Re: [FFmpeg-devel] [PATCH v2 1/2] avfilter/vf_blackdetect: add AVX2 SIMD version

From: Kacper Michajlow <kasper93@gmail.com>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH v2 1/2] avfilter/vf_blackdetect: add AVX2 SIMD version
Date: Fri, 18 Jul 2025 14:41:08 +0200
Message-ID: <CABPLAST3K2DTL9JY4eQVhxmXh1ukZgx6qNfw9GoLTQPePR+q1g@mail.gmail.com> (raw)
In-Reply-To: <CABGuwEnr25LE3+Mq4ZuY9vmzQ+Enp77J23+3s3KQAdbbsMBVsw@mail.gmail.com>

On Fri, 18 Jul 2025 at 14:14, Kieran Kunhya via ffmpeg-devel
<ffmpeg-devel@ffmpeg.org> wrote:
>
> > blackdetect8_c:                                        820.8 ( 1.00x)
> > blackdetect8_avx2:                                     219.2 ( 3.74x)
> > blackdetect16_c:                                       372.8 ( 1.00x)
> > blackdetect16_avx2:                                    201.4 ( 1.85x)
> >
> > Again, sorry for being pedantic here, but it gives the wrong
> > impression especially if you look at this from outside.
>
> Also misleading as far as I understand because GCC doesn't have
> runtime detection like FFmpeg.

Speak of... actually GCC does have runtime detection. All you have to
do is mark the function with `target_clones` with requested
architectures and it will dispatch automatically during runtime the
best function to use.

See for more information:
https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-target_005fclones-function-attribute

- Kacper
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