[FFmpeg-devel] [PATCH] Unconditionally run emms on calls to emms_c() if HAVE_MMX is defined

Dominik 'Rathann' Mierzejewski dominik
Sun Jul 4 21:26:24 CEST 2010


On Sunday, 04 July 2010 at 20:02, M?ns Rullg?rd wrote:
> Dominik 'Rathann' Mierzejewski <dominik at rangers.eu.org> writes:
> 
> > On Sunday, 04 July 2010 at 17:05, M?ns Rullg?rd wrote:
> >> Eli Friedman <eli.friedman at gmail.com> writes:
> >> 
> >> > 2010/7/4 M?ns Rullg?rd <mans at mansr.com>:
> >> >> Eli Friedman <eli.friedman at gmail.com> writes:
> >> >>
> >> >>> On Sat, Jul 3, 2010 at 11:50 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
> >> >>>> Patch attached. ?We already assume HAVE_MMX implies MMX is available
> >> >>>> at runtime, so this seems like it should be OK.
> >> >>>
> >> >>> Actually, that's wrong... I think this breaks distros that want to
> >> >>> support Pentium Pro and earlier in the same binary for modern
> >> >>> computers.
> >> >>
> >> >> A binary built for i586 or earlier will be quite crippled even in
> >> >> plain C code. ?The only sane thing to do as a distro to provide two
> >> >> packages (or more).
> >> >
> >> > So you think this patch is okay?
> >> 
> >> _I_ think the idea is OK, but your patch isn't quite what I intended.
> >> I'm waiting for Reinhard to voice his opinion.  He knows what distros
> >> want, can, and can't.
> >
> > Speaking from Fedora side, the current minimum hw requirement for CPU
> > is Pentium Pro (i686). MMX is not required, so the basic package should
> > work even if MMX is not available.
> 
> Do you have any mechanism for providing multiple packages of the same
> software with different optimisations?  Allowing mmx/sse in
> non-pointered code has real performance advantages.  Do you want to
> deprive your users of those?

Yes, we have such mechanism and no, I don't want to deprive users
of the optimizations.

Regards,
R.

-- 
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