2 files changed, 52 insertions, 2 deletions

diff --git a/llvm/include/llvm/Analysis/MemorySSA.h b/llvm/include/llvm/Analysis/MemorySSA.h
index 93911b7407f..2194e8b10f6 100644
--- a/llvm/include/llvm/Analysis/MemorySSA.h
+++ b/llvm/include/llvm/Analysis/MemorySSA.h
@@ -381,7 +381,9 @@ public:
     OptimizedID = getDefiningAccess()->getID();
   }
 
-  MemoryAccess *getOptimized() const { return Optimized; }
+  MemoryAccess *getOptimized() const {
+    return cast_or_null<MemoryAccess>(Optimized);
+  }
 
   bool isOptimized() const {
     return getOptimized() && getDefiningAccess() &&
@@ -401,7 +403,7 @@ private:
 
   const unsigned ID;
   unsigned OptimizedID = INVALID_MEMORYACCESS_ID;
-  MemoryAccess *Optimized = nullptr;
+  WeakVH Optimized;
 };
 
 template <>
diff --git a/llvm/unittests/Analysis/MemorySSA.cpp b/llvm/unittests/Analysis/MemorySSA.cpp
index 326a62efb44..b255b403914 100644
--- a/llvm/unittests/Analysis/MemorySSA.cpp
+++ b/llvm/unittests/Analysis/MemorySSA.cpp
@@ -951,3 +951,51 @@ TEST_F(MemorySSATest, MoveToBeforeLiveOnEntryInvalidatesCache) {
             MSSA.getLiveOnEntryDef())
       << "(DefA = " << DefA << ")";
 }
+
+TEST_F(MemorySSATest, RemovingDefInvalidatesCache) {
+  // Create:
+  //   %x = alloca i8
+  //   %y = alloca i8
+  //   ; 1 = MemoryDef(liveOnEntry)
+  //   store i8 0, i8* %x
+  //   ; 2 = MemoryDef(1)
+  //   store i8 0, i8* %y
+  //   ; 3 = MemoryDef(2)
+  //   store i8 0, i8* %x
+  //
+  // And be sure that MSSA's caching handles the removal of def `1`
+  // appropriately.
+  IRBuilder<> B(C);
+  F = Function::Create(
+      FunctionType::get(B.getVoidTy(), {B.getInt8PtrTy()}, false),
+      GlobalValue::ExternalLinkage, "F", &M);
+
+  BasicBlock *Entry = BasicBlock::Create(C, "if", F);
+  B.SetInsertPoint(Entry);
+
+  Value *X = B.CreateAlloca(B.getInt8Ty());
+  Value *Y = B.CreateAlloca(B.getInt8Ty());
+  StoreInst *StoreX1 = B.CreateStore(B.getInt8(0), X);
+  StoreInst *StoreY = B.CreateStore(B.getInt8(0), Y);
+  StoreInst *StoreX2 = B.CreateStore(B.getInt8(0), X);
+
+  setupAnalyses();
+
+  MemorySSA &MSSA = *Analyses->MSSA;
+
+  auto *DefX1 = cast<MemoryDef>(MSSA.getMemoryAccess(StoreX1));
+  auto *DefY = cast<MemoryDef>(MSSA.getMemoryAccess(StoreY));
+  auto *DefX2 = cast<MemoryDef>(MSSA.getMemoryAccess(StoreX2));
+
+  EXPECT_EQ(DefX2->getDefiningAccess(), DefY);
+  MemoryAccess *X2Clobber = MSSA.getWalker()->getClobberingMemoryAccess(DefX2);
+  ASSERT_EQ(DefX1, X2Clobber);
+
+  MemorySSAUpdater(&MSSA).removeMemoryAccess(DefX1);
+  StoreX1->eraseFromParent();
+
+  EXPECT_EQ(DefX2->getDefiningAccess(), DefY);
+  EXPECT_EQ(MSSA.getWalker()->getClobberingMemoryAccess(DefX2),
+            MSSA.getLiveOnEntryDef())
+      << "(DefX1 = " << DefX1 << ")";
+}