How to generate MMX code with GCC?

[Erven Rohou <erven.rohou@xxxxxxxx>]

Hello,

I am trying to generate MMX code, but had no luck so far.

Here is the piece of code:

typedef int v2si __attribute__ ((vector_size (8)));
typedef int v4si __attribute__ ((vector_size (16)));

v2si foo(v2si a, v2si b)
{
  return a+b;
}

v4si bar(v4si a, v4si b)
{
  return a+b;
}

int main()
{
  return 0;
}

When compiling with GCC 4.5 "gcc -mmmx -msse4.2 -O2 -S", the function bar nicely 
uses SSE instructions. But foo looks pretty bad. I expected a single paddd 
instruction.
foo:
        pushl   %ebp
        movl    %esp, %ebp
        subl    $64, %esp
        movq    %mm0, -56(%ebp)
        movl    %ebx, -12(%ebp)
        movl    -56(%ebp), %ebx
        movl    %esi, -8(%ebp)
        movl    -52(%ebp), %esi
        movq    %mm1, -56(%ebp)
        movl    -56(%ebp), %ecx
        movl    %edi, -4(%ebp)
        movl    -52(%ebp), %edi
        movl    %ebx, -48(%ebp)
        movl    %esi, -44(%ebp)
        movl    -8(%ebp), %esi
        leal    (%ecx,%ebx), %eax
        movl    -12(%ebp), %ebx
        movl    %eax, -56(%ebp)
        movl    %edi, -36(%ebp)
        movl    -36(%ebp), %eax
        movd    -56(%ebp), %xmm0
        addl    -44(%ebp), %eax
        movl    %ecx, -40(%ebp)
        movl    -4(%ebp), %edi
        pinsrd  $0x1, %eax, %xmm0
        movq    %xmm0, -64(%ebp)
        movdq2q %xmm0, %mm0
        movl    %ebp, %esp
        popl    %ebp
        ret
From the dumps produced by -fdump-tree-all, it seems that veclower splits the 
64-bit vectors.

Any idea what I am missing?

Thanks,

--
Erven.