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

[Guillaume Poirier]

Hi,
Le 30 mai 07 ? 20:03, Trent Piepho a ?crit :

> On Wed, 30 May 2007, Michael Niedermayer wrote:
>>>> compiles with gcc 2.95. So there isn't any doubt in the patch  
>>>> itself.
>>>
>>> Ok, fine with me. Michael, do you think that the patch I posted
>>> earlier (100% based on Trent's, only fixing minor issues) should be
>>> applied?
>>
>> well these arent the only occurances of this syntax in ffmpeg
>> also i would like to see benchmarks, gcc has the tendency to do  
>> stupid
>> things if it can and here it can ... (=more freedom with gcc  
>> generally means
>> worse code, thats just my experience with gcc, its not always  
>> true, also
>> gcc should be getting better as the version numbers increase ...)
>> also i dont see how this additional freedom could lead to better code
>> here, it can just lead to worse code if gcc doesnt realize that  
>> things
>> can be addressed via the same register
>
> When I checked the asm output, it generates the exact same  
> instructions,
> just without the semi-incorrect asm syntax.


I beg to differ. The output it different, though very similar. I'm  
attaching the MNdiff of vanilla VS your patched version, as well in  
unified diff.

 From what I can see with the dissasm, the speed impact should be  
very small.

Both were generated with gcc (GCC) 4.1.2 20061115 (prerelease)  
(Debian 4.1.1-21)
I can probably test with GCC 2.95 later.

Guilaume

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