re PR ada/37139 (DEP prevents using Ada tasking)

	PR ada/37139
	PR ada/67205
	* common.opt (-ftrampolines): New option.
	* doc/invoke.texi (Code Gen Options): Document it.
	* doc/tm.texi.in (Trampolines): Add TARGET_CUSTOM_FUNCTION_DESCRIPTORS.
	* doc/tm.texi: Regenerate.
	* builtins.def: Add init_descriptor and adjust_descriptor.
	* builtins.c (expand_builtin_init_trampoline): Do not issue a warning
	on platforms with descriptors.
	(expand_builtin_init_descriptor): New function.
	(expand_builtin_adjust_descriptor): Likewise.
	(expand_builtin) <BUILT_IN_INIT_DESCRIPTOR>: New case.
	<BUILT_IN_ADJUST_DESCRIPTOR>: Likewise.
	* calls.c (prepare_call_address): Remove SIBCALLP parameter and add
	FLAGS parameter.  Deal with indirect calls by descriptor and adjust.
	Set STATIC_CHAIN_REG_P on the static chain register, if any.
	(call_expr_flags): Set ECF_BY_DESCRIPTOR for calls by descriptor.
	(expand_call): Likewise.  Move around call to prepare_call_address
	and pass all flags to it.
	* cfgexpand.c (expand_call_stmt): Reinstate CALL_EXPR_BY_DESCRIPTOR.
	* gimple.h (enum gf_mask): New GF_CALL_BY_DESCRIPTOR value.
	(gimple_call_set_by_descriptor): New setter.
	(gimple_call_by_descriptor_p): New getter.
	* gimple.c (gimple_build_call_from_tree): SetCALL_EXPR_BY_DESCRIPTOR.
	(gimple_call_flags): Deal with GF_CALL_BY_DESCRIPTOR.
	* langhooks.h (struct lang_hooks): Add custom_function_descriptors.
	* langhooks-def.h (LANG_HOOKS_CUSTOM_FUNCTION_DESCRIPTORS): Define.
	(LANG_HOOKS_INITIALIZER): Add LANG_HOOKS_CUSTOM_FUNCTION_DESCRIPTORS.
	* rtl.h (STATIC_CHAIN_REG_P): New macro.
	* rtlanal.c (find_first_parameter_load): Skip static chain registers.
	* target.def (custom_function_descriptors): New POD hook.
	* tree.h (FUNC_ADDR_BY_DESCRIPTOR): New flag on ADDR_EXPR.
	(CALL_EXPR_BY_DESCRIPTOR): New flag on CALL_EXPR.
	* tree-core.h (ECF_BY_DESCRIPTOR): New mask.
	Document FUNC_ADDR_BY_DESCRIPTOR and CALL_EXPR_BY_DESCRIPTOR.
	* tree.c (make_node_stat) <tcc_declaration>: Use FUNCTION_ALIGNMENT.
	(build_common_builtin_nodes): Initialize init_descriptor and
	adjust_descriptor.
	* tree-nested.c: Include target.h.
	(struct nesting_info): Add 'any_descr_created' field.
	(get_descriptor_type): New function.
	(lookup_element_for_decl): New function extracted from...
	(create_field_for_decl): Likewise.
	(lookup_tramp_for_decl): ...here.  Adjust.
	(lookup_descr_for_decl): New function.
	(convert_tramp_reference_op): Deal with descriptors.
	(build_init_call_stmt): New function extracted from...
	(finalize_nesting_tree_1): ...here.  Adjust and deal withdescriptors.
	* defaults.h (FUNCTION_ALIGNMENT): Define.
	(TRAMPOLINE_ALIGNMENT): Set to above instead of FUNCTION_BOUNDARY.
	* config/i386/i386.h (TARGET_CUSTOM_FUNCTION_DESCRIPTORS): Define.
	* config/ia64/ia64.h (TARGET_CUSTOM_FUNCTION_DESCRIPTORS): Likewise.
	* config/rs6000/rs6000.h (TARGET_CUSTOM_FUNCTION_DESCRIPTORS):Likewise.
	* config/sparc/sparc.h (TARGET_CUSTOM_FUNCTION_DESCRIPTORS): Likewise.
ada/
	* gcc-interface/misc.c (LANG_HOOKS_CUSTOM_FUNCTION_DESCRIPTORS):Define.
	* gcc-interface/trans.c (Attribute_to_gnu) <Attr_Access>: Deal with
	a zero TARGET_CUSTOM_FUNCTION_DESCRIPTORS specially for Code_Address.
	Otherwise, if TARGET_CUSTOM_FUNCTION_DESCRIPTORS is positive, set
	FUNC_ADDR_BY_DESCRIPTOR for 'Access/'Unrestricted_Access of nested
	subprograms if the type can use an internal representation.
	(call_to_gnu): Likewise, but set CALL_EXPR_BY_DESCRIPTOR on indirect
	calls if the type can use an internal representation.

From-SVN: r241222

1 files changed, 23 insertions, 1 deletions

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 0241cb5..795ad1b 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -502,7 +502,7 @@ Objective-C and Objective-C++ Dialects}.
 -fverbose-asm  -fpack-struct[=@var{n}]  @gol
 -fleading-underscore  -ftls-model=@var{model} @gol
 -fstack-reuse=@var{reuse_level} @gol
--ftrapv  -fwrapv @gol
+-ftrampolines  -ftrapv  -fwrapv @gol
 -fvisibility=@r{[}default@r{|}internal@r{|}hidden@r{|}protected@r{]} @gol
 -fstrict-volatile-bitfields -fsync-libcalls}
 
@@ -12067,6 +12067,28 @@ unit, or if @option{-fpic} is not given on the command line.
 The default without @option{-fpic} is @samp{initial-exec}; with
 @option{-fpic} the default is @samp{global-dynamic}.
 
+@item -ftrampolines
+@opindex ftrampolines
+For targets that normally need trampolines for nested functions, always
+generate them instead of using descriptors.  Otherwise, for targets that
+do not need them, like for example HP-PA or IA-64, do nothing.
+
+A trampoline is a small piece of code that is created at run time on the
+stack when the address of a nested function is taken, and is used to call
+the nested function indirectly.  Therefore, it requires the stack to be
+made executable in order for the program to work properly.
+
+@option{-fno-trampolines} is enabled by default on a language by language
+basis to let the compiler avoid generating them, if it computes that this
+is safe, and replace them with descriptors.  Descriptors are made up of data
+only, but the generated code must be prepared to deal with them.  As of this
+writing, @option{-fno-trampolines} is enabled by default only for Ada.
+
+Moreover, code compiled with @option{-ftrampolines} and code compiled with
+@option{-fno-trampolines} are not binary compatible if nested functions are
+present.  This option must therefore be used on a program-wide basis and be
+manipulated with extreme care.
+
 @item -fvisibility=@r{[}default@r{|}internal@r{|}hidden@r{|}protected@r{]}
 @opindex fvisibility
 Set the default ELF image symbol visibility to the specified option---all