C++1y: Allow aggregates to have default initializers.

Add a CXXDefaultInitExpr, analogous to CXXDefaultArgExpr, and use it both in
CXXCtorInitializers and in InitListExprs to represent a default initializer.

There's an additional complication here: because the default initializer can
refer to the initialized object via its 'this' pointer, we need to make sure
that 'this' points to the right thing within the evaluation.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179958 91177308-0d34-0410-b5e6-96231b3b80d8

37 files changed, 495 insertions, 41 deletions

diff --git a/include/clang/AST/DeclCXX.h b/include/clang/AST/DeclCXX.h
index 5506d211cc..eb6035680b 100644
--- a/include/clang/AST/DeclCXX.h
+++ b/include/clang/AST/DeclCXX.h
@@ -1754,8 +1754,6 @@ class CXXCtorInitializer {
 
   /// \brief The argument used to initialize the base or member, which may
   /// end up constructing an object (when multiple arguments are involved).
-  /// If 0, this is a field initializer, and the in-class member initializer
-  /// will be used.
   Stmt *Init;
 
   /// LParenLoc - Location of the left paren of the ctor-initializer.
@@ -1840,7 +1838,7 @@ public:
   /// implicit ctor initializer generated for a field with an initializer
   /// defined on the member declaration.
   bool isInClassMemberInitializer() const {
-    return !Init;
+    return isa<CXXDefaultInitExpr>(Init);
   }
 
   /// isDelegatingInitializer - Returns true when this initializer is creating
@@ -1967,14 +1965,8 @@ public:
                                getNumArrayIndices());
   }
 
-  /// \brief Get the initializer. This is 0 if this is an in-class initializer
-  /// for a non-static data member which has not yet been parsed.
-  Expr *getInit() const {
-    if (!Init)
-      return getAnyMember()->getInClassInitializer();
-
-    return static_cast<Expr*>(Init);
-  }
+  /// \brief Get the initializer.
+  Expr *getInit() const { return static_cast<Expr*>(Init); }
 };
 
 /// CXXConstructorDecl - Represents a C++ constructor within a
diff --git a/include/clang/AST/ExprCXX.h b/include/clang/AST/ExprCXX.h
index 3189426f9d..91e5b21eac 100644
--- a/include/clang/AST/ExprCXX.h
+++ b/include/clang/AST/ExprCXX.h
@@ -884,6 +884,53 @@ public:
   friend class ASTStmtWriter;
 };
 
+/// \brief This wraps a use of a C++ default initializer (technically,
+/// a brace-or-equal-initializer for a non-static data member) when it
+/// is implicitly used in a mem-initializer-list in a constructor
+/// (C++11 [class.base.init]p8) or in aggregate initialization
+/// (C++1y [dcl.init.aggr]p7).
+class CXXDefaultInitExpr : public Expr {
+  /// \brief The field whose default is being used.
+  FieldDecl *Field;
+
+  /// \brief The location where the default initializer expression was used.
+  SourceLocation Loc;
+
+  CXXDefaultInitExpr(ASTContext &C, SourceLocation Loc, FieldDecl *Field,
+                     QualType T);
+
+  CXXDefaultInitExpr(EmptyShell Empty) : Expr(CXXDefaultInitExprClass, Empty) {}
+
+public:
+  // Field is the non-static data member whose default initializer is used
+  // by this expression.
+  static CXXDefaultInitExpr *Create(ASTContext &C, SourceLocation Loc,
+                                    FieldDecl *Field) {
+    return new (C) CXXDefaultInitExpr(C, Loc, Field, Field->getType());
+  }
+
+  // Get the field whose initializer will be used.
+  FieldDecl *getField() { return Field; }
+  const FieldDecl *getField() const { return Field; }
+
+  // Get the initialization expression that will be used.
+  const Expr *getExpr() const { return Field->getInClassInitializer(); }
+  Expr *getExpr() { return Field->getInClassInitializer(); }
+
+  SourceLocation getLocStart() const LLVM_READONLY { return Loc; }
+  SourceLocation getLocEnd() const LLVM_READONLY { return Loc; }
+
+  static bool classof(const Stmt *T) {
+    return T->getStmtClass() == CXXDefaultInitExprClass;
+  }
+
+  // Iterators
+  child_range children() { return child_range(); }
+
+  friend class ASTReader;
+  friend class ASTStmtReader;
+};
+
 /// CXXTemporary - Represents a C++ temporary.
 class CXXTemporary {
   /// Destructor - The destructor that needs to be called.
diff --git a/include/clang/AST/RecursiveASTVisitor.h b/include/clang/AST/RecursiveASTVisitor.h
index df41b6fa5a..eb5a8123c2 100644
--- a/include/clang/AST/RecursiveASTVisitor.h
+++ b/include/clang/AST/RecursiveASTVisitor.h
@@ -2170,6 +2170,7 @@ DEF_TRAVERSE_STMT(CompoundLiteralExpr, {
 DEF_TRAVERSE_STMT(CXXBindTemporaryExpr, { })
 DEF_TRAVERSE_STMT(CXXBoolLiteralExpr, { })
 DEF_TRAVERSE_STMT(CXXDefaultArgExpr, { })
+DEF_TRAVERSE_STMT(CXXDefaultInitExpr, { })
 DEF_TRAVERSE_STMT(CXXDeleteExpr, { })
 DEF_TRAVERSE_STMT(ExprWithCleanups, { })
 DEF_TRAVERSE_STMT(CXXNullPtrLiteralExpr, { })
diff --git a/include/clang/Basic/StmtNodes.td b/include/clang/Basic/StmtNodes.td
index ad25e57c89..cbfce83c4b 100644
--- a/include/clang/Basic/StmtNodes.td
+++ b/include/clang/Basic/StmtNodes.td
@@ -108,6 +108,7 @@ def CXXNullPtrLiteralExpr : DStmt<Expr>;
 def CXXThisExpr : DStmt<Expr>;
 def CXXThrowExpr : DStmt<Expr>;
 def CXXDefaultArgExpr : DStmt<Expr>;
+def CXXDefaultInitExpr : DStmt<Expr>;
 def CXXScalarValueInitExpr : DStmt<Expr>;
 def CXXNewExpr : DStmt<Expr>;
 def CXXDeleteExpr : DStmt<Expr>;
diff --git a/include/clang/Serialization/ASTBitCodes.h b/include/clang/Serialization/ASTBitCodes.h
index 9f5e8b1224..81f8980425 100644
--- a/include/clang/Serialization/ASTBitCodes.h
+++ b/include/clang/Serialization/ASTBitCodes.h
@@ -1267,6 +1267,7 @@ namespace clang {
       EXPR_CXX_THIS,              // CXXThisExpr
       EXPR_CXX_THROW,             // CXXThrowExpr
       EXPR_CXX_DEFAULT_ARG,       // CXXDefaultArgExpr
+      EXPR_CXX_DEFAULT_INIT,      // CXXDefaultInitExpr
       EXPR_CXX_BIND_TEMPORARY,    // CXXBindTemporaryExpr
 
       EXPR_CXX_SCALAR_VALUE_INIT, // CXXScalarValueInitExpr
diff --git a/lib/AST/DeclCXX.cpp b/lib/AST/DeclCXX.cpp
index 2c7c4d335d..ece831571c 100644
--- a/lib/AST/DeclCXX.cpp
+++ b/lib/AST/DeclCXX.cpp
@@ -505,7 +505,7 @@ void CXXRecordDecl::addedMember(Decl *D) {
     // C++ [dcl.init.aggr]p1:
     //   An aggregate is an array or a class with no user-declared
     //   constructors [...].
-    // C++0x [dcl.init.aggr]p1:
+    // C++11 [dcl.init.aggr]p1:
     //   An aggregate is an array or a class with no user-provided
     //   constructors [...].
     if (getASTContext().getLangOpts().CPlusPlus11
@@ -690,7 +690,10 @@ void CXXRecordDecl::addedMember(Decl *D) {
       // C++11 [dcl.init.aggr]p1:
       //   An aggregate is a [...] class with [...] no
       //   brace-or-equal-initializers for non-static data members.
-      data().Aggregate = false;
+      //
+      // This rule was removed in C++1y.
+      if (!getASTContext().getLangOpts().CPlusPlus1y)
+        data().Aggregate = false;
 
       // C++11 [class]p10:
       //   A POD struct is [...] a trivial class.
diff --git a/lib/AST/DeclPrinter.cpp b/lib/AST/DeclPrinter.cpp
index 995925350c..bcc4e3865a 100644
--- a/lib/AST/DeclPrinter.cpp
+++ b/lib/AST/DeclPrinter.cpp
@@ -487,7 +487,7 @@ void DeclPrinter::VisitFunctionDecl(FunctionDecl *D) {
       for (CXXConstructorDecl::init_const_iterator B = CDecl->init_begin(),
            E = CDecl->init_end();
            B != E; ++B) {
-        CXXCtorInitializer * BMInitializer = (*B);
+        CXXCtorInitializer *BMInitializer = (*B);
         if (BMInitializer->isInClassMemberInitializer())
           continue;
 
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 748d3084fe..1303fb0cee 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -100,11 +100,20 @@ Expr::skipRValueSubobjectAdjustments(
 const Expr *
 Expr::findMaterializedTemporary(const MaterializeTemporaryExpr *&MTE) const {
   const Expr *E = this;
+
+  // This might be a default initializer for a reference member. Walk over the
+  // wrapper node for that.
+  if (const CXXDefaultInitExpr *DAE = dyn_cast<CXXDefaultInitExpr>(E))
+    E = DAE->getExpr();
+
   // Look through single-element init lists that claim to be lvalues. They're
   // just syntactic wrappers in this case.
   if (const InitListExpr *ILE = dyn_cast<InitListExpr>(E)) {
-    if (ILE->getNumInits() == 1 && ILE->isGLValue())
+    if (ILE->getNumInits() == 1 && ILE->isGLValue()) {
       E = ILE->getInit(0);
+      if (const CXXDefaultInitExpr *DAE = dyn_cast<CXXDefaultInitExpr>(E))
+        E = DAE->getExpr();
+    }
   }
 
   // Look through expressions for materialized temporaries (for now).
@@ -2174,6 +2183,9 @@ bool Expr::isUnusedResultAWarning(const Expr *&WarnE, SourceLocation &Loc,
   case CXXDefaultArgExprClass:
     return (cast<CXXDefaultArgExpr>(this)
             ->getExpr()->isUnusedResultAWarning(WarnE, Loc, R1, R2, Ctx));
+  case CXXDefaultInitExprClass:
+    return (cast<CXXDefaultInitExpr>(this)
+            ->getExpr()->isUnusedResultAWarning(WarnE, Loc, R1, R2, Ctx));
 
   case CXXNewExprClass:
     // FIXME: In theory, there might be new expressions that don't have side
@@ -2851,6 +2863,12 @@ bool Expr::HasSideEffects(const ASTContext &Ctx) const {
   case CXXDefaultArgExprClass:
     return cast<CXXDefaultArgExpr>(this)->getExpr()->HasSideEffects(Ctx);
 
+  case CXXDefaultInitExprClass:
+    if (const Expr *E = cast<CXXDefaultInitExpr>(this)->getExpr())
+      return E->HasSideEffects(Ctx);
+    // If we've not yet parsed the initializer, assume it has side-effects.
+    return true;
+
   case CXXDynamicCastExprClass: {
     // A dynamic_cast expression has side-effects if it can throw.
     const CXXDynamicCastExpr *DCE = cast<CXXDynamicCastExpr>(this);
@@ -3038,8 +3056,12 @@ Expr::isNullPointerConstant(ASTContext &Ctx,
     return GE->getResultExpr()->isNullPointerConstant(Ctx, NPC);
   } else if (const CXXDefaultArgExpr *DefaultArg
                = dyn_cast<CXXDefaultArgExpr>(this)) {
-    // See through default argument expressions
+    // See through default argument expressions.
     return DefaultArg->getExpr()->isNullPointerConstant(Ctx, NPC);
+  } else if (const CXXDefaultInitExpr *DefaultInit
+               = dyn_cast<CXXDefaultInitExpr>(this)) {
+    // See through default initializer expressions.
+    return DefaultInit->getExpr()->isNullPointerConstant(Ctx, NPC);
   } else if (isa<GNUNullExpr>(this)) {
     // The GNU __null extension is always a null pointer constant.
     return NPCK_GNUNull;
diff --git a/lib/AST/ExprCXX.cpp b/lib/AST/ExprCXX.cpp
index 12a47fcd78..277c8c09a5 100644
--- a/lib/AST/ExprCXX.cpp
+++ b/lib/AST/ExprCXX.cpp
@@ -704,6 +704,17 @@ CXXDefaultArgExpr::Create(ASTContext &C, SourceLocation Loc,
                                      SubExpr);
 }
 
+CXXDefaultInitExpr::CXXDefaultInitExpr(ASTContext &C, SourceLocation Loc,
+                                       FieldDecl *Field, QualType T)
+    : Expr(CXXDefaultInitExprClass, T.getNonLValueExprType(C),
+           T->isLValueReferenceType() ? VK_LValue : T->isRValueReferenceType()
+                                                        ? VK_XValue
+                                                        : VK_RValue,
+           /*FIXME*/ OK_Ordinary, false, false, false, false),
+      Field(Field), Loc(Loc) {
+  assert(Field->hasInClassInitializer());
+}
+
 CXXTemporary *CXXTemporary::Create(ASTContext &C,
                                    const CXXDestructorDecl *Destructor) {
   return new (C) CXXTemporary(Destructor);
diff --git a/lib/AST/ExprClassification.cpp b/lib/AST/ExprClassification.cpp
index c2a35f42c1..bcb6d4e809 100644
--- a/lib/AST/ExprClassification.cpp
+++ b/lib/AST/ExprClassification.cpp
@@ -298,6 +298,10 @@ static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
   case Expr::CXXDefaultArgExprClass:
     return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
 
+    // Same idea for default initializers.
+  case Expr::CXXDefaultInitExprClass:
+    return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
+
     // Same idea for temporary binding.
   case Expr::CXXBindTemporaryExprClass:
     return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 3675b2ff44..4e468806dc 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -301,6 +301,22 @@ namespace {
     ~CallStackFrame();
   };
 
+  /// Temporarily override 'this'.
+  class ThisOverrideRAII {
+  public:
+    ThisOverrideRAII(CallStackFrame &Frame, const LValue *NewThis, bool Enable)
+        : Frame(Frame), OldThis(Frame.This) {
+      if (Enable)
+        Frame.This = NewThis;
+    }
+    ~ThisOverrideRAII() {
+      Frame.This = OldThis;
+    }
+  private:
+    CallStackFrame &Frame;
+    const LValue *OldThis;
+  };
+
   /// A partial diagnostic which we might know in advance that we are not going
   /// to emit.
   class OptionalDiagnostic {
@@ -2397,6 +2413,8 @@ public:
     { return StmtVisitorTy::Visit(E->getReplacement()); }
   RetTy VisitCXXDefaultArgExpr(const CXXDefaultArgExpr *E)
     { return StmtVisitorTy::Visit(E->getExpr()); }
+  RetTy VisitCXXDefaultInitExpr(const CXXDefaultInitExpr *E)
+    { return StmtVisitorTy::Visit(E->getExpr()); }
   // We cannot create any objects for which cleanups are required, so there is
   // nothing to do here; all cleanups must come from unevaluated subexpressions.
   RetTy VisitExprWithCleanups(const ExprWithCleanups *E)
@@ -3398,12 +3416,20 @@ bool RecordExprEvaluator::VisitInitListExpr(const InitListExpr *E) {
 
     // If the initializer list for a union does not contain any elements, the
     // first element of the union is value-initialized.
+    // FIXME: The element should be initialized from an initializer list.
+    //        Is this difference ever observable for initializer lists which
+    //        we don't build?
     ImplicitValueInitExpr VIE(Field->getType());
     const Expr *InitExpr = E->getNumInits() ? E->getInit(0) : &VIE;
 
     LValue Subobject = This;
     if (!HandleLValueMember(Info, InitExpr, Subobject, Field, &Layout))
       return false;
+
+    // Temporarily override This, in case there's a CXXDefaultInitExpr in here.
+    ThisOverrideRAII ThisOverride(*Info.CurrentCall, &This,
+                                  isa<CXXDefaultInitExpr>(InitExpr));
+
     return EvaluateInPlace(Result.getUnionValue(), Info, Subobject, InitExpr);
   }
 
@@ -3433,10 +3459,14 @@ bool RecordExprEvaluator::VisitInitListExpr(const InitListExpr *E) {
     // Perform an implicit value-initialization for members beyond the end of
     // the initializer list.
     ImplicitValueInitExpr VIE(HaveInit ? Info.Ctx.IntTy : Field->getType());
+    const Expr *Init = HaveInit ? E->getInit(ElementNo++) : &VIE;
 
-    if (!EvaluateInPlace(
-          Result.getStructField(Field->getFieldIndex()),
-          Info, Subobject, HaveInit ? E->getInit(ElementNo++) : &VIE)) {
+    // Temporarily override This, in case there's a CXXDefaultInitExpr in here.
+    ThisOverrideRAII ThisOverride(*Info.CurrentCall, &This,
+                                  isa<CXXDefaultInitExpr>(Init));
+
+    if (!EvaluateInPlace(Result.getStructField(Field->getFieldIndex()), Info,
+                         Subobject, Init)) {
       if (!Info.keepEvaluatingAfterFailure())
         return false;
       Success = false;
@@ -6807,6 +6837,8 @@ static ICEDiag CheckICE(const Expr* E, ASTContext &Ctx) {
   }
   case Expr::CXXDefaultArgExprClass:
     return CheckICE(cast<CXXDefaultArgExpr>(E)->getExpr(), Ctx);
+  case Expr::CXXDefaultInitExprClass:
+    return CheckICE(cast<CXXDefaultInitExpr>(E)->getExpr(), Ctx);
   case Expr::ChooseExprClass: {
     return CheckICE(cast<ChooseExpr>(E)->getChosenSubExpr(Ctx), Ctx);
   }
diff --git a/lib/AST/ItaniumMangle.cpp b/lib/AST/ItaniumMangle.cpp
index e82b017e4a..0b77933f0b 100644
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@@ -2473,6 +2473,10 @@ recurse:
     mangleExpression(cast<CXXDefaultArgExpr>(E)->getExpr(), Arity);
     break;
 
+  case Expr::CXXDefaultInitExprClass:
+    mangleExpression(cast<CXXDefaultInitExpr>(E)->getExpr(), Arity);
+    break;
+
   case Expr::SubstNonTypeTemplateParmExprClass:
     mangleExpression(cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement(),
                      Arity);
diff --git a/lib/AST/StmtPrinter.cpp b/lib/AST/StmtPrinter.cpp
index 1b2285c794..95bacb64b3 100644
--- a/lib/AST/StmtPrinter.cpp
+++ b/lib/AST/StmtPrinter.cpp
@@ -1314,7 +1314,11 @@ void StmtPrinter::VisitCXXThrowExpr(CXXThrowExpr *Node) {
 }
 
 void StmtPrinter::VisitCXXDefaultArgExpr(CXXDefaultArgExpr *Node) {
-  // Nothing to print: we picked up the default argument
+  // Nothing to print: we picked up the default argument.
+}
+
+void StmtPrinter::VisitCXXDefaultInitExpr(CXXDefaultInitExpr *Node) {
+  // Nothing to print: we picked up the default initializer.
 }
 
 void StmtPrinter::VisitCXXFunctionalCastExpr(CXXFunctionalCastExpr *Node) {
diff --git a/lib/AST/StmtProfile.cpp b/lib/AST/StmtProfile.cpp
index d99400c603..8ade242d56 100644
--- a/lib/AST/StmtProfile.cpp
+++ b/lib/AST/StmtProfile.cpp
@@ -789,6 +789,11 @@ void StmtProfiler::VisitCXXDefaultArgExpr(const CXXDefaultArgExpr *S) {
   VisitDecl(S->getParam());
 }
 
+void StmtProfiler::VisitCXXDefaultInitExpr(const CXXDefaultInitExpr *S) {
+  VisitExpr(S);
+  VisitDecl(S->getField());
+}
+
 void StmtProfiler::VisitCXXBindTemporaryExpr(const CXXBindTemporaryExpr *S) {
   VisitExpr(S);
   VisitDecl(
diff --git a/lib/Analysis/CFG.cpp b/lib/Analysis/CFG.cpp
index 1adb8b84e4..096c7a080b 100644
--- a/lib/Analysis/CFG.cpp
+++ b/lib/Analysis/CFG.cpp
@@ -1085,11 +1085,16 @@ CFGBlock *CFGBuilder::Visit(Stmt * S, AddStmtChoice asc) {
       return VisitExprWithCleanups(cast<ExprWithCleanups>(S), asc);
 
     case Stmt::CXXDefaultArgExprClass:
+    case Stmt::CXXDefaultInitExprClass:
       // FIXME: The expression inside a CXXDefaultArgExpr is owned by the
       // called function's declaration, not by the caller. If we simply add
       // this expression to the CFG, we could end up with the same Expr
       // appearing multiple times.
       // PR13385 / <rdar://problem/12156507>
+      //
+      // It's likewise possible for multiple CXXDefaultInitExprs for the same
+      // expression to be used in the same function (through aggregate
+      // initialization).
       return VisitStmt(S, asc);
 
     case Stmt::CXXBindTemporaryExprClass:
diff --git a/lib/CodeGen/CGClass.cpp b/lib/CodeGen/CGClass.cpp
index 05925567b0..2b9a55b2a6 100644
--- a/lib/CodeGen/CGClass.cpp
+++ b/lib/CodeGen/CGClass.cpp
@@ -1139,6 +1139,7 @@ void CodeGenFunction::EmitCtorPrologue(const CXXConstructorDecl *CD,
   InitializeVTablePointers(ClassDecl);
 
   // And finally, initialize class members.
+  FieldConstructionScope FCS(*this, CXXThisValue);
   ConstructorMemcpyizer CM(*this, CD, Args);
   for (; B != E; B++) {
     CXXCtorInitializer *Member = (*B);
diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index a0725b5f9c..ea13de17ab 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -903,6 +903,10 @@ LValue CodeGenFunction::EmitLValue(const Expr *E) {
     return EmitNullInitializationLValue(cast<CXXScalarValueInitExpr>(E));
   case Expr::CXXDefaultArgExprClass:
     return EmitLValue(cast<CXXDefaultArgExpr>(E)->getExpr());
+  case Expr::CXXDefaultInitExprClass: {
+    CXXDefaultInitExprScope Scope(*this);
+    return EmitLValue(cast<CXXDefaultInitExpr>(E)->getExpr());
+  }
   case Expr::CXXTypeidExprClass:
     return EmitCXXTypeidLValue(cast<CXXTypeidExpr>(E));
 
diff --git a/lib/CodeGen/CGExprAgg.cpp b/lib/CodeGen/CGExprAgg.cpp
index 6b29b3155a..b974e1dcc6 100644
--- a/lib/CodeGen/CGExprAgg.cpp
+++ b/lib/CodeGen/CGExprAgg.cpp
@@ -170,6 +170,10 @@ public:
   void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
     Visit(DAE->getExpr());
   }
+  void VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
+    CodeGenFunction::CXXDefaultInitExprScope Scope(CGF);
+    Visit(DIE->getExpr());
+  }
   void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
   void VisitCXXConstructExpr(const CXXConstructExpr *E);
   void VisitLambdaExpr(LambdaExpr *E);
@@ -1189,7 +1193,10 @@ void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
   // the optimizer, especially with bitfields.
   unsigned NumInitElements = E->getNumInits();
   RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
-  
+
+  // Prepare a 'this' for CXXDefaultInitExprs.
+  CodeGenFunction::FieldConstructionScope FCS(CGF, Dest.getAddr());
+
   if (record->isUnion()) {
     // Only initialize one field of a union. The field itself is
     // specified by the initializer list.
diff --git a/lib/CodeGen/CGExprComplex.cpp b/lib/CodeGen/CGExprComplex.cpp
index 5fc73aa790..36f974a313 100644
--- a/lib/CodeGen/CGExprComplex.cpp
+++ b/lib/CodeGen/CGExprComplex.cpp
@@ -182,6 +182,10 @@ public:
   ComplexPairTy VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
     return Visit(DAE->getExpr());
   }
+  ComplexPairTy VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
+    CodeGenFunction::CXXDefaultInitExprScope Scope(CGF);
+    return Visit(DIE->getExpr());
+  }
   ComplexPairTy VisitExprWithCleanups(ExprWithCleanups *E) {
     CGF.enterFullExpression(E);
     CodeGenFunction::RunCleanupsScope Scope(CGF);
diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index faaf6468f1..f5c8187c26 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -757,6 +757,12 @@ public:
     return Visit(DAE->getExpr());
   }
 
+  llvm::Constant *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
+    // No need for a DefaultInitExprScope: we don't handle 'this' in a
+    // constant expression.
+    return Visit(DIE->getExpr());
+  }
+
   llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) {
     return Visit(E->GetTemporaryExpr());
   }
diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index ea1eae8088..c1c252d12b 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -344,6 +344,10 @@ public:
   Value *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
     return Visit(DAE->getExpr());
   }
+  Value *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
+    CodeGenFunction::CXXDefaultInitExprScope Scope(CGF);
+    return Visit(DIE->getExpr());
+  }
   Value *VisitCXXThisExpr(CXXThisExpr *TE) {
     return CGF.LoadCXXThis();
   }
diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index cda3ce0286..a12e7dc445 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -45,6 +45,7 @@ CodeGenFunction::CodeGenFunction(CodeGenModule &cgm, bool suppressNewContext)
     DidCallStackSave(false),
     IndirectBranch(0), SwitchInsn(0), CaseRangeBlock(0), UnreachableBlock(0),
     CXXABIThisDecl(0), CXXABIThisValue(0), CXXThisValue(0),
+    CXXDefaultInitExprThis(0),
     CXXStructorImplicitParamDecl(0), CXXStructorImplicitParamValue(0),
     OutermostConditional(0), CurLexicalScope(0), TerminateLandingPad(0),
     TerminateHandler(0), TrapBB(0) {
diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index 6e2d62760f..f0c2c1e672 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -1206,12 +1206,53 @@ private:
   /// lazily by getUnreachableBlock().
   llvm::BasicBlock *UnreachableBlock;
 
+public:
+  /// A scope within which we are constructing the fields of an object which
+  /// might use a CXXDefaultInitExpr. This stashes away a 'this' value to use
+  /// if we need to evaluate a CXXDefaultInitExpr within the evaluation.
+  class FieldConstructionScope {
+  public:
+    FieldConstructionScope(CodeGenFunction &CGF, llvm::Value *This)
+        : CGF(CGF), OldCXXDefaultInitExprThis(CGF.CXXDefaultInitExprThis) {
+      CGF.CXXDefaultInitExprThis = This;
+    }
+    ~FieldConstructionScope() {
+      CGF.CXXDefaultInitExprThis = OldCXXDefaultInitExprThis;
+    }
+
+  private:
+    CodeGenFunction &CGF;
+    llvm::Value *OldCXXDefaultInitExprThis;
+  };
+
+  /// The scope of a CXXDefaultInitExpr. Within this scope, the value of 'this'
+  /// is overridden to be the object under construction.
+  class CXXDefaultInitExprScope {
+  public:
+    CXXDefaultInitExprScope(CodeGenFunction &CGF)
+        : CGF(CGF), OldCXXThisValue(CGF.CXXThisValue) {
+      CGF.CXXThisValue = CGF.CXXDefaultInitExprThis;
+    }
+    ~CXXDefaultInitExprScope() {
+      CGF.CXXThisValue = OldCXXThisValue;
+    }
+
+  public:
+    CodeGenFunction &CGF;
+    llvm::Value *OldCXXThisValue;
+  };
+
+private:
   /// CXXThisDecl - When generating code for a C++ member function,
   /// this will hold the implicit 'this' declaration.
   ImplicitParamDecl *CXXABIThisDecl;
   llvm::Value *CXXABIThisValue;
   llvm::Value *CXXThisValue;
 
+  /// The value of 'this' to use when evaluating CXXDefaultInitExprs within
+  /// this expression.
+  llvm::Value *CXXDefaultInitExprThis;
+
   /// CXXStructorImplicitParamDecl - When generating code for a