[Ffmpeg-devel] Re: [rfc] cleaning up dsputil*

[Luca Barbato]

Mike Melanson wrote:
> Ronald S. Bultje wrote:
>> Could the altivec init be made in such a way that binaries compiled on a
>> G4 work on a G3? I think I've reported this in the past, but just to
>> repeat myself: I've found that binaries of lavf/lavc compiled on a G4 do
>> not work on a G3; they appear to be using altivec code. I haven't found
>> any compiler flag that will do runtime detection of CPU. I do not have
>> this problem on x86.
> 
> Are there any runtime CPU class detection tricks that work on PPC?
> 

yes

you can check for altivec by trapping sigill or use os dependent tricks
(check dsputil_altivec)

but

the latest gcc are getting way smarter and once altivec is enabled it
will be used here and there in the scalar code to speed up certain tasks....

so

you may hack your way building with -mno-altivec the scalar code, use
the standard flags for the vector code, link everything and hope that
you didn't forget something.

I'd rather keep 2 binaries.

lu

-- 

Luca Barbato

Gentoo/linux Gentoo/PPC
http://dev.gentoo.org/~lu_zero