InstCombine: Don't try to reorder shuffles where the mask is a ConstantExpr.

We can't analyze the individual values of a vector expression. PR20114.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211581 91177308-0d34-0410-b5e6-96231b3b80d8
InstCombine: Disable umul.with.overflow recognition for vectors.

It doesn't make a lot on most targets and the code isn't ready for it. PR20113.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211583 91177308-0d34-0410-b5e6-96231b3b80d8