[FFmpeg-devel] r9017 breaks WMA decoding on Intel Macs
castet.matthieu at free.fr
Thu May 31 09:36:59 CEST 2007
Quoting Guillaume POIRIER <poirierg at gmail.com>:
> > This won't assemble correctly if any of the memory operands already have a
> > displacement. Loren explained why:
> > http://article.gmane.org/gmane.comp.video.ffmpeg.devel/51453
> I agree. This patch's main purpose is to show how to write this
> routine with proper syntax
No, it is broken if you aren't lucky (ie the offset is positive).
> (Bear in mind that all assemblers produce a
> warning here. To a certain extend, we may consider that the reason it
> works with FSF AS is just by pure luck.)
Well that's more like a gas extension that was made for case like that.
> But IMHO, it's a bit pointless, because
> whatever the speed figures may look like, we are comparing 1 solution
> that appears to work by luck, and another that is more reliable. Speed
> isn't what your patch is after.
There is no luck in the old solution providing :
- we tell gcc the memory we modify (may be using "memory" clobber).
- we use a gas supporting the +(%reg) syntax
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