[MPlayer-dev-eng] [PATCH] configure cmov detection

[Diego Biurrun]

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.

Diego