[Bug target/66697] Feature request: -mstackrealign and force_align_arg_pointer for x86_64

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66697

H.J. Lu <hjl.tools at gmail dot com> changed:

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--- Comment #20 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Uroš Bizjak from comment #19)
> (In reply to Justas L from comment #18)
> > Out of curiosity, what could it be that makes -mincoming-stack-boundary=3
> > successfully deal with rogue code while -mstackrealign fails at that?
> > Shouldn't -mstackrealign do the same job without being told what the outside
> > stack alignment is, or am I misunderstanding it?
> 
> -mstackrealign conditionally generates realignment prologue, depending on
> presence of insns that require 128bit alignment. It looks that heuristics is
> not yet fully reliable on x86_64. Bugreports welcome!

-mstackrealign works correctly as designed on x86-64.  The
issue is MIN_STACK_BOUNDARY.  When MIN_STACK_BOUNDARY is 128,
you don't need to realign the stack if you only need 128-bit
stack alignment.