[MemorySSA & LoopPassManager] Update MemorySSA in formDedicatedExitBlocks.

MemorySSA is now updated when forming dedicated exit blocks.
Resolves PR40037.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354623 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed