Hi,

the stack clash protection mechanism in the x86 back-end was implemented by 
largely duplicating the existing stack checking implementation.  Now the only 
significant difference between them is the probing window, which is shifted by 
1 probing interval (not 2 as documented in explow.c), but we can certainly do 
1 more probe for stack checking even if it is redundant in almost all cases.

Tested on x86-64/Linux, OK for the mainline?


2020-07-15  Eric Botcazou  <ebotcazou@adacore.com>

	* config/i386/i386.c (ix86_compute_frame_layout): Minor tweak.
	(ix86_adjust_stack_and_probe): Delete.
	(ix86_adjust_stack_and_probe_stack_clash): Rename to above and add
	PROTECTION_AREA parameter.  If it is true, probe PROBE_INTERVAL plus
	a small dope beyond SIZE bytes.
	(ix86_emit_probe_stack_range): Use local variable.
	(ix86_expand_prologue): Adjust calls to ix86_adjust_stack_and_probe
	and tidy up the stack checking code.
	* explow.c (get_stack_check_protect): Fix head comment.
	(anti_adjust_stack_and_probe_stack_clash): Likewise.
	(allocate_dynamic_stack_space): Add comment.

-- 
Eric Botcazou