[FFmpeg-devel] [FFmpeg-cvslog] r12171 - trunk/doc/optimization.txt

[Mike Melanson]

?smail D?nmez wrote:
> Hi,
> 
> 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.

-- 
	-Mike Melanson