Fix SCEVExpander's existing PHI reuse checking to recognize the

Fix SCEVExpander's existing PHI reuse checking to recognize the
case where there are loop-invariant instructions somehow left
inside the loop, and in a position where they won't dominate
the IV increment position.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96448 91177308-0d34-0410-b5e6-96231b3b80d8