diff --git a/include/clang/AST/Expr.h b/include/clang/AST/Expr.h
index 10b877ac89..c6ac007a13 100644
--- a/include/clang/AST/Expr.h
+++ b/include/clang/AST/Expr.h
@@ -1645,7 +1645,7 @@ public:
 /// initializations into the subobject they initialize. Additionally,
 /// any "holes" in the initialization, where no initializer has been
 /// specified for a particular subobject, will be replaced with
-/// implicitly-generated CXXZeroInitValueExpr expressions that
+/// implicitly-generated ImplicitValueInitExpr expressions that
 /// value-initialize the subobjects. Note, however, that the
 /// initializer lists may still have fewer initializers than there are
 /// elements to initialize within the object.
@@ -1987,6 +1987,31 @@ public:
   virtual child_iterator child_end(); 
 };
 
+/// \brief Represents an implicitly-generated value initialization of
+/// an object of a given type.
+///
+/// Implicit value initializations occur within semantic initialize
+/// list expressions (\see InitListExpr) as placeholders for subobject
+/// initializations not explicitly specified by the user.
+class ImplicitValueInitExpr : public Expr { 
+public:
+  explicit ImplicitValueInitExpr(QualType ty) 
+    : Expr(ImplicitValueInitExprClass, ty) { }
+
+  static bool classof(const Stmt *T) { 
+    return T->getStmtClass() == ImplicitValueInitExprClass;
+  }
+  static bool classof(const ImplicitValueInitExpr *) { return true; }
+
+  virtual SourceRange getSourceRange() const {
+    return SourceRange();
+  }
+
+  // Iterators
+  virtual child_iterator child_begin();
+  virtual child_iterator child_end(); 
+};
+
 //===----------------------------------------------------------------------===//
 // Clang Extensions
 //===----------------------------------------------------------------------===//
diff --git a/include/clang/AST/StmtNodes.def b/include/clang/AST/StmtNodes.def
index e8d4a56c50..18b8dbebfe 100644
--- a/include/clang/AST/StmtNodes.def
+++ b/include/clang/AST/StmtNodes.def
@@ -86,6 +86,7 @@ STMT(CompoundLiteralExpr   , Expr)
 STMT(ExtVectorElementExpr  , Expr)
 STMT(InitListExpr          , Expr)
 STMT(DesignatedInitExpr    , Expr)
+STMT(ImplicitValueInitExpr , Expr)
 STMT(VAArgExpr             , Expr)
 
 // GNU Extensions.
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index c1c8084cd5..8a04198293 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -735,6 +735,8 @@ bool Expr::isConstantInitializer(ASTContext &Ctx) const {
     }
     return true;
   }
+  case ImplicitValueInitExprClass:
+    return true;
   case ParenExprClass: {
     return cast<ParenExpr>(this)->getSubExpr()->isConstantInitializer(Ctx);
   }
@@ -1672,7 +1674,7 @@ Stmt::child_iterator InitListExpr::child_end() {
   return InitExprs.size() ? &InitExprs[0] + InitExprs.size() : 0;
 }
 
-/// DesignatedInitExpr
+// DesignatedInitExpr
 Stmt::child_iterator DesignatedInitExpr::child_begin() {
   char* Ptr = static_cast<char*>(static_cast<void *>(this));
   Ptr += sizeof(DesignatedInitExpr);
@@ -1683,6 +1685,15 @@ Stmt::child_iterator DesignatedInitExpr::child_end() {
   return child_iterator(&*child_begin() + NumSubExprs);
 }
 
+// ImplicitValueInitExpr
+Stmt::child_iterator ImplicitValueInitExpr::child_begin() { 
+  return child_iterator(); 
+}
+
+Stmt::child_iterator ImplicitValueInitExpr::child_end() { 
+  return child_iterator(); 
+}
+
 // ObjCStringLiteral
 Stmt::child_iterator ObjCStringLiteral::child_begin() { 
   return child_iterator();
diff --git a/lib/AST/StmtPrinter.cpp b/lib/AST/StmtPrinter.cpp
index 7a558ab8dd..27bab206a4 100644
--- a/lib/AST/StmtPrinter.cpp
+++ b/lib/AST/StmtPrinter.cpp
@@ -906,6 +906,10 @@ void StmtPrinter::VisitDesignatedInitExpr(DesignatedInitExpr *Node) {
   PrintExpr(Node->getInit());
 }
 
+void StmtPrinter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *Node) {
+  OS << "/*implicit*/" << Node->getType().getAsString() << "()";
+}
+
 void StmtPrinter::VisitVAArgExpr(VAArgExpr *Node) {
   OS << "va_arg(";
   PrintExpr(Node->getSubExpr());
diff --git a/lib/CodeGen/CGExprAgg.cpp b/lib/CodeGen/CGExprAgg.cpp
index b487bacc71..f985763b5c 100644
--- a/lib/CodeGen/CGExprAgg.cpp
+++ b/lib/CodeGen/CGExprAgg.cpp
@@ -339,10 +339,10 @@ void AggExprEmitter::EmitNonConstInit(InitListExpr *E) {
 
 void AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
   // FIXME: Are initializers affected by volatile?
-  if (E->getType()->isComplexType()) {
-    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
-  } else if (isa<CXXZeroInitValueExpr>(E)) {
+  if (isa<ImplicitValueInitExpr>(E)) {
     EmitNullInitializationToLValue(LV, E->getType());
+  } else if (E->getType()->isComplexType()) {
+    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
   } else if (CGF.hasAggregateLLVMType(E->getType())) {
     CGF.EmitAnyExpr(E, LV.getAddress(), false);
   } else {
diff --git a/lib/CodeGen/CGExprComplex.cpp b/lib/CodeGen/CGExprComplex.cpp
index 73fceedee5..387635cb06 100644
--- a/lib/CodeGen/CGExprComplex.cpp
+++ b/lib/CodeGen/CGExprComplex.cpp
@@ -130,6 +130,12 @@ public:
     llvm::Constant *Null = llvm::Constant::getNullValue(CGF.ConvertType(Elem));
     return ComplexPairTy(Null, Null);
   }
+  ComplexPairTy VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
+    assert(E->getType()->isAnyComplexType() && "Expected complex type!");
+    QualType Elem = E->getType()->getAsComplexType()->getElementType();
+    llvm::Constant *Null = llvm::Constant::getNullValue(CGF.ConvertType(Elem));
+    return ComplexPairTy(Null, Null);
+  }
   
   struct BinOpInfo {
     ComplexPairTy LHS;
diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index e523ab3acf..3aedf9bc7f 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -248,11 +248,6 @@ public:
 
     FieldDecl* curField = ILE->getInitializedFieldInUnion();
     if (!curField) {
-#ifndef NDEBUG
-#endif
-    }
-
-    if (!curField) {
       // There's no field to initialize, so value-initialize the union.
 #ifndef NDEBUG
       // Make sure that it's really an empty and not a failure of
diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index dd8b30041e..f855e23ba0 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -200,6 +200,9 @@ public:
     return V;
   }
   
+  Value *VisitImplicitValueInitExpr(const ImplicitValueInitExpr *E) {
+    return llvm::Constant::getNullValue(ConvertType(E->getType()));
+  }
   Value *VisitImplicitCastExpr(const ImplicitCastExpr *E);
   Value *VisitCastExpr(const CastExpr *E) { 
     return EmitCastExpr(E->getSubExpr(), E->getType());
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 7572560be1..1559213fcb 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -2220,17 +2220,17 @@ bool Sema::CheckForConstantInitializer(Expr *Init, QualType DclT) {
   if (CompoundLiteralExpr *e = dyn_cast<CompoundLiteralExpr>(Init))
     return CheckForConstantInitializer(e->getInitializer(), DclT);
 
+  if (isa<ImplicitValueInitExpr>(Init)) {
+    // FIXME: In C++, check for non-POD types.
+    return false;
+  }
+
   if (InitListExpr *Exp = dyn_cast<InitListExpr>(Init)) {
     unsigned numInits = Exp->getNumInits();
     for (unsigned i = 0; i < numInits; i++) {
       // FIXME: Need to get the type of the declaration for C++,
       // because it could be a reference?
 
-      // Implicitly-generated value initializations are okay.
-      if (isa<CXXZeroInitValueExpr>(Exp->getInit(i)) &&
-          cast<CXXZeroInitValueExpr>(Exp->getInit(i))->isImplicit()) 
-        continue;
-
       if (CheckForConstantInitializer(Exp->getInit(i),
                                       Exp->getInit(i)->getType()))
         return true;
diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp
index 527f965dc3..5d7f705edb 100644
--- a/lib/Sema/SemaInit.cpp
+++ b/lib/Sema/SemaInit.cpp
@@ -17,7 +17,6 @@
 #include "clang/Parse/Designator.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Expr.h"
-#include "clang/AST/ExprCXX.h"
 #include <map>
 using namespace clang;
 
@@ -137,10 +136,9 @@ static void fillInValueInitializations(ASTContext &Context, InitListExpr *ILE) {
       // FIXME: Check for fields with reference type in C++?
       if (!ILE->getInit(Init))
         ILE->setInit(Init, 
-                     new (Context) CXXZeroInitValueExpr(Field->getType(), 
-                                                        SourceLocation(),
-                                                        SourceLocation()));
-      else if (InitListExpr *InnerILE = dyn_cast<InitListExpr>(ILE->getInit(Init)))
+                     new (Context) ImplicitValueInitExpr(Field->getType()));
+      else if (InitListExpr *InnerILE 
+                 = dyn_cast<InitListExpr>(ILE->getInit(Init)))
         fillInValueInitializations(Context, InnerILE);
       ++Init;
     }
@@ -160,9 +158,7 @@ static void fillInValueInitializations(ASTContext &Context, InitListExpr *ILE) {
   for (unsigned Init = 0, NumInits = ILE->getNumInits(); Init != NumInits; 
        ++Init) {
     if (!ILE->getInit(Init))
-      ILE->setInit(Init, new (Context) CXXZeroInitValueExpr(ElementType, 
-                                                            SourceLocation(),
-                                                            SourceLocation()));
+      ILE->setInit(Init, new (Context) ImplicitValueInitExpr(ElementType));
     else if (InitListExpr *InnerILE =dyn_cast<InitListExpr>(ILE->getInit(Init)))
       fillInValueInitializations(Context, InnerILE);
   }
@@ -550,6 +546,22 @@ void InitListChecker::CheckStructUnionTypes(InitListExpr *IList,
     hadError = true;
     return;
   }    
+
+  if (DeclType->isUnionType() && IList->getNumInits() == 0) {
+    // Value-initialize the first named member of the union.
+    RecordDecl *RD = DeclType->getAsRecordType()->getDecl();
+    for (RecordDecl::field_iterator FieldEnd = RD->field_end();
+         Field != FieldEnd; ++Field) {
+      if (Field->getDeclName()) {
+        StructuredList->setInitializedFieldInUnion(*Field);
+        break;
+      }
+    }
+    return;
+  }
+
+
+
   // If structDecl is a forward declaration, this loop won't do
   // anything except look at designated initializers; That's okay,
   // because an error should get printed out elsewhere. It might be
diff --git a/test/CodeGen/designated-initializers.c b/test/CodeGen/designated-initializers.c
new file mode 100644
index 0000000000..0605b24b1c
--- /dev/null
+++ b/test/CodeGen/designated-initializers.c
@@ -0,0 +1,17 @@
+// RUN: clang %s -emit-llvm -o -
+// XFAIL
+struct foo {
+    void *a;
+    int b;
+};
+
+union { int i; float f; } u = { };
+
+int main(int argc, char **argv)
+{
+  union { int i; float f; } u2 = { };
+    static struct foo foo = {
+        .b = 1024,
+    };
+}
+