Re: Intel AVX10.1 Compiler Design and Support

[Hongtao Liu <crazylht@gmail.com>]

On Wed, Aug 9, 2023 at 3:17 PM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 09.08.2023 04:14, Hongtao Liu wrote:
> > On Wed, Aug 9, 2023 at 9:21 AM Hongtao Liu <crazylht@gmail.com> wrote:
> >>
> >> On Wed, Aug 9, 2023 at 3:55 AM Joseph Myers <joseph@codesourcery.com> wrote:
> >>>
> >>> Do you have any comments on the interaction of AVX10 with the
> >>> micro-architecture levels defined in the ABI (and supported with
> >>> glibc-hwcaps directories in glibc)?  Given that the levels are cumulative,
> >>> should we take it that any future levels will be ones supporting 512-bit
> >>> vector width for AVX10 (because x86-64-v4 requires the current AVX512F,
> >>> AVX512BW, AVX512CD, AVX512DQ and AVX512VL) - and so any future processors
> >>> that only support 256-bit vector width will be considered to match the
> >>> x86-64-v3 micro-architecture level but not any higher level?
> >> This is actually something we really want to discuss in the community,
> >> our proposal for x86-64-v5: AVX10.2-256(Implying AVX10.1-256) + APX.
> >> One big reason is Intel E-core will only support AVX10 256-bit, if we
> >> want to use x86-64-v5 accross  server and client, it's better to
> >> 256-bit default.
>
> Aiui these ABI levels were intended to be incremental, i.e. higher versions
> would include everything earlier ones cover. Without such a guarantee, how
> would you propose compatibility checks to be implemented in a way
Are there many software implemenation based on this assumption?
At least in GCC, it's not a big problem, we can adjust code for the
new micro-architecture level.
> applicable both forwards and backwards? If a new level is wanted here, then
> I guess it could only be something like v3.5.
But if we use avx10.1 as v3.5, it's still not subset of
x86-64-v4(avx10.1 contains avx512fp16,avx512bf16 .etc which are not in
x86-64-v4), there will be still a diverge.
Then 256-bit of x86-64-v4 as v3.5? that's too weired to me.

Our main proposal is to make AVX10.x as new micro-architecture level
with 256-bit default, either v3.5 or v5 would be acceptable if it's
just the name.
>
> Jan



-- 
BR,
Hongtao