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Diffstat (limited to 'gcc/doc/extend.texi')
| -rw-r--r-- | gcc/doc/extend.texi | 83 |
1 files changed, 52 insertions, 31 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index 7427825..616e05e 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -31,7 +31,6 @@ extensions, accepted by GCC in C90 mode and in C++. * Thread-Local:: Per-thread variables. * OpenMP:: Multiprocessing extensions. * OpenACC:: Extensions for offloading code to accelerator devices. -* _Countof:: The number of elements of arrays. * Inline:: Defining inline functions (as fast as macros). * Volatiles:: What constitutes an access to a volatile object. * Using Assembly Language with C:: Instructions and extensions for interfacing C with assembler. @@ -3971,6 +3970,27 @@ threads, such as the POSIX @code{swapcontext} function. This attribute adds a @code{BTI J} instruction when BTI is enabled e.g. via @option{-mbranch-protection}. +@cindex @code{preserve_none} function attribute, AArch64 +@item preserve_none +Use this attribute to change the procedure call standard of the specified +function to the preserve-none variant. + +The preserve-none ABI variant modifies the AAPCS such that has no callee-saved +registers (including SIMD and floating-point registers). That is, with the +exception of the stack register, link register (r30), and frame pointer (r29), +all registers are caller saved, and can be used as scratch registers by the +callee. + +Additionally, registers r20--r28, r0--r7, r10--r14, r9 and r15 are used for +argument passing, in that order. For Microsoft Windows targets +r15 is not used for argument passing. + +The return value registers remain r0 and r1 in both cases. + +All other details are the same as for the AAPCS ABI. + +This ABI has not been stabilized, and may be subject to change in future +versions. @end table The above target attributes can be specified as follows: @@ -10890,36 +10910,6 @@ library. @xref{OpenMP and OpenACC Options}, for additional options useful with @option{-fopenacc}. -@node _Countof -@section Determining the Number of Elements of Arrays -@cindex _Countof -@cindex number of elements - -The keyword @code{_Countof} determines -the number of elements of an array operand. -Its syntax is similar to @code{sizeof}. -The operand must be -a parenthesized complete array type name -or an expression of such a type. -For example: - -@smallexample -int a[n]; -_Countof (a); // returns n -_Countof (int [7][3]); // returns 7 -@end smallexample - -The result of this operator is an integer constant expression, -unless the array has a variable number of elements. -The operand is only evaluated -if the array has a variable number of elements. -For example: - -@smallexample -_Countof (int [7][n++]); // integer constant expression -_Countof (int [n++][7]); // run-time value; n++ is evaluated -@end smallexample - @node Inline @section An Inline Function is As Fast As a Macro @cindex inline functions @@ -13341,6 +13331,7 @@ C and/or C++ standards, while others remain specific to GNU C. * Labels as Values:: Getting pointers to labels, and computed gotos. * Nested Functions:: Nested functions in GNU C. * Typeof:: @code{typeof}: referring to the type of an expression. +* _Countof:: Determining the number of elements of arrays * Offsetof:: Special syntax for @code{offsetof}. * Alignment:: Determining the alignment of a function, type or variable. * Enum Extensions:: Forward declarations and specifying the underlying type. @@ -13977,6 +13968,36 @@ evaluated only once when using @code{__auto_type}, but twice if @code{typeof} is used. @end itemize +@node _Countof +@subsection Determining the Number of Elements of Arrays +@findex _Countof +@findex number of elements + +The keyword @code{_Countof} determines +the number of elements of an array operand. +Its syntax is similar to @code{sizeof}. +The operand must be +a parenthesized complete array type name +or an expression of such a type. +For example: + +@smallexample +int a[n]; +_Countof (a); // returns n +_Countof (int [7][3]); // returns 7 +@end smallexample + +The result of this operator is an integer constant expression, +unless the array has a variable number of elements. +The operand is only evaluated +if the array has a variable number of elements. +For example: + +@smallexample +_Countof (int [7][n++]); // integer constant expression +_Countof (int [n++][7]); // run-time value; n++ is evaluated +@end smallexample + @node Offsetof @subsection Support for @code{offsetof} @findex __builtin_offsetof |