AST: Mangle reference temporaries reliably

Summary:
Previously, we would generate a single name for all reference
temporaries and allow LLVM to rename them for us.  Instead, number the
reference temporaries as we build them in Sema.

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D3554

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@207776 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/ExprCXX.h

@@ -3784,39 +3784,51 @@ class FunctionParmPackExpr : public Expr {
 /// temporary. When either happens, the expression will also track the
 /// declaration which is responsible for the lifetime extension.
 class MaterializeTemporaryExpr : public Expr {
-public:
-  /// \brief The temporary-generating expression whose value will be
-  /// materialized.
-  Stmt *Temporary;
+private:
+  struct ExtraState {
+    /// \brief The temporary-generating expression whose value will be
+    /// materialized.
+    Stmt *Temporary;
 
-  /// \brief The declaration which lifetime-extended this reference, if any.
-  /// Either a VarDecl, or (for a ctor-initializer) a FieldDecl.
-  const ValueDecl *ExtendingDecl;
+    /// \brief The declaration which lifetime-extended this reference, if any.
+    /// Either a VarDecl, or (for a ctor-initializer) a FieldDecl.
+    const ValueDecl *ExtendingDecl;
+
+    unsigned ManglingNumber;
+  };
+  llvm::PointerUnion<Stmt *, ExtraState *> State;
 
   friend class ASTStmtReader;
   friend class ASTStmtWriter;
 
+  void initializeExtraState(const ValueDecl *ExtendedBy,
+                            unsigned ManglingNumber);
+
 public:
   MaterializeTemporaryExpr(QualType T, Expr *Temporary,
-                           bool BoundToLvalueReference,
-                           const ValueDecl *ExtendedBy)
+                           bool BoundToLvalueReference)
     : Expr(MaterializeTemporaryExprClass, T,
            BoundToLvalueReference? VK_LValue : VK_XValue, OK_Ordinary,
            Temporary->isTypeDependent(), Temporary->isValueDependent(),
            Temporary->isInstantiationDependent(),
            Temporary->containsUnexpandedParameterPack()),
-      Temporary(Temporary), ExtendingDecl(ExtendedBy) {
-  }
+        State(Temporary) {}
 
   MaterializeTemporaryExpr(EmptyShell Empty)
     : Expr(MaterializeTemporaryExprClass, Empty) { }
 
+  Stmt *getTemporary() const {
+    return State.is<Stmt *>() ? State.get<Stmt *>()
+                              : State.get<ExtraState *>()->Temporary;
+  }
+
   /// \brief Retrieve the temporary-generating subexpression whose value will
   /// be materialized into a glvalue.
-  Expr *GetTemporaryExpr() const { return static_cast<Expr *>(Temporary); }
+  Expr *GetTemporaryExpr() const { return static_cast<Expr *>(getTemporary()); }
 
   /// \brief Retrieve the storage duration for the materialized temporary.
   StorageDuration getStorageDuration() const {
+    const ValueDecl *ExtendingDecl = getExtendingDecl();
     if (!ExtendingDecl)
       return SD_FullExpression;
     // FIXME: This is not necessarily correct for a temporary materialized
@@ -3828,10 +3840,15 @@ class MaterializeTemporaryExpr : public Expr {
 
   /// \brief Get the declaration which triggered the lifetime-extension of this
   /// temporary, if any.
-  const ValueDecl *getExtendingDecl() const { return ExtendingDecl; }
+  const ValueDecl *getExtendingDecl() const {
+    return State.is<Stmt *>() ? nullptr
+                              : State.get<ExtraState *>()->ExtendingDecl;
+  }
+
+  void setExtendingDecl(const ValueDecl *ExtendedBy, unsigned ManglingNumber);
 
-  void setExtendingDecl(const ValueDecl *ExtendedBy) {
-    ExtendingDecl = ExtendedBy;
+  unsigned getManglingNumber() const {
+    return State.is<Stmt *>() ? 0 : State.get<ExtraState *>()->ManglingNumber;
   }
 
   /// \brief Determine whether this materialized temporary is bound to an
@@ -3841,18 +3858,24 @@ class MaterializeTemporaryExpr : public Expr {
   }
 
   SourceLocation getLocStart() const LLVM_READONLY {
-    return Temporary->getLocStart();
+    return getTemporary()->getLocStart();
   }
   SourceLocation getLocEnd() const LLVM_READONLY {
-    return Temporary->getLocEnd();
+    return getTemporary()->getLocEnd();
   }
 
   static bool classof(const Stmt *T) {
     return T->getStmtClass() == MaterializeTemporaryExprClass;
   }
 
   // Iterators
-  child_range children() { return child_range(&Temporary, &Temporary + 1); }
+  child_range children() {
+    if (State.is<Stmt *>())
+      return child_range(State.getAddrOfPtr1(), State.getAddrOfPtr1() + 1);
+
+    auto ES = State.get<ExtraState *>();
+    return child_range(&ES->Temporary, &ES->Temporary + 1);
+  }
 };
 
 }  // end namespace clang

include/clang/AST/Mangle.h

@@ -130,6 +130,7 @@ class MangleContext {
                                   const ThisAdjustment &ThisAdjustment,
                                   raw_ostream &) = 0;
   virtual void mangleReferenceTemporary(const VarDecl *D,
+                                        unsigned ManglingNumber,
                                         raw_ostream &) = 0;
   virtual void mangleCXXRTTI(QualType T, raw_ostream &) = 0;
   virtual void mangleCXXRTTIName(QualType T, raw_ostream &) = 0;

include/clang/Sema/Initialization.h

@@ -103,6 +103,9 @@ class InitializedEntity {
   /// \brief The type of the object or reference being initialized.
   QualType Type;
 
+  /// \brief The mangling number for the next reference temporary to be created.
+  mutable unsigned ManglingNumber;
+
   struct LN {
     /// \brief When Kind == EK_Result, EK_Exception, EK_New, the
     /// location of the 'return', 'throw', or 'new' keyword,
@@ -155,19 +158,19 @@ class InitializedEntity {
     struct C Capture;
   };
 
-  InitializedEntity() { }
+  InitializedEntity() : ManglingNumber(0) {}
 
   /// \brief Create the initialization entity for a variable.
   InitializedEntity(VarDecl *Var)
-    : Kind(EK_Variable), Parent(0), Type(Var->getType()),
+    : Kind(EK_Variable), Parent(0), Type(Var->getType()), ManglingNumber(0),
       VariableOrMember(Var) { }
 
   /// \brief Create the initialization entity for the result of a
   /// function, throwing an object, performing an explicit cast, or
   /// initializing a parameter for which there is no declaration.
   InitializedEntity(EntityKind Kind, SourceLocation Loc, QualType Type,
                     bool NRVO = false)
-    : Kind(Kind), Parent(0), Type(Type)
+    : Kind(Kind), Parent(0), Type(Type), ManglingNumber(0)
   {
     LocAndNRVO.Location = Loc.getRawEncoding();
     LocAndNRVO.NRVO = NRVO;
@@ -176,15 +179,15 @@ class InitializedEntity {
   /// \brief Create the initialization entity for a member subobject.
   InitializedEntity(FieldDecl *Member, const InitializedEntity *Parent) 
     : Kind(EK_Member), Parent(Parent), Type(Member->getType()),
-      VariableOrMember(Member) { }
+      ManglingNumber(0), VariableOrMember(Member) { }
 
   /// \brief Create the initialization entity for an array element.
   InitializedEntity(ASTContext &Context, unsigned Index, 
                     const InitializedEntity &Parent);
 
   /// \brief Create the initialization entity for a lambda capture.
   InitializedEntity(IdentifierInfo *VarID, QualType FieldType, SourceLocation Loc)
-    : Kind(EK_LambdaCapture), Parent(0), Type(FieldType) 
+    : Kind(EK_LambdaCapture), Parent(0), Type(FieldType), ManglingNumber(0)
   {
     Capture.VarID = VarID;
     Capture.Location = Loc.getRawEncoding();
@@ -418,6 +421,8 @@ class InitializedEntity {
     Kind = EK_Parameter_CF_Audited;
   }
 
+  unsigned allocateManglingNumber() const { return ++ManglingNumber; }
+
   /// Dump a representation of the initialized entity to standard error,
   /// for debugging purposes.
   void dump() const;

lib/AST/ExprCXX.cpp

@@ -1446,6 +1446,25 @@ FunctionParmPackExpr::CreateEmpty(const ASTContext &Context,
     FunctionParmPackExpr(QualType(), 0, SourceLocation(), 0, 0);
 }
 
+void MaterializeTemporaryExpr::setExtendingDecl(const ValueDecl *ExtendedBy,
+                                                unsigned ManglingNumber) {
+  // We only need extra state if we have to remember more than just the Stmt.
+  if (!ExtendedBy)
+    return;
+
+  // We may need to allocate extra storage for the mangling number and the
+  // extended-by ValueDecl.
+  if (!State.is<ExtraState *>()) {
+    auto ES = new (ExtendedBy->getASTContext()) ExtraState;
+    ES->Temporary = State.get<Stmt *>();
+    State = ES;
+  }
+
+  auto ES = State.get<ExtraState *>();
+  ES->ExtendingDecl = ExtendedBy;
+  ES->ManglingNumber = ManglingNumber;
+}
+
 TypeTraitExpr::TypeTraitExpr(QualType T, SourceLocation Loc, TypeTrait Kind,
                              ArrayRef<TypeSourceInfo *> Args,
                              SourceLocation RParenLoc,

lib/AST/ItaniumMangle.cpp

@@ -136,7 +136,8 @@ class ItaniumMangleContextImpl : public ItaniumMangleContext {
   void mangleCXXDtorThunk(const CXXDestructorDecl *DD, CXXDtorType Type,
                           const ThisAdjustment &ThisAdjustment,
                           raw_ostream &) override;
-  void mangleReferenceTemporary(const VarDecl *D, raw_ostream &) override;
+  void mangleReferenceTemporary(const VarDecl *D, unsigned ManglingNumber,
+                                raw_ostream &) override;
   void mangleCXXVTable(const CXXRecordDecl *RD, raw_ostream &) override;
   void mangleCXXVTT(const CXXRecordDecl *RD, raw_ostream &) override;
   void mangleCXXCtorVTable(const CXXRecordDecl *RD, int64_t Offset,
@@ -3782,12 +3783,16 @@ ItaniumMangleContextImpl::mangleItaniumThreadLocalWrapper(const VarDecl *D,
 }
 
 void ItaniumMangleContextImpl::mangleReferenceTemporary(const VarDecl *D,
+                                                        unsigned ManglingNumber,
                                                         raw_ostream &Out) {
   // We match the GCC mangling here.
   //  <special-name> ::= GR <object name>
   CXXNameMangler Mangler(*this, Out);
   Mangler.getStream() << "_ZGR";
   Mangler.mangleName(D);
+  assert(ManglingNumber > 0 && "Reference temporary mangling number is zero!");
+  if (ManglingNumber > 1)
+    Mangler.mangleNumber(ManglingNumber - 2);
 }
 
 void ItaniumMangleContextImpl::mangleCXXVTable(const CXXRecordDecl *RD,

lib/AST/MicrosoftMangle.cpp

@@ -117,7 +117,8 @@ class MicrosoftMangleContextImpl : public MicrosoftMangleContext {
                      raw_ostream &) override;
   void mangleCXXDtor(const CXXDestructorDecl *D, CXXDtorType Type,
                      raw_ostream &) override;
-  void mangleReferenceTemporary(const VarDecl *, raw_ostream &) override;
+  void mangleReferenceTemporary(const VarDecl *, unsigned ManglingNumber,
+                                raw_ostream &) override;
   void mangleStaticGuardVariable(const VarDecl *D, raw_ostream &Out) override;
   void mangleDynamicInitializer(const VarDecl *D, raw_ostream &Out) override;
   void mangleDynamicAtExitDestructor(const VarDecl *D,
@@ -2267,6 +2268,7 @@ void MicrosoftMangleContextImpl::mangleCXXDtor(const CXXDestructorDecl *D,
 }
 
 void MicrosoftMangleContextImpl::mangleReferenceTemporary(const VarDecl *VD,
+                                                          unsigned,
                                                           raw_ostream &) {
   unsigned DiagID = getDiags().getCustomDiagID(DiagnosticsEngine::Error,
     "cannot mangle this reference temporary yet");

lib/CodeGen/CodeGenModule.cpp

@@ -2828,7 +2828,8 @@ llvm::Constant *CodeGenModule::GetAddrOfGlobalTemporary(
   // we also need to make the temporaries externally-visible).
   SmallString<256> Name;
   llvm::raw_svector_ostream Out(Name);
-  getCXXABI().getMangleContext().mangleReferenceTemporary(VD, Out);
+  getCXXABI().getMangleContext().mangleReferenceTemporary(
+      VD, E->getManglingNumber(), Out);
   Out.flush();
 
   APValue *Value = 0;

lib/Sema/SemaCast.cpp

@@ -1584,8 +1584,7 @@ static TryCastResult TryConstCast(Sema &Self, ExprResult &SrcExpr,
     // This is a const_cast from a class prvalue to an rvalue reference type.
     // Materialize a temporary to store the result of the conversion.
     SrcExpr = new (Self.Context) MaterializeTemporaryExpr(
-        SrcType, SrcExpr.take(), /*IsLValueReference*/ false,
-        /*ExtendingDecl*/ 0);
+        SrcType, SrcExpr.take(), /*IsLValueReference*/ false);
 
   return TC_Success;
 }

lib/Sema/SemaExpr.cpp

@@ -8885,7 +8885,7 @@ QualType Sema::CheckAddressOfOperand(ExprResult &OrigOp, SourceLocation OpLoc) {
       return QualType();
     // Materialize the temporary as an lvalue so that we can take its address.
     OrigOp = op = new (Context)
-        MaterializeTemporaryExpr(op->getType(), OrigOp.take(), true, 0);
+        MaterializeTemporaryExpr(op->getType(), OrigOp.take(), true);
   } else if (isa<ObjCSelectorExpr>(op)) {
     return Context.getPointerType(op->getType());
   } else if (lval == Expr::LV_MemberFunction) {