[X86] Add constant folding to combineMOVMSK.

There's still some shortcoming in our ability to combine binops of constants with different sizes separated by an extend. I'll try to look at that next.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@326128 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed