[FFmpeg-devel] [PATCH] Better AV_ZERO128 on x86

Alexander Strange astrange
Sat Jan 15 21:28:45 CET 2011

On Sat, Jan 15, 2011 at 2:53 AM, Jason Garrett-Glaser <jason at x264.com> wrote:
> This patch makes AV_ZERO work under SSE, instead of requiring SSE2.

Fine here.

The 'struct v's defined in that file need av_alias added sometime, or
need to be moved next to the definition of av_alias64.

> But AV_ZERO still sucks, because it duplicates the pxor/xorps every
> single time it runs. ?Is there any reason we can't do what x264 does,
> that is, use intrinsics like ((__m128){0,0,0,0}) to solve the problem?
> ?This does make gcc (even crappy old gcc) reuse the value instead of
> calculating it every time.

I only did it like this to avoid an argument about using intrinsics.

Isn't it actually faster on some cpus to do xor every time, because of
register read stalls?

More information about the ffmpeg-devel mailing list