[MPlayer-dev-eng] [RFC] disable fastmemcpy on x86-64 by default

[Michael Niedermayer]

Hi

On Sun, May 27, 2007 at 10:47:55PM +0200, Attila Kinali wrote:
> On Sun, 27 May 2007 18:19:48 +0200
> Reimar D?ffinger <Reimar.Doeffinger at stud.uni-karlsruhe.de> wrote:
> 
> > Hello,
> > since SSE is part of the x86-64 architecture, at least glibc makes use
> > of it for its memcpy and some quick (and imprecise) tests indicate that
> > it's at least not slower.
> > So what do you think about attached patch? Can someone do more concise
> > benchmarks?
> 
> Here some benchmarks:
[...]
> I also sinlge-run tested a few other samples similar to benchmark 1 and 3
> (ie animes with divx3, divx4, xvid, h.264) codecs that didn't show any
> siginificant speed difference (<1%)
> 
> Interesting are benchmark 2 and 5, which both are faster with
> the patch. 

hmm, theres something odd ...
where is this code using any memcpy at all?
doesnt mga vo always use mem2agpcpy() ?
it seems the patch disabled this and uses plain memcpy() for it

and MIN_LEN is 2k and mem2agpcpy is just done per line which is
less then 2k so it practically falls back to rep movsb

this is in impressive series of bugs ...

if my hypothesis is correct then reimar will have some work to do ;)

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

There will always be a question for which you do not know the correct awnser.
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