x86 ISA v3 / v4 coverage

[H.J. Lu]

On Thu, Jun 2, 2022 at 7:31 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> H.J.,
>
> the other day I came to notice two apparent anomalies:
>
> Shouldn't XOP and FMA4 be excluded from v3, just like LWP and TBM are?

Yes, they should be excluded since they don't require v3.

> Shouldn't AVX512_4FMAPS be excluded from v4, just like AVX512_4VNNIW is?

Yes, it should be since it doesn't require v4.

> And is it correct for new ISA additions (like not so long ago AVX512-FP16)
> to become part of what is covered by v3 or v4? AMX, for example, was

AVX512_FP16 requires v4.

> excluded from v3 when it was added to the code base. And e.g. GFNI is not
> part of v2 because there no "umbrella property" (VEX for v3, EVEX for v4)
> is checked, but it's strictly a white-listing of Cpu* flags.
>
> I'm afraid all of this once again is unobvious because the specification
> is not clear enough.

The ISA level is the minimum requirement.  All ISAs listed in the level can
be freely used.

-- 
H.J.