[Ffmpeg-cvslog] CVS: ffmpeg/libavcodec/i386 h264dsp_mmx.c, 1.15, 1.16

[Diego Biurrun]

On Wed, Mar 08, 2006 at 11:34:31AM -0500, Rich Felker wrote:
> On Wed, Mar 08, 2006 at 11:39:16AM +0100, Guillaume POIRIER wrote:
> > 
> > On 3/8/06, Rich Felker <dalias at aerifal.cx> wrote:
> > > On Sat, Mar 04, 2006 at 11:31:47PM +0200, Ismail Donmez wrote:
> > > > Maybe off topic but linux kernel recently dropped support for gcc < 3.2 , it
> > > > might be worth to reconsider gcc 2.95 support in ffmpeg too.
> > >
> > > Yes and as we all know Linux sucks...
> > >
> > > > P.S: No flamewar intended
> > >
> > > Bad idea suggesting this then... :)
> > 
> > Somehow, I see it logical to have someone having an old distro (let's
> > say RH 7.0) and wanting to build a recent userland app, like FFmpeg
> > from CVS... On the contrary, having an old distro and upgrading to
> > latest 2.6 seems quite a more invasive task as it requires to upgrade
> > the a fair deal of core apps which gravitates around the kernel.
> > So IMHO it only sound logical that the kernel dev folks drop old
> > compilers, and userland dev folks keeping compatibility with old
> > compilers which haven't gone dodo yet.
> 
> The issue at hand isn't what's common case with distros, but whether
> gcc3/4 is better or worse. For many users it's worse. If you compile a
> lot of software from source, the slowness of gcc3/4 is extremely bad.
> With gcc3, the performance gains in the resulting binaries were
> marginal or often even negative (i.e. worse performance than 2.95). I
> hear gcc4 has cleaned up this regression to some extent, but they need
> to improve compiletime performance before it's viable for everyone to
> use.

I ran some benchmarks with MPlayer compiled with different versions of
gcc ages ago on my K6-III.  The result was that gcc 3.x produced smaller
binaries than 2.95.3.  gcc 3.x took 40-80% longer to compile.  The
binaries produced by gcc 3.4 were about 5% faster than 2.95, the other
gcc versions were slower.

I might be getting the numbers slightly wrong, it's been a long time.
I'm too lazy to dig out a link right now.  It would be interesting to
rerun all these tests with gcc 4.0 and 4.1.  I hear that performance is
somewhat improved for more or less the same compilation time.

Note that this only applies to x86.  gcc 2.95 is horrible on at least
PPC.

Diego