[FFmpeg-devel] [PATCH] ARM: remove useless stack push/pop

[Rafaël Carré]

Hi,

r12 doesn't need to be saved in called functions because it's a scratch
register.




While I'm here, did anyone try to build FFmpeg with -mthumb yet ?

"grep -Er '(pop|ldm).*pc' libavcodec/arm" shows that there is a lot of
functions which can't be called from thumb on armv4t : using ldm ...,pc
will not perform the switch from arm to thumb on these CPU.

If you want to support both thumb code and armv4t this needs changing
to use 1 more instruction (without speed cost on anything but arm7tdmi
where it would take 1 more cycle to return).

I have not built FFmpeg with thumb but it gives interesting results on
rockbox: http://www.rockbox.org/tracker/task/6734?string=thumb

-- 
Rafa?l Carr?
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