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

1 files changed, 41 insertions, 0 deletions

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;