Fix crash in PRE.

After r203553 overflow intrinsics and their non-intrinsic (normal)
instruction get hashed to the same value. This patch prevents PRE from
moving an instruction into a predecessor block, and trying to add a phi
node that gets two different types (the intrinsic result and the
non-intrinsic result), resulting in a failing assert.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203574 91177308-0d34-0410-b5e6-96231b3b80d8