[FFmpeg-devel] [FFmpeg-cvslog] r12171 - trunk/doc/optimization.txt
Thu Feb 21 21:29:11 CET 2008
?smail D?nmez wrote:
> On Thu, Feb 21, 2008 at 10:19 PM, Mike Melanson <mike at multimedia.cx> wrote:
>> ?smail D?nmez wrote:
>> > Hi,
>> > On Thu, Feb 21, 2008 at 9:57 PM, Uoti Urpala <uoti.urpala at pp1.inet.fi> wrote:
>> >> On Thu, 2008-02-21 at 20:11 +0100, Michael Niedermayer wrote:
>> >> > As you can see gcc injects 2 unneeded lea instructions in the innermost loop.
>> >> It'd need at least one other instruction instead though. Anyway I do not
>> >> see that behavior with Debian's gcc-4.3, gcc always uses 3 instructions
>> >> for the adds (same as the handwritten asm).
>> > That supports my theory that gcc 4.3 is a big improvement optimization wise.
>> According to the data FATE has been collecting, FFmpeg binaries built
>> using gcc out of SVN are not performing as well as gcc <= 4.2.x. Much
>> worse in fact. This only seems to be an issue on x86_32.
> Well that requires further investigation, is it a general slow down or
> some specific part like h264 decoding?
Unfortunately, I don't have a very rich diversity of tests in the suite
yet, nor a good way to visualize trends.
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