Update MemorySSA in SimpleLoopUnswitch.

Summary:
Teach SimpleLoopUnswitch to preserve MemorySSA.

Subscribers: sanjoy, jlebar, Prazek, george.burgess.iv, llvm-commits

Differential Revision: https://reviews.llvm.org/D47022

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@348263 91177308-0d34-0410-b5e6-96231b3b80d8
32 files changed