SSE2 add 32 bits parts of register xmm1

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Roman

Joined: 21 Apr 2012
Posts: 1836

Roman 14 Aug 2013, 18:07

I have 32 bits Color buffer.
I do movups xmm1,[buffer]
Now in registr xmm1 we have 4 Color each 32 bits

How i can add all 4 Colors in registr xmm1 together ?
Does for this only one SSE command ? Now i use pshufd xmm2,xmm1,1 and pshufd xmm3,xmm1,2 and pshufd xmm4,xmm1,3 then apply xmm1,xmm2,xmm3,xmm4 but its very slow.

14 Aug 2013, 18:07

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 14 Aug 2013, 22:09

Roman,

Did you mean something like horisontal add? Use phaddd xmm1, xmm0 twice while xmm0 being zero, and you're all set (it's SSSE3 though; please state the constraints clearly; your reference to pshufd implies SSE2 at least).

Should those colors be added component-wise? Or they're colorful shades of grayscale? How about saturation?

[EDIT] Oh, I'm sorry, missed SSE2 referred in subject. [/EDIT]

14 Aug 2013, 22:09

asmdev

Joined: 21 Dec 2006
Posts: 18

asmdev 14 Aug 2013, 23:17

Code:

        movdqa  xmm0, [mem]            ; 3 2 1 0
        pshufd  xmm1, xmm0, 1110b       ; _ _ 3 2
        paddb   xmm1, xmm0              ; change to "paddd" if adding dwords
        pshufd  xmm0, xmm1, 1
        paddb   xmm0, xmm1              ; change to "paddd" if adding dwords

Code:

        movdqa  xmm0, [mem]            ; 3 2 1 0
        movdqa  xmm2, [mem+16]
        pshufd  xmm1, xmm0, 1110b       ; _ _ 3 2
        pshufd  xmm3, xmm2, 1110b
        paddb   xmm1, xmm0              ; change to "paddd" if adding dwords
        paddb   xmm3, xmm2
        pshufd  xmm0, xmm1, 1
        pshufd  xmm2, xmm3, 1
        paddb   xmm0, xmm1              ; change to "paddd" if adding dwords
        paddb   xmm2, xmm3

I don't recommend unrolling any futher.

You should consider 4 regular "add" instructions in a row if you are adding dwords and EITHER memory is cached OR you are using movUps instead of movdqA.

14 Aug 2013, 23:17

Roman

Joined: 21 Apr 2012
Posts: 1836

Roman 15 Aug 2013, 13:32

baldr
Да именно сложить четири части регистра XMM1 между собой. Вроде phaddd xmm1, xmm1 то что надо. Спасибо.

15 Aug 2013, 13:32

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