[FFmpeg-devel] [PATCH 09/13] avcodec/svq1dec: clear MMX state after MB decode loop

[Henrik Gramner]

On Mon, Oct 24, 2016 at 9:59 PM, Ronald S. Bultje <rsbultje at gmail.com> wrote:
> Good idea to reference Hendrik Gramner here, who keeps insisting we get rid
> of all MMX code in ffmpeg (at least as an option) for future Intel CPUs in
> which MMX will be deprecated.

Replacing MMX with SSE2 is indeed the most "proper" fix in my opinion,
but it's a fair amount of work and not done in an evening.

The fact that a lot of assembly lacks unit tests is certainly not
helping in that regard.

Some MMX instructions are slower than the equivalent SSE2 code on
Skylake. Intel hasn't officially commented on (as far as I know at
least) if we should expect this trend to continue, but they certainly
seem to treat MMX as legacy.

I doubt they would completely remove support for it though, backwards
compatibility is a big selling-point for x86.