[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 #3 from Daniel Santos <daniel.santos at pobox dot com> ---
Thank you for the report Martin.  I apologize for my slow start on this, I've
been a bit under the weather.  So when I wrote the code for using aligned SSE
saves with realigned (non-DRAP) stack pointer and the -mcall-ms2sysv-xlogues
feature, I had failed to anticipate the need for a stack alignment greater than
16 bytes for the function body.  This ICE is actually occurring from the
realigned stack changes, but this problem also exists with the
-mcall-ms2sysv-xlogues feature and both need to be fixed.

For the sake of the ABI, we only need to save the XMM portion of each SIMD
register (https://msdn.microsoft.com/en-us/library/9z1stfyw.aspx) and we only
need a 16-byte alignment to for those, but this function body needs its locals
64-byte aligned.

On a side note, with the introduction of AVX-512, I wonder if there are some
opportunities to make more efficient (compact) use of the stack with holes
upwards of 56 bytes in the save area.  I should probably learn AVX/2/512
better.