Index: include/llvm/Analysis/MemorySSAUpdater.h
===================================================================
--- include/llvm/Analysis/MemorySSAUpdater.h
+++ include/llvm/Analysis/MemorySSAUpdater.h
@@ -120,6 +120,14 @@
   /// |------|        |------|
   void moveAllAfterMergeBlocks(BasicBlock *From, BasicBlock *To,
                                Instruction *Start);
+  /// BasicBlock Old had New, an empty BasicBlock, added directly before it,
+  /// and the predecessors in Preds that used to point to Old, now point to
+  /// New. 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);
 
   // The below are utility functions. Other than creation of accesses to pass
   // to insertDef, and removeAccess to remove accesses, you should generally
Index: lib/Analysis/MemorySSAUpdater.cpp
===================================================================
--- lib/Analysis/MemorySSAUpdater.cpp
+++ lib/Analysis/MemorySSAUpdater.cpp
@@ -494,6 +494,32 @@
   return MA;
 }
 
+void MemorySSAUpdater::wireOldPredecessorsToNewImmediatePredecessor(BasicBlock *Old,
+                                                        BasicBlock *New,
+                                                        ArrayRef<BasicBlock *>Preds) {
+  assert(MSSA->getWritableBlockAccesses(New) == nullptr &&
+         "Access list should be null for a new block.");
+  MemoryPhi *Phi = MSSA->getMemoryAccess(Old);
+  if (!Phi)
+    return;
+  if (pred_size(Old) == 1 && pred_size(New) == Preds.size())
+    MSSA->moveTo(Phi, New, MemorySSA::Beginning);
+  else {
+    assert (Preds.size() > 0 &&
+            "Must be moving at least one predecessor to the new immediate predecessor.");
+    MemoryPhi *NewPhi = MSSA->createMemoryPhi(New);
+    for (auto *Pred : Preds) {
+      int Idx = Phi->getBasicBlockIndex(Pred);
+      assert (Idx >=0 && "Predecessor must have an incoming value in Phi.");
+      NewPhi->addIncoming(Phi->getIncomingValue(Idx), Pred);
+      Phi->unorderedDeleteIncoming(Idx);
+    }
+    Phi->addIncoming(NewPhi, New);
+    if (onlySingleValue(NewPhi))
+      removeMemoryAccess(NewPhi);
+  }
+}
+
 void MemorySSAUpdater::removeMemoryAccess(MemoryAccess *MA) {
   assert(!MSSA->isLiveOnEntryDef(MA) &&
          "Trying to remove the live on entry def");