Re: [PATCH] Fix CPU feature detection for fma3, avx512 and avx512icl

On Thu, Nov 9, 2023 at 10:24 PM Zuxy Meng <[email protected]> wrote:

> Greetings! I have recently got my hands on a Zen 4 machine and found
> that configure's feature detection is broken for several features.
>
> The fma3 and assembly fix is probably less controversial, but would
> like to hear what you guys think about avx512 and avx512icl.
>
> I tried to make it equivalent to ffmpeg's internal logic (
>
> https://patchwork.ffmpeg.org/project/ffmpeg/patch/[email protected]/#70640
> )
> but it has since become very wordy. Can we simplify it to check only
> one cpuinfo word for each feature based on
> https://en.wikipedia.org/wiki/AVX-512#CPUs_with_AVX-512? For example,
> check avx512dq for baseline and avx512_vnni for avx512icl. ffmpeg will
> do its own run time check anyway.


Unfortunately it breaks build because yasm doesn’t support these fancy new
instructions. Let me craft another patch to migrate us to nasm first.

>
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