[theora-dev] Issues with Win32 MMX code

John Ridges jridges at masque.com
Tue Feb 3 13:07:37 PST 2009

It seems a reasonable solution for the VC compiler, but seeing as this 
code is very
unlikely to change in the future it seems a shame to force a performance 
hit on the
GCC version because of a Microsoft bug.


theora-dev-request at xiph.org wrote:
> Date: Tue, 03 Feb 2009 06:38:42 +0100
> From: Nils Pipenbrinck <n.pipenbrinck at cubic.org>
> Subject: [theora-dev] Issues with Win32  MMX code
> To: theora-dev at xiph.org
> Message-ID: <4987D862.4070706 at cubic.org>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> Hi folks.
> Mozilla had some issues with the MMX optimized frag_recon functions over 
> the last days, and I was able to track the problem down. The code itself 
> is fine, but it unfortunately it has the tendency to cause a 
> non-deterministic compiler bug.
> The whole discussion is here:
>   https://bugzilla.mozilla.org/show_bug.cgi?id=474937
> After thinking about the problem I've suggested to remove all optimized 
> frag_recon assembler functions and replace them with MMX intrinsic based 
> versions. My hope is that the problem will dissapear that way because 
> the new functions will be no special cases for the compiler anymore.
> If we only fix/remove the function that caused the problems (that's the 
> current bug-fix) we don't win much because the problem may occur a week 
> or two later at another place.
> Any comments?
> - Nils

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