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

Henrik Gramner henrik at gramner.com
Mon Oct 24 22:53:22 EEST 2016

On Mon, Oct 24, 2016 at 9:34 PM, wm4 <nfxjfg at googlemail.com> wrote:
> a ASM function must, according to the calling convention, reset the
> MMX state when returning.
> What FFmpeg does here was misdesigned from the very start.

The decision to issue emms manually instead of after every MMX
function was a deliberate decision. I'd hardly call it "misdesigned"
to make SIMD code twice as fast at the cost of technically abusing the
ABI, which has worked flawlessly for years until very recently.

More information about the ffmpeg-devel mailing list