be folded. Instead, fail to fold the entire vector.
We could also return a vector with some elements folded and some not. If anyone
thinks that's a better approach, please speak up!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55689 91177308-0d34-0410-b5e6-96231b3b80d8
