hi guys,
i write to you direct because i can't find the relevant mailing list
for help with the mmintrin functions. there's a thread at:
http://gcc.gnu.org/ml/gcc-help/2007-04/msg00201.html
that details my problems.
i want to sum an array of longs using mmx. i use the functions:
_mm_set_pi32 and _m_paddd
but the resultant binary contains significantly less efficient code
than inline asm or even plain C ( for(i=0;i<n;i++)total+=a[i]; ).
here's the relevant function:
simd_mmintrin(n, is)
I *is;
{ __m64 q,r;
I i;
_m_empty();
q=_m_from_int(0);
for (i=0; i < n; i+=W) {
r=_mm_set_pi32(is[i],is[i+1]);
q=_m_paddd(q,r);
}
union {long a[2];__m64 m;}u;
u.m=q;
return u.a[0]+u.a[1];
}
and the rest of the code and a shell script to run it is in the thread above.