[cairo] Added mmx fast path for fbComposeCopyAreammx

[Vladimir Vukicevic]

On Mar 10, 2008, at 12:21 PM, Frederic Plourde wrote:
>
> Here's a speedup chart that supports this optimization :
> http://pastebin.mozilla.org/362713
> A mean perf gain of 1.5X was observed for the image-rgb cases  
> instead of 0.99 as
> seen before this optim.

There's something weird here, everything shows a speedup except:

before patch:
image-rgb subimage_copy-512    0.303ms  (nommx) -> 0.321ms (mmx)  --  
94% speed

after patch:
image-rgb subimage_copy-512    0.302ms  (nommx) -> 0.347ms (mmx)  --  
87% speed

So turning MMX on for the 512x512 case made things slower, and the  
patch made it even slower... that sounds really weird, I would expect  
a bigger speedup as the image size goes up.  It would be worth trying  
1024x1024 and 2048x2048 to see whether there is an odd trend here, and  
even then to figuring out why the 512x512 case slows down.

     - Vlad