[FFmpeg-devel] [PATCH] some SIMD write-combining for h264

Carl Eugen Hoyos cehoyos
Mon Jan 18 01:54:44 CET 2010

Alexander Strange <astrange <at> ithinksw.com> writes:

> >>> also what sets __MMX__ ? we have our own defines for that
> >> 
> >> It's a gcc builtin define, set based on ./configure --cpu=x adding
> >> -march.  HAVE_MMX is for the build and not the host cpu family, and
> >> this is inlined asm, so it can't use it.
> > 
> > Huh?  Host... build???
> Oh, that was supposed to be "target"...
> Anyway, this is MMX being used like the cmov/clz inlines, so it depends on the
> given --cpu and not on the build system's capabilities.

Could you explain once more why this shouldn't be HAVE_MMX?
If the user passes --disable-mmx to configure, he imo expects MMX to be disabled.

Carl Eugen

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