[FFmpeg-cvslog] r12512 - trunk/libavcodec/i386/dsputil_mmx.c

Michael Niedermayer michaelni
Fri Mar 21 01:44:43 CET 2008


On Fri, Mar 21, 2008 at 02:04:46AM +0200, ?smail D?nmez wrote:
> On Fri, Mar 21, 2008 at 1:55 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> > On Fri, Mar 21, 2008 at 12:16:53AM +0200, Uoti Urpala wrote:
> >  > On Thu, 2008-03-20 at 14:52 -0700, Mike Melanson wrote:
> >  > > michael wrote:
> >  > > > Log:
> >  > > > Hardcode register to prevent aparent miscompilation.
> >  > > > Fixes regression tests with gcc 2.95.
> >  > >
> >  > > Awesome. FATE thanks you. :)
> >  >
> >  > Not so awesome for people with working compilers. The change makes the
> >  > code worse for the sake of working around bugs in an obsolete compiler.
> >
> >  #define uoti_worse_code supports_gcc2_95()
> >
> >  Anyway, the "worse" code should be faster, as it uses a register where the old
> >  could use memory. Also the gcc 2.95 bug helped finding a unused temp variable
> >  (see previous commit) removing that surely improved speed.
> 
> "should be" faster? You always require people to benchmark first
> before changing such code, did you actually benchmarked your change?

No, i didnt.
First because the code should be faster with a half sane compiler.
Second because it fixes the regression tests. And the 1 extra mov which a
non sane compiler might add really if its meassureable at all is less
important than the regression tests.
That is i would have commited even if the affected code was a very tiny
bit slower.

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

Many things microsoft did are stupid, but not doing something just because
microsoft did it is even more stupid. If everything ms did were stupid they
would be bankrupt already.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-cvslog/attachments/20080321/cb5a3ec4/attachment.pgp>



More information about the ffmpeg-cvslog mailing list