[FFmpeg-devel] [PATCH] some SIMD write-combining for h264

[Michael Niedermayer]

On Sun, Jan 24, 2010 at 12:58:47AM -0500, Alexander Strange wrote:
> 
> On Jan 18, 2010, at 5:34 AM, Alexander Strange wrote:
> 
> > 
> > On Jan 17, 2010, at 8:27 PM, M?ns Rullg?rd wrote:
> > 
> >> Alexander Strange <astrange at ithinksw.com> writes:
> >> 
> >>> On Sun, Jan 17, 2010 at 7:54 PM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
> >>>> Alexander Strange <astrange <at> ithinksw.com> writes:
> >>>> 
> >>>>>>>> also what sets __MMX__ ? we have our own defines for that
> >>>>>>> 
> >>>>>>> It's a gcc builtin define, set based on ./configure --cpu=x adding
> >>>>>>> -march.  HAVE_MMX is for the build and not the host cpu family, and
> >>>>>>> this is inlined asm, so it can't use it.
> >>>>>> 
> >>>>>> Huh?  Host... build???
> >>>>> 
> >>>>> Oh, that was supposed to be "target"...
> >>>>> Anyway, this is MMX being used like the cmov/clz inlines, so it depends on the
> >>>>> given --cpu and not on the build system's capabilities.
> >>>> 
> >>>> Could you explain once more why this shouldn't be HAVE_MMX?
> >>>> If the user passes --disable-mmx to configure, he imo expects MMX to be disabled.
> >>>> 
> >>>> Carl Eugen
> >>> 
> >>> HAVE_MMX isn't enough to enable it - './configure --cpu=i586' enables
> >>> HAVE_MMX, but i586 doesn't have it.
> >> 
> >> Not anymore.
> > 
> > I think that was wrong. --cpu is the minimum required cpu, not the only expected cpu, but that turned off building dsputil mmx which is runtime-cpudetected. (even if runtime-cpudetection is disabled, actually)
> > Besides, './configure' also sets HAVE_MMX but targets generic x86-32 which might not have it.
> > 
> >>> Technically I'd say --disable-mmx should pass -mno-mmx to gcc, but
> >>> that seems like a complicated change to configure, so I'll check
> >>> HAVE_MMX to disable it as well.
> >> 
> >> That's almost trivial to arrange.  Do we want that?
> > 
> > The other new architectures would have to be added as configure options (sse[234] are missing), but if you want then sure.
> > 
> > Applied the first patch with #if HAVE_MMX around the file and av_always_inline.
> > The second patch needs to be rewritten now since the decoder changed under it.
> 
> Here it is, with some more opportunities I found.
> The original file now goes from 12.236s to 11.862s on x86-32 (3% faster).

iam fine with the patch once the types are correct to avoid warnings

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I wish the Xiph folks would stop pretending they've got something they
do not.  Somehow I fear this will remain a wish. -- M?ns Rullg?rd
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