[FFmpeg-cvslog] r14743 - in trunk/libavcodec: ac3dec.c ac3dec.h dsputil.c dsputil.h i386/dsputil_mmx.c

[Michael Niedermayer]

On Wed, Aug 13, 2008 at 08:14:40PM -0700, Mike Melanson wrote:
> Uoti Urpala wrote:
> > On Wed, 2008-08-13 at 19:49 -0700, Mike Melanson wrote:
> >> lorenm wrote:
> >>> Author: lorenm
> >>> Date: Thu Aug 14 01:35:40 2008
> >>> New Revision: 14743
> >>>
> >>> Log:
> >>> simd int->float
> >>> 20% faster ac3 if downmixing, 15% if not
> >> This made all of the x86_32 gcc configurations fail to build (but not 
> >> icc!). The failure looks like this:
> > 
> > The issue is that the asm uses the "x" constraint for SSE register, and
> > GCC doesn't allow that at all if the current instruction set does not
> > support SSE. So the asm will fail to compile if you try to compile the
> > file without -msse or a -march= option that implies the processor has
> > SSE available. If you configure FFmpeg with some --cpu= option that
> > supports SSE then it will compile.
> > 
> > The most robust option would be to compile SSE-using code for runtime
> > CPU detection in a separate file and use -msse when compiling that file,
> > but probably this function alone isn't enough motivation to do that.
> 
> So should we be prepared for an avalanche of bug reports when people try 
> to build FFmpeg with their usual 'configure' commands?

yes

quick fix: simply remove the x

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

Dictatorship naturally arises out of democracy, and the most aggravated
form of tyranny and slavery out of the most extreme liberty. -- Plato
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