inline-asm, i386: Add "redzone" clobber support

inline-asm, i386: Add "redzone" clobber support

The following patch adds a "redzone" clobber (recognized everywhere,
even on on targets which don't do anything with it),
with which one can mark the rare case where inline asm pushes
something on the stack or uses call instruction without taking
red zone into account (i.e. addq $-128, %rsp; and addq $128, %rsp
around that).

2024-11-28  Jakub Jelinek  <jakub@redhat.com>

gcc/
	* target.def (redzone_clobber): New target hook.
	* varasm.cc (decode_reg_name_and_count): Return -5 for
	"redzone".
	* cfgexpand.cc (expand_asm_stmt): Handle redzone clobber.
	* config/i386/i386.h (struct machine_function): Add
	asm_redzone_clobber_seen member.
	* config/i386/i386.cc (ix86_compute_frame_layout): Don't
	use red zone if cfun->machine->asm_redzone_clobber_seen.
	(ix86_redzone_clobber): New function.
	(TARGET_REDZONE_CLOBBER): Redefine.
	* doc/extend.texi (Clobbers and Scratch Registers): Document
	the "redzone" clobber.
	* doc/tm.texi.in: Add @hook TARGET_REDZONE_CLOBBER.
	* doc/tm.texi: Regenerate.
gcc/testsuite/
	* gcc.dg/asm-redzone-1.c: New test.
	* gcc.target/i386/asm-redzone-1.c: New test.