[PATCH RFC 2/2] x86: default to not accepting Xeon Phi insns

[Jiang, Haochen]

> From: Jan Beulich <jbeulich@suse.com>
> Sent: Friday, November 15, 2024 6:59 PM
>
> Gcc15 has Xeon Phi support removed. While we don't want to remove
> support, require these deprecated insns to be enabled explicitly.

I thought I have replied this but I realized I did not until I just glanced through
the Binutils archive.

Among all the insts, prefetchwt1 is missing. It is also in Xeon Phi and should also
be not accepted by default.

> ---
> RFC: Likely this wants holding back until gcc15 was actually released,
>      to avoid negatively affecting in particular gcc14.

Yes for sure, either to catch up with Binutils 2.44 or to wait for GCC15 release
seems both ok to me.

> 
> Seeing the various *ig*-intel.d that needed adjustment, I actually question
> their value. Checking this once (e.g. for AVX512F) ought to be enough to be
> certain the intended behavior is there. We could down the number of tests by
> 8 or more this way.

We could remove that. They are quite duplicate.

Thx,
Haochen