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

Måns Rullgård mans
Mon Jan 18 02:27:38 CET 2010

Alexander Strange <astrange at ithinksw.com> writes:

> On Sun, Jan 17, 2010 at 7:54 PM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
>> 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
> HAVE_MMX isn't enough to enable it - './configure --cpu=i586' enables
> HAVE_MMX, but i586 doesn't have it.

Not anymore.

> Technically I'd say --disable-mmx should pass -mno-mmx to gcc, but
> that seems like a complicated change to configure, so I'll check
> HAVE_MMX to disable it as well.

That's almost trivial to arrange.  Do we want that?

M?ns Rullg?rd
mans at mansr.com

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