SSE support in 2.4.x

[James Macnicol]

Hello,

	I was under the impression that the 2.4.x kernels enable SSE
instructions on Pentium III and later (also Athlon XP) processors by
default without needing a kernel patch as was required for 2.2.x.  Can
someone then explain why I get a SIGILL doing the following :

cunegonde(132):~/flow/test% cat psadbw2.c
#include <stdio.h>

int main(void)
{
  unsigned sad[2];
  unsigned char foo[16] = { 10, 12, 14, 16, 18, 16, 14, 12,
                            10, 12, 14, 16, 18, 16, 14, 12 };
  unsigned char bar[16] = { 10, 10, 10, 10, 10, 10, 10, 10,
                            10, 10, 10, 10, 10, 10, 10, 10 };

  __asm__ (
           "movq %1, %%xmm0\n\t"
           "movq %2, %%xmm1\n\t"
           "psadbw %%xmm0, %%xmm1\n\t"
           "movq %%xmm1, %0\n\t"
           : "=m" (*sad)
           : "m"(*foo), "m"(*bar)
  );

  printf("Result = %u,%u\n", *sad, sad[1]);

  return (0);
}
cunegonde(0):~/flow/test% gcc -Wall -o psadbw2 psadbw2.c 
cunegonde(0):~/flow/test% ./psadbw2 
Illegal instruction (core dumped)
cunegonde(132):~/flow/test% uname -a
Linux cunegonde 2.4.12 #2 Fri Oct 19 21:32:30 EST 2001 i686 unknown
cunegonde(0):~/flow/test% dmesg | grep "Pentium III"
CPU: Intel Pentium III (Coppermine) stepping 03


     or is my assembler dodgy ?  Note that I have CONFIG_MPENTIUMIII set
for the kernel configuration.


Thanks.


--
James Macnicol
j-macnicol at adfa.edu.au