Re: Using the Intel's MMX Instruction Set in gcc3.2

[Ulrich Prakash <uprakash at npd dot hcltech dot com>]

Hi All,

I have got the solution for this..Thought of putting it across.
We have to use the Intrinsic library provided by gcc here.

The below is a program to test the PMADDWD(Packed Multiply and Add) of the 
MMX Instruction Set.

NOTE: compile like this>gcc  -mmmx testmac.c
(-mmmx option is important here.)

------------------------TESTMAC.C-----------------------------------
#include <mmintrin.h>


int  main()
{
   __m64 m1 = 0x00ff00a300bc00ae;
   __m64 m2 = 0x0001000100010001;
 __m64 m3;

   unsigned char *data;
   unsigned char ch;
   int i;


  //asm ("pmaddwd m1,m2\n\t");
   m3 =_mm_madd_pi16 (m1, m2);

   printf("value is %x%x\n", m1);
   printf("value is %x%x\n", m2);
   printf("value is %x%x\n", m3);

   data = (char *)&m3;

   for ( i = 0; i < 8; i++)
        {
        printf("Element %d value is %x\n", i, data[i]);
        }


   return;
}


Thanks for the pointers and the individual mails sent to me which gave me 
an insight of doing this.
I guess that there is a scarcity of material on this subject in the Net.

Regards,
Prakash.
~

At 20.18 05/03/2003 +0530, Ulrich Prakash wrote:
Hi,

I tried this piece of code.


-----testmac.c-----------
#include <mmintrin.h>


int main()
{
   __m64 m1 = 12;
   __m64 m2 = 24;
 __m64 m3;

asm ("pmaddwd m1,m2\n\t");

m3 = m1;


   return;
}


and tried compiling using> gcc -mmmx testmac.c
I get the foll ERROR:
/tmp/cc0rnlnq.s: Assembler messages:
/tmp/cc0rnlnq.s:18: Error: too many memory references for `pmaddwd'

though i could find nothing wrong in usage of asm ("pmaddwd m1,m2\n\t");

Please help me if I am missing something.


Thanks,
Prakash.

At 02:06 PM 3/5/03 +0100, Andrea 'fwyzard' Bocci wrote:
At 16.32 05/03/2003 +0530, Ulrich Prakash wrote:
Hi,


I am using gcc version3.2,which supports the MMX Instruction Set.
Can anyone tell me how to use this Instruction Set in my C program?

Is there a particular way that GCC provides to use the MMX Instruction Set 
directly?(If so,how?)
(OR)
Is it through an assembly function(.s file) in which I would have to use 
these Instruction Sets,and which I would have to call in my C program?

I don't recall now, I think there should be some intrinsics for that, or 
whatever. Have a look into the GCC manual, looking for MMX.

.fwyzard.