support for x86, and UMULO/SMULO for many architectures, including PPC
(PR4201), ARM, and Cell. The resulting expansion isn't perfect, but it's
not bad.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73477 91177308-0d34-0410-b5e6-96231b3b80d8