Hi, On Mon, Oct 24, 2016 at 4:26 PM, Henrik Gramner <hen...@gramner.com> wrote:
> On Mon, Oct 24, 2016 at 9:59 PM, Ronald S. Bultje <rsbul...@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. Well, it gives us another way of fixing this issue (on x86-64 only): have sse2 implementations for all code that has a mmx (register) path right now. Given the complexity of this issue, it's worth considering that fix along with the other possibilities... Ronald _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
