I ran into some test failures where common code changed vector division
by constant into a multiply-high operation (MULHU). But these are not
implemented by the back-end, so we failed to recognize the insn.
Fixed by marking MULHU/MULHS as Expand for vector types.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214716 91177308-0d34-0410-b5e6-96231b3b80d8