Author: Matt Taylor
Date: 23:41:38 01/14/03
Go up one level in this thread
On January 14, 2003 at 19:23:38, Sander de Zoete wrote:
>Thanks Gerd,
>
>I also did some searching myself on the web. I ended up with a website where
>SIMD was explained together with MMX,SSE,MAJC, etc. Then I also managed to
>download the instruction sets from all these processor technologies. Can I use
>these like this in Cplusplus (Borland)
>
>I really see a lot of potential here.
>
>// Put BITBOARD a into MMX
>void SetBitboardIntoMMX(BITBOARD a, unsigned int b)
>{
> asm
> {
> movq a
>
> }
> // Shift a with value b to the right
> asm
> {
> psrlw a, b
>
> }
>}
>Will something like this work?
>
>In an example a was represented by mm5 (probably the 6th memory space in MMX
>(mm0 - mm7 if I recall correctly). How do I know what is in mm5?
>
>Sander.
mm5 works exactly like a variable. How do you know what a and b are until you
set them? Same thing for mm5 -- you have to initialize it with a movd or movq
instruction. As for the significance of mm5, its significance is defined by you.
If you put a in mm5, mm5 becomes a. If you put b in mm5, it becomes b.
Note that you probably want to coalesce your statements like this:
asm
{
movq a
psrlw a, b
}
The syntax of the instructions is always going to look like this:
operation dest, src
By the way, Intel manual 245471-6 makes a very good reference.
-Matt
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