[FFmpeg-devel] [PATCH] avcodec/scpr: optimize shift loop.

[Michael Niedermayer]

On Sat, Sep 09, 2017 at 08:02:04PM -0300, James Almer wrote:
> On 9/9/2017 7:47 PM, Michael Niedermayer wrote:
> > On Sat, Sep 09, 2017 at 04:37:52PM -0500, Brian Matherly wrote:
> >>
> >> On 9/9/2017 1:27 PM, Michael Niedermayer wrote:
> >>> +            // If the image is sufficiently aligned, compute 8 samples at once
> >>> +            if (!(((uintptr_t)dst) & 7)) {
> >>> +                uint64_t *dst64 = (uint64_t *)dst;
> >>> +                int w = avctx->width>>1;
> >>> +                for (x = 0; x < w; x++) {
> >>> +                    dst64[x] = (dst64[x] << 3) & 0xFCFCFCFCFCFCFCFCULL;
> >>> +                }
> >>> +                x *= 8;
> >>> +            } else
> >>> +                x = 0;
> >>> +            for (; x < avctx->width * 4; x++) {
> >>>                  dst[x] = dst[x] << 3;
> >>>              }
> >>
> >> Forgive me if I'm not understanding the code correctly, but couldn't
> >> you always apply the optimization if you align the first (up to) 7
> >> samples?
> > 
> > yes, thats possible, it would be optimizing a case that probably
> > never occurs in practice though.
> > 
> > If people want, i can add code to handle misaligned cases ?
> 
> No, frame->data[0] should always be sufficiently aligned.
> I hadn't even looked what dst pointed to, hence my original comment
> about this change potentially not have an effect in all cases.
> 
> It's ok as is, no need to make it anymore complex.

will apply

thanks

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is dangerous to be right in matters on which the established authorities
are wrong. -- Voltaire
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