[X86][SSE] Improve lowering of vXi64 multiplies
As mentioned on PR30845, we were performing our vXi64 multiplication as:
AloBlo = pmuludq(a, b);
AloBhi = pmuludq(a, psrlqi(b, 32));
AhiBlo = pmuludq(psrlqi(a, 32), b);
return AloBlo + psllqi(AloBhi, 32)+ psllqi(AhiBlo, 32);
when we could avoid one of the upper shifts with:
AloBlo = pmuludq(a, b);
AloBhi = pmuludq(a, psrlqi(b, 32));
AhiBlo = pmuludq(psrlqi(a, 32), b);
return AloBlo + psllqi(AloBhi + AhiBlo, 32);
This matches the lowering on gcc/icc.
Differential Revision: https://reviews.llvm.org/D27756
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@290267 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed