diff --git a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
--- a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -12,6 +12,7 @@
 
 #include "InstCombineInternal.h"
 #include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AliasAnalysis.h"
@@ -65,7 +66,6 @@
     const auto [Value, IsOffset] = Elem;
     for (auto &U : Value->uses()) {
       auto *I = cast<Instruction>(U.getUser());
-
       if (auto *LI = dyn_cast<LoadInst>(I)) {
         // Ignore non-volatile loads, they are always ok.
         if (!LI->isSimple()) return false;
@@ -261,29 +261,66 @@
 public:
   PointerReplacer(InstCombinerImpl &IC) : IC(IC) {}
 
-  bool collectUsers(Instruction &I);
+  bool collectUsers(Instruction &I, MemTransferInst *Copy);
   void replacePointer(Instruction &I, Value *V);
 
 private:
+  bool collectUsersRecursive(Instruction &I, MemTransferInst *Copy);
   void replace(Instruction *I);
   Value *getReplacement(Value *I);
 
+  SmallPtrSet<Value *, 32> ValuesToRevisit;
   SmallSetVector<Instruction *, 4> Worklist;
   MapVector<Value *, Value *> WorkMap;
   InstCombinerImpl &IC;
 };
 } // end anonymous namespace
 
-bool PointerReplacer::collectUsers(Instruction &I) {
+bool PointerReplacer::collectUsers(Instruction &I, MemTransferInst *Copy) {
+  if (!collectUsersRecursive(I, Copy))
+    return false;
+
+  // Ensure that all outstanding (indirect) users of I
+  // are inserted into the Worklist. Return false
+  // otherwise.
+  for (auto *V : ValuesToRevisit)
+    if (!Worklist.contains(cast<Instruction>(V)))
+      return false;
+  return true;
+}
+
+bool PointerReplacer::collectUsersRecursive(Instruction &I,
+                                            MemTransferInst *Copy) {
   for (auto *U : I.users()) {
     auto *Inst = cast<Instruction>(&*U);
     if (auto *Load = dyn_cast<LoadInst>(Inst)) {
       if (Load->isVolatile())
         return false;
       Worklist.insert(Load);
-    } else if (isa<GetElementPtrInst>(Inst) || isa<BitCastInst>(Inst)) {
+    } else if (auto *PHI = dyn_cast<PHINode>(Inst)) {
+      // Check whether all operands of the PHI are in the Worklist.
+      // If not, keep track of the PHI and check again after collecting
+      // all users.
+      bool ValueInserted = false;
+      for (unsigned Idx = 0; Idx < PHI->getNumIncomingValues(); ++Idx) {
+        auto *V = PHI->getIncomingValue(Idx);
+        if (!isa<Instruction>(V))
+          return false;
+        if (!Worklist.contains(cast<Instruction>(V))) {
+          ValuesToRevisit.insert(PHI);
+          ValueInserted = true;
+          break;
+        }
+      }
+      if (ValueInserted)
+        continue;
+
+      Worklist.insert(PHI);
+      if (!collectUsers(*PHI, Copy))
+        return false;
+    } else if (isa<GetElementPtrInst, BitCastInst>(Inst)) {
       Worklist.insert(Inst);
-      if (!collectUsers(*Inst))
+      if (!collectUsers(*Inst, Copy))
         return false;
     } else if (auto *MI = dyn_cast<MemTransferInst>(Inst)) {
       if (MI->isVolatile())
@@ -296,7 +333,6 @@
       return false;
     }
   }
-
   return true;
 }
 
@@ -318,6 +354,14 @@
     IC.InsertNewInstWith(NewI, *LT);
     IC.replaceInstUsesWith(*LT, NewI);
     WorkMap[LT] = NewI;
+  } else if (auto *PHI = dyn_cast<PHINode>(I)) {
+    Type *NewTy = getReplacement(PHI->getIncomingValue(0))->getType();
+    auto *NewPHI = PHINode::Create(NewTy, PHI->getNumIncomingValues(),
+                                   PHI->getName(), PHI);
+    for (unsigned int I = 0; I < PHI->getNumIncomingValues(); ++I)
+      NewPHI->addIncoming(getReplacement(PHI->getIncomingValue(I)),
+                          PHI->getIncomingBlock(I));
+    WorkMap[PHI] = NewPHI;
   } else if (auto *GEP = dyn_cast<GetElementPtrInst>(I)) {
     auto *V = getReplacement(GEP->getPointerOperand());
     assert(V && "Operand not replaced");
@@ -452,10 +496,9 @@
       }
 
       PointerReplacer PtrReplacer(*this);
-      if (PtrReplacer.collectUsers(AI)) {
+      if (PtrReplacer.collectUsers(AI, Copy)) {
         for (Instruction *Delete : ToDelete)
           eraseInstFromFunction(*Delete);
-
         Value *Cast = Builder.CreateBitCast(TheSrc, DestTy);
         PtrReplacer.replacePointer(AI, Cast);
         ++NumGlobalCopies;