[PATCH] x86/APX: Don't promote AVX512 instructions out of APX spec

[Jan Beulich]

On 16.09.2024 01:38, H.J. Lu wrote:
> V{BROADCAST,EXTRACT,INSERT}{F,I}128 and VROUND{P,S}{S,D} aren't promoted
> to support EGPR in APX spec.  Don't promote them out of APX spec.

As previously indicated - I disagree with outright removal. If you want
to have a strict mode, which compilers may want to enable, that's fine.
For hand-written assembly (possibly including inline assembly, yet there
are sharp edges there) we ought to aid programmers. We aren't obliged
to follow the spec to the letter, especially when the spec itself can be
considered questionable, as to not properly promoting all existing
insns (which surely would have been possible from a purely technical
perspective).

As an aside,
- such a commit imo likely would want to mention the commits it 
  (effectively) reverts (the need for which will disappear when the
  effect is limited to said "strict" mode),
- I'm struggling with the purpose of the additions to the
  x86-64-apx-egpr-inval testcase, with the use of ".arch default"
  there.

Jan