re PR target/25967 (Add attribute naked for x86)

re PR target/25967 (Add attribute naked for x86)

	PR target/25967
	* config/i386/i386.c (ix86_function_naked): New function.
	(ix86_can_use_return_insn_p): Return false for naked functions.
	(ix86_expand_prologue): Skip prologue for naked functions.
	(ix86_expand_epilogue): Skip epilogue for naked functions
	and emit trap instruction.
	(ix86_warn_func_return): New function.
	(ix86_attribute_table): Add "naked" attribute specification.
	(TARGET_WARN_FUNC_RETURN): Define.
	* doc/extend.texi (x86 Function Attributes) <naked>: Document it.

testsuite/ChangeLog:

	PR target/25967
	* gcc.target/i386/naked-1.c: New test.
	* gcc.target/i386/naked-2.c: Ditto.
	* gcc.target/i386/naked-3.c: Ditto.
	* gcc.target/x86_64/abi/ms-sysv/ms-sysv.c: Remove
	do_test_body0 stub function, use attribute "naked" instead.
	* gcc.dg/pr44290-1.c: Use naked_functions effective target.
	* gcc.dg/pr44290-2.c: Ditto.

From-SVN: r250736