[FFmpeg-devel] [PATCH] SSE dct32() [Was: r23095 - in trunk/libavcodec: ...]

Vitor Sessak vitor1001
Sun Jun 20 13:21:06 CEST 2010

On 06/20/2010 12:15 PM, M?ns Rullg?rd wrote:
> Vitor Sessak<vitor1001 at gmail.com>  writes:
>>>> I don't remember seeing a big difference _for the dct32 code_ between in ==
>>>> out and in != out.
>>> now iam confused, i thought the 3% you quoted was about in ==out vs in!= out
>>> ?
>> No, the 3% slowdown was when converting our general code (using FFT)
>> to have in != out.
> And that was due to missed optimisations caused by gcc not knowing
> that those pointers don't alias each other.  Marking them restrict is
> not good either, since we actually want to pass the same value
> sometimes.

That and one extra used register.


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