[FFmpeg-devel] [PATCH] 'vorbis_residue_decode' optimizations

Michael Niedermayer michaelni
Tue Sep 9 16:22:50 CEST 2008

On Tue, Sep 09, 2008 at 05:47:28AM -0600, Loren Merritt wrote:
> On Tue, 9 Sep 2008, Siarhei Siamashka wrote:
> > On Wednesday 03 September 2008, Michael Niedermayer wrote:
> >>
> >> This could be added as a SHOW_CONST_UBITS
> >> also gcc should be able to build the mask itself at compile time as long as
> >> no asm shift tricks re used.
> >
> > Sure. The only problem is that it would be nice to use the same macro for both
> > constant and non-constant expressions. Adding one more macro does not add much
> > convenience because the compiler can't either insert a constant or use asm
> > shift trick automatically. Or can it?
> __builtin_constant_p

I was unaware of this one, and i did search for a way to put both in the
same macro. Using this is definitly a good idea, though it should be
wraped in a macro like FF_IS_CONST() that can be defined to 0 when the
compiler doesnt support __builtin_constant_p

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

There will always be a question for which you do not know the correct awnser.
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