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| author | Martin Liska <mliska@suse.cz> | 2022-11-07 13:23:41 +0100 |
|---|---|---|
| committer | Martin Liska <mliska@suse.cz> | 2022-11-09 09:00:35 +0100 |
| commit | 54ca4eef58661a7d7a511e2bbbe309bde1732abf (patch) | |
| tree | 4f9067b036a4e7c08d0d483246cb5ab5a0d60d41 /gcc/doc/tm.texi | |
| parent | 564a805f9f08b4346a854ab8dca2e5b561a7a28e (diff) | |
| download | gcc-54ca4eef58661a7d7a511e2bbbe309bde1732abf.zip gcc-54ca4eef58661a7d7a511e2bbbe309bde1732abf.tar.gz gcc-54ca4eef58661a7d7a511e2bbbe309bde1732abf.tar.bz2 | |
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diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi deleted file mode 100644 index 8572313..0000000 --- a/gcc/doc/tm.texi +++ /dev/null @@ -1,12436 +0,0 @@ -@c Copyright (C) 1988-2022 Free Software Foundation, Inc. -@c This is part of the GCC manual. -@c For copying conditions, see the file gcc.texi. - -@node Target Macros -@chapter Target Description Macros and Functions -@cindex machine description macros -@cindex target description macros -@cindex macros, target description -@cindex @file{tm.h} macros - -In addition to the file @file{@var{machine}.md}, a machine description -includes a C header file conventionally given the name -@file{@var{machine}.h} and a C source file named @file{@var{machine}.c}. -The header file defines numerous macros that convey the information -about the target machine that does not fit into the scheme of the -@file{.md} file. The file @file{tm.h} should be a link to -@file{@var{machine}.h}. The header file @file{config.h} includes -@file{tm.h} and most compiler source files include @file{config.h}. The -source file defines a variable @code{targetm}, which is a structure -containing pointers to functions and data relating to the target -machine. @file{@var{machine}.c} should also contain their definitions, -if they are not defined elsewhere in GCC, and other functions called -through the macros defined in the @file{.h} file. - -@menu -* Target Structure:: The @code{targetm} variable. -* Driver:: Controlling how the driver runs the compilation passes. -* Run-time Target:: Defining @samp{-m} options like @option{-m68000} and @option{-m68020}. -* Per-Function Data:: Defining data structures for per-function information. -* Storage Layout:: Defining sizes and alignments of data. -* Type Layout:: Defining sizes and properties of basic user data types. -* Registers:: Naming and describing the hardware registers. -* Register Classes:: Defining the classes of hardware registers. -* Stack and Calling:: Defining which way the stack grows and by how much. -* Varargs:: Defining the varargs macros. -* Trampolines:: Code set up at run time to enter a nested function. -* Library Calls:: Controlling how library routines are implicitly called. -* Addressing Modes:: Defining addressing modes valid for memory operands. -* Anchored Addresses:: Defining how @option{-fsection-anchors} should work. -* Condition Code:: Defining how insns update the condition code. -* Costs:: Defining relative costs of different operations. -* Scheduling:: Adjusting the behavior of the instruction scheduler. -* Sections:: Dividing storage into text, data, and other sections. -* PIC:: Macros for position independent code. -* Assembler Format:: Defining how to write insns and pseudo-ops to output. -* Debugging Info:: Defining the format of debugging output. -* Floating Point:: Handling floating point for cross-compilers. -* Mode Switching:: Insertion of mode-switching instructions. -* Target Attributes:: Defining target-specific uses of @code{__attribute__}. -* Emulated TLS:: Emulated TLS support. -* MIPS Coprocessors:: MIPS coprocessor support and how to customize it. -* PCH Target:: Validity checking for precompiled headers. -* C++ ABI:: Controlling C++ ABI changes. -* D Language and ABI:: Controlling D ABI changes. -* Named Address Spaces:: Adding support for named address spaces -* Misc:: Everything else. -@end menu - -@node Target Structure -@section The Global @code{targetm} Variable -@cindex target hooks -@cindex target functions - -@deftypevar {struct gcc_target} targetm -The target @file{.c} file must define the global @code{targetm} variable -which contains pointers to functions and data relating to the target -machine. The variable is declared in @file{target.h}; -@file{target-def.h} defines the macro @code{TARGET_INITIALIZER} which is -used to initialize the variable, and macros for the default initializers -for elements of the structure. The @file{.c} file should override those -macros for which the default definition is inappropriate. For example: -@smallexample -#include "target.h" -#include "target-def.h" - -/* @r{Initialize the GCC target structure.} */ - -#undef TARGET_COMP_TYPE_ATTRIBUTES -#define TARGET_COMP_TYPE_ATTRIBUTES @var{machine}_comp_type_attributes - -struct gcc_target targetm = TARGET_INITIALIZER; -@end smallexample -@end deftypevar - -Where a macro should be defined in the @file{.c} file in this manner to -form part of the @code{targetm} structure, it is documented below as a -``Target Hook'' with a prototype. Many macros will change in future -from being defined in the @file{.h} file to being part of the -@code{targetm} structure. - -Similarly, there is a @code{targetcm} variable for hooks that are -specific to front ends for C-family languages, documented as ``C -Target Hook''. This is declared in @file{c-family/c-target.h}, the -initializer @code{TARGETCM_INITIALIZER} in -@file{c-family/c-target-def.h}. If targets initialize @code{targetcm} -themselves, they should set @code{target_has_targetcm=yes} in -@file{config.gcc}; otherwise a default definition is used. - -Similarly, there is a @code{targetm_common} variable for hooks that -are shared between the compiler driver and the compilers proper, -documented as ``Common Target Hook''. This is declared in -@file{common/common-target.h}, the initializer -@code{TARGETM_COMMON_INITIALIZER} in -@file{common/common-target-def.h}. If targets initialize -@code{targetm_common} themselves, they should set -@code{target_has_targetm_common=yes} in @file{config.gcc}; otherwise a -default definition is used. - -Similarly, there is a @code{targetdm} variable for hooks that are -specific to the D language front end, documented as ``D Target Hook''. -This is declared in @file{d/d-target.h}, the initializer -@code{TARGETDM_INITIALIZER} in @file{d/d-target-def.h}. If targets -initialize @code{targetdm} themselves, they should set -@code{target_has_targetdm=yes} in @file{config.gcc}; otherwise a default -definition is used. - -@node Driver -@section Controlling the Compilation Driver, @file{gcc} -@cindex driver -@cindex controlling the compilation driver - -@c prevent bad page break with this line -You can control the compilation driver. - -@defmac DRIVER_SELF_SPECS -A list of specs for the driver itself. It should be a suitable -initializer for an array of strings, with no surrounding braces. - -The driver applies these specs to its own command line between loading -default @file{specs} files (but not command-line specified ones) and -choosing the multilib directory or running any subcommands. It -applies them in the order given, so each spec can depend on the -options added by earlier ones. It is also possible to remove options -using @samp{%<@var{option}} in the usual way. - -This macro can be useful when a port has several interdependent target -options. It provides a way of standardizing the command line so -that the other specs are easier to write. - -Do not define this macro if it does not need to do anything. -@end defmac - -@defmac OPTION_DEFAULT_SPECS -A list of specs used to support configure-time default options (i.e.@: -@option{--with} options) in the driver. It should be a suitable initializer -for an array of structures, each containing two strings, without the -outermost pair of surrounding braces. - -The first item in the pair is the name of the default. This must match -the code in @file{config.gcc} for the target. The second item is a spec -to apply if a default with this name was specified. The string -@samp{%(VALUE)} in the spec will be replaced by the value of the default -everywhere it occurs. - -The driver will apply these specs to its own command line between loading -default @file{specs} files and processing @code{DRIVER_SELF_SPECS}, using -the same mechanism as @code{DRIVER_SELF_SPECS}. - -Do not define this macro if it does not need to do anything. -@end defmac - -@defmac CPP_SPEC -A C string constant that tells the GCC driver program options to -pass to CPP@. It can also specify how to translate options you -give to GCC into options for GCC to pass to the CPP@. - -Do not define this macro if it does not need to do anything. -@end defmac - -@defmac CPLUSPLUS_CPP_SPEC -This macro is just like @code{CPP_SPEC}, but is used for C++, rather -than C@. If you do not define this macro, then the value of -@code{CPP_SPEC} (if any) will be used instead. -@end defmac - -@defmac CC1_SPEC -A C string constant that tells the GCC driver program options to -pass to @code{cc1}, @code{cc1plus}, @code{f771}, and the other language -front ends. -It can also specify how to translate options you give to GCC into options -for GCC to pass to front ends. - -Do not define this macro if it does not need to do anything. -@end defmac - -@defmac CC1PLUS_SPEC -A C string constant that tells the GCC driver program options to -pass to @code{cc1plus}. It can also specify how to translate options you -give to GCC into options for GCC to pass to the @code{cc1plus}. - -Do not define this macro if it does not need to do anything. -Note that everything defined in CC1_SPEC is already passed to -@code{cc1plus} so there is no need to duplicate the contents of -CC1_SPEC in CC1PLUS_SPEC@. -@end defmac - -@defmac ASM_SPEC -A C string constant that tells the GCC driver program options to -pass to the assembler. It can also specify how to translate options -you give to GCC into options for GCC to pass to the assembler. -See the file @file{sun3.h} for an example of this. - -Do not define this macro if it does not need to do anything. -@end defmac - -@defmac ASM_FINAL_SPEC -A C string constant that tells the GCC driver program how to -run any programs which cleanup after the normal assembler. -Normally, this is not needed. See the file @file{mips.h} for -an example of this. - -Do not define this macro if it does not need to do anything. -@end defmac - -@defmac AS_NEEDS_DASH_FOR_PIPED_INPUT -Define this macro, with no value, if the driver should give the assembler -an argument consisting of a single dash, @option{-}, to instruct it to -read from its standard input (which will be a pipe connected to the -output of the compiler proper). This argument is given after any -@option{-o} option specifying the name of the output file. - -If you do not define this macro, the assembler is assumed to read its -standard input if given no non-option arguments. If your assembler -cannot read standard input at all, use a @samp{%@{pipe:%e@}} construct; -see @file{mips.h} for instance. -@end defmac - -@defmac LINK_SPEC -A C string constant that tells the GCC driver program options to -pass to the linker. It can also specify how to translate options you -give to GCC into options for GCC to pass to the linker. - -Do not define this macro if it does not need to do anything. -@end defmac - -@defmac LIB_SPEC -Another C string constant used much like @code{LINK_SPEC}. The difference -between the two is that @code{LIB_SPEC} is used at the end of the -command given to the linker. - -If this macro is not defined, a default is provided that -loads the standard C library from the usual place. See @file{gcc.cc}. -@end defmac - -@defmac LIBGCC_SPEC -Another C string constant that tells the GCC driver program -how and when to place a reference to @file{libgcc.a} into the -linker command line. This constant is placed both before and after -the value of @code{LIB_SPEC}. - -If this macro is not defined, the GCC driver provides a default that -passes the string @option{-lgcc} to the linker. -@end defmac - -@defmac REAL_LIBGCC_SPEC -By default, if @code{ENABLE_SHARED_LIBGCC} is defined, the -@code{LIBGCC_SPEC} is not directly used by the driver program but is -instead modified to refer to different versions of @file{libgcc.a} -depending on the values of the command line flags @option{-static}, -@option{-shared}, @option{-static-libgcc}, and @option{-shared-libgcc}. On -targets where these modifications are inappropriate, define -@code{REAL_LIBGCC_SPEC} instead. @code{REAL_LIBGCC_SPEC} tells the -driver how to place a reference to @file{libgcc} on the link command -line, but, unlike @code{LIBGCC_SPEC}, it is used unmodified. -@end defmac - -@defmac USE_LD_AS_NEEDED -A macro that controls the modifications to @code{LIBGCC_SPEC} -mentioned in @code{REAL_LIBGCC_SPEC}. If nonzero, a spec will be -generated that uses @option{--as-needed} or equivalent options and the -shared @file{libgcc} in place of the -static exception handler library, when linking without any of -@code{-static}, @code{-static-libgcc}, or @code{-shared-libgcc}. -@end defmac - -@defmac LINK_EH_SPEC -If defined, this C string constant is added to @code{LINK_SPEC}. -When @code{USE_LD_AS_NEEDED} is zero or undefined, it also affects -the modifications to @code{LIBGCC_SPEC} mentioned in -@code{REAL_LIBGCC_SPEC}. -@end defmac - -@defmac STARTFILE_SPEC -Another C string constant used much like @code{LINK_SPEC}. The -difference between the two is that @code{STARTFILE_SPEC} is used at -the very beginning of the command given to the linker. - -If this macro is not defined, a default is provided that loads the -standard C startup file from the usual place. See @file{gcc.cc}. -@end defmac - -@defmac ENDFILE_SPEC -Another C string constant used much like @code{LINK_SPEC}. The -difference between the two is that @code{ENDFILE_SPEC} is used at -the very end of the command given to the linker. - -Do not define this macro if it does not need to do anything. -@end defmac - -@defmac THREAD_MODEL_SPEC -GCC @code{-v} will print the thread model GCC was configured to use. -However, this doesn't work on platforms that are multilibbed on thread -models, such as AIX 4.3. On such platforms, define -@code{THREAD_MODEL_SPEC} such that it evaluates to a string without -blanks that names one of the recognized thread models. @code{%*}, the -default value of this macro, will expand to the value of -@code{thread_file} set in @file{config.gcc}. -@end defmac - -@defmac SYSROOT_SUFFIX_SPEC -Define this macro to add a suffix to the target sysroot when GCC is -configured with a sysroot. This will cause GCC to search for usr/lib, -et al, within sysroot+suffix. -@end defmac - -@defmac SYSROOT_HEADERS_SUFFIX_SPEC -Define this macro to add a headers_suffix to the target sysroot when -GCC is configured with a sysroot. This will cause GCC to pass the -updated sysroot+headers_suffix to CPP, causing it to search for -usr/include, et al, within sysroot+headers_suffix. -@end defmac - -@defmac EXTRA_SPECS -Define this macro to provide additional specifications to put in the -@file{specs} file that can be used in various specifications like -@code{CC1_SPEC}. - -The definition should be an initializer for an array of structures, -containing a string constant, that defines the specification name, and a -string constant that provides the specification. - -Do not define this macro if it does not need to do anything. - -@code{EXTRA_SPECS} is useful when an architecture contains several -related targets, which have various @code{@dots{}_SPECS} which are similar -to each other, and the maintainer would like one central place to keep -these definitions. - -For example, the PowerPC System V.4 targets use @code{EXTRA_SPECS} to -define either @code{_CALL_SYSV} when the System V calling sequence is -used or @code{_CALL_AIX} when the older AIX-based calling sequence is -used. - -The @file{config/rs6000/rs6000.h} target file defines: - -@smallexample -#define EXTRA_SPECS \ - @{ "cpp_sysv_default", CPP_SYSV_DEFAULT @}, - -#define CPP_SYS_DEFAULT "" -@end smallexample - -The @file{config/rs6000/sysv.h} target file defines: -@smallexample -#undef CPP_SPEC -#define CPP_SPEC \ -"%@{posix: -D_POSIX_SOURCE @} \ -%@{mcall-sysv: -D_CALL_SYSV @} \ -%@{!mcall-sysv: %(cpp_sysv_default) @} \ -%@{msoft-float: -D_SOFT_FLOAT@} %@{mcpu=403: -D_SOFT_FLOAT@}" - -#undef CPP_SYSV_DEFAULT -#define CPP_SYSV_DEFAULT "-D_CALL_SYSV" -@end smallexample - -while the @file{config/rs6000/eabiaix.h} target file defines -@code{CPP_SYSV_DEFAULT} as: - -@smallexample -#undef CPP_SYSV_DEFAULT -#define CPP_SYSV_DEFAULT "-D_CALL_AIX" -@end smallexample -@end defmac - -@defmac LINK_LIBGCC_SPECIAL_1 -Define this macro if the driver program should find the library -@file{libgcc.a}. If you do not define this macro, the driver program will pass -the argument @option{-lgcc} to tell the linker to do the search. -@end defmac - -@defmac LINK_GCC_C_SEQUENCE_SPEC -The sequence in which libgcc and libc are specified to the linker. -By default this is @code{%G %L %G}. -@end defmac - -@defmac POST_LINK_SPEC -Define this macro to add additional steps to be executed after linker. -The default value of this macro is empty string. -@end defmac - -@defmac LINK_COMMAND_SPEC -A C string constant giving the complete command line need to execute the -linker. When you do this, you will need to update your port each time a -change is made to the link command line within @file{gcc.cc}. Therefore, -define this macro only if you need to completely redefine the command -line for invoking the linker and there is no other way to accomplish -the effect you need. Overriding this macro may be avoidable by overriding -@code{LINK_GCC_C_SEQUENCE_SPEC} instead. -@end defmac - -@deftypevr {Common Target Hook} bool TARGET_ALWAYS_STRIP_DOTDOT -True if @file{..} components should always be removed from directory names -computed relative to GCC's internal directories, false (default) if such -components should be preserved and directory names containing them passed -to other tools such as the linker. -@end deftypevr - -@defmac MULTILIB_DEFAULTS -Define this macro as a C expression for the initializer of an array of -string to tell the driver program which options are defaults for this -target and thus do not need to be handled specially when using -@code{MULTILIB_OPTIONS}. - -Do not define this macro if @code{MULTILIB_OPTIONS} is not defined in -the target makefile fragment or if none of the options listed in -@code{MULTILIB_OPTIONS} are set by default. -@xref{Target Fragment}. -@end defmac - -@defmac RELATIVE_PREFIX_NOT_LINKDIR -Define this macro to tell @command{gcc} that it should only translate -a @option{-B} prefix into a @option{-L} linker option if the prefix -indicates an absolute file name. -@end defmac - -@defmac MD_EXEC_PREFIX -If defined, this macro is an additional prefix to try after -@code{STANDARD_EXEC_PREFIX}. @code{MD_EXEC_PREFIX} is not searched -when the compiler is built as a cross -compiler. If you define @code{MD_EXEC_PREFIX}, then be sure to add it -to the list of directories used to find the assembler in @file{configure.ac}. -@end defmac - -@defmac STANDARD_STARTFILE_PREFIX -Define this macro as a C string constant if you wish to override the -standard choice of @code{libdir} as the default prefix to -try when searching for startup files such as @file{crt0.o}. -@code{STANDARD_STARTFILE_PREFIX} is not searched when the compiler -is built as a cross compiler. -@end defmac - -@defmac STANDARD_STARTFILE_PREFIX_1 -Define this macro as a C string constant if you wish to override the -standard choice of @code{/lib} as a prefix to try after the default prefix -when searching for startup files such as @file{crt0.o}. -@code{STANDARD_STARTFILE_PREFIX_1} is not searched when the compiler -is built as a cross compiler. -@end defmac - -@defmac STANDARD_STARTFILE_PREFIX_2 -Define this macro as a C string constant if you wish to override the -standard choice of @code{/lib} as yet another prefix to try after the -default prefix when searching for startup files such as @file{crt0.o}. -@code{STANDARD_STARTFILE_PREFIX_2} is not searched when the compiler -is built as a cross compiler. -@end defmac - -@defmac MD_STARTFILE_PREFIX -If defined, this macro supplies an additional prefix to try after the -standard prefixes. @code{MD_EXEC_PREFIX} is not searched when the -compiler is built as a cross compiler. -@end defmac - -@defmac MD_STARTFILE_PREFIX_1 -If defined, this macro supplies yet another prefix to try after the -standard prefixes. It is not searched when the compiler is built as a -cross compiler. -@end defmac - -@defmac INIT_ENVIRONMENT -Define this macro as a C string constant if you wish to set environment -variables for programs called by the driver, such as the assembler and -loader. The driver passes the value of this macro to @code{putenv} to -initialize the necessary environment variables. -@end defmac - -@defmac LOCAL_INCLUDE_DIR -Define this macro as a C string constant if you wish to override the -standard choice of @file{/usr/local/include} as the default prefix to -try when searching for local header files. @code{LOCAL_INCLUDE_DIR} -comes before @code{NATIVE_SYSTEM_HEADER_DIR} (set in -@file{config.gcc}, normally @file{/usr/include}) in the search order. - -Cross compilers do not search either @file{/usr/local/include} or its -replacement. -@end defmac - -@defmac NATIVE_SYSTEM_HEADER_COMPONENT -The ``component'' corresponding to @code{NATIVE_SYSTEM_HEADER_DIR}. -See @code{INCLUDE_DEFAULTS}, below, for the description of components. -If you do not define this macro, no component is used. -@end defmac - -@defmac INCLUDE_DEFAULTS -Define this macro if you wish to override the entire default search path -for include files. For a native compiler, the default search path -usually consists of @code{GCC_INCLUDE_DIR}, @code{LOCAL_INCLUDE_DIR}, -@code{GPLUSPLUS_INCLUDE_DIR}, and -@code{NATIVE_SYSTEM_HEADER_DIR}. In addition, @code{GPLUSPLUS_INCLUDE_DIR} -and @code{GCC_INCLUDE_DIR} are defined automatically by @file{Makefile}, -and specify private search areas for GCC@. The directory -@code{GPLUSPLUS_INCLUDE_DIR} is used only for C++ programs. - -The definition should be an initializer for an array of structures. -Each array element should have four elements: the directory name (a -string constant), the component name (also a string constant), a flag -for C++-only directories, -and a flag showing that the includes in the directory don't need to be -wrapped in @code{extern @samp{C}} when compiling C++. Mark the end of -the array with a null element. - -The component name denotes what GNU package the include file is part of, -if any, in all uppercase letters. For example, it might be @samp{GCC} -or @samp{BINUTILS}. If the package is part of a vendor-supplied -operating system, code the component name as @samp{0}. - -For example, here is the definition used for VAX/VMS: - -@smallexample -#define INCLUDE_DEFAULTS \ -@{ \ - @{ "GNU_GXX_INCLUDE:", "G++", 1, 1@}, \ - @{ "GNU_CC_INCLUDE:", "GCC", 0, 0@}, \ - @{ "SYS$SYSROOT:[SYSLIB.]", 0, 0, 0@}, \ - @{ ".", 0, 0, 0@}, \ - @{ 0, 0, 0, 0@} \ -@} -@end smallexample -@end defmac - -Here is the order of prefixes tried for exec files: - -@enumerate -@item -Any prefixes specified by the user with @option{-B}. - -@item -The environment variable @code{GCC_EXEC_PREFIX} or, if @code{GCC_EXEC_PREFIX} -is not set and the compiler has not been installed in the configure-time -@var{prefix}, the location in which the compiler has actually been installed. - -@item -The directories specified by the environment variable @code{COMPILER_PATH}. - -@item -The macro @code{STANDARD_EXEC_PREFIX}, if the compiler has been installed -in the configured-time @var{prefix}. - -@item -The location @file{/usr/libexec/gcc/}, but only if this is a native compiler. - -@item -The location @file{/usr/lib/gcc/}, but only if this is a native compiler. - -@item -The macro @code{MD_EXEC_PREFIX}, if defined, but only if this is a native -compiler. -@end enumerate - -Here is the order of prefixes tried for startfiles: - -@enumerate -@item -Any prefixes specified by the user with @option{-B}. - -@item -The environment variable @code{GCC_EXEC_PREFIX} or its automatically determined -value based on the installed toolchain location. - -@item -The directories specified by the environment variable @code{LIBRARY_PATH} -(or port-specific name; native only, cross compilers do not use this). - -@item -The macro @code{STANDARD_EXEC_PREFIX}, but only if the toolchain is installed -in the configured @var{prefix} or this is a native compiler. - -@item -The location @file{/usr/lib/gcc/}, but only if this is a native compiler. - -@item -The macro @code{MD_EXEC_PREFIX}, if defined, but only if this is a native -compiler. - -@item -The macro @code{MD_STARTFILE_PREFIX}, if defined, but only if this is a -native compiler, or we have a target system root. - -@item -The macro @code{MD_STARTFILE_PREFIX_1}, if defined, but only if this is a -native compiler, or we have a target system root. - -@item -The macro @code{STANDARD_STARTFILE_PREFIX}, with any sysroot modifications. -If this path is relative it will be prefixed by @code{GCC_EXEC_PREFIX} and -the machine suffix or @code{STANDARD_EXEC_PREFIX} and the machine suffix. - -@item -The macro @code{STANDARD_STARTFILE_PREFIX_1}, but only if this is a native -compiler, or we have a target system root. The default for this macro is -@file{/lib/}. - -@item -The macro @code{STANDARD_STARTFILE_PREFIX_2}, but only if this is a native -compiler, or we have a target system root. The default for this macro is -@file{/usr/lib/}. -@end enumerate - -@node Run-time Target -@section Run-time Target Specification -@cindex run-time target specification -@cindex predefined macros -@cindex target specifications - -@c prevent bad page break with this line -Here are run-time target specifications. - -@defmac TARGET_CPU_CPP_BUILTINS () -This function-like macro expands to a block of code that defines -built-in preprocessor macros and assertions for the target CPU, using -the functions @code{builtin_define}, @code{builtin_define_std} and -@code{builtin_assert}. When the front end -calls this macro it provides a trailing semicolon, and since it has -finished command line option processing your code can use those -results freely. - -@code{builtin_assert} takes a string in the form you pass to the -command-line option @option{-A}, such as @code{cpu=mips}, and creates -the assertion. @code{builtin_define} takes a string in the form -accepted by option @option{-D} and unconditionally defines the macro. - -@code{builtin_define_std} takes a string representing the name of an -object-like macro. If it doesn't lie in the user's namespace, -@code{builtin_define_std} defines it unconditionally. Otherwise, it -defines a version with two leading underscores, and another version -with two leading and trailing underscores, and defines the original -only if an ISO standard was not requested on the command line. For -example, passing @code{unix} defines @code{__unix}, @code{__unix__} -and possibly @code{unix}; passing @code{_mips} defines @code{__mips}, -@code{__mips__} and possibly @code{_mips}, and passing @code{_ABI64} -defines only @code{_ABI64}. - -You can also test for the C dialect being compiled. The variable -@code{c_language} is set to one of @code{clk_c}, @code{clk_cplusplus} -or @code{clk_objective_c}. Note that if we are preprocessing -assembler, this variable will be @code{clk_c} but the function-like -macro @code{preprocessing_asm_p()} will return true, so you might want -to check for that first. If you need to check for strict ANSI, the -variable @code{flag_iso} can be used. The function-like macro -@code{preprocessing_trad_p()} can be used to check for traditional -preprocessing. -@end defmac - -@defmac TARGET_OS_CPP_BUILTINS () -Similarly to @code{TARGET_CPU_CPP_BUILTINS} but this macro is optional -and is used for the target operating system instead. -@end defmac - -@defmac TARGET_OBJFMT_CPP_BUILTINS () -Similarly to @code{TARGET_CPU_CPP_BUILTINS} but this macro is optional -and is used for the target object format. @file{elfos.h} uses this -macro to define @code{__ELF__}, so you probably do not need to define -it yourself. -@end defmac - -@deftypevar {extern int} target_flags -This variable is declared in @file{options.h}, which is included before -any target-specific headers. -@end deftypevar - -@deftypevr {Common Target Hook} int TARGET_DEFAULT_TARGET_FLAGS -This variable specifies the initial value of @code{target_flags}. -Its default setting is 0. -@end deftypevr - -@cindex optional hardware or system features -@cindex features, optional, in system conventions - -@deftypefn {Common Target Hook} bool TARGET_HANDLE_OPTION (struct gcc_options *@var{opts}, struct gcc_options *@var{opts_set}, const struct cl_decoded_option *@var{decoded}, location_t @var{loc}) -This hook is called whenever the user specifies one of the -target-specific options described by the @file{.opt} definition files -(@pxref{Options}). It has the opportunity to do some option-specific -processing and should return true if the option is valid. The default -definition does nothing but return true. - -@var{decoded} specifies the option and its arguments. @var{opts} and -@var{opts_set} are the @code{gcc_options} structures to be used for -storing option state, and @var{loc} is the location at which the -option was passed (@code{UNKNOWN_LOCATION} except for options passed -via attributes). -@end deftypefn - -@deftypefn {C Target Hook} bool TARGET_HANDLE_C_OPTION (size_t @var{code}, const char *@var{arg}, int @var{value}) -This target hook is called whenever the user specifies one of the -target-specific C language family options described by the @file{.opt} -definition files(@pxref{Options}). It has the opportunity to do some -option-specific processing and should return true if the option is -valid. The arguments are like for @code{TARGET_HANDLE_OPTION}. The -default definition does nothing but return false. - -In general, you should use @code{TARGET_HANDLE_OPTION} to handle -options. However, if processing an option requires routines that are -only available in the C (and related language) front ends, then you -should use @code{TARGET_HANDLE_C_OPTION} instead. -@end deftypefn - -@deftypefn {C Target Hook} tree TARGET_OBJC_CONSTRUCT_STRING_OBJECT (tree @var{string}) -Targets may provide a string object type that can be used within -and between C, C++ and their respective Objective-C dialects. -A string object might, for example, embed encoding and length information. -These objects are considered opaque to the compiler and handled as references. -An ideal implementation makes the composition of the string object -match that of the Objective-C @code{NSString} (@code{NXString} for GNUStep), -allowing efficient interworking between C-only and Objective-C code. -If a target implements string objects then this hook should return a -reference to such an object constructed from the normal `C' string -representation provided in @var{string}. -At present, the hook is used by Objective-C only, to obtain a - common-format string object when the target provides one. -@end deftypefn - -@deftypefn {C Target Hook} void TARGET_OBJC_DECLARE_UNRESOLVED_CLASS_REFERENCE (const char *@var{classname}) -Declare that Objective C class @var{classname} is referenced -by the current TU. -@end deftypefn - -@deftypefn {C Target Hook} void TARGET_OBJC_DECLARE_CLASS_DEFINITION (const char *@var{classname}) -Declare that Objective C class @var{classname} is defined -by the current TU. -@end deftypefn - -@deftypefn {C Target Hook} bool TARGET_STRING_OBJECT_REF_TYPE_P (const_tree @var{stringref}) -If a target implements string objects then this hook should return -@code{true} if @var{stringref} is a valid reference to such an object. -@end deftypefn - -@deftypefn {C Target Hook} void TARGET_CHECK_STRING_OBJECT_FORMAT_ARG (tree @var{format_arg}, tree @var{args_list}) -If a target implements string objects then this hook should -provide a facility to check the function arguments in @var{args_list} -against the format specifiers in @var{format_arg} where the type of -@var{format_arg} is one recognized as a valid string reference type. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE (void) -This target function is similar to the hook @code{TARGET_OPTION_OVERRIDE} -but is called when the optimize level is changed via an attribute or -pragma or when it is reset at the end of the code affected by the -attribute or pragma. It is not called at the beginning of compilation -when @code{TARGET_OPTION_OVERRIDE} is called so if you want to perform these -actions then, you should have @code{TARGET_OPTION_OVERRIDE} call -@code{TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE}. -@end deftypefn - -@defmac C_COMMON_OVERRIDE_OPTIONS -This is similar to the @code{TARGET_OPTION_OVERRIDE} hook -but is only used in the C -language frontends (C, Objective-C, C++, Objective-C++) and so can be -used to alter option flag variables which only exist in those -frontends. -@end defmac - -@deftypevr {Common Target Hook} {const struct default_options *} TARGET_OPTION_OPTIMIZATION_TABLE -Some machines may desire to change what optimizations are performed for -various optimization levels. This variable, if defined, describes -options to enable at particular sets of optimization levels. These -options are processed once -just after the optimization level is determined and before the remainder -of the command options have been parsed, so may be overridden by other -options passed explicitly. - -This processing is run once at program startup and when the optimization -options are changed via @code{#pragma GCC optimize} or by using the -@code{optimize} attribute. -@end deftypevr - -@deftypefn {Common Target Hook} void TARGET_OPTION_INIT_STRUCT (struct gcc_options *@var{opts}) -Set target-dependent initial values of fields in @var{opts}. -@end deftypefn - -@deftypefn {Common Target Hook} {const char *} TARGET_COMPUTE_MULTILIB (const struct switchstr *@var{switches}, int @var{n_switches}, const char *@var{multilib_dir}, const char *@var{multilib_defaults}, const char *@var{multilib_select}, const char *@var{multilib_matches}, const char *@var{multilib_exclusions}, const char *@var{multilib_reuse}) -Some targets like RISC-V might have complicated multilib reuse rules which -are hard to implement with the current multilib scheme. This hook allows -targets to override the result from the built-in multilib mechanism. -@var{switches} is the raw option list with @var{n_switches} items; -@var{multilib_dir} is the multi-lib result which is computed by the built-in -multi-lib mechanism; -@var{multilib_defaults} is the default options list for multi-lib; -@var{multilib_select} is the string containing the list of supported -multi-libs, and the option checking list. -@var{multilib_matches}, @var{multilib_exclusions}, and @var{multilib_reuse} -are corresponding to @var{MULTILIB_MATCHES}, @var{MULTILIB_EXCLUSIONS}, -and @var{MULTILIB_REUSE}. -The default definition does nothing but return @var{multilib_dir} directly. -@end deftypefn - - -@defmac SWITCHABLE_TARGET -Some targets need to switch between substantially different subtargets -during compilation. For example, the MIPS target has one subtarget for -the traditional MIPS architecture and another for MIPS16. Source code -can switch between these two subarchitectures using the @code{mips16} -and @code{nomips16} attributes. - -Such subtargets can differ in things like the set of available -registers, the set of available instructions, the costs of various -operations, and so on. GCC caches a lot of this type of information -in global variables, and recomputing them for each subtarget takes a -significant amount of time. The compiler therefore provides a facility -for maintaining several versions of the global variables and quickly -switching between them; see @file{target-globals.h} for details. - -Define this macro to 1 if your target needs this facility. The default -is 0. -@end defmac - -@deftypefn {Target Hook} bool TARGET_FLOAT_EXCEPTIONS_ROUNDING_SUPPORTED_P (void) -Returns true if the target supports IEEE 754 floating-point exceptions -and rounding modes, false otherwise. This is intended to relate to the -@code{float} and @code{double} types, but not necessarily @code{long double}. -By default, returns true if the @code{adddf3} instruction pattern is -available and false otherwise, on the assumption that hardware floating -point supports exceptions and rounding modes but software floating point -does not. -@end deftypefn - -@node Per-Function Data -@section Defining data structures for per-function information. -@cindex per-function data -@cindex data structures - -If the target needs to store information on a per-function basis, GCC -provides a macro and a couple of variables to allow this. Note, just -using statics to store the information is a bad idea, since GCC supports -nested functions, so you can be halfway through encoding one function -when another one comes along. - -GCC defines a data structure called @code{struct function} which -contains all of the data specific to an individual function. This -structure contains a field called @code{machine} whose type is -@code{struct machine_function *}, which can be used by targets to point -to their own specific data. - -If a target needs per-function specific data it should define the type -@code{struct machine_function} and also the macro @code{INIT_EXPANDERS}. -This macro should be used to initialize the function pointer -@code{init_machine_status}. This pointer is explained below. - -One typical use of per-function, target specific data is to create an -RTX to hold the register containing the function's return address. This -RTX can then be used to implement the @code{__builtin_return_address} -function, for level 0. - -Note---earlier implementations of GCC used a single data area to hold -all of the per-function information. Thus when processing of a nested -function began the old per-function data had to be pushed onto a -stack, and when the processing was finished, it had to be popped off the -stack. GCC used to provide function pointers called -@code{save_machine_status} and @code{restore_machine_status} to handle -the saving and restoring of the target specific information. Since the -single data area approach is no longer used, these pointers are no -longer supported. - -@defmac INIT_EXPANDERS -Macro called to initialize any target specific information. This macro -is called once per function, before generation of any RTL has begun. -The intention of this macro is to allow the initialization of the -function pointer @code{init_machine_status}. -@end defmac - -@deftypevar {void (*)(struct function *)} init_machine_status -If this function pointer is non-@code{NULL} it will be called once per -function, before function compilation starts, in order to allow the -target to perform any target specific initialization of the -@code{struct function} structure. It is intended that this would be -used to initialize the @code{machine} of that structure. - -@code{struct machine_function} structures are expected to be freed by GC@. -Generally, any memory that they reference must be allocated by using -GC allocation, including the structure itself. -@end deftypevar - -@node Storage Layout -@section Storage Layout -@cindex storage layout - -Note that the definitions of the macros in this table which are sizes or -alignments measured in bits do not need to be constant. They can be C -expressions that refer to static variables, such as the @code{target_flags}. -@xref{Run-time Target}. - -@defmac BITS_BIG_ENDIAN -Define this macro to have the value 1 if the most significant bit in a -byte has the lowest number; otherwise define it to have the value zero. -This means that bit-field instructions count from the most significant -bit. If the machine has no bit-field instructions, then this must still -be defined, but it doesn't matter which value it is defined to. This -macro need not be a constant. - -This macro does not affect the way structure fields are packed into -bytes or words; that is controlled by @code{BYTES_BIG_ENDIAN}. -@end defmac - -@defmac BYTES_BIG_ENDIAN -Define this macro to have the value 1 if the most significant byte in a -word has the lowest number. This macro need not be a constant. -@end defmac - -@defmac WORDS_BIG_ENDIAN -Define this macro to have the value 1 if, in a multiword object, the -most significant word has the lowest number. This applies to both -memory locations and registers; see @code{REG_WORDS_BIG_ENDIAN} if the -order of words in memory is not the same as the order in registers. This -macro need not be a constant. -@end defmac - -@defmac REG_WORDS_BIG_ENDIAN -On some machines, the order of words in a multiword object differs between -registers in memory. In such a situation, define this macro to describe -the order of words in a register. The macro @code{WORDS_BIG_ENDIAN} controls -the order of words in memory. -@end defmac - -@defmac FLOAT_WORDS_BIG_ENDIAN -Define this macro to have the value 1 if @code{DFmode}, @code{XFmode} or -@code{TFmode} floating point numbers are stored in memory with the word -containing the sign bit at the lowest address; otherwise define it to -have the value 0. This macro need not be a constant. - -You need not define this macro if the ordering is the same as for -multi-word integers. -@end defmac - -@defmac BITS_PER_WORD -Number of bits in a word. If you do not define this macro, the default -is @code{BITS_PER_UNIT * UNITS_PER_WORD}. -@end defmac - -@defmac MAX_BITS_PER_WORD -Maximum number of bits in a word. If this is undefined, the default is -@code{BITS_PER_WORD}. Otherwise, it is the constant value that is the -largest value that @code{BITS_PER_WORD} can have at run-time. -@end defmac - -@defmac UNITS_PER_WORD -Number of storage units in a word; normally the size of a general-purpose -register, a power of two from 1 or 8. -@end defmac - -@defmac MIN_UNITS_PER_WORD -Minimum number of units in a word. If this is undefined, the default is -@code{UNITS_PER_WORD}. Otherwise, it is the constant value that is the -smallest value that @code{UNITS_PER_WORD} can have at run-time. -@end defmac - -@defmac POINTER_SIZE -Width of a pointer, in bits. You must specify a value no wider than the -width of @code{Pmode}. If it is not equal to the width of @code{Pmode}, -you must define @code{POINTERS_EXTEND_UNSIGNED}. If you do not specify -a value the default is @code{BITS_PER_WORD}. -@end defmac - -@defmac POINTERS_EXTEND_UNSIGNED -A C expression that determines how pointers should be extended from -@code{ptr_mode} to either @code{Pmode} or @code{word_mode}. It is -greater than zero if pointers should be zero-extended, zero if they -should be sign-extended, and negative if some other sort of conversion -is needed. In the last case, the extension is done by the target's -@code{ptr_extend} instruction. - -You need not define this macro if the @code{ptr_mode}, @code{Pmode} -and @code{word_mode} are all the same width. -@end defmac - -@defmac PROMOTE_MODE (@var{m}, @var{unsignedp}, @var{type}) -A macro to update @var{m} and @var{unsignedp} when an object whose type -is @var{type} and which has the specified mode and signedness is to be -stored in a register. This macro is only called when @var{type} is a -scalar type. - -On most RISC machines, which only have operations that operate on a full -register, define this macro to set @var{m} to @code{word_mode} if -@var{m} is an integer mode narrower than @code{BITS_PER_WORD}. In most -cases, only integer modes should be widened because wider-precision -floating-point operations are usually more expensive than their narrower -counterparts. - -For most machines, the macro definition does not change @var{unsignedp}. -However, some machines, have instructions that preferentially handle -either signed or unsigned quantities of certain modes. For example, on -the DEC Alpha, 32-bit loads from memory and 32-bit add instructions -sign-extend the result to 64 bits. On such machines, set -@var{unsignedp} according to which kind of extension is more efficient. - -Do not define this macro if it would never modify @var{m}. -@end defmac - -@deftypefn {Target Hook} {enum flt_eval_method} TARGET_C_EXCESS_PRECISION (enum excess_precision_type @var{type}) -Return a value, with the same meaning as the C99 macro -@code{FLT_EVAL_METHOD} that describes which excess precision should be -applied. @var{type} is either @code{EXCESS_PRECISION_TYPE_IMPLICIT}, -@code{EXCESS_PRECISION_TYPE_FAST}, -@code{EXCESS_PRECISION_TYPE_STANDARD}, or -@code{EXCESS_PRECISION_TYPE_FLOAT16}. For -@code{EXCESS_PRECISION_TYPE_IMPLICIT}, the target should return which -precision and range operations will be implictly evaluated in regardless -of the excess precision explicitly added. For -@code{EXCESS_PRECISION_TYPE_STANDARD}, -@code{EXCESS_PRECISION_TYPE_FLOAT16}, and -@code{EXCESS_PRECISION_TYPE_FAST}, the target should return the -explicit excess precision that should be added depending on the -value set for @option{-fexcess-precision=@r{[}standard@r{|}fast@r{|}16@r{]}}. -Note that unpredictable explicit excess precision does not make sense, -so a target should never return @code{FLT_EVAL_METHOD_UNPREDICTABLE} -when @var{type} is @code{EXCESS_PRECISION_TYPE_STANDARD}, -@code{EXCESS_PRECISION_TYPE_FLOAT16} or -@code{EXCESS_PRECISION_TYPE_FAST}. -@end deftypefn -Return a value, with the same meaning as the C99 macro -@code{FLT_EVAL_METHOD} that describes which excess precision should be -applied. - -@deftypefn {Target Hook} machine_mode TARGET_PROMOTE_FUNCTION_MODE (const_tree @var{type}, machine_mode @var{mode}, int *@var{punsignedp}, const_tree @var{funtype}, int @var{for_return}) -Like @code{PROMOTE_MODE}, but it is applied to outgoing function arguments or -function return values. The target hook should return the new mode -and possibly change @code{*@var{punsignedp}} if the promotion should -change signedness. This function is called only for scalar @emph{or -pointer} types. - -@var{for_return} allows to distinguish the promotion of arguments and -return values. If it is @code{1}, a return value is being promoted and -@code{TARGET_FUNCTION_VALUE} must perform the same promotions done here. -If it is @code{2}, the returned mode should be that of the register in -which an incoming parameter is copied, or the outgoing result is computed; -then the hook should return the same mode as @code{promote_mode}, though -the signedness may be different. - -@var{type} can be NULL when promoting function arguments of libcalls. - -The default is to not promote arguments and return values. You can -also define the hook to @code{default_promote_function_mode_always_promote} -if you would like to apply the same rules given by @code{PROMOTE_MODE}. -@end deftypefn - -@defmac PARM_BOUNDARY -Normal alignment required for function parameters on the stack, in -bits. All stack parameters receive at least this much alignment -regardless of data type. On most machines, this is the same as the -size of an integer. -@end defmac - -@defmac STACK_BOUNDARY -Define this macro to the minimum alignment enforced by hardware for the -stack pointer on this machine. The definition is a C expression for the -desired alignment (measured in bits). This value is used as a default -if @code{PREFERRED_STACK_BOUNDARY} is not defined. On most machines, -this should be the same as @code{PARM_BOUNDARY}. -@end defmac - -@defmac PREFERRED_STACK_BOUNDARY -Define this macro if you wish to preserve a certain alignment for the -stack pointer, greater than what the hardware enforces. The definition -is a C expression for the desired alignment (measured in bits). This -macro must evaluate to a value equal to or larger than -@code{STACK_BOUNDARY}. -@end defmac - -@defmac INCOMING_STACK_BOUNDARY -Define this macro if the incoming stack boundary may be different -from @code{PREFERRED_STACK_BOUNDARY}. This macro must evaluate -to a value equal to or larger than @code{STACK_BOUNDARY}. -@end defmac - -@defmac FUNCTION_BOUNDARY -Alignment required for a function entry point, in bits. -@end defmac - -@defmac BIGGEST_ALIGNMENT -Biggest alignment that any data type can require on this machine, in -bits. Note that this is not the biggest alignment that is supported, -just the biggest alignment that, when violated, may cause a fault. -@end defmac - -@deftypevr {Target Hook} HOST_WIDE_INT TARGET_ABSOLUTE_BIGGEST_ALIGNMENT -If defined, this target hook specifies the absolute biggest alignment -that a type or variable can have on this machine, otherwise, -@code{BIGGEST_ALIGNMENT} is used. -@end deftypevr - -@defmac MALLOC_ABI_ALIGNMENT -Alignment, in bits, a C conformant malloc implementation has to -provide. If not defined, the default value is @code{BITS_PER_WORD}. -@end defmac - -@defmac ATTRIBUTE_ALIGNED_VALUE -Alignment used by the @code{__attribute__ ((aligned))} construct. If -not defined, the default value is @code{BIGGEST_ALIGNMENT}. -@end defmac - -@defmac MINIMUM_ATOMIC_ALIGNMENT -If defined, the smallest alignment, in bits, that can be given to an -object that can be referenced in one operation, without disturbing any -nearby object. Normally, this is @code{BITS_PER_UNIT}, but may be larger -on machines that don't have byte or half-word store operations. -@end defmac - -@defmac BIGGEST_FIELD_ALIGNMENT -Biggest alignment that any structure or union field can require on this -machine, in bits. If defined, this overrides @code{BIGGEST_ALIGNMENT} for -structure and union fields only, unless the field alignment has been set -by the @code{__attribute__ ((aligned (@var{n})))} construct. -@end defmac - -@defmac ADJUST_FIELD_ALIGN (@var{field}, @var{type}, @var{computed}) -An expression for the alignment of a structure field @var{field} of -type @var{type} if the alignment computed in the usual way (including -applying of @code{BIGGEST_ALIGNMENT} and @code{BIGGEST_FIELD_ALIGNMENT} to the -alignment) is @var{computed}. It overrides alignment only if the -field alignment has not been set by the -@code{__attribute__ ((aligned (@var{n})))} construct. Note that @var{field} -may be @code{NULL_TREE} in case we just query for the minimum alignment -of a field of type @var{type} in structure context. -@end defmac - -@defmac MAX_STACK_ALIGNMENT -Biggest stack alignment guaranteed by the backend. Use this macro -to specify the maximum alignment of a variable on stack. - -If not defined, the default value is @code{STACK_BOUNDARY}. - -@c FIXME: The default should be @code{PREFERRED_STACK_BOUNDARY}. -@c But the fix for PR 32893 indicates that we can only guarantee -@c maximum stack alignment on stack up to @code{STACK_BOUNDARY}, not -@c @code{PREFERRED_STACK_BOUNDARY}, if stack alignment isn't supported. -@end defmac - -@defmac MAX_OFILE_ALIGNMENT -Biggest alignment supported by the object file format of this machine. -Use this macro to limit the alignment which can be specified using the -@code{__attribute__ ((aligned (@var{n})))} construct for functions and -objects with static storage duration. The alignment of automatic -objects may exceed the object file format maximum up to the maximum -supported by GCC. If not defined, the default value is -@code{BIGGEST_ALIGNMENT}. - -On systems that use ELF, the default (in @file{config/elfos.h}) is -the largest supported 32-bit ELF section alignment representable on -a 32-bit host e.g.@: @samp{(((uint64_t) 1 << 28) * 8)}. -On 32-bit ELF the largest supported section alignment in bits is -@samp{(0x80000000 * 8)}, but this is not representable on 32-bit hosts. -@end defmac - -@deftypefn {Target Hook} void TARGET_LOWER_LOCAL_DECL_ALIGNMENT (tree @var{decl}) -Define this hook to lower alignment of local, parm or result -decl @samp{(@var{decl})}. -@end deftypefn - -@deftypefn {Target Hook} HOST_WIDE_INT TARGET_STATIC_RTX_ALIGNMENT (machine_mode @var{mode}) -This hook returns the preferred alignment in bits for a -statically-allocated rtx, such as a constant pool entry. @var{mode} -is the mode of the rtx. The default implementation returns -@samp{GET_MODE_ALIGNMENT (@var{mode})}. -@end deftypefn - -@defmac DATA_ALIGNMENT (@var{type}, @var{basic-align}) -If defined, a C expression to compute the alignment for a variable in -the static store. @var{type} is the data type, and @var{basic-align} is -the alignment that the object would ordinarily have. The value of this -macro is used instead of that alignment to align the object. - -If this macro is not defined, then @var{basic-align} is used. - -@findex strcpy -One use of this macro is to increase alignment of medium-size data to -make it all fit in fewer cache lines. Another is to cause character -arrays to be word-aligned so that @code{strcpy} calls that copy -constants to character arrays can be done inline. -@end defmac - -@defmac DATA_ABI_ALIGNMENT (@var{type}, @var{basic-align}) -Similar to @code{DATA_ALIGNMENT}, but for the cases where the ABI mandates -some alignment increase, instead of optimization only purposes. E.g.@ -AMD x86-64 psABI says that variables with array type larger than 15 bytes -must be aligned to 16 byte boundaries. - -If this macro is not defined, then @var{basic-align} is used. -@end defmac - -@deftypefn {Target Hook} HOST_WIDE_INT TARGET_CONSTANT_ALIGNMENT (const_tree @var{constant}, HOST_WIDE_INT @var{basic_align}) -This hook returns the alignment in bits of a constant that is being -placed in memory. @var{constant} is the constant and @var{basic_align} -is the alignment that the object would ordinarily have. - -The default definition just returns @var{basic_align}. - -The typical use of this hook is to increase alignment for string -constants to be word aligned so that @code{strcpy} calls that copy -constants can be done inline. The function -@code{constant_alignment_word_strings} provides such a definition. -@end deftypefn - -@defmac LOCAL_ALIGNMENT (@var{type}, @var{basic-align}) -If defined, a C expression to compute the alignment for a variable in -the local store. @var{type} is the data type, and @var{basic-align} is -the alignment that the object would ordinarily have. The value of this -macro is used instead of that alignment to align the object. - -If this macro is not defined, then @var{basic-align} is used. - -One use of this macro is to increase alignment of medium-size data to -make it all fit in fewer cache lines. - -If the value of this macro has a type, it should be an unsigned type. -@end defmac - -@deftypefn {Target Hook} HOST_WIDE_INT TARGET_VECTOR_ALIGNMENT (const_tree @var{type}) -This hook can be used to define the alignment for a vector of type -@var{type}, in order to comply with a platform ABI. The default is to -require natural alignment for vector types. The alignment returned by -this hook must be a power-of-two multiple of the default alignment of -the vector element type. -@end deftypefn - -@defmac STACK_SLOT_ALIGNMENT (@var{type}, @var{mode}, @var{basic-align}) -If defined, a C expression to compute the alignment for stack slot. -@var{type} is the data type, @var{mode} is the widest mode available, -and @var{basic-align} is the alignment that the slot would ordinarily -have. The value of this macro is used instead of that alignment to -align the slot. - -If this macro is not defined, then @var{basic-align} is used when -@var{type} is @code{NULL}. Otherwise, @code{LOCAL_ALIGNMENT} will -be used. - -This macro is to set alignment of stack slot to the maximum alignment -of all possible modes which the slot may have. - -If the value of this macro has a type, it should be an unsigned type. -@end defmac - -@defmac LOCAL_DECL_ALIGNMENT (@var{decl}) -If defined, a C expression to compute the alignment for a local -variable @var{decl}. - -If this macro is not defined, then -@code{LOCAL_ALIGNMENT (TREE_TYPE (@var{decl}), DECL_ALIGN (@var{decl}))} -is used. - -One use of this macro is to increase alignment of medium-size data to -make it all fit in fewer cache lines. - -If the value of this macro has a type, it should be an unsigned type. -@end defmac - -@defmac MINIMUM_ALIGNMENT (@var{exp}, @var{mode}, @var{align}) -If defined, a C expression to compute the minimum required alignment -for dynamic stack realignment purposes for @var{exp} (a type or decl), -@var{mode}, assuming normal alignment @var{align}. - -If this macro is not defined, then @var{align} will be used. -@end defmac - -@defmac EMPTY_FIELD_BOUNDARY -Alignment in bits to be given to a structure bit-field that follows an -empty field such as @code{int : 0;}. - -If @code{PCC_BITFIELD_TYPE_MATTERS} is true, it overrides this macro. -@end defmac - -@defmac STRUCTURE_SIZE_BOUNDARY -Number of bits which any structure or union's size must be a multiple of. -Each structure or union's size is rounded up to a multiple of this. - -If you do not define this macro, the default is the same as -@code{BITS_PER_UNIT}. -@end defmac - -@defmac STRICT_ALIGNMENT -Define this macro to be the value 1 if instructions will fail to work -if given data not on the nominal alignment. If instructions will merely -go slower in that case, define this macro as 0. -@end defmac - -@defmac PCC_BITFIELD_TYPE_MATTERS -Define this if you wish to imitate the way many other C compilers handle -alignment of bit-fields and the structures that contain them. - -The behavior is that the type written for a named bit-field (@code{int}, -@code{short}, or other integer type) imposes an alignment for the entire -structure, as if the structure really did contain an ordinary field of -that type. In addition, the bit-field is placed within the structure so -that it would fit within such a field, not crossing a boundary for it. - -Thus, on most machines, a named bit-field whose type is written as -@code{int} would not cross a four-byte boundary, and would force -four-byte alignment for the whole structure. (The alignment used may -not be four bytes; it is controlled by the other alignment parameters.) - -An unnamed bit-field will not affect the alignment of the containing -structure. - -If the macro is defined, its definition should be a C expression; -a nonzero value for the expression enables this behavior. - -Note that if this macro is not defined, or its value is zero, some -bit-fields may cross more than one alignment boundary. The compiler can -support such references if there are @samp{insv}, @samp{extv}, and -@samp{extzv} insns that can directly reference memory. - -The other known way of making bit-fields work is to define -@code{STRUCTURE_SIZE_BOUNDARY} as large as @code{BIGGEST_ALIGNMENT}. -Then every structure can be accessed with fullwords. - -Unless the machine has bit-field instructions or you define -@code{STRUCTURE_SIZE_BOUNDARY} that way, you must define -@code{PCC_BITFIELD_TYPE_MATTERS} to have a nonzero value. - -If your aim is to make GCC use the same conventions for laying out -bit-fields as are used by another compiler, here is how to investigate -what the other compiler does. Compile and run this program: - -@smallexample -struct foo1 -@{ - char x; - char :0; - char y; -@}; - -struct foo2 -@{ - char x; - int :0; - char y; -@}; - -main () -@{ - printf ("Size of foo1 is %d\n", - sizeof (struct foo1)); - printf ("Size of foo2 is %d\n", - sizeof (struct foo2)); - exit (0); -@} -@end smallexample - -If this prints 2 and 5, then the compiler's behavior is what you would -get from @code{PCC_BITFIELD_TYPE_MATTERS}. -@end defmac - -@defmac BITFIELD_NBYTES_LIMITED -Like @code{PCC_BITFIELD_TYPE_MATTERS} except that its effect is limited -to aligning a bit-field within the structure. -@end defmac - -@deftypefn {Target Hook} bool TARGET_ALIGN_ANON_BITFIELD (void) -When @code{PCC_BITFIELD_TYPE_MATTERS} is true this hook will determine -whether unnamed bitfields affect the alignment of the containing -structure. The hook should return true if the structure should inherit -the alignment requirements of an unnamed bitfield's type. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_NARROW_VOLATILE_BITFIELD (void) -This target hook should return @code{true} if accesses to volatile bitfields -should use the narrowest mode possible. It should return @code{false} if -these accesses should use the bitfield container type. - -The default is @code{false}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_MEMBER_TYPE_FORCES_BLK (const_tree @var{field}, machine_mode @var{mode}) -Return true if a structure, union or array containing @var{field} should -be accessed using @code{BLKMODE}. - -If @var{field} is the only field in the structure, @var{mode} is its -mode, otherwise @var{mode} is VOIDmode. @var{mode} is provided in the -case where structures of one field would require the structure's mode to -retain the field's mode. - -Normally, this is not needed. -@end deftypefn - -@defmac ROUND_TYPE_ALIGN (@var{type}, @var{computed}, @var{specified}) -Define this macro as an expression for the alignment of a type (given -by @var{type} as a tree node) if the alignment computed in the usual -way is @var{computed} and the alignment explicitly specified was -@var{specified}. - -The default is to use @var{specified} if it is larger; otherwise, use -the smaller of @var{computed} and @code{BIGGEST_ALIGNMENT} -@end defmac - -@defmac MAX_FIXED_MODE_SIZE -An integer expression for the size in bits of the largest integer -machine mode that should actually be used. All integer machine modes of -this size or smaller can be used for structures and unions with the -appropriate sizes. If this macro is undefined, @code{GET_MODE_BITSIZE -(DImode)} is assumed. -@end defmac - -@defmac STACK_SAVEAREA_MODE (@var{save_level}) -If defined, an expression of type @code{machine_mode} that -specifies the mode of the save area operand of a -@code{save_stack_@var{level}} named pattern (@pxref{Standard Names}). -@var{save_level} is one of @code{SAVE_BLOCK}, @code{SAVE_FUNCTION}, or -@code{SAVE_NONLOCAL} and selects which of the three named patterns is -having its mode specified. - -You need not define this macro if it always returns @code{Pmode}. You -would most commonly define this macro if the -@code{save_stack_@var{level}} patterns need to support both a 32- and a -64-bit mode. -@end defmac - -@defmac STACK_SIZE_MODE -If defined, an expression of type @code{machine_mode} that -specifies the mode of the size increment operand of an -@code{allocate_stack} named pattern (@pxref{Standard Names}). - -You need not define this macro if it always returns @code{word_mode}. -You would most commonly define this macro if the @code{allocate_stack} -pattern needs to support both a 32- and a 64-bit mode. -@end defmac - -@deftypefn {Target Hook} scalar_int_mode TARGET_LIBGCC_CMP_RETURN_MODE (void) -This target hook should return the mode to be used for the return value -of compare instructions expanded to libgcc calls. If not defined -@code{word_mode} is returned which is the right choice for a majority of -targets. -@end deftypefn - -@deftypefn {Target Hook} scalar_int_mode TARGET_LIBGCC_SHIFT_COUNT_MODE (void) -This target hook should return the mode to be used for the shift count operand -of shift instructions expanded to libgcc calls. If not defined -@code{word_mode} is returned which is the right choice for a majority of -targets. -@end deftypefn - -@deftypefn {Target Hook} scalar_int_mode TARGET_UNWIND_WORD_MODE (void) -Return machine mode to be used for @code{_Unwind_Word} type. -The default is to use @code{word_mode}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_MS_BITFIELD_LAYOUT_P (const_tree @var{record_type}) -This target hook returns @code{true} if bit-fields in the given -@var{record_type} are to be laid out following the rules of Microsoft -Visual C/C++, namely: (i) a bit-field won't share the same storage -unit with the previous bit-field if their underlying types have -different sizes, and the bit-field will be aligned to the highest -alignment of the underlying types of itself and of the previous -bit-field; (ii) a zero-sized bit-field will affect the alignment of -the whole enclosing structure, even if it is unnamed; except that -(iii) a zero-sized bit-field will be disregarded unless it follows -another bit-field of nonzero size. If this hook returns @code{true}, -other macros that control bit-field layout are ignored. - -When a bit-field is inserted into a packed record, the whole size -of the underlying type is used by one or more same-size adjacent -bit-fields (that is, if its long:3, 32 bits is used in the record, -and any additional adjacent long bit-fields are packed into the same -chunk of 32 bits. However, if the size changes, a new field of that -size is allocated). In an unpacked record, this is the same as using -alignment, but not equivalent when packing. - -If both MS bit-fields and @samp{__attribute__((packed))} are used, -the latter will take precedence. If @samp{__attribute__((packed))} is -used on a single field when MS bit-fields are in use, it will take -precedence for that field, but the alignment of the rest of the structure -may affect its placement. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_DECIMAL_FLOAT_SUPPORTED_P (void) -Returns true if the target supports decimal floating point. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_FIXED_POINT_SUPPORTED_P (void) -Returns true if the target supports fixed-point arithmetic. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_EXPAND_TO_RTL_HOOK (void) -This hook is called just before expansion into rtl, allowing the target -to perform additional initializations or analysis before the expansion. -For example, the rs6000 port uses it to allocate a scratch stack slot -for use in copying SDmode values between memory and floating point -registers whenever the function being expanded has any SDmode -usage. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_INSTANTIATE_DECLS (void) -This hook allows the backend to perform additional instantiations on rtl -that are not actually in any insns yet, but will be later. -@end deftypefn - -@deftypefn {Target Hook} {const char *} TARGET_MANGLE_TYPE (const_tree @var{type}) -If your target defines any fundamental types, or any types your target -uses should be mangled differently from the default, define this hook -to return the appropriate encoding for these types as part of a C++ -mangled name. The @var{type} argument is the tree structure representing -the type to be mangled. The hook may be applied to trees which are -not target-specific fundamental types; it should return @code{NULL} -for all such types, as well as arguments it does not recognize. If the -return value is not @code{NULL}, it must point to a statically-allocated -string constant. - -Target-specific fundamental types might be new fundamental types or -qualified versions of ordinary fundamental types. Encode new -fundamental types as @samp{@w{u @var{n} @var{name}}}, where @var{name} -is the name used for the type in source code, and @var{n} is the -length of @var{name} in decimal. Encode qualified versions of -ordinary types as @samp{@w{U @var{n} @var{name} @var{code}}}, where -@var{name} is the name used for the type qualifier in source code, -@var{n} is the length of @var{name} as above, and @var{code} is the -code used to represent the unqualified version of this type. (See -@code{write_builtin_type} in @file{cp/mangle.cc} for the list of -codes.) In both cases the spaces are for clarity; do not include any -spaces in your string. - -This hook is applied to types prior to typedef resolution. If the mangled -name for a particular type depends only on that type's main variant, you -can perform typedef resolution yourself using @code{TYPE_MAIN_VARIANT} -before mangling. - -The default version of this hook always returns @code{NULL}, which is -appropriate for a target that does not define any new fundamental -types. -@end deftypefn - -@node Type Layout -@section Layout of Source Language Data Types - -These macros define the sizes and other characteristics of the standard -basic data types used in programs being compiled. Unlike the macros in -the previous section, these apply to specific features of C and related -languages, rather than to fundamental aspects of storage layout. - -@defmac INT_TYPE_SIZE -A C expression for the size in bits of the type @code{int} on the -target machine. If you don't define this, the default is one word. -@end defmac - -@defmac SHORT_TYPE_SIZE -A C expression for the size in bits of the type @code{short} on the -target machine. If you don't define this, the default is half a word. -(If this would be less than one storage unit, it is rounded up to one -unit.) -@end defmac - -@defmac LONG_TYPE_SIZE -A C expression for the size in bits of the type @code{long} on the -target machine. If you don't define this, the default is one word. -@end defmac - -@defmac ADA_LONG_TYPE_SIZE -On some machines, the size used for the Ada equivalent of the type -@code{long} by a native Ada compiler differs from that used by C@. In -that situation, define this macro to be a C expression to be used for -the size of that type. If you don't define this, the default is the -value of @code{LONG_TYPE_SIZE}. -@end defmac - -@defmac LONG_LONG_TYPE_SIZE -A C expression for the size in bits of the type @code{long long} on the -target machine. If you don't define this, the default is two -words. If you want to support GNU Ada on your machine, the value of this -macro must be at least 64. -@end defmac - -@defmac CHAR_TYPE_SIZE -A C expression for the size in bits of the type @code{char} on the -target machine. If you don't define this, the default is -@code{BITS_PER_UNIT}. -@end defmac - -@defmac BOOL_TYPE_SIZE -A C expression for the size in bits of the C++ type @code{bool} and -C99 type @code{_Bool} on the target machine. If you don't define -this, and you probably shouldn't, the default is @code{CHAR_TYPE_SIZE}. -@end defmac - -@defmac FLOAT_TYPE_SIZE -A C expression for the size in bits of the type @code{float} on the -target machine. If you don't define this, the default is one word. -@end defmac - -@defmac DOUBLE_TYPE_SIZE -A C expression for the size in bits of the type @code{double} on the -target machine. If you don't define this, the default is two -words. -@end defmac - -@defmac LONG_DOUBLE_TYPE_SIZE -A C expression for the size in bits of the type @code{long double} on -the target machine. If you don't define this, the default is two -words. -@end defmac - -@defmac SHORT_FRACT_TYPE_SIZE -A C expression for the size in bits of the type @code{short _Fract} on -the target machine. If you don't define this, the default is -@code{BITS_PER_UNIT}. -@end defmac - -@defmac FRACT_TYPE_SIZE -A C expression for the size in bits of the type @code{_Fract} on -the target machine. If you don't define this, the default is -@code{BITS_PER_UNIT * 2}. -@end defmac - -@defmac LONG_FRACT_TYPE_SIZE -A C expression for the size in bits of the type @code{long _Fract} on -the target machine. If you don't define this, the default is -@code{BITS_PER_UNIT * 4}. -@end defmac - -@defmac LONG_LONG_FRACT_TYPE_SIZE -A C expression for the size in bits of the type @code{long long _Fract} on -the target machine. If you don't define this, the default is -@code{BITS_PER_UNIT * 8}. -@end defmac - -@defmac SHORT_ACCUM_TYPE_SIZE -A C expression for the size in bits of the type @code{short _Accum} on -the target machine. If you don't define this, the default is -@code{BITS_PER_UNIT * 2}. -@end defmac - -@defmac ACCUM_TYPE_SIZE -A C expression for the size in bits of the type @code{_Accum} on -the target machine. If you don't define this, the default is -@code{BITS_PER_UNIT * 4}. -@end defmac - -@defmac LONG_ACCUM_TYPE_SIZE -A C expression for the size in bits of the type @code{long _Accum} on -the target machine. If you don't define this, the default is -@code{BITS_PER_UNIT * 8}. -@end defmac - -@defmac LONG_LONG_ACCUM_TYPE_SIZE -A C expression for the size in bits of the type @code{long long _Accum} on -the target machine. If you don't define this, the default is -@code{BITS_PER_UNIT * 16}. -@end defmac - -@defmac LIBGCC2_GNU_PREFIX -This macro corresponds to the @code{TARGET_LIBFUNC_GNU_PREFIX} target -hook and should be defined if that hook is overriden to be true. It -causes function names in libgcc to be changed to use a @code{__gnu_} -prefix for their name rather than the default @code{__}. A port which -uses this macro should also arrange to use @file{t-gnu-prefix} in -the libgcc @file{config.host}. -@end defmac - -@defmac WIDEST_HARDWARE_FP_SIZE -A C expression for the size in bits of the widest floating-point format -supported by the hardware. If you define this macro, you must specify a -value less than or equal to the value of @code{LONG_DOUBLE_TYPE_SIZE}. -If you do not define this macro, the value of @code{LONG_DOUBLE_TYPE_SIZE} -is the default. -@end defmac - -@defmac DEFAULT_SIGNED_CHAR -An expression whose value is 1 or 0, according to whether the type -@code{char} should be signed or unsigned by default. The user can -always override this default with the options @option{-fsigned-char} -and @option{-funsigned-char}. -@end defmac - -@deftypefn {Target Hook} bool TARGET_DEFAULT_SHORT_ENUMS (void) -This target hook should return true if the compiler should give an -@code{enum} type only as many bytes as it takes to represent the range -of possible values of that type. It should return false if all -@code{enum} types should be allocated like @code{int}. - -The default is to return false. -@end deftypefn - -@defmac SIZE_TYPE -A C expression for a string describing the name of the data type to use -for size values. The typedef name @code{size_t} is defined using the -contents of the string. - -The string can contain more than one keyword. If so, separate them with -spaces, and write first any length keyword, then @code{unsigned} if -appropriate, and finally @code{int}. The string must exactly match one -of the data type names defined in the function -@code{c_common_nodes_and_builtins} in the file @file{c-family/c-common.cc}. -You may not omit @code{int} or change the order---that would cause the -compiler to crash on startup. - -If you don't define this macro, the default is @code{"long unsigned -int"}. -@end defmac - -@defmac SIZETYPE -GCC defines internal types (@code{sizetype}, @code{ssizetype}, -@code{bitsizetype} and @code{sbitsizetype}) for expressions -dealing with size. This macro is a C expression for a string describing -the name of the data type from which the precision of @code{sizetype} -is extracted. - -The string has the same restrictions as @code{SIZE_TYPE} string. - -If you don't define this macro, the default is @code{SIZE_TYPE}. -@end defmac - -@defmac PTRDIFF_TYPE -A C expression for a string describing the name of the data type to use -for the result of subtracting two pointers. The typedef name -@code{ptrdiff_t} is defined using the contents of the string. See -@code{SIZE_TYPE} above for more information. - -If you don't define this macro, the default is @code{"long int"}. -@end defmac - -@defmac WCHAR_TYPE -A C expression for a string describing the name of the data type to use -for wide characters. The typedef name @code{wchar_t} is defined using -the contents of the string. See @code{SIZE_TYPE} above for more -information. - -If you don't define this macro, the default is @code{"int"}. -@end defmac - -@defmac WCHAR_TYPE_SIZE -A C expression for the size in bits of the data type for wide -characters. This is used in @code{cpp}, which cannot make use of -@code{WCHAR_TYPE}. -@end defmac - -@defmac WINT_TYPE -A C expression for a string describing the name of the data type to -use for wide characters passed to @code{printf} and returned from -@code{getwc}. The typedef name @code{wint_t} is defined using the -contents of the string. See @code{SIZE_TYPE} above for more -information. - -If you don't define this macro, the default is @code{"unsigned int"}. -@end defmac - -@defmac INTMAX_TYPE -A C expression for a string describing the name of the data type that -can represent any value of any standard or extended signed integer type. -The typedef name @code{intmax_t} is defined using the contents of the -string. See @code{SIZE_TYPE} above for more information. - -If you don't define this macro, the default is the first of -@code{"int"}, @code{"long int"}, or @code{"long long int"} that has as -much precision as @code{long long int}. -@end defmac - -@defmac UINTMAX_TYPE -A C expression for a string describing the name of the data type that -can represent any value of any standard or extended unsigned integer -type. The typedef name @code{uintmax_t} is defined using the contents -of the string. See @code{SIZE_TYPE} above for more information. - -If you don't define this macro, the default is the first of -@code{"unsigned int"}, @code{"long unsigned int"}, or @code{"long long -unsigned int"} that has as much precision as @code{long long unsigned -int}. -@end defmac - -@defmac SIG_ATOMIC_TYPE -@defmacx INT8_TYPE -@defmacx INT16_TYPE -@defmacx INT32_TYPE -@defmacx INT64_TYPE -@defmacx UINT8_TYPE -@defmacx UINT16_TYPE -@defmacx UINT32_TYPE -@defmacx UINT64_TYPE -@defmacx INT_LEAST8_TYPE -@defmacx INT_LEAST16_TYPE -@defmacx INT_LEAST32_TYPE -@defmacx INT_LEAST64_TYPE -@defmacx UINT_LEAST8_TYPE -@defmacx UINT_LEAST16_TYPE -@defmacx UINT_LEAST32_TYPE -@defmacx UINT_LEAST64_TYPE -@defmacx INT_FAST8_TYPE -@defmacx INT_FAST16_TYPE -@defmacx INT_FAST32_TYPE -@defmacx INT_FAST64_TYPE -@defmacx UINT_FAST8_TYPE -@defmacx UINT_FAST16_TYPE -@defmacx UINT_FAST32_TYPE -@defmacx UINT_FAST64_TYPE -@defmacx INTPTR_TYPE -@defmacx UINTPTR_TYPE -C expressions for the standard types @code{sig_atomic_t}, -@code{int8_t}, @code{int16_t}, @code{int32_t}, @code{int64_t}, -@code{uint8_t}, @code{uint16_t}, @code{uint32_t}, @code{uint64_t}, -@code{int_least8_t}, @code{int_least16_t}, @code{int_least32_t}, -@code{int_least64_t}, @code{uint_least8_t}, @code{uint_least16_t}, -@code{uint_least32_t}, @code{uint_least64_t}, @code{int_fast8_t}, -@code{int_fast16_t}, @code{int_fast32_t}, @code{int_fast64_t}, -@code{uint_fast8_t}, @code{uint_fast16_t}, @code{uint_fast32_t}, -@code{uint_fast64_t}, @code{intptr_t}, and @code{uintptr_t}. See -@code{SIZE_TYPE} above for more information. - -If any of these macros evaluates to a null pointer, the corresponding -type is not supported; if GCC is configured to provide -@code{<stdint.h>} in such a case, the header provided may not conform -to C99, depending on the type in question. The defaults for all of -these macros are null pointers. -@end defmac - -@defmac TARGET_PTRMEMFUNC_VBIT_LOCATION -The C++ compiler represents a pointer-to-member-function with a struct -that looks like: - -@smallexample - struct @{ - union @{ - void (*fn)(); - ptrdiff_t vtable_index; - @}; - ptrdiff_t delta; - @}; -@end smallexample - -@noindent -The C++ compiler must use one bit to indicate whether the function that -will be called through a pointer-to-member-function is virtual. -Normally, we assume that the low-order bit of a function pointer must -always be zero. Then, by ensuring that the vtable_index is odd, we can -distinguish which variant of the union is in use. But, on some -platforms function pointers can be odd, and so this doesn't work. In -that case, we use the low-order bit of the @code{delta} field, and shift -the remainder of the @code{delta} field to the left. - -GCC will automatically make the right selection about where to store -this bit using the @code{FUNCTION_BOUNDARY} setting for your platform. -However, some platforms such as ARM/Thumb have @code{FUNCTION_BOUNDARY} -set such that functions always start at even addresses, but the lowest -bit of pointers to functions indicate whether the function at that -address is in ARM or Thumb mode. If this is the case of your -architecture, you should define this macro to -@code{ptrmemfunc_vbit_in_delta}. - -In general, you should not have to define this macro. On architectures -in which function addresses are always even, according to -@code{FUNCTION_BOUNDARY}, GCC will automatically define this macro to -@code{ptrmemfunc_vbit_in_pfn}. -@end defmac - -@defmac TARGET_VTABLE_USES_DESCRIPTORS -Normally, the C++ compiler uses function pointers in vtables. This -macro allows the target to change to use ``function descriptors'' -instead. Function descriptors are found on targets for whom a -function pointer is actually a small data structure. Normally the -data structure consists of the actual code address plus a data -pointer to which the function's data is relative. - -If vtables are used, the value of this macro should be the number -of words that the function descriptor occupies. -@end defmac - -@defmac TARGET_VTABLE_ENTRY_ALIGN -By default, the vtable entries are void pointers, the so the alignment -is the same as pointer alignment. The value of this macro specifies -the alignment of the vtable entry in bits. It should be defined only -when special alignment is necessary. */ -@end defmac - -@defmac TARGET_VTABLE_DATA_ENTRY_DISTANCE -There are a few non-descriptor entries in the vtable at offsets below -zero. If these entries must be padded (say, to preserve the alignment -specified by @code{TARGET_VTABLE_ENTRY_ALIGN}), set this to the number -of words in each data entry. -@end defmac - -@node Registers -@section Register Usage -@cindex register usage - -This section explains how to describe what registers the target machine -has, and how (in general) they can be used. - -The description of which registers a specific instruction can use is -done with register classes; see @ref{Register Classes}. For information -on using registers to access a stack frame, see @ref{Frame Registers}. -For passing values in registers, see @ref{Register Arguments}. -For returning values in registers, see @ref{Scalar Return}. - -@menu -* Register Basics:: Number and kinds of registers. -* Allocation Order:: Order in which registers are allocated. -* Values in Registers:: What kinds of values each reg can hold. -* Leaf Functions:: Renumbering registers for leaf functions. -* Stack Registers:: Handling a register stack such as 80387. -@end menu - -@node Register Basics -@subsection Basic Characteristics of Registers - -@c prevent bad page break with this line -Registers have various characteristics. - -@defmac FIRST_PSEUDO_REGISTER -Number of hardware registers known to the compiler. They receive -numbers 0 through @code{FIRST_PSEUDO_REGISTER-1}; thus, the first -pseudo register's number really is assigned the number -@code{FIRST_PSEUDO_REGISTER}. -@end defmac - -@defmac FIXED_REGISTERS -@cindex fixed register -An initializer that says which registers are used for fixed purposes -all throughout the compiled code and are therefore not available for -general allocation. These would include the stack pointer, the frame -pointer (except on machines where that can be used as a general -register when no frame pointer is needed), the program counter on -machines where that is considered one of the addressable registers, -and any other numbered register with a standard use. - -This information is expressed as a sequence of numbers, separated by -commas and surrounded by braces. The @var{n}th number is 1 if -register @var{n} is fixed, 0 otherwise. - -The table initialized from this macro, and the table initialized by -the following one, may be overridden at run time either automatically, -by the actions of the macro @code{CONDITIONAL_REGISTER_USAGE}, or by -the user with the command options @option{-ffixed-@var{reg}}, -@option{-fcall-used-@var{reg}} and @option{-fcall-saved-@var{reg}}. -@end defmac - -@defmac CALL_USED_REGISTERS -@cindex call-used register -@cindex call-clobbered register -@cindex call-saved register -Like @code{FIXED_REGISTERS} but has 1 for each register that is -clobbered (in general) by function calls as well as for fixed -registers. This macro therefore identifies the registers that are not -available for general allocation of values that must live across -function calls. - -If a register has 0 in @code{CALL_USED_REGISTERS}, the compiler -automatically saves it on function entry and restores it on function -exit, if the register is used within the function. - -Exactly one of @code{CALL_USED_REGISTERS} and @code{CALL_REALLY_USED_REGISTERS} -must be defined. Modern ports should define @code{CALL_REALLY_USED_REGISTERS}. -@end defmac - -@defmac CALL_REALLY_USED_REGISTERS -@cindex call-used register -@cindex call-clobbered register -@cindex call-saved register -Like @code{CALL_USED_REGISTERS} except this macro doesn't require -that the entire set of @code{FIXED_REGISTERS} be included. -(@code{CALL_USED_REGISTERS} must be a superset of @code{FIXED_REGISTERS}). - -Exactly one of @code{CALL_USED_REGISTERS} and @code{CALL_REALLY_USED_REGISTERS} -must be defined. Modern ports should define @code{CALL_REALLY_USED_REGISTERS}. -@end defmac - -@cindex call-used register -@cindex call-clobbered register -@cindex call-saved register -@deftypefn {Target Hook} {const predefined_function_abi &} TARGET_FNTYPE_ABI (const_tree @var{type}) -Return the ABI used by a function with type @var{type}; see the -definition of @code{predefined_function_abi} for details of the ABI -descriptor. Targets only need to define this hook if they support -interoperability between several ABIs in the same translation unit. -@end deftypefn - -@deftypefn {Target Hook} {const predefined_function_abi &} TARGET_INSN_CALLEE_ABI (const rtx_insn *@var{insn}) -This hook returns a description of the ABI used by the target of -call instruction @var{insn}; see the definition of -@code{predefined_function_abi} for details of the ABI descriptor. -Only the global function @code{insn_callee_abi} should call this hook -directly. - -Targets only need to define this hook if they support -interoperability between several ABIs in the same translation unit. -@end deftypefn - -@cindex call-used register -@cindex call-clobbered register -@cindex call-saved register -@deftypefn {Target Hook} bool TARGET_HARD_REGNO_CALL_PART_CLOBBERED (unsigned int @var{abi_id}, unsigned int @var{regno}, machine_mode @var{mode}) -ABIs usually specify that calls must preserve the full contents -of a particular register, or that calls can alter any part of a -particular register. This information is captured by the target macro -@code{CALL_REALLY_USED_REGISTERS}. However, some ABIs specify that calls -must preserve certain bits of a particular register but can alter others. -This hook should return true if this applies to at least one of the -registers in @samp{(reg:@var{mode} @var{regno})}, and if as a result the -call would alter part of the @var{mode} value. For example, if a call -preserves the low 32 bits of a 64-bit hard register @var{regno} but can -clobber the upper 32 bits, this hook should return true for a 64-bit mode -but false for a 32-bit mode. - -The value of @var{abi_id} comes from the @code{predefined_function_abi} -structure that describes the ABI of the call; see the definition of the -structure for more details. If (as is usual) the target uses the same ABI -for all functions in a translation unit, @var{abi_id} is always 0. - -The default implementation returns false, which is correct -for targets that don't have partly call-clobbered registers. -@end deftypefn - -@deftypefn {Target Hook} {const char *} TARGET_GET_MULTILIB_ABI_NAME (void) -This hook returns name of multilib ABI name. -@end deftypefn - -@findex fixed_regs -@findex call_used_regs -@findex global_regs -@findex reg_names -@findex reg_class_contents -@deftypefn {Target Hook} void TARGET_CONDITIONAL_REGISTER_USAGE (void) -This hook may conditionally modify five variables -@code{fixed_regs}, @code{call_used_regs}, @code{global_regs}, -@code{reg_names}, and @code{reg_class_contents}, to take into account -any dependence of these register sets on target flags. The first three -of these are of type @code{char []} (interpreted as boolean vectors). -@code{global_regs} is a @code{const char *[]}, and -@code{reg_class_contents} is a @code{HARD_REG_SET}. Before the macro is -called, @code{fixed_regs}, @code{call_used_regs}, -@code{reg_class_contents}, and @code{reg_names} have been initialized -from @code{FIXED_REGISTERS}, @code{CALL_USED_REGISTERS}, -@code{REG_CLASS_CONTENTS}, and @code{REGISTER_NAMES}, respectively. -@code{global_regs} has been cleared, and any @option{-ffixed-@var{reg}}, -@option{-fcall-used-@var{reg}} and @option{-fcall-saved-@var{reg}} -command options have been applied. - -@cindex disabling certain registers -@cindex controlling register usage -If the usage of an entire class of registers depends on the target -flags, you may indicate this to GCC by using this macro to modify -@code{fixed_regs} and @code{call_used_regs} to 1 for each of the -registers in the classes which should not be used by GCC@. Also make -@code{define_register_constraint}s return @code{NO_REGS} for constraints -that shouldn't be used. - -(However, if this class is not included in @code{GENERAL_REGS} and all -of the insn patterns whose constraints permit this class are -controlled by target switches, then GCC will automatically avoid using -these registers when the target switches are opposed to them.) -@end deftypefn - -@defmac INCOMING_REGNO (@var{out}) -Define this macro if the target machine has register windows. This C -expression returns the register number as seen by the called function -corresponding to the register number @var{out} as seen by the calling -function. Return @var{out} if register number @var{out} is not an -outbound register. -@end defmac - -@defmac OUTGOING_REGNO (@var{in}) -Define this macro if the target machine has register windows. This C -expression returns the register number as seen by the calling function -corresponding to the register number @var{in} as seen by the called -function. Return @var{in} if register number @var{in} is not an inbound -register. -@end defmac - -@defmac LOCAL_REGNO (@var{regno}) -Define this macro if the target machine has register windows. This C -expression returns true if the register is call-saved but is in the -register window. Unlike most call-saved registers, such registers -need not be explicitly restored on function exit or during non-local -gotos. -@end defmac - -@defmac PC_REGNUM -If the program counter has a register number, define this as that -register number. Otherwise, do not define it. -@end defmac - -@node Allocation Order -@subsection Order of Allocation of Registers -@cindex order of register allocation -@cindex register allocation order - -@c prevent bad page break with this line -Registers are allocated in order. - -@defmac REG_ALLOC_ORDER -If defined, an initializer for a vector of integers, containing the -numbers of hard registers in the order in which GCC should prefer -to use them (from most preferred to least). - -If this macro is not defined, registers are used lowest numbered first -(all else being equal). - -One use of this macro is on machines where the highest numbered -registers must always be saved and the save-multiple-registers -instruction supports only sequences of consecutive registers. On such -machines, define @code{REG_ALLOC_ORDER} to be an initializer that lists -the highest numbered allocable register first. -@end defmac - -@defmac ADJUST_REG_ALLOC_ORDER -A C statement (sans semicolon) to choose the order in which to allocate -hard registers for pseudo-registers local to a basic block. - -Store the desired register order in the array @code{reg_alloc_order}. -Element 0 should be the register to allocate first; element 1, the next -register; and so on. - -The macro body should not assume anything about the contents of -@code{reg_alloc_order} before execution of the macro. - -On most machines, it is not necessary to define this macro. -@end defmac - -@defmac HONOR_REG_ALLOC_ORDER -Normally, IRA tries to estimate the costs for saving a register in the -prologue and restoring it in the epilogue. This discourages it from -using call-saved registers. If a machine wants to ensure that IRA -allocates registers in the order given by REG_ALLOC_ORDER even if some -call-saved registers appear earlier than call-used ones, then define this -macro as a C expression to nonzero. Default is 0. -@end defmac - -@defmac IRA_HARD_REGNO_ADD_COST_MULTIPLIER (@var{regno}) -In some case register allocation order is not enough for the -Integrated Register Allocator (@acronym{IRA}) to generate a good code. -If this macro is defined, it should return a floating point value -based on @var{regno}. The cost of using @var{regno} for a pseudo will -be increased by approximately the pseudo's usage frequency times the -value returned by this macro. Not defining this macro is equivalent -to having it always return @code{0.0}. - -On most machines, it is not necessary to define this macro. -@end defmac - -@node Values in Registers -@subsection How Values Fit in Registers - -This section discusses the macros that describe which kinds of values -(specifically, which machine modes) each register can hold, and how many -consecutive registers are needed for a given mode. - -@deftypefn {Target Hook} {unsigned int} TARGET_HARD_REGNO_NREGS (unsigned int @var{regno}, machine_mode @var{mode}) -This hook returns the number of consecutive hard registers, starting -at register number @var{regno}, required to hold a value of mode -@var{mode}. This hook must never return zero, even if a register -cannot hold the requested mode - indicate that with -@code{TARGET_HARD_REGNO_MODE_OK} and/or -@code{TARGET_CAN_CHANGE_MODE_CLASS} instead. - -The default definition returns the number of words in @var{mode}. -@end deftypefn - -@defmac HARD_REGNO_NREGS_HAS_PADDING (@var{regno}, @var{mode}) -A C expression that is nonzero if a value of mode @var{mode}, stored -in memory, ends with padding that causes it to take up more space than -in registers starting at register number @var{regno} (as determined by -multiplying GCC's notion of the size of the register when containing -this mode by the number of registers returned by -@code{TARGET_HARD_REGNO_NREGS}). By default this is zero. - -For example, if a floating-point value is stored in three 32-bit -registers but takes up 128 bits in memory, then this would be -nonzero. - -This macros only needs to be defined if there are cases where -@code{subreg_get_info} -would otherwise wrongly determine that a @code{subreg} can be -represented by an offset to the register number, when in fact such a -@code{subreg} would contain some of the padding not stored in -registers and so not be representable. -@end defmac - -@defmac HARD_REGNO_NREGS_WITH_PADDING (@var{regno}, @var{mode}) -For values of @var{regno} and @var{mode} for which -@code{HARD_REGNO_NREGS_HAS_PADDING} returns nonzero, a C expression -returning the greater number of registers required to hold the value -including any padding. In the example above, the value would be four. -@end defmac - -@defmac REGMODE_NATURAL_SIZE (@var{mode}) -Define this macro if the natural size of registers that hold values -of mode @var{mode} is not the word size. It is a C expression that -should give the natural size in bytes for the specified mode. It is -used by the register allocator to try to optimize its results. This -happens for example on SPARC 64-bit where the natural size of -floating-point registers is still 32-bit. -@end defmac - -@deftypefn {Target Hook} bool TARGET_HARD_REGNO_MODE_OK (unsigned int @var{regno}, machine_mode @var{mode}) -This hook returns true if it is permissible to store a value -of mode @var{mode} in hard register number @var{regno} (or in several -registers starting with that one). The default definition returns true -unconditionally. - -You need not include code to check for the numbers of fixed registers, -because the allocation mechanism considers them to be always occupied. - -@cindex register pairs -On some machines, double-precision values must be kept in even/odd -register pairs. You can implement that by defining this hook to reject -odd register numbers for such modes. - -The minimum requirement for a mode to be OK in a register is that the -@samp{mov@var{mode}} instruction pattern support moves between the -register and other hard register in the same class and that moving a -value into the register and back out not alter it. - -Since the same instruction used to move @code{word_mode} will work for -all narrower integer modes, it is not necessary on any machine for -this hook to distinguish between these modes, provided you define -patterns @samp{movhi}, etc., to take advantage of this. This is -useful because of the interaction between @code{TARGET_HARD_REGNO_MODE_OK} -and @code{TARGET_MODES_TIEABLE_P}; it is very desirable for all integer -modes to be tieable. - -Many machines have special registers for floating point arithmetic. -Often people assume that floating point machine modes are allowed only -in floating point registers. This is not true. Any registers that -can hold integers can safely @emph{hold} a floating point machine -mode, whether or not floating arithmetic can be done on it in those -registers. Integer move instructions can be used to move the values. - -On some machines, though, the converse is true: fixed-point machine -modes may not go in floating registers. This is true if the floating -registers normalize any value stored in them, because storing a -non-floating value there would garble it. In this case, -@code{TARGET_HARD_REGNO_MODE_OK} should reject fixed-point machine modes in -floating registers. But if the floating registers do not automatically -normalize, if you can store any bit pattern in one and retrieve it -unchanged without a trap, then any machine mode may go in a floating -register, so you can define this hook to say so. - -The primary significance of special floating registers is rather that -they are the registers acceptable in floating point arithmetic -instructions. However, this is of no concern to -@code{TARGET_HARD_REGNO_MODE_OK}. You handle it by writing the proper -constraints for those instructions. - -On some machines, the floating registers are especially slow to access, -so that it is better to store a value in a stack frame than in such a -register if floating point arithmetic is not being done. As long as the -floating registers are not in class @code{GENERAL_REGS}, they will not -be used unless some pattern's constraint asks for one. -@end deftypefn - -@defmac HARD_REGNO_RENAME_OK (@var{from}, @var{to}) -A C expression that is nonzero if it is OK to rename a hard register -@var{from} to another hard register @var{to}. - -One common use of this macro is to prevent renaming of a register to -another register that is not saved by a prologue in an interrupt -handler. - -The default is always nonzero. -@end defmac - -@deftypefn {Target Hook} bool TARGET_MODES_TIEABLE_P (machine_mode @var{mode1}, machine_mode @var{mode2}) -This hook returns true if a value of mode @var{mode1} is accessible -in mode @var{mode2} without copying. - -If @code{TARGET_HARD_REGNO_MODE_OK (@var{r}, @var{mode1})} and -@code{TARGET_HARD_REGNO_MODE_OK (@var{r}, @var{mode2})} are always -the same for any @var{r}, then -@code{TARGET_MODES_TIEABLE_P (@var{mode1}, @var{mode2})} -should be true. If they differ for any @var{r}, you should define -this hook to return false unless some other mechanism ensures the -accessibility of the value in a narrower mode. - -You should define this hook to return true in as many cases as -possible since doing so will allow GCC to perform better register -allocation. The default definition returns true unconditionally. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_HARD_REGNO_SCRATCH_OK (unsigned int @var{regno}) -This target hook should return @code{true} if it is OK to use a hard register -@var{regno} as scratch reg in peephole2. - -One common use of this macro is to prevent using of a register that -is not saved by a prologue in an interrupt handler. - -The default version of this hook always returns @code{true}. -@end deftypefn - -@defmac AVOID_CCMODE_COPIES -Define this macro if the compiler should avoid copies to/from @code{CCmode} -registers. You should only define this macro if support for copying to/from -@code{CCmode} is incomplete. -@end defmac - -@node Leaf Functions -@subsection Handling Leaf Functions - -@cindex leaf functions -@cindex functions, leaf -On some machines, a leaf function (i.e., one which makes no calls) can run -more efficiently if it does not make its own register window. Often this -means it is required to receive its arguments in the registers where they -are passed by the caller, instead of the registers where they would -normally arrive. - -The special treatment for leaf functions generally applies only when -other conditions are met; for example, often they may use only those -registers for its own variables and temporaries. We use the term ``leaf -function'' to mean a function that is suitable for this special -handling, so that functions with no calls are not necessarily ``leaf -functions''. - -GCC assigns register numbers before it knows whether the function is -suitable for leaf function treatment. So it needs to renumber the -registers in order to output a leaf function. The following macros -accomplish this. - -@defmac LEAF_REGISTERS -Name of a char vector, indexed by hard register number, which -contains 1 for a register that is allowable in a candidate for leaf -function treatment. - -If leaf function treatment involves renumbering the registers, then the -registers marked here should be the ones before renumbering---those that -GCC would ordinarily allocate. The registers which will actually be -used in the assembler code, after renumbering, should not be marked with 1 -in this vector. - -Define this macro only if the target machine offers a way to optimize -the treatment of leaf functions. -@end defmac - -@defmac LEAF_REG_REMAP (@var{regno}) -A C expression whose value is the register number to which @var{regno} -should be renumbered, when a function is treated as a leaf function. - -If @var{regno} is a register number which should not appear in a leaf -function before renumbering, then the expression should yield @minus{}1, which -will cause the compiler to abort. - -Define this macro only if the target machine offers a way to optimize the -treatment of leaf functions, and registers need to be renumbered to do -this. -@end defmac - -@findex current_function_is_leaf -@findex current_function_uses_only_leaf_regs -@code{TARGET_ASM_FUNCTION_PROLOGUE} and -@code{TARGET_ASM_FUNCTION_EPILOGUE} must usually treat leaf functions -specially. They can test the C variable @code{current_function_is_leaf} -which is nonzero for leaf functions. @code{current_function_is_leaf} is -set prior to local register allocation and is valid for the remaining -compiler passes. They can also test the C variable -@code{current_function_uses_only_leaf_regs} which is nonzero for leaf -functions which only use leaf registers. -@code{current_function_uses_only_leaf_regs} is valid after all passes -that modify the instructions have been run and is only useful if -@code{LEAF_REGISTERS} is defined. -@c changed this to fix overfull. ALSO: why the "it" at the beginning -@c of the next paragraph?! --mew 2feb93 - -@node Stack Registers -@subsection Registers That Form a Stack - -There are special features to handle computers where some of the -``registers'' form a stack. Stack registers are normally written by -pushing onto the stack, and are numbered relative to the top of the -stack. - -Currently, GCC can only handle one group of stack-like registers, and -they must be consecutively numbered. Furthermore, the existing -support for stack-like registers is specific to the 80387 floating -point coprocessor. If you have a new architecture that uses -stack-like registers, you will need to do substantial work on -@file{reg-stack.cc} and write your machine description to cooperate -with it, as well as defining these macros. - -@defmac STACK_REGS -Define this if the machine has any stack-like registers. -@end defmac - -@defmac STACK_REG_COVER_CLASS -This is a cover class containing the stack registers. Define this if -the machine has any stack-like registers. -@end defmac - -@defmac FIRST_STACK_REG -The number of the first stack-like register. This one is the top -of the stack. -@end defmac - -@defmac LAST_STACK_REG -The number of the last stack-like register. This one is the bottom of -the stack. -@end defmac - -@node Register Classes -@section Register Classes -@cindex register class definitions -@cindex class definitions, register - -On many machines, the numbered registers are not all equivalent. -For example, certain registers may not be allowed for indexed addressing; -certain registers may not be allowed in some instructions. These machine -restrictions are described to the compiler using @dfn{register classes}. - -You define a number of register classes, giving each one a name and saying -which of the registers belong to it. Then you can specify register classes -that are allowed as operands to particular instruction patterns. - -@findex ALL_REGS -@findex NO_REGS -In general, each register will belong to several classes. In fact, one -class must be named @code{ALL_REGS} and contain all the registers. Another -class must be named @code{NO_REGS} and contain no registers. Often the -union of two classes will be another class; however, this is not required. - -@findex GENERAL_REGS -One of the classes must be named @code{GENERAL_REGS}. There is nothing -terribly special about the name, but the operand constraint letters -@samp{r} and @samp{g} specify this class. If @code{GENERAL_REGS} is -the same as @code{ALL_REGS}, just define it as a macro which expands -to @code{ALL_REGS}. - -Order the classes so that if class @var{x} is contained in class @var{y} -then @var{x} has a lower class number than @var{y}. - -The way classes other than @code{GENERAL_REGS} are specified in operand -constraints is through machine-dependent operand constraint letters. -You can define such letters to correspond to various classes, then use -them in operand constraints. - -You must define the narrowest register classes for allocatable -registers, so that each class either has no subclasses, or that for -some mode, the move cost between registers within the class is -cheaper than moving a register in the class to or from memory -(@pxref{Costs}). - -You should define a class for the union of two classes whenever some -instruction allows both classes. For example, if an instruction allows -either a floating point (coprocessor) register or a general register for a -certain operand, you should define a class @code{FLOAT_OR_GENERAL_REGS} -which includes both of them. Otherwise you will get suboptimal code, -or even internal compiler errors when reload cannot find a register in the -class computed via @code{reg_class_subunion}. - -You must also specify certain redundant information about the register -classes: for each class, which classes contain it and which ones are -contained in it; for each pair of classes, the largest class contained -in their union. - -When a value occupying several consecutive registers is expected in a -certain class, all the registers used must belong to that class. -Therefore, register classes cannot be used to enforce a requirement for -a register pair to start with an even-numbered register. The way to -specify this requirement is with @code{TARGET_HARD_REGNO_MODE_OK}. - -Register classes used for input-operands of bitwise-and or shift -instructions have a special requirement: each such class must have, for -each fixed-point machine mode, a subclass whose registers can transfer that -mode to or from memory. For example, on some machines, the operations for -single-byte values (@code{QImode}) are limited to certain registers. When -this is so, each register class that is used in a bitwise-and or shift -instruction must have a subclass consisting of registers from which -single-byte values can be loaded or stored. This is so that -@code{PREFERRED_RELOAD_CLASS} can always have a possible value to return. - -@deftp {Data type} {enum reg_class} -An enumerated type that must be defined with all the register class names -as enumerated values. @code{NO_REGS} must be first. @code{ALL_REGS} -must be the last register class, followed by one more enumerated value, -@code{LIM_REG_CLASSES}, which is not a register class but rather -tells how many classes there are. - -Each register class has a number, which is the value of casting -the class name to type @code{int}. The number serves as an index -in many of the tables described below. -@end deftp - -@defmac N_REG_CLASSES -The number of distinct register classes, defined as follows: - -@smallexample -#define N_REG_CLASSES (int) LIM_REG_CLASSES -@end smallexample -@end defmac - -@defmac REG_CLASS_NAMES -An initializer containing the names of the register classes as C string -constants. These names are used in writing some of the debugging dumps. -@end defmac - -@defmac REG_CLASS_CONTENTS -An initializer containing the contents of the register classes, as integers -which are bit masks. The @var{n}th integer specifies the contents of class -@var{n}. The way the integer @var{mask} is interpreted is that -register @var{r} is in the class if @code{@var{mask} & (1 << @var{r})} is 1. - -When the machine has more than 32 registers, an integer does not suffice. -Then the integers are replaced by sub-initializers, braced groupings containing -several integers. Each sub-initializer must be suitable as an initializer -for the type @code{HARD_REG_SET} which is defined in @file{hard-reg-set.h}. -In this situation, the first integer in each sub-initializer corresponds to -registers 0 through 31, the second integer to registers 32 through 63, and -so on. -@end defmac - -@defmac REGNO_REG_CLASS (@var{regno}) -A C expression whose value is a register class containing hard register -@var{regno}. In general there is more than one such class; choose a class -which is @dfn{minimal}, meaning that no smaller class also contains the -register. -@end defmac - -@defmac BASE_REG_CLASS -A macro whose definition is the name of the class to which a valid -base register must belong. A base register is one used in an address -which is the register value plus a displacement. -@end defmac - -@defmac MODE_BASE_REG_CLASS (@var{mode}) -This is a variation of the @code{BASE_REG_CLASS} macro which allows -the selection of a base register in a mode dependent manner. If -@var{mode} is VOIDmode then it should return the same value as -@code{BASE_REG_CLASS}. -@end defmac - -@defmac MODE_BASE_REG_REG_CLASS (@var{mode}) -A C expression whose value is the register class to which a valid -base register must belong in order to be used in a base plus index -register address. You should define this macro if base plus index -addresses have different requirements than other base register uses. -@end defmac - -@defmac MODE_CODE_BASE_REG_CLASS (@var{mode}, @var{address_space}, @var{outer_code}, @var{index_code}) -A C expression whose value is the register class to which a valid -base register for a memory reference in mode @var{mode} to address -space @var{address_space} must belong. @var{outer_code} and @var{index_code} -define the context in which the base register occurs. @var{outer_code} is -the code of the immediately enclosing expression (@code{MEM} for the top level -of an address, @code{ADDRESS} for something that occurs in an -@code{address_operand}). @var{index_code} is the code of the corresponding -index expression if @var{outer_code} is @code{PLUS}; @code{SCRATCH} otherwise. -@end defmac - -@defmac INDEX_REG_CLASS -A macro whose definition is the name of the class to which a valid -index register must belong. An index register is one used in an -address where its value is either multiplied by a scale factor or -added to another register (as well as added to a displacement). -@end defmac - -@defmac REGNO_OK_FOR_BASE_P (@var{num}) -A C expression which is nonzero if register number @var{num} is -suitable for use as a base register in operand addresses. -@end defmac - -@defmac REGNO_MODE_OK_FOR_BASE_P (@var{num}, @var{mode}) -A C expression that is just like @code{REGNO_OK_FOR_BASE_P}, except that -that expression may examine the mode of the memory reference in -@var{mode}. You should define this macro if the mode of the memory -reference affects whether a register may be used as a base register. If -you define this macro, the compiler will use it instead of -@code{REGNO_OK_FOR_BASE_P}. The mode may be @code{VOIDmode} for -addresses that appear outside a @code{MEM}, i.e., as an -@code{address_operand}. -@end defmac - -@defmac REGNO_MODE_OK_FOR_REG_BASE_P (@var{num}, @var{mode}) -A C expression which is nonzero if register number @var{num} is suitable for -use as a base register in base plus index operand addresses, accessing -memory in mode @var{mode}. It may be either a suitable hard register or a -pseudo register that has been allocated such a hard register. You should -define this macro if base plus index addresses have different requirements -than other base register uses. - -Use of this macro is deprecated; please use the more general -@code{REGNO_MODE_CODE_OK_FOR_BASE_P}. -@end defmac - -@defmac REGNO_MODE_CODE_OK_FOR_BASE_P (@var{num}, @var{mode}, @var{address_space}, @var{outer_code}, @var{index_code}) -A C expression which is nonzero if register number @var{num} is -suitable for use as a base register in operand addresses, accessing -memory in mode @var{mode} in address space @var{address_space}. -This is similar to @code{REGNO_MODE_OK_FOR_BASE_P}, except -that that expression may examine the context in which the register -appears in the memory reference. @var{outer_code} is the code of the -immediately enclosing expression (@code{MEM} if at the top level of the -address, @code{ADDRESS} for something that occurs in an -@code{address_operand}). @var{index_code} is the code of the -corresponding index expression if @var{outer_code} is @code{PLUS}; -@code{SCRATCH} otherwise. The mode may be @code{VOIDmode} for addresses -that appear outside a @code{MEM}, i.e., as an @code{address_operand}. -@end defmac - -@defmac REGNO_OK_FOR_INDEX_P (@var{num}) -A C expression which is nonzero if register number @var{num} is -suitable for use as an index register in operand addresses. It may be -either a suitable hard register or a pseudo register that has been -allocated such a hard register. - -The difference between an index register and a base register is that -the index register may be scaled. If an address involves the sum of -two registers, neither one of them scaled, then either one may be -labeled the ``base'' and the other the ``index''; but whichever -labeling is used must fit the machine's constraints of which registers -may serve in each capacity. The compiler will try both labelings, -looking for one that is valid, and will reload one or both registers -only if neither labeling works. -@end defmac - -@deftypefn {Target Hook} reg_class_t TARGET_PREFERRED_RENAME_CLASS (reg_class_t @var{rclass}) -A target hook that places additional preference on the register -class to use when it is necessary to rename a register in class -@var{rclass} to another class, or perhaps @var{NO_REGS}, if no -preferred register class is found or hook @code{preferred_rename_class} -is not implemented. -Sometimes returning a more restrictive class makes better code. For -example, on ARM, thumb-2 instructions using @code{LO_REGS} may be -smaller than instructions using @code{GENERIC_REGS}. By returning -@code{LO_REGS} from @code{preferred_rename_class}, code size can -be reduced. -@end deftypefn - -@deftypefn {Target Hook} reg_class_t TARGET_PREFERRED_RELOAD_CLASS (rtx @var{x}, reg_class_t @var{rclass}) -A target hook that places additional restrictions on the register class -to use when it is necessary to copy value @var{x} into a register in class -@var{rclass}. The value is a register class; perhaps @var{rclass}, or perhaps -another, smaller class. - -The default version of this hook always returns value of @code{rclass} argument. - -Sometimes returning a more restrictive class makes better code. For -example, on the 68000, when @var{x} is an integer constant that is in range -for a @samp{moveq} instruction, the value of this macro is always -@code{DATA_REGS} as long as @var{rclass} includes the data registers. -Requiring a data register guarantees that a @samp{moveq} will be used. - -One case where @code{TARGET_PREFERRED_RELOAD_CLASS} must not return -@var{rclass} is if @var{x} is a legitimate constant which cannot be -loaded into some register class. By returning @code{NO_REGS} you can -force @var{x} into a memory location. For example, rs6000 can load -immediate values into general-purpose registers, but does not have an -instruction for loading an immediate value into a floating-point -register, so @code{TARGET_PREFERRED_RELOAD_CLASS} returns @code{NO_REGS} when -@var{x} is a floating-point constant. If the constant can't be loaded -into any kind of register, code generation will be better if -@code{TARGET_LEGITIMATE_CONSTANT_P} makes the constant illegitimate instead -of using @code{TARGET_PREFERRED_RELOAD_CLASS}. - -If an insn has pseudos in it after register allocation, reload will go -through the alternatives and call repeatedly @code{TARGET_PREFERRED_RELOAD_CLASS} -to find the best one. Returning @code{NO_REGS}, in this case, makes -reload add a @code{!} in front of the constraint: the x86 back-end uses -this feature to discourage usage of 387 registers when math is done in -the SSE registers (and vice versa). -@end deftypefn - -@defmac PREFERRED_RELOAD_CLASS (@var{x}, @var{class}) -A C expression that places additional restrictions on the register class -to use when it is necessary to copy value @var{x} into a register in class -@var{class}. The value is a register class; perhaps @var{class}, or perhaps -another, smaller class. On many machines, the following definition is -safe: - -@smallexample -#define PREFERRED_RELOAD_CLASS(X,CLASS) CLASS -@end smallexample - -Sometimes returning a more restrictive class makes better code. For -example, on the 68000, when @var{x} is an integer constant that is in range -for a @samp{moveq} instruction, the value of this macro is always -@code{DATA_REGS} as long as @var{class} includes the data registers. -Requiring a data register guarantees that a @samp{moveq} will be used. - -One case where @code{PREFERRED_RELOAD_CLASS} must not return -@var{class} is if @var{x} is a legitimate constant which cannot be -loaded into some register class. By returning @code{NO_REGS} you can -force @var{x} into a memory location. For example, rs6000 can load -immediate values into general-purpose registers, but does not have an -instruction for loading an immediate value into a floating-point -register, so @code{PREFERRED_RELOAD_CLASS} returns @code{NO_REGS} when -@var{x} is a floating-point constant. If the constant cannot be loaded -into any kind of register, code generation will be better if -@code{TARGET_LEGITIMATE_CONSTANT_P} makes the constant illegitimate instead -of using @code{TARGET_PREFERRED_RELOAD_CLASS}. - -If an insn has pseudos in it after register allocation, reload will go -through the alternatives and call repeatedly @code{PREFERRED_RELOAD_CLASS} -to find the best one. Returning @code{NO_REGS}, in this case, makes -reload add a @code{!} in front of the constraint: the x86 back-end uses -this feature to discourage usage of 387 registers when math is done in -the SSE registers (and vice versa). -@end defmac - -@deftypefn {Target Hook} reg_class_t TARGET_PREFERRED_OUTPUT_RELOAD_CLASS (rtx @var{x}, reg_class_t @var{rclass}) -Like @code{TARGET_PREFERRED_RELOAD_CLASS}, but for output reloads instead of -input reloads. - -The default version of this hook always returns value of @code{rclass} -argument. - -You can also use @code{TARGET_PREFERRED_OUTPUT_RELOAD_CLASS} to discourage -reload from using some alternatives, like @code{TARGET_PREFERRED_RELOAD_CLASS}. -@end deftypefn - -@defmac LIMIT_RELOAD_CLASS (@var{mode}, @var{class}) -A C expression that places additional restrictions on the register class -to use when it is necessary to be able to hold a value of mode -@var{mode} in a reload register for which class @var{class} would -ordinarily be used. - -Unlike @code{PREFERRED_RELOAD_CLASS}, this macro should be used when -there are certain modes that simply cannot go in certain reload classes. - -The value is a register class; perhaps @var{class}, or perhaps another, -smaller class. - -Don't define this macro unless the target machine has limitations which -require the macro to do something nontrivial. -@end defmac - -@deftypefn {Target Hook} reg_class_t TARGET_SECONDARY_RELOAD (bool @var{in_p}, rtx @var{x}, reg_class_t @var{reload_class}, machine_mode @var{reload_mode}, secondary_reload_info *@var{sri}) -Many machines have some registers that cannot be copied directly to or -from memory or even from other types of registers. An example is the -@samp{MQ} register, which on most machines, can only be copied to or -from general registers, but not memory. Below, we shall be using the -term 'intermediate register' when a move operation cannot be performed -directly, but has to be done by copying the source into the intermediate -register first, and then copying the intermediate register to the -destination. An intermediate register always has the same mode as -source and destination. Since it holds the actual value being copied, -reload might apply optimizations to re-use an intermediate register -and eliding the copy from the source when it can determine that the -intermediate register still holds the required value. - -Another kind of secondary reload is required on some machines which -allow copying all registers to and from memory, but require a scratch -register for stores to some memory locations (e.g., those with symbolic -address on the RT, and those with certain symbolic address on the SPARC -when compiling PIC)@. Scratch registers need not have the same mode -as the value being copied, and usually hold a different value than -that being copied. Special patterns in the md file are needed to -describe how the copy is performed with the help of the scratch register; -these patterns also describe the number, register class(es) and mode(s) -of the scratch register(s). - -In some cases, both an intermediate and a scratch register are required. - -For input reloads, this target hook is called with nonzero @var{in_p}, -and @var{x} is an rtx that needs to be copied to a register of class -@var{reload_class} in @var{reload_mode}. For output reloads, this target -hook is called with zero @var{in_p}, and a register of class @var{reload_class} -needs to be copied to rtx @var{x} in @var{reload_mode}. - -If copying a register of @var{reload_class} from/to @var{x} requires -an intermediate register, the hook @code{secondary_reload} should -return the register class required for this intermediate register. -If no intermediate register is required, it should return NO_REGS. -If more than one intermediate register is required, describe the one -that is closest in the copy chain to the reload register. - -If scratch registers are needed, you also have to describe how to -perform the copy from/to the reload register to/from this -closest intermediate register. Or if no intermediate register is -required, but still a scratch register is needed, describe the -copy from/to the reload register to/from the reload operand @var{x}. - -You do this by setting @code{sri->icode} to the instruction code of a pattern -in the md file which performs the move. Operands 0 and 1 are the output -and input of this copy, respectively. Operands from operand 2 onward are -for scratch operands. These scratch operands must have a mode, and a -single-register-class -@c [later: or memory] -output constraint. - -When an intermediate register is used, the @code{secondary_reload} -hook will be called again to determine how to copy the intermediate -register to/from the reload operand @var{x}, so your hook must also -have code to handle the register class of the intermediate operand. - -@c [For later: maybe we'll allow multi-alternative reload patterns - -@c the port maintainer could name a mov<mode> pattern that has clobbers - -@c and match the constraints of input and output to determine the required -@c alternative. A restriction would be that constraints used to match -@c against reloads registers would have to be written as register class -@c constraints, or we need a new target macro / hook that tells us if an -@c arbitrary constraint can match an unknown register of a given class. -@c Such a macro / hook would also be useful in other places.] - - -@var{x} might be a pseudo-register or a @code{subreg} of a -pseudo-register, which could either be in a hard register or in memory. -Use @code{true_regnum} to find out; it will return @minus{}1 if the pseudo is -in memory and the hard register number if it is in a register. - -Scratch operands in memory (constraint @code{"=m"} / @code{"=&m"}) are -currently not supported. For the time being, you will have to continue -to use @code{TARGET_SECONDARY_MEMORY_NEEDED} for that purpose. - -@code{copy_cost} also uses this target hook to find out how values are -copied. If you want it to include some extra cost for the need to allocate -(a) scratch register(s), set @code{sri->extra_cost} to the additional cost. -Or if two dependent moves are supposed to have a lower cost than the sum -of the individual moves due to expected fortuitous scheduling and/or special -forwarding logic, you can set @code{sri->extra_cost} to a negative amount. -@end deftypefn - -@defmac SECONDARY_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) -@defmacx SECONDARY_INPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) -@defmacx SECONDARY_OUTPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x}) -These macros are obsolete, new ports should use the target hook -@code{TARGET_SECONDARY_RELOAD} instead. - -These are obsolete macros, replaced by the @code{TARGET_SECONDARY_RELOAD} -target hook. Older ports still define these macros to indicate to the -reload phase that it may -need to allocate at least one register for a reload in addition to the -register to contain the data. Specifically, if copying @var{x} to a -register @var{class} in @var{mode} requires an intermediate register, -you were supposed to define @code{SECONDARY_INPUT_RELOAD_CLASS} to return the -largest register class all of whose registers can be used as -intermediate registers or scratch registers. - -If copying a register @var{class} in @var{mode} to @var{x} requires an -intermediate or scratch register, @code{SECONDARY_OUTPUT_RELOAD_CLASS} -was supposed to be defined to return the largest register -class required. If the -requirements for input and output reloads were the same, the macro -@code{SECONDARY_RELOAD_CLASS} should have been used instead of defining both -macros identically. - -The values returned by these macros are often @code{GENERAL_REGS}. -Return @code{NO_REGS} if no spare register is needed; i.e., if @var{x} -can be directly copied to or from a register of @var{class} in -@var{mode} without requiring a scratch register. Do not define this -macro if it would always return @code{NO_REGS}. - -If a scratch register is required (either with or without an -intermediate register), you were supposed to define patterns for -@samp{reload_in@var{m}} or @samp{reload_out@var{m}}, as required -(@pxref{Standard Names}. These patterns, which were normally -implemented with a @code{define_expand}, should be similar to the -@samp{mov@var{m}} patterns, except that operand 2 is the scratch -register. - -These patterns need constraints for the reload register and scratch -register that -contain a single register class. If the original reload register (whose -class is @var{class}) can meet the constraint given in the pattern, the -value returned by these macros is used for the class of the scratch -register. Otherwise, two additional reload registers are required. -Their classes are obtained from the constraints in the insn pattern. - -@var{x} might be a pseudo-register or a @code{subreg} of a -pseudo-register, which could either be in a hard register or in memory. -Use @code{true_regnum} to find out; it will return @minus{}1 if the pseudo is -in memory and the hard register number if it is in a register. - -These macros should not be used in the case where a particular class of -registers can only be copied to memory and not to another class of -registers. In that case, secondary reload registers are not needed and -would not be helpful. Instead, a stack location must be used to perform -the copy and the @code{mov@var{m}} pattern should use memory as an -intermediate storage. This case often occurs between floating-point and -general registers. -@end defmac - -@deftypefn {Target Hook} bool TARGET_SECONDARY_MEMORY_NEEDED (machine_mode @var{mode}, reg_class_t @var{class1}, reg_class_t @var{class2}) -Certain machines have the property that some registers cannot be copied -to some other registers without using memory. Define this hook on -those machines to return true if objects of mode @var{m} in registers -of @var{class1} can only be copied to registers of class @var{class2} by - storing a register of @var{class1} into memory and loading that memory -location into a register of @var{class2}. The default definition returns -false for all inputs. -@end deftypefn - -@defmac SECONDARY_MEMORY_NEEDED_RTX (@var{mode}) -Normally when @code{TARGET_SECONDARY_MEMORY_NEEDED} is defined, the compiler -allocates a stack slot for a memory location needed for register copies. -If this macro is defined, the compiler instead uses the memory location -defined by this macro. - -Do not define this macro if you do not define -@code{TARGET_SECONDARY_MEMORY_NEEDED}. -@end defmac - -@deftypefn {Target Hook} machine_mode TARGET_SECONDARY_MEMORY_NEEDED_MODE (machine_mode @var{mode}) -If @code{TARGET_SECONDARY_MEMORY_NEEDED} tells the compiler to use memory -when moving between two particular registers of mode @var{mode}, -this hook specifies the mode that the memory should have. - -The default depends on @code{TARGET_LRA_P}. Without LRA, the default -is to use a word-sized mode for integral modes that are smaller than a -a word. This is right thing to do on most machines because it ensures -that all bits of the register are copied and prevents accesses to the -registers in a narrower mode, which some machines prohibit for -floating-point registers. - -However, this default behavior is not correct on some machines, such as -the DEC Alpha, that store short integers in floating-point registers -differently than in integer registers. On those machines, the default -widening will not work correctly and you must define this hook to -suppress that widening in some cases. See the file @file{alpha.cc} for -details. - -With LRA, the default is to use @var{mode} unmodified. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SELECT_EARLY_REMAT_MODES (sbitmap @var{modes}) -On some targets, certain modes cannot be held in registers around a -standard ABI call and are relatively expensive to spill to the stack. -The early rematerialization pass can help in such cases by aggressively -recomputing values after calls, so that they don't need to be spilled. - -This hook returns the set of such modes by setting the associated bits -in @var{modes}. The default implementation selects no modes, which has -the effect of disabling the early rematerialization pass. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CLASS_LIKELY_SPILLED_P (reg_class_t @var{rclass}) -A target hook which returns @code{true} if pseudos that have been assigned -to registers of class @var{rclass} would likely be spilled because -registers of @var{rclass} are needed for spill registers. - -The default version of this target hook returns @code{true} if @var{rclass} -has exactly one register and @code{false} otherwise. On most machines, this -default should be used. For generally register-starved machines, such as -i386, or machines with right register constraints, such as SH, this hook -can be used to avoid excessive spilling. - -This hook is also used by some of the global intra-procedural code -transformations to throtle code motion, to avoid increasing register -pressure. -@end deftypefn - -@deftypefn {Target Hook} {unsigned char} TARGET_CLASS_MAX_NREGS (reg_class_t @var{rclass}, machine_mode @var{mode}) -A target hook returns the maximum number of consecutive registers -of class @var{rclass} needed to hold a value of mode @var{mode}. - -This is closely related to the macro @code{TARGET_HARD_REGNO_NREGS}. -In fact, the value returned by @code{TARGET_CLASS_MAX_NREGS (@var{rclass}, -@var{mode})} target hook should be the maximum value of -@code{TARGET_HARD_REGNO_NREGS (@var{regno}, @var{mode})} for all @var{regno} -values in the class @var{rclass}. - -This target hook helps control the handling of multiple-word values -in the reload pass. - -The default version of this target hook returns the size of @var{mode} -in words. -@end deftypefn - -@defmac CLASS_MAX_NREGS (@var{class}, @var{mode}) -A C expression for the maximum number of consecutive registers -of class @var{class} needed to hold a value of mode @var{mode}. - -This is closely related to the macro @code{TARGET_HARD_REGNO_NREGS}. In fact, -the value of the macro @code{CLASS_MAX_NREGS (@var{class}, @var{mode})} -should be the maximum value of @code{TARGET_HARD_REGNO_NREGS (@var{regno}, -@var{mode})} for all @var{regno} values in the class @var{class}. - -This macro helps control the handling of multiple-word values -in the reload pass. -@end defmac - -@deftypefn {Target Hook} bool TARGET_CAN_CHANGE_MODE_CLASS (machine_mode @var{from}, machine_mode @var{to}, reg_class_t @var{rclass}) -This hook returns true if it is possible to bitcast values held in -registers of class @var{rclass} from mode @var{from} to mode @var{to} -and if doing so preserves the low-order bits that are common to both modes. -The result is only meaningful if @var{rclass} has registers that can hold -both @code{from} and @code{to}. The default implementation returns true. - -As an example of when such bitcasting is invalid, loading 32-bit integer or -floating-point objects into floating-point registers on Alpha extends them -to 64 bits. Therefore loading a 64-bit object and then storing it as a -32-bit object does not store the low-order 32 bits, as would be the case -for a normal register. Therefore, @file{alpha.h} defines -@code{TARGET_CAN_CHANGE_MODE_CLASS} to return: - -@smallexample -(GET_MODE_SIZE (from) == GET_MODE_SIZE (to) - || !reg_classes_intersect_p (FLOAT_REGS, rclass)) -@end smallexample - -Even if storing from a register in mode @var{to} would be valid, -if both @var{from} and @code{raw_reg_mode} for @var{rclass} are wider -than @code{word_mode}, then we must prevent @var{to} narrowing the -mode. This happens when the middle-end assumes that it can load -or store pieces of an @var{N}-word pseudo, and that the pseudo will -eventually be allocated to @var{N} @code{word_mode} hard registers. -Failure to prevent this kind of mode change will result in the -entire @code{raw_reg_mode} being modified instead of the partial -value that the middle-end intended. -@end deftypefn - -@deftypefn {Target Hook} reg_class_t TARGET_IRA_CHANGE_PSEUDO_ALLOCNO_CLASS (int, @var{reg_class_t}, @var{reg_class_t}) -A target hook which can change allocno class for given pseudo from - allocno and best class calculated by IRA. - - The default version of this target hook always returns given class. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_LRA_P (void) -A target hook which returns true if we use LRA instead of reload pass. - -The default version of this target hook returns true. New ports -should use LRA, and existing ports are encouraged to convert. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_REGISTER_PRIORITY (int) -A target hook which returns the register priority number to which the -register @var{hard_regno} belongs to. The bigger the number, the -more preferable the hard register usage (when all other conditions are -the same). This hook can be used to prefer some hard register over -others in LRA. For example, some x86-64 register usage needs -additional prefix which makes instructions longer. The hook can -return lower priority number for such registers make them less favorable -and as result making the generated code smaller. - -The default version of this target hook returns always zero. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_REGISTER_USAGE_LEVELING_P (void) -A target hook which returns true if we need register usage leveling. -That means if a few hard registers are equally good for the -assignment, we choose the least used hard register. The register -usage leveling may be profitable for some targets. Don't use the -usage leveling for targets with conditional execution or targets -with big register files as it hurts if-conversion and cross-jumping -optimizations. - -The default version of this target hook returns always false. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_DIFFERENT_ADDR_DISPLACEMENT_P (void) -A target hook which returns true if an address with the same structure -can have different maximal legitimate displacement. For example, the -displacement can depend on memory mode or on operand combinations in -the insn. - -The default version of this target hook returns always false. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CANNOT_SUBSTITUTE_MEM_EQUIV_P (rtx @var{subst}) -A target hook which returns @code{true} if @var{subst} can't -substitute safely pseudos with equivalent memory values during -register allocation. -The default version of this target hook returns @code{false}. -On most machines, this default should be used. For generally -machines with non orthogonal register usage for addressing, such -as SH, this hook can be used to avoid excessive spilling. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_LEGITIMIZE_ADDRESS_DISPLACEMENT (rtx *@var{offset1}, rtx *@var{offset2}, poly_int64 @var{orig_offset}, machine_mode @var{mode}) -This hook tries to split address offset @var{orig_offset} into -two parts: one that should be added to the base address to create -a local anchor point, and an additional offset that can be applied -to the anchor to address a value of mode @var{mode}. The idea is that -the local anchor could be shared by other accesses to nearby locations. - -The hook returns true if it succeeds, storing the offset of the -anchor from the base in @var{offset1} and the offset of the final address -from the anchor in @var{offset2}. The default implementation returns false. -@end deftypefn - -@deftypefn {Target Hook} reg_class_t TARGET_SPILL_CLASS (reg_class_t, @var{machine_mode}) -This hook defines a class of registers which could be used for spilling -pseudos of the given mode and class, or @code{NO_REGS} if only memory -should be used. Not defining this hook is equivalent to returning -@code{NO_REGS} for all inputs. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ADDITIONAL_ALLOCNO_CLASS_P (reg_class_t) -This hook should return @code{true} if given class of registers should -be an allocno class in any way. Usually RA uses only one register -class from all classes containing the same register set. In some -complicated cases, you need to have two or more such classes as -allocno ones for RA correct work. Not defining this hook is -equivalent to returning @code{false} for all inputs. -@end deftypefn - -@deftypefn {Target Hook} scalar_int_mode TARGET_CSTORE_MODE (enum insn_code @var{icode}) -This hook defines the machine mode to use for the boolean result of -conditional store patterns. The ICODE argument is the instruction code -for the cstore being performed. Not definiting this hook is the same -as accepting the mode encoded into operand 0 of the cstore expander -patterns. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_COMPUTE_PRESSURE_CLASSES (enum reg_class *@var{pressure_classes}) -A target hook which lets a backend compute the set of pressure classes to -be used by those optimization passes which take register pressure into -account, as opposed to letting IRA compute them. It returns the number of -register classes stored in the array @var{pressure_classes}. -@end deftypefn - -@node Stack and Calling -@section Stack Layout and Calling Conventions -@cindex calling conventions - -@c prevent bad page break with this line -This describes the stack layout and calling conventions. - -@menu -* Frame Layout:: -* Exception Handling:: -* Stack Checking:: -* Frame Registers:: -* Elimination:: -* Stack Arguments:: -* Register Arguments:: -* Scalar Return:: -* Aggregate Return:: -* Caller Saves:: -* Function Entry:: -* Profiling:: -* Tail Calls:: -* Shrink-wrapping separate components:: -* Stack Smashing Protection:: -* Miscellaneous Register Hooks:: -@end menu - -@node Frame Layout -@subsection Basic Stack Layout -@cindex stack frame layout -@cindex frame layout - -@c prevent bad page break with this line -Here is the basic stack layout. - -@defmac STACK_GROWS_DOWNWARD -Define this macro to be true if pushing a word onto the stack moves the stack -pointer to a smaller address, and false otherwise. -@end defmac - -@defmac STACK_PUSH_CODE -This macro defines the operation used when something is pushed -on the stack. In RTL, a push operation will be -@code{(set (mem (STACK_PUSH_CODE (reg sp))) @dots{})} - -The choices are @code{PRE_DEC}, @code{POST_DEC}, @code{PRE_INC}, -and @code{POST_INC}. Which of these is correct depends on -the stack direction and on whether the stack pointer points -to the last item on the stack or whether it points to the -space for the next item on the stack. - -The default is @code{PRE_DEC} when @code{STACK_GROWS_DOWNWARD} is -true, which is almost always right, and @code{PRE_INC} otherwise, -which is often wrong. -@end defmac - -@defmac FRAME_GROWS_DOWNWARD -Define this macro to nonzero value if the addresses of local variable slots -are at negative offsets from the frame pointer. -@end defmac - -@defmac ARGS_GROW_DOWNWARD -Define this macro if successive arguments to a function occupy decreasing -addresses on the stack. -@end defmac - -@deftypefn {Target Hook} HOST_WIDE_INT TARGET_STARTING_FRAME_OFFSET (void) -This hook returns the offset from the frame pointer to the first local -variable slot to be allocated. If @code{FRAME_GROWS_DOWNWARD}, it is the -offset to @emph{end} of the first slot allocated, otherwise it is the -offset to @emph{beginning} of the first slot allocated. The default -implementation returns 0. -@end deftypefn - -@defmac STACK_ALIGNMENT_NEEDED -Define to zero to disable final alignment of the stack during reload. -The nonzero default for this macro is suitable for most ports. - -On ports where @code{TARGET_STARTING_FRAME_OFFSET} is nonzero or where there -is a register save block following the local block that doesn't require -alignment to @code{STACK_BOUNDARY}, it may be beneficial to disable -stack alignment and do it in the backend. -@end defmac - -@defmac STACK_POINTER_OFFSET -Offset from the stack pointer register to the first location at which -outgoing arguments are placed. If not specified, the default value of -zero is used. This is the proper value for most machines. - -If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above -the first location at which outgoing arguments are placed. -@end defmac - -@defmac FIRST_PARM_OFFSET (@var{fundecl}) -Offset from the argument pointer register to the first argument's -address. On some machines it may depend on the data type of the -function. - -If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above -the first argument's address. -@end defmac - -@defmac STACK_DYNAMIC_OFFSET (@var{fundecl}) -Offset from the stack pointer register to an item dynamically allocated -on the stack, e.g., by @code{alloca}. - -The default value for this macro is @code{STACK_POINTER_OFFSET} plus the -length of the outgoing arguments. The default is correct for most -machines. See @file{function.cc} for details. -@end defmac - -@defmac INITIAL_FRAME_ADDRESS_RTX -A C expression whose value is RTL representing the address of the initial -stack frame. This address is passed to @code{RETURN_ADDR_RTX} and -@code{DYNAMIC_CHAIN_ADDRESS}. If you don't define this macro, a reasonable -default value will be used. Define this macro in order to make frame pointer -elimination work in the presence of @code{__builtin_frame_address (count)} and -@code{__builtin_return_address (count)} for @code{count} not equal to zero. -@end defmac - -@defmac DYNAMIC_CHAIN_ADDRESS (@var{frameaddr}) -A C expression whose value is RTL representing the address in a stack -frame where the pointer to the caller's frame is stored. Assume that -@var{frameaddr} is an RTL expression for the address of the stack frame -itself. - -If you don't define this macro, the default is to return the value -of @var{frameaddr}---that is, the stack frame address is also the -address of the stack word that points to the previous frame. -@end defmac - -@defmac SETUP_FRAME_ADDRESSES -A C expression that produces the machine-specific code to -setup the stack so that arbitrary frames can be accessed. For example, -on the SPARC, we must flush all of the register windows to the stack -before we can access arbitrary stack frames. You will seldom need to -define this macro. The default is to do nothing. -@end defmac - -@deftypefn {Target Hook} rtx TARGET_BUILTIN_SETJMP_FRAME_VALUE (void) -This target hook should return an rtx that is used to store -the address of the current frame into the built in @code{setjmp} buffer. -The default value, @code{virtual_stack_vars_rtx}, is correct for most -machines. One reason you may need to define this target hook is if -@code{hard_frame_pointer_rtx} is the appropriate value on your machine. -@end deftypefn - -@defmac FRAME_ADDR_RTX (@var{frameaddr}) -A C expression whose value is RTL representing the value of the frame -address for the current frame. @var{frameaddr} is the frame pointer -of the current frame. This is used for __builtin_frame_address. -You need only define this macro if the frame address is not the same -as the frame pointer. Most machines do not need to define it. -@end defmac - -@defmac RETURN_ADDR_RTX (@var{count}, @var{frameaddr}) -A C expression whose value is RTL representing the value of the return -address for the frame @var{count} steps up from the current frame, after -the prologue. @var{frameaddr} is the frame pointer of the @var{count} -frame, or the frame pointer of the @var{count} @minus{} 1 frame if -@code{RETURN_ADDR_IN_PREVIOUS_FRAME} is nonzero. - -The value of the expression must always be the correct address when -@var{count} is zero, but may be @code{NULL_RTX} if there is no way to -determine the return address of other frames. -@end defmac - -@defmac RETURN_ADDR_IN_PREVIOUS_FRAME -Define this macro to nonzero value if the return address of a particular -stack frame is accessed from the frame pointer of the previous stack -frame. The zero default for this macro is suitable for most ports. -@end defmac - -@defmac INCOMING_RETURN_ADDR_RTX -A C expression whose value is RTL representing the location of the -incoming return address at the beginning of any function, before the -prologue. This RTL is either a @code{REG}, indicating that the return -value is saved in @samp{REG}, or a @code{MEM} representing a location in -the stack. - -You only need to define this macro if you want to support call frame -debugging information like that provided by DWARF 2. - -If this RTL is a @code{REG}, you should also define -@code{DWARF_FRAME_RETURN_COLUMN} to @code{DWARF_FRAME_REGNUM (REGNO)}. -@end defmac - -@defmac DWARF_ALT_FRAME_RETURN_COLUMN -A C expression whose value is an integer giving a DWARF 2 column -number that may be used as an alternative return column. The column -must not correspond to any gcc hard register (that is, it must not -be in the range of @code{DWARF_FRAME_REGNUM}). - -This macro can be useful if @code{DWARF_FRAME_RETURN_COLUMN} is set to a -general register, but an alternative column needs to be used for signal -frames. Some targets have also used different frame return columns -over time. -@end defmac - -@defmac DWARF_ZERO_REG -A C expression whose value is an integer giving a DWARF 2 register -number that is considered to always have the value zero. This should -only be defined if the target has an architected zero register, and -someone decided it was a good idea to use that register number to -terminate the stack backtrace. New ports should avoid this. -@end defmac - -@defmac DWARF_VERSION_DEFAULT -A C expression whose value is the default dwarf standard version we'll honor -and advertise when generating dwarf debug information, in absence of -an explicit @option{-gdwarf-@var{version}} option on the command line. -@end defmac - -@deftypefn {Target Hook} void TARGET_DWARF_HANDLE_FRAME_UNSPEC (const char *@var{label}, rtx @var{pattern}, int @var{index}) -This target hook allows the backend to emit frame-related insns that -contain UNSPECs or UNSPEC_VOLATILEs. The DWARF 2 call frame debugging -info engine will invoke it on insns of the form -@smallexample -(set (reg) (unspec [@dots{}] UNSPEC_INDEX)) -@end smallexample -and -@smallexample -(set (reg) (unspec_volatile [@dots{}] UNSPECV_INDEX)). -@end smallexample -to let the backend emit the call frame instructions. @var{label} is -the CFI label attached to the insn, @var{pattern} is the pattern of -the insn and @var{index} is @code{UNSPEC_INDEX} or @code{UNSPECV_INDEX}. -@end deftypefn - -@deftypefn {Target Hook} {unsigned int} TARGET_DWARF_POLY_INDETERMINATE_VALUE (unsigned int @var{i}, unsigned int *@var{factor}, int *@var{offset}) -Express the value of @code{poly_int} indeterminate @var{i} as a DWARF -expression, with @var{i} counting from 1. Return the number of a DWARF -register @var{R} and set @samp{*@var{factor}} and @samp{*@var{offset}} such -that the value of the indeterminate is: -@smallexample -value_of(@var{R}) / @var{factor} - @var{offset} -@end smallexample - -A target only needs to define this hook if it sets -@samp{NUM_POLY_INT_COEFFS} to a value greater than 1. -@end deftypefn - -@defmac INCOMING_FRAME_SP_OFFSET -A C expression whose value is an integer giving the offset, in bytes, -from the value of the stack pointer register to the top of the stack -frame at the beginning of any function, before the prologue. The top of -the frame is defined to be the value of the stack pointer in the -previous frame, just before the call instruction. - -You only need to define this macro if you want to support call frame -debugging information like that provided by DWARF 2. -@end defmac - -@defmac DEFAULT_INCOMING_FRAME_SP_OFFSET -Like @code{INCOMING_FRAME_SP_OFFSET}, but must be the same for all -functions of the same ABI, and when using GAS @code{.cfi_*} directives -must also agree with the default CFI GAS emits. Define this macro -only if @code{INCOMING_FRAME_SP_OFFSET} can have different values -between different functions of the same ABI or when -@code{INCOMING_FRAME_SP_OFFSET} does not agree with GAS default CFI. -@end defmac - -@defmac ARG_POINTER_CFA_OFFSET (@var{fundecl}) -A C expression whose value is an integer giving the offset, in bytes, -from the argument pointer to the canonical frame address (cfa). The -final value should coincide with that calculated by -@code{INCOMING_FRAME_SP_OFFSET}. Which is unfortunately not usable -during virtual register instantiation. - -The default value for this macro is -@code{FIRST_PARM_OFFSET (fundecl) + crtl->args.pretend_args_size}, -which is correct for most machines; in general, the arguments are found -immediately before the stack frame. Note that this is not the case on -some targets that save registers into the caller's frame, such as SPARC -and rs6000, and so such targets need to define this macro. - -You only need to define this macro if the default is incorrect, and you -want to support call frame debugging information like that provided by -DWARF 2. -@end defmac - -@defmac FRAME_POINTER_CFA_OFFSET (@var{fundecl}) -If defined, a C expression whose value is an integer giving the offset -in bytes from the frame pointer to the canonical frame address (cfa). -The final value should coincide with that calculated by -@code{INCOMING_FRAME_SP_OFFSET}. - -Normally the CFA is calculated as an offset from the argument pointer, -via @code{ARG_POINTER_CFA_OFFSET}, but if the argument pointer is -variable due to the ABI, this may not be possible. If this macro is -defined, it implies that the virtual register instantiation should be -based on the frame pointer instead of the argument pointer. Only one -of @code{FRAME_POINTER_CFA_OFFSET} and @code{ARG_POINTER_CFA_OFFSET} -should be defined. -@end defmac - -@defmac CFA_FRAME_BASE_OFFSET (@var{fundecl}) -If defined, a C expression whose value is an integer giving the offset -in bytes from the canonical frame address (cfa) to the frame base used -in DWARF 2 debug information. The default is zero. A different value -may reduce the size of debug information on some ports. -@end defmac - -@node Exception Handling -@subsection Exception Handling Support -@cindex exception handling - -@defmac EH_RETURN_DATA_REGNO (@var{N}) -A C expression whose value is the @var{N}th register number used for -data by exception handlers, or @code{INVALID_REGNUM} if fewer than -@var{N} registers are usable. - -The exception handling library routines communicate with the exception -handlers via a set of agreed upon registers. Ideally these registers -should be call-clobbered; it is possible to use call-saved registers, -but may negatively impact code size. The target must support at least -2 data registers, but should define 4 if there are enough free registers. - -You must define this macro if you want to support call frame exception -handling like that provided by DWARF 2. -@end defmac - -@defmac EH_RETURN_STACKADJ_RTX -A C expression whose value is RTL representing a location in which -to store a stack adjustment to be applied before function return. -This is used to unwind the stack to an exception handler's call frame. -It will be assigned zero on code paths that return normally. - -Typically this is a call-clobbered hard register that is otherwise -untouched by the epilogue, but could also be a stack slot. - -Do not define this macro if the stack pointer is saved and restored -by the regular prolog and epilog code in the call frame itself; in -this case, the exception handling library routines will update the -stack location to be restored in place. Otherwise, you must define -this macro if you want to support call frame exception handling like -that provided by DWARF 2. -@end defmac - -@defmac EH_RETURN_HANDLER_RTX -A C expression whose value is RTL representing a location in which -to store the address of an exception handler to which we should -return. It will not be assigned on code paths that return normally. - -Typically this is the location in the call frame at which the normal -return address is stored. For targets that return by popping an -address off the stack, this might be a memory address just below -the @emph{target} call frame rather than inside the current call -frame. If defined, @code{EH_RETURN_STACKADJ_RTX} will have already -been assigned, so it may be used to calculate the location of the -target call frame. - -Some targets have more complex requirements than storing to an -address calculable during initial code generation. In that case -the @code{eh_return} instruction pattern should be used instead. - -If you want to support call frame exception handling, you must -define either this macro or the @code{eh_return} instruction pattern. -@end defmac - -@defmac RETURN_ADDR_OFFSET -If defined, an integer-valued C expression for which rtl will be generated -to add it to the exception handler address before it is searched in the -exception handling tables, and to subtract it again from the address before -using it to return to the exception handler. -@end defmac - -@defmac ASM_PREFERRED_EH_DATA_FORMAT (@var{code}, @var{global}) -This macro chooses the encoding of pointers embedded in the exception -handling sections. If at all possible, this should be defined such -that the exception handling section will not require dynamic relocations, -and so may be read-only. - -@var{code} is 0 for data, 1 for code labels, 2 for function pointers. -@var{global} is true if the symbol may be affected by dynamic relocations. -The macro should return a combination of the @code{DW_EH_PE_*} defines -as found in @file{dwarf2.h}. - -If this macro is not defined, pointers will not be encoded but -represented directly. -@end defmac - -@defmac ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX (@var{file}, @var{encoding}, @var{size}, @var{addr}, @var{done}) -This macro allows the target to emit whatever special magic is required -to represent the encoding chosen by @code{ASM_PREFERRED_EH_DATA_FORMAT}. -Generic code takes care of pc-relative and indirect encodings; this must -be defined if the target uses text-relative or data-relative encodings. - -This is a C statement that branches to @var{done} if the format was -handled. @var{encoding} is the format chosen, @var{size} is the number -of bytes that the format occupies, @var{addr} is the @code{SYMBOL_REF} -to be emitted. -@end defmac - -@defmac MD_FALLBACK_FRAME_STATE_FOR (@var{context}, @var{fs}) -This macro allows the target to add CPU and operating system specific -code to the call-frame unwinder for use when there is no unwind data -available. The most common reason to implement this macro is to unwind -through signal frames. - -This macro is called from @code{uw_frame_state_for} in -@file{unwind-dw2.c}, @file{unwind-dw2-xtensa.c} and -@file{unwind-ia64.c}. @var{context} is an @code{_Unwind_Context}; -@var{fs} is an @code{_Unwind_FrameState}. Examine @code{context->ra} -for the address of the code being executed and @code{context->cfa} for -the stack pointer value. If the frame can be decoded, the register -save addresses should be updated in @var{fs} and the macro should -evaluate to @code{_URC_NO_REASON}. If the frame cannot be decoded, -the macro should evaluate to @code{_URC_END_OF_STACK}. - -For proper signal handling in Java this macro is accompanied by -@code{MAKE_THROW_FRAME}, defined in @file{libjava/include/*-signal.h} headers. -@end defmac - -@defmac MD_HANDLE_UNWABI (@var{context}, @var{fs}) -This macro allows the target to add operating system specific code to the -call-frame unwinder to handle the IA-64 @code{.unwabi} unwinding directive, -usually used for signal or interrupt frames. - -This macro is called from @code{uw_update_context} in libgcc's -@file{unwind-ia64.c}. @var{context} is an @code{_Unwind_Context}; -@var{fs} is an @code{_Unwind_FrameState}. Examine @code{fs->unwabi} -for the abi and context in the @code{.unwabi} directive. If the -@code{.unwabi} directive can be handled, the register save addresses should -be updated in @var{fs}. -@end defmac - -@defmac TARGET_USES_WEAK_UNWIND_INFO -A C expression that evaluates to true if the target requires unwind -info to be given comdat linkage. Define it to be @code{1} if comdat -linkage is necessary. The default is @code{0}. -@end defmac - -@node Stack Checking -@subsection Specifying How Stack Checking is Done - -GCC will check that stack references are within the boundaries of the -stack, if the option @option{-fstack-check} is specified, in one of -three ways: - -@enumerate -@item -If the value of the @code{STACK_CHECK_BUILTIN} macro is nonzero, GCC -will assume that you have arranged for full stack checking to be done -at appropriate places in the configuration files. GCC will not do -other special processing. - -@item -If @code{STACK_CHECK_BUILTIN} is zero and the value of the -@code{STACK_CHECK_STATIC_BUILTIN} macro is nonzero, GCC will assume -that you have arranged for static stack checking (checking of the -static stack frame of functions) to be done at appropriate places -in the configuration files. GCC will only emit code to do dynamic -stack checking (checking on dynamic stack allocations) using the third -approach below. - -@item -If neither of the above are true, GCC will generate code to periodically -``probe'' the stack pointer using the values of the macros defined below. -@end enumerate - -If neither STACK_CHECK_BUILTIN nor STACK_CHECK_STATIC_BUILTIN is defined, -GCC will change its allocation strategy for large objects if the option -@option{-fstack-check} is specified: they will always be allocated -dynamically if their size exceeds @code{STACK_CHECK_MAX_VAR_SIZE} bytes. - -@defmac STACK_CHECK_BUILTIN -A nonzero value if stack checking is done by the configuration files in a -machine-dependent manner. You should define this macro if stack checking -is required by the ABI of your machine or if you would like to do stack -checking in some more efficient way than the generic approach. The default -value of this macro is zero. -@end defmac - -@defmac STACK_CHECK_STATIC_BUILTIN -A nonzero value if static stack checking is done by the configuration files -in a machine-dependent manner. You should define this macro if you would -like to do static stack checking in some more efficient way than the generic -approach. The default value of this macro is zero. -@end defmac - -@defmac STACK_CHECK_PROBE_INTERVAL_EXP -An integer specifying the interval at which GCC must generate stack probe -instructions, defined as 2 raised to this integer. You will normally -define this macro so that the interval be no larger than the size of -the ``guard pages'' at the end of a stack area. The default value -of 12 (4096-byte interval) is suitable for most systems. -@end defmac - -@defmac STACK_CHECK_MOVING_SP -An integer which is nonzero if GCC should move the stack pointer page by page -when doing probes. This can be necessary on systems where the stack pointer -contains the bottom address of the memory area accessible to the executing -thread at any point in time. In this situation an alternate signal stack -is required in order to be able to recover from a stack overflow. The -default value of this macro is zero. -@end defmac - -@defmac STACK_CHECK_PROTECT -The number of bytes of stack needed to recover from a stack overflow, for -languages where such a recovery is supported. The default value of 4KB/8KB -with the @code{setjmp}/@code{longjmp}-based exception handling mechanism and -8KB/12KB with other exception handling mechanisms should be adequate for most -architectures and operating systems. -@end defmac - -The following macros are relevant only if neither STACK_CHECK_BUILTIN -nor STACK_CHECK_STATIC_BUILTIN is defined; you can omit them altogether -in the opposite case. - -@defmac STACK_CHECK_MAX_FRAME_SIZE -The maximum size of a stack frame, in bytes. GCC will generate probe -instructions in non-leaf functions to ensure at least this many bytes of -stack are available. If a stack frame is larger than this size, stack -checking will not be reliable and GCC will issue a warning. The -default is chosen so that GCC only generates one instruction on most -systems. You should normally not change the default value of this macro. -@end defmac - -@defmac STACK_CHECK_FIXED_FRAME_SIZE -GCC uses this value to generate the above warning message. It -represents the amount of fixed frame used by a function, not including -space for any callee-saved registers, temporaries and user variables. -You need only specify an upper bound for this amount and will normally -use the default of four words. -@end defmac - -@defmac STACK_CHECK_MAX_VAR_SIZE -The maximum size, in bytes, of an object that GCC will place in the -fixed area of the stack frame when the user specifies -@option{-fstack-check}. -GCC computed the default from the values of the above macros and you will -normally not need to override that default. -@end defmac - -@deftypefn {Target Hook} HOST_WIDE_INT TARGET_STACK_CLASH_PROTECTION_ALLOCA_PROBE_RANGE (void) -Some targets have an ABI defined interval for which no probing needs to be done. -When a probe does need to be done this same interval is used as the probe distance -up when doing stack clash protection for alloca. -On such targets this value can be set to override the default probing up interval. -Define this variable to return nonzero if such a probe range is required or zero otherwise. -Defining this hook also requires your functions which make use of alloca to have at least 8 byes -of outgoing arguments. If this is not the case the stack will be corrupted. -You need not define this macro if it would always have the value zero. -@end deftypefn - -@need 2000 -@node Frame Registers -@subsection Registers That Address the Stack Frame - -@c prevent bad page break with this line -This discusses registers that address the stack frame. - -@defmac STACK_POINTER_REGNUM -The register number of the stack pointer register, which must also be a -fixed register according to @code{FIXED_REGISTERS}. On most machines, -the hardware determines which register this is. -@end defmac - -@defmac FRAME_POINTER_REGNUM -The register number of the frame pointer register, which is used to -access automatic variables in the stack frame. On some machines, the -hardware determines which register this is. On other machines, you can -choose any register you wish for this purpose. -@end defmac - -@defmac HARD_FRAME_POINTER_REGNUM -On some machines the offset between the frame pointer and starting -offset of the automatic variables is not known until after register -allocation has been done (for example, because the saved registers are -between these two locations). On those machines, define -@code{FRAME_POINTER_REGNUM} the number of a special, fixed register to -be used internally until the offset is known, and define -@code{HARD_FRAME_POINTER_REGNUM} to be the actual hard register number -used for the frame pointer. - -You should define this macro only in the very rare circumstances when it -is not possible to calculate the offset between the frame pointer and -the automatic variables until after register allocation has been -completed. When this macro is defined, you must also indicate in your -definition of @code{ELIMINABLE_REGS} how to eliminate -@code{FRAME_POINTER_REGNUM} into either @code{HARD_FRAME_POINTER_REGNUM} -or @code{STACK_POINTER_REGNUM}. - -Do not define this macro if it would be the same as -@code{FRAME_POINTER_REGNUM}. -@end defmac - -@defmac ARG_POINTER_REGNUM -The register number of the arg pointer register, which is used to access -the function's argument list. On some machines, this is the same as the -frame pointer register. On some machines, the hardware determines which -register this is. On other machines, you can choose any register you -wish for this purpose. If this is not the same register as the frame -pointer register, then you must mark it as a fixed register according to -@code{FIXED_REGISTERS}, or arrange to be able to eliminate it -(@pxref{Elimination}). -@end defmac - -@defmac HARD_FRAME_POINTER_IS_FRAME_POINTER -Define this to a preprocessor constant that is nonzero if -@code{hard_frame_pointer_rtx} and @code{frame_pointer_rtx} should be -the same. The default definition is @samp{(HARD_FRAME_POINTER_REGNUM -== FRAME_POINTER_REGNUM)}; you only need to define this macro if that -definition is not suitable for use in preprocessor conditionals. -@end defmac - -@defmac HARD_FRAME_POINTER_IS_ARG_POINTER -Define this to a preprocessor constant that is nonzero if -@code{hard_frame_pointer_rtx} and @code{arg_pointer_rtx} should be the -same. The default definition is @samp{(HARD_FRAME_POINTER_REGNUM == -ARG_POINTER_REGNUM)}; you only need to define this macro if that -definition is not suitable for use in preprocessor conditionals. -@end defmac - -@defmac RETURN_ADDRESS_POINTER_REGNUM -The register number of the return address pointer register, which is used to -access the current function's return address from the stack. On some -machines, the return address is not at a fixed offset from the frame -pointer or stack pointer or argument pointer. This register can be defined -to point to the return address on the stack, and then be converted by -@code{ELIMINABLE_REGS} into either the frame pointer or stack pointer. - -Do not define this macro unless there is no other way to get the return -address from the stack. -@end defmac - -@defmac STATIC_CHAIN_REGNUM -@defmacx STATIC_CHAIN_INCOMING_REGNUM -Register numbers used for passing a function's static chain pointer. If -register windows are used, the register number as seen by the called -function is @code{STATIC_CHAIN_INCOMING_REGNUM}, while the register -number as seen by the calling function is @code{STATIC_CHAIN_REGNUM}. If -these registers are the same, @code{STATIC_CHAIN_INCOMING_REGNUM} need -not be defined. - -The static chain register need not be a fixed register. - -If the static chain is passed in memory, these macros should not be -defined; instead, the @code{TARGET_STATIC_CHAIN} hook should be used. -@end defmac - -@deftypefn {Target Hook} rtx TARGET_STATIC_CHAIN (const_tree @var{fndecl_or_type}, bool @var{incoming_p}) -This hook replaces the use of @code{STATIC_CHAIN_REGNUM} et al for -targets that may use different static chain locations for different -nested functions. This may be required if the target has function -attributes that affect the calling conventions of the function and -those calling conventions use different static chain locations. - -The default version of this hook uses @code{STATIC_CHAIN_REGNUM} et al. - -If the static chain is passed in memory, this hook should be used to -provide rtx giving @code{mem} expressions that denote where they are stored. -Often the @code{mem} expression as seen by the caller will be at an offset -from the stack pointer and the @code{mem} expression as seen by the callee -will be at an offset from the frame pointer. -@findex stack_pointer_rtx -@findex frame_pointer_rtx -@findex arg_pointer_rtx -The variables @code{stack_pointer_rtx}, @code{frame_pointer_rtx}, and -@code{arg_pointer_rtx} will have been initialized and should be used -to refer to those items. -@end deftypefn - -@defmac DWARF_FRAME_REGISTERS -This macro specifies the maximum number of hard registers that can be -saved in a call frame. This is used to size data structures used in -DWARF2 exception handling. - -Prior to GCC 3.0, this macro was needed in order to establish a stable -exception handling ABI in the face of adding new hard registers for ISA -extensions. In GCC 3.0 and later, the EH ABI is insulated from changes -in the number of hard registers. Nevertheless, this macro can still be -used to reduce the runtime memory requirements of the exception handling -routines, which can be substantial if the ISA contains a lot of -registers that are not call-saved. - -If this macro is not defined, it defaults to -@code{FIRST_PSEUDO_REGISTER}. -@end defmac - -@defmac PRE_GCC3_DWARF_FRAME_REGISTERS - -This macro is similar to @code{DWARF_FRAME_REGISTERS}, but is provided -for backward compatibility in pre GCC 3.0 compiled code. - -If this macro is not defined, it defaults to -@code{DWARF_FRAME_REGISTERS}. -@end defmac - -@defmac DWARF_REG_TO_UNWIND_COLUMN (@var{regno}) - -Define this macro if the target's representation for dwarf registers -is different than the internal representation for unwind column. -Given a dwarf register, this macro should return the internal unwind -column number to use instead. -@end defmac - -@defmac DWARF_FRAME_REGNUM (@var{regno}) - -Define this macro if the target's representation for dwarf registers -used in .eh_frame or .debug_frame is different from that used in other -debug info sections. Given a GCC hard register number, this macro -should return the .eh_frame register number. The default is -@code{DEBUGGER_REGNO (@var{regno})}. - -@end defmac - -@defmac DWARF2_FRAME_REG_OUT (@var{regno}, @var{for_eh}) - -Define this macro to map register numbers held in the call frame info -that GCC has collected using @code{DWARF_FRAME_REGNUM} to those that -should be output in .debug_frame (@code{@var{for_eh}} is zero) and -.eh_frame (@code{@var{for_eh}} is nonzero). The default is to -return @code{@var{regno}}. - -@end defmac - -@defmac REG_VALUE_IN_UNWIND_CONTEXT - -Define this macro if the target stores register values as -@code{_Unwind_Word} type in unwind context. It should be defined if -target register size is larger than the size of @code{void *}. The -default is to store register values as @code{void *} type. - -@end defmac - -@defmac ASSUME_EXTENDED_UNWIND_CONTEXT - -Define this macro to be 1 if the target always uses extended unwind -context with version, args_size and by_value fields. If it is undefined, -it will be defined to 1 when @code{REG_VALUE_IN_UNWIND_CONTEXT} is -defined and 0 otherwise. - -@end defmac - -@defmac DWARF_LAZY_REGISTER_VALUE (@var{regno}, @var{value}) -Define this macro if the target has pseudo DWARF registers whose -values need to be computed lazily on demand by the unwinder (such as when -referenced in a CFA expression). The macro returns true if @var{regno} -is such a register and stores its value in @samp{*@var{value}} if so. -@end defmac - -@node Elimination -@subsection Eliminating Frame Pointer and Arg Pointer - -@c prevent bad page break with this line -This is about eliminating the frame pointer and arg pointer. - -@deftypefn {Target Hook} bool TARGET_FRAME_POINTER_REQUIRED (void) -This target hook should return @code{true} if a function must have and use -a frame pointer. This target hook is called in the reload pass. If its return -value is @code{true} the function will have a frame pointer. - -This target hook can in principle examine the current function and decide -according to the facts, but on most machines the constant @code{false} or the -constant @code{true} suffices. Use @code{false} when the machine allows code -to be generated with no frame pointer, and doing so saves some time or space. -Use @code{true} when there is no possible advantage to avoiding a frame -pointer. - -In certain cases, the compiler does not know how to produce valid code -without a frame pointer. The compiler recognizes those cases and -automatically gives the function a frame pointer regardless of what -@code{targetm.frame_pointer_required} returns. You don't need to worry about -them. - -In a function that does not require a frame pointer, the frame pointer -register can be allocated for ordinary usage, unless you mark it as a -fixed register. See @code{FIXED_REGISTERS} for more information. - -Default return value is @code{false}. -@end deftypefn - -@defmac ELIMINABLE_REGS -This macro specifies a table of register pairs used to eliminate -unneeded registers that point into the stack frame. - -The definition of this macro is a list of structure initializations, each -of which specifies an original and replacement register. - -On some machines, the position of the argument pointer is not known until -the compilation is completed. In such a case, a separate hard register -must be used for the argument pointer. This register can be eliminated by -replacing it with either the frame pointer or the argument pointer, -depending on whether or not the frame pointer has been eliminated. - -In this case, you might specify: -@smallexample -#define ELIMINABLE_REGS \ -@{@{ARG_POINTER_REGNUM, STACK_POINTER_REGNUM@}, \ - @{ARG_POINTER_REGNUM, FRAME_POINTER_REGNUM@}, \ - @{FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM@}@} -@end smallexample - -Note that the elimination of the argument pointer with the stack pointer is -specified first since that is the preferred elimination. -@end defmac - -@deftypefn {Target Hook} bool TARGET_CAN_ELIMINATE (const int @var{from_reg}, const int @var{to_reg}) -This target hook should return @code{true} if the compiler is allowed to -try to replace register number @var{from_reg} with register number -@var{to_reg}. This target hook will usually be @code{true}, since most of the -cases preventing register elimination are things that the compiler already -knows about. - -Default return value is @code{true}. -@end deftypefn - -@defmac INITIAL_ELIMINATION_OFFSET (@var{from-reg}, @var{to-reg}, @var{offset-var}) -This macro returns the initial difference between the specified pair -of registers. The value would be computed from information -such as the result of @code{get_frame_size ()} and the tables of -registers @code{df_regs_ever_live_p} and @code{call_used_regs}. -@end defmac - -@deftypefn {Target Hook} void TARGET_COMPUTE_FRAME_LAYOUT (void) -This target hook is called once each time the frame layout needs to be -recalculated. The calculations can be cached by the target and can then -be used by @code{INITIAL_ELIMINATION_OFFSET} instead of re-computing the -layout on every invocation of that hook. This is particularly useful -for targets that have an expensive frame layout function. Implementing -this callback is optional. -@end deftypefn - -@node Stack Arguments -@subsection Passing Function Arguments on the Stack -@cindex arguments on stack -@cindex stack arguments - -The macros in this section control how arguments are passed -on the stack. See the following section for other macros that -control passing certain arguments in registers. - -@deftypefn {Target Hook} bool TARGET_PROMOTE_PROTOTYPES (const_tree @var{fntype}) -This target hook returns @code{true} if an argument declared in a -prototype as an integral type smaller than @code{int} should actually be -passed as an @code{int}. In addition to avoiding errors in certain -cases of mismatch, it also makes for better code on certain machines. -The default is to not promote prototypes. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_PUSH_ARGUMENT (unsigned int @var{npush}) -This target hook returns @code{true} if push instructions will be -used to pass outgoing arguments. When the push instruction usage is -optional, @var{npush} is nonzero to indicate the number of bytes to -push. Otherwise, @var{npush} is zero. If the target machine does not -have a push instruction or push instruction should be avoided, -@code{false} should be returned. That directs GCC to use an alternate -strategy: to allocate the entire argument block and then store the -arguments into it. If this target hook may return @code{true}, -@code{PUSH_ROUNDING} must be defined. -@end deftypefn - -@defmac PUSH_ARGS_REVERSED -A C expression. If nonzero, function arguments will be evaluated from -last to first, rather than from first to last. If this macro is not -defined, it defaults to @code{PUSH_ARGS} on targets where the stack -and args grow in opposite directions, and 0 otherwise. -@end defmac - -@defmac PUSH_ROUNDING (@var{npushed}) -A C expression that is the number of bytes actually pushed onto the -stack when an instruction attempts to push @var{npushed} bytes. - -On some machines, the definition - -@smallexample -#define PUSH_ROUNDING(BYTES) (BYTES) -@end smallexample - -@noindent -will suffice. But on other machines, instructions that appear -to push one byte actually push two bytes in an attempt to maintain -alignment. Then the definition should be - -@smallexample -#define PUSH_ROUNDING(BYTES) (((BYTES) + 1) & ~1) -@end smallexample - -If the value of this macro has a type, it should be an unsigned type. -@end defmac - -@findex outgoing_args_size -@findex crtl->outgoing_args_size -@defmac ACCUMULATE_OUTGOING_ARGS -A C expression. If nonzero, the maximum amount of space required for outgoing arguments -will be computed and placed into -@code{crtl->outgoing_args_size}. No space will be pushed -onto the stack for each call; instead, the function prologue should -increase the stack frame size by this amount. - -Setting both @code{PUSH_ARGS} and @code{ACCUMULATE_OUTGOING_ARGS} -is not proper. -@end defmac - -@defmac REG_PARM_STACK_SPACE (@var{fndecl}) -Define this macro if functions should assume that stack space has been -allocated for arguments even when their values are passed in -registers. - -The value of this macro is the size, in bytes, of the area reserved for -arguments passed in registers for the function represented by @var{fndecl}, -which can be zero if GCC is calling a library function. -The argument @var{fndecl} can be the FUNCTION_DECL, or the type itself -of the function. - -This space can be allocated by the caller, or be a part of the -machine-dependent stack frame: @code{OUTGOING_REG_PARM_STACK_SPACE} says -which. -@end defmac -@c above is overfull. not sure what to do. --mew 5feb93 did -@c something, not sure if it looks good. --mew 10feb93 - -@defmac INCOMING_REG_PARM_STACK_SPACE (@var{fndecl}) -Like @code{REG_PARM_STACK_SPACE}, but for incoming register arguments. -Define this macro if space guaranteed when compiling a function body -is different to space required when making a call, a situation that -can arise with K&R style function definitions. -@end defmac - -@defmac OUTGOING_REG_PARM_STACK_SPACE (@var{fntype}) -Define this to a nonzero value if it is the responsibility of the -caller to allocate the area reserved for arguments passed in registers -when calling a function of @var{fntype}. @var{fntype} may be NULL -if the function called is a library function. - -If @code{ACCUMULATE_OUTGOING_ARGS} is defined, this macro controls -whether the space for these arguments counts in the value of -@code{crtl->outgoing_args_size}. -@end defmac - -@defmac STACK_PARMS_IN_REG_PARM_AREA -Define this macro if @code{REG_PARM_STACK_SPACE} is defined, but the -stack parameters don't skip the area specified by it. -@c i changed this, makes more sens and it should have taken care of the -@c overfull.. not as specific, tho. --mew 5feb93 - -Normally, when a parameter is not passed in registers, it is placed on the -stack beyond the @code{REG_PARM_STACK_SPACE} area. Defining this macro -suppresses this behavior and causes the parameter to be passed on the -stack in its natural location. -@end defmac - -@deftypefn {Target Hook} poly_int64 TARGET_RETURN_POPS_ARGS (tree @var{fundecl}, tree @var{funtype}, poly_int64 @var{size}) -This target hook returns the number of bytes of its own arguments that -a function pops on returning, or 0 if the function pops no arguments -and the caller must therefore pop them all after the function returns. - -@var{fundecl} is a C variable whose value is a tree node that describes -the function in question. Normally it is a node of type -@code{FUNCTION_DECL} that describes the declaration of the function. -From this you can obtain the @code{DECL_ATTRIBUTES} of the function. - -@var{funtype} is a C variable whose value is a tree node that -describes the function in question. Normally it is a node of type -@code{FUNCTION_TYPE} that describes the data type of the function. -From this it is possible to obtain the data types of the value and -arguments (if known). - -When a call to a library function is being considered, @var{fundecl} -will contain an identifier node for the library function. Thus, if -you need to distinguish among various library functions, you can do so -by their names. Note that ``library function'' in this context means -a function used to perform arithmetic, whose name is known specially -in the compiler and was not mentioned in the C code being compiled. - -@var{size} is the number of bytes of arguments passed on the -stack. If a variable number of bytes is passed, it is zero, and -argument popping will always be the responsibility of the calling function. - -On the VAX, all functions always pop their arguments, so the definition -of this macro is @var{size}. On the 68000, using the standard -calling convention, no functions pop their arguments, so the value of -the macro is always 0 in this case. But an alternative calling -convention is available in which functions that take a fixed number of -arguments pop them but other functions (such as @code{printf}) pop -nothing (the caller pops all). When this convention is in use, -@var{funtype} is examined to determine whether a function takes a fixed -number of arguments. -@end deftypefn - -@defmac CALL_POPS_ARGS (@var{cum}) -A C expression that should indicate the number of bytes a call sequence -pops off the stack. It is added to the value of @code{RETURN_POPS_ARGS} -when compiling a function call. - -@var{cum} is the variable in which all arguments to the called function -have been accumulated. - -On certain architectures, such as the SH5, a call trampoline is used -that pops certain registers off the stack, depending on the arguments -that have been passed to the function. Since this is a property of the -call site, not of the called function, @code{RETURN_POPS_ARGS} is not -appropriate. -@end defmac - -@node Register Arguments -@subsection Passing Arguments in Registers -@cindex arguments in registers -@cindex registers arguments - -This section describes the macros which let you control how various -types of arguments are passed in registers or how they are arranged in -the stack. - -@deftypefn {Target Hook} rtx TARGET_FUNCTION_ARG (cumulative_args_t @var{ca}, const function_arg_info @var{&arg}) -Return an RTX indicating whether function argument @var{arg} is passed -in a register and if so, which register. Argument @var{ca} summarizes all -the previous arguments. - -The return value is usually either a @code{reg} RTX for the hard -register in which to pass the argument, or zero to pass the argument -on the stack. - -The value of the expression can also be a @code{parallel} RTX@. This is -used when an argument is passed in multiple locations. The mode of the -@code{parallel} should be the mode of the entire argument. The -@code{parallel} holds any number of @code{expr_list} pairs; each one -describes where part of the argument is passed. In each -@code{expr_list} the first operand must be a @code{reg} RTX for the hard -register in which to pass this part of the argument, and the mode of the -register RTX indicates how large this part of the argument is. The -second operand of the @code{expr_list} is a @code{const_int} which gives -the offset in bytes into the entire argument of where this part starts. -As a special exception the first @code{expr_list} in the @code{parallel} -RTX may have a first operand of zero. This indicates that the entire -argument is also stored on the stack. - -The last time this hook is called, it is called with @code{MODE == -VOIDmode}, and its result is passed to the @code{call} or @code{call_value} -pattern as operands 2 and 3 respectively. - -@cindex @file{stdarg.h} and register arguments -The usual way to make the ISO library @file{stdarg.h} work on a -machine where some arguments are usually passed in registers, is to -cause nameless arguments to be passed on the stack instead. This is -done by making @code{TARGET_FUNCTION_ARG} return 0 whenever -@var{named} is @code{false}. - -@cindex @code{TARGET_MUST_PASS_IN_STACK}, and @code{TARGET_FUNCTION_ARG} -@cindex @code{REG_PARM_STACK_SPACE}, and @code{TARGET_FUNCTION_ARG} -You may use the hook @code{targetm.calls.must_pass_in_stack} -in the definition of this macro to determine if this argument is of a -type that must be passed in the stack. If @code{REG_PARM_STACK_SPACE} -is not defined and @code{TARGET_FUNCTION_ARG} returns nonzero for such an -argument, the compiler will abort. If @code{REG_PARM_STACK_SPACE} is -defined, the argument will be computed in the stack and then loaded into -a register. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_MUST_PASS_IN_STACK (const function_arg_info @var{&arg}) -This target hook should return @code{true} if we should not pass @var{arg} -solely in registers. The file @file{expr.h} defines a -definition that is usually appropriate, refer to @file{expr.h} for additional -documentation. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_FUNCTION_INCOMING_ARG (cumulative_args_t @var{ca}, const function_arg_info @var{&arg}) -Define this hook if the caller and callee on the target have different -views of where arguments are passed. Also define this hook if there are -functions that are never directly called, but are invoked by the hardware -and which have nonstandard calling conventions. - -In this case @code{TARGET_FUNCTION_ARG} computes the register in -which the caller passes the value, and -@code{TARGET_FUNCTION_INCOMING_ARG} should be defined in a similar -fashion to tell the function being called where the arguments will -arrive. - -@code{TARGET_FUNCTION_INCOMING_ARG} can also return arbitrary address -computation using hard register, which can be forced into a register, -so that it can be used to pass special arguments. - -If @code{TARGET_FUNCTION_INCOMING_ARG} is not defined, -@code{TARGET_FUNCTION_ARG} serves both purposes. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_USE_PSEUDO_PIC_REG (void) -This hook should return 1 in case pseudo register should be created -for pic_offset_table_rtx during function expand. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_INIT_PIC_REG (void) -Perform a target dependent initialization of pic_offset_table_rtx. -This hook is called at the start of register allocation. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_ARG_PARTIAL_BYTES (cumulative_args_t @var{cum}, const function_arg_info @var{&arg}) -This target hook returns the number of bytes at the beginning of an -argument that must be put in registers. The value must be zero for -arguments that are passed entirely in registers or that are entirely -pushed on the stack. - -On some machines, certain arguments must be passed partially in -registers and partially in memory. On these machines, typically the -first few words of arguments are passed in registers, and the rest -on the stack. If a multi-word argument (a @code{double} or a -structure) crosses that boundary, its first few words must be passed -in registers and the rest must be pushed. This macro tells the -compiler when this occurs, and how many bytes should go in registers. - -@code{TARGET_FUNCTION_ARG} for these arguments should return the first -register to be used by the caller for this argument; likewise -@code{TARGET_FUNCTION_INCOMING_ARG}, for the called function. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_PASS_BY_REFERENCE (cumulative_args_t @var{cum}, const function_arg_info @var{&arg}) -This target hook should return @code{true} if argument @var{arg} at the -position indicated by @var{cum} should be passed by reference. This -predicate is queried after target independent reasons for being -passed by reference, such as @code{TREE_ADDRESSABLE (@var{arg}.type)}. - -If the hook returns true, a copy of that argument is made in memory and a -pointer to the argument is passed instead of the argument itself. -The pointer is passed in whatever way is appropriate for passing a pointer -to that type. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CALLEE_COPIES (cumulative_args_t @var{cum}, const function_arg_info @var{&arg}) -The function argument described by the parameters to this hook is -known to be passed by reference. The hook should return true if the -function argument should be copied by the callee instead of copied -by the caller. - -For any argument for which the hook returns true, if it can be -determined that the argument is not modified, then a copy need -not be generated. - -The default version of this hook always returns false. -@end deftypefn - -@defmac CUMULATIVE_ARGS -A C type for declaring a variable that is used as the first argument -of @code{TARGET_FUNCTION_ARG} and other related values. For some -target machines, the type @code{int} suffices and can hold the number -of bytes of argument so far. - -There is no need to record in @code{CUMULATIVE_ARGS} anything about the -arguments that have been passed on the stack. The compiler has other -variables to keep track of that. For target machines on which all -arguments are passed on the stack, there is no need to store anything in -@code{CUMULATIVE_ARGS}; however, the data structure must exist and -should not be empty, so use @code{int}. -@end defmac - -@defmac OVERRIDE_ABI_FORMAT (@var{fndecl}) -If defined, this macro is called before generating any code for a -function, but after the @var{cfun} descriptor for the function has been -created. The back end may use this macro to update @var{cfun} to -reflect an ABI other than that which would normally be used by default. -If the compiler is generating code for a compiler-generated function, -@var{fndecl} may be @code{NULL}. -@end defmac - -@defmac INIT_CUMULATIVE_ARGS (@var{cum}, @var{fntype}, @var{libname}, @var{fndecl}, @var{n_named_args}) -A C statement (sans semicolon) for initializing the variable -@var{cum} for the state at the beginning of the argument list. The -variable has type @code{CUMULATIVE_ARGS}. The value of @var{fntype} -is the tree node for the data type of the function which will receive -the args, or 0 if the args are to a compiler support library function. -For direct calls that are not libcalls, @var{fndecl} contain the -declaration node of the function. @var{fndecl} is also set when -@code{INIT_CUMULATIVE_ARGS} is used to find arguments for the function -being compiled. @var{n_named_args} is set to the number of named -arguments, including a structure return address if it is passed as a -parameter, when making a call. When processing incoming arguments, -@var{n_named_args} is set to @minus{}1. - -When processing a call to a compiler support library function, -@var{libname} identifies which one. It is a @code{symbol_ref} rtx which -contains the name of the function, as a string. @var{libname} is 0 when -an ordinary C function call is being processed. Thus, each time this -macro is called, either @var{libname} or @var{fntype} is nonzero, but -never both of them at once. -@end defmac - -@defmac INIT_CUMULATIVE_LIBCALL_ARGS (@var{cum}, @var{mode}, @var{libname}) -Like @code{INIT_CUMULATIVE_ARGS} but only used for outgoing libcalls, -it gets a @code{MODE} argument instead of @var{fntype}, that would be -@code{NULL}. @var{indirect} would always be zero, too. If this macro -is not defined, @code{INIT_CUMULATIVE_ARGS (cum, NULL_RTX, libname, -0)} is used instead. -@end defmac - -@defmac INIT_CUMULATIVE_INCOMING_ARGS (@var{cum}, @var{fntype}, @var{libname}) -Like @code{INIT_CUMULATIVE_ARGS} but overrides it for the purposes of -finding the arguments for the function being compiled. If this macro is -undefined, @code{INIT_CUMULATIVE_ARGS} is used instead. - -The value passed for @var{libname} is always 0, since library routines -with special calling conventions are never compiled with GCC@. The -argument @var{libname} exists for symmetry with -@code{INIT_CUMULATIVE_ARGS}. -@c could use "this macro" in place of @code{INIT_CUMULATIVE_ARGS}, maybe. -@c --mew 5feb93 i switched the order of the sentences. --mew 10feb93 -@end defmac - -@deftypefn {Target Hook} void TARGET_FUNCTION_ARG_ADVANCE (cumulative_args_t @var{ca}, const function_arg_info @var{&arg}) -This hook updates the summarizer variable pointed to by @var{ca} to -advance past argument @var{arg} in the argument list. Once this is done, -the variable @var{cum} is suitable for analyzing the @emph{following} -argument with @code{TARGET_FUNCTION_ARG}, etc. - -This hook need not do anything if the argument in question was passed -on the stack. The compiler knows how to track the amount of stack space -used for arguments without any special help. -@end deftypefn - -@deftypefn {Target Hook} HOST_WIDE_INT TARGET_FUNCTION_ARG_OFFSET (machine_mode @var{mode}, const_tree @var{type}) -This hook returns the number of bytes to add to the offset of an -argument of type @var{type} and mode @var{mode} when passed in memory. -This is needed for the SPU, which passes @code{char} and @code{short} -arguments in the preferred slot that is in the middle of the quad word -instead of starting at the top. The default implementation returns 0. -@end deftypefn - -@deftypefn {Target Hook} pad_direction TARGET_FUNCTION_ARG_PADDING (machine_mode @var{mode}, const_tree @var{type}) -This hook determines whether, and in which direction, to pad out -an argument of mode @var{mode} and type @var{type}. It returns -@code{PAD_UPWARD} to insert padding above the argument, @code{PAD_DOWNWARD} -to insert padding below the argument, or @code{PAD_NONE} to inhibit padding. - -The @emph{amount} of padding is not controlled by this hook, but by -@code{TARGET_FUNCTION_ARG_ROUND_BOUNDARY}. It is always just enough -to reach the next multiple of that boundary. - -This hook has a default definition that is right for most systems. -For little-endian machines, the default is to pad upward. For -big-endian machines, the default is to pad downward for an argument of -constant size shorter than an @code{int}, and upward otherwise. -@end deftypefn - -@defmac PAD_VARARGS_DOWN -If defined, a C expression which determines whether the default -implementation of va_arg will attempt to pad down before reading the -next argument, if that argument is smaller than its aligned space as -controlled by @code{PARM_BOUNDARY}. If this macro is not defined, all such -arguments are padded down if @code{BYTES_BIG_ENDIAN} is true. -@end defmac - -@defmac BLOCK_REG_PADDING (@var{mode}, @var{type}, @var{first}) -Specify padding for the last element of a block move between registers and -memory. @var{first} is nonzero if this is the only element. Defining this -macro allows better control of register function parameters on big-endian -machines, without using @code{PARALLEL} rtl. In particular, -@code{MUST_PASS_IN_STACK} need not test padding and mode of types in -registers, as there is no longer a "wrong" part of a register; For example, -a three byte aggregate may be passed in the high part of a register if so -required. -@end defmac - -@deftypefn {Target Hook} {unsigned int} TARGET_FUNCTION_ARG_BOUNDARY (machine_mode @var{mode}, const_tree @var{type}) -This hook returns the alignment boundary, in bits, of an argument -with the specified mode and type. The default hook returns -@code{PARM_BOUNDARY} for all arguments. -@end deftypefn - -@deftypefn {Target Hook} {unsigned int} TARGET_FUNCTION_ARG_ROUND_BOUNDARY (machine_mode @var{mode}, const_tree @var{type}) -Normally, the size of an argument is rounded up to @code{PARM_BOUNDARY}, -which is the default value for this hook. You can define this hook to -return a different value if an argument size must be rounded to a larger -value. -@end deftypefn - -@defmac FUNCTION_ARG_REGNO_P (@var{regno}) -A C expression that is nonzero if @var{regno} is the number of a hard -register in which function arguments are sometimes passed. This does -@emph{not} include implicit arguments such as the static chain and -the structure-value address. On many machines, no registers can be -used for this purpose since all function arguments are pushed on the -stack. -@end defmac - -@deftypefn {Target Hook} bool TARGET_SPLIT_COMPLEX_ARG (const_tree @var{type}) -This hook should return true if parameter of type @var{type} are passed -as two scalar parameters. By default, GCC will attempt to pack complex -arguments into the target's word size. Some ABIs require complex arguments -to be split and treated as their individual components. For example, on -AIX64, complex floats should be passed in a pair of floating point -registers, even though a complex float would fit in one 64-bit floating -point register. - -The default value of this hook is @code{NULL}, which is treated as always -false. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_BUILD_BUILTIN_VA_LIST (void) -This hook returns a type node for @code{va_list} for the target. -The default version of the hook returns @code{void*}. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_ENUM_VA_LIST_P (int @var{idx}, const char **@var{pname}, tree *@var{ptree}) -This target hook is used in function @code{c_common_nodes_and_builtins} -to iterate through the target specific builtin types for va_list. The -variable @var{idx} is used as iterator. @var{pname} has to be a pointer -to a @code{const char *} and @var{ptree} a pointer to a @code{tree} typed -variable. -The arguments @var{pname} and @var{ptree} are used to store the result of -this macro and are set to the name of the va_list builtin type and its -internal type. -If the return value of this macro is zero, then there is no more element. -Otherwise the @var{IDX} should be increased for the next call of this -macro to iterate through all types. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_FN_ABI_VA_LIST (tree @var{fndecl}) -This hook returns the va_list type of the calling convention specified by -@var{fndecl}. -The default version of this hook returns @code{va_list_type_node}. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_CANONICAL_VA_LIST_TYPE (tree @var{type}) -This hook returns the va_list type of the calling convention specified by the -type of @var{type}. If @var{type} is not a valid va_list type, it returns -@code{NULL_TREE}. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_GIMPLIFY_VA_ARG_EXPR (tree @var{valist}, tree @var{type}, gimple_seq *@var{pre_p}, gimple_seq *@var{post_p}) -This hook performs target-specific gimplification of -@code{VA_ARG_EXPR}. The first two parameters correspond to the -arguments to @code{va_arg}; the latter two are as in -@code{gimplify.cc:gimplify_expr}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_VALID_POINTER_MODE (scalar_int_mode @var{mode}) -Define this to return nonzero if the port can handle pointers -with machine mode @var{mode}. The default version of this -hook returns true for both @code{ptr_mode} and @code{Pmode}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_REF_MAY_ALIAS_ERRNO (ao_ref *@var{ref}) -Define this to return nonzero if the memory reference @var{ref} -may alias with the system C library errno location. The default -version of this hook assumes the system C library errno location -is either a declaration of type int or accessed by dereferencing -a pointer to int. -@end deftypefn - -@deftypefn {Target Hook} machine_mode TARGET_TRANSLATE_MODE_ATTRIBUTE (machine_mode @var{mode}) -Define this hook if during mode attribute processing, the port should -translate machine_mode @var{mode} to another mode. For example, rs6000's -@code{KFmode}, when it is the same as @code{TFmode}. - -The default version of the hook returns that mode that was passed in. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_SCALAR_MODE_SUPPORTED_P (scalar_mode @var{mode}) -Define this to return nonzero if the port is prepared to handle -insns involving scalar mode @var{mode}. For a scalar mode to be -considered supported, all the basic arithmetic and comparisons -must work. - -The default version of this hook returns true for any mode -required to handle the basic C types (as defined by the port). -Included here are the double-word arithmetic supported by the -code in @file{optabs.cc}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_VECTOR_MODE_SUPPORTED_P (machine_mode @var{mode}) -Define this to return nonzero if the port is prepared to handle -insns involving vector mode @var{mode}. At the very least, it -must have move patterns for this mode. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_COMPATIBLE_VECTOR_TYPES_P (const_tree @var{type1}, const_tree @var{type2}) -Return true if there is no target-specific reason for treating -vector types @var{type1} and @var{type2} as distinct types. The caller -has already checked for target-independent reasons, meaning that the -types are known to have the same mode, to have the same number of elements, -and to have what the caller considers to be compatible element types. - -The main reason for defining this hook is to reject pairs of types -that are handled differently by the target's calling convention. -For example, when a new @var{N}-bit vector architecture is added -to a target, the target may want to handle normal @var{N}-bit -@code{VECTOR_TYPE} arguments and return values in the same way as -before, to maintain backwards compatibility. However, it may also -provide new, architecture-specific @code{VECTOR_TYPE}s that are passed -and returned in a more efficient way. It is then important to maintain -a distinction between the ``normal'' @code{VECTOR_TYPE}s and the new -architecture-specific ones. - -The default implementation returns true, which is correct for most targets. -@end deftypefn - -@deftypefn {Target Hook} opt_machine_mode TARGET_ARRAY_MODE (machine_mode @var{mode}, unsigned HOST_WIDE_INT @var{nelems}) -Return the mode that GCC should use for an array that has -@var{nelems} elements, with each element having mode @var{mode}. -Return no mode if the target has no special requirements. In the -latter case, GCC looks for an integer mode of the appropriate size -if available and uses BLKmode otherwise. Usually the search for the -integer mode is limited to @code{MAX_FIXED_MODE_SIZE}, but the -@code{TARGET_ARRAY_MODE_SUPPORTED_P} hook allows a larger mode to be -used in specific cases. - -The main use of this hook is to specify that an array of vectors should -also have a vector mode. The default implementation returns no mode. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ARRAY_MODE_SUPPORTED_P (machine_mode @var{mode}, unsigned HOST_WIDE_INT @var{nelems}) -Return true if GCC should try to use a scalar mode to store an array -of @var{nelems} elements, given that each element has mode @var{mode}. -Returning true here overrides the usual @code{MAX_FIXED_MODE} limit -and allows GCC to use any defined integer mode. - -One use of this hook is to support vector load and store operations -that operate on several homogeneous vectors. For example, ARM NEON -has operations like: - -@smallexample -int8x8x3_t vld3_s8 (const int8_t *) -@end smallexample - -where the return type is defined as: - -@smallexample -typedef struct int8x8x3_t -@{ - int8x8_t val[3]; -@} int8x8x3_t; -@end smallexample - -If this hook allows @code{val} to have a scalar mode, then -@code{int8x8x3_t} can have the same mode. GCC can then store -@code{int8x8x3_t}s in registers rather than forcing them onto the stack. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P (scalar_float_mode @var{mode}) -Define this to return nonzero if libgcc provides support for the -floating-point mode @var{mode}, which is known to pass -@code{TARGET_SCALAR_MODE_SUPPORTED_P}. The default version of this -hook returns true for all of @code{SFmode}, @code{DFmode}, -@code{XFmode} and @code{TFmode}, if such modes exist. -@end deftypefn - -@deftypefn {Target Hook} opt_scalar_float_mode TARGET_FLOATN_MODE (int @var{n}, bool @var{extended}) -Define this to return the machine mode to use for the type -@code{_Float@var{n}}, if @var{extended} is false, or the type -@code{_Float@var{n}x}, if @var{extended} is true. If such a type is not -supported, return @code{opt_scalar_float_mode ()}. The default version of -this hook returns @code{SFmode} for @code{_Float32}, @code{DFmode} for -@code{_Float64} and @code{_Float32x} and @code{TFmode} for -@code{_Float128}, if those modes exist and satisfy the requirements for -those types and pass @code{TARGET_SCALAR_MODE_SUPPORTED_P} and -@code{TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P}; for @code{_Float64x}, it -returns the first of @code{XFmode} and @code{TFmode} that exists and -satisfies the same requirements; for other types, it returns -@code{opt_scalar_float_mode ()}. The hook is only called for values -of @var{n} and @var{extended} that are valid according to -ISO/IEC TS 18661-3:2015; that is, @var{n} is one of 32, 64, 128, or, -if @var{extended} is false, 16 or greater than 128 and a multiple of 32. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_FLOATN_BUILTIN_P (int @var{func}) -Define this to return true if the @code{_Float@var{n}} and -@code{_Float@var{n}x} built-in functions should implicitly enable the -built-in function without the @code{__builtin_} prefix in addition to the -normal built-in function with the @code{__builtin_} prefix. The default is -to only enable built-in functions without the @code{__builtin_} prefix for -the GNU C langauge. In strict ANSI/ISO mode, the built-in function without -the @code{__builtin_} prefix is not enabled. The argument @code{FUNC} is the -@code{enum built_in_function} id of the function to be enabled. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_SMALL_REGISTER_CLASSES_FOR_MODE_P (machine_mode @var{mode}) -Define this to return nonzero for machine modes for which the port has -small register classes. If this target hook returns nonzero for a given -@var{mode}, the compiler will try to minimize the lifetime of registers -in @var{mode}. The hook may be called with @code{VOIDmode} as argument. -In this case, the hook is expected to return nonzero if it returns nonzero -for any mode. - -On some machines, it is risky to let hard registers live across arbitrary -insns. Typically, these machines have instructions that require values -to be in specific registers (like an accumulator), and reload will fail -if the required hard register is used for another purpose across such an -insn. - -Passes before reload do not know which hard registers will be used -in an instruction, but the machine modes of the registers set or used in -the instruction are already known. And for some machines, register -classes are small for, say, integer registers but not for floating point -registers. For example, the AMD x86-64 architecture requires specific -registers for the legacy x86 integer instructions, but there are many -SSE registers for floating point operations. On such targets, a good -strategy may be to return nonzero from this hook for @code{INTEGRAL_MODE_P} -machine modes but zero for the SSE register classes. - -The default version of this hook returns false for any mode. It is always -safe to redefine this hook to return with a nonzero value. But if you -unnecessarily define it, you will reduce the amount of optimizations -that can be performed in some cases. If you do not define this hook -to return a nonzero value when it is required, the compiler will run out -of spill registers and print a fatal error message. -@end deftypefn - -@node Scalar Return -@subsection How Scalar Function Values Are Returned -@cindex return values in registers -@cindex values, returned by functions -@cindex scalars, returned as values - -This section discusses the macros that control returning scalars as -values---values that can fit in registers. - -@deftypefn {Target Hook} rtx TARGET_FUNCTION_VALUE (const_tree @var{ret_type}, const_tree @var{fn_decl_or_type}, bool @var{outgoing}) - -Define this to return an RTX representing the place where a function -returns or receives a value of data type @var{ret_type}, a tree node -representing a data type. @var{fn_decl_or_type} is a tree node -representing @code{FUNCTION_DECL} or @code{FUNCTION_TYPE} of a -function being called. If @var{outgoing} is false, the hook should -compute the register in which the caller will see the return value. -Otherwise, the hook should return an RTX representing the place where -a function returns a value. - -On many machines, only @code{TYPE_MODE (@var{ret_type})} is relevant. -(Actually, on most machines, scalar values are returned in the same -place regardless of mode.) The value of the expression is usually a -@code{reg} RTX for the hard register where the return value is stored. -The value can also be a @code{parallel} RTX, if the return value is in -multiple places. See @code{TARGET_FUNCTION_ARG} for an explanation of the -@code{parallel} form. Note that the callee will populate every -location specified in the @code{parallel}, but if the first element of -the @code{parallel} contains the whole return value, callers will use -that element as the canonical location and ignore the others. The m68k -port uses this type of @code{parallel} to return pointers in both -@samp{%a0} (the canonical location) and @samp{%d0}. - -If @code{TARGET_PROMOTE_FUNCTION_RETURN} returns true, you must apply -the same promotion rules specified in @code{PROMOTE_MODE} if -@var{valtype} is a scalar type. - -If the precise function being called is known, @var{func} is a tree -node (@code{FUNCTION_DECL}) for it; otherwise, @var{func} is a null -pointer. This makes it possible to use a different value-returning -convention for specific functions when all their calls are -known. - -Some target machines have ``register windows'' so that the register in -which a function returns its value is not the same as the one in which -the caller sees the value. For such machines, you should return -different RTX depending on @var{outgoing}. - -@code{TARGET_FUNCTION_VALUE} is not used for return values with -aggregate data types, because these are returned in another way. See -@code{TARGET_STRUCT_VALUE_RTX} and related macros, below. -@end deftypefn - -@defmac FUNCTION_VALUE (@var{valtype}, @var{func}) -This macro has been deprecated. Use @code{TARGET_FUNCTION_VALUE} for -a new target instead. -@end defmac - -@defmac LIBCALL_VALUE (@var{mode}) -A C expression to create an RTX representing the place where a library -function returns a value of mode @var{mode}. - -Note that ``library function'' in this context means a compiler -support routine, used to perform arithmetic, whose name is known -specially by the compiler and was not mentioned in the C code being -compiled. -@end defmac - -@deftypefn {Target Hook} rtx TARGET_LIBCALL_VALUE (machine_mode @var{mode}, const_rtx @var{fun}) -Define this hook if the back-end needs to know the name of the libcall -function in order to determine where the result should be returned. - -The mode of the result is given by @var{mode} and the name of the called -library function is given by @var{fun}. The hook should return an RTX -representing the place where the library function result will be returned. - -If this hook is not defined, then LIBCALL_VALUE will be used. -@end deftypefn - -@defmac FUNCTION_VALUE_REGNO_P (@var{regno}) -A C expression that is nonzero if @var{regno} is the number of a hard -register in which the values of called function may come back. - -A register whose use for returning values is limited to serving as the -second of a pair (for a value of type @code{double}, say) need not be -recognized by this macro. So for most machines, this definition -suffices: - -@smallexample -#define FUNCTION_VALUE_REGNO_P(N) ((N) == 0) -@end smallexample - -If the machine has register windows, so that the caller and the called -function use different registers for the return value, this macro -should recognize only the caller's register numbers. - -This macro has been deprecated. Use @code{TARGET_FUNCTION_VALUE_REGNO_P} -for a new target instead. -@end defmac - -@deftypefn {Target Hook} bool TARGET_FUNCTION_VALUE_REGNO_P (const unsigned int @var{regno}) -A target hook that return @code{true} if @var{regno} is the number of a hard -register in which the values of called function may come back. - -A register whose use for returning values is limited to serving as the -second of a pair (for a value of type @code{double}, say) need not be -recognized by this target hook. - -If the machine has register windows, so that the caller and the called -function use different registers for the return value, this target hook -should recognize only the caller's register numbers. - -If this hook is not defined, then FUNCTION_VALUE_REGNO_P will be used. -@end deftypefn - -@defmac APPLY_RESULT_SIZE -Define this macro if @samp{untyped_call} and @samp{untyped_return} -need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for -saving and restoring an arbitrary return value. -@end defmac - -@deftypevr {Target Hook} bool TARGET_OMIT_STRUCT_RETURN_REG -Normally, when a function returns a structure by memory, the address -is passed as an invisible pointer argument, but the compiler also -arranges to return the address from the function like it would a normal -pointer return value. Define this to true if that behavior is -undesirable on your target. -@end deftypevr - -@deftypefn {Target Hook} bool TARGET_RETURN_IN_MSB (const_tree @var{type}) -This hook should return true if values of type @var{type} are returned -at the most significant end of a register (in other words, if they are -padded at the least significant end). You can assume that @var{type} -is returned in a register; the caller is required to check this. - -Note that the register provided by @code{TARGET_FUNCTION_VALUE} must -be able to hold the complete return value. For example, if a 1-, 2- -or 3-byte structure is returned at the most significant end of a -4-byte register, @code{TARGET_FUNCTION_VALUE} should provide an -@code{SImode} rtx. -@end deftypefn - -@node Aggregate Return -@subsection How Large Values Are Returned -@cindex aggregates as return values -@cindex large return values -@cindex returning aggregate values -@cindex structure value address - -When a function value's mode is @code{BLKmode} (and in some other -cases), the value is not returned according to -@code{TARGET_FUNCTION_VALUE} (@pxref{Scalar Return}). Instead, the -caller passes the address of a block of memory in which the value -should be stored. This address is called the @dfn{structure value -address}. - -This section describes how to control returning structure values in -memory. - -@deftypefn {Target Hook} bool TARGET_RETURN_IN_MEMORY (const_tree @var{type}, const_tree @var{fntype}) -This target hook should return a nonzero value to say to return the -function value in memory, just as large structures are always returned. -Here @var{type} will be the data type of the value, and @var{fntype} -will be the type of the function doing the returning, or @code{NULL} for -libcalls. - -Note that values of mode @code{BLKmode} must be explicitly handled -by this function. Also, the option @option{-fpcc-struct-return} -takes effect regardless of this macro. On most systems, it is -possible to leave the hook undefined; this causes a default -definition to be used, whose value is the constant 1 for @code{BLKmode} -values, and 0 otherwise. - -Do not use this hook to indicate that structures and unions should always -be returned in memory. You should instead use @code{DEFAULT_PCC_STRUCT_RETURN} -to indicate this. -@end deftypefn - -@defmac DEFAULT_PCC_STRUCT_RETURN -Define this macro to be 1 if all structure and union return values must be -in memory. Since this results in slower code, this should be defined -only if needed for compatibility with other compilers or with an ABI@. -If you define this macro to be 0, then the conventions used for structure -and union return values are decided by the @code{TARGET_RETURN_IN_MEMORY} -target hook. - -If not defined, this defaults to the value 1. -@end defmac - -@deftypefn {Target Hook} rtx TARGET_STRUCT_VALUE_RTX (tree @var{fndecl}, int @var{incoming}) -This target hook should return the location of the structure value -address (normally a @code{mem} or @code{reg}), or 0 if the address is -passed as an ``invisible'' first argument. Note that @var{fndecl} may -be @code{NULL}, for libcalls. You do not need to define this target -hook if the address is always passed as an ``invisible'' first -argument. - -On some architectures the place where the structure value address -is found by the called function is not the same place that the -caller put it. This can be due to register windows, or it could -be because the function prologue moves it to a different place. -@var{incoming} is @code{1} or @code{2} when the location is needed in -the context of the called function, and @code{0} in the context of -the caller. - -If @var{incoming} is nonzero and the address is to be found on the -stack, return a @code{mem} which refers to the frame pointer. If -@var{incoming} is @code{2}, the result is being used to fetch the -structure value address at the beginning of a function. If you need -to emit adjusting code, you should do it at this point. -@end deftypefn - -@defmac PCC_STATIC_STRUCT_RETURN -Define this macro if the usual system convention on the target machine -for returning structures and unions is for the called function to return -the address of a static variable containing the value. - -Do not define this if the usual system convention is for the caller to -pass an address to the subroutine. - -This macro has effect in @option{-fpcc-struct-return} mode, but it does -nothing when you use @option{-freg-struct-return} mode. -@end defmac - -@deftypefn {Target Hook} fixed_size_mode TARGET_GET_RAW_RESULT_MODE (int @var{regno}) -This target hook returns the mode to be used when accessing raw return -registers in @code{__builtin_return}. Define this macro if the value -in @var{reg_raw_mode} is not correct. -@end deftypefn - -@deftypefn {Target Hook} fixed_size_mode TARGET_GET_RAW_ARG_MODE (int @var{regno}) -This target hook returns the mode to be used when accessing raw argument -registers in @code{__builtin_apply_args}. Define this macro if the value -in @var{reg_raw_mode} is not correct. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_EMPTY_RECORD_P (const_tree @var{type}) -This target hook returns true if the type is an empty record. The default -is to return @code{false}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_WARN_PARAMETER_PASSING_ABI (cumulative_args_t @var{ca}, tree @var{type}) -This target hook warns about the change in empty class parameter passing -ABI. -@end deftypefn - -@node Caller Saves -@subsection Caller-Saves Register Allocation - -If you enable it, GCC can save registers around function calls. This -makes it possible to use call-clobbered registers to hold variables that -must live across calls. - -@defmac HARD_REGNO_CALLER_SAVE_MODE (@var{regno}, @var{nregs}) -A C expression specifying which mode is required for saving @var{nregs} -of a pseudo-register in call-clobbered hard register @var{regno}. If -@var{regno} is unsuitable for caller save, @code{VOIDmode} should be -returned. For most machines this macro need not be defined since GCC -will select the smallest suitable mode. -@end defmac - -@node Function Entry -@subsection Function Entry and Exit -@cindex function entry and exit -@cindex prologue -@cindex epilogue - -This section describes the macros that output function entry -(@dfn{prologue}) and exit (@dfn{epilogue}) code. - -@deftypefn {Target Hook} void TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY (FILE *@var{file}, unsigned HOST_WIDE_INT @var{patch_area_size}, bool @var{record_p}) -Generate a patchable area at the function start, consisting of -@var{patch_area_size} NOP instructions. If the target supports named -sections and if @var{record_p} is true, insert a pointer to the current -location in the table of patchable functions. The default implementation -of the hook places the table of pointers in the special section named -@code{__patchable_function_entries}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_FUNCTION_PROLOGUE (FILE *@var{file}) -If defined, a function that outputs the assembler code for entry to a -function. The prologue is responsible for setting up the stack frame, -initializing the frame pointer register, saving registers that must be -saved, and allocating @var{size} additional bytes of storage for the -local variables. @var{file} is a stdio stream to which the assembler -code should be output. - -The label for the beginning of the function need not be output by this -macro. That has already been done when the macro is run. - -@findex regs_ever_live -To determine which registers to save, the macro can refer to the array -@code{regs_ever_live}: element @var{r} is nonzero if hard register -@var{r} is used anywhere within the function. This implies the function -prologue should save register @var{r}, provided it is not one of the -call-used registers. (@code{TARGET_ASM_FUNCTION_EPILOGUE} must likewise use -@code{regs_ever_live}.) - -On machines that have ``register windows'', the function entry code does -not save on the stack the registers that are in the windows, even if -they are supposed to be preserved by function calls; instead it takes -appropriate steps to ``push'' the register stack, if any non-call-used -registers are used in the function. - -@findex frame_pointer_needed -On machines where functions may or may not have frame-pointers, the -function entry code must vary accordingly; it must set up the frame -pointer if one is wanted, and not otherwise. To determine whether a -frame pointer is in wanted, the macro can refer to the variable -@code{frame_pointer_needed}. The variable's value will be 1 at run -time in a function that needs a frame pointer. @xref{Elimination}. - -The function entry code is responsible for allocating any stack space -required for the function. This stack space consists of the regions -listed below. In most cases, these regions are allocated in the -order listed, with the last listed region closest to the top of the -stack (the lowest address if @code{STACK_GROWS_DOWNWARD} is defined, and -the highest address if it is not defined). You can use a different order -for a machine if doing so is more convenient or required for -compatibility reasons. Except in cases where required by standard -or by a debugger, there is no reason why the stack layout used by GCC -need agree with that used by other compilers for a machine. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_FUNCTION_END_PROLOGUE (FILE *@var{file}) -If defined, a function that outputs assembler code at the end of a -prologue. This should be used when the function prologue is being -emitted as RTL, and you have some extra assembler that needs to be -emitted. @xref{prologue instruction pattern}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_FUNCTION_BEGIN_EPILOGUE (FILE *@var{file}) -If defined, a function that outputs assembler code at the start of an -epilogue. This should be used when the function epilogue is being -emitted as RTL, and you have some extra assembler that needs to be -emitted. @xref{epilogue instruction pattern}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_FUNCTION_EPILOGUE (FILE *@var{file}) -If defined, a function that outputs the assembler code for exit from a -function. The epilogue is responsible for restoring the saved -registers and stack pointer to their values when the function was -called, and returning control to the caller. This macro takes the -same argument as the macro @code{TARGET_ASM_FUNCTION_PROLOGUE}, and the -registers to restore are determined from @code{regs_ever_live} and -@code{CALL_USED_REGISTERS} in the same way. - -On some machines, there is a single instruction that does all the work -of returning from the function. On these machines, give that -instruction the name @samp{return} and do not define the macro -@code{TARGET_ASM_FUNCTION_EPILOGUE} at all. - -Do not define a pattern named @samp{return} if you want the -@code{TARGET_ASM_FUNCTION_EPILOGUE} to be used. If you want the target -switches to control whether return instructions or epilogues are used, -define a @samp{return} pattern with a validity condition that tests the -target switches appropriately. If the @samp{return} pattern's validity -condition is false, epilogues will be used. - -On machines where functions may or may not have frame-pointers, the -function exit code must vary accordingly. Sometimes the code for these -two cases is completely different. To determine whether a frame pointer -is wanted, the macro can refer to the variable -@code{frame_pointer_needed}. The variable's value will be 1 when compiling -a function that needs a frame pointer. - -Normally, @code{TARGET_ASM_FUNCTION_PROLOGUE} and -@code{TARGET_ASM_FUNCTION_EPILOGUE} must treat leaf functions specially. -The C variable @code{current_function_is_leaf} is nonzero for such a -function. @xref{Leaf Functions}. - -On some machines, some functions pop their arguments on exit while -others leave that for the caller to do. For example, the 68020 when -given @option{-mrtd} pops arguments in functions that take a fixed -number of arguments. - -@findex pops_args -@findex crtl->args.pops_args -Your definition of the macro @code{RETURN_POPS_ARGS} decides which -functions pop their own arguments. @code{TARGET_ASM_FUNCTION_EPILOGUE} -needs to know what was decided. The number of bytes of the current -function's arguments that this function should pop is available in -@code{crtl->args.pops_args}. @xref{Scalar Return}. -@end deftypefn - -@itemize @bullet -@item -@findex pretend_args_size -@findex crtl->args.pretend_args_size -A region of @code{crtl->args.pretend_args_size} bytes of -uninitialized space just underneath the first argument arriving on the -stack. (This may not be at the very start of the allocated stack region -if the calling sequence has pushed anything else since pushing the stack -arguments. But usually, on such machines, nothing else has been pushed -yet, because the function prologue itself does all the pushing.) This -region is used on machines where an argument may be passed partly in -registers and partly in memory, and, in some cases to support the -features in @code{<stdarg.h>}. - -@item -An area of memory used to save certain registers used by the function. -The size of this area, which may also include space for such things as -the return address and pointers to previous stack frames, is -machine-specific and usually depends on which registers have been used -in the function. Machines with register windows often do not require -a save area. - -@item -A region of at least @var{size} bytes, possibly rounded up to an allocation -boundary, to contain the local variables of the function. On some machines, -this region and the save area may occur in the opposite order, with the -save area closer to the top of the stack. - -@item -@cindex @code{ACCUMULATE_OUTGOING_ARGS} and stack frames -Optionally, when @code{ACCUMULATE_OUTGOING_ARGS} is defined, a region of -@code{crtl->outgoing_args_size} bytes to be used for outgoing -argument lists of the function. @xref{Stack Arguments}. -@end itemize - -@defmac EXIT_IGNORE_STACK -Define this macro as a C expression that is nonzero if the return -instruction or the function epilogue ignores the value of the stack -pointer; in other words, if it is safe to delete an instruction to -adjust the stack pointer before a return from the function. The -default is 0. - -Note that this macro's value is relevant only for functions for which -frame pointers are maintained. It is never safe to delete a final -stack adjustment in a function that has no frame pointer, and the -compiler knows this regardless of @code{EXIT_IGNORE_STACK}. -@end defmac - -@defmac EPILOGUE_USES (@var{regno}) -Define this macro as a C expression that is nonzero for registers that are -used by the epilogue or the @samp{return} pattern. The stack and frame -pointer registers are already assumed to be used as needed. -@end defmac - -@defmac EH_USES (@var{regno}) -Define this macro as a C expression that is nonzero for registers that are -used by the exception handling mechanism, and so should be considered live -on entry to an exception edge. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_OUTPUT_MI_THUNK (FILE *@var{file}, tree @var{thunk_fndecl}, HOST_WIDE_INT @var{delta}, HOST_WIDE_INT @var{vcall_offset}, tree @var{function}) -A function that outputs the assembler code for a thunk -function, used to implement C++ virtual function calls with multiple -inheritance. The thunk acts as a wrapper around a virtual function, -adjusting the implicit object parameter before handing control off to -the real function. - -First, emit code to add the integer @var{delta} to the location that -contains the incoming first argument. Assume that this argument -contains a pointer, and is the one used to pass the @code{this} pointer -in C++. This is the incoming argument @emph{before} the function prologue, -e.g.@: @samp{%o0} on a sparc. The addition must preserve the values of -all other incoming arguments. - -Then, if @var{vcall_offset} is nonzero, an additional adjustment should be -made after adding @code{delta}. In particular, if @var{p} is the -adjusted pointer, the following adjustment should be made: - -@smallexample -p += (*((ptrdiff_t **)p))[vcall_offset/sizeof(ptrdiff_t)] -@end smallexample - -After the additions, emit code to jump to @var{function}, which is a -@code{FUNCTION_DECL}. This is a direct pure jump, not a call, and does -not touch the return address. Hence returning from @var{FUNCTION} will -return to whoever called the current @samp{thunk}. - -The effect must be as if @var{function} had been called directly with -the adjusted first argument. This macro is responsible for emitting all -of the code for a thunk function; @code{TARGET_ASM_FUNCTION_PROLOGUE} -and @code{TARGET_ASM_FUNCTION_EPILOGUE} are not invoked. - -The @var{thunk_fndecl} is redundant. (@var{delta} and @var{function} -have already been extracted from it.) It might possibly be useful on -some targets, but probably not. - -If you do not define this macro, the target-independent code in the C++ -front end will generate a less efficient heavyweight thunk that calls -@var{function} instead of jumping to it. The generic approach does -not support varargs. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ASM_CAN_OUTPUT_MI_THUNK (const_tree @var{thunk_fndecl}, HOST_WIDE_INT @var{delta}, HOST_WIDE_INT @var{vcall_offset}, const_tree @var{function}) -A function that returns true if TARGET_ASM_OUTPUT_MI_THUNK would be able -to output the assembler code for the thunk function specified by the -arguments it is passed, and false otherwise. In the latter case, the -generic approach will be used by the C++ front end, with the limitations -previously exposed. -@end deftypefn - -@node Profiling -@subsection Generating Code for Profiling -@cindex profiling, code generation - -These macros will help you generate code for profiling. - -@defmac FUNCTION_PROFILER (@var{file}, @var{labelno}) -A C statement or compound statement to output to @var{file} some -assembler code to call the profiling subroutine @code{mcount}. - -@findex mcount -The details of how @code{mcount} expects to be called are determined by -your operating system environment, not by GCC@. To figure them out, -compile a small program for profiling using the system's installed C -compiler and look at the assembler code that results. - -Older implementations of @code{mcount} expect the address of a counter -variable to be loaded into some register. The name of this variable is -@samp{LP} followed by the number @var{labelno}, so you would generate -the name using @samp{LP%d} in a @code{fprintf}. -@end defmac - -@defmac PROFILE_HOOK -A C statement or compound statement to output to @var{file} some assembly -code to call the profiling subroutine @code{mcount} even the target does -not support profiling. -@end defmac - -@defmac NO_PROFILE_COUNTERS -Define this macro to be an expression with a nonzero value if the -@code{mcount} subroutine on your system does not need a counter variable -allocated for each function. This is true for almost all modern -implementations. If you define this macro, you must not use the -@var{labelno} argument to @code{FUNCTION_PROFILER}. -@end defmac - -@defmac PROFILE_BEFORE_PROLOGUE -Define this macro if the code for function profiling should come before -the function prologue. Normally, the profiling code comes after. -@end defmac - -@deftypefn {Target Hook} bool TARGET_KEEP_LEAF_WHEN_PROFILED (void) -This target hook returns true if the target wants the leaf flag for -the current function to stay true even if it calls mcount. This might -make sense for targets using the leaf flag only to determine whether a -stack frame needs to be generated or not and for which the call to -mcount is generated before the function prologue. -@end deftypefn - -@node Tail Calls -@subsection Permitting tail calls -@cindex tail calls - -@deftypefn {Target Hook} bool TARGET_FUNCTION_OK_FOR_SIBCALL (tree @var{decl}, tree @var{exp}) -True if it is OK to do sibling call optimization for the specified -call expression @var{exp}. @var{decl} will be the called function, -or @code{NULL} if this is an indirect call. - -It is not uncommon for limitations of calling conventions to prevent -tail calls to functions outside the current unit of translation, or -during PIC compilation. The hook is used to enforce these restrictions, -as the @code{sibcall} md pattern cannot fail, or fall over to a -``normal'' call. The criteria for successful sibling call optimization -may vary greatly between different architectures. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_EXTRA_LIVE_ON_ENTRY (bitmap @var{regs}) -Add any hard registers to @var{regs} that are live on entry to the -function. This hook only needs to be defined to provide registers that -cannot be found by examination of FUNCTION_ARG_REGNO_P, the callee saved -registers, STATIC_CHAIN_INCOMING_REGNUM, STATIC_CHAIN_REGNUM, -TARGET_STRUCT_VALUE_RTX, FRAME_POINTER_REGNUM, EH_USES, -FRAME_POINTER_REGNUM, ARG_POINTER_REGNUM, and the PIC_OFFSET_TABLE_REGNUM. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SET_UP_BY_PROLOGUE (struct hard_reg_set_container *@var{}) -This hook should add additional registers that are computed by the prologue -to the hard regset for shrink-wrapping optimization purposes. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_WARN_FUNC_RETURN (tree) -True if a function's return statements should be checked for matching -the function's return type. This includes checking for falling off the end -of a non-void function. Return false if no such check should be made. -@end deftypefn - -@node Shrink-wrapping separate components -@subsection Shrink-wrapping separate components -@cindex shrink-wrapping separate components - -The prologue may perform a variety of target dependent tasks such as -saving callee-saved registers, saving the return address, aligning the -stack, creating a stack frame, initializing the PIC register, setting -up the static chain, etc. - -On some targets some of these tasks may be independent of others and -thus may be shrink-wrapped separately. These independent tasks are -referred to as components and are handled generically by the target -independent parts of GCC. - -Using the following hooks those prologue or epilogue components can be -shrink-wrapped separately, so that the initialization (and possibly -teardown) those components do is not done as frequently on execution -paths where this would unnecessary. - -What exactly those components are is up to the target code; the generic -code treats them abstractly, as a bit in an @code{sbitmap}. These -@code{sbitmap}s are allocated by the @code{shrink_wrap.get_separate_components} -and @code{shrink_wrap.components_for_bb} hooks, and deallocated by the -generic code. - -@deftypefn {Target Hook} sbitmap TARGET_SHRINK_WRAP_GET_SEPARATE_COMPONENTS (void) -This hook should return an @code{sbitmap} with the bits set for those -components that can be separately shrink-wrapped in the current function. -Return @code{NULL} if the current function should not get any separate -shrink-wrapping. -Don't define this hook if it would always return @code{NULL}. -If it is defined, the other hooks in this group have to be defined as well. -@end deftypefn - -@deftypefn {Target Hook} sbitmap TARGET_SHRINK_WRAP_COMPONENTS_FOR_BB (basic_block) -This hook should return an @code{sbitmap} with the bits set for those -components where either the prologue component has to be executed before -the @code{basic_block}, or the epilogue component after it, or both. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SHRINK_WRAP_DISQUALIFY_COMPONENTS (sbitmap @var{components}, edge @var{e}, sbitmap @var{edge_components}, bool @var{is_prologue}) -This hook should clear the bits in the @var{components} bitmap for those -components in @var{edge_components} that the target cannot handle on edge -@var{e}, where @var{is_prologue} says if this is for a prologue or an -epilogue instead. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SHRINK_WRAP_EMIT_PROLOGUE_COMPONENTS (sbitmap) -Emit prologue insns for the components indicated by the parameter. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SHRINK_WRAP_EMIT_EPILOGUE_COMPONENTS (sbitmap) -Emit epilogue insns for the components indicated by the parameter. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SHRINK_WRAP_SET_HANDLED_COMPONENTS (sbitmap) -Mark the components in the parameter as handled, so that the -@code{prologue} and @code{epilogue} named patterns know to ignore those -components. The target code should not hang on to the @code{sbitmap}, it -will be deleted after this call. -@end deftypefn - -@node Stack Smashing Protection -@subsection Stack smashing protection -@cindex stack smashing protection - -@deftypefn {Target Hook} tree TARGET_STACK_PROTECT_GUARD (void) -This hook returns a @code{DECL} node for the external variable to use -for the stack protection guard. This variable is initialized by the -runtime to some random value and is used to initialize the guard value -that is placed at the top of the local stack frame. The type of this -variable must be @code{ptr_type_node}. - -The default version of this hook creates a variable called -@samp{__stack_chk_guard}, which is normally defined in @file{libgcc2.c}. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_STACK_PROTECT_FAIL (void) -This hook returns a @code{CALL_EXPR} that alerts the runtime that the -stack protect guard variable has been modified. This expression should -involve a call to a @code{noreturn} function. - -The default version of this hook invokes a function called -@samp{__stack_chk_fail}, taking no arguments. This function is -normally defined in @file{libgcc2.c}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_STACK_PROTECT_RUNTIME_ENABLED_P (void) -Returns true if the target wants GCC's default stack protect runtime support, -otherwise return false. The default implementation always returns true. -@end deftypefn - -@deftypefn {Common Target Hook} bool TARGET_SUPPORTS_SPLIT_STACK (bool @var{report}, struct gcc_options *@var{opts}) -Whether this target supports splitting the stack when the options -described in @var{opts} have been passed. This is called -after options have been parsed, so the target may reject splitting -the stack in some configurations. The default version of this hook -returns false. If @var{report} is true, this function may issue a warning -or error; if @var{report} is false, it must simply return a value -@end deftypefn - -@deftypefn {Common Target Hook} {vec<const char *>} TARGET_GET_VALID_OPTION_VALUES (int @var{option_code}, const char *@var{prefix}) -The hook is used for options that have a non-trivial list of -possible option values. OPTION_CODE is option code of opt_code -enum type. PREFIX is used for bash completion and allows an implementation -to return more specific completion based on the prefix. All string values -should be allocated from heap memory and consumers should release them. -The result will be pruned to cases with PREFIX if not NULL. -@end deftypefn - -@node Miscellaneous Register Hooks -@subsection Miscellaneous register hooks -@cindex miscellaneous register hooks - -@deftypevr {Target Hook} bool TARGET_CALL_FUSAGE_CONTAINS_NON_CALLEE_CLOBBERS -Set to true if each call that binds to a local definition explicitly -clobbers or sets all non-fixed registers modified by performing the call. -That is, by the call pattern itself, or by code that might be inserted by the -linker (e.g.@: stubs, veneers, branch islands), but not including those -modifiable by the callee. The affected registers may be mentioned explicitly -in the call pattern, or included as clobbers in CALL_INSN_FUNCTION_USAGE. -The default version of this hook is set to false. The purpose of this hook -is to enable the fipa-ra optimization. -@end deftypevr - -@node Varargs -@section Implementing the Varargs Macros -@cindex varargs implementation - -GCC comes with an implementation of @code{<varargs.h>} and -@code{<stdarg.h>} that work without change on machines that pass arguments -on the stack. Other machines require their own implementations of -varargs, and the two machine independent header files must have -conditionals to include it. - -ISO @code{<stdarg.h>} differs from traditional @code{<varargs.h>} mainly in -the calling convention for @code{va_start}. The traditional -implementation takes just one argument, which is the variable in which -to store the argument pointer. The ISO implementation of -@code{va_start} takes an additional second argument. The user is -supposed to write the last named argument of the function here. - -However, @code{va_start} should not use this argument. The way to find -the end of the named arguments is with the built-in functions described -below. - -@defmac __builtin_saveregs () -Use this built-in function to save the argument registers in memory so -that the varargs mechanism can access them. Both ISO and traditional -versions of @code{va_start} must use @code{__builtin_saveregs}, unless -you use @code{TARGET_SETUP_INCOMING_VARARGS} (see below) instead. - -On some machines, @code{__builtin_saveregs} is open-coded under the -control of the target hook @code{TARGET_EXPAND_BUILTIN_SAVEREGS}. On -other machines, it calls a routine written in assembler language, -found in @file{libgcc2.c}. - -Code generated for the call to @code{__builtin_saveregs} appears at the -beginning of the function, as opposed to where the call to -@code{__builtin_saveregs} is written, regardless of what the code is. -This is because the registers must be saved before the function starts -to use them for its own purposes. -@c i rewrote the first sentence above to fix an overfull hbox. --mew -@c 10feb93 -@end defmac - -@defmac __builtin_next_arg (@var{lastarg}) -This builtin returns the address of the first anonymous stack -argument, as type @code{void *}. If @code{ARGS_GROW_DOWNWARD}, it -returns the address of the location above the first anonymous stack -argument. Use it in @code{va_start} to initialize the pointer for -fetching arguments from the stack. Also use it in @code{va_start} to -verify that the second parameter @var{lastarg} is the last named argument -of the current function. -@end defmac - -@defmac __builtin_classify_type (@var{object}) -Since each machine has its own conventions for which data types are -passed in which kind of register, your implementation of @code{va_arg} -has to embody these conventions. The easiest way to categorize the -specified data type is to use @code{__builtin_classify_type} together -with @code{sizeof} and @code{__alignof__}. - -@code{__builtin_classify_type} ignores the value of @var{object}, -considering only its data type. It returns an integer describing what -kind of type that is---integer, floating, pointer, structure, and so on. - -The file @file{typeclass.h} defines an enumeration that you can use to -interpret the values of @code{__builtin_classify_type}. -@end defmac - -These machine description macros help implement varargs: - -@deftypefn {Target Hook} rtx TARGET_EXPAND_BUILTIN_SAVEREGS (void) -If defined, this hook produces the machine-specific code for a call to -@code{__builtin_saveregs}. This code will be moved to the very -beginning of the function, before any parameter access are made. The -return value of this function should be an RTX that contains the value -to use as the return of @code{__builtin_saveregs}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SETUP_INCOMING_VARARGS (cumulative_args_t @var{args_so_far}, const function_arg_info @var{&arg}, int *@var{pretend_args_size}, int @var{second_time}) -This target hook offers an alternative to using -@code{__builtin_saveregs} and defining the hook -@code{TARGET_EXPAND_BUILTIN_SAVEREGS}. Use it to store the anonymous -register arguments into the stack so that all the arguments appear to -have been passed consecutively on the stack. Once this is done, you can -use the standard implementation of varargs that works for machines that -pass all their arguments on the stack. - -The argument @var{args_so_far} points to the @code{CUMULATIVE_ARGS} data -structure, containing the values that are obtained after processing the -named arguments. The argument @var{arg} describes the last of these named -arguments. The argument @var{arg} should not be used if the function type -satisfies @code{TYPE_NO_NAMED_ARGS_STDARG_P}, since in that case there are -no named arguments and all arguments are accessed with @code{va_arg}. - -The target hook should do two things: first, push onto the stack all the -argument registers @emph{not} used for the named arguments, and second, -store the size of the data thus pushed into the @code{int}-valued -variable pointed to by @var{pretend_args_size}. The value that you -store here will serve as additional offset for setting up the stack -frame. - -Because you must generate code to push the anonymous arguments at -compile time without knowing their data types, -@code{TARGET_SETUP_INCOMING_VARARGS} is only useful on machines that -have just a single category of argument register and use it uniformly -for all data types. - -If the argument @var{second_time} is nonzero, it means that the -arguments of the function are being analyzed for the second time. This -happens for an inline function, which is not actually compiled until the -end of the source file. The hook @code{TARGET_SETUP_INCOMING_VARARGS} should -not generate any instructions in this case. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_STRICT_ARGUMENT_NAMING (cumulative_args_t @var{ca}) -Define this hook to return @code{true} if the location where a function -argument is passed depends on whether or not it is a named argument. - -This hook controls how the @var{named} argument to @code{TARGET_FUNCTION_ARG} -is set for varargs and stdarg functions. If this hook returns -@code{true}, the @var{named} argument is always true for named -arguments, and false for unnamed arguments. If it returns @code{false}, -but @code{TARGET_PRETEND_OUTGOING_VARARGS_NAMED} returns @code{true}, -then all arguments are treated as named. Otherwise, all named arguments -except the last are treated as named. - -You need not define this hook if it always returns @code{false}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_CALL_ARGS (rtx, @var{tree}) -While generating RTL for a function call, this target hook is invoked once -for each argument passed to the function, either a register returned by -@code{TARGET_FUNCTION_ARG} or a memory location. It is called just -before the point where argument registers are stored. The type of the -function to be called is also passed as the second argument; it is -@code{NULL_TREE} for libcalls. The @code{TARGET_END_CALL_ARGS} hook is -invoked just after the code to copy the return reg has been emitted. -This functionality can be used to perform special setup of call argument -registers if a target needs it. -For functions without arguments, the hook is called once with @code{pc_rtx} -passed instead of an argument register. -Most ports do not need to implement anything for this hook. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_END_CALL_ARGS (void) -This target hook is invoked while generating RTL for a function call, -just after the point where the return reg is copied into a pseudo. It -signals that all the call argument and return registers for the just -emitted call are now no longer in use. -Most ports do not need to implement anything for this hook. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_PRETEND_OUTGOING_VARARGS_NAMED (cumulative_args_t @var{ca}) -If you need to conditionally change ABIs so that one works with -@code{TARGET_SETUP_INCOMING_VARARGS}, but the other works like neither -@code{TARGET_SETUP_INCOMING_VARARGS} nor @code{TARGET_STRICT_ARGUMENT_NAMING} was -defined, then define this hook to return @code{true} if -@code{TARGET_SETUP_INCOMING_VARARGS} is used, @code{false} otherwise. -Otherwise, you should not define this hook. -@end deftypefn - -@node Trampolines -@section Support for Nested Functions -@cindex support for nested functions -@cindex trampolines for nested functions -@cindex descriptors for nested functions -@cindex nested functions, support for - -Taking the address of a nested function requires special compiler -handling to ensure that the static chain register is loaded when -the function is invoked via an indirect call. - -GCC has traditionally supported nested functions by creating an -executable @dfn{trampoline} at run time when the address of a nested -function is taken. This is a small piece of code which normally -resides on the stack, in the stack frame of the containing function. -The trampoline loads the static chain register and then jumps to the -real address of the nested function. - -The use of trampolines requires an executable stack, which is a -security risk. To avoid this problem, GCC also supports another -strategy: using descriptors for nested functions. Under this model, -taking the address of a nested function results in a pointer to a -non-executable function descriptor object. Initializing the static chain -from the descriptor is handled at indirect call sites. - -On some targets, including HPPA and IA-64, function descriptors may be -mandated by the ABI or be otherwise handled in a target-specific way -by the back end in its code generation strategy for indirect calls. -GCC also provides its own generic descriptor implementation to support the -@option{-fno-trampolines} option. In this case runtime detection of -function descriptors at indirect call sites relies on descriptor -pointers being tagged with a bit that is never set in bare function -addresses. Since GCC's generic function descriptors are -not ABI-compliant, this option is typically used only on a -per-language basis (notably by Ada) or when it can otherwise be -applied to the whole program. - -For languages other than Ada, the @code{-ftrampolines} and -@code{-fno-trampolines} options currently have no effect, and -trampolines are always generated on platforms that need them -for nested functions. - -Define the following hook if your backend either implements ABI-specified -descriptor support, or can use GCC's generic descriptor implementation -for nested functions. - -@deftypevr {Target Hook} int TARGET_CUSTOM_FUNCTION_DESCRIPTORS -If the target can use GCC's generic descriptor mechanism for nested -functions, define this hook to a power of 2 representing an unused bit -in function pointers which can be used to differentiate descriptors at -run time. This value gives the number of bytes by which descriptor -pointers are misaligned compared to function pointers. For example, on -targets that require functions to be aligned to a 4-byte boundary, a -value of either 1 or 2 is appropriate unless the architecture already -reserves the bit for another purpose, such as on ARM. - -Define this hook to 0 if the target implements ABI support for -function descriptors in its standard calling sequence, like for example -HPPA or IA-64. - -Using descriptors for nested functions -eliminates the need for trampolines that reside on the stack and require -it to be made executable. -@end deftypevr - -The following macros tell GCC how to generate code to allocate and -initialize an executable trampoline. You can also use this interface -if your back end needs to create ABI-specified non-executable descriptors; in -this case the "trampoline" created is the descriptor containing data only. - -The instructions in an executable trampoline must do two things: load -a constant address into the static chain register, and jump to the real -address of the nested function. On CISC machines such as the m68k, -this requires two instructions, a move immediate and a jump. Then the -two addresses exist in the trampoline as word-long immediate operands. -On RISC machines, it is often necessary to load each address into a -register in two parts. Then pieces of each address form separate -immediate operands. - -The code generated to initialize the trampoline must store the variable -parts---the static chain value and the function address---into the -immediate operands of the instructions. On a CISC machine, this is -simply a matter of copying each address to a memory reference at the -proper offset from the start of the trampoline. On a RISC machine, it -may be necessary to take out pieces of the address and store them -separately. - -@deftypefn {Target Hook} void TARGET_ASM_TRAMPOLINE_TEMPLATE (FILE *@var{f}) -This hook is called by @code{assemble_trampoline_template} to output, -on the stream @var{f}, assembler code for a block of data that contains -the constant parts of a trampoline. This code should not include a -label---the label is taken care of automatically. - -If you do not define this hook, it means no template is needed -for the target. Do not define this hook on systems where the block move -code to copy the trampoline into place would be larger than the code -to generate it on the spot. -@end deftypefn - -@defmac TRAMPOLINE_SECTION -Return the section into which the trampoline template is to be placed -(@pxref{Sections}). The default value is @code{readonly_data_section}. -@end defmac - -@defmac TRAMPOLINE_SIZE -A C expression for the size in bytes of the trampoline, as an integer. -@end defmac - -@defmac TRAMPOLINE_ALIGNMENT -Alignment required for trampolines, in bits. - -If you don't define this macro, the value of @code{FUNCTION_ALIGNMENT} -is used for aligning trampolines. -@end defmac - -@deftypefn {Target Hook} void TARGET_TRAMPOLINE_INIT (rtx @var{m_tramp}, tree @var{fndecl}, rtx @var{static_chain}) -This hook is called to initialize a trampoline. -@var{m_tramp} is an RTX for the memory block for the trampoline; @var{fndecl} -is the @code{FUNCTION_DECL} for the nested function; @var{static_chain} is an -RTX for the static chain value that should be passed to the function -when it is called. - -If the target defines @code{TARGET_ASM_TRAMPOLINE_TEMPLATE}, then the -first thing this hook should do is emit a block move into @var{m_tramp} -from the memory block returned by @code{assemble_trampoline_template}. -Note that the block move need only cover the constant parts of the -trampoline. If the target isolates the variable parts of the trampoline -to the end, not all @code{TRAMPOLINE_SIZE} bytes need be copied. - -If the target requires any other actions, such as flushing caches -(possibly calling function maybe_emit_call_builtin___clear_cache) or -enabling stack execution, these actions should be performed after -initializing the trampoline proper. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_EMIT_CALL_BUILTIN___CLEAR_CACHE (rtx @var{begin}, rtx @var{end}) -On targets that do not define a @code{clear_cache} insn expander, -but that define the @code{CLEAR_CACHE_INSN} macro, -maybe_emit_call_builtin___clear_cache relies on this target hook -to clear an address range in the instruction cache. - -The default implementation calls the @code{__clear_cache} builtin, -taking the assembler name from the builtin declaration. Overriding -definitions may call alternate functions, with alternate calling -conventions, or emit alternate RTX to perform the job. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_TRAMPOLINE_ADJUST_ADDRESS (rtx @var{addr}) -This hook should perform any machine-specific adjustment in -the address of the trampoline. Its argument contains the address of the -memory block that was passed to @code{TARGET_TRAMPOLINE_INIT}. In case -the address to be used for a function call should be different from the -address at which the template was stored, the different address should -be returned; otherwise @var{addr} should be returned unchanged. -If this hook is not defined, @var{addr} will be used for function calls. -@end deftypefn - -Implementing trampolines is difficult on many machines because they have -separate instruction and data caches. Writing into a stack location -fails to clear the memory in the instruction cache, so when the program -jumps to that location, it executes the old contents. - -Here are two possible solutions. One is to clear the relevant parts of -the instruction cache whenever a trampoline is set up. The other is to -make all trampolines identical, by having them jump to a standard -subroutine. The former technique makes trampoline execution faster; the -latter makes initialization faster. - -To clear the instruction cache when a trampoline is initialized, define -the following macro. - -@defmac CLEAR_INSN_CACHE (@var{beg}, @var{end}) -If defined, expands to a C expression clearing the @emph{instruction -cache} in the specified interval. The definition of this macro would -typically be a series of @code{asm} statements. Both @var{beg} and -@var{end} are pointer expressions. -@end defmac - -To use a standard subroutine, define the following macro. In addition, -you must make sure that the instructions in a trampoline fill an entire -cache line with identical instructions, or else ensure that the -beginning of the trampoline code is always aligned at the same point in -its cache line. Look in @file{m68k.h} as a guide. - -@defmac TRANSFER_FROM_TRAMPOLINE -Define this macro if trampolines need a special subroutine to do their -work. The macro should expand to a series of @code{asm} statements -which will be compiled with GCC@. They go in a library function named -@code{__transfer_from_trampoline}. - -If you need to avoid executing the ordinary prologue code of a compiled -C function when you jump to the subroutine, you can do so by placing a -special label of your own in the assembler code. Use one @code{asm} -statement to generate an assembler label, and another to make the label -global. Then trampolines can use that label to jump directly to your -special assembler code. -@end defmac - -@node Library Calls -@section Implicit Calls to Library Routines -@cindex library subroutine names -@cindex @file{libgcc.a} - -@c prevent bad page break with this line -Here is an explanation of implicit calls to library routines. - -@defmac DECLARE_LIBRARY_RENAMES -This macro, if defined, should expand to a piece of C code that will get -expanded when compiling functions for libgcc.a. It can be used to -provide alternate names for GCC's internal library functions if there -are ABI-mandated names that the compiler should provide. -@end defmac - -@findex set_optab_libfunc -@findex init_one_libfunc -@deftypefn {Target Hook} void TARGET_INIT_LIBFUNCS (void) -This hook should declare additional library routines or rename -existing ones, using the functions @code{set_optab_libfunc} and -@code{init_one_libfunc} defined in @file{optabs.cc}. -@code{init_optabs} calls this macro after initializing all the normal -library routines. - -The default is to do nothing. Most ports don't need to define this hook. -@end deftypefn - -@deftypevr {Target Hook} bool TARGET_LIBFUNC_GNU_PREFIX -If false (the default), internal library routines start with two -underscores. If set to true, these routines start with @code{__gnu_} -instead. E.g., @code{__muldi3} changes to @code{__gnu_muldi3}. This -currently only affects functions defined in @file{libgcc2.c}. If this -is set to true, the @file{tm.h} file must also -@code{#define LIBGCC2_GNU_PREFIX}. -@end deftypevr - -@defmac FLOAT_LIB_COMPARE_RETURNS_BOOL (@var{mode}, @var{comparison}) -This macro should return @code{true} if the library routine that -implements the floating point comparison operator @var{comparison} in -mode @var{mode} will return a boolean, and @var{false} if it will -return a tristate. - -GCC's own floating point libraries return tristates from the -comparison operators, so the default returns false always. Most ports -don't need to define this macro. -@end defmac - -@defmac TARGET_LIB_INT_CMP_BIASED -This macro should evaluate to @code{true} if the integer comparison -functions (like @code{__cmpdi2}) return 0 to indicate that the first -operand is smaller than the second, 1 to indicate that they are equal, -and 2 to indicate that the first operand is greater than the second. -If this macro evaluates to @code{false} the comparison functions return -@minus{}1, 0, and 1 instead of 0, 1, and 2. If the target uses the routines -in @file{libgcc.a}, you do not need to define this macro. -@end defmac - -@defmac TARGET_HAS_NO_HW_DIVIDE -This macro should be defined if the target has no hardware divide -instructions. If this macro is defined, GCC will use an algorithm which -make use of simple logical and arithmetic operations for 64-bit -division. If the macro is not defined, GCC will use an algorithm which -make use of a 64-bit by 32-bit divide primitive. -@end defmac - -@cindex @code{EDOM}, implicit usage -@findex matherr -@defmac TARGET_EDOM -The value of @code{EDOM} on the target machine, as a C integer constant -expression. If you don't define this macro, GCC does not attempt to -deposit the value of @code{EDOM} into @code{errno} directly. Look in -@file{/usr/include/errno.h} to find the value of @code{EDOM} on your -system. - -If you do not define @code{TARGET_EDOM}, then compiled code reports -domain errors by calling the library function and letting it report the -error. If mathematical functions on your system use @code{matherr} when -there is an error, then you should leave @code{TARGET_EDOM} undefined so -that @code{matherr} is used normally. -@end defmac - -@cindex @code{errno}, implicit usage -@defmac GEN_ERRNO_RTX -Define this macro as a C expression to create an rtl expression that -refers to the global ``variable'' @code{errno}. (On certain systems, -@code{errno} may not actually be a variable.) If you don't define this -macro, a reasonable default is used. -@end defmac - -@deftypefn {Target Hook} bool TARGET_LIBC_HAS_FUNCTION (enum function_class @var{fn_class}, tree @var{type}) -This hook determines whether a function from a class of functions -@var{fn_class} is present in the target C library. If @var{type} is NULL, -the caller asks for support for all standard (float, double, long double) -types. If @var{type} is non-NULL, the caller asks for support for a -specific type. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_LIBC_HAS_FAST_FUNCTION (int @var{fcode}) -This hook determines whether a function from a class of functions -@code{(enum function_class)}@var{fcode} has a fast implementation. -@end deftypefn - -@defmac NEXT_OBJC_RUNTIME -Set this macro to 1 to use the "NeXT" Objective-C message sending conventions -by default. This calling convention involves passing the object, the selector -and the method arguments all at once to the method-lookup library function. -This is the usual setting when targeting Darwin/Mac OS X systems, which have -the NeXT runtime installed. - -If the macro is set to 0, the "GNU" Objective-C message sending convention -will be used by default. This convention passes just the object and the -selector to the method-lookup function, which returns a pointer to the method. - -In either case, it remains possible to select code-generation for the alternate -scheme, by means of compiler command line switches. -@end defmac - -@node Addressing Modes -@section Addressing Modes -@cindex addressing modes - -@c prevent bad page break with this line -This is about addressing modes. - -@defmac HAVE_PRE_INCREMENT -@defmacx HAVE_PRE_DECREMENT -@defmacx HAVE_POST_INCREMENT -@defmacx HAVE_POST_DECREMENT -A C expression that is nonzero if the machine supports pre-increment, -pre-decrement, post-increment, or post-decrement addressing respectively. -@end defmac - -@defmac HAVE_PRE_MODIFY_DISP -@defmacx HAVE_POST_MODIFY_DISP -A C expression that is nonzero if the machine supports pre- or -post-address side-effect generation involving constants other than -the size of the memory operand. -@end defmac - -@defmac HAVE_PRE_MODIFY_REG -@defmacx HAVE_POST_MODIFY_REG -A C expression that is nonzero if the machine supports pre- or -post-address side-effect generation involving a register displacement. -@end defmac - -@defmac CONSTANT_ADDRESS_P (@var{x}) -A C expression that is 1 if the RTX @var{x} is a constant which -is a valid address. On most machines the default definition of -@code{(CONSTANT_P (@var{x}) && GET_CODE (@var{x}) != CONST_DOUBLE)} -is acceptable, but a few machines are more restrictive as to which -constant addresses are supported. -@end defmac - -@defmac CONSTANT_P (@var{x}) -@code{CONSTANT_P}, which is defined by target-independent code, -accepts integer-values expressions whose values are not explicitly -known, such as @code{symbol_ref}, @code{label_ref}, and @code{high} -expressions and @code{const} arithmetic expressions, in addition to -@code{const_int} and @code{const_double} expressions. -@end defmac - -@defmac MAX_REGS_PER_ADDRESS -A number, the maximum number of registers that can appear in a valid -memory address. Note that it is up to you to specify a value equal to -the maximum number that @code{TARGET_LEGITIMATE_ADDRESS_P} would ever -accept. -@end defmac - -@deftypefn {Target Hook} bool TARGET_LEGITIMATE_ADDRESS_P (machine_mode @var{mode}, rtx @var{x}, bool @var{strict}) -A function that returns whether @var{x} (an RTX) is a legitimate memory -address on the target machine for a memory operand of mode @var{mode}. - -Legitimate addresses are defined in two variants: a strict variant and a -non-strict one. The @var{strict} parameter chooses which variant is -desired by the caller. - -The strict variant is used in the reload pass. It must be defined so -that any pseudo-register that has not been allocated a hard register is -considered a memory reference. This is because in contexts where some -kind of register is required, a pseudo-register with no hard register -must be rejected. For non-hard registers, the strict variant should look -up the @code{reg_renumber} array; it should then proceed using the hard -register number in the array, or treat the pseudo as a memory reference -if the array holds @code{-1}. - -The non-strict variant is used in other passes. It must be defined to -accept all pseudo-registers in every context where some kind of -register is required. - -Normally, constant addresses which are the sum of a @code{symbol_ref} -and an integer are stored inside a @code{const} RTX to mark them as -constant. Therefore, there is no need to recognize such sums -specifically as legitimate addresses. Normally you would simply -recognize any @code{const} as legitimate. - -Usually @code{PRINT_OPERAND_ADDRESS} is not prepared to handle constant -sums that are not marked with @code{const}. It assumes that a naked -@code{plus} indicates indexing. If so, then you @emph{must} reject such -naked constant sums as illegitimate addresses, so that none of them will -be given to @code{PRINT_OPERAND_ADDRESS}. - -@cindex @code{TARGET_ENCODE_SECTION_INFO} and address validation -On some machines, whether a symbolic address is legitimate depends on -the section that the address refers to. On these machines, define the -target hook @code{TARGET_ENCODE_SECTION_INFO} to store the information -into the @code{symbol_ref}, and then check for it here. When you see a -@code{const}, you will have to look inside it to find the -@code{symbol_ref} in order to determine the section. @xref{Assembler -Format}. - -@cindex @code{GO_IF_LEGITIMATE_ADDRESS} -Some ports are still using a deprecated legacy substitute for -this hook, the @code{GO_IF_LEGITIMATE_ADDRESS} macro. This macro -has this syntax: - -@example -#define GO_IF_LEGITIMATE_ADDRESS (@var{mode}, @var{x}, @var{label}) -@end example - -@noindent -and should @code{goto @var{label}} if the address @var{x} is a valid -address on the target machine for a memory operand of mode @var{mode}. - -@findex REG_OK_STRICT -Compiler source files that want to use the strict variant of this -macro define the macro @code{REG_OK_STRICT}. You should use an -@code{#ifdef REG_OK_STRICT} conditional to define the strict variant in -that case and the non-strict variant otherwise. - -Using the hook is usually simpler because it limits the number of -files that are recompiled when changes are made. -@end deftypefn - -@defmac TARGET_MEM_CONSTRAINT -A single character to be used instead of the default @code{'m'} -character for general memory addresses. This defines the constraint -letter which matches the memory addresses accepted by -@code{TARGET_LEGITIMATE_ADDRESS_P}. Define this macro if you want to -support new address formats in your back end without changing the -semantics of the @code{'m'} constraint. This is necessary in order to -preserve functionality of inline assembly constructs using the -@code{'m'} constraint. -@end defmac - -@defmac FIND_BASE_TERM (@var{x}) -A C expression to determine the base term of address @var{x}, -or to provide a simplified version of @var{x} from which @file{alias.cc} -can easily find the base term. This macro is used in only two places: -@code{find_base_value} and @code{find_base_term} in @file{alias.cc}. - -It is always safe for this macro to not be defined. It exists so -that alias analysis can understand machine-dependent addresses. - -The typical use of this macro is to handle addresses containing -a label_ref or symbol_ref within an UNSPEC@. -@end defmac - -@deftypefn {Target Hook} rtx TARGET_LEGITIMIZE_ADDRESS (rtx @var{x}, rtx @var{oldx}, machine_mode @var{mode}) -This hook is given an invalid memory address @var{x} for an -operand of mode @var{mode} and should try to return a valid memory -address. - -@findex break_out_memory_refs -@var{x} will always be the result of a call to @code{break_out_memory_refs}, -and @var{oldx} will be the operand that was given to that function to produce -@var{x}. - -The code of the hook should not alter the substructure of -@var{x}. If it transforms @var{x} into a more legitimate form, it -should return the new @var{x}. - -It is not necessary for this hook to come up with a legitimate address, -with the exception of native TLS addresses (@pxref{Emulated TLS}). -The compiler has standard ways of doing so in all cases. In fact, if -the target supports only emulated TLS, it -is safe to omit this hook or make it return @var{x} if it cannot find -a valid way to legitimize the address. But often a machine-dependent -strategy can generate better code. -@end deftypefn - -@defmac LEGITIMIZE_RELOAD_ADDRESS (@var{x}, @var{mode}, @var{opnum}, @var{type}, @var{ind_levels}, @var{win}) -A C compound statement that attempts to replace @var{x}, which is an address -that needs reloading, with a valid memory address for an operand of mode -@var{mode}. @var{win} will be a C statement label elsewhere in the code. -It is not necessary to define this macro, but it might be useful for -performance reasons. - -For example, on the i386, it is sometimes possible to use a single -reload register instead of two by reloading a sum of two pseudo -registers into a register. On the other hand, for number of RISC -processors offsets are limited so that often an intermediate address -needs to be generated in order to address a stack slot. By defining -@code{LEGITIMIZE_RELOAD_ADDRESS} appropriately, the intermediate addresses -generated for adjacent some stack slots can be made identical, and thus -be shared. - -@emph{Note}: This macro should be used with caution. It is necessary -to know something of how reload works in order to effectively use this, -and it is quite easy to produce macros that build in too much knowledge -of reload internals. - -@emph{Note}: This macro must be able to reload an address created by a -previous invocation of this macro. If it fails to handle such addresses -then the compiler may generate incorrect code or abort. - -@findex push_reload -The macro definition should use @code{push_reload} to indicate parts that -need reloading; @var{opnum}, @var{type} and @var{ind_levels} are usually -suitable to be passed unaltered to @code{push_reload}. - -The code generated by this macro must not alter the substructure of -@var{x}. If it transforms @var{x} into a more legitimate form, it -should assign @var{x} (which will always be a C variable) a new value. -This also applies to parts that you change indirectly by calling -@code{push_reload}. - -@findex strict_memory_address_p -The macro definition may use @code{strict_memory_address_p} to test if -the address has become legitimate. - -@findex copy_rtx -If you want to change only a part of @var{x}, one standard way of doing -this is to use @code{copy_rtx}. Note, however, that it unshares only a -single level of rtl. Thus, if the part to be changed is not at the -top level, you'll need to replace first the top level. -It is not necessary for this macro to come up with a legitimate -address; but often a machine-dependent strategy can generate better code. -@end defmac - -@deftypefn {Target Hook} bool TARGET_MODE_DEPENDENT_ADDRESS_P (const_rtx @var{addr}, addr_space_t @var{addrspace}) -This hook returns @code{true} if memory address @var{addr} in address -space @var{addrspace} can have -different meanings depending on the machine mode of the memory -reference it is used for or if the address is valid for some modes -but not others. - -Autoincrement and autodecrement addresses typically have mode-dependent -effects because the amount of the increment or decrement is the size -of the operand being addressed. Some machines have other mode-dependent -addresses. Many RISC machines have no mode-dependent addresses. - -You may assume that @var{addr} is a valid address for the machine. - -The default version of this hook returns @code{false}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_LEGITIMATE_CONSTANT_P (machine_mode @var{mode}, rtx @var{x}) -This hook returns true if @var{x} is a legitimate constant for a -@var{mode}-mode immediate operand on the target machine. You can assume that -@var{x} satisfies @code{CONSTANT_P}, so you need not check this. - -The default definition returns true. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_PRECOMPUTE_TLS_P (machine_mode @var{mode}, rtx @var{x}) -This hook returns true if @var{x} is a TLS operand on the target -machine that should be pre-computed when used as the argument in a call. -You can assume that @var{x} satisfies @code{CONSTANT_P}, so you need not -check this. - -The default definition returns false. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_DELEGITIMIZE_ADDRESS (rtx @var{x}) -This hook is used to undo the possibly obfuscating effects of the -@code{LEGITIMIZE_ADDRESS} and @code{LEGITIMIZE_RELOAD_ADDRESS} target -macros. Some backend implementations of these macros wrap symbol -references inside an @code{UNSPEC} rtx to represent PIC or similar -addressing modes. This target hook allows GCC's optimizers to understand -the semantics of these opaque @code{UNSPEC}s by converting them back -into their original form. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CONST_NOT_OK_FOR_DEBUG_P (rtx @var{x}) -This hook should return true if @var{x} should not be emitted into -debug sections. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CANNOT_FORCE_CONST_MEM (machine_mode @var{mode}, rtx @var{x}) -This hook should return true if @var{x} is of a form that cannot (or -should not) be spilled to the constant pool. @var{mode} is the mode -of @var{x}. - -The default version of this hook returns false. - -The primary reason to define this hook is to prevent reload from -deciding that a non-legitimate constant would be better reloaded -from the constant pool instead of spilling and reloading a register -holding the constant. This restriction is often true of addresses -of TLS symbols for various targets. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_USE_BLOCKS_FOR_CONSTANT_P (machine_mode @var{mode}, const_rtx @var{x}) -This hook should return true if pool entries for constant @var{x} can -be placed in an @code{object_block} structure. @var{mode} is the mode -of @var{x}. - -The default version returns false for all constants. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_USE_BLOCKS_FOR_DECL_P (const_tree @var{decl}) -This hook should return true if pool entries for @var{decl} should -be placed in an @code{object_block} structure. - -The default version returns true for all decls. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_BUILTIN_RECIPROCAL (tree @var{fndecl}) -This hook should return the DECL of a function that implements the -reciprocal of the machine-specific builtin function @var{fndecl}, or -@code{NULL_TREE} if such a function is not available. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_VECTORIZE_BUILTIN_MASK_FOR_LOAD (void) -This hook should return the DECL of a function @var{f} that given an -address @var{addr} as an argument returns a mask @var{m} that can be -used to extract from two vectors the relevant data that resides in -@var{addr} in case @var{addr} is not properly aligned. - -The autovectorizer, when vectorizing a load operation from an address -@var{addr} that may be unaligned, will generate two vector loads from -the two aligned addresses around @var{addr}. It then generates a -@code{REALIGN_LOAD} operation to extract the relevant data from the -two loaded vectors. The first two arguments to @code{REALIGN_LOAD}, -@var{v1} and @var{v2}, are the two vectors, each of size @var{VS}, and -the third argument, @var{OFF}, defines how the data will be extracted -from these two vectors: if @var{OFF} is 0, then the returned vector is -@var{v2}; otherwise, the returned vector is composed from the last -@var{VS}-@var{OFF} elements of @var{v1} concatenated to the first -@var{OFF} elements of @var{v2}. - -If this hook is defined, the autovectorizer will generate a call -to @var{f} (using the DECL tree that this hook returns) and will -use the return value of @var{f} as the argument @var{OFF} to -@code{REALIGN_LOAD}. Therefore, the mask @var{m} returned by @var{f} -should comply with the semantics expected by @code{REALIGN_LOAD} -described above. -If this hook is not defined, then @var{addr} will be used as -the argument @var{OFF} to @code{REALIGN_LOAD}, in which case the low -log2(@var{VS}) @minus{} 1 bits of @var{addr} will be considered. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_VECTORIZE_BUILTIN_VECTORIZATION_COST (enum vect_cost_for_stmt @var{type_of_cost}, tree @var{vectype}, int @var{misalign}) -Returns cost of different scalar or vector statements for vectorization cost model. -For vector memory operations the cost may depend on type (@var{vectype}) and -misalignment value (@var{misalign}). -@end deftypefn - -@deftypefn {Target Hook} poly_uint64 TARGET_VECTORIZE_PREFERRED_VECTOR_ALIGNMENT (const_tree @var{type}) -This hook returns the preferred alignment in bits for accesses to -vectors of type @var{type} in vectorized code. This might be less than -or greater than the ABI-defined value returned by -@code{TARGET_VECTOR_ALIGNMENT}. It can be equal to the alignment of -a single element, in which case the vectorizer will not try to optimize -for alignment. - -The default hook returns @code{TYPE_ALIGN (@var{type})}, which is -correct for most targets. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_VECTORIZE_VECTOR_ALIGNMENT_REACHABLE (const_tree @var{type}, bool @var{is_packed}) -Return true if vector alignment is reachable (by peeling N iterations) -for the given scalar type @var{type}. @var{is_packed} is false if the scalar -access using @var{type} is known to be naturally aligned. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_VECTORIZE_VEC_PERM_CONST (machine_mode @var{mode}, machine_mode @var{op_mode}, rtx @var{output}, rtx @var{in0}, rtx @var{in1}, const vec_perm_indices @var{&sel}) -This hook is used to test whether the target can permute up to two -vectors of mode @var{op_mode} using the permutation vector @code{sel}, -producing a vector of mode @var{mode}. The hook is also used to emit such -a permutation. - -When the hook is being used to test whether the target supports a permutation, -@var{in0}, @var{in1}, and @var{out} are all null. When the hook is being used -to emit a permutation, @var{in0} and @var{in1} are the source vectors of mode -@var{op_mode} and @var{out} is the destination vector of mode @var{mode}. -@var{in1} is the same as @var{in0} if @var{sel} describes a permutation on one -vector instead of two. - -Return true if the operation is possible, emitting instructions for it -if rtxes are provided. - -@cindex @code{vec_perm@var{m}} instruction pattern -If the hook returns false for a mode with multibyte elements, GCC will -try the equivalent byte operation. If that also fails, it will try forcing -the selector into a register and using the @var{vec_perm@var{mode}} -instruction pattern. There is no need for the hook to handle these two -implementation approaches itself. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_VECTORIZE_BUILTIN_VECTORIZED_FUNCTION (unsigned @var{code}, tree @var{vec_type_out}, tree @var{vec_type_in}) -This hook should return the decl of a function that implements the -vectorized variant of the function with the @code{combined_fn} code -@var{code} or @code{NULL_TREE} if such a function is not available. -The return type of the vectorized function shall be of vector type -@var{vec_type_out} and the argument types should be @var{vec_type_in}. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_VECTORIZE_BUILTIN_MD_VECTORIZED_FUNCTION (tree @var{fndecl}, tree @var{vec_type_out}, tree @var{vec_type_in}) -This hook should return the decl of a function that implements the -vectorized variant of target built-in function @code{fndecl}. The -return type of the vectorized function shall be of vector type -@var{vec_type_out} and the argument types should be @var{vec_type_in}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_VECTORIZE_SUPPORT_VECTOR_MISALIGNMENT (machine_mode @var{mode}, const_tree @var{type}, int @var{misalignment}, bool @var{is_packed}) -This hook should return true if the target supports misaligned vector -store/load of a specific factor denoted in the @var{misalignment} -parameter. The vector store/load should be of machine mode @var{mode} and -the elements in the vectors should be of type @var{type}. @var{is_packed} -parameter is true if the memory access is defined in a packed struct. -@end deftypefn - -@deftypefn {Target Hook} machine_mode TARGET_VECTORIZE_PREFERRED_SIMD_MODE (scalar_mode @var{mode}) -This hook should return the preferred mode for vectorizing scalar -mode @var{mode}. The default is -equal to @code{word_mode}, because the vectorizer can do some -transformations even in absence of specialized @acronym{SIMD} hardware. -@end deftypefn - -@deftypefn {Target Hook} machine_mode TARGET_VECTORIZE_SPLIT_REDUCTION (machine_mode) -This hook should return the preferred mode to split the final reduction -step on @var{mode} to. The reduction is then carried out reducing upper -against lower halves of vectors recursively until the specified mode is -reached. The default is @var{mode} which means no splitting. -@end deftypefn - -@deftypefn {Target Hook} {unsigned int} TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_MODES (vector_modes *@var{modes}, bool @var{all}) -If using the mode returned by @code{TARGET_VECTORIZE_PREFERRED_SIMD_MODE} -is not the only approach worth considering, this hook should add one mode to -@var{modes} for each useful alternative approach. These modes are then -passed to @code{TARGET_VECTORIZE_RELATED_MODE} to obtain the vector mode -for a given element mode. - -The modes returned in @var{modes} should use the smallest element mode -possible for the vectorization approach that they represent, preferring -integer modes over floating-poing modes in the event of a tie. The first -mode should be the @code{TARGET_VECTORIZE_PREFERRED_SIMD_MODE} for its -element mode. - -If @var{all} is true, add suitable vector modes even when they are generally -not expected to be worthwhile. - -The hook returns a bitmask of flags that control how the modes in -@var{modes} are used. The flags are: -@table @code -@item VECT_COMPARE_COSTS -Tells the loop vectorizer to try all the provided modes and pick the one -with the lowest cost. By default the vectorizer will choose the first -mode that works. -@end table - -The hook does not need to do anything if the vector returned by -@code{TARGET_VECTORIZE_PREFERRED_SIMD_MODE} is the only one relevant -for autovectorization. The default implementation adds no modes and -returns 0. -@end deftypefn - -@deftypefn {Target Hook} opt_machine_mode TARGET_VECTORIZE_RELATED_MODE (machine_mode @var{vector_mode}, scalar_mode @var{element_mode}, poly_uint64 @var{nunits}) -If a piece of code is using vector mode @var{vector_mode} and also wants -to operate on elements of mode @var{element_mode}, return the vector mode -it should use for those elements. If @var{nunits} is nonzero, ensure that -the mode has exactly @var{nunits} elements, otherwise pick whichever vector -size pairs the most naturally with @var{vector_mode}. Return an empty -@code{opt_machine_mode} if there is no supported vector mode with the -required properties. - -There is no prescribed way of handling the case in which @var{nunits} -is zero. One common choice is to pick a vector mode with the same size -as @var{vector_mode}; this is the natural choice if the target has a -fixed vector size. Another option is to choose a vector mode with the -same number of elements as @var{vector_mode}; this is the natural choice -if the target has a fixed number of elements. Alternatively, the hook -might choose a middle ground, such as trying to keep the number of -elements as similar as possible while applying maximum and minimum -vector sizes. - -The default implementation uses @code{mode_for_vector} to find the -requested mode, returning a mode with the same size as @var{vector_mode} -when @var{nunits} is zero. This is the correct behavior for most targets. -@end deftypefn - -@deftypefn {Target Hook} opt_machine_mode TARGET_VECTORIZE_GET_MASK_MODE (machine_mode @var{mode}) -Return the mode to use for a vector mask that holds one boolean -result for each element of vector mode @var{mode}. The returned mask mode -can be a vector of integers (class @code{MODE_VECTOR_INT}), a vector of -booleans (class @code{MODE_VECTOR_BOOL}) or a scalar integer (class -@code{MODE_INT}). Return an empty @code{opt_machine_mode} if no such -mask mode exists. - -The default implementation returns a @code{MODE_VECTOR_INT} with the -same size and number of elements as @var{mode}, if such a mode exists. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_VECTORIZE_EMPTY_MASK_IS_EXPENSIVE (unsigned @var{ifn}) -This hook returns true if masked internal function @var{ifn} (really of -type @code{internal_fn}) should be considered expensive when the mask is -all zeros. GCC can then try to branch around the instruction instead. -@end deftypefn - -@deftypefn {Target Hook} {class vector_costs *} TARGET_VECTORIZE_CREATE_COSTS (vec_info *@var{vinfo}, bool @var{costing_for_scalar}) -This hook should initialize target-specific data structures in preparation -for modeling the costs of vectorizing a loop or basic block. The default -allocates three unsigned integers for accumulating costs for the prologue, -body, and epilogue of the loop or basic block. If @var{loop_info} is -non-NULL, it identifies the loop being vectorized; otherwise a single block -is being vectorized. If @var{costing_for_scalar} is true, it indicates the -current cost model is for the scalar version of a loop or block; otherwise -it is for the vector version. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_VECTORIZE_BUILTIN_GATHER (const_tree @var{mem_vectype}, const_tree @var{index_type}, int @var{scale}) -Target builtin that implements vector gather operation. @var{mem_vectype} -is the vector type of the load and @var{index_type} is scalar type of -the index, scaled by @var{scale}. -The default is @code{NULL_TREE} which means to not vectorize gather -loads. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_VECTORIZE_BUILTIN_SCATTER (const_tree @var{vectype}, const_tree @var{index_type}, int @var{scale}) -Target builtin that implements vector scatter operation. @var{vectype} -is the vector type of the store and @var{index_type} is scalar type of -the index, scaled by @var{scale}. -The default is @code{NULL_TREE} which means to not vectorize scatter -stores. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SIMD_CLONE_COMPUTE_VECSIZE_AND_SIMDLEN (struct cgraph_node *@var{}, struct cgraph_simd_clone *@var{}, @var{tree}, @var{int}) -This hook should set @var{vecsize_mangle}, @var{vecsize_int}, @var{vecsize_float} -fields in @var{simd_clone} structure pointed by @var{clone_info} argument and also -@var{simdlen} field if it was previously 0. -@var{vecsize_mangle} is a marker for the backend only. @var{vecsize_int} and -@var{vecsize_float} should be left zero on targets where the number of lanes is -not determined by the bitsize (in which case @var{simdlen} is always used). -The hook should return 0 if SIMD clones shouldn't be emitted, -or number of @var{vecsize_mangle} variants that should be emitted. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SIMD_CLONE_ADJUST (struct cgraph_node *@var{}) -This hook should add implicit @code{attribute(target("..."))} attribute -to SIMD clone @var{node} if needed. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SIMD_CLONE_USABLE (struct cgraph_node *@var{}) -This hook should return -1 if SIMD clone @var{node} shouldn't be used -in vectorized loops in current function, or non-negative number if it is -usable. In that case, the smaller the number is, the more desirable it is -to use it. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SIMT_VF (void) -Return number of threads in SIMT thread group on the target. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_OMP_DEVICE_KIND_ARCH_ISA (enum omp_device_kind_arch_isa @var{trait}, const char *@var{name}) -Return 1 if @var{trait} @var{name} is present in the OpenMP context's -device trait set, return 0 if not present in any OpenMP context in the -whole translation unit, or -1 if not present in the current OpenMP context -but might be present in another OpenMP context in the same TU. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_GOACC_VALIDATE_DIMS (tree @var{decl}, int *@var{dims}, int @var{fn_level}, unsigned @var{used}) -This hook should check the launch dimensions provided for an OpenACC -compute region, or routine. Defaulted values are represented as -1 -and non-constant values as 0. The @var{fn_level} is negative for the -function corresponding to the compute region. For a routine it is the -outermost level at which partitioned execution may be spawned. The hook -should verify non-default values. If DECL is NULL, global defaults -are being validated and unspecified defaults should be filled in. -Diagnostics should be issued as appropriate. Return -true, if changes have been made. You must override this hook to -provide dimensions larger than 1. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_GOACC_DIM_LIMIT (int @var{axis}) -This hook should return the maximum size of a particular dimension, -or zero if unbounded. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_GOACC_FORK_JOIN (gcall *@var{call}, const int *@var{dims}, bool @var{is_fork}) -This hook can be used to convert IFN_GOACC_FORK and IFN_GOACC_JOIN -function calls to target-specific gimple, or indicate whether they -should be retained. It is executed during the oacc_device_lower pass. -It should return true, if the call should be retained. It should -return false, if it is to be deleted (either because target-specific -gimple has been inserted before it, or there is no need for it). -The default hook returns false, if there are no RTL expanders for them. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_GOACC_REDUCTION (gcall *@var{call}) -This hook is used by the oacc_transform pass to expand calls to the -@var{GOACC_REDUCTION} internal function, into a sequence of gimple -instructions. @var{call} is gimple statement containing the call to -the function. This hook removes statement @var{call} after the -expanded sequence has been inserted. This hook is also responsible -for allocating any storage for reductions when necessary. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_PREFERRED_ELSE_VALUE (unsigned @var{ifn}, tree @var{type}, unsigned @var{nops}, tree *@var{ops}) -This hook returns the target's preferred final argument for a call -to conditional internal function @var{ifn} (really of type -@code{internal_fn}). @var{type} specifies the return type of the -function and @var{ops} are the operands to the conditional operation, -of which there are @var{nops}. - -For example, if @var{ifn} is @code{IFN_COND_ADD}, the hook returns -a value of type @var{type} that should be used when @samp{@var{ops}[0]} -and @samp{@var{ops}[1]} are conditionally added together. - -This hook is only relevant if the target supports conditional patterns -like @code{cond_add@var{m}}. The default implementation returns a zero -constant of type @var{type}. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_GOACC_ADJUST_PRIVATE_DECL (location_t @var{loc}, tree @var{var}, int @var{level}) -This hook, if defined, is used by accelerator target back-ends to adjust -OpenACC variable declarations that should be made private to the given -parallelism level (i.e. @code{GOMP_DIM_GANG}, @code{GOMP_DIM_WORKER} or -@code{GOMP_DIM_VECTOR}). A typical use for this hook is to force variable -declarations at the @code{gang} level to reside in GPU shared memory. -@var{loc} may be used for diagnostic purposes. - -You may also use the @code{TARGET_GOACC_EXPAND_VAR_DECL} hook if the -adjusted variable declaration needs to be expanded to RTL in a non-standard -way. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_GOACC_EXPAND_VAR_DECL (tree @var{var}) -This hook, if defined, is used by accelerator target back-ends to expand -specially handled kinds of @code{VAR_DECL} expressions. A particular use is -to place variables with specific attributes inside special accelarator -memories. A return value of @code{NULL} indicates that the target does not -handle this @code{VAR_DECL}, and normal RTL expanding is resumed. - -Only define this hook if your accelerator target needs to expand certain -@code{VAR_DECL} nodes in a way that differs from the default. You can also adjust -private variables at OpenACC device-lowering time using the -@code{TARGET_GOACC_ADJUST_PRIVATE_DECL} target hook. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_GOACC_CREATE_WORKER_BROADCAST_RECORD (tree @var{rec}, bool @var{sender}, const char *@var{name}, unsigned HOST_WIDE_INT @var{offset}) -Create a record used to propagate local-variable state from an active -worker to other workers. A possible implementation might adjust the type -of REC to place the new variable in shared GPU memory. - -Presence of this target hook indicates that middle end neutering/broadcasting -be used. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_GOACC_SHARED_MEM_LAYOUT (unsigned HOST_WIDE_INT *@var{}, unsigned HOST_WIDE_INT *@var{}, @var{int[]}, unsigned @var{HOST_WIDE_INT[]}, unsigned @var{HOST_WIDE_INT[]}) -Lay out a fixed shared-memory region on the target. The LO and HI -arguments should be set to a range of addresses that can be used for worker -broadcasting. The dimensions, reduction size and gang-private size -arguments are for the current offload region. -@end deftypefn - -@node Anchored Addresses -@section Anchored Addresses -@cindex anchored addresses -@cindex @option{-fsection-anchors} - -GCC usually addresses every static object as a separate entity. -For example, if we have: - -@smallexample -static int a, b, c; -int foo (void) @{ return a + b + c; @} -@end smallexample - -the code for @code{foo} will usually calculate three separate symbolic -addresses: those of @code{a}, @code{b} and @code{c}. On some targets, -it would be better to calculate just one symbolic address and access -the three variables relative to it. The equivalent pseudocode would -be something like: - -@smallexample -int foo (void) -@{ - register int *xr = &x; - return xr[&a - &x] + xr[&b - &x] + xr[&c - &x]; -@} -@end smallexample - -(which isn't valid C). We refer to shared addresses like @code{x} as -``section anchors''. Their use is controlled by @option{-fsection-anchors}. - -The hooks below describe the target properties that GCC needs to know -in order to make effective use of section anchors. It won't use -section anchors at all unless either @code{TARGET_MIN_ANCHOR_OFFSET} -or @code{TARGET_MAX_ANCHOR_OFFSET} is set to a nonzero value. - -@deftypevr {Target Hook} HOST_WIDE_INT TARGET_MIN_ANCHOR_OFFSET -The minimum offset that should be applied to a section anchor. -On most targets, it should be the smallest offset that can be -applied to a base register while still giving a legitimate address -for every mode. The default value is 0. -@end deftypevr - -@deftypevr {Target Hook} HOST_WIDE_INT TARGET_MAX_ANCHOR_OFFSET -Like @code{TARGET_MIN_ANCHOR_OFFSET}, but the maximum (inclusive) -offset that should be applied to section anchors. The default -value is 0. -@end deftypevr - -@deftypefn {Target Hook} void TARGET_ASM_OUTPUT_ANCHOR (rtx @var{x}) -Write the assembly code to define section anchor @var{x}, which is a -@code{SYMBOL_REF} for which @samp{SYMBOL_REF_ANCHOR_P (@var{x})} is true. -The hook is called with the assembly output position set to the beginning -of @code{SYMBOL_REF_BLOCK (@var{x})}. - -If @code{ASM_OUTPUT_DEF} is available, the hook's default definition uses -it to define the symbol as @samp{. + SYMBOL_REF_BLOCK_OFFSET (@var{x})}. -If @code{ASM_OUTPUT_DEF} is not available, the hook's default definition -is @code{NULL}, which disables the use of section anchors altogether. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_USE_ANCHORS_FOR_SYMBOL_P (const_rtx @var{x}) -Return true if GCC should attempt to use anchors to access @code{SYMBOL_REF} -@var{x}. You can assume @samp{SYMBOL_REF_HAS_BLOCK_INFO_P (@var{x})} and -@samp{!SYMBOL_REF_ANCHOR_P (@var{x})}. - -The default version is correct for most targets, but you might need to -intercept this hook to handle things like target-specific attributes -or target-specific sections. -@end deftypefn - -@node Condition Code -@section Condition Code Status -@cindex condition code status - -Condition codes in GCC are represented as registers, -which provides better schedulability for -architectures that do have a condition code register, but on which -most instructions do not affect it. The latter category includes -most RISC machines. - -Implicit clobbering would pose a strong restriction on the placement of -the definition and use of the condition code. In the past the definition -and use were always adjacent. However, recent changes to support trapping -arithmetic may result in the definition and user being in different blocks. -Thus, there may be a @code{NOTE_INSN_BASIC_BLOCK} between them. Additionally, -the definition may be the source of exception handling edges. - -These restrictions can prevent important -optimizations on some machines. For example, on the IBM RS/6000, there -is a delay for taken branches unless the condition code register is set -three instructions earlier than the conditional branch. The instruction -scheduler cannot perform this optimization if it is not permitted to -separate the definition and use of the condition code register. - -If there is a specific -condition code register in the machine, use a hard register. If the -condition code or comparison result can be placed in any general register, -or if there are multiple condition registers, use a pseudo register. -Registers used to store the condition code value will usually have a mode -that is in class @code{MODE_CC}. - -Alternatively, you can use @code{BImode} if the comparison operator is -specified already in the compare instruction. In this case, you are not -interested in most macros in this section. - -@menu -* MODE_CC Condition Codes:: Modern representation of condition codes. -@end menu - -@node MODE_CC Condition Codes -@subsection Representation of condition codes using registers -@findex CCmode -@findex MODE_CC - -@defmac SELECT_CC_MODE (@var{op}, @var{x}, @var{y}) -On many machines, the condition code may be produced by other instructions -than compares, for example the branch can use directly the condition -code set by a subtract instruction. However, on some machines -when the condition code is set this way some bits (such as the overflow -bit) are not set in the same way as a test instruction, so that a different -branch instruction must be used for some conditional branches. When -this happens, use the machine mode of the condition code register to -record different formats of the condition code register. Modes can -also be used to record which compare instruction (e.g.@: a signed or an -unsigned comparison) produced the condition codes. - -If other modes than @code{CCmode} are required, add them to -@file{@var{machine}-modes.def} and define @code{SELECT_CC_MODE} to choose -a mode given an operand of a compare. This is needed because the modes -have to be chosen not only during RTL generation but also, for example, -by instruction combination. The result of @code{SELECT_CC_MODE} should -be consistent with the mode used in the patterns; for example to support -the case of the add on the SPARC discussed above, we have the pattern - -@smallexample -(define_insn "" - [(set (reg:CCNZ 0) - (compare:CCNZ - (plus:SI (match_operand:SI 0 "register_operand" "%r") - (match_operand:SI 1 "arith_operand" "rI")) - (const_int 0)))] - "" - "@dots{}") -@end smallexample - -@noindent -together with a @code{SELECT_CC_MODE} that returns @code{CCNZmode} -for comparisons whose argument is a @code{plus}: - -@smallexample -#define SELECT_CC_MODE(OP,X,Y) \ - (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT \ - ? ((OP == LT || OP == LE || OP == GT || OP == GE) \ - ? CCFPEmode : CCFPmode) \ - : ((GET_CODE (X) == PLUS || GET_CODE (X) == MINUS \ - || GET_CODE (X) == NEG || GET_CODE (x) == ASHIFT) \ - ? CCNZmode : CCmode)) -@end smallexample - -Another reason to use modes is to retain information on which operands -were used by the comparison; see @code{REVERSIBLE_CC_MODE} later in -this section. - -You should define this macro if and only if you define extra CC modes -in @file{@var{machine}-modes.def}. -@end defmac - -@deftypefn {Target Hook} void TARGET_CANONICALIZE_COMPARISON (int *@var{code}, rtx *@var{op0}, rtx *@var{op1}, bool @var{op0_preserve_value}) -On some machines not all possible comparisons are defined, but you can -convert an invalid comparison into a valid one. For example, the Alpha -does not have a @code{GT} comparison, but you can use an @code{LT} -comparison instead and swap the order of the operands. - -On such machines, implement this hook to do any required conversions. -@var{code} is the initial comparison code and @var{op0} and @var{op1} -are the left and right operands of the comparison, respectively. If -@var{op0_preserve_value} is @code{true} the implementation is not -allowed to change the value of @var{op0} since the value might be used -in RTXs which aren't comparisons. E.g. the implementation is not -allowed to swap operands in that case. - -GCC will not assume that the comparison resulting from this macro is -valid but will see if the resulting insn matches a pattern in the -@file{md} file. - -You need not to implement this hook if it would never change the -comparison code or operands. -@end deftypefn - -@defmac REVERSIBLE_CC_MODE (@var{mode}) -A C expression whose value is one if it is always safe to reverse a -comparison whose mode is @var{mode}. If @code{SELECT_CC_MODE} -can ever return @var{mode} for a floating-point inequality comparison, -then @code{REVERSIBLE_CC_MODE (@var{mode})} must be zero. - -You need not define this macro if it would always returns zero or if the -floating-point format is anything other than @code{IEEE_FLOAT_FORMAT}. -For example, here is the definition used on the SPARC, where floating-point -inequality comparisons are given either @code{CCFPEmode} or @code{CCFPmode}: - -@smallexample -#define REVERSIBLE_CC_MODE(MODE) \ - ((MODE) != CCFPEmode && (MODE) != CCFPmode) -@end smallexample -@end defmac - -@defmac REVERSE_CONDITION (@var{code}, @var{mode}) -A C expression whose value is reversed condition code of the @var{code} for -comparison done in CC_MODE @var{mode}. The macro is used only in case -@code{REVERSIBLE_CC_MODE (@var{mode})} is nonzero. Define this macro in case -machine has some non-standard way how to reverse certain conditionals. For -instance in case all floating point conditions are non-trapping, compiler may -freely convert unordered compares to ordered ones. Then definition may look -like: - -@smallexample -#define REVERSE_CONDITION(CODE, MODE) \ - ((MODE) != CCFPmode ? reverse_condition (CODE) \ - : reverse_condition_maybe_unordered (CODE)) -@end smallexample -@end defmac - -@deftypefn {Target Hook} bool TARGET_FIXED_CONDITION_CODE_REGS (unsigned int *@var{p1}, unsigned int *@var{p2}) -On targets which use a hard -register rather than a pseudo-register to hold condition codes, the -regular CSE passes are often not able to identify cases in which the -hard register is set to a common value. Use this hook to enable a -small pass which optimizes such cases. This hook should return true -to enable this pass, and it should set the integers to which its -arguments point to the hard register numbers used for condition codes. -When there is only one such register, as is true on most systems, the -integer pointed to by @var{p2} should be set to -@code{INVALID_REGNUM}. - -The default version of this hook returns false. -@end deftypefn - -@deftypefn {Target Hook} machine_mode TARGET_CC_MODES_COMPATIBLE (machine_mode @var{m1}, machine_mode @var{m2}) -On targets which use multiple condition code modes in class -@code{MODE_CC}, it is sometimes the case that a comparison can be -validly done in more than one mode. On such a system, define this -target hook to take two mode arguments and to return a mode in which -both comparisons may be validly done. If there is no such mode, -return @code{VOIDmode}. - -The default version of this hook checks whether the modes are the -same. If they are, it returns that mode. If they are different, it -returns @code{VOIDmode}. -@end deftypefn - -@deftypevr {Target Hook} {unsigned int} TARGET_FLAGS_REGNUM -If the target has a dedicated flags register, and it needs to use the -post-reload comparison elimination pass, or the delay slot filler pass, -then this value should be set appropriately. -@end deftypevr - -@node Costs -@section Describing Relative Costs of Operations -@cindex costs of instructions -@cindex relative costs -@cindex speed of instructions - -These macros let you describe the relative speed of various operations -on the target machine. - -@defmac REGISTER_MOVE_COST (@var{mode}, @var{from}, @var{to}) -A C expression for the cost of moving data of mode @var{mode} from a -register in class @var{from} to one in class @var{to}. The classes are -expressed using the enumeration values such as @code{GENERAL_REGS}. A -value of 2 is the default; other values are interpreted relative to -that. - -It is not required that the cost always equal 2 when @var{from} is the -same as @var{to}; on some machines it is expensive to move between -registers if they are not general registers. - -If reload sees an insn consisting of a single @code{set} between two -hard registers, and if @code{REGISTER_MOVE_COST} applied to their -classes returns a value of 2, reload does not check to ensure that the -constraints of the insn are met. Setting a cost of other than 2 will -allow reload to verify that the constraints are met. You should do this -if the @samp{mov@var{m}} pattern's constraints do not allow such copying. - -These macros are obsolete, new ports should use the target hook -@code{TARGET_REGISTER_MOVE_COST} instead. -@end defmac - -@deftypefn {Target Hook} int TARGET_REGISTER_MOVE_COST (machine_mode @var{mode}, reg_class_t @var{from}, reg_class_t @var{to}) -This target hook should return the cost of moving data of mode @var{mode} -from a register in class @var{from} to one in class @var{to}. The classes -are expressed using the enumeration values such as @code{GENERAL_REGS}. -A value of 2 is the default; other values are interpreted relative to -that. - -It is not required that the cost always equal 2 when @var{from} is the -same as @var{to}; on some machines it is expensive to move between -registers if they are not general registers. - -If reload sees an insn consisting of a single @code{set} between two -hard registers, and if @code{TARGET_REGISTER_MOVE_COST} applied to their -classes returns a value of 2, reload does not check to ensure that the -constraints of the insn are met. Setting a cost of other than 2 will -allow reload to verify that the constraints are met. You should do this -if the @samp{mov@var{m}} pattern's constraints do not allow such copying. - -The default version of this function returns 2. -@end deftypefn - -@defmac MEMORY_MOVE_COST (@var{mode}, @var{class}, @var{in}) -A C expression for the cost of moving data of mode @var{mode} between a -register of class @var{class} and memory; @var{in} is zero if the value -is to be written to memory, nonzero if it is to be read in. This cost -is relative to those in @code{REGISTER_MOVE_COST}. If moving between -registers and memory is more expensive than between two registers, you -should define this macro to express the relative cost. - -If you do not define this macro, GCC uses a default cost of 4 plus -the cost of copying via a secondary reload register, if one is -needed. If your machine requires a secondary reload register to copy -between memory and a register of @var{class} but the reload mechanism is -more complex than copying via an intermediate, define this macro to -reflect the actual cost of the move. - -GCC defines the function @code{memory_move_secondary_cost} if -secondary reloads are needed. It computes the costs due to copying via -a secondary register. If your machine copies from memory using a -secondary register in the conventional way but the default base value of -4 is not correct for your machine, define this macro to add some other -value to the result of that function. The arguments to that function -are the same as to this macro. - -These macros are obsolete, new ports should use the target hook -@code{TARGET_MEMORY_MOVE_COST} instead. -@end defmac - -@deftypefn {Target Hook} int TARGET_MEMORY_MOVE_COST (machine_mode @var{mode}, reg_class_t @var{rclass}, bool @var{in}) -This target hook should return the cost of moving data of mode @var{mode} -between a register of class @var{rclass} and memory; @var{in} is @code{false} -if the value is to be written to memory, @code{true} if it is to be read in. -This cost is relative to those in @code{TARGET_REGISTER_MOVE_COST}. -If moving between registers and memory is more expensive than between two -registers, you should add this target hook to express the relative cost. - -If you do not add this target hook, GCC uses a default cost of 4 plus -the cost of copying via a secondary reload register, if one is -needed. If your machine requires a secondary reload register to copy -between memory and a register of @var{rclass} but the reload mechanism is -more complex than copying via an intermediate, use this target hook to -reflect the actual cost of the move. - -GCC defines the function @code{memory_move_secondary_cost} if -secondary reloads are needed. It computes the costs due to copying via -a secondary register. If your machine copies from memory using a -secondary register in the conventional way but the default base value of -4 is not correct for your machine, use this target hook to add some other -value to the result of that function. The arguments to that function -are the same as to this target hook. -@end deftypefn - -@defmac BRANCH_COST (@var{speed_p}, @var{predictable_p}) -A C expression for the cost of a branch instruction. A value of 1 is -the default; other values are interpreted relative to that. Parameter -@var{speed_p} is true when the branch in question should be optimized -for speed. When it is false, @code{BRANCH_COST} should return a value -optimal for code size rather than performance. @var{predictable_p} is -true for well-predicted branches. On many architectures the -@code{BRANCH_COST} can be reduced then. -@end defmac - -Here are additional macros which do not specify precise relative costs, -but only that certain actions are more expensive than GCC would -ordinarily expect. - -@defmac SLOW_BYTE_ACCESS -Define this macro as a C expression which is nonzero if accessing less -than a word of memory (i.e.@: a @code{char} or a @code{short}) is no -faster than accessing a word of memory, i.e., if such access -require more than one instruction or if there is no difference in cost -between byte and (aligned) word loads. - -When this macro is not defined, the compiler will access a field by -finding the smallest containing object; when it is defined, a fullword -load will be used if alignment permits. Unless bytes accesses are -faster than word accesses, using word accesses is preferable since it -may eliminate subsequent memory access if subsequent accesses occur to -other fields in the same word of the structure, but to different bytes. -@end defmac - -@deftypefn {Target Hook} bool TARGET_SLOW_UNALIGNED_ACCESS (machine_mode @var{mode}, unsigned int @var{align}) -This hook returns true if memory accesses described by the -@var{mode} and @var{alignment} parameters have a cost many times greater -than aligned accesses, for example if they are emulated in a trap handler. -This hook is invoked only for unaligned accesses, i.e.@: when -@code{@var{alignment} < GET_MODE_ALIGNMENT (@var{mode})}. - -When this hook returns true, the compiler will act as if -@code{STRICT_ALIGNMENT} were true when generating code for block -moves. This can cause significantly more instructions to be produced. -Therefore, do not make this hook return true if unaligned accesses only -add a cycle or two to the time for a memory access. - -The hook must return true whenever @code{STRICT_ALIGNMENT} is true. -The default implementation returns @code{STRICT_ALIGNMENT}. -@end deftypefn - -@defmac MOVE_RATIO (@var{speed}) -The threshold of number of scalar memory-to-memory move insns, @emph{below} -which a sequence of insns should be generated instead of a -string move insn or a library call. Increasing the value will always -make code faster, but eventually incurs high cost in increased code size. - -Note that on machines where the corresponding move insn is a -@code{define_expand} that emits a sequence of insns, this macro counts -the number of such sequences. - -The parameter @var{speed} is true if the code is currently being -optimized for speed rather than size. - -If you don't define this, a reasonable default is used. -@end defmac - -@deftypefn {Target Hook} bool TARGET_USE_BY_PIECES_INFRASTRUCTURE_P (unsigned HOST_WIDE_INT @var{size}, unsigned int @var{alignment}, enum by_pieces_operation @var{op}, bool @var{speed_p}) -GCC will attempt several strategies when asked to copy between -two areas of memory, or to set, clear or store to memory, for example -when copying a @code{struct}. The @code{by_pieces} infrastructure -implements such memory operations as a sequence of load, store or move -insns. Alternate strategies are to expand the -@code{cpymem} or @code{setmem} optabs, to emit a library call, or to emit -unit-by-unit, loop-based operations. - -This target hook should return true if, for a memory operation with a -given @var{size} and @var{alignment}, using the @code{by_pieces} -infrastructure is expected to result in better code generation. -Both @var{size} and @var{alignment} are measured in terms of storage -units. - -The parameter @var{op} is one of: @code{CLEAR_BY_PIECES}, -@code{MOVE_BY_PIECES}, @code{SET_BY_PIECES}, @code{STORE_BY_PIECES} or -@code{COMPARE_BY_PIECES}. These describe the type of memory operation -under consideration. - -The parameter @var{speed_p} is true if the code is currently being -optimized for speed rather than size. - -Returning true for higher values of @var{size} can improve code generation -for speed if the target does not provide an implementation of the -@code{cpymem} or @code{setmem} standard names, if the @code{cpymem} or -@code{setmem} implementation would be more expensive than a sequence of -insns, or if the overhead of a library call would dominate that of -the body of the memory operation. - -Returning true for higher values of @code{size} may also cause an increase -in code size, for example where the number of insns emitted to perform a -move would be greater than that of a library call. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_OVERLAP_OP_BY_PIECES_P (void) -This target hook should return true if when the @code{by_pieces} -infrastructure is used, an offset adjusted unaligned memory operation -in the smallest integer mode for the last piece operation of a memory -region can be generated to avoid doing more than one smaller operations. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_COMPARE_BY_PIECES_BRANCH_RATIO (machine_mode @var{mode}) -When expanding a block comparison in MODE, gcc can try to reduce the -number of branches at the expense of more memory operations. This hook -allows the target to override the default choice. It should return the -factor by which branches should be reduced over the plain expansion with -one comparison per @var{mode}-sized piece. A port can also prevent a -particular mode from being used for block comparisons by returning a -negative number from this hook. -@end deftypefn - -@defmac MOVE_MAX_PIECES -A C expression used by @code{move_by_pieces} to determine the largest unit -a load or store used to copy memory is. Defaults to @code{MOVE_MAX}. -@end defmac - -@defmac STORE_MAX_PIECES -A C expression used by @code{store_by_pieces} to determine the largest unit -a store used to memory is. Defaults to @code{MOVE_MAX_PIECES}, or two times -the size of @code{HOST_WIDE_INT}, whichever is smaller. -@end defmac - -@defmac COMPARE_MAX_PIECES -A C expression used by @code{compare_by_pieces} to determine the largest unit -a load or store used to compare memory is. Defaults to -@code{MOVE_MAX_PIECES}. -@end defmac - -@defmac CLEAR_RATIO (@var{speed}) -The threshold of number of scalar move insns, @emph{below} which a sequence -of insns should be generated to clear memory instead of a string clear insn -or a library call. Increasing the value will always make code faster, but -eventually incurs high cost in increased code size. - -The parameter @var{speed} is true if the code is currently being -optimized for speed rather than size. - -If you don't define this, a reasonable default is used. -@end defmac - -@defmac SET_RATIO (@var{speed}) -The threshold of number of scalar move insns, @emph{below} which a sequence -of insns should be generated to set memory to a constant value, instead of -a block set insn or a library call. -Increasing the value will always make code faster, but -eventually incurs high cost in increased code size. - -The parameter @var{speed} is true if the code is currently being -optimized for speed rather than size. - -If you don't define this, it defaults to the value of @code{MOVE_RATIO}. -@end defmac - -@defmac USE_LOAD_POST_INCREMENT (@var{mode}) -A C expression used to determine whether a load postincrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_POST_INCREMENT}. -@end defmac - -@defmac USE_LOAD_POST_DECREMENT (@var{mode}) -A C expression used to determine whether a load postdecrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_POST_DECREMENT}. -@end defmac - -@defmac USE_LOAD_PRE_INCREMENT (@var{mode}) -A C expression used to determine whether a load preincrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_PRE_INCREMENT}. -@end defmac - -@defmac USE_LOAD_PRE_DECREMENT (@var{mode}) -A C expression used to determine whether a load predecrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_PRE_DECREMENT}. -@end defmac - -@defmac USE_STORE_POST_INCREMENT (@var{mode}) -A C expression used to determine whether a store postincrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_POST_INCREMENT}. -@end defmac - -@defmac USE_STORE_POST_DECREMENT (@var{mode}) -A C expression used to determine whether a store postdecrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_POST_DECREMENT}. -@end defmac - -@defmac USE_STORE_PRE_INCREMENT (@var{mode}) -This macro is used to determine whether a store preincrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_PRE_INCREMENT}. -@end defmac - -@defmac USE_STORE_PRE_DECREMENT (@var{mode}) -This macro is used to determine whether a store predecrement is a good -thing to use for a given mode. Defaults to the value of -@code{HAVE_PRE_DECREMENT}. -@end defmac - -@defmac NO_FUNCTION_CSE -Define this macro to be true if it is as good or better to call a constant -function address than to call an address kept in a register. -@end defmac - -@defmac LOGICAL_OP_NON_SHORT_CIRCUIT -Define this macro if a non-short-circuit operation produced by -@samp{fold_range_test ()} is optimal. This macro defaults to true if -@code{BRANCH_COST} is greater than or equal to the value 2. -@end defmac - -@deftypefn {Target Hook} bool TARGET_OPTAB_SUPPORTED_P (int @var{op}, machine_mode @var{mode1}, machine_mode @var{mode2}, optimization_type @var{opt_type}) -Return true if the optimizers should use optab @var{op} with -modes @var{mode1} and @var{mode2} for optimization type @var{opt_type}. -The optab is known to have an associated @file{.md} instruction -whose C condition is true. @var{mode2} is only meaningful for conversion -optabs; for direct optabs it is a copy of @var{mode1}. - -For example, when called with @var{op} equal to @code{rint_optab} and -@var{mode1} equal to @code{DFmode}, the hook should say whether the -optimizers should use optab @code{rintdf2}. - -The default hook returns true for all inputs. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_RTX_COSTS (rtx @var{x}, machine_mode @var{mode}, int @var{outer_code}, int @var{opno}, int *@var{total}, bool @var{speed}) -This target hook describes the relative costs of RTL expressions. - -The cost may depend on the precise form of the expression, which is -available for examination in @var{x}, and the fact that @var{x} appears -as operand @var{opno} of an expression with rtx code @var{outer_code}. -That is, the hook can assume that there is some rtx @var{y} such -that @samp{GET_CODE (@var{y}) == @var{outer_code}} and such that -either (a) @samp{XEXP (@var{y}, @var{opno}) == @var{x}} or -(b) @samp{XVEC (@var{y}, @var{opno})} contains @var{x}. - -@var{mode} is @var{x}'s machine mode, or for cases like @code{const_int} that -do not have a mode, the mode in which @var{x} is used. - -In implementing this hook, you can use the construct -@code{COSTS_N_INSNS (@var{n})} to specify a cost equal to @var{n} fast -instructions. - -On entry to the hook, @code{*@var{total}} contains a default estimate -for the cost of the expression. The hook should modify this value as -necessary. Traditionally, the default costs are @code{COSTS_N_INSNS (5)} -for multiplications, @code{COSTS_N_INSNS (7)} for division and modulus -operations, and @code{COSTS_N_INSNS (1)} for all other operations. - -When optimizing for code size, i.e.@: when @code{speed} is -false, this target hook should be used to estimate the relative -size cost of an expression, again relative to @code{COSTS_N_INSNS}. - -The hook returns true when all subexpressions of @var{x} have been -processed, and false when @code{rtx_cost} should recurse. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_ADDRESS_COST (rtx @var{address}, machine_mode @var{mode}, addr_space_t @var{as}, bool @var{speed}) -This hook computes the cost of an addressing mode that contains -@var{address}. If not defined, the cost is computed from -the @var{address} expression and the @code{TARGET_RTX_COST} hook. - -For most CISC machines, the default cost is a good approximation of the -true cost of the addressing mode. However, on RISC machines, all -instructions normally have the same length and execution time. Hence -all addresses will have equal costs. - -In cases where more than one form of an address is known, the form with -the lowest cost will be used. If multiple forms have the same, lowest, -cost, the one that is the most complex will be used. - -For example, suppose an address that is equal to the sum of a register -and a constant is used twice in the same basic block. When this macro -is not defined, the address will be computed in a register and memory -references will be indirect through that register. On machines where -the cost of the addressing mode containing the sum is no higher than -that of a simple indirect reference, this will produce an additional -instruction and possibly require an additional register. Proper -specification of this macro eliminates this overhead for such machines. - -This hook is never called with an invalid address. - -On machines where an address involving more than one register is as -cheap as an address computation involving only one register, defining -@code{TARGET_ADDRESS_COST} to reflect this can cause two registers to -be live over a region of code where only one would have been if -@code{TARGET_ADDRESS_COST} were not defined in that manner. This effect -should be considered in the definition of this macro. Equivalent costs -should probably only be given to addresses with different numbers of -registers on machines with lots of registers. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_INSN_COST (rtx_insn *@var{insn}, bool @var{speed}) -This target hook describes the relative costs of RTL instructions. - -In implementing this hook, you can use the construct -@code{COSTS_N_INSNS (@var{n})} to specify a cost equal to @var{n} fast -instructions. - -When optimizing for code size, i.e.@: when @code{speed} is -false, this target hook should be used to estimate the relative -size cost of an expression, again relative to @code{COSTS_N_INSNS}. -@end deftypefn - -@deftypefn {Target Hook} {unsigned int} TARGET_MAX_NOCE_IFCVT_SEQ_COST (edge @var{e}) -This hook returns a value in the same units as @code{TARGET_RTX_COSTS}, -giving the maximum acceptable cost for a sequence generated by the RTL -if-conversion pass when conditional execution is not available. -The RTL if-conversion pass attempts to convert conditional operations -that would require a branch to a series of unconditional operations and -@code{mov@var{mode}cc} insns. This hook returns the maximum cost of the -unconditional instructions and the @code{mov@var{mode}cc} insns. -RTL if-conversion is cancelled if the cost of the converted sequence -is greater than the value returned by this hook. - -@code{e} is the edge between the basic block containing the conditional -branch to the basic block which would be executed if the condition -were true. - -The default implementation of this hook uses the -@code{max-rtl-if-conversion-[un]predictable} parameters if they are set, -and uses a multiple of @code{BRANCH_COST} otherwise. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_NOCE_CONVERSION_PROFITABLE_P (rtx_insn *@var{seq}, struct noce_if_info *@var{if_info}) -This hook returns true if the instruction sequence @code{seq} is a good -candidate as a replacement for the if-convertible sequence described in -@code{if_info}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_NEW_ADDRESS_PROFITABLE_P (rtx @var{memref}, rtx_insn * @var{insn}, rtx @var{new_addr}) -Return @code{true} if it is profitable to replace the address in -@var{memref} with @var{new_addr}. This allows targets to prevent the -scheduler from undoing address optimizations. The instruction containing the -memref is @var{insn}. The default implementation returns @code{true}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_NO_SPECULATION_IN_DELAY_SLOTS_P (void) -This predicate controls the use of the eager delay slot filler to disallow -speculatively executed instructions being placed in delay slots. Targets -such as certain MIPS architectures possess both branches with and without -delay slots. As the eager delay slot filler can decrease performance, -disabling it is beneficial when ordinary branches are available. Use of -delay slot branches filled using the basic filler is often still desirable -as the delay slot can hide a pipeline bubble. -@end deftypefn - -@deftypefn {Target Hook} HOST_WIDE_INT TARGET_ESTIMATED_POLY_VALUE (poly_int64 @var{val}, poly_value_estimate_kind @var{kind}) -Return an estimate of the runtime value of @var{val}, for use in -things like cost calculations or profiling frequencies. @var{kind} is used -to ask for the minimum, maximum, and likely estimates of the value through -the @code{POLY_VALUE_MIN}, @code{POLY_VALUE_MAX} and -@code{POLY_VALUE_LIKELY} values. The default -implementation returns the lowest possible value of @var{val}. -@end deftypefn - -@node Scheduling -@section Adjusting the Instruction Scheduler - -The instruction scheduler may need a fair amount of machine-specific -adjustment in order to produce good code. GCC provides several target -hooks for this purpose. It is usually enough to define just a few of -them: try the first ones in this list first. - -@deftypefn {Target Hook} int TARGET_SCHED_ISSUE_RATE (void) -This hook returns the maximum number of instructions that can ever -issue at the same time on the target machine. The default is one. -Although the insn scheduler can define itself the possibility of issue -an insn on the same cycle, the value can serve as an additional -constraint to issue insns on the same simulated processor cycle (see -hooks @samp{TARGET_SCHED_REORDER} and @samp{TARGET_SCHED_REORDER2}). -This value must be constant over the entire compilation. If you need -it to vary depending on what the instructions are, you must use -@samp{TARGET_SCHED_VARIABLE_ISSUE}. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SCHED_VARIABLE_ISSUE (FILE *@var{file}, int @var{verbose}, rtx_insn *@var{insn}, int @var{more}) -This hook is executed by the scheduler after it has scheduled an insn -from the ready list. It should return the number of insns which can -still be issued in the current cycle. The default is -@samp{@w{@var{more} - 1}} for insns other than @code{CLOBBER} and -@code{USE}, which normally are not counted against the issue rate. -You should define this hook if some insns take more machine resources -than others, so that fewer insns can follow them in the same cycle. -@var{file} is either a null pointer, or a stdio stream to write any -debug output to. @var{verbose} is the verbose level provided by -@option{-fsched-verbose-@var{n}}. @var{insn} is the instruction that -was scheduled. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SCHED_ADJUST_COST (rtx_insn *@var{insn}, int @var{dep_type1}, rtx_insn *@var{dep_insn}, int @var{cost}, unsigned int @var{dw}) -This function corrects the value of @var{cost} based on the -relationship between @var{insn} and @var{dep_insn} through a -dependence of type dep_type, and strength @var{dw}. It should return the new -value. The default is to make no adjustment to @var{cost}. This can be -used for example to specify to the scheduler using the traditional pipeline -description that an output- or anti-dependence does not incur the same cost -as a data-dependence. If the scheduler using the automaton based pipeline -description, the cost of anti-dependence is zero and the cost of -output-dependence is maximum of one and the difference of latency -times of the first and the second insns. If these values are not -acceptable, you could use the hook to modify them too. See also -@pxref{Processor pipeline description}. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SCHED_ADJUST_PRIORITY (rtx_insn *@var{insn}, int @var{priority}) -This hook adjusts the integer scheduling priority @var{priority} of -@var{insn}. It should return the new priority. Increase the priority to -execute @var{insn} earlier, reduce the priority to execute @var{insn} -later. Do not define this hook if you do not need to adjust the -scheduling priorities of insns. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SCHED_REORDER (FILE *@var{file}, int @var{verbose}, rtx_insn **@var{ready}, int *@var{n_readyp}, int @var{clock}) -This hook is executed by the scheduler after it has scheduled the ready -list, to allow the machine description to reorder it (for example to -combine two small instructions together on @samp{VLIW} machines). -@var{file} is either a null pointer, or a stdio stream to write any -debug output to. @var{verbose} is the verbose level provided by -@option{-fsched-verbose-@var{n}}. @var{ready} is a pointer to the ready -list of instructions that are ready to be scheduled. @var{n_readyp} is -a pointer to the number of elements in the ready list. The scheduler -reads the ready list in reverse order, starting with -@var{ready}[@var{*n_readyp} @minus{} 1] and going to @var{ready}[0]. @var{clock} -is the timer tick of the scheduler. You may modify the ready list and -the number of ready insns. The return value is the number of insns that -can issue this cycle; normally this is just @code{issue_rate}. See also -@samp{TARGET_SCHED_REORDER2}. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SCHED_REORDER2 (FILE *@var{file}, int @var{verbose}, rtx_insn **@var{ready}, int *@var{n_readyp}, int @var{clock}) -Like @samp{TARGET_SCHED_REORDER}, but called at a different time. That -function is called whenever the scheduler starts a new cycle. This one -is called once per iteration over a cycle, immediately after -@samp{TARGET_SCHED_VARIABLE_ISSUE}; it can reorder the ready list and -return the number of insns to be scheduled in the same cycle. Defining -this hook can be useful if there are frequent situations where -scheduling one insn causes other insns to become ready in the same -cycle. These other insns can then be taken into account properly. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_SCHED_MACRO_FUSION_P (void) -This hook is used to check whether target platform supports macro fusion. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_SCHED_MACRO_FUSION_PAIR_P (rtx_insn *@var{prev}, rtx_insn *@var{curr}) -This hook is used to check whether two insns should be macro fused for -a target microarchitecture. If this hook returns true for the given insn pair -(@var{prev} and @var{curr}), the scheduler will put them into a sched -group, and they will not be scheduled apart. The two insns will be either -two SET insns or a compare and a conditional jump and this hook should -validate any dependencies needed to fuse the two insns together. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_DEPENDENCIES_EVALUATION_HOOK (rtx_insn *@var{head}, rtx_insn *@var{tail}) -This hook is called after evaluation forward dependencies of insns in -chain given by two parameter values (@var{head} and @var{tail} -correspondingly) but before insns scheduling of the insn chain. For -example, it can be used for better insn classification if it requires -analysis of dependencies. This hook can use backward and forward -dependencies of the insn scheduler because they are already -calculated. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_INIT (FILE *@var{file}, int @var{verbose}, int @var{max_ready}) -This hook is executed by the scheduler at the beginning of each block of -instructions that are to be scheduled. @var{file} is either a null -pointer, or a stdio stream to write any debug output to. @var{verbose} -is the verbose level provided by @option{-fsched-verbose-@var{n}}. -@var{max_ready} is the maximum number of insns in the current scheduling -region that can be live at the same time. This can be used to allocate -scratch space if it is needed, e.g.@: by @samp{TARGET_SCHED_REORDER}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_FINISH (FILE *@var{file}, int @var{verbose}) -This hook is executed by the scheduler at the end of each block of -instructions that are to be scheduled. It can be used to perform -cleanup of any actions done by the other scheduling hooks. @var{file} -is either a null pointer, or a stdio stream to write any debug output -to. @var{verbose} is the verbose level provided by -@option{-fsched-verbose-@var{n}}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_INIT_GLOBAL (FILE *@var{file}, int @var{verbose}, int @var{old_max_uid}) -This hook is executed by the scheduler after function level initializations. -@var{file} is either a null pointer, or a stdio stream to write any debug output to. -@var{verbose} is the verbose level provided by @option{-fsched-verbose-@var{n}}. -@var{old_max_uid} is the maximum insn uid when scheduling begins. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_FINISH_GLOBAL (FILE *@var{file}, int @var{verbose}) -This is the cleanup hook corresponding to @code{TARGET_SCHED_INIT_GLOBAL}. -@var{file} is either a null pointer, or a stdio stream to write any debug output to. -@var{verbose} is the verbose level provided by @option{-fsched-verbose-@var{n}}. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_SCHED_DFA_PRE_CYCLE_INSN (void) -The hook returns an RTL insn. The automaton state used in the -pipeline hazard recognizer is changed as if the insn were scheduled -when the new simulated processor cycle starts. Usage of the hook may -simplify the automaton pipeline description for some @acronym{VLIW} -processors. If the hook is defined, it is used only for the automaton -based pipeline description. The default is not to change the state -when the new simulated processor cycle starts. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_INIT_DFA_PRE_CYCLE_INSN (void) -The hook can be used to initialize data used by the previous hook. -@end deftypefn - -@deftypefn {Target Hook} {rtx_insn *} TARGET_SCHED_DFA_POST_CYCLE_INSN (void) -The hook is analogous to @samp{TARGET_SCHED_DFA_PRE_CYCLE_INSN} but used -to changed the state as if the insn were scheduled when the new -simulated processor cycle finishes. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_INIT_DFA_POST_CYCLE_INSN (void) -The hook is analogous to @samp{TARGET_SCHED_INIT_DFA_PRE_CYCLE_INSN} but -used to initialize data used by the previous hook. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_DFA_PRE_ADVANCE_CYCLE (void) -The hook to notify target that the current simulated cycle is about to finish. -The hook is analogous to @samp{TARGET_SCHED_DFA_PRE_CYCLE_INSN} but used -to change the state in more complicated situations - e.g., when advancing -state on a single insn is not enough. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_DFA_POST_ADVANCE_CYCLE (void) -The hook to notify target that new simulated cycle has just started. -The hook is analogous to @samp{TARGET_SCHED_DFA_POST_CYCLE_INSN} but used -to change the state in more complicated situations - e.g., when advancing -state on a single insn is not enough. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD (void) -This hook controls better choosing an insn from the ready insn queue -for the @acronym{DFA}-based insn scheduler. Usually the scheduler -chooses the first insn from the queue. If the hook returns a positive -value, an additional scheduler code tries all permutations of -@samp{TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD ()} -subsequent ready insns to choose an insn whose issue will result in -maximal number of issued insns on the same cycle. For the -@acronym{VLIW} processor, the code could actually solve the problem of -packing simple insns into the @acronym{VLIW} insn. Of course, if the -rules of @acronym{VLIW} packing are described in the automaton. - -This code also could be used for superscalar @acronym{RISC} -processors. Let us consider a superscalar @acronym{RISC} processor -with 3 pipelines. Some insns can be executed in pipelines @var{A} or -@var{B}, some insns can be executed only in pipelines @var{B} or -@var{C}, and one insn can be executed in pipeline @var{B}. The -processor may issue the 1st insn into @var{A} and the 2nd one into -@var{B}. In this case, the 3rd insn will wait for freeing @var{B} -until the next cycle. If the scheduler issues the 3rd insn the first, -the processor could issue all 3 insns per cycle. - -Actually this code demonstrates advantages of the automaton based -pipeline hazard recognizer. We try quickly and easy many insn -schedules to choose the best one. - -The default is no multipass scheduling. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD_GUARD (rtx_insn *@var{insn}, int @var{ready_index}) - -This hook controls what insns from the ready insn queue will be -considered for the multipass insn scheduling. If the hook returns -zero for @var{insn}, the insn will be considered in multipass scheduling. -Positive return values will remove @var{insn} from consideration on -the current round of multipass scheduling. -Negative return values will remove @var{insn} from consideration for given -number of cycles. -Backends should be careful about returning non-zero for highest priority -instruction at position 0 in the ready list. @var{ready_index} is passed -to allow backends make correct judgements. - -The default is that any ready insns can be chosen to be issued. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_BEGIN (void *@var{data}, signed char *@var{ready_try}, int @var{n_ready}, bool @var{first_cycle_insn_p}) -This hook prepares the target backend for a new round of multipass -scheduling. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_ISSUE (void *@var{data}, signed char *@var{ready_try}, int @var{n_ready}, rtx_insn *@var{insn}, const void *@var{prev_data}) -This hook is called when multipass scheduling evaluates instruction INSN. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_BACKTRACK (const void *@var{data}, signed char *@var{ready_try}, int @var{n_ready}) -This is called when multipass scheduling backtracks from evaluation of -an instruction. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_END (const void *@var{data}) -This hook notifies the target about the result of the concluded current -round of multipass scheduling. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_INIT (void *@var{data}) -This hook initializes target-specific data used in multipass scheduling. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_FINI (void *@var{data}) -This hook finalizes target-specific data used in multipass scheduling. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SCHED_DFA_NEW_CYCLE (FILE *@var{dump}, int @var{verbose}, rtx_insn *@var{insn}, int @var{last_clock}, int @var{clock}, int *@var{sort_p}) -This hook is called by the insn scheduler before issuing @var{insn} -on cycle @var{clock}. If the hook returns nonzero, -@var{insn} is not issued on this processor cycle. Instead, -the processor cycle is advanced. If *@var{sort_p} -is zero, the insn ready queue is not sorted on the new cycle -start as usually. @var{dump} and @var{verbose} specify the file and -verbosity level to use for debugging output. -@var{last_clock} and @var{clock} are, respectively, the -processor cycle on which the previous insn has been issued, -and the current processor cycle. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_SCHED_IS_COSTLY_DEPENDENCE (struct _dep *@var{_dep}, int @var{cost}, int @var{distance}) -This hook is used to define which dependences are considered costly by -the target, so costly that it is not advisable to schedule the insns that -are involved in the dependence too close to one another. The parameters -to this hook are as follows: The first parameter @var{_dep} is the dependence -being evaluated. The second parameter @var{cost} is the cost of the -dependence as estimated by the scheduler, and the third -parameter @var{distance} is the distance in cycles between the two insns. -The hook returns @code{true} if considering the distance between the two -insns the dependence between them is considered costly by the target, -and @code{false} otherwise. - -Defining this hook can be useful in multiple-issue out-of-order machines, -where (a) it's practically hopeless to predict the actual data/resource -delays, however: (b) there's a better chance to predict the actual grouping -that will be formed, and (c) correctly emulating the grouping can be very -important. In such targets one may want to allow issuing dependent insns -closer to one another---i.e., closer than the dependence distance; however, -not in cases of ``costly dependences'', which this hooks allows to define. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_H_I_D_EXTENDED (void) -This hook is called by the insn scheduler after emitting a new instruction to -the instruction stream. The hook notifies a target backend to extend its -per instruction data structures. -@end deftypefn - -@deftypefn {Target Hook} {void *} TARGET_SCHED_ALLOC_SCHED_CONTEXT (void) -Return a pointer to a store large enough to hold target scheduling context. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_INIT_SCHED_CONTEXT (void *@var{tc}, bool @var{clean_p}) -Initialize store pointed to by @var{tc} to hold target scheduling context. -It @var{clean_p} is true then initialize @var{tc} as if scheduler is at the -beginning of the block. Otherwise, copy the current context into @var{tc}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_SET_SCHED_CONTEXT (void *@var{tc}) -Copy target scheduling context pointed to by @var{tc} to the current context. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_CLEAR_SCHED_CONTEXT (void *@var{tc}) -Deallocate internal data in target scheduling context pointed to by @var{tc}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_FREE_SCHED_CONTEXT (void *@var{tc}) -Deallocate a store for target scheduling context pointed to by @var{tc}. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SCHED_SPECULATE_INSN (rtx_insn *@var{insn}, unsigned int @var{dep_status}, rtx *@var{new_pat}) -This hook is called by the insn scheduler when @var{insn} has only -speculative dependencies and therefore can be scheduled speculatively. -The hook is used to check if the pattern of @var{insn} has a speculative -version and, in case of successful check, to generate that speculative -pattern. The hook should return 1, if the instruction has a speculative form, -or @minus{}1, if it doesn't. @var{request} describes the type of requested -speculation. If the return value equals 1 then @var{new_pat} is assigned -the generated speculative pattern. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_SCHED_NEEDS_BLOCK_P (unsigned int @var{dep_status}) -This hook is called by the insn scheduler during generation of recovery code -for @var{insn}. It should return @code{true}, if the corresponding check -instruction should branch to recovery code, or @code{false} otherwise. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_SCHED_GEN_SPEC_CHECK (rtx_insn *@var{insn}, rtx_insn *@var{label}, unsigned int @var{ds}) -This hook is called by the insn scheduler to generate a pattern for recovery -check instruction. If @var{mutate_p} is zero, then @var{insn} is a -speculative instruction for which the check should be generated. -@var{label} is either a label of a basic block, where recovery code should -be emitted, or a null pointer, when requested check doesn't branch to -recovery code (a simple check). If @var{mutate_p} is nonzero, then -a pattern for a branchy check corresponding to a simple check denoted by -@var{insn} should be generated. In this case @var{label} can't be null. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_SET_SCHED_FLAGS (struct spec_info_def *@var{spec_info}) -This hook is used by the insn scheduler to find out what features should be -enabled/used. -The structure *@var{spec_info} should be filled in by the target. -The structure describes speculation types that can be used in the scheduler. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_SCHED_CAN_SPECULATE_INSN (rtx_insn *@var{insn}) -Some instructions should never be speculated by the schedulers, usually - because the instruction is too expensive to get this wrong. Often such - instructions have long latency, and often they are not fully modeled in the - pipeline descriptions. This hook should return @code{false} if @var{insn} - should not be speculated. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_SCHED_SMS_RES_MII (struct ddg *@var{g}) -This hook is called by the swing modulo scheduler to calculate a -resource-based lower bound which is based on the resources available in -the machine and the resources required by each instruction. The target -backend can use @var{g} to calculate such bound. A very simple lower -bound will be used in case this hook is not implemented: the total number -of instructions divided by the issue rate. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_SCHED_DISPATCH (rtx_insn *@var{insn}, int @var{x}) -This hook is called by Haifa Scheduler. It returns true if dispatch scheduling -is supported in hardware and the condition specified in the parameter is true. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_DISPATCH_DO (rtx_insn *@var{insn}, int @var{x}) -This hook is called by Haifa Scheduler. It performs the operation specified -in its second parameter. -@end deftypefn - -@deftypevr {Target Hook} bool TARGET_SCHED_EXPOSED_PIPELINE -True if the processor has an exposed pipeline, which means that not just -the order of instructions is important for correctness when scheduling, but -also the latencies of operations. -@end deftypevr - -@deftypefn {Target Hook} int TARGET_SCHED_REASSOCIATION_WIDTH (unsigned int @var{opc}, machine_mode @var{mode}) -This hook is called by tree reassociator to determine a level of -parallelism required in output calculations chain. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SCHED_FUSION_PRIORITY (rtx_insn *@var{insn}, int @var{max_pri}, int *@var{fusion_pri}, int *@var{pri}) -This hook is called by scheduling fusion pass. It calculates fusion -priorities for each instruction passed in by parameter. The priorities -are returned via pointer parameters. - -@var{insn} is the instruction whose priorities need to be calculated. -@var{max_pri} is the maximum priority can be returned in any cases. -@var{fusion_pri} is the pointer parameter through which @var{insn}'s -fusion priority should be calculated and returned. -@var{pri} is the pointer parameter through which @var{insn}'s priority -should be calculated and returned. - -Same @var{fusion_pri} should be returned for instructions which should -be scheduled together. Different @var{pri} should be returned for -instructions with same @var{fusion_pri}. @var{fusion_pri} is the major -sort key, @var{pri} is the minor sort key. All instructions will be -scheduled according to the two priorities. All priorities calculated -should be between 0 (exclusive) and @var{max_pri} (inclusive). To avoid -false dependencies, @var{fusion_pri} of instructions which need to be -scheduled together should be smaller than @var{fusion_pri} of irrelevant -instructions. - -Given below example: - -@smallexample - ldr r10, [r1, 4] - add r4, r4, r10 - ldr r15, [r2, 8] - sub r5, r5, r15 - ldr r11, [r1, 0] - add r4, r4, r11 - ldr r16, [r2, 12] - sub r5, r5, r16 -@end smallexample - -On targets like ARM/AArch64, the two pairs of consecutive loads should be -merged. Since peephole2 pass can't help in this case unless consecutive -loads are actually next to each other in instruction flow. That's where -this scheduling fusion pass works. This hook calculates priority for each -instruction based on its fustion type, like: - -@smallexample - ldr r10, [r1, 4] ; fusion_pri=99, pri=96 - add r4, r4, r10 ; fusion_pri=100, pri=100 - ldr r15, [r2, 8] ; fusion_pri=98, pri=92 - sub r5, r5, r15 ; fusion_pri=100, pri=100 - ldr r11, [r1, 0] ; fusion_pri=99, pri=100 - add r4, r4, r11 ; fusion_pri=100, pri=100 - ldr r16, [r2, 12] ; fusion_pri=98, pri=88 - sub r5, r5, r16 ; fusion_pri=100, pri=100 -@end smallexample - -Scheduling fusion pass then sorts all ready to issue instructions according -to the priorities. As a result, instructions of same fusion type will be -pushed together in instruction flow, like: - -@smallexample - ldr r11, [r1, 0] - ldr r10, [r1, 4] - ldr r15, [r2, 8] - ldr r16, [r2, 12] - add r4, r4, r10 - sub r5, r5, r15 - add r4, r4, r11 - sub r5, r5, r16 -@end smallexample - -Now peephole2 pass can simply merge the two pairs of loads. - -Since scheduling fusion pass relies on peephole2 to do real fusion -work, it is only enabled by default when peephole2 is in effect. - -This is firstly introduced on ARM/AArch64 targets, please refer to -the hook implementation for how different fusion types are supported. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_EXPAND_DIVMOD_LIBFUNC (rtx @var{libfunc}, machine_mode @var{mode}, rtx @var{op0}, rtx @var{op1}, rtx *@var{quot}, rtx *@var{rem}) -Define this hook for enabling divmod transform if the port does not have -hardware divmod insn but defines target-specific divmod libfuncs. -@end deftypefn - -@node Sections -@section Dividing the Output into Sections (Texts, Data, @dots{}) -@c the above section title is WAY too long. maybe cut the part between -@c the (...)? --mew 10feb93 - -An object file is divided into sections containing different types of -data. In the most common case, there are three sections: the @dfn{text -section}, which holds instructions and read-only data; the @dfn{data -section}, which holds initialized writable data; and the @dfn{bss -section}, which holds uninitialized data. Some systems have other kinds -of sections. - -@file{varasm.cc} provides several well-known sections, such as -@code{text_section}, @code{data_section} and @code{bss_section}. -The normal way of controlling a @code{@var{foo}_section} variable -is to define the associated @code{@var{FOO}_SECTION_ASM_OP} macro, -as described below. The macros are only read once, when @file{varasm.cc} -initializes itself, so their values must be run-time constants. -They may however depend on command-line flags. - -@emph{Note:} Some run-time files, such @file{crtstuff.c}, also make -use of the @code{@var{FOO}_SECTION_ASM_OP} macros, and expect them -to be string literals. - -Some assemblers require a different string to be written every time a -section is selected. If your assembler falls into this category, you -should define the @code{TARGET_ASM_INIT_SECTIONS} hook and use -@code{get_unnamed_section} to set up the sections. - -You must always create a @code{text_section}, either by defining -@code{TEXT_SECTION_ASM_OP} or by initializing @code{text_section} -in @code{TARGET_ASM_INIT_SECTIONS}. The same is true of -@code{data_section} and @code{DATA_SECTION_ASM_OP}. If you do not -create a distinct @code{readonly_data_section}, the default is to -reuse @code{text_section}. - -All the other @file{varasm.cc} sections are optional, and are null -if the target does not provide them. - -@defmac TEXT_SECTION_ASM_OP -A C expression whose value is a string, including spacing, containing the -assembler operation that should precede instructions and read-only data. -Normally @code{"\t.text"} is right. -@end defmac - -@defmac HOT_TEXT_SECTION_NAME -If defined, a C string constant for the name of the section containing most -frequently executed functions of the program. If not defined, GCC will provide -a default definition if the target supports named sections. -@end defmac - -@defmac UNLIKELY_EXECUTED_TEXT_SECTION_NAME -If defined, a C string constant for the name of the section containing unlikely -executed functions in the program. -@end defmac - -@defmac DATA_SECTION_ASM_OP -A C expression whose value is a string, including spacing, containing the -assembler operation to identify the following data as writable initialized -data. Normally @code{"\t.data"} is right. -@end defmac - -@defmac SDATA_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -initialized, writable small data. -@end defmac - -@defmac READONLY_DATA_SECTION_ASM_OP -A C expression whose value is a string, including spacing, containing the -assembler operation to identify the following data as read-only initialized -data. -@end defmac - -@defmac BSS_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -uninitialized global data. If not defined, and -@code{ASM_OUTPUT_ALIGNED_BSS} not defined, -uninitialized global data will be output in the data section if -@option{-fno-common} is passed, otherwise @code{ASM_OUTPUT_COMMON} will be -used. -@end defmac - -@defmac SBSS_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -uninitialized, writable small data. -@end defmac - -@defmac TLS_COMMON_ASM_OP -If defined, a C expression whose value is a string containing the -assembler operation to identify the following data as thread-local -common data. The default is @code{".tls_common"}. -@end defmac - -@defmac TLS_SECTION_ASM_FLAG -If defined, a C expression whose value is a character constant -containing the flag used to mark a section as a TLS section. The -default is @code{'T'}. -@end defmac - -@defmac INIT_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -initialization code. If not defined, GCC will assume such a section does -not exist. This section has no corresponding @code{init_section} -variable; it is used entirely in runtime code. -@end defmac - -@defmac FINI_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -finalization code. If not defined, GCC will assume such a section does -not exist. This section has no corresponding @code{fini_section} -variable; it is used entirely in runtime code. -@end defmac - -@defmac INIT_ARRAY_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -part of the @code{.init_array} (or equivalent) section. If not -defined, GCC will assume such a section does not exist. Do not define -both this macro and @code{INIT_SECTION_ASM_OP}. -@end defmac - -@defmac FINI_ARRAY_SECTION_ASM_OP -If defined, a C expression whose value is a string, including spacing, -containing the assembler operation to identify the following data as -part of the @code{.fini_array} (or equivalent) section. If not -defined, GCC will assume such a section does not exist. Do not define -both this macro and @code{FINI_SECTION_ASM_OP}. -@end defmac - -@defmac MACH_DEP_SECTION_ASM_FLAG -If defined, a C expression whose value is a character constant -containing the flag used to mark a machine-dependent section. This -corresponds to the @code{SECTION_MACH_DEP} section flag. -@end defmac - -@defmac CRT_CALL_STATIC_FUNCTION (@var{section_op}, @var{function}) -If defined, an ASM statement that switches to a different section -via @var{section_op}, calls @var{function}, and switches back to -the text section. This is used in @file{crtstuff.c} if -@code{INIT_SECTION_ASM_OP} or @code{FINI_SECTION_ASM_OP} to calls -to initialization and finalization functions from the init and fini -sections. By default, this macro uses a simple function call. Some -ports need hand-crafted assembly code to avoid dependencies on -registers initialized in the function prologue or to ensure that -constant pools don't end up too far way in the text section. -@end defmac - -@defmac TARGET_LIBGCC_SDATA_SECTION -If defined, a string which names the section into which small -variables defined in crtstuff and libgcc should go. This is useful -when the target has options for optimizing access to small data, and -you want the crtstuff and libgcc routines to be conservative in what -they expect of your application yet liberal in what your application -expects. For example, for targets with a @code{.sdata} section (like -MIPS), you could compile crtstuff with @code{-G 0} so that it doesn't -require small data support from your application, but use this macro -to put small data into @code{.sdata} so that your application can -access these variables whether it uses small data or not. -@end defmac - -@defmac FORCE_CODE_SECTION_ALIGN -If defined, an ASM statement that aligns a code section to some -arbitrary boundary. This is used to force all fragments of the -@code{.init} and @code{.fini} sections to have to same alignment -and thus prevent the linker from having to add any padding. -@end defmac - -@defmac JUMP_TABLES_IN_TEXT_SECTION -Define this macro to be an expression with a nonzero value if jump -tables (for @code{tablejump} insns) should be output in the text -section, along with the assembler instructions. Otherwise, the -readonly data section is used. - -This macro is irrelevant if there is no separate readonly data section. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_INIT_SECTIONS (void) -Define this hook if you need to do something special to set up the -@file{varasm.cc} sections, or if your target has some special sections -of its own that you need to create. - -GCC calls this hook after processing the command line, but before writing -any assembly code, and before calling any of the section-returning hooks -described below. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_ASM_RELOC_RW_MASK (void) -Return a mask describing how relocations should be treated when -selecting sections. Bit 1 should be set if global relocations -should be placed in a read-write section; bit 0 should be set if -local relocations should be placed in a read-write section. - -The default version of this function returns 3 when @option{-fpic} -is in effect, and 0 otherwise. The hook is typically redefined -when the target cannot support (some kinds of) dynamic relocations -in read-only sections even in executables. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ASM_GENERATE_PIC_ADDR_DIFF_VEC (void) -Return true to generate ADDR_DIF_VEC table -or false to generate ADDR_VEC table for jumps in case of -fPIC. - -The default version of this function returns true if flag_pic -equals true and false otherwise -@end deftypefn - -@deftypefn {Target Hook} {section *} TARGET_ASM_SELECT_SECTION (tree @var{exp}, int @var{reloc}, unsigned HOST_WIDE_INT @var{align}) -Return the section into which @var{exp} should be placed. You can -assume that @var{exp} is either a @code{VAR_DECL} node or a constant of -some sort. @var{reloc} indicates whether the initial value of @var{exp} -requires link-time relocations. Bit 0 is set when variable contains -local relocations only, while bit 1 is set for global relocations. -@var{align} is the constant alignment in bits. - -The default version of this function takes care of putting read-only -variables in @code{readonly_data_section}. - -See also @var{USE_SELECT_SECTION_FOR_FUNCTIONS}. -@end deftypefn - -@defmac USE_SELECT_SECTION_FOR_FUNCTIONS -Define this macro if you wish TARGET_ASM_SELECT_SECTION to be called -for @code{FUNCTION_DECL}s as well as for variables and constants. - -In the case of a @code{FUNCTION_DECL}, @var{reloc} will be zero if the -function has been determined to be likely to be called, and nonzero if -it is unlikely to be called. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_UNIQUE_SECTION (tree @var{decl}, int @var{reloc}) -Build up a unique section name, expressed as a @code{STRING_CST} node, -and assign it to @samp{DECL_SECTION_NAME (@var{decl})}. -As with @code{TARGET_ASM_SELECT_SECTION}, @var{reloc} indicates whether -the initial value of @var{exp} requires link-time relocations. - -The default version of this function appends the symbol name to the -ELF section name that would normally be used for the symbol. For -example, the function @code{foo} would be placed in @code{.text.foo}. -Whatever the actual target object format, this is often good enough. -@end deftypefn - -@deftypefn {Target Hook} {section *} TARGET_ASM_FUNCTION_RODATA_SECTION (tree @var{decl}, bool @var{relocatable}) -Return the readonly data or reloc readonly data section associated with -@samp{DECL_SECTION_NAME (@var{decl})}. @var{relocatable} selects the latter -over the former. -The default version of this function selects @code{.gnu.linkonce.r.name} if -the function's section is @code{.gnu.linkonce.t.name}, @code{.rodata.name} -or @code{.data.rel.ro.name} if function is in @code{.text.name}, and -the normal readonly-data or reloc readonly data section otherwise. -@end deftypefn - -@deftypevr {Target Hook} {const char *} TARGET_ASM_MERGEABLE_RODATA_PREFIX -Usually, the compiler uses the prefix @code{".rodata"} to construct -section names for mergeable constant data. Define this macro to override -the string if a different section name should be used. -@end deftypevr - -@deftypefn {Target Hook} {section *} TARGET_ASM_TM_CLONE_TABLE_SECTION (void) -Return the section that should be used for transactional memory clone -tables. -@end deftypefn - -@deftypefn {Target Hook} {section *} TARGET_ASM_SELECT_RTX_SECTION (machine_mode @var{mode}, rtx @var{x}, unsigned HOST_WIDE_INT @var{align}) -Return the section into which a constant @var{x}, of mode @var{mode}, -should be placed. You can assume that @var{x} is some kind of -constant in RTL@. The argument @var{mode} is redundant except in the -case of a @code{const_int} rtx. @var{align} is the constant alignment -in bits. - -The default version of this function takes care of putting symbolic -constants in @code{flag_pic} mode in @code{data_section} and everything -else in @code{readonly_data_section}. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_MANGLE_DECL_ASSEMBLER_NAME (tree @var{decl}, tree @var{id}) -Define this hook if you need to postprocess the assembler name generated -by target-independent code. The @var{id} provided to this hook will be -the computed name (e.g., the macro @code{DECL_NAME} of the @var{decl} in C, -or the mangled name of the @var{decl} in C++). The return value of the -hook is an @code{IDENTIFIER_NODE} for the appropriate mangled name on -your target system. The default implementation of this hook just -returns the @var{id} provided. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ENCODE_SECTION_INFO (tree @var{decl}, rtx @var{rtl}, int @var{new_decl_p}) -Define this hook if references to a symbol or a constant must be -treated differently depending on something about the variable or -function named by the symbol (such as what section it is in). - -The hook is executed immediately after rtl has been created for -@var{decl}, which may be a variable or function declaration or -an entry in the constant pool. In either case, @var{rtl} is the -rtl in question. Do @emph{not} use @code{DECL_RTL (@var{decl})} -in this hook; that field may not have been initialized yet. - -In the case of a constant, it is safe to assume that the rtl is -a @code{mem} whose address is a @code{symbol_ref}. Most decls -will also have this form, but that is not guaranteed. Global -register variables, for instance, will have a @code{reg} for their -rtl. (Normally the right thing to do with such unusual rtl is -leave it alone.) - -The @var{new_decl_p} argument will be true if this is the first time -that @code{TARGET_ENCODE_SECTION_INFO} has been invoked on this decl. It will -be false for subsequent invocations, which will happen for duplicate -declarations. Whether or not anything must be done for the duplicate -declaration depends on whether the hook examines @code{DECL_ATTRIBUTES}. -@var{new_decl_p} is always true when the hook is called for a constant. - -@cindex @code{SYMBOL_REF_FLAG}, in @code{TARGET_ENCODE_SECTION_INFO} -The usual thing for this hook to do is to record flags in the -@code{symbol_ref}, using @code{SYMBOL_REF_FLAG} or @code{SYMBOL_REF_FLAGS}. -Historically, the name string was modified if it was necessary to -encode more than one bit of information, but this practice is now -discouraged; use @code{SYMBOL_REF_FLAGS}. - -The default definition of this hook, @code{default_encode_section_info} -in @file{varasm.cc}, sets a number of commonly-useful bits in -@code{SYMBOL_REF_FLAGS}. Check whether the default does what you need -before overriding it. -@end deftypefn - -@deftypefn {Target Hook} {const char *} TARGET_STRIP_NAME_ENCODING (const char *@var{name}) -Decode @var{name} and return the real name part, sans -the characters that @code{TARGET_ENCODE_SECTION_INFO} -may have added. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_IN_SMALL_DATA_P (const_tree @var{exp}) -Returns true if @var{exp} should be placed into a ``small data'' section. -The default version of this hook always returns false. -@end deftypefn - -@deftypevr {Target Hook} bool TARGET_HAVE_SRODATA_SECTION -Contains the value true if the target places read-only -``small data'' into a separate section. The default value is false. -@end deftypevr - -@deftypefn {Target Hook} bool TARGET_PROFILE_BEFORE_PROLOGUE (void) -It returns true if target wants profile code emitted before prologue. - -The default version of this hook use the target macro -@code{PROFILE_BEFORE_PROLOGUE}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_BINDS_LOCAL_P (const_tree @var{exp}) -Returns true if @var{exp} names an object for which name resolution -rules must resolve to the current ``module'' (dynamic shared library -or executable image). - -The default version of this hook implements the name resolution rules -for ELF, which has a looser model of global name binding than other -currently supported object file formats. -@end deftypefn - -@deftypevr {Target Hook} bool TARGET_HAVE_TLS -Contains the value true if the target supports thread-local storage. -The default value is false. -@end deftypevr - - -@node PIC -@section Position Independent Code -@cindex position independent code -@cindex PIC - -This section describes macros that help implement generation of position -independent code. Simply defining these macros is not enough to -generate valid PIC; you must also add support to the hook -@code{TARGET_LEGITIMATE_ADDRESS_P} and to the macro -@code{PRINT_OPERAND_ADDRESS}, as well as @code{LEGITIMIZE_ADDRESS}. You -must modify the definition of @samp{movsi} to do something appropriate -when the source operand contains a symbolic address. You may also -need to alter the handling of switch statements so that they use -relative addresses. -@c i rearranged the order of the macros above to try to force one of -@c them to the next line, to eliminate an overfull hbox. --mew 10feb93 - -@defmac PIC_OFFSET_TABLE_REGNUM -The register number of the register used to address a table of static -data addresses in memory. In some cases this register is defined by a -processor's ``application binary interface'' (ABI)@. When this macro -is defined, RTL is generated for this register once, as with the stack -pointer and frame pointer registers. If this macro is not defined, it -is up to the machine-dependent files to allocate such a register (if -necessary). Note that this register must be fixed when in use (e.g.@: -when @code{flag_pic} is true). -@end defmac - -@defmac PIC_OFFSET_TABLE_REG_CALL_CLOBBERED -A C expression that is nonzero if the register defined by -@code{PIC_OFFSET_TABLE_REGNUM} is clobbered by calls. If not defined, -the default is zero. Do not define -this macro if @code{PIC_OFFSET_TABLE_REGNUM} is not defined. -@end defmac - -@defmac LEGITIMATE_PIC_OPERAND_P (@var{x}) -A C expression that is nonzero if @var{x} is a legitimate immediate -operand on the target machine when generating position independent code. -You can assume that @var{x} satisfies @code{CONSTANT_P}, so you need not -check this. You can also assume @var{flag_pic} is true, so you need not -check it either. You need not define this macro if all constants -(including @code{SYMBOL_REF}) can be immediate operands when generating -position independent code. -@end defmac - -@node Assembler Format -@section Defining the Output Assembler Language - -This section describes macros whose principal purpose is to describe how -to write instructions in assembler language---rather than what the -instructions do. - -@menu -* File Framework:: Structural information for the assembler file. -* Data Output:: Output of constants (numbers, strings, addresses). -* Uninitialized Data:: Output of uninitialized variables. -* Label Output:: Output and generation of labels. -* Initialization:: General principles of initialization - and termination routines. -* Macros for Initialization:: - Specific macros that control the handling of - initialization and termination routines. -* Instruction Output:: Output of actual instructions. -* Dispatch Tables:: Output of jump tables. -* Exception Region Output:: Output of exception region code. -* Alignment Output:: Pseudo ops for alignment and skipping data. -@end menu - -@node File Framework -@subsection The Overall Framework of an Assembler File -@cindex assembler format -@cindex output of assembler code - -@c prevent bad page break with this line -This describes the overall framework of an assembly file. - -@findex default_file_start -@deftypefn {Target Hook} void TARGET_ASM_FILE_START (void) -Output to @code{asm_out_file} any text which the assembler expects to -find at the beginning of a file. The default behavior is controlled -by two flags, documented below. Unless your target's assembler is -quite unusual, if you override the default, you should call -@code{default_file_start} at some point in your target hook. This -lets other target files rely on these variables. -@end deftypefn - -@deftypevr {Target Hook} bool TARGET_ASM_FILE_START_APP_OFF -If this flag is true, the text of the macro @code{ASM_APP_OFF} will be -printed as the very first line in the assembly file, unless -@option{-fverbose-asm} is in effect. (If that macro has been defined -to the empty string, this variable has no effect.) With the normal -definition of @code{ASM_APP_OFF}, the effect is to notify the GNU -assembler that it need not bother stripping comments or extra -whitespace from its input. This allows it to work a bit faster. - -The default is false. You should not set it to true unless you have -verified that your port does not generate any extra whitespace or -comments that will cause GAS to issue errors in NO_APP mode. -@end deftypevr - -@deftypevr {Target Hook} bool TARGET_ASM_FILE_START_FILE_DIRECTIVE -If this flag is true, @code{output_file_directive} will be called -for the primary source file, immediately after printing -@code{ASM_APP_OFF} (if that is enabled). Most ELF assemblers expect -this to be done. The default is false. -@end deftypevr - -@deftypefn {Target Hook} void TARGET_ASM_FILE_END (void) -Output to @code{asm_out_file} any text which the assembler expects -to find at the end of a file. The default is to output nothing. -@end deftypefn - -@deftypefun void file_end_indicate_exec_stack () -Some systems use a common convention, the @samp{.note.GNU-stack} -special section, to indicate whether or not an object file relies on -the stack being executable. If your system uses this convention, you -should define @code{TARGET_ASM_FILE_END} to this function. If you -need to do other things in that hook, have your hook function call -this function. -@end deftypefun - -@deftypefn {Target Hook} void TARGET_ASM_LTO_START (void) -Output to @code{asm_out_file} any text which the assembler expects -to find at the start of an LTO section. The default is to output -nothing. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_LTO_END (void) -Output to @code{asm_out_file} any text which the assembler expects -to find at the end of an LTO section. The default is to output -nothing. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_CODE_END (void) -Output to @code{asm_out_file} any text which is needed before emitting -unwind info and debug info at the end of a file. Some targets emit -here PIC setup thunks that cannot be emitted at the end of file, -because they couldn't have unwind info then. The default is to output -nothing. -@end deftypefn - -@defmac ASM_COMMENT_START -A C string constant describing how to begin a comment in the target -assembler language. The compiler assumes that the comment will end at -the end of the line. -@end defmac - -@defmac ASM_APP_ON -A C string constant for text to be output before each @code{asm} -statement or group of consecutive ones. Normally this is -@code{"#APP"}, which is a comment that has no effect on most -assemblers but tells the GNU assembler that it must check the lines -that follow for all valid assembler constructs. -@end defmac - -@defmac ASM_APP_OFF -A C string constant for text to be output after each @code{asm} -statement or group of consecutive ones. Normally this is -@code{"#NO_APP"}, which tells the GNU assembler to resume making the -time-saving assumptions that are valid for ordinary compiler output. -@end defmac - -@defmac ASM_OUTPUT_SOURCE_FILENAME (@var{stream}, @var{name}) -A C statement to output COFF information or DWARF debugging information -which indicates that filename @var{name} is the current source file to -the stdio stream @var{stream}. - -This macro need not be defined if the standard form of output -for the file format in use is appropriate. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_OUTPUT_SOURCE_FILENAME (FILE *@var{file}, const char *@var{name}) -Output DWARF debugging information which indicates that filename -@var{name} is the current source file to the stdio stream @var{file}. - -This target hook need not be defined if the standard form of output -for the file format in use is appropriate. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_OUTPUT_IDENT (const char *@var{name}) -Output a string based on @var{name}, suitable for the @samp{#ident} -directive, or the equivalent directive or pragma in non-C-family languages. -If this hook is not defined, nothing is output for the @samp{#ident} -directive. -@end deftypefn - -@defmac OUTPUT_QUOTED_STRING (@var{stream}, @var{string}) -A C statement to output the string @var{string} to the stdio stream -@var{stream}. If you do not call the function @code{output_quoted_string} -in your config files, GCC will only call it to output filenames to -the assembler source. So you can use it to canonicalize the format -of the filename using this macro. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_NAMED_SECTION (const char *@var{name}, unsigned int @var{flags}, tree @var{decl}) -Output assembly directives to switch to section @var{name}. The section -should have attributes as specified by @var{flags}, which is a bit mask -of the @code{SECTION_*} flags defined in @file{output.h}. If @var{decl} -is non-NULL, it is the @code{VAR_DECL} or @code{FUNCTION_DECL} with which -this section is associated. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ASM_ELF_FLAGS_NUMERIC (unsigned int @var{flags}, unsigned int *@var{num}) -This hook can be used to encode ELF section flags for which no letter -code has been defined in the assembler. It is called by -@code{default_asm_named_section} whenever the section flags need to be -emitted in the assembler output. If the hook returns true, then the -numerical value for ELF section flags should be calculated from -@var{flags} and saved in @var{*num}; the value is printed out instead of the -normal sequence of letter codes. If the hook is not defined, or if it -returns false, then @var{num} is ignored and the traditional letter sequence -is emitted. -@end deftypefn - -@deftypefn {Target Hook} {section *} TARGET_ASM_FUNCTION_SECTION (tree @var{decl}, enum node_frequency @var{freq}, bool @var{startup}, bool @var{exit}) -Return preferred text (sub)section for function @var{decl}. -Main purpose of this function is to separate cold, normal and hot -functions. @var{startup} is true when function is known to be used only -at startup (from static constructors or it is @code{main()}). -@var{exit} is true when function is known to be used only at exit -(from static destructors). -Return NULL if function should go to default text section. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_FUNCTION_SWITCHED_TEXT_SECTIONS (FILE *@var{file}, tree @var{decl}, bool @var{new_is_cold}) -Used by the target to emit any assembler directives or additional -labels needed when a function is partitioned between different -sections. Output should be written to @var{file}. The function -decl is available as @var{decl} and the new section is `cold' if -@var{new_is_cold} is @code{true}. -@end deftypefn - -@deftypevr {Common Target Hook} bool TARGET_HAVE_NAMED_SECTIONS -This flag is true if the target supports @code{TARGET_ASM_NAMED_SECTION}. -It must not be modified by command-line option processing. -@end deftypevr - -@anchor{TARGET_HAVE_SWITCHABLE_BSS_SECTIONS} -@deftypevr {Target Hook} bool TARGET_HAVE_SWITCHABLE_BSS_SECTIONS -This flag is true if we can create zeroed data by switching to a BSS -section and then using @code{ASM_OUTPUT_SKIP} to allocate the space. -This is true on most ELF targets. -@end deftypevr - -@deftypefn {Target Hook} {unsigned int} TARGET_SECTION_TYPE_FLAGS (tree @var{decl}, const char *@var{name}, int @var{reloc}) -Choose a set of section attributes for use by @code{TARGET_ASM_NAMED_SECTION} -based on a variable or function decl, a section name, and whether or not the -declaration's initializer may contain runtime relocations. @var{decl} may be -null, in which case read-write data should be assumed. - -The default version of this function handles choosing code vs data, -read-only vs read-write data, and @code{flag_pic}. You should only -need to override this if your target has special flags that might be -set via @code{__attribute__}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_RECORD_GCC_SWITCHES (const char *@var{}) -Provides the target with the ability to record the gcc command line -switches provided as argument. - -By default this hook is set to NULL, but an example implementation is -provided for ELF based targets. Called @var{elf_record_gcc_switches}, -it records the switches as ASCII text inside a new, string mergeable -section in the assembler output file. The name of the new section is -provided by the @code{TARGET_ASM_RECORD_GCC_SWITCHES_SECTION} target -hook. -@end deftypefn - -@deftypevr {Target Hook} {const char *} TARGET_ASM_RECORD_GCC_SWITCHES_SECTION -This is the name of the section that will be created by the example -ELF implementation of the @code{TARGET_ASM_RECORD_GCC_SWITCHES} target -hook. -@end deftypevr - -@need 2000 -@node Data Output -@subsection Output of Data - - -@deftypevr {Target Hook} {const char *} TARGET_ASM_BYTE_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_HI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_PSI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_SI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_PDI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_DI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_PTI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_TI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_HI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_PSI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_SI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_PDI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_DI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_PTI_OP -@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_TI_OP -These hooks specify assembly directives for creating certain kinds -of integer object. The @code{TARGET_ASM_BYTE_OP} directive creates a -byte-sized object, the @code{TARGET_ASM_ALIGNED_HI_OP} one creates an -aligned two-byte object, and so on. Any of the hooks may be -@code{NULL}, indicating that no suitable directive is available. - -The compiler will print these strings at the start of a new line, -followed immediately by the object's initial value. In most cases, -the string should contain a tab, a pseudo-op, and then another tab. -@end deftypevr - -@deftypefn {Target Hook} bool TARGET_ASM_INTEGER (rtx @var{x}, unsigned int @var{size}, int @var{aligned_p}) -The @code{assemble_integer} function uses this hook to output an -integer object. @var{x} is the object's value, @var{size} is its size -in bytes and @var{aligned_p} indicates whether it is aligned. The -function should return @code{true} if it was able to output the -object. If it returns false, @code{assemble_integer} will try to -split the object into smaller parts. - -The default implementation of this hook will use the -@code{TARGET_ASM_BYTE_OP} family of strings, returning @code{false} -when the relevant string is @code{NULL}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_DECL_END (void) -Define this hook if the target assembler requires a special marker to -terminate an initialized variable declaration. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ASM_OUTPUT_ADDR_CONST_EXTRA (FILE *@var{file}, rtx @var{x}) -A target hook to recognize @var{rtx} patterns that @code{output_addr_const} -can't deal with, and output assembly code to @var{file} corresponding to -the pattern @var{x}. This may be used to allow machine-dependent -@code{UNSPEC}s to appear within constants. - -If target hook fails to recognize a pattern, it must return @code{false}, -so that a standard error message is printed. If it prints an error message -itself, by calling, for example, @code{output_operand_lossage}, it may just -return @code{true}. -@end deftypefn - -@defmac ASM_OUTPUT_ASCII (@var{stream}, @var{ptr}, @var{len}) -A C statement to output to the stdio stream @var{stream} an assembler -instruction to assemble a string constant containing the @var{len} -bytes at @var{ptr}. @var{ptr} will be a C expression of type -@code{char *} and @var{len} a C expression of type @code{int}. - -If the assembler has a @code{.ascii} pseudo-op as found in the -Berkeley Unix assembler, do not define the macro -@code{ASM_OUTPUT_ASCII}. -@end defmac - -@defmac ASM_OUTPUT_FDESC (@var{stream}, @var{decl}, @var{n}) -A C statement to output word @var{n} of a function descriptor for -@var{decl}. This must be defined if @code{TARGET_VTABLE_USES_DESCRIPTORS} -is defined, and is otherwise unused. -@end defmac - -@defmac CONSTANT_POOL_BEFORE_FUNCTION -You may define this macro as a C expression. You should define the -expression to have a nonzero value if GCC should output the constant -pool for a function before the code for the function, or a zero value if -GCC should output the constant pool after the function. If you do -not define this macro, the usual case, GCC will output the constant -pool before the function. -@end defmac - -@defmac ASM_OUTPUT_POOL_PROLOGUE (@var{file}, @var{funname}, @var{fundecl}, @var{size}) -A C statement to output assembler commands to define the start of the -constant pool for a function. @var{funname} is a string giving -the name of the function. Should the return type of the function -be required, it can be obtained via @var{fundecl}. @var{size} -is the size, in bytes, of the constant pool that will be written -immediately after this call. - -If no constant-pool prefix is required, the usual case, this macro need -not be defined. -@end defmac - -@defmac ASM_OUTPUT_SPECIAL_POOL_ENTRY (@var{file}, @var{x}, @var{mode}, @var{align}, @var{labelno}, @var{jumpto}) -A C statement (with or without semicolon) to output a constant in the -constant pool, if it needs special treatment. (This macro need not do -anything for RTL expressions that can be output normally.) - -The argument @var{file} is the standard I/O stream to output the -assembler code on. @var{x} is the RTL expression for the constant to -output, and @var{mode} is the machine mode (in case @var{x} is a -@samp{const_int}). @var{align} is the required alignment for the value -@var{x}; you should output an assembler directive to force this much -alignment. - -The argument @var{labelno} is a number to use in an internal label for -the address of this pool entry. The definition of this macro is -responsible for outputting the label definition at the proper place. -Here is how to do this: - -@smallexample -@code{(*targetm.asm_out.internal_label)} (@var{file}, "LC", @var{labelno}); -@end smallexample - -When you output a pool entry specially, you should end with a -@code{goto} to the label @var{jumpto}. This will prevent the same pool -entry from being output a second time in the usual manner. - -You need not define this macro if it would do nothing. -@end defmac - -@defmac ASM_OUTPUT_POOL_EPILOGUE (@var{file} @var{funname} @var{fundecl} @var{size}) -A C statement to output assembler commands to at the end of the constant -pool for a function. @var{funname} is a string giving the name of the -function. Should the return type of the function be required, you can -obtain it via @var{fundecl}. @var{size} is the size, in bytes, of the -constant pool that GCC wrote immediately before this call. - -If no constant-pool epilogue is required, the usual case, you need not -define this macro. -@end defmac - -@defmac IS_ASM_LOGICAL_LINE_SEPARATOR (@var{C}, @var{STR}) -Define this macro as a C expression which is nonzero if @var{C} is -used as a logical line separator by the assembler. @var{STR} points -to the position in the string where @var{C} was found; this can be used if -a line separator uses multiple characters. - -If you do not define this macro, the default is that only -the character @samp{;} is treated as a logical line separator. -@end defmac - -@deftypevr {Target Hook} {const char *} TARGET_ASM_OPEN_PAREN -@deftypevrx {Target Hook} {const char *} TARGET_ASM_CLOSE_PAREN -These target hooks are C string constants, describing the syntax in the -assembler for grouping arithmetic expressions. If not overridden, they -default to normal parentheses, which is correct for most assemblers. -@end deftypevr - -These macros are provided by @file{real.h} for writing the definitions -of @code{ASM_OUTPUT_DOUBLE} and the like: - -@defmac REAL_VALUE_TO_TARGET_SINGLE (@var{x}, @var{l}) -@defmacx REAL_VALUE_TO_TARGET_DOUBLE (@var{x}, @var{l}) -@defmacx REAL_VALUE_TO_TARGET_LONG_DOUBLE (@var{x}, @var{l}) -@defmacx REAL_VALUE_TO_TARGET_DECIMAL32 (@var{x}, @var{l}) -@defmacx REAL_VALUE_TO_TARGET_DECIMAL64 (@var{x}, @var{l}) -@defmacx REAL_VALUE_TO_TARGET_DECIMAL128 (@var{x}, @var{l}) -These translate @var{x}, of type @code{REAL_VALUE_TYPE}, to the -target's floating point representation, and store its bit pattern in -the variable @var{l}. For @code{REAL_VALUE_TO_TARGET_SINGLE} and -@code{REAL_VALUE_TO_TARGET_DECIMAL32}, this variable should be a -simple @code{long int}. For the others, it should be an array of -@code{long int}. The number of elements in this array is determined -by the size of the desired target floating point data type: 32 bits of -it go in each @code{long int} array element. Each array element holds -32 bits of the result, even if @code{long int} is wider than 32 bits -on the host machine. - -The array element values are designed so that you can print them out -using @code{fprintf} in the order they should appear in the target -machine's memory. -@end defmac - -@node Uninitialized Data -@subsection Output of Uninitialized Variables - -Each of the macros in this section is used to do the whole job of -outputting a single uninitialized variable. - -@defmac ASM_OUTPUT_COMMON (@var{stream}, @var{name}, @var{size}, @var{rounded}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} the assembler definition of a common-label named -@var{name} whose size is @var{size} bytes. The variable @var{rounded} -is the size rounded up to whatever alignment the caller wants. It is -possible that @var{size} may be zero, for instance if a struct with no -other member than a zero-length array is defined. In this case, the -backend must output a symbol definition that allocates at least one -byte, both so that the address of the resulting object does not compare -equal to any other, and because some object formats cannot even express -the concept of a zero-sized common symbol, as that is how they represent -an ordinary undefined external. - -Use the expression @code{assemble_name (@var{stream}, @var{name})} to -output the name itself; before and after that, output the additional -assembler syntax for defining the name, and a newline. - -This macro controls how the assembler definitions of uninitialized -common global variables are output. -@end defmac - -@defmac ASM_OUTPUT_ALIGNED_COMMON (@var{stream}, @var{name}, @var{size}, @var{alignment}) -Like @code{ASM_OUTPUT_COMMON} except takes the required alignment as a -separate, explicit argument. If you define this macro, it is used in -place of @code{ASM_OUTPUT_COMMON}, and gives you more flexibility in -handling the required alignment of the variable. The alignment is specified -as the number of bits. -@end defmac - -@defmac ASM_OUTPUT_ALIGNED_DECL_COMMON (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) -Like @code{ASM_OUTPUT_ALIGNED_COMMON} except that @var{decl} of the -variable to be output, if there is one, or @code{NULL_TREE} if there -is no corresponding variable. If you define this macro, GCC will use it -in place of both @code{ASM_OUTPUT_COMMON} and -@code{ASM_OUTPUT_ALIGNED_COMMON}. Define this macro when you need to see -the variable's decl in order to chose what to output. -@end defmac - -@defmac ASM_OUTPUT_ALIGNED_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} the assembler definition of uninitialized global @var{decl} named -@var{name} whose size is @var{size} bytes. The variable @var{alignment} -is the alignment specified as the number of bits. - -Try to use function @code{asm_output_aligned_bss} defined in file -@file{varasm.cc} when defining this macro. If unable, use the expression -@code{assemble_name (@var{stream}, @var{name})} to output the name itself; -before and after that, output the additional assembler syntax for defining -the name, and a newline. - -There are two ways of handling global BSS@. One is to define this macro. -The other is to have @code{TARGET_ASM_SELECT_SECTION} return a -switchable BSS section (@pxref{TARGET_HAVE_SWITCHABLE_BSS_SECTIONS}). -You do not need to do both. - -Some languages do not have @code{common} data, and require a -non-common form of global BSS in order to handle uninitialized globals -efficiently. C++ is one example of this. However, if the target does -not support global BSS, the front end may choose to make globals -common in order to save space in the object file. -@end defmac - -@defmac ASM_OUTPUT_LOCAL (@var{stream}, @var{name}, @var{size}, @var{rounded}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} the assembler definition of a local-common-label named -@var{name} whose size is @var{size} bytes. The variable @var{rounded} -is the size rounded up to whatever alignment the caller wants. - -Use the expression @code{assemble_name (@var{stream}, @var{name})} to -output the name itself; before and after that, output the additional -assembler syntax for defining the name, and a newline. - -This macro controls how the assembler definitions of uninitialized -static variables are output. -@end defmac - -@defmac ASM_OUTPUT_ALIGNED_LOCAL (@var{stream}, @var{name}, @var{size}, @var{alignment}) -Like @code{ASM_OUTPUT_LOCAL} except takes the required alignment as a -separate, explicit argument. If you define this macro, it is used in -place of @code{ASM_OUTPUT_LOCAL}, and gives you more flexibility in -handling the required alignment of the variable. The alignment is specified -as the number of bits. -@end defmac - -@defmac ASM_OUTPUT_ALIGNED_DECL_LOCAL (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment}) -Like @code{ASM_OUTPUT_ALIGNED_LOCAL} except that @var{decl} of the -variable to be output, if there is one, or @code{NULL_TREE} if there -is no corresponding variable. If you define this macro, GCC will use it -in place of both @code{ASM_OUTPUT_LOCAL} and -@code{ASM_OUTPUT_ALIGNED_LOCAL}. Define this macro when you need to see -the variable's decl in order to chose what to output. -@end defmac - -@node Label Output -@subsection Output and Generation of Labels - -@c prevent bad page break with this line -This is about outputting labels. - -@findex assemble_name -@defmac ASM_OUTPUT_LABEL (@var{stream}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} the assembler definition of a label named @var{name}. -Use the expression @code{assemble_name (@var{stream}, @var{name})} to -output the name itself; before and after that, output the additional -assembler syntax for defining the name, and a newline. A default -definition of this macro is provided which is correct for most systems. -@end defmac - -@defmac ASM_OUTPUT_FUNCTION_LABEL (@var{stream}, @var{name}, @var{decl}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} the assembler definition of a label named @var{name} of -a function. -Use the expression @code{assemble_name (@var{stream}, @var{name})} to -output the name itself; before and after that, output the additional -assembler syntax for defining the name, and a newline. A default -definition of this macro is provided which is correct for most systems. - -If this macro is not defined, then the function name is defined in the -usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). -@end defmac - -@findex assemble_name_raw -@defmac ASM_OUTPUT_INTERNAL_LABEL (@var{stream}, @var{name}) -Identical to @code{ASM_OUTPUT_LABEL}, except that @var{name} is known -to refer to a compiler-generated label. The default definition uses -@code{assemble_name_raw}, which is like @code{assemble_name} except -that it is more efficient. -@end defmac - -@defmac SIZE_ASM_OP -A C string containing the appropriate assembler directive to specify the -size of a symbol, without any arguments. On systems that use ELF, the -default (in @file{config/elfos.h}) is @samp{"\t.size\t"}; on other -systems, the default is not to define this macro. - -Define this macro only if it is correct to use the default definitions -of @code{ASM_OUTPUT_SIZE_DIRECTIVE} and @code{ASM_OUTPUT_MEASURED_SIZE} -for your system. If you need your own custom definitions of those -macros, or if you do not need explicit symbol sizes at all, do not -define this macro. -@end defmac - -@defmac ASM_OUTPUT_SIZE_DIRECTIVE (@var{stream}, @var{name}, @var{size}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} a directive telling the assembler that the size of the -symbol @var{name} is @var{size}. @var{size} is a @code{HOST_WIDE_INT}. -If you define @code{SIZE_ASM_OP}, a default definition of this macro is -provided. -@end defmac - -@defmac ASM_OUTPUT_MEASURED_SIZE (@var{stream}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} a directive telling the assembler to calculate the size of -the symbol @var{name} by subtracting its address from the current -address. - -If you define @code{SIZE_ASM_OP}, a default definition of this macro is -provided. The default assumes that the assembler recognizes a special -@samp{.} symbol as referring to the current address, and can calculate -the difference between this and another symbol. If your assembler does -not recognize @samp{.} or cannot do calculations with it, you will need -to redefine @code{ASM_OUTPUT_MEASURED_SIZE} to use some other technique. -@end defmac - -@defmac NO_DOLLAR_IN_LABEL -Define this macro if the assembler does not accept the character -@samp{$} in label names. By default constructors and destructors in -G++ have @samp{$} in the identifiers. If this macro is defined, -@samp{.} is used instead. -@end defmac - -@defmac NO_DOT_IN_LABEL -Define this macro if the assembler does not accept the character -@samp{.} in label names. By default constructors and destructors in G++ -have names that use @samp{.}. If this macro is defined, these names -are rewritten to avoid @samp{.}. -@end defmac - -@defmac TYPE_ASM_OP -A C string containing the appropriate assembler directive to specify the -type of a symbol, without any arguments. On systems that use ELF, the -default (in @file{config/elfos.h}) is @samp{"\t.type\t"}; on other -systems, the default is not to define this macro. - -Define this macro only if it is correct to use the default definition of -@code{ASM_OUTPUT_TYPE_DIRECTIVE} for your system. If you need your own -custom definition of this macro, or if you do not need explicit symbol -types at all, do not define this macro. -@end defmac - -@defmac TYPE_OPERAND_FMT -A C string which specifies (using @code{printf} syntax) the format of -the second operand to @code{TYPE_ASM_OP}. On systems that use ELF, the -default (in @file{config/elfos.h}) is @samp{"@@%s"}; on other systems, -the default is not to define this macro. - -Define this macro only if it is correct to use the default definition of -@code{ASM_OUTPUT_TYPE_DIRECTIVE} for your system. If you need your own -custom definition of this macro, or if you do not need explicit symbol -types at all, do not define this macro. -@end defmac - -@defmac ASM_OUTPUT_TYPE_DIRECTIVE (@var{stream}, @var{type}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} a directive telling the assembler that the type of the -symbol @var{name} is @var{type}. @var{type} is a C string; currently, -that string is always either @samp{"function"} or @samp{"object"}, but -you should not count on this. - -If you define @code{TYPE_ASM_OP} and @code{TYPE_OPERAND_FMT}, a default -definition of this macro is provided. -@end defmac - -@defmac ASM_DECLARE_FUNCTION_NAME (@var{stream}, @var{name}, @var{decl}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for declaring the name @var{name} of a -function which is being defined. This macro is responsible for -outputting the label definition (perhaps using -@code{ASM_OUTPUT_FUNCTION_LABEL}). The argument @var{decl} is the -@code{FUNCTION_DECL} tree node representing the function. - -If this macro is not defined, then the function name is defined in the -usual manner as a label (by means of @code{ASM_OUTPUT_FUNCTION_LABEL}). - -You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} in the definition -of this macro. -@end defmac - -@defmac ASM_DECLARE_FUNCTION_SIZE (@var{stream}, @var{name}, @var{decl}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for declaring the size of a function -which is being defined. The argument @var{name} is the name of the -function. The argument @var{decl} is the @code{FUNCTION_DECL} tree node -representing the function. - -If this macro is not defined, then the function size is not defined. - -You may wish to use @code{ASM_OUTPUT_MEASURED_SIZE} in the definition -of this macro. -@end defmac - -@defmac ASM_DECLARE_COLD_FUNCTION_NAME (@var{stream}, @var{name}, @var{decl}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for declaring the name @var{name} of a -cold function partition which is being defined. This macro is responsible -for outputting the label definition (perhaps using -@code{ASM_OUTPUT_FUNCTION_LABEL}). The argument @var{decl} is the -@code{FUNCTION_DECL} tree node representing the function. - -If this macro is not defined, then the cold partition name is defined in the -usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). - -You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} in the definition -of this macro. -@end defmac - -@defmac ASM_DECLARE_COLD_FUNCTION_SIZE (@var{stream}, @var{name}, @var{decl}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for declaring the size of a cold function -partition which is being defined. The argument @var{name} is the name of the -cold partition of the function. The argument @var{decl} is the -@code{FUNCTION_DECL} tree node representing the function. - -If this macro is not defined, then the partition size is not defined. - -You may wish to use @code{ASM_OUTPUT_MEASURED_SIZE} in the definition -of this macro. -@end defmac - -@defmac ASM_DECLARE_OBJECT_NAME (@var{stream}, @var{name}, @var{decl}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for declaring the name @var{name} of an -initialized variable which is being defined. This macro must output the -label definition (perhaps using @code{ASM_OUTPUT_LABEL}). The argument -@var{decl} is the @code{VAR_DECL} tree node representing the variable. - -If this macro is not defined, then the variable name is defined in the -usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}). - -You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} and/or -@code{ASM_OUTPUT_SIZE_DIRECTIVE} in the definition of this macro. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_DECLARE_CONSTANT_NAME (FILE *@var{file}, const char *@var{name}, const_tree @var{expr}, HOST_WIDE_INT @var{size}) -A target hook to output to the stdio stream @var{file} any text necessary -for declaring the name @var{name} of a constant which is being defined. This -target hook is responsible for outputting the label definition (perhaps using -@code{assemble_label}). The argument @var{exp} is the value of the constant, -and @var{size} is the size of the constant in bytes. The @var{name} -will be an internal label. - -The default version of this target hook, define the @var{name} in the -usual manner as a label (by means of @code{assemble_label}). - -You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} in this target hook. -@end deftypefn - -@defmac ASM_DECLARE_REGISTER_GLOBAL (@var{stream}, @var{decl}, @var{regno}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for claiming a register @var{regno} -for a global variable @var{decl} with name @var{name}. - -If you don't define this macro, that is equivalent to defining it to do -nothing. -@end defmac - -@defmac ASM_FINISH_DECLARE_OBJECT (@var{stream}, @var{decl}, @var{toplevel}, @var{atend}) -A C statement (sans semicolon) to finish up declaring a variable name -once the compiler has processed its initializer fully and thus has had a -chance to determine the size of an array when controlled by an -initializer. This is used on systems where it's necessary to declare -something about the size of the object. - -If you don't define this macro, that is equivalent to defining it to do -nothing. - -You may wish to use @code{ASM_OUTPUT_SIZE_DIRECTIVE} and/or -@code{ASM_OUTPUT_MEASURED_SIZE} in the definition of this macro. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_GLOBALIZE_LABEL (FILE *@var{stream}, const char *@var{name}) -This target hook is a function to output to the stdio stream -@var{stream} some commands that will make the label @var{name} global; -that is, available for reference from other files. - -The default implementation relies on a proper definition of -@code{GLOBAL_ASM_OP}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_GLOBALIZE_DECL_NAME (FILE *@var{stream}, tree @var{decl}) -This target hook is a function to output to the stdio stream -@var{stream} some commands that will make the name associated with @var{decl} -global; that is, available for reference from other files. - -The default implementation uses the TARGET_ASM_GLOBALIZE_LABEL target hook. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_ASSEMBLE_UNDEFINED_DECL (FILE *@var{stream}, const char *@var{name}, const_tree @var{decl}) -This target hook is a function to output to the stdio stream -@var{stream} some commands that will declare the name associated with -@var{decl} which is not defined in the current translation unit. Most -assemblers do not require anything to be output in this case. -@end deftypefn - -@defmac ASM_WEAKEN_LABEL (@var{stream}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} some commands that will make the label @var{name} weak; -that is, available for reference from other files but only used if -no other definition is available. Use the expression -@code{assemble_name (@var{stream}, @var{name})} to output the name -itself; before and after that, output the additional assembler syntax -for making that name weak, and a newline. - -If you don't define this macro or @code{ASM_WEAKEN_DECL}, GCC will not -support weak symbols and you should not define the @code{SUPPORTS_WEAK} -macro. -@end defmac - -@defmac ASM_WEAKEN_DECL (@var{stream}, @var{decl}, @var{name}, @var{value}) -Combines (and replaces) the function of @code{ASM_WEAKEN_LABEL} and -@code{ASM_OUTPUT_WEAK_ALIAS}, allowing access to the associated function -or variable decl. If @var{value} is not @code{NULL}, this C statement -should output to the stdio stream @var{stream} assembler code which -defines (equates) the weak symbol @var{name} to have the value -@var{value}. If @var{value} is @code{NULL}, it should output commands -to make @var{name} weak. -@end defmac - -@defmac ASM_OUTPUT_WEAKREF (@var{stream}, @var{decl}, @var{name}, @var{value}) -Outputs a directive that enables @var{name} to be used to refer to -symbol @var{value} with weak-symbol semantics. @code{decl} is the -declaration of @code{name}. -@end defmac - -@defmac SUPPORTS_WEAK -A preprocessor constant expression which evaluates to true if the target -supports weak symbols. - -If you don't define this macro, @file{defaults.h} provides a default -definition. If either @code{ASM_WEAKEN_LABEL} or @code{ASM_WEAKEN_DECL} -is defined, the default definition is @samp{1}; otherwise, it is @samp{0}. -@end defmac - -@defmac TARGET_SUPPORTS_WEAK -A C expression which evaluates to true if the target supports weak symbols. - -If you don't define this macro, @file{defaults.h} provides a default -definition. The default definition is @samp{(SUPPORTS_WEAK)}. Define -this macro if you want to control weak symbol support with a compiler -flag such as @option{-melf}. -@end defmac - -@defmac MAKE_DECL_ONE_ONLY (@var{decl}) -A C statement (sans semicolon) to mark @var{decl} to be emitted as a -public symbol such that extra copies in multiple translation units will -be discarded by the linker. Define this macro if your object file -format provides support for this concept, such as the @samp{COMDAT} -section flags in the Microsoft Windows PE/COFF format, and this support -requires changes to @var{decl}, such as putting it in a separate section. -@end defmac - -@defmac SUPPORTS_ONE_ONLY -A C expression which evaluates to true if the target supports one-only -semantics. - -If you don't define this macro, @file{varasm.cc} provides a default -definition. If @code{MAKE_DECL_ONE_ONLY} is defined, the default -definition is @samp{1}; otherwise, it is @samp{0}. Define this macro if -you want to control one-only symbol support with a compiler flag, or if -setting the @code{DECL_ONE_ONLY} flag is enough to mark a declaration to -be emitted as one-only. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_ASSEMBLE_VISIBILITY (tree @var{decl}, int @var{visibility}) -This target hook is a function to output to @var{asm_out_file} some -commands that will make the symbol(s) associated with @var{decl} have -hidden, protected or internal visibility as specified by @var{visibility}. -@end deftypefn - -@defmac TARGET_WEAK_NOT_IN_ARCHIVE_TOC -A C expression that evaluates to true if the target's linker expects -that weak symbols do not appear in a static archive's table of contents. -The default is @code{0}. - -Leaving weak symbols out of an archive's table of contents means that, -if a symbol will only have a definition in one translation unit and -will have undefined references from other translation units, that -symbol should not be weak. Defining this macro to be nonzero will -thus have the effect that certain symbols that would normally be weak -(explicit template instantiations, and vtables for polymorphic classes -with noninline key methods) will instead be nonweak. - -The C++ ABI requires this macro to be zero. Define this macro for -targets where full C++ ABI compliance is impossible and where linker -restrictions require weak symbols to be left out of a static archive's -table of contents. -@end defmac - -@defmac ASM_OUTPUT_EXTERNAL (@var{stream}, @var{decl}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} any text necessary for declaring the name of an external -symbol named @var{name} which is referenced in this compilation but -not defined. The value of @var{decl} is the tree node for the -declaration. - -This macro need not be defined if it does not need to output anything. -The GNU assembler and most Unix assemblers don't require anything. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_EXTERNAL_LIBCALL (rtx @var{symref}) -This target hook is a function to output to @var{asm_out_file} an assembler -pseudo-op to declare a library function name external. The name of the -library function is given by @var{symref}, which is a @code{symbol_ref}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_MARK_DECL_PRESERVED (const char *@var{symbol}) -This target hook is a function to output to @var{asm_out_file} an assembler -directive to annotate @var{symbol} as used. The Darwin target uses the -.no_dead_code_strip directive. -@end deftypefn - -@defmac ASM_OUTPUT_LABELREF (@var{stream}, @var{name}) -A C statement (sans semicolon) to output to the stdio stream -@var{stream} a reference in assembler syntax to a label named -@var{name}. This should add @samp{_} to the front of the name, if that -is customary on your operating system, as it is in most Berkeley Unix -systems. This macro is used in @code{assemble_name}. -@end defmac - -@deftypefn {Target Hook} tree TARGET_MANGLE_ASSEMBLER_NAME (const char *@var{name}) -Given a symbol @var{name}, perform same mangling as @code{varasm.cc}'s -@code{assemble_name}, but in memory rather than to a file stream, returning -result as an @code{IDENTIFIER_NODE}. Required for correct LTO symtabs. The -default implementation calls the @code{TARGET_STRIP_NAME_ENCODING} hook and -then prepends the @code{USER_LABEL_PREFIX}, if any. -@end deftypefn - -@defmac ASM_OUTPUT_SYMBOL_REF (@var{stream}, @var{sym}) -A C statement (sans semicolon) to output a reference to -@code{SYMBOL_REF} @var{sym}. If not defined, @code{assemble_name} -will be used to output the name of the symbol. This macro may be used -to modify the way a symbol is referenced depending on information -encoded by @code{TARGET_ENCODE_SECTION_INFO}. -@end defmac - -@defmac ASM_OUTPUT_LABEL_REF (@var{stream}, @var{buf}) -A C statement (sans semicolon) to output a reference to @var{buf}, the -result of @code{ASM_GENERATE_INTERNAL_LABEL}. If not defined, -@code{assemble_name} will be used to output the name of the symbol. -This macro is not used by @code{output_asm_label}, or the @code{%l} -specifier that calls it; the intention is that this macro should be set -when it is necessary to output a label differently when its address is -being taken. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_INTERNAL_LABEL (FILE *@var{stream}, const char *@var{prefix}, unsigned long @var{labelno}) -A function to output to the stdio stream @var{stream} a label whose -name is made from the string @var{prefix} and the number @var{labelno}. - -It is absolutely essential that these labels be distinct from the labels -used for user-level functions and variables. Otherwise, certain programs -will have name conflicts with internal labels. - -It is desirable to exclude internal labels from the symbol table of the -object file. Most assemblers have a naming convention for labels that -should be excluded; on many systems, the letter @samp{L} at the -beginning of a label has this effect. You should find out what -convention your system uses, and follow it. - -The default version of this function utilizes @code{ASM_GENERATE_INTERNAL_LABEL}. -@end deftypefn - -@defmac ASM_OUTPUT_DEBUG_LABEL (@var{stream}, @var{prefix}, @var{num}) -A C statement to output to the stdio stream @var{stream} a debug info -label whose name is made from the string @var{prefix} and the number -@var{num}. This is useful for VLIW targets, where debug info labels -may need to be treated differently than branch target labels. On some -systems, branch target labels must be at the beginning of instruction -bundles, but debug info labels can occur in the middle of instruction -bundles. - -If this macro is not defined, then @code{(*targetm.asm_out.internal_label)} will be -used. -@end defmac - -@defmac ASM_GENERATE_INTERNAL_LABEL (@var{string}, @var{prefix}, @var{num}) -A C statement to store into the string @var{string} a label whose name -is made from the string @var{prefix} and the number @var{num}. - -This string, when output subsequently by @code{assemble_name}, should -produce the output that @code{(*targetm.asm_out.internal_label)} would produce -with the same @var{prefix} and @var{num}. - -If the string begins with @samp{*}, then @code{assemble_name} will -output the rest of the string unchanged. It is often convenient for -@code{ASM_GENERATE_INTERNAL_LABEL} to use @samp{*} in this way. If the -string doesn't start with @samp{*}, then @code{ASM_OUTPUT_LABELREF} gets -to output the string, and may change it. (Of course, -@code{ASM_OUTPUT_LABELREF} is also part of your machine description, so -you should know what it does on your machine.) -@end defmac - -@defmac ASM_FORMAT_PRIVATE_NAME (@var{outvar}, @var{name}, @var{number}) -A C expression to assign to @var{outvar} (which is a variable of type -@code{char *}) a newly allocated string made from the string -@var{name} and the number @var{number}, with some suitable punctuation -added. Use @code{alloca} to get space for the string. - -The string will be used as an argument to @code{ASM_OUTPUT_LABELREF} to -produce an assembler label for an internal static variable whose name is -@var{name}. Therefore, the string must be such as to result in valid -assembler code. The argument @var{number} is different each time this -macro is executed; it prevents conflicts between similarly-named -internal static variables in different scopes. - -Ideally this string should not be a valid C identifier, to prevent any -conflict with the user's own symbols. Most assemblers allow periods -or percent signs in assembler symbols; putting at least one of these -between the name and the number will suffice. - -If this macro is not defined, a default definition will be provided -which is correct for most systems. -@end defmac - -@defmac ASM_OUTPUT_DEF (@var{stream}, @var{name}, @var{value}) -A C statement to output to the stdio stream @var{stream} assembler code -which defines (equates) the symbol @var{name} to have the value @var{value}. - -@findex SET_ASM_OP -If @code{SET_ASM_OP} is defined, a default definition is provided which is -correct for most systems. -@end defmac - -@defmac ASM_OUTPUT_DEF_FROM_DECLS (@var{stream}, @var{decl_of_name}, @var{decl_of_value}) -A C statement to output to the stdio stream @var{stream} assembler code -which defines (equates) the symbol whose tree node is @var{decl_of_name} -to have the value of the tree node @var{decl_of_value}. This macro will -be used in preference to @samp{ASM_OUTPUT_DEF} if it is defined and if -the tree nodes are available. - -@findex SET_ASM_OP -If @code{SET_ASM_OP} is defined, a default definition is provided which is -correct for most systems. -@end defmac - -@defmac TARGET_DEFERRED_OUTPUT_DEFS (@var{decl_of_name}, @var{decl_of_value}) -A C statement that evaluates to true if the assembler code which defines -(equates) the symbol whose tree node is @var{decl_of_name} to have the value -of the tree node @var{decl_of_value} should be emitted near the end of the -current compilation unit. The default is to not defer output of defines. -This macro affects defines output by @samp{ASM_OUTPUT_DEF} and -@samp{ASM_OUTPUT_DEF_FROM_DECLS}. -@end defmac - -@defmac ASM_OUTPUT_WEAK_ALIAS (@var{stream}, @var{name}, @var{value}) -A C statement to output to the stdio stream @var{stream} assembler code -which defines (equates) the weak symbol @var{name} to have the value -@var{value}. If @var{value} is @code{NULL}, it defines @var{name} as -an undefined weak symbol. - -Define this macro if the target only supports weak aliases; define -@code{ASM_OUTPUT_DEF} instead if possible. -@end defmac - -@defmac OBJC_GEN_METHOD_LABEL (@var{buf}, @var{is_inst}, @var{class_name}, @var{cat_name}, @var{sel_name}) -Define this macro to override the default assembler names used for -Objective-C methods. - -The default name is a unique method number followed by the name of the -class (e.g.@: @samp{_1_Foo}). For methods in categories, the name of -the category is also included in the assembler name (e.g.@: -@samp{_1_Foo_Bar}). - -These names are safe on most systems, but make debugging difficult since -the method's selector is not present in the name. Therefore, particular -systems define other ways of computing names. - -@var{buf} is an expression of type @code{char *} which gives you a -buffer in which to store the name; its length is as long as -@var{class_name}, @var{cat_name} and @var{sel_name} put together, plus -50 characters extra. - -The argument @var{is_inst} specifies whether the method is an instance -method or a class method; @var{class_name} is the name of the class; -@var{cat_name} is the name of the category (or @code{NULL} if the method is not -in a category); and @var{sel_name} is the name of the selector. - -On systems where the assembler can handle quoted names, you can use this -macro to provide more human-readable names. -@end defmac - -@node Initialization -@subsection How Initialization Functions Are Handled -@cindex initialization routines -@cindex termination routines -@cindex constructors, output of -@cindex destructors, output of - -The compiled code for certain languages includes @dfn{constructors} -(also called @dfn{initialization routines})---functions to initialize -data in the program when the program is started. These functions need -to be called before the program is ``started''---that is to say, before -@code{main} is called. - -Compiling some languages generates @dfn{destructors} (also called -@dfn{termination routines}) that should be called when the program -terminates. - -To make the initialization and termination functions work, the compiler -must output something in the assembler code to cause those functions to -be called at the appropriate time. When you port the compiler to a new -system, you need to specify how to do this. - -There are two major ways that GCC currently supports the execution of -initialization and termination functions. Each way has two variants. -Much of the structure is common to all four variations. - -@findex __CTOR_LIST__ -@findex __DTOR_LIST__ -The linker must build two lists of these functions---a list of -initialization functions, called @code{__CTOR_LIST__}, and a list of -termination functions, called @code{__DTOR_LIST__}. - -Each list always begins with an ignored function pointer (which may hold -0, @minus{}1, or a count of the function pointers after it, depending on -the environment). This is followed by a series of zero or more function -pointers to constructors (or destructors), followed by a function -pointer containing zero. - -Depending on the operating system and its executable file format, either -@file{crtstuff.c} or @file{libgcc2.c} traverses these lists at startup -time and exit time. Constructors are called in reverse order of the -list; destructors in forward order. - -The best way to handle static constructors works only for object file -formats which provide arbitrarily-named sections. A section is set -aside for a list of constructors, and another for a list of destructors. -Traditionally these are called @samp{.ctors} and @samp{.dtors}. Each -object file that defines an initialization function also puts a word in -the constructor section to point to that function. The linker -accumulates all these words into one contiguous @samp{.ctors} section. -Termination functions are handled similarly. - -This method will be chosen as the default by @file{target-def.h} if -@code{TARGET_ASM_NAMED_SECTION} is defined. A target that does not -support arbitrary sections, but does support special designated -constructor and destructor sections may define @code{CTORS_SECTION_ASM_OP} -and @code{DTORS_SECTION_ASM_OP} to achieve the same effect. - -When arbitrary sections are available, there are two variants, depending -upon how the code in @file{crtstuff.c} is called. On systems that -support a @dfn{.init} section which is executed at program startup, -parts of @file{crtstuff.c} are compiled into that section. The -program is linked by the @command{gcc} driver like this: - -@smallexample -ld -o @var{output_file} crti.o crtbegin.o @dots{} -lgcc crtend.o crtn.o -@end smallexample - -The prologue of a function (@code{__init}) appears in the @code{.init} -section of @file{crti.o}; the epilogue appears in @file{crtn.o}. Likewise -for the function @code{__fini} in the @dfn{.fini} section. Normally these -files are provided by the operating system or by the GNU C library, but -are provided by GCC for a few targets. - -The objects @file{crtbegin.o} and @file{crtend.o} are (for most targets) -compiled from @file{crtstuff.c}. They contain, among other things, code -fragments within the @code{.init} and @code{.fini} sections that branch -to routines in the @code{.text} section. The linker will pull all parts -of a section together, which results in a complete @code{__init} function -that invokes the routines we need at startup. - -To use this variant, you must define the @code{INIT_SECTION_ASM_OP} -macro properly. - -If no init section is available, when GCC compiles any function called -@code{main} (or more accurately, any function designated as a program -entry point by the language front end calling @code{expand_main_function}), -it inserts a procedure call to @code{__main} as the first executable code -after the function prologue. The @code{__main} function is defined -in @file{libgcc2.c} and runs the global constructors. - -In file formats that don't support arbitrary sections, there are again -two variants. In the simplest variant, the GNU linker (GNU @code{ld}) -and an `a.out' format must be used. In this case, -@code{TARGET_ASM_CONSTRUCTOR} is defined to produce a @code{.stabs} -entry of type @samp{N_SETT}, referencing the name @code{__CTOR_LIST__}, -and with the address of the void function containing the initialization -code as its value. The GNU linker recognizes this as a request to add -the value to a @dfn{set}; the values are accumulated, and are eventually -placed in the executable as a vector in the format described above, with -a leading (ignored) count and a trailing zero element. -@code{TARGET_ASM_DESTRUCTOR} is handled similarly. Since no init -section is available, the absence of @code{INIT_SECTION_ASM_OP} causes -the compilation of @code{main} to call @code{__main} as above, starting -the initialization process. - -The last variant uses neither arbitrary sections nor the GNU linker. -This is preferable when you want to do dynamic linking and when using -file formats which the GNU linker does not support, such as `ECOFF'@. In -this case, @code{TARGET_HAVE_CTORS_DTORS} is false, initialization and -termination functions are recognized simply by their names. This requires -an extra program in the linkage step, called @command{collect2}. This program -pretends to be the linker, for use with GCC; it does its job by running -the ordinary linker, but also arranges to include the vectors of -initialization and termination functions. These functions are called -via @code{__main} as described above. In order to use this method, -@code{use_collect2} must be defined in the target in @file{config.gcc}. - -@ifinfo -The following section describes the specific macros that control and -customize the handling of initialization and termination functions. -@end ifinfo - -@node Macros for Initialization -@subsection Macros Controlling Initialization Routines - -Here are the macros that control how the compiler handles initialization -and termination functions: - -@defmac INIT_SECTION_ASM_OP -If defined, a C string constant, including spacing, for the assembler -operation to identify the following data as initialization code. If not -defined, GCC will assume such a section does not exist. When you are -using special sections for initialization and termination functions, this -macro also controls how @file{crtstuff.c} and @file{libgcc2.c} arrange to -run the initialization functions. -@end defmac - -@defmac HAS_INIT_SECTION -If defined, @code{main} will not call @code{__main} as described above. -This macro should be defined for systems that control start-up code -on a symbol-by-symbol basis, such as OSF/1, and should not -be defined explicitly for systems that support @code{INIT_SECTION_ASM_OP}. -@end defmac - -@defmac LD_INIT_SWITCH -If defined, a C string constant for a switch that tells the linker that -the following symbol is an initialization routine. -@end defmac - -@defmac LD_FINI_SWITCH -If defined, a C string constant for a switch that tells the linker that -the following symbol is a finalization routine. -@end defmac - -@defmac COLLECT_SHARED_INIT_FUNC (@var{stream}, @var{func}) -If defined, a C statement that will write a function that can be -automatically called when a shared library is loaded. The function -should call @var{func}, which takes no arguments. If not defined, and -the object format requires an explicit initialization function, then a -function called @code{_GLOBAL__DI} will be generated. - -This function and the following one are used by collect2 when linking a -shared library that needs constructors or destructors, or has DWARF2 -exception tables embedded in the code. -@end defmac - -@defmac COLLECT_SHARED_FINI_FUNC (@var{stream}, @var{func}) -If defined, a C statement that will write a function that can be -automatically called when a shared library is unloaded. The function -should call @var{func}, which takes no arguments. If not defined, and -the object format requires an explicit finalization function, then a -function called @code{_GLOBAL__DD} will be generated. -@end defmac - -@defmac INVOKE__main -If defined, @code{main} will call @code{__main} despite the presence of -@code{INIT_SECTION_ASM_OP}. This macro should be defined for systems -where the init section is not actually run automatically, but is still -useful for collecting the lists of constructors and destructors. -@end defmac - -@defmac SUPPORTS_INIT_PRIORITY -If nonzero, the C++ @code{init_priority} attribute is supported and the -compiler should emit instructions to control the order of initialization -of objects. If zero, the compiler will issue an error message upon -encountering an @code{init_priority} attribute. -@end defmac - -@deftypevr {Target Hook} bool TARGET_HAVE_CTORS_DTORS -This value is true if the target supports some ``native'' method of -collecting constructors and destructors to be run at startup and exit. -It is false if we must use @command{collect2}. -@end deftypevr - -@deftypevr {Target Hook} bool TARGET_DTORS_FROM_CXA_ATEXIT -This value is true if the target wants destructors to be queued to be -run from __cxa_atexit. If this is the case then, for each priority level, -a new constructor will be entered that registers the destructors for that -level with __cxa_atexit (and there will be no destructors emitted). -It is false the method implied by @code{have_ctors_dtors} is used. -@end deftypevr - -@deftypefn {Target Hook} void TARGET_ASM_CONSTRUCTOR (rtx @var{symbol}, int @var{priority}) -If defined, a function that outputs assembler code to arrange to call -the function referenced by @var{symbol} at initialization time. - -Assume that @var{symbol} is a @code{SYMBOL_REF} for a function taking -no arguments and with no return value. If the target supports initialization -priorities, @var{priority} is a value between 0 and @code{MAX_INIT_PRIORITY}; -otherwise it must be @code{DEFAULT_INIT_PRIORITY}. - -If this macro is not defined by the target, a suitable default will -be chosen if (1) the target supports arbitrary section names, (2) the -target defines @code{CTORS_SECTION_ASM_OP}, or (3) @code{USE_COLLECT2} -is not defined. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_DESTRUCTOR (rtx @var{symbol}, int @var{priority}) -This is like @code{TARGET_ASM_CONSTRUCTOR} but used for termination -functions rather than initialization functions. -@end deftypefn - -If @code{TARGET_HAVE_CTORS_DTORS} is true, the initialization routine -generated for the generated object file will have static linkage. - -If your system uses @command{collect2} as the means of processing -constructors, then that program normally uses @command{nm} to scan -an object file for constructor functions to be called. - -On certain kinds of systems, you can define this macro to make -@command{collect2} work faster (and, in some cases, make it work at all): - -@defmac OBJECT_FORMAT_COFF -Define this macro if the system uses COFF (Common Object File Format) -object files, so that @command{collect2} can assume this format and scan -object files directly for dynamic constructor/destructor functions. - -This macro is effective only in a native compiler; @command{collect2} as -part of a cross compiler always uses @command{nm} for the target machine. -@end defmac - -@defmac REAL_NM_FILE_NAME -Define this macro as a C string constant containing the file name to use -to execute @command{nm}. The default is to search the path normally for -@command{nm}. -@end defmac - -@defmac NM_FLAGS -@command{collect2} calls @command{nm} to scan object files for static -constructors and destructors and LTO info. By default, @option{-n} is -passed. Define @code{NM_FLAGS} to a C string constant if other options -are needed to get the same output format as GNU @command{nm -n} -produces. -@end defmac - -If your system supports shared libraries and has a program to list the -dynamic dependencies of a given library or executable, you can define -these macros to enable support for running initialization and -termination functions in shared libraries: - -@defmac LDD_SUFFIX -Define this macro to a C string constant containing the name of the program -which lists dynamic dependencies, like @command{ldd} under SunOS 4. -@end defmac - -@defmac PARSE_LDD_OUTPUT (@var{ptr}) -Define this macro to be C code that extracts filenames from the output -of the program denoted by @code{LDD_SUFFIX}. @var{ptr} is a variable -of type @code{char *} that points to the beginning of a line of output -from @code{LDD_SUFFIX}. If the line lists a dynamic dependency, the -code must advance @var{ptr} to the beginning of the filename on that -line. Otherwise, it must set @var{ptr} to @code{NULL}. -@end defmac - -@defmac SHLIB_SUFFIX -Define this macro to a C string constant containing the default shared -library extension of the target (e.g., @samp{".so"}). @command{collect2} -strips version information after this suffix when generating global -constructor and destructor names. This define is only needed on targets -that use @command{collect2} to process constructors and destructors. -@end defmac - -@node Instruction Output -@subsection Output of Assembler Instructions - -@c prevent bad page break with this line -This describes assembler instruction output. - -@defmac REGISTER_NAMES -A C initializer containing the assembler's names for the machine -registers, each one as a C string constant. This is what translates -register numbers in the compiler into assembler language. -@end defmac - -@defmac ADDITIONAL_REGISTER_NAMES -If defined, a C initializer for an array of structures containing a name -and a register number. This macro defines additional names for hard -registers, thus allowing the @code{asm} option in declarations to refer -to registers using alternate names. -@end defmac - -@defmac OVERLAPPING_REGISTER_NAMES -If defined, a C initializer for an array of structures containing a -name, a register number and a count of the number of consecutive -machine registers the name overlaps. This macro defines additional -names for hard registers, thus allowing the @code{asm} option in -declarations to refer to registers using alternate names. Unlike -@code{ADDITIONAL_REGISTER_NAMES}, this macro should be used when the -register name implies multiple underlying registers. - -This macro should be used when it is important that a clobber in an -@code{asm} statement clobbers all the underlying values implied by the -register name. For example, on ARM, clobbering the double-precision -VFP register ``d0'' implies clobbering both single-precision registers -``s0'' and ``s1''. -@end defmac - -@defmac ASM_OUTPUT_OPCODE (@var{stream}, @var{ptr}) -Define this macro if you are using an unusual assembler that -requires different names for the machine instructions. - -The definition is a C statement or statements which output an -assembler instruction opcode to the stdio stream @var{stream}. The -macro-operand @var{ptr} is a variable of type @code{char *} which -points to the opcode name in its ``internal'' form---the form that is -written in the machine description. The definition should output the -opcode name to @var{stream}, performing any translation you desire, and -increment the variable @var{ptr} to point at the end of the opcode -so that it will not be output twice. - -In fact, your macro definition may process less than the entire opcode -name, or more than the opcode name; but if you want to process text -that includes @samp{%}-sequences to substitute operands, you must take -care of the substitution yourself. Just be sure to increment -@var{ptr} over whatever text should not be output normally. - -@findex recog_data.operand -If you need to look at the operand values, they can be found as the -elements of @code{recog_data.operand}. - -If the macro definition does nothing, the instruction is output -in the usual way. -@end defmac - -@defmac FINAL_PRESCAN_INSN (@var{insn}, @var{opvec}, @var{noperands}) -If defined, a C statement to be executed just prior to the output of -assembler code for @var{insn}, to modify the extracted operands so -they will be output differently. - -Here the argument @var{opvec} is the vector containing the operands -extracted from @var{insn}, and @var{noperands} is the number of -elements of the vector which contain meaningful data for this insn. -The contents of this vector are what will be used to convert the insn -template into assembler code, so you can change the assembler output -by changing the contents of the vector. - -This macro is useful when various assembler syntaxes share a single -file of instruction patterns; by defining this macro differently, you -can cause a large class of instructions to be output differently (such -as with rearranged operands). Naturally, variations in assembler -syntax affecting individual insn patterns ought to be handled by -writing conditional output routines in those patterns. - -If this macro is not defined, it is equivalent to a null statement. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_FINAL_POSTSCAN_INSN (FILE *@var{file}, rtx_insn *@var{insn}, rtx *@var{opvec}, int @var{noperands}) -If defined, this target hook is a function which is executed just after the -output of assembler code for @var{insn}, to change the mode of the assembler -if necessary. - -Here the argument @var{opvec} is the vector containing the operands -extracted from @var{insn}, and @var{noperands} is the number of -elements of the vector which contain meaningful data for this insn. -The contents of this vector are what was used to convert the insn -template into assembler code, so you can change the assembler mode -by checking the contents of the vector. -@end deftypefn - -@defmac PRINT_OPERAND (@var{stream}, @var{x}, @var{code}) -A C compound statement to output to stdio stream @var{stream} the -assembler syntax for an instruction operand @var{x}. @var{x} is an -RTL expression. - -@var{code} is a value that can be used to specify one of several ways -of printing the operand. It is used when identical operands must be -printed differently depending on the context. @var{code} comes from -the @samp{%} specification that was used to request printing of the -operand. If the specification was just @samp{%@var{digit}} then -@var{code} is 0; if the specification was @samp{%@var{ltr} -@var{digit}} then @var{code} is the ASCII code for @var{ltr}. - -@findex reg_names -If @var{x} is a register, this macro should print the register's name. -The names can be found in an array @code{reg_names} whose type is -@code{char *[]}. @code{reg_names} is initialized from -@code{REGISTER_NAMES}. - -When the machine description has a specification @samp{%@var{punct}} -(a @samp{%} followed by a punctuation character), this macro is called -with a null pointer for @var{x} and the punctuation character for -@var{code}. -@end defmac - -@defmac PRINT_OPERAND_PUNCT_VALID_P (@var{code}) -A C expression which evaluates to true if @var{code} is a valid -punctuation character for use in the @code{PRINT_OPERAND} macro. If -@code{PRINT_OPERAND_PUNCT_VALID_P} is not defined, it means that no -punctuation characters (except for the standard one, @samp{%}) are used -in this way. -@end defmac - -@defmac PRINT_OPERAND_ADDRESS (@var{stream}, @var{x}) -A C compound statement to output to stdio stream @var{stream} the -assembler syntax for an instruction operand that is a memory reference -whose address is @var{x}. @var{x} is an RTL expression. - -@cindex @code{TARGET_ENCODE_SECTION_INFO} usage -On some machines, the syntax for a symbolic address depends on the -section that the address refers to. On these machines, define the hook -@code{TARGET_ENCODE_SECTION_INFO} to store the information into the -@code{symbol_ref}, and then check for it here. @xref{Assembler -Format}. -@end defmac - -@findex dbr_sequence_length -@defmac DBR_OUTPUT_SEQEND (@var{file}) -A C statement, to be executed after all slot-filler instructions have -been output. If necessary, call @code{dbr_sequence_length} to -determine the number of slots filled in a sequence (zero if not -currently outputting a sequence), to decide how many no-ops to output, -or whatever. - -Don't define this macro if it has nothing to do, but it is helpful in -reading assembly output if the extent of the delay sequence is made -explicit (e.g.@: with white space). -@end defmac - -@findex final_sequence -Note that output routines for instructions with delay slots must be -prepared to deal with not being output as part of a sequence -(i.e.@: when the scheduling pass is not run, or when no slot fillers could be -found.) The variable @code{final_sequence} is null when not -processing a sequence, otherwise it contains the @code{sequence} rtx -being output. - -@findex asm_fprintf -@defmac REGISTER_PREFIX -@defmacx LOCAL_LABEL_PREFIX -@defmacx USER_LABEL_PREFIX -@defmacx IMMEDIATE_PREFIX -If defined, C string expressions to be used for the @samp{%R}, @samp{%L}, -@samp{%U}, and @samp{%I} options of @code{asm_fprintf} (see -@file{final.cc}). These are useful when a single @file{md} file must -support multiple assembler formats. In that case, the various @file{tm.h} -files can define these macros differently. -@end defmac - -@defmac ASM_FPRINTF_EXTENSIONS (@var{file}, @var{argptr}, @var{format}) -If defined this macro should expand to a series of @code{case} -statements which will be parsed inside the @code{switch} statement of -the @code{asm_fprintf} function. This allows targets to define extra -printf formats which may useful when generating their assembler -statements. Note that uppercase letters are reserved for future -generic extensions to asm_fprintf, and so are not available to target -specific code. The output file is given by the parameter @var{file}. -The varargs input pointer is @var{argptr} and the rest of the format -string, starting the character after the one that is being switched -upon, is pointed to by @var{format}. -@end defmac - -@defmac ASSEMBLER_DIALECT -If your target supports multiple dialects of assembler language (such as -different opcodes), define this macro as a C expression that gives the -numeric index of the assembler language dialect to use, with zero as the -first variant. - -If this macro is defined, you may use constructs of the form -@smallexample -@samp{@{option0|option1|option2@dots{}@}} -@end smallexample -@noindent -in the output templates of patterns (@pxref{Output Template}) or in the -first argument of @code{asm_fprintf}. This construct outputs -@samp{option0}, @samp{option1}, @samp{option2}, etc., if the value of -@code{ASSEMBLER_DIALECT} is zero, one, two, etc. Any special characters -within these strings retain their usual meaning. If there are fewer -alternatives within the braces than the value of -@code{ASSEMBLER_DIALECT}, the construct outputs nothing. If it's needed -to print curly braces or @samp{|} character in assembler output directly, -@samp{%@{}, @samp{%@}} and @samp{%|} can be used. - -If you do not define this macro, the characters @samp{@{}, @samp{|} and -@samp{@}} do not have any special meaning when used in templates or -operands to @code{asm_fprintf}. - -Define the macros @code{REGISTER_PREFIX}, @code{LOCAL_LABEL_PREFIX}, -@code{USER_LABEL_PREFIX} and @code{IMMEDIATE_PREFIX} if you can express -the variations in assembler language syntax with that mechanism. Define -@code{ASSEMBLER_DIALECT} and use the @samp{@{option0|option1@}} syntax -if the syntax variant are larger and involve such things as different -opcodes or operand order. -@end defmac - -@defmac ASM_OUTPUT_REG_PUSH (@var{stream}, @var{regno}) -A C expression to output to @var{stream} some assembler code -which will push hard register number @var{regno} onto the stack. -The code need not be optimal, since this macro is used only when -profiling. -@end defmac - -@defmac ASM_OUTPUT_REG_POP (@var{stream}, @var{regno}) -A C expression to output to @var{stream} some assembler code -which will pop hard register number @var{regno} off of the stack. -The code need not be optimal, since this macro is used only when -profiling. -@end defmac - -@node Dispatch Tables -@subsection Output of Dispatch Tables - -@c prevent bad page break with this line -This concerns dispatch tables. - -@cindex dispatch table -@defmac ASM_OUTPUT_ADDR_DIFF_ELT (@var{stream}, @var{body}, @var{value}, @var{rel}) -A C statement to output to the stdio stream @var{stream} an assembler -pseudo-instruction to generate a difference between two labels. -@var{value} and @var{rel} are the numbers of two internal labels. The -definitions of these labels are output using -@code{(*targetm.asm_out.internal_label)}, and they must be printed in the same -way here. For example, - -@smallexample -fprintf (@var{stream}, "\t.word L%d-L%d\n", - @var{value}, @var{rel}) -@end smallexample - -You must provide this macro on machines where the addresses in a -dispatch table are relative to the table's own address. If defined, GCC -will also use this macro on all machines when producing PIC@. -@var{body} is the body of the @code{ADDR_DIFF_VEC}; it is provided so that the -mode and flags can be read. -@end defmac - -@defmac ASM_OUTPUT_ADDR_VEC_ELT (@var{stream}, @var{value}) -This macro should be provided on machines where the addresses -in a dispatch table are absolute. - -The definition should be a C statement to output to the stdio stream -@var{stream} an assembler pseudo-instruction to generate a reference to -a label. @var{value} is the number of an internal label whose -definition is output using @code{(*targetm.asm_out.internal_label)}. -For example, - -@smallexample -fprintf (@var{stream}, "\t.word L%d\n", @var{value}) -@end smallexample -@end defmac - -@defmac ASM_OUTPUT_CASE_LABEL (@var{stream}, @var{prefix}, @var{num}, @var{table}) -Define this if the label before a jump-table needs to be output -specially. The first three arguments are the same as for -@code{(*targetm.asm_out.internal_label)}; the fourth argument is the -jump-table which follows (a @code{jump_table_data} containing an -@code{addr_vec} or @code{addr_diff_vec}). - -This feature is used on system V to output a @code{swbeg} statement -for the table. - -If this macro is not defined, these labels are output with -@code{(*targetm.asm_out.internal_label)}. -@end defmac - -@defmac ASM_OUTPUT_CASE_END (@var{stream}, @var{num}, @var{table}) -Define this if something special must be output at the end of a -jump-table. The definition should be a C statement to be executed -after the assembler code for the table is written. It should write -the appropriate code to stdio stream @var{stream}. The argument -@var{table} is the jump-table insn, and @var{num} is the label-number -of the preceding label. - -If this macro is not defined, nothing special is output at the end of -the jump-table. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_POST_CFI_STARTPROC (FILE *@var{}, @var{tree}) -This target hook is used to emit assembly strings required by the target -after the .cfi_startproc directive. The first argument is the file stream to -write the strings to and the second argument is the function's declaration. The -expected use is to add more .cfi_* directives. - -The default is to not output any assembly strings. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_EMIT_UNWIND_LABEL (FILE *@var{stream}, tree @var{decl}, int @var{for_eh}, int @var{empty}) -This target hook emits a label at the beginning of each FDE@. It -should be defined on targets where FDEs need special labels, and it -should write the appropriate label, for the FDE associated with the -function declaration @var{decl}, to the stdio stream @var{stream}. -The third argument, @var{for_eh}, is a boolean: true if this is for an -exception table. The fourth argument, @var{empty}, is a boolean: -true if this is a placeholder label for an omitted FDE@. - -The default is that FDEs are not given nonlocal labels. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_EMIT_EXCEPT_TABLE_LABEL (FILE *@var{stream}) -This target hook emits a label at the beginning of the exception table. -It should be defined on targets where it is desirable for the table -to be broken up according to function. - -The default is that no label is emitted. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_EMIT_EXCEPT_PERSONALITY (rtx @var{personality}) -If the target implements @code{TARGET_ASM_UNWIND_EMIT}, this hook may be -used to emit a directive to install a personality hook into the unwind -info. This hook should not be used if dwarf2 unwind info is used. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_UNWIND_EMIT (FILE *@var{stream}, rtx_insn *@var{insn}) -This target hook emits assembly directives required to unwind the -given instruction. This is only used when @code{TARGET_EXCEPT_UNWIND_INFO} -returns @code{UI_TARGET}. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_ASM_MAKE_EH_SYMBOL_INDIRECT (rtx @var{origsymbol}, bool @var{pubvis}) -If necessary, modify personality and LSDA references to handle indirection. -The original symbol is in @code{origsymbol} and if @code{pubvis} is true -the symbol is visible outside the TU. -@end deftypefn - -@deftypevr {Target Hook} bool TARGET_ASM_UNWIND_EMIT_BEFORE_INSN -True if the @code{TARGET_ASM_UNWIND_EMIT} hook should be called before -the assembly for @var{insn} has been emitted, false if the hook should -be called afterward. -@end deftypevr - -@deftypefn {Target Hook} bool TARGET_ASM_SHOULD_RESTORE_CFA_STATE (void) -For DWARF-based unwind frames, two CFI instructions provide for save and -restore of register state. GCC maintains the current frame address (CFA) -separately from the register bank but the unwinder in libgcc preserves this -state along with the registers (and this is expected by the code that writes -the unwind frames). This hook allows the target to specify that the CFA data -is not saved/restored along with the registers by the target unwinder so that -suitable additional instructions should be emitted to restore it. -@end deftypefn - -@node Exception Region Output -@subsection Assembler Commands for Exception Regions - -@c prevent bad page break with this line - -This describes commands marking the start and the end of an exception -region. - -@defmac EH_FRAME_SECTION_NAME -If defined, a C string constant for the name of the section containing -exception handling frame unwind information. If not defined, GCC will -provide a default definition if the target supports named sections. -@file{crtstuff.c} uses this macro to switch to the appropriate section. - -You should define this symbol if your target supports DWARF 2 frame -unwind information and the default definition does not work. -@end defmac - -@defmac EH_FRAME_THROUGH_COLLECT2 -If defined, DWARF 2 frame unwind information will identified by -specially named labels. The collect2 process will locate these -labels and generate code to register the frames. - -This might be necessary, for instance, if the system linker will not -place the eh_frames in-between the sentinals from @file{crtstuff.c}, -or if the system linker does garbage collection and sections cannot -be marked as not to be collected. -@end defmac - -@defmac EH_TABLES_CAN_BE_READ_ONLY -Define this macro to 1 if your target is such that no frame unwind -information encoding used with non-PIC code will ever require a -runtime relocation, but the linker may not support merging read-only -and read-write sections into a single read-write section. -@end defmac - -@defmac MASK_RETURN_ADDR -An rtx used to mask the return address found via @code{RETURN_ADDR_RTX}, so -that it does not contain any extraneous set bits in it. -@end defmac - -@defmac DWARF2_UNWIND_INFO -Define this macro to 0 if your target supports DWARF 2 frame unwind -information, but it does not yet work with exception handling. -Otherwise, if your target supports this information (if it defines -@code{INCOMING_RETURN_ADDR_RTX} and @code{OBJECT_FORMAT_ELF}), -GCC will provide a default definition of 1. -@end defmac - -@deftypefn {Common Target Hook} {enum unwind_info_type} TARGET_EXCEPT_UNWIND_INFO (struct gcc_options *@var{opts}) -This hook defines the mechanism that will be used for exception handling -by the target. If the target has ABI specified unwind tables, the hook -should return @code{UI_TARGET}. If the target is to use the -@code{setjmp}/@code{longjmp}-based exception handling scheme, the hook -should return @code{UI_SJLJ}. If the target supports DWARF 2 frame unwind -information, the hook should return @code{UI_DWARF2}. - -A target may, if exceptions are disabled, choose to return @code{UI_NONE}. -This may end up simplifying other parts of target-specific code. The -default implementation of this hook never returns @code{UI_NONE}. - -Note that the value returned by this hook should be constant. It should -not depend on anything except the command-line switches described by -@var{opts}. In particular, the -setting @code{UI_SJLJ} must be fixed at compiler start-up as C pre-processor -macros and builtin functions related to exception handling are set up -depending on this setting. - -The default implementation of the hook first honors the -@option{--enable-sjlj-exceptions} configure option, then -@code{DWARF2_UNWIND_INFO}, and finally defaults to @code{UI_SJLJ}. If -@code{DWARF2_UNWIND_INFO} depends on command-line options, the target -must define this hook so that @var{opts} is used correctly. -@end deftypefn - -@deftypevr {Common Target Hook} bool TARGET_UNWIND_TABLES_DEFAULT -This variable should be set to @code{true} if the target ABI requires unwinding -tables even when exceptions are not used. It must not be modified by -command-line option processing. -@end deftypevr - -@defmac DONT_USE_BUILTIN_SETJMP -Define this macro to 1 if the @code{setjmp}/@code{longjmp}-based scheme -should use the @code{setjmp}/@code{longjmp} functions from the C library -instead of the @code{__builtin_setjmp}/@code{__builtin_longjmp} machinery. -@end defmac - -@defmac JMP_BUF_SIZE -This macro has no effect unless @code{DONT_USE_BUILTIN_SETJMP} is also -defined. Define this macro if the default size of @code{jmp_buf} buffer -for the @code{setjmp}/@code{longjmp}-based exception handling mechanism -is not large enough, or if it is much too large. -The default size is @code{FIRST_PSEUDO_REGISTER * sizeof(void *)}. -@end defmac - -@defmac DWARF_CIE_DATA_ALIGNMENT -This macro need only be defined if the target might save registers in the -function prologue at an offset to the stack pointer that is not aligned to -@code{UNITS_PER_WORD}. The definition should be the negative minimum -alignment if @code{STACK_GROWS_DOWNWARD} is true, and the positive -minimum alignment otherwise. @xref{DWARF}. Only applicable if -the target supports DWARF 2 frame unwind information. -@end defmac - -@deftypevr {Target Hook} bool TARGET_TERMINATE_DW2_EH_FRAME_INFO -Contains the value true if the target should add a zero word onto the -end of a Dwarf-2 frame info section when used for exception handling. -Default value is false if @code{EH_FRAME_SECTION_NAME} is defined, and -true otherwise. -@end deftypevr - -@deftypefn {Target Hook} rtx TARGET_DWARF_REGISTER_SPAN (rtx @var{reg}) -Given a register, this hook should return a parallel of registers to -represent where to find the register pieces. Define this hook if the -register and its mode are represented in Dwarf in non-contiguous -locations, or if the register should be represented in more than one -register in Dwarf. Otherwise, this hook should return @code{NULL_RTX}. -If not defined, the default is to return @code{NULL_RTX}. -@end deftypefn - -@deftypefn {Target Hook} machine_mode TARGET_DWARF_FRAME_REG_MODE (int @var{regno}) -Given a register, this hook should return the mode which the -corresponding Dwarf frame register should have. This is normally -used to return a smaller mode than the raw mode to prevent call -clobbered parts of a register altering the frame register size -@end deftypefn - -@deftypefn {Target Hook} void TARGET_INIT_DWARF_REG_SIZES_EXTRA (tree @var{address}) -If some registers are represented in Dwarf-2 unwind information in -multiple pieces, define this hook to fill in information about the -sizes of those pieces in the table used by the unwinder at runtime. -It will be called by @code{expand_builtin_init_dwarf_reg_sizes} after -filling in a single size corresponding to each hard register; -@var{address} is the address of the table. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ASM_TTYPE (rtx @var{sym}) -This hook is used to output a reference from a frame unwinding table to -the type_info object identified by @var{sym}. It should return @code{true} -if the reference was output. Returning @code{false} will cause the -reference to be output using the normal Dwarf2 routines. -@end deftypefn - -@deftypevr {Target Hook} bool TARGET_ARM_EABI_UNWINDER -This flag should be set to @code{true} on targets that use an ARM EABI -based unwinding library, and @code{false} on other targets. This effects -the format of unwinding tables, and how the unwinder in entered after -running a cleanup. The default is @code{false}. -@end deftypevr - -@node Alignment Output -@subsection Assembler Commands for Alignment - -@c prevent bad page break with this line -This describes commands for alignment. - -@defmac JUMP_ALIGN (@var{label}) -The alignment (log base 2) to put in front of @var{label}, which is -a common destination of jumps and has no fallthru incoming edge. - -This macro need not be defined if you don't want any special alignment -to be done at such a time. Most machine descriptions do not currently -define the macro. - -Unless it's necessary to inspect the @var{label} parameter, it is better -to set the variable @var{align_jumps} in the target's -@code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's -selection in @var{align_jumps} in a @code{JUMP_ALIGN} implementation. -@end defmac - -@defmac LABEL_ALIGN_AFTER_BARRIER (@var{label}) -The alignment (log base 2) to put in front of @var{label}, which follows -a @code{BARRIER}. - -This macro need not be defined if you don't want any special alignment -to be done at such a time. Most machine descriptions do not currently -define the macro. -@end defmac - -@defmac LOOP_ALIGN (@var{label}) -The alignment (log base 2) to put in front of @var{label} that heads -a frequently executed basic block (usually the header of a loop). - -This macro need not be defined if you don't want any special alignment -to be done at such a time. Most machine descriptions do not currently -define the macro. - -Unless it's necessary to inspect the @var{label} parameter, it is better -to set the variable @code{align_loops} in the target's -@code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's -selection in @code{align_loops} in a @code{LOOP_ALIGN} implementation. -@end defmac - -@defmac LABEL_ALIGN (@var{label}) -The alignment (log base 2) to put in front of @var{label}. -If @code{LABEL_ALIGN_AFTER_BARRIER} / @code{LOOP_ALIGN} specify a different alignment, -the maximum of the specified values is used. - -Unless it's necessary to inspect the @var{label} parameter, it is better -to set the variable @code{align_labels} in the target's -@code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's -selection in @code{align_labels} in a @code{LABEL_ALIGN} implementation. -@end defmac - -@defmac ASM_OUTPUT_SKIP (@var{stream}, @var{nbytes}) -A C statement to output to the stdio stream @var{stream} an assembler -instruction to advance the location counter by @var{nbytes} bytes. -Those bytes should be zero when loaded. @var{nbytes} will be a C -expression of type @code{unsigned HOST_WIDE_INT}. -@end defmac - -@defmac ASM_NO_SKIP_IN_TEXT -Define this macro if @code{ASM_OUTPUT_SKIP} should not be used in the -text section because it fails to put zeros in the bytes that are skipped. -This is true on many Unix systems, where the pseudo--op to skip bytes -produces no-op instructions rather than zeros when used in the text -section. -@end defmac - -@defmac ASM_OUTPUT_ALIGN (@var{stream}, @var{power}) -A C statement to output to the stdio stream @var{stream} an assembler -command to advance the location counter to a multiple of 2 to the -@var{power} bytes. @var{power} will be a C expression of type @code{int}. -@end defmac - -@defmac ASM_OUTPUT_ALIGN_WITH_NOP (@var{stream}, @var{power}) -Like @code{ASM_OUTPUT_ALIGN}, except that the ``nop'' instruction is used -for padding, if necessary. -@end defmac - -@defmac ASM_OUTPUT_MAX_SKIP_ALIGN (@var{stream}, @var{power}, @var{max_skip}) -A C statement to output to the stdio stream @var{stream} an assembler -command to advance the location counter to a multiple of 2 to the -@var{power} bytes, but only if @var{max_skip} or fewer bytes are needed to -satisfy the alignment request. @var{power} and @var{max_skip} will be -a C expression of type @code{int}. -@end defmac - -@need 3000 -@node Debugging Info -@section Controlling Debugging Information Format - -@c prevent bad page break with this line -This describes how to specify debugging information. - -@menu -* All Debuggers:: Macros that affect all debugging formats uniformly. -* DWARF:: Macros for DWARF format. -* VMS Debug:: Macros for VMS debug format. -* CTF Debug:: Macros for CTF debug format. -* BTF Debug:: Macros for BTF debug format. -@end menu - -@node All Debuggers -@subsection Macros Affecting All Debugging Formats - -@c prevent bad page break with this line -These macros affect all debugging formats. - -@defmac DEBUGGER_REGNO (@var{regno}) -A C expression that returns the debugger register number for the compiler -register number @var{regno}. In the default macro provided, the value -of this expression will be @var{regno} itself. But sometimes there are -some registers that the compiler knows about and debugger does not, or vice -versa. In such cases, some register may need to have one number in the -compiler and another for debugger@. - -If two registers have consecutive numbers inside GCC, and they can be -used as a pair to hold a multiword value, then they @emph{must} have -consecutive numbers after renumbering with @code{DEBUGGER_REGNO}. -Otherwise, debuggers will be unable to access such a pair, because they -expect register pairs to be consecutive in their own numbering scheme. - -If you find yourself defining @code{DEBUGGER_REGNO} in way that -does not preserve register pairs, then what you must do instead is -redefine the actual register numbering scheme. -@end defmac - -@defmac DEBUGGER_AUTO_OFFSET (@var{x}) -A C expression that returns the integer offset value for an automatic -variable having address @var{x} (an RTL expression). The default -computation assumes that @var{x} is based on the frame-pointer and -gives the offset from the frame-pointer. This is required for targets -that produce debugging output for debugger and allow the frame-pointer to be -eliminated when the @option{-g} option is used. -@end defmac - -@defmac DEBUGGER_ARG_OFFSET (@var{offset}, @var{x}) -A C expression that returns the integer offset value for an argument -having address @var{x} (an RTL expression). The nominal offset is -@var{offset}. -@end defmac - -@defmac PREFERRED_DEBUGGING_TYPE -A C expression that returns the type of debugging output GCC should -produce when the user specifies just @option{-g}. Define -this if you have arranged for GCC to support more than one format of -debugging output. Currently, the allowable values are -@code{DWARF2_DEBUG}, @code{VMS_DEBUG}, -and @code{VMS_AND_DWARF2_DEBUG}. - -When the user specifies @option{-ggdb}, GCC normally also uses the -value of this macro to select the debugging output format, but with two -exceptions. If @code{DWARF2_DEBUGGING_INFO} is defined, GCC uses the -value @code{DWARF2_DEBUG}. - -The value of this macro only affects the default debugging output; the -user can always get a specific type of output by using @option{-gdwarf-2}, -or @option{-gvms}. -@end defmac - -@defmac DEFAULT_GDB_EXTENSIONS -Define this macro to control whether GCC should by default generate -GDB's extended version of debugging information. If you don't define the -macro, the default is 1: always generate the extended information -if there is any occasion to. -@end defmac - -@need 2000 -@node DWARF -@subsection Macros for DWARF Output - -@c prevent bad page break with this line -Here are macros for DWARF output. - -@defmac DWARF2_DEBUGGING_INFO -Define this macro if GCC should produce dwarf version 2 format -debugging output in response to the @option{-g} option. - -To support optional call frame debugging information, you must also -define @code{INCOMING_RETURN_ADDR_RTX} and either set -@code{RTX_FRAME_RELATED_P} on the prologue insns if you use RTL for the -prologue, or call @code{dwarf2out_def_cfa} and @code{dwarf2out_reg_save} -as appropriate from @code{TARGET_ASM_FUNCTION_PROLOGUE} if you don't. -@end defmac - -@deftypefn {Target Hook} int TARGET_DWARF_CALLING_CONVENTION (const_tree @var{function}) -Define this to enable the dwarf attribute @code{DW_AT_calling_convention} to -be emitted for each function. Instead of an integer return the enum -value for the @code{DW_CC_} tag. -@end deftypefn - -@defmac DWARF2_FRAME_INFO -Define this macro to a nonzero value if GCC should always output -Dwarf 2 frame information. If @code{TARGET_EXCEPT_UNWIND_INFO} -(@pxref{Exception Region Output}) returns @code{UI_DWARF2}, and -exceptions are enabled, GCC will output this information not matter -how you define @code{DWARF2_FRAME_INFO}. -@end defmac - -@deftypefn {Target Hook} {enum unwind_info_type} TARGET_DEBUG_UNWIND_INFO (void) -This hook defines the mechanism that will be used for describing frame -unwind information to the debugger. Normally the hook will return -@code{UI_DWARF2} if DWARF 2 debug information is enabled, and -return @code{UI_NONE} otherwise. - -A target may return @code{UI_DWARF2} even when DWARF 2 debug information -is disabled in order to always output DWARF 2 frame information. - -A target may return @code{UI_TARGET} if it has ABI specified unwind tables. -This will suppress generation of the normal debug frame unwind information. -@end deftypefn - -@defmac DWARF2_ASM_LINE_DEBUG_INFO -Define this macro to be a nonzero value if the assembler can generate Dwarf 2 -line debug info sections. This will result in much more compact line number -tables, and hence is desirable if it works. -@end defmac - -@defmac DWARF2_ASM_VIEW_DEBUG_INFO -Define this macro to be a nonzero value if the assembler supports view -assignment and verification in @code{.loc}. If it does not, but the -user enables location views, the compiler may have to fallback to -internal line number tables. -@end defmac - -@deftypefn {Target Hook} int TARGET_RESET_LOCATION_VIEW (rtx_insn *@var{}) -This hook, if defined, enables -ginternal-reset-location-views, and -uses its result to override cases in which the estimated min insn -length might be nonzero even when a PC advance (i.e., a view reset) -cannot be taken for granted. - -If the hook is defined, it must return a positive value to indicate -the insn definitely advances the PC, and so the view number can be -safely assumed to be reset; a negative value to mean the insn -definitely does not advance the PC, and os the view number must not -be reset; or zero to decide based on the estimated insn length. - -If insn length is to be regarded as reliable, set the hook to -@code{hook_int_rtx_insn_0}. -@end deftypefn - -@deftypevr {Target Hook} bool TARGET_WANT_DEBUG_PUB_SECTIONS -True if the @code{.debug_pubtypes} and @code{.debug_pubnames} sections -should be emitted. These sections are not used on most platforms, and -in particular GDB does not use them. -@end deftypevr - -@deftypevr {Target Hook} bool TARGET_DELAY_SCHED2 -True if sched2 is not to be run at its normal place. -This usually means it will be run as part of machine-specific reorg. -@end deftypevr - -@deftypevr {Target Hook} bool TARGET_DELAY_VARTRACK -True if vartrack is not to be run at its normal place. -This usually means it will be run as part of machine-specific reorg. -@end deftypevr - -@deftypevr {Target Hook} bool TARGET_NO_REGISTER_ALLOCATION -True if register allocation and the passes -following it should not be run. Usually true only for virtual assembler -targets. -@end deftypevr - -@defmac ASM_OUTPUT_DWARF_DELTA (@var{stream}, @var{size}, @var{label1}, @var{label2}) -A C statement to issue assembly directives that create a difference -@var{lab1} minus @var{lab2}, using an integer of the given @var{size}. -@end defmac - -@defmac ASM_OUTPUT_DWARF_VMS_DELTA (@var{stream}, @var{size}, @var{label1}, @var{label2}) -A C statement to issue assembly directives that create a difference -between the two given labels in system defined units, e.g.@: instruction -slots on IA64 VMS, using an integer of the given size. -@end defmac - -@defmac ASM_OUTPUT_DWARF_OFFSET (@var{stream}, @var{size}, @var{label}, @var{offset}, @var{section}) -A C statement to issue assembly directives that create a -section-relative reference to the given @var{label} plus @var{offset}, using -an integer of the given @var{size}. The label is known to be defined in the -given @var{section}. -@end defmac - -@defmac ASM_OUTPUT_DWARF_PCREL (@var{stream}, @var{size}, @var{label}) -A C statement to issue assembly directives that create a self-relative -reference to the given @var{label}, using an integer of the given @var{size}. -@end defmac - -@defmac ASM_OUTPUT_DWARF_DATAREL (@var{stream}, @var{size}, @var{label}) -A C statement to issue assembly directives that create a reference to the -given @var{label} relative to the dbase, using an integer of the given @var{size}. -@end defmac - -@defmac ASM_OUTPUT_DWARF_TABLE_REF (@var{label}) -A C statement to issue assembly directives that create a reference to -the DWARF table identifier @var{label} from the current section. This -is used on some systems to avoid garbage collecting a DWARF table which -is referenced by a function. -@end defmac - -@deftypefn {Target Hook} void TARGET_ASM_OUTPUT_DWARF_DTPREL (FILE *@var{file}, int @var{size}, rtx @var{x}) -If defined, this target hook is a function which outputs a DTP-relative -reference to the given TLS symbol of the specified size. -@end deftypefn - -@need 2000 -@node VMS Debug -@subsection Macros for VMS Debug Format - -@c prevent bad page break with this line -Here are macros for VMS debug format. - -@defmac VMS_DEBUGGING_INFO -Define this macro if GCC should produce debugging output for VMS -in response to the @option{-g} option. The default behavior for VMS -is to generate minimal debug info for a traceback in the absence of -@option{-g} unless explicitly overridden with @option{-g0}. This -behavior is controlled by @code{TARGET_OPTION_OPTIMIZATION} and -@code{TARGET_OPTION_OVERRIDE}. -@end defmac - -@need 2000 -@node CTF Debug -@subsection Macros for CTF Debug Format - -@c prevent bad page break with this line -Here are macros for CTF debug format. - -@defmac CTF_DEBUGGING_INFO -Define this macro if GCC should produce debugging output in CTF debug -format in response to the @option{-gctf} option. -@end defmac - -@need 2000 -@node BTF Debug -@subsection Macros for BTF Debug Format - -@c prevent bad page break with this line -Here are macros for BTF debug format. - -@defmac BTF_DEBUGGING_INFO -Define this macro if GCC should produce debugging output in BTF debug -format in response to the @option{-gbtf} option. -@end defmac - -@node Floating Point -@section Cross Compilation and Floating Point -@cindex cross compilation and floating point -@cindex floating point and cross compilation - -While all modern machines use twos-complement representation for integers, -there are a variety of representations for floating point numbers. This -means that in a cross-compiler the representation of floating point numbers -in the compiled program may be different from that used in the machine -doing the compilation. - -Because different representation systems may offer different amounts of -range and precision, all floating point constants must be represented in -the target machine's format. Therefore, the cross compiler cannot -safely use the host machine's floating point arithmetic; it must emulate -the target's arithmetic. To ensure consistency, GCC always uses -emulation to work with floating point values, even when the host and -target floating point formats are identical. - -The following macros are provided by @file{real.h} for the compiler to -use. All parts of the compiler which generate or optimize -floating-point calculations must use these macros. They may evaluate -their operands more than once, so operands must not have side effects. - -@defmac REAL_VALUE_TYPE -The C data type to be used to hold a floating point value in the target -machine's format. Typically this is a @code{struct} containing an -array of @code{HOST_WIDE_INT}, but all code should treat it as an opaque -quantity. -@end defmac - -@deftypefn Macro HOST_WIDE_INT REAL_VALUE_FIX (REAL_VALUE_TYPE @var{x}) -Truncates @var{x} to a signed integer, rounding toward zero. -@end deftypefn - -@deftypefn Macro {unsigned HOST_WIDE_INT} REAL_VALUE_UNSIGNED_FIX (REAL_VALUE_TYPE @var{x}) -Truncates @var{x} to an unsigned integer, rounding toward zero. If -@var{x} is negative, returns zero. -@end deftypefn - -@deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_ATOF (const char *@var{string}, machine_mode @var{mode}) -Converts @var{string} into a floating point number in the target machine's -representation for mode @var{mode}. This routine can handle both -decimal and hexadecimal floating point constants, using the syntax -defined by the C language for both. -@end deftypefn - -@deftypefn Macro int REAL_VALUE_NEGATIVE (REAL_VALUE_TYPE @var{x}) -Returns 1 if @var{x} is negative (including negative zero), 0 otherwise. -@end deftypefn - -@deftypefn Macro int REAL_VALUE_ISINF (REAL_VALUE_TYPE @var{x}) -Determines whether @var{x} represents infinity (positive or negative). -@end deftypefn - -@deftypefn Macro int REAL_VALUE_ISNAN (REAL_VALUE_TYPE @var{x}) -Determines whether @var{x} represents a ``NaN'' (not-a-number). -@end deftypefn - -@deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_NEGATE (REAL_VALUE_TYPE @var{x}) -Returns the negative of the floating point value @var{x}. -@end deftypefn - -@deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_ABS (REAL_VALUE_TYPE @var{x}) -Returns the absolute value of @var{x}. -@end deftypefn - -@node Mode Switching -@section Mode Switching Instructions -@cindex mode switching -The following macros control mode switching optimizations: - -@defmac OPTIMIZE_MODE_SWITCHING (@var{entity}) -Define this macro if the port needs extra instructions inserted for mode -switching in an optimizing compilation. - -For an example, the SH4 can perform both single and double precision -floating point operations, but to perform a single precision operation, -the FPSCR PR bit has to be cleared, while for a double precision -operation, this bit has to be set. Changing the PR bit requires a general -purpose register as a scratch register, hence these FPSCR sets have to -be inserted before reload, i.e.@: you cannot put this into instruction emitting -or @code{TARGET_MACHINE_DEPENDENT_REORG}. - -You can have multiple entities that are mode-switched, and select at run time -which entities actually need it. @code{OPTIMIZE_MODE_SWITCHING} should -return nonzero for any @var{entity} that needs mode-switching. -If you define this macro, you also have to define -@code{NUM_MODES_FOR_MODE_SWITCHING}, @code{TARGET_MODE_NEEDED}, -@code{TARGET_MODE_PRIORITY} and @code{TARGET_MODE_EMIT}. -@code{TARGET_MODE_AFTER}, @code{TARGET_MODE_ENTRY}, and @code{TARGET_MODE_EXIT} -are optional. -@end defmac - -@defmac NUM_MODES_FOR_MODE_SWITCHING -If you define @code{OPTIMIZE_MODE_SWITCHING}, you have to define this as -initializer for an array of integers. Each initializer element -N refers to an entity that needs mode switching, and specifies the number -of different modes that might need to be set for this entity. -The position of the initializer in the initializer---starting counting at -zero---determines the integer that is used to refer to the mode-switched -entity in question. -In macros that take mode arguments / yield a mode result, modes are -represented as numbers 0 @dots{} N @minus{} 1. N is used to specify that no mode -switch is needed / supplied. -@end defmac - -@deftypefn {Target Hook} void TARGET_MODE_EMIT (int @var{entity}, int @var{mode}, int @var{prev_mode}, HARD_REG_SET @var{regs_live}) -Generate one or more insns to set @var{entity} to @var{mode}. -@var{hard_reg_live} is the set of hard registers live at the point where -the insn(s) are to be inserted. @var{prev_moxde} indicates the mode -to switch from. Sets of a lower numbered entity will be emitted before -sets of a higher numbered entity to a mode of the same or lower priority. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_MODE_NEEDED (int @var{entity}, rtx_insn *@var{insn}) -@var{entity} is an integer specifying a mode-switched entity. -If @code{OPTIMIZE_MODE_SWITCHING} is defined, you must define this macro -to return an integer value not larger than the corresponding element -in @code{NUM_MODES_FOR_MODE_SWITCHING}, to denote the mode that @var{entity} -must be switched into prior to the execution of @var{insn}. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_MODE_AFTER (int @var{entity}, int @var{mode}, rtx_insn *@var{insn}) -@var{entity} is an integer specifying a mode-switched entity. -If this macro is defined, it is evaluated for every @var{insn} during mode -switching. It determines the mode that an insn results -in (if different from the incoming mode). -@end deftypefn - -@deftypefn {Target Hook} int TARGET_MODE_ENTRY (int @var{entity}) -If this macro is defined, it is evaluated for every @var{entity} that -needs mode switching. It should evaluate to an integer, which is a mode -that @var{entity} is assumed to be switched to at function entry. -If @code{TARGET_MODE_ENTRY} is defined then @code{TARGET_MODE_EXIT} -must be defined. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_MODE_EXIT (int @var{entity}) -If this macro is defined, it is evaluated for every @var{entity} that -needs mode switching. It should evaluate to an integer, which is a mode -that @var{entity} is assumed to be switched to at function exit. -If @code{TARGET_MODE_EXIT} is defined then @code{TARGET_MODE_ENTRY} -must be defined. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_MODE_PRIORITY (int @var{entity}, int @var{n}) -This macro specifies the order in which modes for @var{entity} -are processed. 0 is the highest priority, -@code{NUM_MODES_FOR_MODE_SWITCHING[@var{entity}] - 1} the lowest. -The value of the macro should be an integer designating a mode -for @var{entity}. For any fixed @var{entity}, @code{mode_priority} -(@var{entity}, @var{n}) shall be a bijection in 0 @dots{} -@code{num_modes_for_mode_switching[@var{entity}] - 1}. -@end deftypefn - -@node Target Attributes -@section Defining target-specific uses of @code{__attribute__} -@cindex target attributes -@cindex machine attributes -@cindex attributes, target-specific - -Target-specific attributes may be defined for functions, data and types. -These are described using the following target hooks; they also need to -be documented in @file{extend.texi}. - -@deftypevr {Target Hook} {const struct attribute_spec *} TARGET_ATTRIBUTE_TABLE -If defined, this target hook points to an array of @samp{struct -attribute_spec} (defined in @file{tree-core.h}) specifying the machine -specific attributes for this target and some of the restrictions on the -entities to which these attributes are applied and the arguments they -take. -@end deftypevr - -@deftypefn {Target Hook} bool TARGET_ATTRIBUTE_TAKES_IDENTIFIER_P (const_tree @var{name}) -If defined, this target hook is a function which returns true if the -machine-specific attribute named @var{name} expects an identifier -given as its first argument to be passed on as a plain identifier, not -subjected to name lookup. If this is not defined, the default is -false for all machine-specific attributes. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_COMP_TYPE_ATTRIBUTES (const_tree @var{type1}, const_tree @var{type2}) -If defined, this target hook is a function which returns zero if the attributes on -@var{type1} and @var{type2} are incompatible, one if they are compatible, -and two if they are nearly compatible (which causes a warning to be -generated). If this is not defined, machine-specific attributes are -supposed always to be compatible. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SET_DEFAULT_TYPE_ATTRIBUTES (tree @var{type}) -If defined, this target hook is a function which assigns default attributes to -the newly defined @var{type}. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_MERGE_TYPE_ATTRIBUTES (tree @var{type1}, tree @var{type2}) -Define this target hook if the merging of type attributes needs special -handling. If defined, the result is a list of the combined -@code{TYPE_ATTRIBUTES} of @var{type1} and @var{type2}. It is assumed -that @code{comptypes} has already been called and returned 1. This -function may call @code{merge_attributes} to handle machine-independent -merging. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_MERGE_DECL_ATTRIBUTES (tree @var{olddecl}, tree @var{newdecl}) -Define this target hook if the merging of decl attributes needs special -handling. If defined, the result is a list of the combined -@code{DECL_ATTRIBUTES} of @var{olddecl} and @var{newdecl}. -@var{newdecl} is a duplicate declaration of @var{olddecl}. Examples of -when this is needed are when one attribute overrides another, or when an -attribute is nullified by a subsequent definition. This function may -call @code{merge_attributes} to handle machine-independent merging. - -@findex TARGET_DLLIMPORT_DECL_ATTRIBUTES -If the only target-specific handling you require is @samp{dllimport} -for Microsoft Windows targets, you should define the macro -@code{TARGET_DLLIMPORT_DECL_ATTRIBUTES} to @code{1}. The compiler -will then define a function called -@code{merge_dllimport_decl_attributes} which can then be defined as -the expansion of @code{TARGET_MERGE_DECL_ATTRIBUTES}. You can also -add @code{handle_dll_attribute} in the attribute table for your port -to perform initial processing of the @samp{dllimport} and -@samp{dllexport} attributes. This is done in @file{i386/cygwin.h} and -@file{i386/i386.cc}, for example. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_VALID_DLLIMPORT_ATTRIBUTE_P (const_tree @var{decl}) -@var{decl} is a variable or function with @code{__attribute__((dllimport))} -specified. Use this hook if the target needs to add extra validation -checks to @code{handle_dll_attribute}. -@end deftypefn - -@defmac TARGET_DECLSPEC -Define this macro to a nonzero value if you want to treat -@code{__declspec(X)} as equivalent to @code{__attribute((X))}. By -default, this behavior is enabled only for targets that define -@code{TARGET_DLLIMPORT_DECL_ATTRIBUTES}. The current implementation -of @code{__declspec} is via a built-in macro, but you should not rely -on this implementation detail. -@end defmac - -@deftypefn {Target Hook} void TARGET_INSERT_ATTRIBUTES (tree @var{node}, tree *@var{attr_ptr}) -Define this target hook if you want to be able to add attributes to a decl -when it is being created. This is normally useful for back ends which -wish to implement a pragma by using the attributes which correspond to -the pragma's effect. The @var{node} argument is the decl which is being -created. The @var{attr_ptr} argument is a pointer to the attribute list -for this decl. The list itself should not be modified, since it may be -shared with other decls, but attributes may be chained on the head of -the list and @code{*@var{attr_ptr}} modified to point to the new -attributes, or a copy of the list may be made if further changes are -needed. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_HANDLE_GENERIC_ATTRIBUTE (tree *@var{node}, tree @var{name}, tree @var{args}, int @var{flags}, bool *@var{no_add_attrs}) -Define this target hook if you want to be able to perform additional -target-specific processing of an attribute which is handled generically -by a front end. The arguments are the same as those which are passed to -attribute handlers. So far this only affects the @var{noinit} and -@var{section} attribute. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_FUNCTION_ATTRIBUTE_INLINABLE_P (const_tree @var{fndecl}) -@cindex inlining -This target hook returns @code{true} if it is OK to inline @var{fndecl} -into the current function, despite its having target-specific -attributes, @code{false} otherwise. By default, if a function has a -target specific attribute attached to it, it will not be inlined. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_OPTION_VALID_ATTRIBUTE_P (tree @var{fndecl}, tree @var{name}, tree @var{args}, int @var{flags}) -This hook is called to parse @code{attribute(target("..."))}, which -allows setting target-specific options on individual functions. -These function-specific options may differ -from the options specified on the command line. The hook should return -@code{true} if the options are valid. - -The hook should set the @code{DECL_FUNCTION_SPECIFIC_TARGET} field in -the function declaration to hold a pointer to a target-specific -@code{struct cl_target_option} structure. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_OPTION_SAVE (struct cl_target_option *@var{ptr}, struct gcc_options *@var{opts}, struct gcc_options *@var{opts_set}) -This hook is called to save any additional target-specific information -in the @code{struct cl_target_option} structure for function-specific -options from the @code{struct gcc_options} structure. -@xref{Option file format}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_OPTION_RESTORE (struct gcc_options *@var{opts}, struct gcc_options *@var{opts_set}, struct cl_target_option *@var{ptr}) -This hook is called to restore any additional target-specific -information in the @code{struct cl_target_option} structure for -function-specific options to the @code{struct gcc_options} structure. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_OPTION_POST_STREAM_IN (struct cl_target_option *@var{ptr}) -This hook is called to update target-specific information in the -@code{struct cl_target_option} structure after it is streamed in from -LTO bytecode. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_OPTION_PRINT (FILE *@var{file}, int @var{indent}, struct cl_target_option *@var{ptr}) -This hook is called to print any additional target-specific -information in the @code{struct cl_target_option} structure for -function-specific options. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_OPTION_PRAGMA_PARSE (tree @var{args}, tree @var{pop_target}) -This target hook parses the options for @code{#pragma GCC target}, which -sets the target-specific options for functions that occur later in the -input stream. The options accepted should be the same as those handled by the -@code{TARGET_OPTION_VALID_ATTRIBUTE_P} hook. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_OPTION_OVERRIDE (void) -Sometimes certain combinations of command options do not make sense on -a particular target machine. You can override the hook -@code{TARGET_OPTION_OVERRIDE} to take account of this. This hooks is called -once just after all the command options have been parsed. - -Don't use this hook to turn on various extra optimizations for -@option{-O}. That is what @code{TARGET_OPTION_OPTIMIZATION} is for. - -If you need to do something whenever the optimization level is -changed via the optimize attribute or pragma, see -@code{TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE} -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_OPTION_FUNCTION_VERSIONS (tree @var{decl1}, tree @var{decl2}) -This target hook returns @code{true} if @var{DECL1} and @var{DECL2} are -versions of the same function. @var{DECL1} and @var{DECL2} are function -versions if and only if they have the same function signature and -different target specific attributes, that is, they are compiled for -different target machines. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CAN_INLINE_P (tree @var{caller}, tree @var{callee}) -This target hook returns @code{false} if the @var{caller} function -cannot inline @var{callee}, based on target specific information. By -default, inlining is not allowed if the callee function has function -specific target options and the caller does not use the same options. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_UPDATE_IPA_FN_TARGET_INFO (unsigned int& @var{info}, const gimple* @var{stmt}) -Allow target to analyze all gimple statements for the given function to -record and update some target specific information for inlining. A typical -example is that a caller with one isa feature disabled is normally not -allowed to inline a callee with that same isa feature enabled even which is -attributed by always_inline, but with the conservative analysis on all -statements of the callee if we are able to guarantee the callee does not -exploit any instructions from the mismatch isa feature, it would be safe to -allow the caller to inline the callee. -@var{info} is one @code{unsigned int} value to record information in which -one set bit indicates one corresponding feature is detected in the analysis, -@var{stmt} is the statement being analyzed. Return true if target still -need to analyze the subsequent statements, otherwise return false to stop -subsequent analysis. -The default version of this hook returns false. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_NEED_IPA_FN_TARGET_INFO (const_tree @var{decl}, unsigned int& @var{info}) -Allow target to check early whether it is necessary to analyze all gimple -statements in the given function to update target specific information for -inlining. See hook @code{update_ipa_fn_target_info} for usage example of -target specific information. This hook is expected to be invoked ahead of -the iterating with hook @code{update_ipa_fn_target_info}. -@var{decl} is the function being analyzed, @var{info} is the same as what -in hook @code{update_ipa_fn_target_info}, target can do one time update -into @var{info} without iterating for some case. Return true if target -decides to analyze all gimple statements to collect information, otherwise -return false. -The default version of this hook returns false. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_RELAYOUT_FUNCTION (tree @var{fndecl}) -This target hook fixes function @var{fndecl} after attributes are processed. -Default does nothing. On ARM, the default function's alignment is updated -with the attribute target. -@end deftypefn - -@node Emulated TLS -@section Emulating TLS -@cindex Emulated TLS - -For targets whose psABI does not provide Thread Local Storage via -specific relocations and instruction sequences, an emulation layer is -used. A set of target hooks allows this emulation layer to be -configured for the requirements of a particular target. For instance -the psABI may in fact specify TLS support in terms of an emulation -layer. - -The emulation layer works by creating a control object for every TLS -object. To access the TLS object, a lookup function is provided -which, when given the address of the control object, will return the -address of the current thread's instance of the TLS object. - -@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_GET_ADDRESS -Contains the name of the helper function that uses a TLS control -object to locate a TLS instance. The default causes libgcc's -emulated TLS helper function to be used. -@end deftypevr - -@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_REGISTER_COMMON -Contains the name of the helper function that should be used at -program startup to register TLS objects that are implicitly -initialized to zero. If this is @code{NULL}, all TLS objects will -have explicit initializers. The default causes libgcc's emulated TLS -registration function to be used. -@end deftypevr - -@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_VAR_SECTION -Contains the name of the section in which TLS control variables should -be placed. The default of @code{NULL} allows these to be placed in -any section. -@end deftypevr - -@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_TMPL_SECTION -Contains the name of the section in which TLS initializers should be -placed. The default of @code{NULL} allows these to be placed in any -section. -@end deftypevr - -@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_VAR_PREFIX -Contains the prefix to be prepended to TLS control variable names. -The default of @code{NULL} uses a target-specific prefix. -@end deftypevr - -@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_TMPL_PREFIX -Contains the prefix to be prepended to TLS initializer objects. The -default of @code{NULL} uses a target-specific prefix. -@end deftypevr - -@deftypefn {Target Hook} tree TARGET_EMUTLS_VAR_FIELDS (tree @var{type}, tree *@var{name}) -Specifies a function that generates the FIELD_DECLs for a TLS control -object type. @var{type} is the RECORD_TYPE the fields are for and -@var{name} should be filled with the structure tag, if the default of -@code{__emutls_object} is unsuitable. The default creates a type suitable -for libgcc's emulated TLS function. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_EMUTLS_VAR_INIT (tree @var{var}, tree @var{decl}, tree @var{tmpl_addr}) -Specifies a function that generates the CONSTRUCTOR to initialize a -TLS control object. @var{var} is the TLS control object, @var{decl} -is the TLS object and @var{tmpl_addr} is the address of the -initializer. The default initializes libgcc's emulated TLS control object. -@end deftypefn - -@deftypevr {Target Hook} bool TARGET_EMUTLS_VAR_ALIGN_FIXED -Specifies whether the alignment of TLS control variable objects is -fixed and should not be increased as some backends may do to optimize -single objects. The default is false. -@end deftypevr - -@deftypevr {Target Hook} bool TARGET_EMUTLS_DEBUG_FORM_TLS_ADDRESS -Specifies whether a DWARF @code{DW_OP_form_tls_address} location descriptor -may be used to describe emulated TLS control objects. -@end deftypevr - -@node MIPS Coprocessors -@section Defining coprocessor specifics for MIPS targets. -@cindex MIPS coprocessor-definition macros - -The MIPS specification allows MIPS implementations to have as many as 4 -coprocessors, each with as many as 32 private registers. GCC supports -accessing these registers and transferring values between the registers -and memory using asm-ized variables. For example: - -@smallexample - register unsigned int cp0count asm ("c0r1"); - unsigned int d; - - d = cp0count + 3; -@end smallexample - -(``c0r1'' is the default name of register 1 in coprocessor 0; alternate -names may be added as described below, or the default names may be -overridden entirely in @code{SUBTARGET_CONDITIONAL_REGISTER_USAGE}.) - -Coprocessor registers are assumed to be epilogue-used; sets to them will -be preserved even if it does not appear that the register is used again -later in the function. - -Another note: according to the MIPS spec, coprocessor 1 (if present) is -the FPU@. One accesses COP1 registers through standard mips -floating-point support; they are not included in this mechanism. - -@node PCH Target -@section Parameters for Precompiled Header Validity Checking -@cindex parameters, precompiled headers - -@deftypefn {Target Hook} {void *} TARGET_GET_PCH_VALIDITY (size_t *@var{sz}) -This hook returns a pointer to the data needed by -@code{TARGET_PCH_VALID_P} and sets -@samp{*@var{sz}} to the size of the data in bytes. -@end deftypefn - -@deftypefn {Target Hook} {const char *} TARGET_PCH_VALID_P (const void *@var{data}, size_t @var{sz}) -This hook checks whether the options used to create a PCH file are -compatible with the current settings. It returns @code{NULL} -if so and a suitable error message if not. Error messages will -be presented to the user and must be localized using @samp{_(@var{msg})}. - -@var{data} is the data that was returned by @code{TARGET_GET_PCH_VALIDITY} -when the PCH file was created and @var{sz} is the size of that data in bytes. -It's safe to assume that the data was created by the same version of the -compiler, so no format checking is needed. - -The default definition of @code{default_pch_valid_p} should be -suitable for most targets. -@end deftypefn - -@deftypefn {Target Hook} {const char *} TARGET_CHECK_PCH_TARGET_FLAGS (int @var{pch_flags}) -If this hook is nonnull, the default implementation of -@code{TARGET_PCH_VALID_P} will use it to check for compatible values -of @code{target_flags}. @var{pch_flags} specifies the value that -@code{target_flags} had when the PCH file was created. The return -value is the same as for @code{TARGET_PCH_VALID_P}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_PREPARE_PCH_SAVE (void) -Called before writing out a PCH file. If the target has some -garbage-collected data that needs to be in a particular state on PCH loads, -it can use this hook to enforce that state. Very few targets need -to do anything here. -@end deftypefn - -@node C++ ABI -@section C++ ABI parameters -@cindex parameters, c++ abi - -@deftypefn {Target Hook} tree TARGET_CXX_GUARD_TYPE (void) -Define this hook to override the integer type used for guard variables. -These are used to implement one-time construction of static objects. The -default is long_long_integer_type_node. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CXX_GUARD_MASK_BIT (void) -This hook determines how guard variables are used. It should return -@code{false} (the default) if the first byte should be used. A return value of -@code{true} indicates that only the least significant bit should be used. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_CXX_GET_COOKIE_SIZE (tree @var{type}) -This hook returns the size of the cookie to use when allocating an array -whose elements have the indicated @var{type}. Assumes that it is already -known that a cookie is needed. The default is -@code{max(sizeof (size_t), alignof(type))}, as defined in section 2.7 of the -IA64/Generic C++ ABI@. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CXX_COOKIE_HAS_SIZE (void) -This hook should return @code{true} if the element size should be stored in -array cookies. The default is to return @code{false}. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_CXX_IMPORT_EXPORT_CLASS (tree @var{type}, int @var{import_export}) -If defined by a backend this hook allows the decision made to export -class @var{type} to be overruled. Upon entry @var{import_export} -will contain 1 if the class is going to be exported, @minus{}1 if it is going -to be imported and 0 otherwise. This function should return the -modified value and perform any other actions necessary to support the -backend's targeted operating system. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CXX_CDTOR_RETURNS_THIS (void) -This hook should return @code{true} if constructors and destructors return -the address of the object created/destroyed. The default is to return -@code{false}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CXX_KEY_METHOD_MAY_BE_INLINE (void) -This hook returns true if the key method for a class (i.e., the method -which, if defined in the current translation unit, causes the virtual -table to be emitted) may be an inline function. Under the standard -Itanium C++ ABI the key method may be an inline function so long as -the function is not declared inline in the class definition. Under -some variants of the ABI, an inline function can never be the key -method. The default is to return @code{true}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_CXX_DETERMINE_CLASS_DATA_VISIBILITY (tree @var{decl}) -@var{decl} is a virtual table, virtual table table, typeinfo object, -or other similar implicit class data object that will be emitted with -external linkage in this translation unit. No ELF visibility has been -explicitly specified. If the target needs to specify a visibility -other than that of the containing class, use this hook to set -@code{DECL_VISIBILITY} and @code{DECL_VISIBILITY_SPECIFIED}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CXX_CLASS_DATA_ALWAYS_COMDAT (void) -This hook returns true (the default) if virtual tables and other -similar implicit class data objects are always COMDAT if they have -external linkage. If this hook returns false, then class data for -classes whose virtual table will be emitted in only one translation -unit will not be COMDAT. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CXX_LIBRARY_RTTI_COMDAT (void) -This hook returns true (the default) if the RTTI information for -the basic types which is defined in the C++ runtime should always -be COMDAT, false if it should not be COMDAT. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CXX_USE_AEABI_ATEXIT (void) -This hook returns true if @code{__aeabi_atexit} (as defined by the ARM EABI) -should be used to register static destructors when @option{-fuse-cxa-atexit} -is in effect. The default is to return false to use @code{__cxa_atexit}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CXX_USE_ATEXIT_FOR_CXA_ATEXIT (void) -This hook returns true if the target @code{atexit} function can be used -in the same manner as @code{__cxa_atexit} to register C++ static -destructors. This requires that @code{atexit}-registered functions in -shared libraries are run in the correct order when the libraries are -unloaded. The default is to return false. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_CXX_ADJUST_CLASS_AT_DEFINITION (tree @var{type}) -@var{type} is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that has just -been defined. Use this hook to make adjustments to the class (eg, tweak -visibility or perform any other required target modifications). -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_CXX_DECL_MANGLING_CONTEXT (const_tree @var{decl}) -Return target-specific mangling context of @var{decl} or @code{NULL_TREE}. -@end deftypefn - -@node D Language and ABI -@section D ABI parameters -@cindex parameters, d abi - -@deftypefn {D Target Hook} void TARGET_D_CPU_VERSIONS (void) -Declare all environmental version identifiers relating to the target CPU -using the function @code{builtin_version}, which takes a string representing -the name of the version. Version identifiers predefined by this hook apply -to all modules that are being compiled and imported. -@end deftypefn - -@deftypefn {D Target Hook} void TARGET_D_OS_VERSIONS (void) -Similarly to @code{TARGET_D_CPU_VERSIONS}, but is used for versions -relating to the target operating system. -@end deftypefn - -@deftypefn {D Target Hook} void TARGET_D_REGISTER_CPU_TARGET_INFO (void) -Register all target information keys relating to the target CPU using the -function @code{d_add_target_info_handlers}, which takes a -@samp{struct d_target_info_spec} (defined in @file{d/d-target.h}). The keys -added by this hook are made available at compile time by the -@code{__traits(getTargetInfo)} extension, the result is an expression -describing the requested target information. -@end deftypefn - -@deftypefn {D Target Hook} void TARGET_D_REGISTER_OS_TARGET_INFO (void) -Same as @code{TARGET_D_CPU_TARGET_INFO}, but is used for keys relating to -the target operating system. -@end deftypefn - -@deftypevr {D Target Hook} {const char *} TARGET_D_MINFO_SECTION -Contains the name of the section in which module info references should be -placed. By default, the compiler puts all module info symbols in the -@code{"minfo"} section. Define this macro to override the string if a -different section name should be used. This section is expected to be -bracketed by two symbols @code{TARGET_D_MINFO_SECTION_START} and -@code{TARGET_D_MINFO_SECTION_END} to indicate the start and end address of -the section, so that the runtime library can collect all modules for each -loaded shared library and executable. Setting the value to @code{NULL} -disables the use of sections for storing module info altogether. -@end deftypevr - -@deftypevr {D Target Hook} {const char *} TARGET_D_MINFO_SECTION_START -If @code{TARGET_D_MINFO_SECTION} is defined, then this must also be defined -as the name of the symbol indicating the start address of the module info -section -@end deftypevr - -@deftypevr {D Target Hook} {const char *} TARGET_D_MINFO_SECTION_END -If @code{TARGET_D_MINFO_SECTION} is defined, then this must also be defined -as the name of the symbol indicating the end address of the module info -section -@end deftypevr - -@deftypefn {D Target Hook} bool TARGET_D_HAS_STDCALL_CONVENTION (unsigned int *@var{link_system}, unsigned int *@var{link_windows}) -Returns @code{true} if the target supports the stdcall calling convention. -The hook should also set @var{link_system} to @code{1} if the @code{stdcall} -attribute should be applied to functions with @code{extern(System)} linkage, -and @var{link_windows} to @code{1} to apply @code{stdcall} to functions with -@code{extern(Windows)} linkage. -@end deftypefn - -@deftypevr {D Target Hook} bool TARGET_D_TEMPLATES_ALWAYS_COMDAT -This flag is true if instantiated functions and variables are always COMDAT -if they have external linkage. If this flag is false, then instantiated -decls will be emitted as weak symbols. The default is @code{false}. -@end deftypevr - -@node Named Address Spaces -@section Adding support for named address spaces -@cindex named address spaces - -The draft technical report of the ISO/IEC JTC1 S22 WG14 N1275 -standards committee, @cite{Programming Languages - C - Extensions to -support embedded processors}, specifies a syntax for embedded -processors to specify alternate address spaces. You can configure a -GCC port to support section 5.1 of the draft report to add support for -address spaces other than the default address space. These address -spaces are new keywords that are similar to the @code{volatile} and -@code{const} type attributes. - -Pointers to named address spaces can have a different size than -pointers to the generic address space. - -For example, the SPU port uses the @code{__ea} address space to refer -to memory in the host processor, rather than memory local to the SPU -processor. Access to memory in the @code{__ea} address space involves -issuing DMA operations to move data between the host processor and the -local processor memory address space. Pointers in the @code{__ea} -address space are either 32 bits or 64 bits based on the -@option{-mea32} or @option{-mea64} switches (native SPU pointers are -always 32 bits). - -Internally, address spaces are represented as a small integer in the -range 0 to 15 with address space 0 being reserved for the generic -address space. - -To register a named address space qualifier keyword with the C front end, -the target may call the @code{c_register_addr_space} routine. For example, -the SPU port uses the following to declare @code{__ea} as the keyword for -named address space #1: -@smallexample -#define ADDR_SPACE_EA 1 -c_register_addr_space ("__ea", ADDR_SPACE_EA); -@end smallexample - -@deftypefn {Target Hook} scalar_int_mode TARGET_ADDR_SPACE_POINTER_MODE (addr_space_t @var{address_space}) -Define this to return the machine mode to use for pointers to -@var{address_space} if the target supports named address spaces. -The default version of this hook returns @code{ptr_mode}. -@end deftypefn - -@deftypefn {Target Hook} scalar_int_mode TARGET_ADDR_SPACE_ADDRESS_MODE (addr_space_t @var{address_space}) -Define this to return the machine mode to use for addresses in -@var{address_space} if the target supports named address spaces. -The default version of this hook returns @code{Pmode}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ADDR_SPACE_VALID_POINTER_MODE (scalar_int_mode @var{mode}, addr_space_t @var{as}) -Define this to return nonzero if the port can handle pointers -with machine mode @var{mode} to address space @var{as}. This target -hook is the same as the @code{TARGET_VALID_POINTER_MODE} target hook, -except that it includes explicit named address space support. The default -version of this hook returns true for the modes returned by either the -@code{TARGET_ADDR_SPACE_POINTER_MODE} or @code{TARGET_ADDR_SPACE_ADDRESS_MODE} -target hooks for the given address space. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ADDR_SPACE_LEGITIMATE_ADDRESS_P (machine_mode @var{mode}, rtx @var{exp}, bool @var{strict}, addr_space_t @var{as}) -Define this to return true if @var{exp} is a valid address for mode -@var{mode} in the named address space @var{as}. The @var{strict} -parameter says whether strict addressing is in effect after reload has -finished. This target hook is the same as the -@code{TARGET_LEGITIMATE_ADDRESS_P} target hook, except that it includes -explicit named address space support. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_ADDR_SPACE_LEGITIMIZE_ADDRESS (rtx @var{x}, rtx @var{oldx}, machine_mode @var{mode}, addr_space_t @var{as}) -Define this to modify an invalid address @var{x} to be a valid address -with mode @var{mode} in the named address space @var{as}. This target -hook is the same as the @code{TARGET_LEGITIMIZE_ADDRESS} target hook, -except that it includes explicit named address space support. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ADDR_SPACE_SUBSET_P (addr_space_t @var{subset}, addr_space_t @var{superset}) -Define this to return whether the @var{subset} named address space is -contained within the @var{superset} named address space. Pointers to -a named address space that is a subset of another named address space -will be converted automatically without a cast if used together in -arithmetic operations. Pointers to a superset address space can be -converted to pointers to a subset address space via explicit casts. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID (addr_space_t @var{as}) -Define this to modify the default handling of address 0 for the -address space. Return true if 0 should be considered a valid address. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_ADDR_SPACE_CONVERT (rtx @var{op}, tree @var{from_type}, tree @var{to_type}) -Define this to convert the pointer expression represented by the RTL -@var{op} with type @var{from_type} that points to a named address -space to a new pointer expression with type @var{to_type} that points -to a different named address space. When this hook it called, it is -guaranteed that one of the two address spaces is a subset of the other, -as determined by the @code{TARGET_ADDR_SPACE_SUBSET_P} target hook. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_ADDR_SPACE_DEBUG (addr_space_t @var{as}) -Define this to define how the address space is encoded in dwarf. -The result is the value to be used with @code{DW_AT_address_class}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ADDR_SPACE_DIAGNOSE_USAGE (addr_space_t @var{as}, location_t @var{loc}) -Define this hook if the availability of an address space depends on -command line options and some diagnostics should be printed when the -address space is used. This hook is called during parsing and allows -to emit a better diagnostic compared to the case where the address space -was not registered with @code{c_register_addr_space}. @var{as} is -the address space as registered with @code{c_register_addr_space}. -@var{loc} is the location of the address space qualifier token. -The default implementation does nothing. -@end deftypefn - -@node Misc -@section Miscellaneous Parameters -@cindex parameters, miscellaneous - -@c prevent bad page break with this line -Here are several miscellaneous parameters. - -@defmac HAS_LONG_COND_BRANCH -Define this boolean macro to indicate whether or not your architecture -has conditional branches that can span all of memory. It is used in -conjunction with an optimization that partitions hot and cold basic -blocks into separate sections of the executable. If this macro is -set to false, gcc will convert any conditional branches that attempt -to cross between sections into unconditional branches or indirect jumps. -@end defmac - -@defmac HAS_LONG_UNCOND_BRANCH -Define this boolean macro to indicate whether or not your architecture -has unconditional branches that can span all of memory. It is used in -conjunction with an optimization that partitions hot and cold basic -blocks into separate sections of the executable. If this macro is -set to false, gcc will convert any unconditional branches that attempt -to cross between sections into indirect jumps. -@end defmac - -@defmac CASE_VECTOR_MODE -An alias for a machine mode name. This is the machine mode that -elements of a jump-table should have. -@end defmac - -@defmac CASE_VECTOR_SHORTEN_MODE (@var{min_offset}, @var{max_offset}, @var{body}) -Optional: return the preferred mode for an @code{addr_diff_vec} -when the minimum and maximum offset are known. If you define this, -it enables extra code in branch shortening to deal with @code{addr_diff_vec}. -To make this work, you also have to define @code{INSN_ALIGN} and -make the alignment for @code{addr_diff_vec} explicit. -The @var{body} argument is provided so that the offset_unsigned and scale -flags can be updated. -@end defmac - -@defmac CASE_VECTOR_PC_RELATIVE -Define this macro to be a C expression to indicate when jump-tables -should contain relative addresses. You need not define this macro if -jump-tables never contain relative addresses, or jump-tables should -contain relative addresses only when @option{-fPIC} or @option{-fPIC} -is in effect. -@end defmac - -@deftypefn {Target Hook} {unsigned int} TARGET_CASE_VALUES_THRESHOLD (void) -This function return the smallest number of different values for which it -is best to use a jump-table instead of a tree of conditional branches. -The default is four for machines with a @code{casesi} instruction and -five otherwise. This is best for most machines. -@end deftypefn - -@defmac WORD_REGISTER_OPERATIONS -Define this macro to 1 if operations between registers with integral mode -smaller than a word are always performed on the entire register. To be -more explicit, if you start with a pair of @code{word_mode} registers with -known values and you do a subword, for example @code{QImode}, addition on -the low part of the registers, then the compiler may consider that the -result has a known value in @code{word_mode} too if the macro is defined -to 1. Most RISC machines have this property and most CISC machines do not. -@end defmac - -@deftypefn {Target Hook} {unsigned int} TARGET_MIN_ARITHMETIC_PRECISION (void) -On some RISC architectures with 64-bit registers, the processor also -maintains 32-bit condition codes that make it possible to do real 32-bit -arithmetic, although the operations are performed on the full registers. - -On such architectures, defining this hook to 32 tells the compiler to try -using 32-bit arithmetical operations setting the condition codes instead -of doing full 64-bit arithmetic. - -More generally, define this hook on RISC architectures if you want the -compiler to try using arithmetical operations setting the condition codes -with a precision lower than the word precision. - -You need not define this hook if @code{WORD_REGISTER_OPERATIONS} is not -defined to 1. -@end deftypefn - -@defmac LOAD_EXTEND_OP (@var{mem_mode}) -Define this macro to be a C expression indicating when insns that read -memory in @var{mem_mode}, an integral mode narrower than a word, set the -bits outside of @var{mem_mode} to be either the sign-extension or the -zero-extension of the data read. Return @code{SIGN_EXTEND} for values -of @var{mem_mode} for which the -insn sign-extends, @code{ZERO_EXTEND} for which it zero-extends, and -@code{UNKNOWN} for other modes. - -This macro is not called with @var{mem_mode} non-integral or with a width -greater than or equal to @code{BITS_PER_WORD}, so you may return any -value in this case. Do not define this macro if it would always return -@code{UNKNOWN}. On machines where this macro is defined, you will normally -define it as the constant @code{SIGN_EXTEND} or @code{ZERO_EXTEND}. - -You may return a non-@code{UNKNOWN} value even if for some hard registers -the sign extension is not performed, if for the @code{REGNO_REG_CLASS} -of these hard registers @code{TARGET_CAN_CHANGE_MODE_CLASS} returns false -when the @var{from} mode is @var{mem_mode} and the @var{to} mode is any -integral mode larger than this but not larger than @code{word_mode}. - -You must return @code{UNKNOWN} if for some hard registers that allow this -mode, @code{TARGET_CAN_CHANGE_MODE_CLASS} says that they cannot change to -@code{word_mode}, but that they can change to another integral mode that -is larger then @var{mem_mode} but still smaller than @code{word_mode}. -@end defmac - -@defmac SHORT_IMMEDIATES_SIGN_EXTEND -Define this macro to 1 if loading short immediate values into registers sign -extends. -@end defmac - -@deftypefn {Target Hook} {unsigned int} TARGET_MIN_DIVISIONS_FOR_RECIP_MUL (machine_mode @var{mode}) -When @option{-ffast-math} is in effect, GCC tries to optimize -divisions by the same divisor, by turning them into multiplications by -the reciprocal. This target hook specifies the minimum number of divisions -that should be there for GCC to perform the optimization for a variable -of mode @var{mode}. The default implementation returns 3 if the machine -has an instruction for the division, and 2 if it does not. -@end deftypefn - -@defmac MOVE_MAX -The maximum number of bytes that a single instruction can move quickly -between memory and registers or between two memory locations. -@end defmac - -@defmac MAX_MOVE_MAX -The maximum number of bytes that a single instruction can move quickly -between memory and registers or between two memory locations. If this -is undefined, the default is @code{MOVE_MAX}. Otherwise, it is the -constant value that is the largest value that @code{MOVE_MAX} can have -at run-time. -@end defmac - -@defmac SHIFT_COUNT_TRUNCATED -A C expression that is nonzero if on this machine the number of bits -actually used for the count of a shift operation is equal to the number -of bits needed to represent the size of the object being shifted. When -this macro is nonzero, the compiler will assume that it is safe to omit -a sign-extend, zero-extend, and certain bitwise `and' instructions that -truncates the count of a shift operation. On machines that have -instructions that act on bit-fields at variable positions, which may -include `bit test' instructions, a nonzero @code{SHIFT_COUNT_TRUNCATED} -also enables deletion of truncations of the values that serve as -arguments to bit-field instructions. - -If both types of instructions truncate the count (for shifts) and -position (for bit-field operations), or if no variable-position bit-field -instructions exist, you should define this macro. - -However, on some machines, such as the 80386 and the 680x0, truncation -only applies to shift operations and not the (real or pretended) -bit-field operations. Define @code{SHIFT_COUNT_TRUNCATED} to be zero on -such machines. Instead, add patterns to the @file{md} file that include -the implied truncation of the shift instructions. - -You need not define this macro if it would always have the value of zero. -@end defmac - -@anchor{TARGET_SHIFT_TRUNCATION_MASK} -@deftypefn {Target Hook} {unsigned HOST_WIDE_INT} TARGET_SHIFT_TRUNCATION_MASK (machine_mode @var{mode}) -This function describes how the standard shift patterns for @var{mode} -deal with shifts by negative amounts or by more than the width of the mode. -@xref{shift patterns}. - -On many machines, the shift patterns will apply a mask @var{m} to the -shift count, meaning that a fixed-width shift of @var{x} by @var{y} is -equivalent to an arbitrary-width shift of @var{x} by @var{y & m}. If -this is true for mode @var{mode}, the function should return @var{m}, -otherwise it should return 0. A return value of 0 indicates that no -particular behavior is guaranteed. - -Note that, unlike @code{SHIFT_COUNT_TRUNCATED}, this function does -@emph{not} apply to general shift rtxes; it applies only to instructions -that are generated by the named shift patterns. - -The default implementation of this function returns -@code{GET_MODE_BITSIZE (@var{mode}) - 1} if @code{SHIFT_COUNT_TRUNCATED} -and 0 otherwise. This definition is always safe, but if -@code{SHIFT_COUNT_TRUNCATED} is false, and some shift patterns -nevertheless truncate the shift count, you may get better code -by overriding it. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_TRULY_NOOP_TRUNCATION (poly_uint64 @var{outprec}, poly_uint64 @var{inprec}) -This hook returns true if it is safe to ``convert'' a value of -@var{inprec} bits to one of @var{outprec} bits (where @var{outprec} is -smaller than @var{inprec}) by merely operating on it as if it had only -@var{outprec} bits. The default returns true unconditionally, which -is correct for most machines. When @code{TARGET_TRULY_NOOP_TRUNCATION} -returns false, the machine description should provide a @code{trunc} -optab to specify the RTL that performs the required truncation. - -If @code{TARGET_MODES_TIEABLE_P} returns false for a pair of modes, -suboptimal code can result if this hook returns true for the corresponding -mode sizes. Making this hook return false in such cases may improve things. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_MODE_REP_EXTENDED (scalar_int_mode @var{mode}, scalar_int_mode @var{rep_mode}) -The representation of an integral mode can be such that the values -are always extended to a wider integral mode. Return -@code{SIGN_EXTEND} if values of @var{mode} are represented in -sign-extended form to @var{rep_mode}. Return @code{UNKNOWN} -otherwise. (Currently, none of the targets use zero-extended -representation this way so unlike @code{LOAD_EXTEND_OP}, -@code{TARGET_MODE_REP_EXTENDED} is expected to return either -@code{SIGN_EXTEND} or @code{UNKNOWN}. Also no target extends -@var{mode} to @var{rep_mode} so that @var{rep_mode} is not the next -widest integral mode and currently we take advantage of this fact.) - -Similarly to @code{LOAD_EXTEND_OP} you may return a non-@code{UNKNOWN} -value even if the extension is not performed on certain hard registers -as long as for the @code{REGNO_REG_CLASS} of these hard registers -@code{TARGET_CAN_CHANGE_MODE_CLASS} returns false. - -Note that @code{TARGET_MODE_REP_EXTENDED} and @code{LOAD_EXTEND_OP} -describe two related properties. If you define -@code{TARGET_MODE_REP_EXTENDED (mode, word_mode)} you probably also want -to define @code{LOAD_EXTEND_OP (mode)} to return the same type of -extension. - -In order to enforce the representation of @code{mode}, -@code{TARGET_TRULY_NOOP_TRUNCATION} should return false when truncating to -@code{mode}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_SETJMP_PRESERVES_NONVOLATILE_REGS_P (void) -On some targets, it is assumed that the compiler will spill all pseudos - that are live across a call to @code{setjmp}, while other targets treat - @code{setjmp} calls as normal function calls. - - This hook returns false if @code{setjmp} calls do not preserve all - non-volatile registers so that gcc that must spill all pseudos that are - live across @code{setjmp} calls. Define this to return true if the - target does not need to spill all pseudos live across @code{setjmp} calls. - The default implementation conservatively assumes all pseudos must be - spilled across @code{setjmp} calls. -@end deftypefn - -@defmac STORE_FLAG_VALUE -A C expression describing the value returned by a comparison operator -with an integral mode and stored by a store-flag instruction -(@samp{cstore@var{mode}4}) when the condition is true. This description must -apply to @emph{all} the @samp{cstore@var{mode}4} patterns and all the -comparison operators whose results have a @code{MODE_INT} mode. - -A value of 1 or @minus{}1 means that the instruction implementing the -comparison operator returns exactly 1 or @minus{}1 when the comparison is true -and 0 when the comparison is false. Otherwise, the value indicates -which bits of the result are guaranteed to be 1 when the comparison is -true. This value is interpreted in the mode of the comparison -operation, which is given by the mode of the first operand in the -@samp{cstore@var{mode}4} pattern. Either the low bit or the sign bit of -@code{STORE_FLAG_VALUE} be on. Presently, only those bits are used by -the compiler. - -If @code{STORE_FLAG_VALUE} is neither 1 or @minus{}1, the compiler will -generate code that depends only on the specified bits. It can also -replace comparison operators with equivalent operations if they cause -the required bits to be set, even if the remaining bits are undefined. -For example, on a machine whose comparison operators return an -@code{SImode} value and where @code{STORE_FLAG_VALUE} is defined as -@samp{0x80000000}, saying that just the sign bit is relevant, the -expression - -@smallexample -(ne:SI (and:SI @var{x} (const_int @var{power-of-2})) (const_int 0)) -@end smallexample - -@noindent -can be converted to - -@smallexample -(ashift:SI @var{x} (const_int @var{n})) -@end smallexample - -@noindent -where @var{n} is the appropriate shift count to move the bit being -tested into the sign bit. - -There is no way to describe a machine that always sets the low-order bit -for a true value, but does not guarantee the value of any other bits, -but we do not know of any machine that has such an instruction. If you -are trying to port GCC to such a machine, include an instruction to -perform a logical-and of the result with 1 in the pattern for the -comparison operators and let us know at @email{gcc@@gcc.gnu.org}. - -Often, a machine will have multiple instructions that obtain a value -from a comparison (or the condition codes). Here are rules to guide the -choice of value for @code{STORE_FLAG_VALUE}, and hence the instructions -to be used: - -@itemize @bullet -@item -Use the shortest sequence that yields a valid definition for -@code{STORE_FLAG_VALUE}. It is more efficient for the compiler to -``normalize'' the value (convert it to, e.g., 1 or 0) than for the -comparison operators to do so because there may be opportunities to -combine the normalization with other operations. - -@item -For equal-length sequences, use a value of 1 or @minus{}1, with @minus{}1 being -slightly preferred on machines with expensive jumps and 1 preferred on -other machines. - -@item -As a second choice, choose a value of @samp{0x80000001} if instructions -exist that set both the sign and low-order bits but do not define the -others. - -@item -Otherwise, use a value of @samp{0x80000000}. -@end itemize - -Many machines can produce both the value chosen for -@code{STORE_FLAG_VALUE} and its negation in the same number of -instructions. On those machines, you should also define a pattern for -those cases, e.g., one matching - -@smallexample -(set @var{A} (neg:@var{m} (ne:@var{m} @var{B} @var{C}))) -@end smallexample - -Some machines can also perform @code{and} or @code{plus} operations on -condition code values with less instructions than the corresponding -@samp{cstore@var{mode}4} insn followed by @code{and} or @code{plus}. On those -machines, define the appropriate patterns. Use the names @code{incscc} -and @code{decscc}, respectively, for the patterns which perform -@code{plus} or @code{minus} operations on condition code values. See -@file{rs6000.md} for some examples. The GNU Superoptimizer can be used to -find such instruction sequences on other machines. - -If this macro is not defined, the default value, 1, is used. You need -not define @code{STORE_FLAG_VALUE} if the machine has no store-flag -instructions, or if the value generated by these instructions is 1. -@end defmac - -@defmac FLOAT_STORE_FLAG_VALUE (@var{mode}) -A C expression that gives a nonzero @code{REAL_VALUE_TYPE} value that is -returned when comparison operators with floating-point results are true. -Define this macro on machines that have comparison operations that return -floating-point values. If there are no such operations, do not define -this macro. -@end defmac - -@defmac VECTOR_STORE_FLAG_VALUE (@var{mode}) -A C expression that gives an rtx representing the nonzero true element -for vector comparisons. The returned rtx should be valid for the inner -mode of @var{mode} which is guaranteed to be a vector mode. Define -this macro on machines that have vector comparison operations that -return a vector result. If there are no such operations, do not define -this macro. Typically, this macro is defined as @code{const1_rtx} or -@code{constm1_rtx}. This macro may return @code{NULL_RTX} to prevent -the compiler optimizing such vector comparison operations for the -given mode. -@end defmac - -@defmac CLZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value}) -@defmacx CTZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value}) -A C expression that indicates whether the architecture defines a value -for @code{clz} or @code{ctz} with a zero operand. -A result of @code{0} indicates the value is undefined. -If the value is defined for only the RTL expression, the macro should -evaluate to @code{1}; if the value applies also to the corresponding optab -entry (which is normally the case if it expands directly into -the corresponding RTL), then the macro should evaluate to @code{2}. -In the cases where the value is defined, @var{value} should be set to -this value. - -If this macro is not defined, the value of @code{clz} or -@code{ctz} at zero is assumed to be undefined. - -This macro must be defined if the target's expansion for @code{ffs} -relies on a particular value to get correct results. Otherwise it -is not necessary, though it may be used to optimize some corner cases, and -to provide a default expansion for the @code{ffs} optab. - -Note that regardless of this macro the ``definedness'' of @code{clz} -and @code{ctz} at zero do @emph{not} extend to the builtin functions -visible to the user. Thus one may be free to adjust the value at will -to match the target expansion of these operations without fear of -breaking the API@. -@end defmac - -@defmac Pmode -An alias for the machine mode for pointers. On most machines, define -this to be the integer mode corresponding to the width of a hardware -pointer; @code{SImode} on 32-bit machine or @code{DImode} on 64-bit machines. -On some machines you must define this to be one of the partial integer -modes, such as @code{PSImode}. - -The width of @code{Pmode} must be at least as large as the value of -@code{POINTER_SIZE}. If it is not equal, you must define the macro -@code{POINTERS_EXTEND_UNSIGNED} to specify how pointers are extended -to @code{Pmode}. -@end defmac - -@defmac FUNCTION_MODE -An alias for the machine mode used for memory references to functions -being called, in @code{call} RTL expressions. On most CISC machines, -where an instruction can begin at any byte address, this should be -@code{QImode}. On most RISC machines, where all instructions have fixed -size and alignment, this should be a mode with the same size and alignment -as the machine instruction words - typically @code{SImode} or @code{HImode}. -@end defmac - -@defmac STDC_0_IN_SYSTEM_HEADERS -In normal operation, the preprocessor expands @code{__STDC__} to the -constant 1, to signify that GCC conforms to ISO Standard C@. On some -hosts, like Solaris, the system compiler uses a different convention, -where @code{__STDC__} is normally 0, but is 1 if the user specifies -strict conformance to the C Standard. - -Defining @code{STDC_0_IN_SYSTEM_HEADERS} makes GNU CPP follows the host -convention when processing system header files, but when processing user -files @code{__STDC__} will always expand to 1. -@end defmac - -@deftypefn {C Target Hook} {const char *} TARGET_C_PREINCLUDE (void) -Define this hook to return the name of a header file to be included at -the start of all compilations, as if it had been included with -@code{#include <@var{file}>}. If this hook returns @code{NULL}, or is -not defined, or the header is not found, or if the user specifies -@option{-ffreestanding} or @option{-nostdinc}, no header is included. - -This hook can be used together with a header provided by the system C -library to implement ISO C requirements for certain macros to be -predefined that describe properties of the whole implementation rather -than just the compiler. -@end deftypefn - -@deftypefn {C Target Hook} bool TARGET_CXX_IMPLICIT_EXTERN_C (const char*@var{}) -Define this hook to add target-specific C++ implicit extern C functions. -If this function returns true for the name of a file-scope function, that -function implicitly gets extern "C" linkage rather than whatever language -linkage the declaration would normally have. An example of such function -is WinMain on Win32 targets. -@end deftypefn - -@defmac SYSTEM_IMPLICIT_EXTERN_C -Define this macro if the system header files do not support C++@. -This macro handles system header files by pretending that system -header files are enclosed in @samp{extern "C" @{@dots{}@}}. -@end defmac - -@findex #pragma -@findex pragma -@defmac REGISTER_TARGET_PRAGMAS () -Define this macro if you want to implement any target-specific pragmas. -If defined, it is a C expression which makes a series of calls to -@code{c_register_pragma} or @code{c_register_pragma_with_expansion} -for each pragma. The macro may also do any -setup required for the pragmas. - -The primary reason to define this macro is to provide compatibility with -other compilers for the same target. In general, we discourage -definition of target-specific pragmas for GCC@. - -If the pragma can be implemented by attributes then you should consider -defining the target hook @samp{TARGET_INSERT_ATTRIBUTES} as well. - -Preprocessor macros that appear on pragma lines are not expanded. All -@samp{#pragma} directives that do not match any registered pragma are -silently ignored, unless the user specifies @option{-Wunknown-pragmas}. -@end defmac - -@deftypefun void c_register_pragma (const char *@var{space}, const char *@var{name}, void (*@var{callback}) (struct cpp_reader *)) -@deftypefunx void c_register_pragma_with_expansion (const char *@var{space}, const char *@var{name}, void (*@var{callback}) (struct cpp_reader *)) - -Each call to @code{c_register_pragma} or -@code{c_register_pragma_with_expansion} establishes one pragma. The -@var{callback} routine will be called when the preprocessor encounters a -pragma of the form - -@smallexample -#pragma [@var{space}] @var{name} @dots{} -@end smallexample - -@var{space} is the case-sensitive namespace of the pragma, or -@code{NULL} to put the pragma in the global namespace. The callback -routine receives @var{pfile} as its first argument, which can be passed -on to cpplib's functions if necessary. You can lex tokens after the -@var{name} by calling @code{pragma_lex}. Tokens that are not read by the -callback will be silently ignored. The end of the line is indicated by -a token of type @code{CPP_EOF}. Macro expansion occurs on the -arguments of pragmas registered with -@code{c_register_pragma_with_expansion} but not on the arguments of -pragmas registered with @code{c_register_pragma}. - -Note that the use of @code{pragma_lex} is specific to the C and C++ -compilers. It will not work in the Java or Fortran compilers, or any -other language compilers for that matter. Thus if @code{pragma_lex} is going -to be called from target-specific code, it must only be done so when -building the C and C++ compilers. This can be done by defining the -variables @code{c_target_objs} and @code{cxx_target_objs} in the -target entry in the @file{config.gcc} file. These variables should name -the target-specific, language-specific object file which contains the -code that uses @code{pragma_lex}. Note it will also be necessary to add a -rule to the makefile fragment pointed to by @code{tmake_file} that shows -how to build this object file. -@end deftypefun - -@defmac HANDLE_PRAGMA_PACK_WITH_EXPANSION -Define this macro if macros should be expanded in the -arguments of @samp{#pragma pack}. -@end defmac - -@defmac TARGET_DEFAULT_PACK_STRUCT -If your target requires a structure packing default other than 0 (meaning -the machine default), define this macro to the necessary value (in bytes). -This must be a value that would also be valid to use with -@samp{#pragma pack()} (that is, a small power of two). -@end defmac - -@defmac DOLLARS_IN_IDENTIFIERS -Define this macro to control use of the character @samp{$} in -identifier names for the C family of languages. 0 means @samp{$} is -not allowed by default; 1 means it is allowed. 1 is the default; -there is no need to define this macro in that case. -@end defmac - -@defmac INSN_SETS_ARE_DELAYED (@var{insn}) -Define this macro as a C expression that is nonzero if it is safe for the -delay slot scheduler to place instructions in the delay slot of @var{insn}, -even if they appear to use a resource set or clobbered in @var{insn}. -@var{insn} is always a @code{jump_insn} or an @code{insn}; GCC knows that -every @code{call_insn} has this behavior. On machines where some @code{insn} -or @code{jump_insn} is really a function call and hence has this behavior, -you should define this macro. - -You need not define this macro if it would always return zero. -@end defmac - -@defmac INSN_REFERENCES_ARE_DELAYED (@var{insn}) -Define this macro as a C expression that is nonzero if it is safe for the -delay slot scheduler to place instructions in the delay slot of @var{insn}, -even if they appear to set or clobber a resource referenced in @var{insn}. -@var{insn} is always a @code{jump_insn} or an @code{insn}. On machines where -some @code{insn} or @code{jump_insn} is really a function call and its operands -are registers whose use is actually in the subroutine it calls, you should -define this macro. Doing so allows the delay slot scheduler to move -instructions which copy arguments into the argument registers into the delay -slot of @var{insn}. - -You need not define this macro if it would always return zero. -@end defmac - -@defmac MULTIPLE_SYMBOL_SPACES -Define this macro as a C expression that is nonzero if, in some cases, -global symbols from one translation unit may not be bound to undefined -symbols in another translation unit without user intervention. For -instance, under Microsoft Windows symbols must be explicitly imported -from shared libraries (DLLs). - -You need not define this macro if it would always evaluate to zero. -@end defmac - -@deftypefn {Target Hook} {rtx_insn *} TARGET_MD_ASM_ADJUST (vec<rtx>& @var{outputs}, vec<rtx>& @var{inputs}, vec<machine_mode>& @var{input_modes}, vec<const char *>& @var{constraints}, vec<rtx>& @var{clobbers}, HARD_REG_SET& @var{clobbered_regs}, location_t @var{loc}) -This target hook may add @dfn{clobbers} to @var{clobbers} and -@var{clobbered_regs} for any hard regs the port wishes to automatically -clobber for an asm. The @var{outputs} and @var{inputs} may be inspected -to avoid clobbering a register that is already used by the asm. @var{loc} -is the source location of the asm. - -It may modify the @var{outputs}, @var{inputs}, @var{input_modes}, and -@var{constraints} as necessary for other pre-processing. In this case the -return value is a sequence of insns to emit after the asm. Note that -changes to @var{inputs} must be accompanied by the corresponding changes -to @var{input_modes}. -@end deftypefn - -@defmac MATH_LIBRARY -Define this macro as a C string constant for the linker argument to link -in the system math library, minus the initial @samp{"-l"}, or -@samp{""} if the target does not have a -separate math library. - -You need only define this macro if the default of @samp{"m"} is wrong. -@end defmac - -@defmac LIBRARY_PATH_ENV -Define this macro as a C string constant for the environment variable that -specifies where the linker should look for libraries. - -You need only define this macro if the default of @samp{"LIBRARY_PATH"} -is wrong. -@end defmac - -@defmac TARGET_POSIX_IO -Define this macro if the target supports the following POSIX@ file -functions, access, mkdir and file locking with fcntl / F_SETLKW@. -Defining @code{TARGET_POSIX_IO} will enable the test coverage code -to use file locking when exiting a program, which avoids race conditions -if the program has forked. It will also create directories at run-time -for cross-profiling. -@end defmac - -@defmac MAX_CONDITIONAL_EXECUTE - -A C expression for the maximum number of instructions to execute via -conditional execution instructions instead of a branch. A value of -@code{BRANCH_COST}+1 is the default. -@end defmac - -@defmac IFCVT_MODIFY_TESTS (@var{ce_info}, @var{true_expr}, @var{false_expr}) -Used if the target needs to perform machine-dependent modifications on the -conditionals used for turning basic blocks into conditionally executed code. -@var{ce_info} points to a data structure, @code{struct ce_if_block}, which -contains information about the currently processed blocks. @var{true_expr} -and @var{false_expr} are the tests that are used for converting the -then-block and the else-block, respectively. Set either @var{true_expr} or -@var{false_expr} to a null pointer if the tests cannot be converted. -@end defmac - -@defmac IFCVT_MODIFY_MULTIPLE_TESTS (@var{ce_info}, @var{bb}, @var{true_expr}, @var{false_expr}) -Like @code{IFCVT_MODIFY_TESTS}, but used when converting more complicated -if-statements into conditions combined by @code{and} and @code{or} operations. -@var{bb} contains the basic block that contains the test that is currently -being processed and about to be turned into a condition. -@end defmac - -@defmac IFCVT_MODIFY_INSN (@var{ce_info}, @var{pattern}, @var{insn}) -A C expression to modify the @var{PATTERN} of an @var{INSN} that is to -be converted to conditional execution format. @var{ce_info} points to -a data structure, @code{struct ce_if_block}, which contains information -about the currently processed blocks. -@end defmac - -@defmac IFCVT_MODIFY_FINAL (@var{ce_info}) -A C expression to perform any final machine dependent modifications in -converting code to conditional execution. The involved basic blocks -can be found in the @code{struct ce_if_block} structure that is pointed -to by @var{ce_info}. -@end defmac - -@defmac IFCVT_MODIFY_CANCEL (@var{ce_info}) -A C expression to cancel any machine dependent modifications in -converting code to conditional execution. The involved basic blocks -can be found in the @code{struct ce_if_block} structure that is pointed -to by @var{ce_info}. -@end defmac - -@defmac IFCVT_MACHDEP_INIT (@var{ce_info}) -A C expression to initialize any machine specific data for if-conversion -of the if-block in the @code{struct ce_if_block} structure that is pointed -to by @var{ce_info}. -@end defmac - -@deftypefn {Target Hook} void TARGET_MACHINE_DEPENDENT_REORG (void) -If non-null, this hook performs a target-specific pass over the -instruction stream. The compiler will run it at all optimization levels, -just before the point at which it normally does delayed-branch scheduling. - -The exact purpose of the hook varies from target to target. Some use -it to do transformations that are necessary for correctness, such as -laying out in-function constant pools or avoiding hardware hazards. -Others use it as an opportunity to do some machine-dependent optimizations. - -You need not implement the hook if it has nothing to do. The default -definition is null. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_INIT_BUILTINS (void) -Define this hook if you have any machine-specific built-in functions -that need to be defined. It should be a function that performs the -necessary setup. - -Machine specific built-in functions can be useful to expand special machine -instructions that would otherwise not normally be generated because -they have no equivalent in the source language (for example, SIMD vector -instructions or prefetch instructions). - -To create a built-in function, call the function -@code{lang_hooks.builtin_function} -which is defined by the language front end. You can use any type nodes set -up by @code{build_common_tree_nodes}; -only language front ends that use those two functions will call -@samp{TARGET_INIT_BUILTINS}. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_BUILTIN_DECL (unsigned @var{code}, bool @var{initialize_p}) -Define this hook if you have any machine-specific built-in functions -that need to be defined. It should be a function that returns the -builtin function declaration for the builtin function code @var{code}. -If there is no such builtin and it cannot be initialized at this time -if @var{initialize_p} is true the function should return @code{NULL_TREE}. -If @var{code} is out of range the function should return -@code{error_mark_node}. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_EXPAND_BUILTIN (tree @var{exp}, rtx @var{target}, rtx @var{subtarget}, machine_mode @var{mode}, int @var{ignore}) - -Expand a call to a machine specific built-in function that was set up by -@samp{TARGET_INIT_BUILTINS}. @var{exp} is the expression for the -function call; the result should go to @var{target} if that is -convenient, and have mode @var{mode} if that is convenient. -@var{subtarget} may be used as the target for computing one of -@var{exp}'s operands. @var{ignore} is nonzero if the value is to be -ignored. This function should return the result of the call to the -built-in function. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_RESOLVE_OVERLOADED_BUILTIN (unsigned int @var{loc}, tree @var{fndecl}, void *@var{arglist}) -Select a replacement for a machine specific built-in function that -was set up by @samp{TARGET_INIT_BUILTINS}. This is done -@emph{before} regular type checking, and so allows the target to -implement a crude form of function overloading. @var{fndecl} is the -declaration of the built-in function. @var{arglist} is the list of -arguments passed to the built-in function. The result is a -complete expression that implements the operation, usually -another @code{CALL_EXPR}. -@var{arglist} really has type @samp{VEC(tree,gc)*} -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CHECK_BUILTIN_CALL (location_t @var{loc}, vec<location_t> @var{arg_loc}, tree @var{fndecl}, tree @var{orig_fndecl}, unsigned int @var{nargs}, tree *@var{args}) -Perform semantic checking on a call to a machine-specific built-in -function after its arguments have been constrained to the function -signature. Return true if the call is valid, otherwise report an error -and return false. - -This hook is called after @code{TARGET_RESOLVE_OVERLOADED_BUILTIN}. -The call was originally to built-in function @var{orig_fndecl}, -but after the optional @code{TARGET_RESOLVE_OVERLOADED_BUILTIN} -step is now to built-in function @var{fndecl}. @var{loc} is the -location of the call and @var{args} is an array of function arguments, -of which there are @var{nargs}. @var{arg_loc} specifies the location -of each argument. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_FOLD_BUILTIN (tree @var{fndecl}, int @var{n_args}, tree *@var{argp}, bool @var{ignore}) -Fold a call to a machine specific built-in function that was set up by -@samp{TARGET_INIT_BUILTINS}. @var{fndecl} is the declaration of the -built-in function. @var{n_args} is the number of arguments passed to -the function; the arguments themselves are pointed to by @var{argp}. -The result is another tree, valid for both GIMPLE and GENERIC, -containing a simplified expression for the call's result. If -@var{ignore} is true the value will be ignored. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_GIMPLE_FOLD_BUILTIN (gimple_stmt_iterator *@var{gsi}) -Fold a call to a machine specific built-in function that was set up -by @samp{TARGET_INIT_BUILTINS}. @var{gsi} points to the gimple -statement holding the function call. Returns true if any change -was made to the GIMPLE stream. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_COMPARE_VERSION_PRIORITY (tree @var{decl1}, tree @var{decl2}) -This hook is used to compare the target attributes in two functions to -determine which function's features get higher priority. This is used -during function multi-versioning to figure out the order in which two -versions must be dispatched. A function version with a higher priority -is checked for dispatching earlier. @var{decl1} and @var{decl2} are - the two function decls that will be compared. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_GET_FUNCTION_VERSIONS_DISPATCHER (void *@var{decl}) -This hook is used to get the dispatcher function for a set of function -versions. The dispatcher function is called to invoke the right function -version at run-time. @var{decl} is one version from a set of semantically -identical versions. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_GENERATE_VERSION_DISPATCHER_BODY (void *@var{arg}) -This hook is used to generate the dispatcher logic to invoke the right -function version at run-time for a given set of function versions. -@var{arg} points to the callgraph node of the dispatcher function whose -body must be generated. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_PREDICT_DOLOOP_P (class loop *@var{loop}) -Return true if we can predict it is possible to use a low-overhead loop -for a particular loop. The parameter @var{loop} is a pointer to the loop. -This target hook is required only when the target supports low-overhead -loops, and will help ivopts to make some decisions. -The default version of this hook returns false. -@end deftypefn - -@deftypevr {Target Hook} bool TARGET_HAVE_COUNT_REG_DECR_P -Return true if the target supports hardware count register for decrement -and branch. -The default value is false. -@end deftypevr - -@deftypevr {Target Hook} int64_t TARGET_DOLOOP_COST_FOR_GENERIC -One IV candidate dedicated for doloop is introduced in IVOPTs, we can -calculate the computation cost of adopting it to any generic IV use by -function get_computation_cost as before. But for targets which have -hardware count register support for decrement and branch, it may have to -move IV value from hardware count register to general purpose register -while doloop IV candidate is used for generic IV uses. It probably takes -expensive penalty. This hook allows target owners to define the cost for -this especially for generic IV uses. -The default value is zero. -@end deftypevr - -@deftypevr {Target Hook} int64_t TARGET_DOLOOP_COST_FOR_ADDRESS -One IV candidate dedicated for doloop is introduced in IVOPTs, we can -calculate the computation cost of adopting it to any address IV use by -function get_computation_cost as before. But for targets which have -hardware count register support for decrement and branch, it may have to -move IV value from hardware count register to general purpose register -while doloop IV candidate is used for address IV uses. It probably takes -expensive penalty. This hook allows target owners to define the cost for -this escpecially for address IV uses. -The default value is zero. -@end deftypevr - -@deftypefn {Target Hook} bool TARGET_CAN_USE_DOLOOP_P (const widest_int @var{&iterations}, const widest_int @var{&iterations_max}, unsigned int @var{loop_depth}, bool @var{entered_at_top}) -Return true if it is possible to use low-overhead loops (@code{doloop_end} -and @code{doloop_begin}) for a particular loop. @var{iterations} gives the -exact number of iterations, or 0 if not known. @var{iterations_max} gives -the maximum number of iterations, or 0 if not known. @var{loop_depth} is -the nesting depth of the loop, with 1 for innermost loops, 2 for loops that -contain innermost loops, and so on. @var{entered_at_top} is true if the -loop is only entered from the top. - -This hook is only used if @code{doloop_end} is available. The default -implementation returns true. You can use @code{can_use_doloop_if_innermost} -if the loop must be the innermost, and if there are no other restrictions. -@end deftypefn - -@deftypefn {Target Hook} {const char *} TARGET_INVALID_WITHIN_DOLOOP (const rtx_insn *@var{insn}) - -Take an instruction in @var{insn} and return NULL if it is valid within a -low-overhead loop, otherwise return a string explaining why doloop -could not be applied. - -Many targets use special registers for low-overhead looping. For any -instruction that clobbers these this function should return a string indicating -the reason why the doloop could not be applied. -By default, the RTL loop optimizer does not use a present doloop pattern for -loops containing function calls or branch on table instructions. -@end deftypefn - -@deftypefn {Target Hook} machine_mode TARGET_PREFERRED_DOLOOP_MODE (machine_mode @var{mode}) -This hook takes a @var{mode} for a doloop IV, where @code{mode} is the -original mode for the operation. If the target prefers an alternate -@code{mode} for the operation, then this hook should return that mode; -otherwise the original @code{mode} should be returned. For example, on a -64-bit target, @code{DImode} might be preferred over @code{SImode}. Both the -original and the returned modes should be @code{MODE_INT}. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_LEGITIMATE_COMBINED_INSN (rtx_insn *@var{insn}) -Take an instruction in @var{insn} and return @code{false} if the instruction -is not appropriate as a combination of two or more instructions. The -default is to accept all instructions. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_CAN_FOLLOW_JUMP (const rtx_insn *@var{follower}, const rtx_insn *@var{followee}) -FOLLOWER and FOLLOWEE are JUMP_INSN instructions; -return true if FOLLOWER may be modified to follow FOLLOWEE; -false, if it can't. -For example, on some targets, certain kinds of branches can't be made to -follow through a hot/cold partitioning. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_COMMUTATIVE_P (const_rtx @var{x}, int @var{outer_code}) -This target hook returns @code{true} if @var{x} is considered to be commutative. -Usually, this is just COMMUTATIVE_P (@var{x}), but the HP PA doesn't consider -PLUS to be commutative inside a MEM@. @var{outer_code} is the rtx code -of the enclosing rtl, if known, otherwise it is UNKNOWN. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_ALLOCATE_INITIAL_VALUE (rtx @var{hard_reg}) - -When the initial value of a hard register has been copied in a pseudo -register, it is often not necessary to actually allocate another register -to this pseudo register, because the original hard register or a stack slot -it has been saved into can be used. @code{TARGET_ALLOCATE_INITIAL_VALUE} -is called at the start of register allocation once for each hard register -that had its initial value copied by using -@code{get_func_hard_reg_initial_val} or @code{get_hard_reg_initial_val}. -Possible values are @code{NULL_RTX}, if you don't want -to do any special allocation, a @code{REG} rtx---that would typically be -the hard register itself, if it is known not to be clobbered---or a -@code{MEM}. -If you are returning a @code{MEM}, this is only a hint for the allocator; -it might decide to use another register anyways. -You may use @code{current_function_is_leaf} or -@code{REG_N_SETS} in the hook to determine if the hard -register in question will not be clobbered. -The default value of this hook is @code{NULL}, which disables any special -allocation. -@end deftypefn - -@deftypefn {Target Hook} int TARGET_UNSPEC_MAY_TRAP_P (const_rtx @var{x}, unsigned @var{flags}) -This target hook returns nonzero if @var{x}, an @code{unspec} or -@code{unspec_volatile} operation, might cause a trap. Targets can use -this hook to enhance precision of analysis for @code{unspec} and -@code{unspec_volatile} operations. You may call @code{may_trap_p_1} -to analyze inner elements of @var{x} in which case @var{flags} should be -passed along. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_SET_CURRENT_FUNCTION (tree @var{decl}) -The compiler invokes this hook whenever it changes its current function -context (@code{cfun}). You can define this function if -the back end needs to perform any initialization or reset actions on a -per-function basis. For example, it may be used to implement function -attributes that affect register usage or code generation patterns. -The argument @var{decl} is the declaration for the new function context, -and may be null to indicate that the compiler has left a function context -and is returning to processing at the top level. -The default hook function does nothing. - -GCC sets @code{cfun} to a dummy function context during initialization of -some parts of the back end. The hook function is not invoked in this -situation; you need not worry about the hook being invoked recursively, -or when the back end is in a partially-initialized state. -@code{cfun} might be @code{NULL} to indicate processing at top level, -outside of any function scope. -@end deftypefn - -@defmac TARGET_OBJECT_SUFFIX -Define this macro to be a C string representing the suffix for object -files on your target machine. If you do not define this macro, GCC will -use @samp{.o} as the suffix for object files. -@end defmac - -@defmac TARGET_EXECUTABLE_SUFFIX -Define this macro to be a C string representing the suffix to be -automatically added to executable files on your target machine. If you -do not define this macro, GCC will use the null string as the suffix for -executable files. -@end defmac - -@defmac COLLECT_EXPORT_LIST -If defined, @code{collect2} will scan the individual object files -specified on its command line and create an export list for the linker. -Define this macro for systems like AIX, where the linker discards -object files that are not referenced from @code{main} and uses export -lists. -@end defmac - -@deftypefn {Target Hook} bool TARGET_CANNOT_MODIFY_JUMPS_P (void) -This target hook returns @code{true} past the point in which new jump -instructions could be created. On machines that require a register for -every jump such as the SHmedia ISA of SH5, this point would typically be -reload, so this target hook should be defined to a function such as: - -@smallexample -static bool -cannot_modify_jumps_past_reload_p () -@{ - return (reload_completed || reload_in_progress); -@} -@end smallexample -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_HAVE_CONDITIONAL_EXECUTION (void) -This target hook returns true if the target supports conditional execution. -This target hook is required only when the target has several different -modes and they have different conditional execution capability, such as ARM. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_GEN_CCMP_FIRST (rtx_insn **@var{prep_seq}, rtx_insn **@var{gen_seq}, int @var{code}, tree @var{op0}, tree @var{op1}) -This function prepares to emit a comparison insn for the first compare in a - sequence of conditional comparisions. It returns an appropriate comparison - with @code{CC} for passing to @code{gen_ccmp_next} or @code{cbranch_optab}. - The insns to prepare the compare are saved in @var{prep_seq} and the compare - insns are saved in @var{gen_seq}. They will be emitted when all the - compares in the conditional comparision are generated without error. - @var{code} is the @code{rtx_code} of the compare for @var{op0} and @var{op1}. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_GEN_CCMP_NEXT (rtx_insn **@var{prep_seq}, rtx_insn **@var{gen_seq}, rtx @var{prev}, int @var{cmp_code}, tree @var{op0}, tree @var{op1}, int @var{bit_code}) -This function prepares to emit a conditional comparison within a sequence - of conditional comparisons. It returns an appropriate comparison with - @code{CC} for passing to @code{gen_ccmp_next} or @code{cbranch_optab}. - The insns to prepare the compare are saved in @var{prep_seq} and the compare - insns are saved in @var{gen_seq}. They will be emitted when all the - compares in the conditional comparision are generated without error. The - @var{prev} expression is the result of a prior call to @code{gen_ccmp_first} - or @code{gen_ccmp_next}. It may return @code{NULL} if the combination of - @var{prev} and this comparison is not supported, otherwise the result must - be appropriate for passing to @code{gen_ccmp_next} or @code{cbranch_optab}. - @var{code} is the @code{rtx_code} of the compare for @var{op0} and @var{op1}. - @var{bit_code} is @code{AND} or @code{IOR}, which is the op on the compares. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_GEN_MEMSET_SCRATCH_RTX (machine_mode @var{mode}) -This hook should return an rtx for a scratch register in @var{mode} to -be used when expanding memset calls. The backend can use a hard scratch -register to avoid stack realignment when expanding memset. The default -is @code{gen_reg_rtx}. -@end deftypefn - -@deftypefn {Target Hook} unsigned TARGET_LOOP_UNROLL_ADJUST (unsigned @var{nunroll}, class loop *@var{loop}) -This target hook returns a new value for the number of times @var{loop} -should be unrolled. The parameter @var{nunroll} is the number of times -the loop is to be unrolled. The parameter @var{loop} is a pointer to -the loop, which is going to be checked for unrolling. This target hook -is required only when the target has special constraints like maximum -number of memory accesses. -@end deftypefn - -@defmac POWI_MAX_MULTS -If defined, this macro is interpreted as a signed integer C expression -that specifies the maximum number of floating point multiplications -that should be emitted when expanding exponentiation by an integer -constant inline. When this value is defined, exponentiation requiring -more than this number of multiplications is implemented by calling the -system library's @code{pow}, @code{powf} or @code{powl} routines. -The default value places no upper bound on the multiplication count. -@end defmac - -@deftypefn Macro void TARGET_EXTRA_INCLUDES (const char *@var{sysroot}, const char *@var{iprefix}, int @var{stdinc}) -This target hook should register any extra include files for the -target. The parameter @var{stdinc} indicates if normal include files -are present. The parameter @var{sysroot} is the system root directory. -The parameter @var{iprefix} is the prefix for the gcc directory. -@end deftypefn - -@deftypefn Macro void TARGET_EXTRA_PRE_INCLUDES (const char *@var{sysroot}, const char *@var{iprefix}, int @var{stdinc}) -This target hook should register any extra include files for the -target before any standard headers. The parameter @var{stdinc} -indicates if normal include files are present. The parameter -@var{sysroot} is the system root directory. The parameter -@var{iprefix} is the prefix for the gcc directory. -@end deftypefn - -@deftypefn Macro void TARGET_OPTF (char *@var{path}) -This target hook should register special include paths for the target. -The parameter @var{path} is the include to register. On Darwin -systems, this is used for Framework includes, which have semantics -that are different from @option{-I}. -@end deftypefn - -@defmac bool TARGET_USE_LOCAL_THUNK_ALIAS_P (tree @var{fndecl}) -This target macro returns @code{true} if it is safe to use a local alias -for a virtual function @var{fndecl} when constructing thunks, -@code{false} otherwise. By default, the macro returns @code{true} for all -functions, if a target supports aliases (i.e.@: defines -@code{ASM_OUTPUT_DEF}), @code{false} otherwise, -@end defmac - -@defmac TARGET_FORMAT_TYPES -If defined, this macro is the name of a global variable containing -target-specific format checking information for the @option{-Wformat} -option. The default is to have no target-specific format checks. -@end defmac - -@defmac TARGET_N_FORMAT_TYPES -If defined, this macro is the number of entries in -@code{TARGET_FORMAT_TYPES}. -@end defmac - -@defmac TARGET_OVERRIDES_FORMAT_ATTRIBUTES -If defined, this macro is the name of a global variable containing -target-specific format overrides for the @option{-Wformat} option. The -default is to have no target-specific format overrides. If defined, -@code{TARGET_FORMAT_TYPES} and @code{TARGET_OVERRIDES_FORMAT_ATTRIBUTES_COUNT} -must be defined, too. -@end defmac - -@defmac TARGET_OVERRIDES_FORMAT_ATTRIBUTES_COUNT -If defined, this macro specifies the number of entries in -@code{TARGET_OVERRIDES_FORMAT_ATTRIBUTES}. -@end defmac - -@defmac TARGET_OVERRIDES_FORMAT_INIT -If defined, this macro specifies the optional initialization -routine for target specific customizations of the system printf -and scanf formatter settings. -@end defmac - -@deftypefn {Target Hook} {const char *} TARGET_INVALID_ARG_FOR_UNPROTOTYPED_FN (const_tree @var{typelist}, const_tree @var{funcdecl}, const_tree @var{val}) -If defined, this macro returns the diagnostic message when it is -illegal to pass argument @var{val} to function @var{funcdecl} -with prototype @var{typelist}. -@end deftypefn - -@deftypefn {Target Hook} {const char *} TARGET_INVALID_CONVERSION (const_tree @var{fromtype}, const_tree @var{totype}) -If defined, this macro returns the diagnostic message when it is -invalid to convert from @var{fromtype} to @var{totype}, or @code{NULL} -if validity should be determined by the front end. -@end deftypefn - -@deftypefn {Target Hook} {const char *} TARGET_INVALID_UNARY_OP (int @var{op}, const_tree @var{type}) -If defined, this macro returns the diagnostic message when it is -invalid to apply operation @var{op} (where unary plus is denoted by -@code{CONVERT_EXPR}) to an operand of type @var{type}, or @code{NULL} -if validity should be determined by the front end. -@end deftypefn - -@deftypefn {Target Hook} {const char *} TARGET_INVALID_BINARY_OP (int @var{op}, const_tree @var{type1}, const_tree @var{type2}) -If defined, this macro returns the diagnostic message when it is -invalid to apply operation @var{op} to operands of types @var{type1} -and @var{type2}, or @code{NULL} if validity should be determined by -the front end. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_PROMOTED_TYPE (const_tree @var{type}) -If defined, this target hook returns the type to which values of -@var{type} should be promoted when they appear in expressions, -analogous to the integer promotions, or @code{NULL_TREE} to use the -front end's normal promotion rules. This hook is useful when there are -target-specific types with special promotion rules. -This is currently used only by the C and C++ front ends. -@end deftypefn - -@deftypefn {Target Hook} tree TARGET_CONVERT_TO_TYPE (tree @var{type}, tree @var{expr}) -If defined, this hook returns the result of converting @var{expr} to -@var{type}. It should return the converted expression, -or @code{NULL_TREE} to apply the front end's normal conversion rules. -This hook is useful when there are target-specific types with special -conversion rules. -This is currently used only by the C and C++ front ends. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_VERIFY_TYPE_CONTEXT (location_t @var{loc}, type_context_kind @var{context}, const_tree @var{type}, bool @var{silent_p}) -If defined, this hook returns false if there is a target-specific reason -why type @var{type} cannot be used in the source language context described -by @var{context}. When @var{silent_p} is false, the hook also reports an -error against @var{loc} for invalid uses of @var{type}. - -Calls to this hook should be made through the global function -@code{verify_type_context}, which makes the @var{silent_p} parameter -default to false and also handles @code{error_mark_node}. - -The default implementation always returns true. -@end deftypefn - -@defmac OBJC_JBLEN -This macro determines the size of the objective C jump buffer for the -NeXT runtime. By default, OBJC_JBLEN is defined to an innocuous value. -@end defmac - -@defmac LIBGCC2_UNWIND_ATTRIBUTE -Define this macro if any target-specific attributes need to be attached -to the functions in @file{libgcc} that provide low-level support for -call stack unwinding. It is used in declarations in @file{unwind-generic.h} -and the associated definitions of those functions. -@end defmac - -@deftypefn {Target Hook} void TARGET_UPDATE_STACK_BOUNDARY (void) -Define this macro to update the current function stack boundary if -necessary. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_GET_DRAP_RTX (void) -This hook should return an rtx for Dynamic Realign Argument Pointer (DRAP) if a -different argument pointer register is needed to access the function's -argument list due to stack realignment. Return @code{NULL} if no DRAP -is needed. -@end deftypefn - -@deftypefn {Target Hook} HARD_REG_SET TARGET_ZERO_CALL_USED_REGS (HARD_REG_SET @var{selected_regs}) -This target hook emits instructions to zero the subset of @var{selected_regs} -that could conceivably contain values that are useful to an attacker. -Return the set of registers that were actually cleared. - -For most targets, the returned set of registers is a subset of -@var{selected_regs}, however, for some of the targets (for example MIPS), -clearing some registers that are in the @var{selected_regs} requires -clearing other call used registers that are not in the @var{selected_regs}, -under such situation, the returned set of registers must be a subset of all -call used registers. - -The default implementation uses normal move instructions to zero -all the registers in @var{selected_regs}. Define this hook if the -target has more efficient ways of zeroing certain registers, -or if you believe that certain registers would never contain -values that are useful to an attacker. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS (void) -When optimization is disabled, this hook indicates whether or not -arguments should be allocated to stack slots. Normally, GCC allocates -stacks slots for arguments when not optimizing in order to make -debugging easier. However, when a function is declared with -@code{__attribute__((naked))}, there is no stack frame, and the compiler -cannot safely move arguments from the registers in which they are passed -to the stack. Therefore, this hook should return true in general, but -false for naked functions. The default implementation always returns true. -@end deftypefn - -@deftypevr {Target Hook} {unsigned HOST_WIDE_INT} TARGET_CONST_ANCHOR -On some architectures it can take multiple instructions to synthesize -a constant. If there is another constant already in a register that -is close enough in value then it is preferable that the new constant -is computed from this register using immediate addition or -subtraction. We accomplish this through CSE. Besides the value of -the constant we also add a lower and an upper constant anchor to the -available expressions. These are then queried when encountering new -constants. The anchors are computed by rounding the constant up and -down to a multiple of the value of @code{TARGET_CONST_ANCHOR}. -@code{TARGET_CONST_ANCHOR} should be the maximum positive value -accepted by immediate-add plus one. We currently assume that the -value of @code{TARGET_CONST_ANCHOR} is a power of 2. For example, on -MIPS, where add-immediate takes a 16-bit signed value, -@code{TARGET_CONST_ANCHOR} is set to @samp{0x8000}. The default value -is zero, which disables this optimization. -@end deftypevr - -@deftypefn {Target Hook} {unsigned HOST_WIDE_INT} TARGET_ASAN_SHADOW_OFFSET (void) -Return the offset bitwise ored into shifted address to get corresponding -Address Sanitizer shadow memory address. NULL if Address Sanitizer is not -supported by the target. May return 0 if Address Sanitizer is not supported -by a subtarget. -@end deftypefn - -@deftypefn {Target Hook} {unsigned HOST_WIDE_INT} TARGET_MEMMODEL_CHECK (unsigned HOST_WIDE_INT @var{val}) -Validate target specific memory model mask bits. When NULL no target specific -memory model bits are allowed. -@end deftypefn - -@deftypevr {Target Hook} {unsigned char} TARGET_ATOMIC_TEST_AND_SET_TRUEVAL -This value should be set if the result written by -@code{atomic_test_and_set} is not exactly 1, i.e.@: the -@code{bool} @code{true}. -@end deftypevr - -@deftypefn {Target Hook} bool TARGET_HAS_IFUNC_P (void) -It returns true if the target supports GNU indirect functions. -The support includes the assembler, linker and dynamic linker. -The default value of this hook is based on target's libc. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_IFUNC_REF_LOCAL_OK (void) -Return true if it is OK to reference indirect function resolvers -locally. The default is to return false. -@end deftypefn - -@deftypefn {Target Hook} {unsigned int} TARGET_ATOMIC_ALIGN_FOR_MODE (machine_mode @var{mode}) -If defined, this function returns an appropriate alignment in bits for an -atomic object of machine_mode @var{mode}. If 0 is returned then the -default alignment for the specified mode is used. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ATOMIC_ASSIGN_EXPAND_FENV (tree *@var{hold}, tree *@var{clear}, tree *@var{update}) -ISO C11 requires atomic compound assignments that may raise floating-point -exceptions to raise exceptions corresponding to the arithmetic operation -whose result was successfully stored in a compare-and-exchange sequence. -This requires code equivalent to calls to @code{feholdexcept}, -@code{feclearexcept} and @code{feupdateenv} to be generated at -appropriate points in the compare-and-exchange sequence. This hook should -set @code{*@var{hold}} to an expression equivalent to the call to -@code{feholdexcept}, @code{*@var{clear}} to an expression equivalent to -the call to @code{feclearexcept} and @code{*@var{update}} to an expression -equivalent to the call to @code{feupdateenv}. The three expressions are -@code{NULL_TREE} on entry to the hook and may be left as @code{NULL_TREE} -if no code is required in a particular place. The default implementation -leaves all three expressions as @code{NULL_TREE}. The -@code{__atomic_feraiseexcept} function from @code{libatomic} may be of use -as part of the code generated in @code{*@var{update}}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_RECORD_OFFLOAD_SYMBOL (tree) -Used when offloaded functions are seen in the compilation unit and no named -sections are available. It is called once for each symbol that must be -recorded in the offload function and variable table. -@end deftypefn - -@deftypefn {Target Hook} {char *} TARGET_OFFLOAD_OPTIONS (void) -Used when writing out the list of options into an LTO file. It should -translate any relevant target-specific options (such as the ABI in use) -into one of the @option{-foffload} options that exist as a common interface -to express such options. It should return a string containing these options, -separated by spaces, which the caller will free. - -@end deftypefn - -@defmac TARGET_SUPPORTS_WIDE_INT - -On older ports, large integers are stored in @code{CONST_DOUBLE} rtl -objects. Newer ports define @code{TARGET_SUPPORTS_WIDE_INT} to be nonzero -to indicate that large integers are stored in -@code{CONST_WIDE_INT} rtl objects. The @code{CONST_WIDE_INT} allows -very large integer constants to be represented. @code{CONST_DOUBLE} -is limited to twice the size of the host's @code{HOST_WIDE_INT} -representation. - -Converting a port mostly requires looking for the places where -@code{CONST_DOUBLE}s are used with @code{VOIDmode} and replacing that -code with code that accesses @code{CONST_WIDE_INT}s. @samp{"grep -i -const_double"} at the port level gets you to 95% of the changes that -need to be made. There are a few places that require a deeper look. - -@itemize @bullet -@item -There is no equivalent to @code{hval} and @code{lval} for -@code{CONST_WIDE_INT}s. This would be difficult to express in the md -language since there are a variable number of elements. - -Most ports only check that @code{hval} is either 0 or -1 to see if the -value is small. As mentioned above, this will no longer be necessary -since small constants are always @code{CONST_INT}. Of course there -are still a few exceptions, the alpha's constraint used by the zap -instruction certainly requires careful examination by C code. -However, all the current code does is pass the hval and lval to C -code, so evolving the c code to look at the @code{CONST_WIDE_INT} is -not really a large change. - -@item -Because there is no standard template that ports use to materialize -constants, there is likely to be some futzing that is unique to each -port in this code. - -@item -The rtx costs may have to be adjusted to properly account for larger -constants that are represented as @code{CONST_WIDE_INT}. -@end itemize - -All and all it does not take long to convert ports that the -maintainer is familiar with. - -@end defmac - -@deftypefn {Target Hook} bool TARGET_HAVE_SPECULATION_SAFE_VALUE (bool @var{active}) -This hook is used to determine the level of target support for - @code{__builtin_speculation_safe_value}. If called with an argument - of false, it returns true if the target has been modified to support - this builtin. If called with an argument of true, it returns true - if the target requires active mitigation execution might be speculative. - - The default implementation returns false if the target does not define - a pattern named @code{speculation_barrier}. Else it returns true - for the first case and whether the pattern is enabled for the current - compilation for the second case. - - For targets that have no processors that can execute instructions - speculatively an alternative implemenation of this hook is available: - simply redefine this hook to @code{speculation_safe_value_not_needed} - along with your other target hooks. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_SPECULATION_SAFE_VALUE (machine_mode @var{mode}, rtx @var{result}, rtx @var{val}, rtx @var{failval}) -This target hook can be used to generate a target-specific code - sequence that implements the @code{__builtin_speculation_safe_value} - built-in function. The function must always return @var{val} in - @var{result} in mode @var{mode} when the cpu is not executing - speculatively, but must never return that when speculating until it - is known that the speculation will not be unwound. The hook supports - two primary mechanisms for implementing the requirements. The first - is to emit a speculation barrier which forces the processor to wait - until all prior speculative operations have been resolved; the second - is to use a target-specific mechanism that can track the speculation - state and to return @var{failval} if it can determine that - speculation must be unwound at a later time. - - The default implementation simply copies @var{val} to @var{result} and - emits a @code{speculation_barrier} instruction if that is defined. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_RUN_TARGET_SELFTESTS (void) -If selftests are enabled, run any selftests for this target. -@end deftypefn - -@deftypefn {Target Hook} bool TARGET_MEMTAG_CAN_TAG_ADDRESSES () -True if the backend architecture naturally supports ignoring some region -of pointers. This feature means that @option{-fsanitize=hwaddress} can -work. - -At preset, this feature does not support address spaces. It also requires -@code{Pmode} to be the same as @code{ptr_mode}. -@end deftypefn - -@deftypefn {Target Hook} uint8_t TARGET_MEMTAG_TAG_SIZE () -Return the size of a tag (in bits) for this platform. - -The default returns 8. -@end deftypefn - -@deftypefn {Target Hook} uint8_t TARGET_MEMTAG_GRANULE_SIZE () -Return the size in real memory that each byte in shadow memory refers to. -I.e. if a variable is @var{X} bytes long in memory, then this hook should -return the value @var{Y} such that the tag in shadow memory spans -@var{X}/@var{Y} bytes. - -Most variables will need to be aligned to this amount since two variables -that are neighbors in memory and share a tag granule would need to share -the same tag. - -The default returns 16. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_MEMTAG_INSERT_RANDOM_TAG (rtx @var{untagged}, rtx @var{target}) -Return an RTX representing the value of @var{untagged} but with a -(possibly) random tag in it. -Put that value into @var{target} if it is convenient to do so. -This function is used to generate a tagged base for the current stack frame. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_MEMTAG_ADD_TAG (rtx @var{base}, poly_int64 @var{addr_offset}, uint8_t @var{tag_offset}) -Return an RTX that represents the result of adding @var{addr_offset} to -the address in pointer @var{base} and @var{tag_offset} to the tag in pointer -@var{base}. -The resulting RTX must either be a valid memory address or be able to get -put into an operand with @code{force_operand}. - -Unlike other memtag hooks, this must return an expression and not emit any -RTL. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_MEMTAG_SET_TAG (rtx @var{untagged_base}, rtx @var{tag}, rtx @var{target}) -Return an RTX representing @var{untagged_base} but with the tag @var{tag}. -Try and store this in @var{target} if convenient. -@var{untagged_base} is required to have a zero tag when this hook is called. -The default of this hook is to set the top byte of @var{untagged_base} to -@var{tag}. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_MEMTAG_EXTRACT_TAG (rtx @var{tagged_pointer}, rtx @var{target}) -Return an RTX representing the tag stored in @var{tagged_pointer}. -Store the result in @var{target} if it is convenient. -The default represents the top byte of the original pointer. -@end deftypefn - -@deftypefn {Target Hook} rtx TARGET_MEMTAG_UNTAGGED_POINTER (rtx @var{tagged_pointer}, rtx @var{target}) -Return an RTX representing @var{tagged_pointer} with its tag set to zero. -Store the result in @var{target} if convenient. -The default clears the top byte of the original pointer. -@end deftypefn - -@deftypefn {Target Hook} HOST_WIDE_INT TARGET_GCOV_TYPE_SIZE (void) -Returns the gcov type size in bits. This type is used for example for -counters incremented by profiling and code-coverage events. The default -value is 64, if the type size of long long is greater than 32, otherwise the -default value is 32. A 64-bit type is recommended to avoid overflows of the -counters. If the @option{-fprofile-update=atomic} is used, then the -counters are incremented using atomic operations. Targets not supporting -64-bit atomic operations may override the default value and request a 32-bit -type. -@end deftypefn - -@deftypevr {Target Hook} bool TARGET_HAVE_SHADOW_CALL_STACK -This value is true if the target platform supports -@option{-fsanitize=shadow-call-stack}. The default value is false. -@end deftypevr |