1 files changed, 17 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/MemorySSAUpdater.cpp b/llvm/lib/Analysis/MemorySSAUpdater.cpp
index 0d1e6471e98..57b9cc98a43 100644
--- a/llvm/lib/Analysis/MemorySSAUpdater.cpp
+++ b/llvm/lib/Analysis/MemorySSAUpdater.cpp
@@ -180,6 +180,10 @@ MemoryAccess *MemorySSAUpdater::recursePhi(MemoryAccess *Phi) {
 template <class RangeType>
 MemoryAccess *MemorySSAUpdater::tryRemoveTrivialPhi(MemoryPhi *Phi,
                                                     RangeType &Operands) {
+  // Bail out on non-opt Phis.
+  if (NonOptPhis.count(Phi))
+    return Phi;
+
   // Detect equal or self arguments
   MemoryAccess *Same = nullptr;
   for (auto &Op : Operands) {
@@ -320,6 +324,10 @@ void MemorySSAUpdater::fixupDefs(const SmallVectorImpl<MemoryAccess *> &Vars) {
     auto *Defs = MSSA->getWritableBlockDefs(NewDef->getBlock());
     auto DefIter = NewDef->getDefsIterator();
 
+    // The temporary Phi is being fixed, unmark it for not to optimize.
+    if (MemoryPhi *Phi = dyn_cast_or_null<MemoryPhi>(NewDef))
+      NonOptPhis.erase(Phi);
+
     // If there is a local def after us, we only have to rename that.
     if (++DefIter != Defs->end()) {
       cast<MemoryDef>(DefIter)->setDefiningAccess(NewDef);
@@ -379,6 +387,11 @@ void MemorySSAUpdater::fixupDefs(const SmallVectorImpl<MemoryAccess *> &Vars) {
 template <class WhereType>
 void MemorySSAUpdater::moveTo(MemoryUseOrDef *What, BasicBlock *BB,
                               WhereType Where) {
+  // Mark MemoryPhi users of What not to be optimized.
+  for (auto *U : What->users())
+    if (MemoryPhi *PhiUser = dyn_cast_or_null<MemoryPhi>(U))
+      NonOptPhis.insert(PhiUser);
+
   // Replace all our users with our defining access.
   What->replaceAllUsesWith(What->getDefiningAccess());
 
@@ -390,6 +403,10 @@ void MemorySSAUpdater::moveTo(MemoryUseOrDef *What, BasicBlock *BB,
     insertDef(MD);
   else
     insertUse(cast<MemoryUse>(What));
+
+  // Clear dangling pointers. We added all MemoryPhi users, but not all
+  // of them are removed by fixupDefs().
+  NonOptPhis.clear();
 }
 
 // Move What before Where in the MemorySSA IR.