X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=unittests%2FIR%2FMetadataTest.cpp;h=de2ff8f81d9df7da761658ca79aa3df8774ac875;hb=f9eaea701dd2771fbd72145ed8eaaaeb62779b08;hp=352e83ee662ee2b276ab06d4a7dacd5900991cc4;hpb=c779e96158cbac4c62df8e2053ab6a933eba5868;p=oota-llvm.git

diff --git a/unittests/IR/MetadataTest.cpp b/unittests/IR/MetadataTest.cpp
index 352e83ee662..de2ff8f81d9 100644
--- a/unittests/IR/MetadataTest.cpp
+++ b/unittests/IR/MetadataTest.cpp
@@ -7,22 +7,65 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/IR/Metadata.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Type.h"
-#include "llvm/Support/ValueHandle.h"
 #include "llvm/Support/raw_ostream.h"
 #include "gtest/gtest.h"
 using namespace llvm;
 
 namespace {
 
+TEST(ContextAndReplaceableUsesTest, FromContext) {
+  LLVMContext Context;
+  ContextAndReplaceableUses CRU(Context);
+  EXPECT_EQ(&Context, &CRU.getContext());
+  EXPECT_FALSE(CRU.hasReplaceableUses());
+  EXPECT_FALSE(CRU.getReplaceableUses());
+}
+
+TEST(ContextAndReplaceableUsesTest, FromReplaceableUses) {
+  LLVMContext Context;
+  ContextAndReplaceableUses CRU(make_unique<ReplaceableMetadataImpl>(Context));
+  EXPECT_EQ(&Context, &CRU.getContext());
+  EXPECT_TRUE(CRU.hasReplaceableUses());
+  EXPECT_TRUE(CRU.getReplaceableUses());
+}
+
+TEST(ContextAndReplaceableUsesTest, makeReplaceable) {
+  LLVMContext Context;
+  ContextAndReplaceableUses CRU(Context);
+  CRU.makeReplaceable(make_unique<ReplaceableMetadataImpl>(Context));
+  EXPECT_EQ(&Context, &CRU.getContext());
+  EXPECT_TRUE(CRU.hasReplaceableUses());
+  EXPECT_TRUE(CRU.getReplaceableUses());
+}
+
+TEST(ContextAndReplaceableUsesTest, takeReplaceableUses) {
+  LLVMContext Context;
+  auto ReplaceableUses = make_unique<ReplaceableMetadataImpl>(Context);
+  auto *Ptr = ReplaceableUses.get();
+  ContextAndReplaceableUses CRU(std::move(ReplaceableUses));
+  ReplaceableUses = CRU.takeReplaceableUses();
+  EXPECT_EQ(&Context, &CRU.getContext());
+  EXPECT_FALSE(CRU.hasReplaceableUses());
+  EXPECT_FALSE(CRU.getReplaceableUses());
+  EXPECT_EQ(Ptr, ReplaceableUses.get());
+}
+
 class MetadataTest : public testing::Test {
 protected:
   LLVMContext Context;
+  MDNode *getNode() { return MDNode::get(Context, None); }
+  MDNode *getNode(Metadata *MD) { return MDNode::get(Context, MD); }
+  MDNode *getNode(Metadata *MD1, Metadata *MD2) {
+    Metadata *MDs[] = {MD1, MD2};
+    return MDNode::get(Context, MDs);
+  }
 };
 typedef MetadataTest MDStringTest;
 
@@ -58,7 +101,7 @@ TEST_F(MDStringTest, PrintingSimple) {
   std::string Str;
   raw_string_ostream oss(Str);
   s->print(oss);
-  EXPECT_STREQ("metadata !\"testing 1 2 3\"", oss.str().c_str());
+  EXPECT_STREQ("!\"testing 1 2 3\"", oss.str().c_str());
 }
 
 // Test printing of MDString with non-printable characters.
@@ -68,7 +111,7 @@ TEST_F(MDStringTest, PrintingComplex) {
   std::string Str;
   raw_string_ostream oss(Str);
   s->print(oss);
-  EXPECT_STREQ("metadata !\"\\00\\0A\\22\\5C\\FF\"", oss.str().c_str());
+  EXPECT_STREQ("!\"\\00\\0A\\22\\5C\\FF\"", oss.str().c_str());
 }
 
 typedef MetadataTest MDNodeTest;
@@ -80,30 +123,27 @@ TEST_F(MDNodeTest, Simple) {
 
   MDString *s1 = MDString::get(Context, StringRef(&x[0], 3));
   MDString *s2 = MDString::get(Context, StringRef(&y[0], 3));
-  ConstantInt *CI = ConstantInt::get(getGlobalContext(), APInt(8, 0));
+  ConstantAsMetadata *CI = ConstantAsMetadata::get(
+      ConstantInt::get(getGlobalContext(), APInt(8, 0)));
 
-  std::vector<Value *> V;
+  std::vector<Metadata *> V;
   V.push_back(s1);
   V.push_back(CI);
   V.push_back(s2);
 
   MDNode *n1 = MDNode::get(Context, V);
-  Value *const c1 = n1;
+  Metadata *const c1 = n1;
   MDNode *n2 = MDNode::get(Context, c1);
-  Value *const c2 = n2;
+  Metadata *const c2 = n2;
   MDNode *n3 = MDNode::get(Context, V);
   MDNode *n4 = MDNode::getIfExists(Context, V);
   MDNode *n5 = MDNode::getIfExists(Context, c1);
   MDNode *n6 = MDNode::getIfExists(Context, c2);
   EXPECT_NE(n1, n2);
-#ifdef ENABLE_MDNODE_UNIQUING
   EXPECT_EQ(n1, n3);
-#else
-  (void) n3;
-#endif
   EXPECT_EQ(n4, n1);
   EXPECT_EQ(n5, n2);
-  EXPECT_EQ(n6, (Value*)0);
+  EXPECT_EQ(n6, (Metadata *)nullptr);
 
   EXPECT_EQ(3u, n1->getNumOperands());
   EXPECT_EQ(s1, n1->getOperand(0));
@@ -118,22 +158,458 @@ TEST_F(MDNodeTest, Delete) {
   Constant *C = ConstantInt::get(Type::getInt32Ty(getGlobalContext()), 1);
   Instruction *I = new BitCastInst(C, Type::getInt32Ty(getGlobalContext()));
 
-  Value *const V = I;
+  Metadata *const V = LocalAsMetadata::get(I);
   MDNode *n = MDNode::get(Context, V);
-  WeakVH wvh = n;
+  TrackingMDRef wvh(n);
 
   EXPECT_EQ(n, wvh);
 
   delete I;
 }
 
+TEST_F(MDNodeTest, SelfReference) {
+  // !0 = !{!0}
+  // !1 = !{!0}
+  {
+    auto Temp = MDNode::getTemporary(Context, None);
+    Metadata *Args[] = {Temp.get()};
+    MDNode *Self = MDNode::get(Context, Args);
+    Self->replaceOperandWith(0, Self);
+    ASSERT_EQ(Self, Self->getOperand(0));
+
+    // Self-references should be distinct, so MDNode::get() should grab a
+    // uniqued node that references Self, not Self.
+    Args[0] = Self;
+    MDNode *Ref1 = MDNode::get(Context, Args);
+    MDNode *Ref2 = MDNode::get(Context, Args);
+    EXPECT_NE(Self, Ref1);
+    EXPECT_EQ(Ref1, Ref2);
+  }
+
+  // !0 = !{!0, !{}}
+  // !1 = !{!0, !{}}
+  {
+    auto Temp = MDNode::getTemporary(Context, None);
+    Metadata *Args[] = {Temp.get(), MDNode::get(Context, None)};
+    MDNode *Self = MDNode::get(Context, Args);
+    Self->replaceOperandWith(0, Self);
+    ASSERT_EQ(Self, Self->getOperand(0));
+
+    // Self-references should be distinct, so MDNode::get() should grab a
+    // uniqued node that references Self, not Self itself.
+    Args[0] = Self;
+    MDNode *Ref1 = MDNode::get(Context, Args);
+    MDNode *Ref2 = MDNode::get(Context, Args);
+    EXPECT_NE(Self, Ref1);
+    EXPECT_EQ(Ref1, Ref2);
+  }
+}
+
+TEST_F(MDNodeTest, Print) {
+  Constant *C = ConstantInt::get(Type::getInt32Ty(Context), 7);
+  MDString *S = MDString::get(Context, "foo");
+  MDNode *N0 = getNode();
+  MDNode *N1 = getNode(N0);
+  MDNode *N2 = getNode(N0, N1);
+
+  Metadata *Args[] = {ConstantAsMetadata::get(C), S, nullptr, N0, N1, N2};
+  MDNode *N = MDNode::get(Context, Args);
+
+  std::string Expected;
+  {
+    raw_string_ostream OS(Expected);
+    OS << "!{";
+    C->printAsOperand(OS);
+    OS << ", ";
+    S->printAsOperand(OS);
+    OS << ", null";
+    MDNode *Nodes[] = {N0, N1, N2};
+    for (auto *Node : Nodes)
+      OS << ", <" << (void *)Node << ">";
+    OS << "}\n";
+  }
+
+  std::string Actual;
+  {
+    raw_string_ostream OS(Actual);
+    N->print(OS);
+  }
+
+  EXPECT_EQ(Expected, Actual);
+}
+
+TEST_F(MDNodeTest, NullOperand) {
+  // metadata !{}
+  MDNode *Empty = MDNode::get(Context, None);
+
+  // metadata !{metadata !{}}
+  Metadata *Ops[] = {Empty};
+  MDNode *N = MDNode::get(Context, Ops);
+  ASSERT_EQ(Empty, N->getOperand(0));
+
+  // metadata !{metadata !{}} => metadata !{null}
+  N->replaceOperandWith(0, nullptr);
+  ASSERT_EQ(nullptr, N->getOperand(0));
+
+  // metadata !{null}
+  Ops[0] = nullptr;
+  MDNode *NullOp = MDNode::get(Context, Ops);
+  ASSERT_EQ(nullptr, NullOp->getOperand(0));
+  EXPECT_EQ(N, NullOp);
+}
+
+TEST_F(MDNodeTest, DistinctOnUniquingCollision) {
+  // !{}
+  MDNode *Empty = MDNode::get(Context, None);
+  ASSERT_TRUE(Empty->isResolved());
+  EXPECT_FALSE(Empty->isDistinct());
+
+  // !{!{}}
+  Metadata *Wrapped1Ops[] = {Empty};
+  MDNode *Wrapped1 = MDNode::get(Context, Wrapped1Ops);
+  ASSERT_EQ(Empty, Wrapped1->getOperand(0));
+  ASSERT_TRUE(Wrapped1->isResolved());
+  EXPECT_FALSE(Wrapped1->isDistinct());
+
+  // !{!{!{}}}
+  Metadata *Wrapped2Ops[] = {Wrapped1};
+  MDNode *Wrapped2 = MDNode::get(Context, Wrapped2Ops);
+  ASSERT_EQ(Wrapped1, Wrapped2->getOperand(0));
+  ASSERT_TRUE(Wrapped2->isResolved());
+  EXPECT_FALSE(Wrapped2->isDistinct());
+
+  // !{!{!{}}} => !{!{}}
+  Wrapped2->replaceOperandWith(0, Empty);
+  ASSERT_EQ(Empty, Wrapped2->getOperand(0));
+  EXPECT_TRUE(Wrapped2->isDistinct());
+  EXPECT_FALSE(Wrapped1->isDistinct());
+}
+
+TEST_F(MDNodeTest, getDistinct) {
+  // !{}
+  MDNode *Empty = MDNode::get(Context, None);
+  ASSERT_TRUE(Empty->isResolved());
+  ASSERT_FALSE(Empty->isDistinct());
+  ASSERT_EQ(Empty, MDNode::get(Context, None));
+
+  // distinct !{}
+  MDNode *Distinct1 = MDNode::getDistinct(Context, None);
+  MDNode *Distinct2 = MDNode::getDistinct(Context, None);
+  EXPECT_TRUE(Distinct1->isResolved());
+  EXPECT_TRUE(Distinct2->isDistinct());
+  EXPECT_NE(Empty, Distinct1);
+  EXPECT_NE(Empty, Distinct2);
+  EXPECT_NE(Distinct1, Distinct2);
+
+  // !{}
+  ASSERT_EQ(Empty, MDNode::get(Context, None));
+}
+
+TEST_F(MDNodeTest, isUniqued) {
+  MDNode *U = MDTuple::get(Context, None);
+  MDNode *D = MDTuple::getDistinct(Context, None);
+  auto T = MDTuple::getTemporary(Context, None);
+  EXPECT_TRUE(U->isUniqued());
+  EXPECT_FALSE(D->isUniqued());
+  EXPECT_FALSE(T->isUniqued());
+}
+
+TEST_F(MDNodeTest, isDistinct) {
+  MDNode *U = MDTuple::get(Context, None);
+  MDNode *D = MDTuple::getDistinct(Context, None);
+  auto T = MDTuple::getTemporary(Context, None);
+  EXPECT_FALSE(U->isDistinct());
+  EXPECT_TRUE(D->isDistinct());
+  EXPECT_FALSE(T->isDistinct());
+}
+
+TEST_F(MDNodeTest, isTemporary) {
+  MDNode *U = MDTuple::get(Context, None);
+  MDNode *D = MDTuple::getDistinct(Context, None);
+  auto T = MDTuple::getTemporary(Context, None);
+  EXPECT_FALSE(U->isTemporary());
+  EXPECT_FALSE(D->isTemporary());
+  EXPECT_TRUE(T->isTemporary());
+}
+
+TEST_F(MDNodeTest, getDistinctWithUnresolvedOperands) {
+  // temporary !{}
+  auto Temp = MDTuple::getTemporary(Context, None);
+  ASSERT_FALSE(Temp->isResolved());
+
+  // distinct !{temporary !{}}
+  Metadata *Ops[] = {Temp.get()};
+  MDNode *Distinct = MDNode::getDistinct(Context, Ops);
+  EXPECT_TRUE(Distinct->isResolved());
+  EXPECT_EQ(Temp.get(), Distinct->getOperand(0));
+
+  // temporary !{} => !{}
+  MDNode *Empty = MDNode::get(Context, None);
+  Temp->replaceAllUsesWith(Empty);
+  EXPECT_EQ(Empty, Distinct->getOperand(0));
+}
+
+TEST_F(MDNodeTest, handleChangedOperandRecursion) {
+  // !0 = !{}
+  MDNode *N0 = MDNode::get(Context, None);
+
+  // !1 = !{!3, null}
+  auto Temp3 = MDTuple::getTemporary(Context, None);
+  Metadata *Ops1[] = {Temp3.get(), nullptr};
+  MDNode *N1 = MDNode::get(Context, Ops1);
+
+  // !2 = !{!3, !0}
+  Metadata *Ops2[] = {Temp3.get(), N0};
+  MDNode *N2 = MDNode::get(Context, Ops2);
+
+  // !3 = !{!2}
+  Metadata *Ops3[] = {N2};
+  MDNode *N3 = MDNode::get(Context, Ops3);
+  Temp3->replaceAllUsesWith(N3);
+
+  // !4 = !{!1}
+  Metadata *Ops4[] = {N1};
+  MDNode *N4 = MDNode::get(Context, Ops4);
+
+  // Confirm that the cycle prevented RAUW from getting dropped.
+  EXPECT_TRUE(N0->isResolved());
+  EXPECT_FALSE(N1->isResolved());
+  EXPECT_FALSE(N2->isResolved());
+  EXPECT_FALSE(N3->isResolved());
+  EXPECT_FALSE(N4->isResolved());
+
+  // Create a couple of distinct nodes to observe what's going on.
+  //
+  // !5 = distinct !{!2}
+  // !6 = distinct !{!3}
+  Metadata *Ops5[] = {N2};
+  MDNode *N5 = MDNode::getDistinct(Context, Ops5);
+  Metadata *Ops6[] = {N3};
+  MDNode *N6 = MDNode::getDistinct(Context, Ops6);
+
+  // Mutate !2 to look like !1, causing a uniquing collision (and an RAUW).
+  // This will ripple up, with !3 colliding with !4, and RAUWing.  Since !2
+  // references !3, this can cause a re-entry of handleChangedOperand() when !3
+  // is not ready for it.
+  //
+  // !2->replaceOperandWith(1, nullptr)
+  // !2: !{!3, !0} => !{!3, null}
+  // !2->replaceAllUsesWith(!1)
+  // !3: !{!2] => !{!1}
+  // !3->replaceAllUsesWith(!4)
+  N2->replaceOperandWith(1, nullptr);
+
+  // If all has gone well, N2 and N3 will have been RAUW'ed and deleted from
+  // under us.  Just check that the other nodes are sane.
+  //
+  // !1 = !{!4, null}
+  // !4 = !{!1}
+  // !5 = distinct !{!1}
+  // !6 = distinct !{!4}
+  EXPECT_EQ(N4, N1->getOperand(0));
+  EXPECT_EQ(N1, N4->getOperand(0));
+  EXPECT_EQ(N1, N5->getOperand(0));
+  EXPECT_EQ(N4, N6->getOperand(0));
+}
+
+TEST_F(MDNodeTest, replaceResolvedOperand) {
+  // Check code for replacing one resolved operand with another.  If doing this
+  // directly (via replaceOperandWith()) becomes illegal, change the operand to
+  // a global value that gets RAUW'ed.
+  //
+  // Use a temporary node to keep N from being resolved.
+  auto Temp = MDTuple::getTemporary(Context, None);
+  Metadata *Ops[] = {nullptr, Temp.get()};
+
+  MDNode *Empty = MDTuple::get(Context, ArrayRef<Metadata *>());
+  MDNode *N = MDTuple::get(Context, Ops);
+  EXPECT_EQ(nullptr, N->getOperand(0));
+  ASSERT_FALSE(N->isResolved());
+
+  // Check code for replacing resolved nodes.
+  N->replaceOperandWith(0, Empty);
+  EXPECT_EQ(Empty, N->getOperand(0));
+
+  // Check code for adding another unresolved operand.
+  N->replaceOperandWith(0, Temp.get());
+  EXPECT_EQ(Temp.get(), N->getOperand(0));
+
+  // Remove the references to Temp; required for teardown.
+  Temp->replaceAllUsesWith(nullptr);
+}
+
+typedef MetadataTest MDLocationTest;
+
+TEST_F(MDLocationTest, Overflow) {
+  MDNode *N = MDNode::get(Context, None);
+  {
+    MDLocation *L = MDLocation::get(Context, 2, 7, N);
+    EXPECT_EQ(2u, L->getLine());
+    EXPECT_EQ(7u, L->getColumn());
+  }
+  unsigned U24 = 1u << 24;
+  unsigned U16 = 1u << 16;
+  {
+    MDLocation *L = MDLocation::get(Context, U24 - 1, U16 - 1, N);
+    EXPECT_EQ(U24 - 1, L->getLine());
+    EXPECT_EQ(U16 - 1, L->getColumn());
+  }
+  {
+    MDLocation *L = MDLocation::get(Context, U24, U16, N);
+    EXPECT_EQ(0u, L->getLine());
+    EXPECT_EQ(0u, L->getColumn());
+  }
+  {
+    MDLocation *L = MDLocation::get(Context, U24 + 1, U16 + 1, N);
+    EXPECT_EQ(0u, L->getLine());
+    EXPECT_EQ(0u, L->getColumn());
+  }
+}
+
+TEST_F(MDLocationTest, getDistinct) {
+  MDNode *N = MDNode::get(Context, None);
+  MDLocation *L0 = MDLocation::getDistinct(Context, 2, 7, N);
+  EXPECT_TRUE(L0->isDistinct());
+  MDLocation *L1 = MDLocation::get(Context, 2, 7, N);
+  EXPECT_FALSE(L1->isDistinct());
+  EXPECT_EQ(L1, MDLocation::get(Context, 2, 7, N));
+}
+
+TEST_F(MDLocationTest, getTemporary) {
+  MDNode *N = MDNode::get(Context, None);
+  auto L = MDLocation::getTemporary(Context, 2, 7, N);
+  EXPECT_TRUE(L->isTemporary());
+  EXPECT_FALSE(L->isResolved());
+}
+
+typedef MetadataTest MetadataAsValueTest;
+
+TEST_F(MetadataAsValueTest, MDNode) {
+  MDNode *N = MDNode::get(Context, None);
+  auto *V = MetadataAsValue::get(Context, N);
+  EXPECT_TRUE(V->getType()->isMetadataTy());
+  EXPECT_EQ(N, V->getMetadata());
+
+  auto *V2 = MetadataAsValue::get(Context, N);
+  EXPECT_EQ(V, V2);
+}
+
+TEST_F(MetadataAsValueTest, MDNodeMDNode) {
+  MDNode *N = MDNode::get(Context, None);
+  Metadata *Ops[] = {N};
+  MDNode *N2 = MDNode::get(Context, Ops);
+  auto *V = MetadataAsValue::get(Context, N2);
+  EXPECT_TRUE(V->getType()->isMetadataTy());
+  EXPECT_EQ(N2, V->getMetadata());
+
+  auto *V2 = MetadataAsValue::get(Context, N2);
+  EXPECT_EQ(V, V2);
+
+  auto *V3 = MetadataAsValue::get(Context, N);
+  EXPECT_TRUE(V3->getType()->isMetadataTy());
+  EXPECT_NE(V, V3);
+  EXPECT_EQ(N, V3->getMetadata());
+}
+
+TEST_F(MetadataAsValueTest, MDNodeConstant) {
+  auto *C = ConstantInt::getTrue(Context);
+  auto *MD = ConstantAsMetadata::get(C);
+  Metadata *Ops[] = {MD};
+  auto *N = MDNode::get(Context, Ops);
+
+  auto *V = MetadataAsValue::get(Context, MD);
+  EXPECT_TRUE(V->getType()->isMetadataTy());
+  EXPECT_EQ(MD, V->getMetadata());
+
+  auto *V2 = MetadataAsValue::get(Context, N);
+  EXPECT_EQ(MD, V2->getMetadata());
+  EXPECT_EQ(V, V2);
+}
+
+typedef MetadataTest ValueAsMetadataTest;
+
+TEST_F(ValueAsMetadataTest, UpdatesOnRAUW) {
+  Type *Ty = Type::getInt1PtrTy(Context);
+  std::unique_ptr<GlobalVariable> GV0(
+      new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage));
+  auto *MD = ValueAsMetadata::get(GV0.get());
+  EXPECT_TRUE(MD->getValue() == GV0.get());
+  ASSERT_TRUE(GV0->use_empty());
+
+  std::unique_ptr<GlobalVariable> GV1(
+      new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage));
+  GV0->replaceAllUsesWith(GV1.get());
+  EXPECT_TRUE(MD->getValue() == GV1.get());
+}
+
+TEST_F(ValueAsMetadataTest, CollidingDoubleUpdates) {
+  // Create a constant.
+  ConstantAsMetadata *CI = ConstantAsMetadata::get(
+      ConstantInt::get(getGlobalContext(), APInt(8, 0)));
+
+  // Create a temporary to prevent nodes from resolving.
+  auto Temp = MDTuple::getTemporary(Context, None);
+
+  // When the first operand of N1 gets reset to nullptr, it'll collide with N2.
+  Metadata *Ops1[] = {CI, CI, Temp.get()};
+  Metadata *Ops2[] = {nullptr, CI, Temp.get()};
+
+  auto *N1 = MDTuple::get(Context, Ops1);
+  auto *N2 = MDTuple::get(Context, Ops2);
+  ASSERT_NE(N1, N2);
+
+  // Tell metadata that the constant is getting deleted.
+  //
+  // After this, N1 will be invalid, so don't touch it.
+  ValueAsMetadata::handleDeletion(CI->getValue());
+  EXPECT_EQ(nullptr, N2->getOperand(0));
+  EXPECT_EQ(nullptr, N2->getOperand(1));
+  EXPECT_EQ(Temp.get(), N2->getOperand(2));
+
+  // Clean up Temp for teardown.
+  Temp->replaceAllUsesWith(nullptr);
+}
+
+typedef MetadataTest TrackingMDRefTest;
+
+TEST_F(TrackingMDRefTest, UpdatesOnRAUW) {
+  Type *Ty = Type::getInt1PtrTy(Context);
+  std::unique_ptr<GlobalVariable> GV0(
+      new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage));
+  TypedTrackingMDRef<ValueAsMetadata> MD(ValueAsMetadata::get(GV0.get()));
+  EXPECT_TRUE(MD->getValue() == GV0.get());
+  ASSERT_TRUE(GV0->use_empty());
+
+  std::unique_ptr<GlobalVariable> GV1(
+      new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage));
+  GV0->replaceAllUsesWith(GV1.get());
+  EXPECT_TRUE(MD->getValue() == GV1.get());
+
+  // Reset it, so we don't inadvertently test deletion.
+  MD.reset();
+}
+
+TEST_F(TrackingMDRefTest, UpdatesOnDeletion) {
+  Type *Ty = Type::getInt1PtrTy(Context);
+  std::unique_ptr<GlobalVariable> GV(
+      new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage));
+  TypedTrackingMDRef<ValueAsMetadata> MD(ValueAsMetadata::get(GV.get()));
+  EXPECT_TRUE(MD->getValue() == GV.get());
+  ASSERT_TRUE(GV->use_empty());
+
+  GV.reset();
+  EXPECT_TRUE(!MD);
+}
+
 TEST(NamedMDNodeTest, Search) {
   LLVMContext Context;
-  Constant *C = ConstantInt::get(Type::getInt32Ty(Context), 1);
-  Constant *C2 = ConstantInt::get(Type::getInt32Ty(Context), 2);
+  ConstantAsMetadata *C =
+      ConstantAsMetadata::get(ConstantInt::get(Type::getInt32Ty(Context), 1));
+  ConstantAsMetadata *C2 =
+      ConstantAsMetadata::get(ConstantInt::get(Type::getInt32Ty(Context), 2));
 
-  Value *const V = C;
-  Value *const V2 = C2;
+  Metadata *const V = C;
+  Metadata *const V2 = C2;
   MDNode *n = MDNode::get(Context, V);
   MDNode *n2 = MDNode::get(Context, V2);