[FFmpeg-devel] r9017 breaks WMA decoding on Intel Macs

[Michael Niedermayer]

Hi

On Thu, May 31, 2007 at 10:10:04AM +0200, Guillaume Poirier wrote:
> Hi,
> 
> castet.matthieu at free.fr wrote:
> > Quoting Guillaume POIRIER <poirierg at gmail.com>:
> > 
> >> Hi,
> >>
> >>> 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).
> 
> NO! Read the message I posted on Date: Wed, 30 May 2007 00:28:58 +0200
>  with the dissasm.

i think he speaks about the 123%4 style solution, this does break on
all assemblers in some cases


[...]
> >> 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
> 
> I disagree. Newer gas _do_ complain about the syntax, and Trent
> already explained the shortcomings of current implementation, no need
> for me to restate them here.

put a "memory" on the clobber list and trents argument is gone

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

Everything should be made as simple as possible, but not simpler.
-- Albert Einstein
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