flat assembler
Message board for the users of flat assembler.

Index > Main > xmm tutorials

Author
Thread Post new topic Reply to topic
realcr



Joined: 02 Apr 2007
Posts: 39
realcr
Hi everyone.

I was looking for some tutorials about SSE and mmx programming asm programming ,but couldn't find any besides the intel reference manuals , which one can't probably call tutorials..

Does anyone knows about such tutorial/book , or intel's reference book are actually the only resource about it?

realcr.
Post 18 Aug 2007, 15:48
View user's profile Send private message Visit poster's website MSN Messenger ICQ Number Reply with quote
r22



Joined: 27 Dec 2004
Posts: 805
r22
I don't know about tutorial information, but you can download the opcode descriptions from Intel and AMD. Also Intel and AMD has optimization manuals that cover some SSE (xmm).

A few notes:
- Make sure data is 16 byte aligned.
- Usually 64 bytes / iteration is the sweet spot for unrolling SSE loops that load and/or store data from/to memory
- Optimize the algorithm first, then attempt to make it parallel then implement it using the SSE instructions.

Here's a simple StringLength function using XMM registers.
Code:
strlen: 
;;string len with aligned and padded buffer
;;[esp+4] string pointer
      mov     eax,[esp+4]
 push    ebx
 test    eax,eax
     jz      .fail
       pxor    xmm0,xmm0
   mov     ebx,eax
.len:
;;load 32 bytes of the string
       movdqa  xmm2,[eax+16]
       movdqa  xmm1,[eax]
;;search for a null character
 pcmpeqb xmm2,xmm0
   pcmpeqb xmm1,xmm0
;;move results to 32bit registers
      pmovmskb edx,xmm2
   pmovmskb ecx,xmm1
;;combine the bit flagged results and increment the loop
       shl     edx,16
      add     eax,32
      or      ecx,edx
     jz      .len
;;calculate the length (end-start + byte_offset - 32)
       sub     eax,ebx
     bsf     ecx,ecx
     lea     eax,[eax+ecx-32]
    pop     ebx
 ret     4
.fail:
     xor     eax,eax
     pop     ebx
 ret     4

    
Post 19 Aug 2007, 02:50
View user's profile Send private message AIM Address Yahoo Messenger Reply with quote
FrozenKnight



Joined: 24 Jun 2005
Posts: 128
FrozenKnight
Thanks, I was looking for something like this are there more?
Post 20 Aug 2007, 09:48
View user's profile Send private message Reply with quote
realcr



Joined: 02 Apr 2007
Posts: 39
realcr
thanks r22. I will also go over the intel manual to see what's inside.


realcr.
Post 23 Aug 2007, 21:40
View user's profile Send private message Visit poster's website MSN Messenger ICQ Number Reply with quote
Display posts from previous:
Post new topic Reply to topic

Jump to:  


< Last Thread | Next Thread >
Forum Rules:
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Copyright © 1999-2020, Tomasz Grysztar. Also on GitHub, YouTube, Twitter.

Website powered by rwasa.