[FFmpeg-devel] libavutil simd

Uoti Urpala uoti.urpala
Mon Oct 1 23:42:57 CEST 2007

On Mon, 2007-10-01 at 23:31 +0200, Michael Niedermayer wrote:
> * ppc does not seem to support clean user mode altivec detection
> * gcc requires -maltivec for altivec intrinsics
> * gcc does NOT generate code which will run on pre altivec CPUs if
>   -maltivec is used independant of use of altivec intrinsics
> * if you dont use -maltivec your code will not be optimal for a altivec
>   cpu
> so please correct me if iam wrong but i dont see how the altivec "detection"
> code in libavcodec could have ever worked short of by pure luck that gcc
> didnt use altivec anywhere when compiling normal c code
> so it really does not seem like runtime altivec detection is possible not
> even with fork and sigill catching or /proc/ with current gcc

It's possible to isolate altivec optimizations in separate files and
only use -maltivec when compiling those. No comment on whether that
would be worth doing.

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