Index: lib/CodeGen/CGCXX.cpp
===================================================================
--- lib/CodeGen/CGCXX.cpp
+++ lib/CodeGen/CGCXX.cpp
@@ -109,17 +109,8 @@
       D->getType()->getAs<FunctionType>()->getCallConv())
     return true;
 
-  return TryEmitDefinitionAsAlias(GlobalDecl(D, Dtor_Base),
-                                  GlobalDecl(BaseD, Dtor_Base));
-}
-
-/// Try to emit a definition as a global alias for another definition.
-/// If \p InEveryTU is true, we know that an equivalent alias can be produced
-/// in every translation unit.
-bool CodeGenModule::TryEmitDefinitionAsAlias(GlobalDecl AliasDecl,
-                                             GlobalDecl TargetDecl) {
-  if (!getCodeGenOpts().CXXCtorDtorAliases)
-    return true;
+  GlobalDecl AliasDecl(D, Dtor_Base);
+  GlobalDecl TargetDecl(BaseD, Dtor_Base);
 
   // The alias will use the linkage of the referent.  If we can't
   // support aliases with that linkage, fail.
@@ -193,6 +184,9 @@
   auto *Alias = llvm::GlobalAlias::create(AliasValueType, 0, Linkage, "",
                                           Aliasee, &getModule());
 
+  // Destructors are always unnamed_addr.
+  Alias->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
+
   // Switch any previous uses to the alias.
   if (Entry) {
     assert(Entry->getType() == AliasType &&
Index: lib/CodeGen/CodeGenModule.h
===================================================================
--- lib/CodeGen/CodeGenModule.h
+++ lib/CodeGen/CodeGenModule.h
@@ -1193,7 +1193,6 @@
   /// are emitted lazily.
   void EmitGlobal(GlobalDecl D);
 
-  bool TryEmitDefinitionAsAlias(GlobalDecl Alias, GlobalDecl Target);
   bool TryEmitBaseDestructorAsAlias(const CXXDestructorDecl *D);
 
   llvm::GlobalValue *GetGlobalValue(StringRef Ref);
Index: lib/CodeGen/ItaniumCXXABI.cpp
===================================================================
--- lib/CodeGen/ItaniumCXXABI.cpp
+++ lib/CodeGen/ItaniumCXXABI.cpp
@@ -3693,6 +3693,9 @@
   // Create the alias with no name.
   auto *Alias = llvm::GlobalAlias::create(Linkage, "", Aliasee);
 
+  // Constructors and destructors are always unnamed_addr.
+  Alias->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
+
   // Switch any previous uses to the alias.
   if (Entry) {
     assert(Entry->getType() == Aliasee->getType() &&
Index: test/CodeGenCXX/constructor-alias.cpp
===================================================================
--- test/CodeGenCXX/constructor-alias.cpp
+++ test/CodeGenCXX/constructor-alias.cpp
@@ -9,4 +9,4 @@
 B::B() {
 }
 
-// CHECK: @_ZN1BC1Ev = alias void (%struct.B*), void (%struct.B*)* @_ZN1BC2Ev
+// CHECK: @_ZN1BC1Ev = unnamed_addr alias void (%struct.B*), void (%struct.B*)* @_ZN1BC2Ev
Index: test/CodeGenCXX/ctor-dtor-alias.cpp
===================================================================
--- test/CodeGenCXX/ctor-dtor-alias.cpp
+++ test/CodeGenCXX/ctor-dtor-alias.cpp
@@ -14,8 +14,8 @@
 // Test that we produce the appropriate comdats when creating aliases to
 // weak_odr constructors and destructors.
 
-// CHECK1: @_ZN5test16foobarIvEC1Ev = weak_odr alias void {{.*}} @_ZN5test16foobarIvEC2Ev
-// CHECK1: @_ZN5test16foobarIvED1Ev = weak_odr alias void (%"struct.test1::foobar"*), void (%"struct.test1::foobar"*)* @_ZN5test16foobarIvED2Ev
+// CHECK1: @_ZN5test16foobarIvEC1Ev = weak_odr unnamed_addr alias void {{.*}} @_ZN5test16foobarIvEC2Ev
+// CHECK1: @_ZN5test16foobarIvED1Ev = weak_odr unnamed_addr alias void (%"struct.test1::foobar"*), void (%"struct.test1::foobar"*)* @_ZN5test16foobarIvED2Ev
 // CHECK1: define weak_odr void @_ZN5test16foobarIvEC2Ev({{.*}} comdat($_ZN5test16foobarIvEC5Ev)
 // CHECK1: define weak_odr void @_ZN5test16foobarIvED2Ev({{.*}} comdat($_ZN5test16foobarIvED5Ev)
 // CHECK1: define weak_odr void @_ZN5test16foobarIvED0Ev({{.*}} comdat($_ZN5test16foobarIvED5Ev)
@@ -141,7 +141,7 @@
 
 namespace test8 {
   // Test that we replace ~zed with ~bar which is an alias to ~foo.
-  // CHECK4: @_ZN5test83barD2Ev = alias {{.*}} @_ZN5test83fooD2Ev
+  // CHECK4: @_ZN5test83barD2Ev = unnamed_addr alias {{.*}} @_ZN5test83fooD2Ev
   // CHECK4: define internal void @__cxx_global_var_init.5()
   // CHECK4: call i32 @__cxa_atexit({{.*}}@_ZN5test83barD2Ev
   struct foo {
@@ -232,8 +232,8 @@
   ~foo();
 };
 foo::~foo() {}
-// CHECK6: @_ZN6test113fooD2Ev = alias {{.*}} @_ZN6test113barD2Ev
-// CHECK6: @_ZN6test113fooD1Ev = alias {{.*}} @_ZN6test113fooD2Ev
+// CHECK6: @_ZN6test113fooD2Ev = unnamed_addr alias {{.*}} @_ZN6test113barD2Ev
+// CHECK6: @_ZN6test113fooD1Ev = unnamed_addr alias {{.*}} @_ZN6test113fooD2Ev
 }
 
 namespace test12 {
@@ -243,6 +243,6 @@
 };
 
 template class foo<1>;
-// CHECK6: @_ZN6test123fooILi1EED1Ev = weak_odr alias {{.*}} @_ZN6test123fooILi1EED2Ev
+// CHECK6: @_ZN6test123fooILi1EED1Ev = weak_odr unnamed_addr alias {{.*}} @_ZN6test123fooILi1EED2Ev
 // CHECK6: define weak_odr void @_ZN6test123fooILi1EED2Ev({{.*}}) {{.*}} comdat($_ZN6test123fooILi1EED5Ev)
 }
Index: test/CodeGenCXX/destructors.cpp
===================================================================
--- test/CodeGenCXX/destructors.cpp
+++ test/CodeGenCXX/destructors.cpp
@@ -96,7 +96,7 @@
 
 // complete destructor alias tested above
 
-// CHECK2-LABEL: @_ZN5test01AD1Ev = alias {{.*}} @_ZN5test01AD2Ev
+// CHECK2-LABEL: @_ZN5test01AD1Ev = unnamed_addr alias {{.*}} @_ZN5test01AD2Ev
 // CHECK2-LABEL: define void @_ZN5test01AD2Ev(%"struct.test0::A"* %this) unnamed_addr
 // CHECK2: invoke void @_ZN5test06MemberD1Ev
 // CHECK2:   unwind label [[MEM_UNWIND:%[a-zA-Z0-9.]+]]
@@ -104,7 +104,7 @@
 // CHECK2:   unwind label [[BASE_UNWIND:%[a-zA-Z0-9.]+]]
 
 // In C++11, the destructors are often known not to throw.
-// CHECK2v11-LABEL: @_ZN5test01AD1Ev = alias {{.*}} @_ZN5test01AD2Ev
+// CHECK2v11-LABEL: @_ZN5test01AD1Ev = unnamed_addr alias {{.*}} @_ZN5test01AD2Ev
 // CHECK2v11-LABEL: define void @_ZN5test01AD2Ev(%"struct.test0::A"* %this) unnamed_addr
 // CHECK2v11: call void @_ZN5test06MemberD1Ev
 // CHECK2v11: call void @_ZN5test04BaseD2Ev
@@ -153,15 +153,15 @@
 
   struct M : A { ~M(); };
   M::~M() {}
-  // CHECK3: @_ZN5test11MD2Ev = alias {{.*}} @_ZN5test11AD2Ev
+  // CHECK3: @_ZN5test11MD2Ev = unnamed_addr alias {{.*}} @_ZN5test11AD2Ev
 
   struct N : A, Empty { ~N(); };
   N::~N() {}
-  // CHECK3: @_ZN5test11ND2Ev = alias {{.*}} @_ZN5test11AD2Ev
+  // CHECK3: @_ZN5test11ND2Ev = unnamed_addr alias {{.*}} @_ZN5test11AD2Ev
 
   struct O : Empty, A { ~O(); };
   O::~O() {}
-  // CHECK3: @_ZN5test11OD2Ev = alias {{.*}} @_ZN5test11AD2Ev
+  // CHECK3: @_ZN5test11OD2Ev = unnamed_addr alias {{.*}} @_ZN5test11AD2Ev
 
   struct P : NonEmpty, A { ~P(); };
   P::~P() {} // CHECK3-LABEL: define void @_ZN5test11PD2Ev(%"struct.test1::P"* %this) unnamed_addr
@@ -174,7 +174,7 @@
 
   struct S : A { ~S(); int x; };
   S::~S() {}
-  // CHECK4: @_ZN5test11SD2Ev = alias {{.*}}, bitcast {{.*}} @_ZN5test11AD2Ev
+  // CHECK4: @_ZN5test11SD2Ev = unnamed_addr alias {{.*}}, bitcast {{.*}} @_ZN5test11AD2Ev
 
   struct T : A { ~T(); B x; };
   T::~T() {} // CHECK4-LABEL: define void @_ZN5test11TD2Ev(%"struct.test1::T"* %this) unnamed_addr
Index: test/CodeGenCXX/dllexport-alias.cpp
===================================================================
--- test/CodeGenCXX/dllexport-alias.cpp
+++ test/CodeGenCXX/dllexport-alias.cpp
@@ -14,5 +14,5 @@
 
 A::~A() {}
 
-// CHECK: @_ZN1AC1Ev = dso_local dllexport alias void (%class.A*), void (%class.A*)* @_ZN1AC2Ev
-// CHECK: @_ZN1AD1Ev = dso_local dllexport alias void (%class.A*), void (%class.A*)* @_ZN1AD2Ev
+// CHECK: @_ZN1AC1Ev = dso_local dllexport unnamed_addr alias void (%class.A*), void (%class.A*)* @_ZN1AC2Ev
+// CHECK: @_ZN1AD1Ev = dso_local dllexport unnamed_addr alias void (%class.A*), void (%class.A*)* @_ZN1AD2Ev
Index: test/CodeGenCXX/dllexport.cpp
===================================================================
--- test/CodeGenCXX/dllexport.cpp
+++ test/CodeGenCXX/dllexport.cpp
@@ -641,7 +641,7 @@
   A::~A() { }
   B::~B() { }
   // Emit a alias definition of B's constructor.
-  // M32-DAG: @"??1B@UseDtorAlias@@QAE@XZ" = dso_local dllexport alias {{.*}} @"??1A@UseDtorAlias@@QAE@XZ"
+  // M32-DAG: @"??1B@UseDtorAlias@@QAE@XZ" = dso_local dllexport unnamed_addr alias {{.*}} @"??1A@UseDtorAlias@@QAE@XZ"
 }
 
 struct __declspec(dllexport) DefaultedCtorsDtors {
Index: test/CodeGenCXX/microsoft-abi-structors-alias.cpp
===================================================================
--- test/CodeGenCXX/microsoft-abi-structors-alias.cpp
+++ test/CodeGenCXX/microsoft-abi-structors-alias.cpp
@@ -22,7 +22,7 @@
 void foo() {
   B b;
 }
-// CHECK-DAG: @"??1B@test2@@UAE@XZ" = dso_local alias void (%"struct.test2::B"*), bitcast (void (%"struct.test2::A"*)* @"??1A@test2@@UAE@XZ" to void (%"struct.test2::B"*)*)
+// CHECK-DAG: @"??1B@test2@@UAE@XZ" = dso_local unnamed_addr alias void (%"struct.test2::B"*), bitcast (void (%"struct.test2::A"*)* @"??1A@test2@@UAE@XZ" to void (%"struct.test2::B"*)*)
 }
 
 namespace test3 {
Index: test/CodeGenCXX/virtual-bases.cpp
===================================================================
--- test/CodeGenCXX/virtual-bases.cpp
+++ test/CodeGenCXX/virtual-bases.cpp
@@ -4,7 +4,7 @@
   A();
 };
 
-// CHECK: @_ZN1AC1Ev = alias {{.*}} @_ZN1AC2Ev
+// CHECK: @_ZN1AC1Ev = unnamed_addr alias {{.*}} @_ZN1AC2Ev
 // CHECK-LABEL: define void @_ZN1AC2Ev(%struct.A* %this) unnamed_addr
 A::A() { }
 
Index: test/CodeGenCXX/virtual-destructor-calls.cpp
===================================================================
--- test/CodeGenCXX/virtual-destructor-calls.cpp
+++ test/CodeGenCXX/virtual-destructor-calls.cpp
@@ -14,11 +14,11 @@
 };
 
 // Complete dtor: just an alias because there are no virtual bases.
-// CHECK: @_ZN1BD1Ev = alias {{.*}} @_ZN1BD2Ev
+// CHECK: @_ZN1BD1Ev = unnamed_addr alias {{.*}} @_ZN1BD2Ev
 
 // (aliases from C)
-// CHECK: @_ZN1CD2Ev = alias {{.*}}, bitcast {{.*}} @_ZN1BD2Ev
-// CHECK: @_ZN1CD1Ev = alias {{.*}} @_ZN1CD2Ev
+// CHECK: @_ZN1CD2Ev = unnamed_addr alias {{.*}}, bitcast {{.*}} @_ZN1BD2Ev
+// CHECK: @_ZN1CD1Ev = unnamed_addr alias {{.*}} @_ZN1CD2Ev
 
 // Base dtor: actually calls A's base dtor.
 // CHECK-LABEL: define void @_ZN1BD2Ev(%struct.B* %this) unnamed_addr