[FFmpeg-devel] [PATCH 1/4] avutil/x86/pixelutils: Empty MMX state in ff_pixelutils_sad_8x8_mmxext

[Andreas Rheinhardt]

Henrik Gramner via ffmpeg-devel:
> On Wed, Nov 1, 2023 at 10:44 AM Andreas Rheinhardt
> <andreas.rheinhardt at outlook.com> wrote:
>>  libavutil/x86/pixelutils.asm | 1 +
>>  1 file changed, 1 insertion(+)
> 
> IIRC the emms instructions is quite slow on many systems, so if this
> is the only pixelutils function using mmx it's probably better to just
> rewrite it to use SSE2 instead (even if that means only using the
> lower half of xmm registers).

Fixing it by rewriting it in a way that avoids MMX altogether is
possible, but this doesn't change the fact that all public functions
absolutely need to abide by the ABI.

- Andreas