[MPlayer-dev-eng] Re: dsputil_mmx.c: -O2
Rich Felker
dalias at aerifal.cx
Mon Sep 18 02:23:09 CEST 2006
On Mon, Sep 18, 2006 at 03:51:19AM +0400, Vladimir Mosgalin wrote:
> Hi Carl Eugen Hoyos!
>
> On 2006.09.17 at 23:19:43 +0000, Carl Eugen Hoyos wrote next:
>
> > 4.1.1:
> > without my patch (best results in >10 tests):
> > BENCHMARKs: VC: 64.651s VO: 17.885s A: 0.000s Sys: 2.112s = 84.648s
> > BENCHMARKs: VC: 64.659s VO: 17.850s A: 0.000s Sys: 2.100s = 84.609s
> > with my patch - -O2 for dsputil_mmx.c (worst results!):
> > BENCHMARKs: VC: 57.822s VO: 18.448s A: 0.000s Sys: 2.181s = 78.452s
> > BENCHMARKs: VC: 57.824s VO: 18.608s A: 0.000s Sys: 2.109s = 78.541s
> >
> > 3.4.6:
> > without my patch:
> > BENCHMARKs: VC: 57.439s VO: 17.993s A: 0.000s Sys: 2.517s = 77.948s
> > BENCHMARKs: VC: 57.138s VO: 17.943s A: 0.000s Sys: 2.160s = 77.242s
> > with my patch - -O2 for dsputil_mmx.c:
> > BENCHMARKs: VC: 56.687s VO: 17.948s A: 0.000s Sys: 2.181s = 76.816s
> > BENCHMARKs: VC: 56.795s VO: 18.129s A: 0.000s Sys: 2.114s = 77.038s
>
> You know, it looks like some buggy optimization in gcc4 (comparing to
> gcc 3.4) making it almost as worse as gcc 2.95.. Maybe this should be
> reported to gcc developers. Some kind of conflict between inline asm and
> gcc optimizations or something like that.
I suspect it has to do with inlining.
> Only dsputil change matters? Have you investigated whether compiling
> the rest of mplayer with -O2 makes postprocessing faster? Because on
> modern systems, unless to go to 1080p hdtv, more time is spent on
> postprocessing than on decoding...
However it's always possible to turn postproc off if you don't have
enough cpu time. It's not possible to turn decoding off. :)
Optimization should always be oriented towards minimizing the
requirements for base case decoding IMO.
Rich
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