[MPlayer-dev-eng] [PATCH] configure cmov detection
diego at biurrun.de
Wed Oct 25 18:19:27 CEST 2006
On Sun, Oct 15, 2006 at 08:14:45PM +0200, Diego Biurrun wrote:
> On Sun, Oct 15, 2006 at 09:08:28PM +0300, Ivan Kalvachev wrote:
> > 2006/10/15, Diego Biurrun <diego at biurrun.de>:
> > >On Sun, Oct 15, 2006 at 08:36:23PM +0300, Ivan Kalvachev wrote:
> > >> To let lavcodecs use cmov for cabac decoder (h264), we need to detect
> > >> it in configure.
> > >>
> > >> I followed the _mmx way of detection.
> > >>
> > >> I'm not sure what processors besides i686 support cmov, so I wrote
> > >> K6-2+ , feel free to correct me.
> > >
> > >I think you are trying to say "K6-2 or later" by K6-2+, this is not
> > >correct, K6-2+ is a processor model. It does not support cmov, though,
> > >my K6-III+ does not.
> > I think I overdid the things.
> > The whole detection could be simple check if the cpu is 686 or newer.
> > there is alredy code in libavutil that does this and it does use cmov.
> > e.g. libavutil.h/internal.h:
> > #if __CPU__ >= 686 && !defined(RUNTIME_CPUDETECT)
> > #define COPY3_IF_LT(x,y,a,b,c,d)\
> > asm volatile (\
> > "cmpl %0, %3 \n\t"\
> > "cmovl %3, %0 \n\t"\
> > "cmovl %4, %1 \n\t"\
> > "cmovl %5, %2 \n\t"\
> > : "+r" (x), "+r" (a), "+r" (c)\
> > : "r" (y), "r" (b), "r" (d)\
> > );
> > #else
> > ...
> OK, then it should just be a matter of adding the proper ifdefs to
> libavcdodec/cabac.h. Since we already have a precedent for that it
> should suffice.
This has been solved differently in FFmpeg, HAVE_CMOV is now defined
there, so we should do the same. We can either apply Ivan's patch to
configure or port the stuff that Guillaume put into FFmpeg's configure.
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