[FFmpeg-devel] [PATCH] VP8 coeff decoding optimizations

[Jason Garrett-Glaser]

2010/8/2 M?ns Rullg?rd <mans at mansr.com>:
> Jason Garrett-Glaser <darkshikari at gmail.com> writes:
>
>> On Mon, Aug 2, 2010 at 5:38 AM, Pascal Massimino
>> <pascal.massimino at gmail.com> wrote:
>>> Jason,
>>>
>>> On Mon, Aug 2, 2010 at 1:32 AM, Jason Garrett-Glaser
>>> <darkshikari at gmail.com>wrote:
>>>
>>>> Attached are two mutually exclusive VP8 optimization patches.
>>>>
>>>> Approach in #1 (test.diff): simplify addressing by eliminating
>>>> vp8_coeff_band
>>>> Advantage: one less dereference, seems to be slightly faster, but
>>>> might depend on the mood of gcc
>>>>
>>>
>>> +1 here. Seems to be a tad faster than test3.diff (gcc 4.2.4 x86-64):
>>>
>>> current (timing decode_mb_coeffs()):
>>> 47533 dezicycles in dec, 131005 runs, 67 skips
>>> 47594 dezicycles in dec, 130977 runs, 95 skips
>>> 47681 dezicycles in dec, 131003 runs, 69 skips
>>> 47503 dezicycles in dec, 130997 runs, 75 skips
>>>
>>> test.diff
>>> 46065 dezicycles in dec, 131004 runs, 68 skips
>>> 46009 dezicycles in dec, 130996 runs, 76 skips
>>> 46119 dezicycles in dec, 131035 runs, 37 skips
>>> 46226 dezicycles in dec, 131000 runs, 72 skips
>>>
>>> test3.diff:
>>> 46255 dezicycles in dec, 131003 runs, 69 skips
>>> 46156 dezicycles in dec, 131009 runs, 63 skips
>>> 46263 dezicycles in dec, 131017 runs, 55 skips
>>
>> Anyone want to bench on another arch (ARM)?
>
> Cortex-A8, gcc 4.3.3-cs2009q1:
>
> no patch
> 1789 dezicycles in dec, 131059 runs, 13 skips
> 1786 dezicycles in dec, 131069 runs, 3 skips
> 1786 dezicycles in dec, 131069 runs, 3 skips
>
> test.diff
> 1728 dezicycles in dec, 131065 runs, 7 skips
> 1726 dezicycles in dec, 131064 runs, 8 skips
> 1728 dezicycles in dec, 131067 runs, 5 skips
>
> test3.diff
> 1780 dezicycles in dec, 131061 runs, 11 skips
> 1780 dezicycles in dec, 131065 runs, 7 skips
> 1784 dezicycles in dec, 131069 runs, 3 skips
>
> --
> M?ns Rullg?rd
> mans at mansr.com
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>

I guess we now know which is better.  Any thoughts on whether I should
improve the init code to be less stupid, or does that not matter?

Dark Shikari