[Bug target/80969] [8 Regression] ICE in ix86_expand_prologue, at config/i386/i386.c:14606

["daniel.santos at pobox dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80969

--- Comment #4 from Daniel Santos <daniel.santos at pobox dot com> ---
Created attachment 41794
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41794&action=edit
proposed fix (still needs cleanup and tests)

This still needs cleanup and tests as well as some explanations, but it appears
to fix the problem and passes regression tests.  I haven't tested on a machine
with avx512f, however.  So there is still work and testing to be done.

This re-works the way the realigned stack is calculated and also reduces wasted
stack space due to realignment in some cases.  One drawback is that I have some
code some-what duplicated in ix86_compute_frame_layout and I would like to
spend some more time with it to see if I can refactor it.

I will better document the changes when I have some more time.