[Ffmpeg-devel] Need -maltivec in addition to -faltivec for OSX

Michael Niedermayer michaelni
Fri Aug 12 21:51:58 CEST 2005


On Fri, Aug 12, 2005 at 02:48:55PM +0200, Dan Villiom Podlaski Christiansen wrote:
> On 10/08/05, Steven M. Schultz <sms at 2bsd.com> wrote:
> > Hi -
> > 
> >         Ok - now that the other changes have been addressed
> >         here's the remaining (single line) change for ./configure  as
> >         a patch by itself.
> > 
> >         Cheers,
> >         Steven Schultz
> Hi,
> I suspect that this patch may be incorrect, or at least might have
> some unwanted side-effects. From reading the documentation, using
> -maltivec will allow GCC to generate AltiVec instructions from
> ordinary, non-vectorised C-code. Currently, an AltiVec-enabled build
> of FFmpeg should work on a G3, and using -maltivec might break this.
> Have you verified that this still works on a G3s? If not, I may be
> able to check it later.

i think you are right, the change is problematic, the reason why i 
still applied it is that -maltivec was altready used for some gcc
versions ...
i think some --enable-runtime-cpudetect (or --disable) could be added
to make it clear if the binary should be optimized for cpu X but run on
any cpu of the same architecture or if its ok if it runs just on X
alternatively the --tune option might be usefull for the distinction


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