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

[Michael Niedermayer]

On Thu, Sep 30, 2010 at 04:02:00PM -0300, Ramiro Polla wrote:
> 2010/9/30 M?ns Rullg?rd <mans at mansr.com>:
> > Ramiro Polla <ramiro.polla at gmail.com> writes:
> >> 2010/9/30 M?ns Rullg?rd <mans at mansr.com>:
> >>> Ramiro Polla <ramiro.polla at gmail.com> writes:
> >>>> What about
> >>>> #if HAVE_XMM_CLOBBERS
> >>>> # ? ?define XMM_CLOBBERS(a, ...) __VA_ARGS__
> >>>> #else
> >>>> # ? ?define XMM_CLOBBERS(a, ...) a
> >>>> #endif
> >>>>
> >>>> to be used as in lavc/x86/fft_sse.c:
> >>>> ? ? ? ? :"+r"(j), "+r"(k)
> >>>> ? ? ? ? :"r"(output+n4), "r"(output+n4*3),
> >>>> ? ? ? ? ?"m"(*m1m1m1m1)
> >>>> ? ? ? ? XMM_CLOBBERS(, : "%xmm0", "%xmm1", "%xmm7")
> >>>> ? ? );
> >>>
> >>> That falls over if any other clobbers are needed.
> >>
> >> If any other clobbers are needed they could be written before the macro.
> >
> > That won't work.
> 
> : "eax" XMM_CLOBBERS(,, "%xmm0", "%xmm1", "%xmm7")
> 
> But I agree having "cc" as dummy is simpler.

it may be simpler but your variant is more correct

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

No snowflake in an avalanche ever feels responsible. -- Voltaire
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