Index: llvm/trunk/include/llvm/Analysis/MemorySSAUpdater.h
===================================================================
--- llvm/trunk/include/llvm/Analysis/MemorySSAUpdater.h
+++ llvm/trunk/include/llvm/Analysis/MemorySSAUpdater.h
@@ -129,10 +129,9 @@
   /// If New is the only predecessor, move Old's Phi, if present, to New.
   /// Otherwise, add a new Phi in New with appropriate incoming values, and
   /// update the incoming values in Old's Phi node too, if present.
-  void
-  wireOldPredecessorsToNewImmediatePredecessor(BasicBlock *Old, BasicBlock *New,
-                                               ArrayRef<BasicBlock *> Preds);
-
+  void wireOldPredecessorsToNewImmediatePredecessor(
+      BasicBlock *Old, BasicBlock *New, ArrayRef<BasicBlock *> Preds,
+      bool IdenticalEdgesWereMerged = true);
   // The below are utility functions. Other than creation of accesses to pass
   // to insertDef, and removeAccess to remove accesses, you should generally
   // not attempt to update memoryssa yourself. It is very non-trivial to get
Index: llvm/trunk/lib/Analysis/MemorySSAUpdater.cpp
===================================================================
--- llvm/trunk/lib/Analysis/MemorySSAUpdater.cpp
+++ llvm/trunk/lib/Analysis/MemorySSAUpdater.cpp
@@ -498,7 +498,8 @@
 }
 
 void MemorySSAUpdater::wireOldPredecessorsToNewImmediatePredecessor(
-    BasicBlock *Old, BasicBlock *New, ArrayRef<BasicBlock *> Preds) {
+    BasicBlock *Old, BasicBlock *New, ArrayRef<BasicBlock *> Preds,
+    bool IdenticalEdgesWereMerged) {
   assert(!MSSA->getWritableBlockAccesses(New) &&
          "Access list should be null for a new block.");
   MemoryPhi *Phi = MSSA->getMemoryAccess(Old);
@@ -513,9 +514,17 @@
                              "new immediate predecessor.");
     MemoryPhi *NewPhi = MSSA->createMemoryPhi(New);
     SmallPtrSet<BasicBlock *, 16> PredsSet(Preds.begin(), Preds.end());
+    // Currently only support the case of removing a single incoming edge when
+    // identical edges were not merged.
+    if (!IdenticalEdgesWereMerged)
+      assert(PredsSet.size() == Preds.size() &&
+             "If identical edges were not merged, we cannot have duplicate "
+             "blocks in the predecessors");
     Phi->unorderedDeleteIncomingIf([&](MemoryAccess *MA, BasicBlock *B) {
       if (PredsSet.count(B)) {
         NewPhi->addIncoming(MA, B);
+        if (!IdenticalEdgesWereMerged)
+          PredsSet.erase(B);
         return true;
       }
       return false;
Index: llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp
+++ llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp
@@ -201,7 +201,8 @@
   auto *LI = Options.LI;
   auto *MSSAU = Options.MSSAU;
   if (MSSAU)
-    MSSAU->wireOldPredecessorsToNewImmediatePredecessor(DestBB, NewBB, {TIBB});
+    MSSAU->wireOldPredecessorsToNewImmediatePredecessor(
+        DestBB, NewBB, {TIBB}, Options.MergeIdenticalEdges);
 
   if (!DT && !LI)
     return NewBB;