diff --git a/lib/Serialization/ASTReaderDecl.cpp b/lib/Serialization/ASTReaderDecl.cpp
index bdedf8a..f7f93af 100644
--- a/lib/Serialization/ASTReaderDecl.cpp
+++ b/lib/Serialization/ASTReaderDecl.cpp
@@ -556,43 +556,80 @@
 void ASTDeclReader::VisitObjCInterfaceDecl(ObjCInterfaceDecl *ID) {
   VisitObjCContainerDecl(ID);
   ID->setTypeForDecl(Reader.readType(F, Record, Idx).getTypePtrOrNull());
-  ID->setSuperClass(ReadDeclAs<ObjCInterfaceDecl>(Record, Idx));
   
-  // Read the directly referenced protocols and their SourceLocations.
-  unsigned NumProtocols = Record[Idx++];
-  SmallVector<ObjCProtocolDecl *, 16> Protocols;
-  Protocols.reserve(NumProtocols);
-  for (unsigned I = 0; I != NumProtocols; ++I)
-    Protocols.push_back(ReadDeclAs<ObjCProtocolDecl>(Record, Idx));
-  SmallVector<SourceLocation, 16> ProtoLocs;
-  ProtoLocs.reserve(NumProtocols);
-  for (unsigned I = 0; I != NumProtocols; ++I)
-    ProtoLocs.push_back(ReadSourceLocation(Record, Idx));
-  ID->setProtocolList(Protocols.data(), NumProtocols, ProtoLocs.data(),
-                      Reader.getContext());
+  ObjCInterfaceDecl *Def = ReadDeclAs<ObjCInterfaceDecl>(Record, Idx);
+  if (ID == Def) {
+    // Read the definition.
+    ID->allocateDefinitionData();
+    
+    ObjCInterfaceDecl::DefinitionData &Data = ID->data();
+    
+    // Read the superclass.
+    Data.SuperClass = ReadDeclAs<ObjCInterfaceDecl>(Record, Idx);
+    Data.SuperClassLoc = ReadSourceLocation(Record, Idx);
+
+    // Read the directly referenced protocols and their SourceLocations.
+    unsigned NumProtocols = Record[Idx++];
+    SmallVector<ObjCProtocolDecl *, 16> Protocols;
+    Protocols.reserve(NumProtocols);
+    for (unsigned I = 0; I != NumProtocols; ++I)
+      Protocols.push_back(ReadDeclAs<ObjCProtocolDecl>(Record, Idx));
+    SmallVector<SourceLocation, 16> ProtoLocs;
+    ProtoLocs.reserve(NumProtocols);
+    for (unsigned I = 0; I != NumProtocols; ++I)
+      ProtoLocs.push_back(ReadSourceLocation(Record, Idx));
+    ID->setProtocolList(Protocols.data(), NumProtocols, ProtoLocs.data(),
+                        Reader.getContext());
   
-  // Read the transitive closure of protocols referenced by this class.
-  NumProtocols = Record[Idx++];
-  Protocols.clear();
-  Protocols.reserve(NumProtocols);
-  for (unsigned I = 0; I != NumProtocols; ++I)
-    Protocols.push_back(ReadDeclAs<ObjCProtocolDecl>(Record, Idx));
-  ID->AllReferencedProtocols.set(Protocols.data(), NumProtocols,
-                                 Reader.getContext());
+    // Read the transitive closure of protocols referenced by this class.
+    NumProtocols = Record[Idx++];
+    Protocols.clear();
+    Protocols.reserve(NumProtocols);
+    for (unsigned I = 0; I != NumProtocols; ++I)
+      Protocols.push_back(ReadDeclAs<ObjCProtocolDecl>(Record, Idx));
+    ID->data().AllReferencedProtocols.set(Protocols.data(), NumProtocols,
+                                          Reader.getContext());
   
-  // Read the ivars.
-  unsigned NumIvars = Record[Idx++];
-  SmallVector<ObjCIvarDecl *, 16> IVars;
-  IVars.reserve(NumIvars);
-  for (unsigned I = 0; I != NumIvars; ++I)
-    IVars.push_back(ReadDeclAs<ObjCIvarDecl>(Record, Idx));
-  ID->setCategoryList(ReadDeclAs<ObjCCategoryDecl>(Record, Idx));
+    // Read the ivars.
+    unsigned NumIvars = Record[Idx++];
+    SmallVector<ObjCIvarDecl *, 16> IVars;
+    IVars.reserve(NumIvars);
+    for (unsigned I = 0; I != NumIvars; ++I)
+      IVars.push_back(ReadDeclAs<ObjCIvarDecl>(Record, Idx));
+    
+    // Read the categories.
+    ID->setCategoryList(ReadDeclAs<ObjCCategoryDecl>(Record, Idx));
   
-  // We will rebuild this list lazily.
-  ID->setIvarList(0);
+    // We will rebuild this list lazily.
+    ID->setIvarList(0);
+    
+    // If there are any pending forward references, make their definition data
+    // pointers point at the newly-allocated data.
+    ASTReader::PendingForwardRefsMap::iterator
+    FindI = Reader.PendingForwardRefs.find(ID);
+    if (FindI != Reader.PendingForwardRefs.end()) {
+      ASTReader::ForwardRefs &Refs = FindI->second;
+      for (ASTReader::ForwardRefs::iterator I = Refs.begin(), 
+                                            E = Refs.end(); 
+           I != E; ++I)
+        cast<ObjCInterfaceDecl>(*I)->Definition = ID->Definition;
+#ifndef NDEBUG
+      // We later check whether PendingForwardRefs is empty to make sure all
+      // pending references were linked.
+      Reader.PendingForwardRefs.erase(ID);
+#endif
+    
+    } else if (Def) {
+      if (Def->Definition) {
+        ID->Definition = Def->Definition;
+      } else {
+        // The definition is still initializing.
+        Reader.PendingForwardRefs[Def].push_back(ID);
+      }
+    }
+  }
+  
   ID->InitiallyForwardDecl = Record[Idx++];
-  ID->ForwardDecl = Record[Idx++];
-  ID->setSuperClassLoc(ReadSourceLocation(Record, Idx));
   ID->setLocEnd(ReadSourceLocation(Record, Idx));
 }
 
@@ -972,7 +1009,7 @@
       ASTReader::ForwardRefs &Refs = FindI->second;
       for (ASTReader::ForwardRefs::iterator
              I = Refs.begin(), E = Refs.end(); I != E; ++I)
-        (*I)->DefinitionData = D->DefinitionData;
+        cast<CXXRecordDecl>(*I)->DefinitionData = D->DefinitionData;
 #ifndef NDEBUG
       // We later check whether PendingForwardRefs is empty to make sure all
       // pending references were linked.
diff --git a/lib/Serialization/ASTWriterDecl.cpp b/lib/Serialization/ASTWriterDecl.cpp
index 1448e59..9396958 100644
--- a/lib/Serialization/ASTWriterDecl.cpp
+++ b/lib/Serialization/ASTWriterDecl.cpp
@@ -449,36 +449,46 @@
 void ASTDeclWriter::VisitObjCInterfaceDecl(ObjCInterfaceDecl *D) {
   VisitObjCContainerDecl(D);
   Writer.AddTypeRef(QualType(D->getTypeForDecl(), 0), Record);
-  Writer.AddDeclRef(D->getSuperClass(), Record);
 
-  // Write out the protocols that are directly referenced by the @interface.
-  Record.push_back(D->ReferencedProtocols.size());
-  for (ObjCInterfaceDecl::protocol_iterator P = D->protocol_begin(),
-         PEnd = D->protocol_end();
-       P != PEnd; ++P)
-    Writer.AddDeclRef(*P, Record);
-  for (ObjCInterfaceDecl::protocol_loc_iterator PL = D->protocol_loc_begin(),
-         PLEnd = D->protocol_loc_end();
-       PL != PLEnd; ++PL)
-    Writer.AddSourceLocation(*PL, Record);
-
-  // Write out the protocols that are transitively referenced.
-  Record.push_back(D->AllReferencedProtocols.size());
-  for (ObjCList<ObjCProtocolDecl>::iterator
-        P = D->AllReferencedProtocols.begin(),
-        PEnd = D->AllReferencedProtocols.end();
-       P != PEnd; ++P)
-    Writer.AddDeclRef(*P, Record);
+  ObjCInterfaceDecl *Def = D->getDefinition();
+  Writer.AddDeclRef(Def, Record);
   
-  // Write out the ivars.
-  Record.push_back(D->ivar_size());
-  for (ObjCInterfaceDecl::ivar_iterator I = D->ivar_begin(),
-                                     IEnd = D->ivar_end(); I != IEnd; ++I)
-    Writer.AddDeclRef(*I, Record);
-  Writer.AddDeclRef(D->getCategoryList(), Record);
+  if (D == Def) {
+    // Write the DefinitionData
+    ObjCInterfaceDecl::DefinitionData &Data = D->data();
+    
+    Writer.AddDeclRef(D->getSuperClass(), Record);
+    Writer.AddSourceLocation(D->getSuperClassLoc(), Record);
+    
+    // Write out the protocols that are directly referenced by the @interface.
+    Record.push_back(Data.ReferencedProtocols.size());
+    for (ObjCInterfaceDecl::protocol_iterator P = D->protocol_begin(),
+                                           PEnd = D->protocol_end();
+         P != PEnd; ++P)
+      Writer.AddDeclRef(*P, Record);
+    for (ObjCInterfaceDecl::protocol_loc_iterator PL = D->protocol_loc_begin(),
+         PLEnd = D->protocol_loc_end();
+         PL != PLEnd; ++PL)
+      Writer.AddSourceLocation(*PL, Record);
+    
+    // Write out the protocols that are transitively referenced.
+    Record.push_back(Data.AllReferencedProtocols.size());
+    for (ObjCList<ObjCProtocolDecl>::iterator
+              P = Data.AllReferencedProtocols.begin(),
+           PEnd = Data.AllReferencedProtocols.end();
+         P != PEnd; ++P)
+      Writer.AddDeclRef(*P, Record);
+    
+    // Write out the ivars.
+    Record.push_back(D->ivar_size());
+    for (ObjCInterfaceDecl::ivar_iterator I = D->ivar_begin(),
+                                       IEnd = D->ivar_end(); I != IEnd; ++I)
+      Writer.AddDeclRef(*I, Record);
+    
+    Writer.AddDeclRef(D->getCategoryList(), Record);
+  }  
+  
   Record.push_back(D->isInitiallyForwardDecl());
-  Record.push_back(D->isForwardDecl());
-  Writer.AddSourceLocation(D->getSuperClassLoc(), Record);
   Writer.AddSourceLocation(D->getLocEnd(), Record);
   Code = serialization::DECL_OBJC_INTERFACE;
 }