IRgen: Mark aliases of ctors and dtors as unnamed_addr.

[pcc]

Summary

This is not only semantically correct but ensures that they will not
be marked as address-significant once D48155 lands.

lib/CodeGen/CGCXX.cpp

bool CodeGenModule::TryEmitBaseDestructorAsAlias(const CXXDestructorDecl *D) {
 
   // Give up if the calling conventions don't match. We could update the call,
   // but it is probably not worth it.
   const CXXDestructorDecl *BaseD = UniqueBase->getDestructor();
   if (BaseD->getType()->getAs<FunctionType>()->getCallConv() !=
       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.
   llvm::GlobalValue::LinkageTypes Linkage = getFunctionLinkage(AliasDecl);
 
   // We can't use an alias if the linkage is not valid for one.
   if (!llvm::GlobalAlias::isValidLinkage(Linkage))
     return true;
bool CodeGenModule::TryEmitBaseDestructorAsAlias(const CXXDestructorDecl *D) {
   // requires explicit comdat support in the IL.
   if (llvm::GlobalValue::isWeakForLinker(TargetLinkage))
     return true;
 
   // Create the alias with no name.
   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 &&
            "declaration exists with different type");
     Alias->takeName(Entry);
     Entry->replaceAllUsesWith(Alias);
     Entry->eraseFromParent();
   } else {

lib/CodeGen/CodeGenModule.h

public:
   void addDeferredVTable(const CXXRecordDecl *RD) {
     DeferredVTables.push_back(RD);
   }
 
   /// Emit code for a single global function or var decl. Forward declarations
   /// are emitted lazily.
   void EmitGlobal(GlobalDecl D);
 
-  bool TryEmitDefinitionAsAlias(GlobalDecl Alias, GlobalDecl Target);
   bool TryEmitBaseDestructorAsAlias(const CXXDestructorDecl *D);
 
   llvm::GlobalValue *GetGlobalValue(StringRef Ref);
 
   /// Set attributes which are common to any form of a global definition (alias,
   /// Objective-C method, function, global variable).
   ///
   /// NOTE: This should only be called for definitions.

lib/CodeGen/ItaniumCXXABI.cpp

static void emitConstructorDestructorAlias(CodeGenModule &CGM,
   if (Entry && !Entry->isDeclaration())
     return;
 
   auto *Aliasee = cast<llvm::GlobalValue>(CGM.GetAddrOfGlobal(TargetDecl));
 
   // 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() &&
            "declaration exists with different type");
     Alias->takeName(Entry);
     Entry->replaceAllUsesWith(Alias);
     Entry->eraseFromParent();
   } else {

test/CodeGenCXX/constructor-alias.cpp

 // RUN: %clang_cc1 -emit-llvm -triple mipsel--linux-gnu -mconstructor-aliases -o - %s | FileCheck %s
 
 // The target attribute code used to get confused with aliases. Make sure
 // we don't crash when an alias is used.
 
 struct B {
   B();
 };
 B::B() {
 }
 
-// CHECK: @_ZN1BC1Ev = alias void (%struct.B*), void (%struct.B*)* @_ZN1BC2Ev
+// CHECK: @_ZN1BC1Ev = unnamed_addr alias void (%struct.B*), void (%struct.B*)* @_ZN1BC2Ev

test/CodeGenCXX/ctor-dtor-alias.cpp

 // RUN: %clang_cc1 %s -triple i686-linux -emit-llvm -o - -mconstructor-aliases | FileCheck --check-prefix=NOOPT %s
 
 // RUN: %clang_cc1 %s -triple i686-linux -emit-llvm -o - -mconstructor-aliases -O1 -disable-llvm-passes > %t
 // RUN: FileCheck --check-prefix=CHECK1 --input-file=%t %s
 // RUN: FileCheck --check-prefix=CHECK2 --input-file=%t %s
 // RUN: FileCheck --check-prefix=CHECK3 --input-file=%t %s
 // RUN: FileCheck --check-prefix=CHECK4 --input-file=%t %s
 // RUN: FileCheck --check-prefix=CHECK5 --input-file=%t %s
 // RUN: FileCheck --check-prefix=CHECK6 --input-file=%t %s
 
 // RUN: %clang_cc1 %s -triple i686-pc-windows-gnu -emit-llvm -o - -mconstructor-aliases -O1 -disable-llvm-passes | FileCheck --check-prefix=COFF %s
 
 namespace test1 {
 // 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)
 // CHECK1-NOT: comdat
 
 // COFF doesn't support comdats with arbitrary names (C5/D5).
 // COFF: define weak_odr {{.*}} void @_ZN5test16foobarIvEC2Ev({{.*}} comdat align
 // COFF: define weak_odr {{.*}} void @_ZN5test16foobarIvEC1Ev({{.*}} comdat align
class B : A<int> {
     ~B();
   };
   template class A<int>;
   B::~B() {}
 }
 
 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 {
     ~foo();
   };
   foo::~foo() {}
   struct bar : public foo {
     ~bar();

 struct bar {
   ~bar();
 };
 bar::~bar() {}
 struct foo : public bar {
   ~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 {
 template <int>
 struct foo {
   ~foo() { delete this; }
 };
 
 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)
 }

test/CodeGenCXX/destructors.cpp

struct A : Base {
     ~A();
   };
 
   // The function-try-block won't suppress -mconstructor-aliases here.
   A::~A() try { } catch (int i) {}
 
 // 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.]+]]
 // CHECK2: invoke void @_ZN5test04BaseD2Ev
 // 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
 
   struct B : Base, virtual VBase {
     Member M;
     ~B();
   };
namespace test1 {
   struct NonEmpty { int x; }; // trivial destructor, non-empty
 
   // There must be a definition in this translation unit for the alias
   // optimization to apply.
   A::~A() { delete m; }
 
   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
 
   struct Q : A, B { ~Q(); };
   Q::~Q() {} // CHECK3-LABEL: define void @_ZN5test11QD2Ev(%"struct.test1::Q"* %this) unnamed_addr
 
   struct R : A { ~R(); };
   R::~R() { A a; } // CHECK3-LABEL: define void @_ZN5test11RD2Ev(%"struct.test1::R"* %this) unnamed_addr
 
   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
 
   // The VTT parameter prevents this.  We could still make this work
   // for calling conventions that are safe against extra parameters.
   struct U : A, virtual B { ~U(); };
   U::~U() {} // CHECK4-LABEL: define void @_ZN5test11UD2Ev(%"struct.test1::U"* %this, i8** %vtt) unnamed_addr

test/CodeGenCXX/dllexport-alias.cpp

 // RUN: %clang_cc1 -triple x86_64-windows-gnu -mconstructor-aliases %s -S -emit-llvm -o - | FileCheck %s
 
 // This test assumes that the C1 constructor will be aliased to the C2
 // constructor, and the D1 destructor to the D2. It then checks that the aliases
 // are dllexport'ed.
 
 class __declspec(dllexport) A {
 public:
     A();
     ~A();
 };
 
 A::A() {}
 
 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

test/CodeGenCXX/dllexport.cpp

 // M32-DAG: define weak_odr dso_local dllexport x86_thiscallcc void @"??1Z@@UAE@XZ"
 
 namespace UseDtorAlias {
   struct __declspec(dllexport) A { ~A(); };
   struct __declspec(dllexport) B : A { ~B(); };
   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 {
   DefaultedCtorsDtors() = default;
   // M32MSVC2013-DAG: define weak_odr dso_local dllexport x86_thiscallcc %struct.DefaultedCtorsDtors* @"??0DefaultedCtorsDtors@@QAE@XZ"
   ~DefaultedCtorsDtors() = default;
   // M32MSVC2013-DAG: define weak_odr dso_local dllexport x86_thiscallcc void @"??1DefaultedCtorsDtors@@QAE@XZ"
 };

test/CodeGenCXX/microsoft-abi-structors-alias.cpp

struct B : A {
   virtual ~B();
 };
 
 A::~A() {}
 B::~B() {}
 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 {
 struct A { virtual ~A(); };
 A::~A() {}
 }
 // CHECK-DAG: define dso_local x86_thiscallcc void @"??1A@test3@@UAE@XZ"(
 namespace test3 {

test/CodeGenCXX/virtual-bases.cpp

 // RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-apple-darwin10 -mconstructor-aliases | FileCheck %s
 
 struct A { 
   A();
 };
 
-// CHECK: @_ZN1AC1Ev = alias {{.*}} @_ZN1AC2Ev
+// CHECK: @_ZN1AC1Ev = unnamed_addr alias {{.*}} @_ZN1AC2Ev
 // CHECK-LABEL: define void @_ZN1AC2Ev(%struct.A* %this) unnamed_addr
 A::A() { }
 
 struct B : virtual A { 
   B();
 };
 
 // CHECK-LABEL: define void @_ZN1BC2Ev(%struct.B* %this, i8** %vtt) unnamed_addr

test/CodeGenCXX/virtual-destructor-calls.cpp

 // RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-apple-darwin10 -mconstructor-aliases -O1 -disable-llvm-passes | FileCheck %s
 
 struct Member {
   ~Member();
 };
 
 struct A {
   virtual ~A();
 };
 
 struct B : A {
   Member m;
   virtual ~B();
 };
 
 // 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
 // CHECK: call void @_ZN6MemberD1Ev
 // CHECK: call void @_ZN1AD2Ev
 
 // Deleting dtor: defers to the complete dtor.
 // CHECK-LABEL: define void @_ZN1BD0Ev(%struct.B* %this) unnamed_addr