[FFmpeg-devel] [PATCH] Altivec version of h264_idct_add

David Conrad umovimus
Sun Jun 3 07:07:52 CEST 2007

On Jun 3, 2007, at 12:38 AM, Luca Barbato wrote:

> David Conrad wrote:
>> On Jun 2, 2007, at 10:15 PM, Luca Barbato wrote:
>>> Loren Merritt wrote:
>>>> The switch could be changed to a table if it matters.
>>> In theory vec_ste is all we need here sadly, I cannot manage to  
>>> get it
>>> working right for the unaligned cases.
>> I've never really looked at vec_ste before today, but it seems that
>> vec_ste will always write the first element of the vector to the
>> rounded-down 16-byte address, and to store to an unaligned address  
>> you
>> have to move the data in the vector and store that element. The  
>> attached
>> patch does this with a permute and uses it instead of the switch. It
>> requires an additional 4 permutes and constant vector the aligned  
>> case,
>> but it seems to be a bit faster overall on my G4.
> vec_splat() should be enough (another perm spared)

Like so?

>> +    vec_u8_t repeatperm = (vec_u8_t)AVV(0x00, 0x01, 0x02, 0x03,  
>> 0x00, 0x01, 0x02, 0x03,
>> +                                        0x00, 0x01, 0x02, 0x03,  
>> 0x00, 0x01, 0x02, 0x03);
> lu

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