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.

llvm-svn: 179958

8 files changed, 69 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGClass.cpp b/clang/lib/CodeGen/CGClass.cpp
index 05925567b0b..2b9a55b2a69 100644
--- a/clang/lib/CodeGen/CGClass.cpp
+++ b/clang/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/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index a0725b5f9cd..ea13de17abb 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/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/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index 6b29b3155aa..b974e1dcc68 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/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/clang/lib/CodeGen/CGExprComplex.cpp b/clang/lib/CodeGen/CGExprComplex.cpp
index 5fc73aa7901..36f974a3132 100644
--- a/clang/lib/CodeGen/CGExprComplex.cpp
+++ b/clang/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/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index faaf6468f1e..f5c8187c26f 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/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/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index ea1eae80887..c1c252d12b7 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/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/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index cda3ce0286d..a12e7dc445d 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/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/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 6e2d62760f5..f0c2c1e6725 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/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 constructor or
   /// destructor, this will hold the implicit argument (e.g. VTT).
   ImplicitParamDecl *CXXStructorImplicitParamDecl;