[MemorySSA] Teach LoopSimplify to preserve MemorySSA.

Summary:
Preserve MemorySSA in LoopSimplify, in the old pass manager, if the analysis is available.
Do not preserve it in the new pass manager.
Update tests.

Subscribers: nemanjai, jlebar, javed.absar, Prazek, kbarton, zzheng, jsji, llvm-commits, george.burgess.iv, chandlerc

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60833

llvm-svn: 360270

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 65d5928e99c..f9dc09e88e9 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1894,10 +1894,14 @@ unsigned llvm::removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB) {
 }
 
 unsigned llvm::changeToUnreachable(Instruction *I, bool UseLLVMTrap,
-                                   bool PreserveLCSSA, DomTreeUpdater *DTU) {
+                                   bool PreserveLCSSA, DomTreeUpdater *DTU,
+                                   MemorySSAUpdater *MSSAU) {
   BasicBlock *BB = I->getParent();
   std::vector <DominatorTree::UpdateType> Updates;
 
+  if (MSSAU)
+    MSSAU->changeToUnreachable(I);
+
   // Loop over all of the successors, removing BB's entry from any PHI
   // nodes.
   if (DTU)