[FFmpeg-devel] [RFC] clobbers for XMM registers

Michael Niedermayer michaelni
Fri Oct 1 01:11:33 CEST 2010

On Thu, Sep 30, 2010 at 10:01:11AM -0400, Ronald S. Bultje wrote:
> Hi,
> 2010/9/28 M?ns Rullg?rd <mans at mansr.com>:
> > Michael Niedermayer <michaelni at gmx.at> writes:
> >> On Tue, Sep 28, 2010 at 09:36:40AM -0400, Ronald S. Bultje wrote:
> >>> On Tue, Sep 28, 2010 at 8:34 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> >>> > you want to execute code from vp3dsp_sse2.c on a pre SSE cpu?
> >>>
> >>> All _sse2 files are templates files that are included in dsputil_mmx.c
> >>> or similar.
> >>
> >> we could add the flags to dsputil_mmx then
> >
> > That would allow the compiler to use SSE instructions in functions
> > that should be MMX only.
> I'm gonna start kicking this subject until it's solved. Come on guys,
> keep this moving. Why don't we make it (the clobbering) a macro and
> only enable this on x86-64. Don't forget all xmm registers are
> caller-save on x86-32 and x86-64 has no issues with marking clobbers
> (and even if it did, -msse is fine, there is no single x86-64 CPU that
> does not support SSE).

-msse is enabled by default on x86-64 (this is documented in the gcc docs).
i do not know what default it has on x86-32 on the various gcc versions

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

When the tyrant has disposed of foreign enemies by conquest or treaty, and
there is nothing more to fear from them, then he is always stirring up
some war or other, in order that the people may require a leader. -- Plato
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