[FFmpeg-devel] [PATCH] Heavy optimization of IFF decoder

[Sebastian Vater]

Ronald S. Bultje a ?crit :
> Hi,
>
> 2010/4/27 M?ns Rullg?rd <mans at mansr.com>:
>   
>> "Ronald S. Bultje" <rsbultje at gmail.com> writes:
>>     
>>> On Mon, Apr 26, 2010 at 7:39 PM, Sebastian Vater
>>> <cdgs.basty at googlemail.com> wrote:
>>>       
>>>> +    const uint32_t lut[] = {0x0000000,
>>>> +                            0x1000000 << plane,
>>>> +                            0x0010000 << plane,
>>>> +                            0x1010000 << plane,
>>>> +                            0x0000100 << plane,
>>>> +                            0x1000100 << plane,
>>>> +                            0x0010100 << plane,
>>>> +                            0x1010100 << plane,
>>>> +                            0x0000001 << plane,
>>>> +                            0x1000001 << plane,
>>>> +                            0x0010001 << plane,
>>>> +                            0x1010001 << plane,
>>>> +                            0x0000101 << plane,
>>>> +                            0x1000101 << plane,
>>>> +                            0x0010101 << plane,
>>>> +                            0x1010101 << plane};
>>>>         
>>> I really can't imagine that a static const lut[][] isn't faster. which
>>> file did you use to test this? (Is it on mphq/samples?)
>>>       
>> A static table whose values are shifted in the loop is 7% faster on ARM.
>>     
>
> It's a little slower on x86 (~12%). However, a (static) 2D array is
> faster (3%) over the original patch. Mans just said that's fine on ARM
> as well, so you should probably implement that (don't forget that
> plane is const, so do a const *lut = table[plane] before entering the
> loop, else gcc messes up).
>   

Please clarify on this, what kind of static 2D array should I use now?
Just apply this one? Well, this one is 20% slower (increases from 6.2k
to 8.9k) for me than my original.

-- 

Best regards,
                   :-) Basty/CDGS (-:

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