On Wed, 16 Jul 2025 17:25:12 -0300 James Almer <jamr...@gmail.com> wrote:
> On 7/16/2025 1:24 PM, Niklas Haas wrote:
> > +cglobal detect_alpha%1_%3, 6, 7, 6, color, color_stride, alpha,
> > alpha_stride, width, height, x
> > + pxor m0, m0
> > + add colorq, widthq
> > + add alphaq, widthq
> > + neg widthq
> > +%ifidn %3, limited
> > +%if ARCH_X86_64
> > + movq xm3, r6mp ; p
> > + movq xm4, r7mp ; q
> > + movq xm5, r8mp ; k
>
> They are int arguments, so no point using movq.
>
> > +%else
> > + movd xm3, r6mp ; p
> > + movd xm4, r7mp ; q
> > + movd xm5, r8mp ; k
> > +%endif
> > + vpbroadcast%2 m3, xm3
> > + vpbroadcast%2 m4, xm4
> > + vpbroadcast%2 m5, xm5
> > +%endif
> > +.lineloop:
> > + mov xq, widthq
> > + .loop:
> > + %ifidn %3, full
> > + movu m1, [colorq + xq]
> > + movu m2, [alphaq + xq]
> > + pmaxu%1 m1, m2
> > + %else
> > + pmovzx%1%2 m1, [colorq + xq]
> > + pmovzx%1%2 m2, [alphaq + xq]
> > + pmull%2 m1, m3
> > + pmull%2 m2, m4
>
> pmulld is painfully slow, so try to instead use pmaddwd. It should be
> doable because the input are words.
Wouldn't this add together adjacent pairs of words, which is not what we want?
Or do you mean I should construct two intermediate registers like
{p, 0, p, 0, p, 0, ...} and {0, p, 0, p, 0, p, ...} and then use two separate
pmaddwd instructions to process a full register?
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