Vendor import of clang trunk r154661:

http://llvm.org/svn/llvm-project/cfe/trunk@r154661

1 files changed, 1023 insertions, 506 deletions

diff --git a/lib/Serialization/ASTReaderDecl.cpp b/lib/Serialization/ASTReaderDecl.cpp
index 6cc3f0a..5db5f92 100644
--- a/lib/Serialization/ASTReaderDecl.cpp
+++ b/lib/Serialization/ASTReaderDecl.cpp
@@ -14,6 +14,8 @@
 
 #include "ASTCommon.h"
 #include "clang/Serialization/ASTReader.h"
+#include "clang/Sema/IdentifierResolver.h"
+#include "clang/Sema/Sema.h"
 #include "clang/Sema/SemaDiagnostic.h"
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
@@ -32,9 +34,10 @@ using namespace clang::serialization;
 namespace clang {
   class ASTDeclReader : public DeclVisitor<ASTDeclReader, void> {
     ASTReader &Reader;
-    Module &F;
+    ModuleFile &F;
     llvm::BitstreamCursor &Cursor;
     const DeclID ThisDeclID;
+    const unsigned RawLocation;
     typedef ASTReader::RecordData RecordData;
     const RecordData &Record;
     unsigned &Idx;
@@ -85,24 +88,123 @@ namespace clang {
       Reader.ReadDeclarationNameInfo(F, NameInfo, R, I);
     }
 
+    serialization::SubmoduleID readSubmoduleID(const RecordData &R, 
+                                               unsigned &I) {
+      if (I >= R.size())
+        return 0;
+      
+      return Reader.getGlobalSubmoduleID(F, R[I++]);
+    }
+    
+    Module *readModule(const RecordData &R, unsigned &I) {
+      return Reader.getSubmodule(readSubmoduleID(R, I));
+    }
+    
     void ReadCXXDefinitionData(struct CXXRecordDecl::DefinitionData &Data,
                                const RecordData &R, unsigned &I);
 
-    void InitializeCXXDefinitionData(CXXRecordDecl *D,
-                                     CXXRecordDecl *DefinitionDecl,
-                                     const RecordData &Record, unsigned &Idx);
+    /// \brief RAII class used to capture the first ID within a redeclaration
+    /// chain and to introduce it into the list of pending redeclaration chains
+    /// on destruction.
+    ///
+    /// The caller can choose not to introduce this ID into the redeclaration
+    /// chain by calling \c suppress().
+    class RedeclarableResult {
+      ASTReader &Reader;
+      GlobalDeclID FirstID;
+      mutable bool Owning;
+      
+      RedeclarableResult &operator=(RedeclarableResult&); // DO NOT IMPLEMENT
+      
+    public:
+      RedeclarableResult(ASTReader &Reader, GlobalDeclID FirstID)
+        : Reader(Reader), FirstID(FirstID), Owning(true) { }
+
+      RedeclarableResult(const RedeclarableResult &Other)
+        : Reader(Other.Reader), FirstID(Other.FirstID), Owning(Other.Owning) 
+      { 
+        Other.Owning = false;
+      }
+
+      ~RedeclarableResult() {
+        // FIXME: We want to suppress this when the declaration is local to
+        // a function, since there's no reason to search other AST files
+        // for redeclarations (they can't exist). However, this is hard to 
+        // do locally because the declaration hasn't necessarily loaded its
+        // declaration context yet. Also, local externs still have the function
+        // as their (semantic) declaration context, which is wrong and would
+        // break this optimize.
+        
+        if (FirstID && Owning && Reader.PendingDeclChainsKnown.insert(FirstID))
+          Reader.PendingDeclChains.push_back(FirstID);
+      }
+      
+      /// \brief Retrieve the first ID.
+      GlobalDeclID getFirstID() const { return FirstID; }
+      
+      /// \brief Do not introduce this declaration ID into the set of pending
+      /// declaration chains.
+      void suppress() {
+        Owning = false;
+      }
+    };
+    
+    /// \brief Class used to capture the result of searching for an existing
+    /// declaration of a specific kind and name, along with the ability
+    /// to update the place where this result was found (the declaration
+    /// chain hanging off an identifier or the DeclContext we searched in)
+    /// if requested.
+    class FindExistingResult {
+      ASTReader &Reader;
+      NamedDecl *New;
+      NamedDecl *Existing;
+      mutable bool AddResult;
+      
+      FindExistingResult &operator=(FindExistingResult&); // DO NOT IMPLEMENT
+      
+    public:
+      FindExistingResult(ASTReader &Reader)
+        : Reader(Reader), New(0), Existing(0), AddResult(false) { }
+      
+      FindExistingResult(ASTReader &Reader, NamedDecl *New, NamedDecl *Existing)
+        : Reader(Reader), New(New), Existing(Existing), AddResult(true) { }
+      
+      FindExistingResult(const FindExistingResult &Other)
+        : Reader(Other.Reader), New(Other.New), Existing(Other.Existing), 
+          AddResult(Other.AddResult)
+      {
+        Other.AddResult = false;
+      }
+      
+      ~FindExistingResult();
+      
+      /// \brief Suppress the addition of this result into the known set of
+      /// names.
+      void suppress() { AddResult = false; }
+      
+      operator NamedDecl*() const { return Existing; }
+      
+      template<typename T>
+      operator T*() const { return dyn_cast_or_null<T>(Existing); }
+    };
+    
+    FindExistingResult findExisting(NamedDecl *D);
+    
   public:
-    ASTDeclReader(ASTReader &Reader, Module &F,
+    ASTDeclReader(ASTReader &Reader, ModuleFile &F,
                   llvm::BitstreamCursor &Cursor, DeclID thisDeclID,
+                  unsigned RawLocation,
                   const RecordData &Record, unsigned &Idx)
       : Reader(Reader), F(F), Cursor(Cursor), ThisDeclID(thisDeclID),
-        Record(Record), Idx(Idx), TypeIDForTypeDecl(0) { }
+        RawLocation(RawLocation), Record(Record), Idx(Idx),
+        TypeIDForTypeDecl(0) { }
 
     static void attachPreviousDecl(Decl *D, Decl *previous);
+    static void attachLatestDecl(Decl *D, Decl *latest);
 
     void Visit(Decl *D);
 
-    void UpdateDecl(Decl *D, Module &Module,
+    void UpdateDecl(Decl *D, ModuleFile &ModuleFile,
                     const RecordData &Record);
 
     static void setNextObjCCategory(ObjCCategoryDecl *Cat,
@@ -118,6 +220,7 @@ namespace clang {
     void VisitUsingDirectiveDecl(UsingDirectiveDecl *D);
     void VisitNamespaceAliasDecl(NamespaceAliasDecl *D);
     void VisitTypeDecl(TypeDecl *TD);
+    void VisitTypedefNameDecl(TypedefNameDecl *TD);
     void VisitTypedefDecl(TypedefDecl *TD);
     void VisitTypeAliasDecl(TypeAliasDecl *TD);
     void VisitUnresolvedUsingTypenameDecl(UnresolvedUsingTypenameDecl *D);
@@ -148,7 +251,7 @@ namespace clang {
     void VisitParmVarDecl(ParmVarDecl *PD);
     void VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D);
     void VisitTemplateDecl(TemplateDecl *D);
-    void VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D);
+    RedeclarableResult VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D);
     void VisitClassTemplateDecl(ClassTemplateDecl *D);
     void VisitFunctionTemplateDecl(FunctionTemplateDecl *D);
     void VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D);
@@ -157,6 +260,7 @@ namespace clang {
     void VisitUsingShadowDecl(UsingShadowDecl *D);
     void VisitLinkageSpecDecl(LinkageSpecDecl *D);
     void VisitFileScopeAsmDecl(FileScopeAsmDecl *AD);
+    void VisitImportDecl(ImportDecl *D);
     void VisitAccessSpecDecl(AccessSpecDecl *D);
     void VisitFriendDecl(FriendDecl *D);
     void VisitFriendTemplateDecl(FriendTemplateDecl *D);
@@ -164,8 +268,13 @@ namespace clang {
     void VisitBlockDecl(BlockDecl *BD);
 
     std::pair<uint64_t, uint64_t> VisitDeclContext(DeclContext *DC);
-    template <typename T> void VisitRedeclarable(Redeclarable<T> *D);
+    
+    template<typename T> 
+    RedeclarableResult VisitRedeclarable(Redeclarable<T> *D);
 
+    template<typename T>
+    void mergeRedeclarable(Redeclarable<T> *D, RedeclarableResult &Redecl);
+    
     // FIXME: Reorder according to DeclNodes.td?
     void VisitObjCMethodDecl(ObjCMethodDecl *D);
     void VisitObjCContainerDecl(ObjCContainerDecl *D);
@@ -173,8 +282,6 @@ namespace clang {
     void VisitObjCIvarDecl(ObjCIvarDecl *D);
     void VisitObjCProtocolDecl(ObjCProtocolDecl *D);
     void VisitObjCAtDefsFieldDecl(ObjCAtDefsFieldDecl *D);
-    void VisitObjCClassDecl(ObjCClassDecl *D);
-    void VisitObjCForwardProtocolDecl(ObjCForwardProtocolDecl *D);
     void VisitObjCCategoryDecl(ObjCCategoryDecl *D);
     void VisitObjCImplDecl(ObjCImplDecl *D);
     void VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *D);
@@ -207,6 +314,9 @@ void ASTDeclReader::Visit(Decl *D) {
   if (TypeDecl *TD = dyn_cast<TypeDecl>(D)) {
     // if we have a fully initialized TypeDecl, we can safely read its type now.
     TD->setTypeForDecl(Reader.GetType(TypeIDForTypeDecl).getTypePtrOrNull());
+  } else if (ObjCInterfaceDecl *ID = dyn_cast<ObjCInterfaceDecl>(D)) {
+    // if we have a fully initialized TypeDecl, we can safely read its type now.
+    ID->TypeForDecl = Reader.GetType(TypeIDForTypeDecl).getTypePtrOrNull();
   } else if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
     // FunctionDecl's body was written last after all other Stmts/Exprs.
     if (Record[Idx++])
@@ -214,12 +324,11 @@ void ASTDeclReader::Visit(Decl *D) {
   } else if (D->isTemplateParameter()) {
     // If we have a fully initialized template parameter, we can now
     // set its DeclContext.
-    D->setDeclContext(
-          cast_or_null<DeclContext>(
-                            Reader.GetDecl(DeclContextIDForTemplateParmDecl)));
-    D->setLexicalDeclContext(
-          cast_or_null<DeclContext>(
-                      Reader.GetDecl(LexicalDeclContextIDForTemplateParmDecl)));
+    DeclContext *SemaDC = cast<DeclContext>(
+                              Reader.GetDecl(DeclContextIDForTemplateParmDecl));
+    DeclContext *LexicalDC = cast<DeclContext>(
+                       Reader.GetDecl(LexicalDeclContextIDForTemplateParmDecl));
+    D->setDeclContextsImpl(SemaDC, LexicalDC, Reader.getContext());
   }
 }
 
@@ -233,22 +342,50 @@ void ASTDeclReader::VisitDecl(Decl *D) {
     LexicalDeclContextIDForTemplateParmDecl = ReadDeclID(Record, Idx);
     D->setDeclContext(Reader.getContext().getTranslationUnitDecl()); 
   } else {
-    D->setDeclContext(ReadDeclAs<DeclContext>(Record, Idx));
-    D->setLexicalDeclContext(ReadDeclAs<DeclContext>(Record, Idx));
+    DeclContext *SemaDC = ReadDeclAs<DeclContext>(Record, Idx);
+    DeclContext *LexicalDC = ReadDeclAs<DeclContext>(Record, Idx);
+    // Avoid calling setLexicalDeclContext() directly because it uses
+    // Decl::getASTContext() internally which is unsafe during derialization.
+    D->setDeclContextsImpl(SemaDC, LexicalDC, Reader.getContext());
   }
-  D->setLocation(ReadSourceLocation(Record, Idx));
+  D->setLocation(Reader.ReadSourceLocation(F, RawLocation));
   D->setInvalidDecl(Record[Idx++]);
   if (Record[Idx++]) { // hasAttrs
     AttrVec Attrs;
     Reader.ReadAttributes(F, Attrs, Record, Idx);
-    D->setAttrs(Attrs);
+    // Avoid calling setAttrs() directly because it uses Decl::getASTContext()
+    // internally which is unsafe during derialization.
+    D->setAttrsImpl(Attrs, Reader.getContext());
   }
   D->setImplicit(Record[Idx++]);
   D->setUsed(Record[Idx++]);
   D->setReferenced(Record[Idx++]);
+  D->setTopLevelDeclInObjCContainer(Record[Idx++]);
   D->setAccess((AccessSpecifier)Record[Idx++]);
   D->FromASTFile = true;
-  D->ModulePrivate = Record[Idx++];
+  D->setModulePrivate(Record[Idx++]);
+  D->Hidden = D->isModulePrivate();
+  
+  // Determine whether this declaration is part of a (sub)module. If so, it
+  // may not yet be visible.
+  if (unsigned SubmoduleID = readSubmoduleID(Record, Idx)) {
+    // Store the owning submodule ID in the declaration.
+    D->setOwningModuleID(SubmoduleID);
+    
+    // Module-private declarations are never visible, so there is no work to do.
+    if (!D->isModulePrivate()) {
+      if (Module *Owner = Reader.getSubmodule(SubmoduleID)) {
+        if (Owner->NameVisibility != Module::AllVisible) {
+          // The owning module is not visible. Mark this declaration as hidden.
+          D->Hidden = true;
+          
+          // Note that this declaration was hidden because its owning module is 
+          // not yet visible.
+          Reader.HiddenNamesMap[Owner].push_back(D);
+        }
+      }
+    }
+  }
 }
 
 void ASTDeclReader::VisitTranslationUnitDecl(TranslationUnitDecl *TU) {
@@ -267,31 +404,41 @@ void ASTDeclReader::VisitTypeDecl(TypeDecl *TD) {
   TypeIDForTypeDecl = Reader.getGlobalTypeID(F, Record[Idx++]);
 }
 
-void ASTDeclReader::VisitTypedefDecl(TypedefDecl *TD) {
+void ASTDeclReader::VisitTypedefNameDecl(TypedefNameDecl *TD) {
+  RedeclarableResult Redecl = VisitRedeclarable(TD);
   VisitTypeDecl(TD);
+  
   TD->setTypeSourceInfo(GetTypeSourceInfo(Record, Idx));
+  mergeRedeclarable(TD, Redecl);
+}
+
+void ASTDeclReader::VisitTypedefDecl(TypedefDecl *TD) {
+  VisitTypedefNameDecl(TD);
 }
 
 void ASTDeclReader::VisitTypeAliasDecl(TypeAliasDecl *TD) {
-  VisitTypeDecl(TD);
-  TD->setTypeSourceInfo(GetTypeSourceInfo(Record, Idx));
+  VisitTypedefNameDecl(TD);
 }
 
 void ASTDeclReader::VisitTagDecl(TagDecl *TD) {
+  RedeclarableResult Redecl = VisitRedeclarable(TD);
   VisitTypeDecl(TD);
-  VisitRedeclarable(TD);
+  
   TD->IdentifierNamespace = Record[Idx++];
   TD->setTagKind((TagDecl::TagKind)Record[Idx++]);
   TD->setCompleteDefinition(Record[Idx++]);
   TD->setEmbeddedInDeclarator(Record[Idx++]);
   TD->setFreeStanding(Record[Idx++]);
   TD->setRBraceLoc(ReadSourceLocation(Record, Idx));
+  
   if (Record[Idx++]) { // hasExtInfo
     TagDecl::ExtInfo *Info = new (Reader.getContext()) TagDecl::ExtInfo();
     ReadQualifierInfo(*Info, Record, Idx);
     TD->TypedefNameDeclOrQualifier = Info;
   } else
     TD->setTypedefNameForAnonDecl(ReadDeclAs<TypedefNameDecl>(Record, Idx));
+
+  mergeRedeclarable(TD, Redecl);  
 }
 
 void ASTDeclReader::VisitEnumDecl(EnumDecl *ED) {
@@ -306,7 +453,13 @@ void ASTDeclReader::VisitEnumDecl(EnumDecl *ED) {
   ED->IsScoped = Record[Idx++];
   ED->IsScopedUsingClassTag = Record[Idx++];
   ED->IsFixed = Record[Idx++];
-  ED->setInstantiationOfMemberEnum(ReadDeclAs<EnumDecl>(Record, Idx));
+
+  if (EnumDecl *InstED = ReadDeclAs<EnumDecl>(Record, Idx)) {
+    TemplateSpecializationKind TSK = (TemplateSpecializationKind)Record[Idx++];
+    SourceLocation POI = ReadSourceLocation(Record, Idx);
+    ED->setInstantiationOfMemberEnum(Reader.getContext(), InstED, TSK);
+    ED->getMemberSpecializationInfo()->setPointOfInstantiation(POI);
+  }
 }
 
 void ASTDeclReader::VisitRecordDecl(RecordDecl *RD) {
@@ -340,14 +493,34 @@ void ASTDeclReader::VisitDeclaratorDecl(DeclaratorDecl *DD) {
 }
 
 void ASTDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
+  RedeclarableResult Redecl = VisitRedeclarable(FD);
   VisitDeclaratorDecl(FD);
-  VisitRedeclarable(FD);
 
   ReadDeclarationNameLoc(FD->DNLoc, FD->getDeclName(), Record, Idx);
   FD->IdentifierNamespace = Record[Idx++];
+  
+  // FunctionDecl's body is handled last at ASTDeclReader::Visit,
+  // after everything else is read.
+  
+  FD->SClass = (StorageClass)Record[Idx++];
+  FD->SClassAsWritten = (StorageClass)Record[Idx++];
+  FD->IsInline = Record[Idx++];
+  FD->IsInlineSpecified = Record[Idx++];
+  FD->IsVirtualAsWritten = Record[Idx++];
+  FD->IsPure = Record[Idx++];
+  FD->HasInheritedPrototype = Record[Idx++];
+  FD->HasWrittenPrototype = Record[Idx++];
+  FD->IsDeleted = Record[Idx++];
+  FD->IsTrivial = Record[Idx++];
+  FD->IsDefaulted = Record[Idx++];
+  FD->IsExplicitlyDefaulted = Record[Idx++];
+  FD->HasImplicitReturnZero = Record[Idx++];
+  FD->IsConstexpr = Record[Idx++];
+  FD->EndRangeLoc = ReadSourceLocation(Record, Idx);
+
   switch ((FunctionDecl::TemplatedKind)Record[Idx++]) {
-  default: llvm_unreachable("Unhandled TemplatedKind!");
   case FunctionDecl::TK_NonTemplate:
+    mergeRedeclarable(FD, Redecl);      
     break;
   case FunctionDecl::TK_FunctionTemplate:
     FD->setDescribedFunctionTemplate(ReadDeclAs<FunctionTemplateDecl>(Record, 
@@ -441,25 +614,6 @@ void ASTDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
   }
   }
 
-  // FunctionDecl's body is handled last at ASTDeclReader::Visit,
-  // after everything else is read.
-
-  FD->SClass = (StorageClass)Record[Idx++];
-  FD->SClassAsWritten = (StorageClass)Record[Idx++];
-  FD->IsInline = Record[Idx++];
-  FD->IsInlineSpecified = Record[Idx++];
-  FD->IsVirtualAsWritten = Record[Idx++];
-  FD->IsPure = Record[Idx++];
-  FD->HasInheritedPrototype = Record[Idx++];
-  FD->HasWrittenPrototype = Record[Idx++];
-  FD->IsDeleted = Record[Idx++];
-  FD->IsTrivial = Record[Idx++];
-  FD->IsDefaulted = Record[Idx++];
-  FD->IsExplicitlyDefaulted = Record[Idx++];
-  FD->HasImplicitReturnZero = Record[Idx++];
-  FD->IsConstexpr = Record[Idx++];
-  FD->EndRangeLoc = ReadSourceLocation(Record, Idx);
-
   // Read in the parameters.
   unsigned NumParams = Record[Idx++];
   SmallVector<ParmVarDecl *, 16> Params;
@@ -518,46 +672,60 @@ void ASTDeclReader::VisitObjCContainerDecl(ObjCContainerDecl *CD) {
 }
 
 void ASTDeclReader::VisitObjCInterfaceDecl(ObjCInterfaceDecl *ID) {
+  RedeclarableResult Redecl = VisitRedeclarable(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());
+  TypeIDForTypeDecl = Reader.getGlobalTypeID(F, Record[Idx++]);
+  mergeRedeclarable(ID, Redecl);
   
-  // 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());
+  if (Record[Idx++]) {
+    // Read the definition.
+    ID->allocateDefinitionData();
+    
+    // Set the definition data of the canonical declaration, so other
+    // redeclarations will see it.
+    ID->getCanonicalDecl()->Data = ID->Data;
+    
+    ObjCInterfaceDecl::DefinitionData &Data = ID->data();
+    
+    // Read the superclass.
+    Data.SuperClass = ReadDeclAs<ObjCInterfaceDecl>(Record, Idx);
+    Data.SuperClassLoc = ReadSourceLocation(Record, Idx);
+
+    Data.EndLoc = 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 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 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());
   
-  // We will rebuild this list lazily.
-  ID->setIvarList(0);
-  ID->setForwardDecl(Record[Idx++]);
-  ID->setImplicitInterfaceDecl(Record[Idx++]);
-  ID->setSuperClassLoc(ReadSourceLocation(Record, Idx));
-  ID->setLocEnd(ReadSourceLocation(Record, Idx));
+    // We will rebuild this list lazily.
+    ID->setIvarList(0);
+    
+    // Note that we have deserialized a definition.
+    Reader.PendingDefinitions.insert(ID);
+    
+    // Note that we've loaded this Objective-C class.
+    Reader.ObjCClassesLoaded.push_back(ID);
+  } else {
+    ID->Data = ID->getCanonicalDecl()->Data;
+  }
 }
 
 void ASTDeclReader::VisitObjCIvarDecl(ObjCIvarDecl *IVD) {
@@ -570,50 +738,52 @@ void ASTDeclReader::VisitObjCIvarDecl(ObjCIvarDecl *IVD) {
 }
 
 void ASTDeclReader::VisitObjCProtocolDecl(ObjCProtocolDecl *PD) {
+  RedeclarableResult Redecl = VisitRedeclarable(PD);
   VisitObjCContainerDecl(PD);
-  PD->setForwardDecl(Record[Idx++]);
-  PD->setLocEnd(ReadSourceLocation(Record, Idx));
-  unsigned NumProtoRefs = Record[Idx++];
-  SmallVector<ObjCProtocolDecl *, 16> ProtoRefs;
-  ProtoRefs.reserve(NumProtoRefs);
-  for (unsigned I = 0; I != NumProtoRefs; ++I)
-    ProtoRefs.push_back(ReadDeclAs<ObjCProtocolDecl>(Record, Idx));
-  SmallVector<SourceLocation, 16> ProtoLocs;
-  ProtoLocs.reserve(NumProtoRefs);
-  for (unsigned I = 0; I != NumProtoRefs; ++I)
-    ProtoLocs.push_back(ReadSourceLocation(Record, Idx));
-  PD->setProtocolList(ProtoRefs.data(), NumProtoRefs, ProtoLocs.data(),
-                      Reader.getContext());
+  mergeRedeclarable(PD, Redecl);
+  
+  if (Record[Idx++]) {
+    // Read the definition.
+    PD->allocateDefinitionData();
+    
+    // Set the definition data of the canonical declaration, so other
+    // redeclarations will see it.
+    PD->getCanonicalDecl()->Data = PD->Data;
+
+    unsigned NumProtoRefs = Record[Idx++];
+    SmallVector<ObjCProtocolDecl *, 16> ProtoRefs;
+    ProtoRefs.reserve(NumProtoRefs);
+    for (unsigned I = 0; I != NumProtoRefs; ++I)
+      ProtoRefs.push_back(ReadDeclAs<ObjCProtocolDecl>(Record, Idx));
+    SmallVector<SourceLocation, 16> ProtoLocs;
+    ProtoLocs.reserve(NumProtoRefs);
+    for (unsigned I = 0; I != NumProtoRefs; ++I)
+      ProtoLocs.push_back(ReadSourceLocation(Record, Idx));
+    PD->setProtocolList(ProtoRefs.data(), NumProtoRefs, ProtoLocs.data(),
+                        Reader.getContext());
+    
+    // Note that we have deserialized a definition.
+    Reader.PendingDefinitions.insert(PD);
+  } else {
+    PD->Data = PD->getCanonicalDecl()->Data;
+  }
 }
 
 void ASTDeclReader::VisitObjCAtDefsFieldDecl(ObjCAtDefsFieldDecl *FD) {
   VisitFieldDecl(FD);
 }
 
-void ASTDeclReader::VisitObjCClassDecl(ObjCClassDecl *CD) {
-  VisitDecl(CD);
-  ObjCInterfaceDecl *ClassRef = ReadDeclAs<ObjCInterfaceDecl>(Record, Idx);
-  SourceLocation SLoc = ReadSourceLocation(Record, Idx);
-  CD->setClass(Reader.getContext(), ClassRef, SLoc);
-}
-
-void ASTDeclReader::VisitObjCForwardProtocolDecl(ObjCForwardProtocolDecl *FPD) {
-  VisitDecl(FPD);
-  unsigned NumProtoRefs = Record[Idx++];
-  SmallVector<ObjCProtocolDecl *, 16> ProtoRefs;
-  ProtoRefs.reserve(NumProtoRefs);
-  for (unsigned I = 0; I != NumProtoRefs; ++I)
-    ProtoRefs.push_back(ReadDeclAs<ObjCProtocolDecl>(Record, Idx));
-  SmallVector<SourceLocation, 16> ProtoLocs;
-  ProtoLocs.reserve(NumProtoRefs);
-  for (unsigned I = 0; I != NumProtoRefs; ++I)
-    ProtoLocs.push_back(ReadSourceLocation(Record, Idx));
-  FPD->setProtocolList(ProtoRefs.data(), NumProtoRefs, ProtoLocs.data(),
-                       Reader.getContext());
-}
-
 void ASTDeclReader::VisitObjCCategoryDecl(ObjCCategoryDecl *CD) {
   VisitObjCContainerDecl(CD);
+  CD->setCategoryNameLoc(ReadSourceLocation(Record, Idx));
+  CD->setIvarLBraceLoc(ReadSourceLocation(Record, Idx));
+  CD->setIvarRBraceLoc(ReadSourceLocation(Record, Idx));
+  
+  // Note that this category has been deserialized. We do this before
+  // deserializing the interface declaration, so that it will consider this
+  /// category.
+  Reader.CategoriesDeserialized.insert(CD);
+
   CD->ClassInterface = ReadDeclAs<ObjCInterfaceDecl>(Record, Idx);
   unsigned NumProtoRefs = Record[Idx++];
   SmallVector<ObjCProtocolDecl *, 16> ProtoRefs;
@@ -626,9 +796,7 @@ void ASTDeclReader::VisitObjCCategoryDecl(ObjCCategoryDecl *CD) {
     ProtoLocs.push_back(ReadSourceLocation(Record, Idx));
   CD->setProtocolList(ProtoRefs.data(), NumProtoRefs, ProtoLocs.data(),
                       Reader.getContext());
-  CD->NextClassCategory = ReadDeclAs<ObjCCategoryDecl>(Record, Idx);
   CD->setHasSynthBitfield(Record[Idx++]);
-  CD->setCategoryNameLoc(ReadSourceLocation(Record, Idx));
 }
 
 void ASTDeclReader::VisitObjCCompatibleAliasDecl(ObjCCompatibleAliasDecl *CAD) {
@@ -639,6 +807,7 @@ void ASTDeclReader::VisitObjCCompatibleAliasDecl(ObjCCompatibleAliasDecl *CAD) {
 void ASTDeclReader::VisitObjCPropertyDecl(ObjCPropertyDecl *D) {
   VisitNamedDecl(D);
   D->setAtLoc(ReadSourceLocation(Record, Idx));
+  D->setLParenLoc(ReadSourceLocation(Record, Idx));
   D->setType(GetTypeSourceInfo(Record, Idx));
   // FIXME: stable encoding
   D->setPropertyAttributes(
@@ -663,11 +832,14 @@ void ASTDeclReader::VisitObjCImplDecl(ObjCImplDecl *D) {
 void ASTDeclReader::VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *D) {
   VisitObjCImplDecl(D);
   D->setIdentifier(Reader.GetIdentifierInfo(F, Record, Idx));
+  D->CategoryNameLoc = ReadSourceLocation(Record, Idx);
 }
 
 void ASTDeclReader::VisitObjCImplementationDecl(ObjCImplementationDecl *D) {
   VisitObjCImplDecl(D);
   D->setSuperClass(ReadDeclAs<ObjCInterfaceDecl>(Record, Idx));
+  D->setIvarLBraceLoc(ReadSourceLocation(Record, Idx));
+  D->setIvarRBraceLoc(ReadSourceLocation(Record, Idx));
   llvm::tie(D->IvarInitializers, D->NumIvarInitializers)
       = Reader.ReadCXXCtorInitializers(F, Record, Idx);
   D->setHasSynthBitfield(Record[Idx++]);
@@ -710,18 +882,30 @@ void ASTDeclReader::VisitIndirectFieldDecl(IndirectFieldDecl *FD) {
 }
 
 void ASTDeclReader::VisitVarDecl(VarDecl *VD) {
+  RedeclarableResult Redecl = VisitRedeclarable(VD);
   VisitDeclaratorDecl(VD);
-  VisitRedeclarable(VD);
+  
   VD->VarDeclBits.SClass = (StorageClass)Record[Idx++];
   VD->VarDeclBits.SClassAsWritten = (StorageClass)Record[Idx++];
   VD->VarDeclBits.ThreadSpecified = Record[Idx++];
-  VD->VarDeclBits.HasCXXDirectInit = Record[Idx++];
+  VD->VarDeclBits.InitStyle = Record[Idx++];
   VD->VarDeclBits.ExceptionVar = Record[Idx++];
   VD->VarDeclBits.NRVOVariable = Record[Idx++];
   VD->VarDeclBits.CXXForRangeDecl = Record[Idx++];
   VD->VarDeclBits.ARCPseudoStrong = Record[Idx++];
-  if (Record[Idx++])
+
+  // Only true variables (not parameters or implicit parameters) can be merged.
+  if (VD->getKind() == Decl::Var)
+    mergeRedeclarable(VD, Redecl);
+  
+  if (uint64_t Val = Record[Idx++]) {
     VD->setInit(Reader.ReadExpr(F));
+    if (Val > 1) {
+      EvaluatedStmt *Eval = VD->ensureEvaluatedStmt();
+      Eval->CheckedICE = true;
+      Eval->IsICE = Val == 3;
+    }
+  }
 
   if (Record[Idx++]) { // HasMemberSpecializationInfo.
     VarDecl *Tmpl = ReadDeclAs<VarDecl>(Record, Idx);
@@ -802,17 +986,25 @@ void ASTDeclReader::VisitLabelDecl(LabelDecl *D) {
 
 
 void ASTDeclReader::VisitNamespaceDecl(NamespaceDecl *D) {
+  RedeclarableResult Redecl = VisitRedeclarable(D);
   VisitNamedDecl(D);
-  D->IsInline = Record[Idx++];
+  D->setInline(Record[Idx++]);
   D->LocStart = ReadSourceLocation(Record, Idx);
   D->RBraceLoc = ReadSourceLocation(Record, Idx);
-  D->NextNamespace = Record[Idx++];
-
-  bool IsOriginal = Record[Idx++];
-  // FIXME: Modules will likely have trouble with pointing directly at
-  // the original namespace.
-  D->OrigOrAnonNamespace.setInt(IsOriginal);
-  D->OrigOrAnonNamespace.setPointer(ReadDeclAs<NamespaceDecl>(Record, Idx));
+  mergeRedeclarable(D, Redecl);
+
+  if (Redecl.getFirstID() == ThisDeclID) {
+    // Each module has its own anonymous namespace, which is disjoint from
+    // any other module's anonymous namespaces, so don't attach the anonymous
+    // namespace at all.
+    NamespaceDecl *Anon = ReadDeclAs<NamespaceDecl>(Record, Idx);
+    if (F.Kind != MK_Module)
+      D->setAnonymousNamespace(Anon);
+  } else {
+    // Link this namespace back to the first declaration, which has already
+    // been deserialized.
+    D->AnonOrFirstNamespaceAndInline.setPointer(D->getFirstDeclaration());
+  }
 }
 
 void ASTDeclReader::VisitNamespaceAliasDecl(NamespaceAliasDecl *D) {
@@ -828,7 +1020,7 @@ void ASTDeclReader::VisitUsingDecl(UsingDecl *D) {
   D->setUsingLocation(ReadSourceLocation(Record, Idx));
   D->QualifierLoc = Reader.ReadNestedNameSpecifierLoc(F, Record, Idx);
   ReadDeclarationNameLoc(D->DNLoc, D->getDeclName(), Record, Idx);
-  D->FirstUsingShadow = ReadDeclAs<UsingShadowDecl>(Record, Idx);
+  D->FirstUsingShadow.setPointer(ReadDeclAs<UsingShadowDecl>(Record, Idx));
   D->setTypeName(Record[Idx++]);
   if (NamedDecl *Pattern = ReadDeclAs<NamedDecl>(Record, Idx))
     Reader.getContext().setInstantiatedFromUsingDecl(D, Pattern);
@@ -869,6 +1061,7 @@ void ASTDeclReader::VisitUnresolvedUsingTypenameDecl(
 void ASTDeclReader::ReadCXXDefinitionData(
                                    struct CXXRecordDecl::DefinitionData &Data,
                                    const RecordData &Record, unsigned &Idx) {
+  // Note: the caller has deserialized the IsLambda bit already.
   Data.UserDeclaredConstructor = Record[Idx++];
   Data.UserDeclaredCopyConstructor = Record[Idx++];
   Data.UserDeclaredMoveConstructor = Record[Idx++];
@@ -886,13 +1079,21 @@ void ASTDeclReader::ReadCXXDefinitionData(
   Data.HasProtectedFields = Record[Idx++];
   Data.HasPublicFields = Record[Idx++];
   Data.HasMutableFields = Record[Idx++];
+  Data.HasOnlyCMembers = Record[Idx++];
   Data.HasTrivialDefaultConstructor = Record[Idx++];
   Data.HasConstexprNonCopyMoveConstructor = Record[Idx++];
+  Data.DefaultedDefaultConstructorIsConstexpr = Record[Idx++];
+  Data.DefaultedCopyConstructorIsConstexpr = Record[Idx++];
+  Data.DefaultedMoveConstructorIsConstexpr = Record[Idx++];
+  Data.HasConstexprDefaultConstructor = Record[Idx++];
+  Data.HasConstexprCopyConstructor = Record[Idx++];
+  Data.HasConstexprMoveConstructor = Record[Idx++];
   Data.HasTrivialCopyConstructor = Record[Idx++];
   Data.HasTrivialMoveConstructor = Record[Idx++];
   Data.HasTrivialCopyAssignment = Record[Idx++];
   Data.HasTrivialMoveAssignment = Record[Idx++];
   Data.HasTrivialDestructor = Record[Idx++];
+  Data.HasIrrelevantDestructor = Record[Idx++];
   Data.HasNonLiteralTypeFieldsOrBases = Record[Idx++];
   Data.ComputedVisibleConversions = Record[Idx++];
   Data.UserProvidedDefaultConstructor = Record[Idx++];
@@ -916,38 +1117,26 @@ void ASTDeclReader::ReadCXXDefinitionData(
   Reader.ReadUnresolvedSet(F, Data.VisibleConversions, Record, Idx);
   assert(Data.Definition && "Data.Definition should be already set!");
   Data.FirstFriend = ReadDeclAs<FriendDecl>(Record, Idx);
-}
-
-void ASTDeclReader::InitializeCXXDefinitionData(CXXRecordDecl *D,
-                                                CXXRecordDecl *DefinitionDecl,
-                                                const RecordData &Record,
-                                                unsigned &Idx) {
-  ASTContext &C = Reader.getContext();
-
-  if (D == DefinitionDecl) {
-    D->DefinitionData = new (C) struct CXXRecordDecl::DefinitionData(D);
-    ReadCXXDefinitionData(*D->DefinitionData, Record, Idx);
-    // We read the definition info. Check if there are pending forward
-    // references that need to point to this DefinitionData pointer.
-    ASTReader::PendingForwardRefsMap::iterator
-        FindI = Reader.PendingForwardRefs.find(D);
-    if (FindI != Reader.PendingForwardRefs.end()) {
-      ASTReader::ForwardRefs &Refs = FindI->second;
-      for (ASTReader::ForwardRefs::iterator
-             I = Refs.begin(), E = Refs.end(); I != E; ++I)
-        (*I)->DefinitionData = D->DefinitionData;
-#ifndef NDEBUG
-      // We later check whether PendingForwardRefs is empty to make sure all
-      // pending references were linked.
-      Reader.PendingForwardRefs.erase(D);
-#endif
-    }
-  } else if (DefinitionDecl) {
-    if (DefinitionDecl->DefinitionData) {
-      D->DefinitionData = DefinitionDecl->DefinitionData;
-    } else {
-      // The definition is still initializing.
-      Reader.PendingForwardRefs[DefinitionDecl].push_back(D);
+  
+  if (Data.IsLambda) {
+    typedef LambdaExpr::Capture Capture;
+    CXXRecordDecl::LambdaDefinitionData &Lambda
+      = static_cast<CXXRecordDecl::LambdaDefinitionData &>(Data);
+    Lambda.Dependent = Record[Idx++];
+    Lambda.NumCaptures = Record[Idx++];
+    Lambda.NumExplicitCaptures = Record[Idx++];
+    Lambda.ManglingNumber = Record[Idx++];
+    Lambda.ContextDecl = ReadDecl(Record, Idx);
+    Lambda.Captures 
+      = (Capture*)Reader.Context.Allocate(sizeof(Capture)*Lambda.NumCaptures);
+    Capture *ToCapture = Lambda.Captures;
+    for (unsigned I = 0, N = Lambda.NumCaptures; I != N; ++I) {
+      SourceLocation Loc = ReadSourceLocation(Record, Idx);
+      bool IsImplicit = Record[Idx++];
+      LambdaCaptureKind Kind = static_cast<LambdaCaptureKind>(Record[Idx++]);
+      VarDecl *Var = ReadDeclAs<VarDecl>(Record, Idx);
+      SourceLocation EllipsisLoc = ReadSourceLocation(Record, Idx);
+      *ToCapture++ = Capture(Loc, IsImplicit, Kind, Var, EllipsisLoc);
     }
   }
 }
@@ -955,17 +1144,36 @@ void ASTDeclReader::InitializeCXXDefinitionData(CXXRecordDecl *D,
 void ASTDeclReader::VisitCXXRecordDecl(CXXRecordDecl *D) {
   VisitRecordDecl(D);
 
-  CXXRecordDecl *DefinitionDecl = ReadDeclAs<CXXRecordDecl>(Record, Idx);
-  InitializeCXXDefinitionData(D, DefinitionDecl, Record, Idx);
-
   ASTContext &C = Reader.getContext();
+  if (Record[Idx++]) {
+    // Determine whether this is a lambda closure type, so that we can
+    // allocate the appropriate DefinitionData structure.
+    bool IsLambda = Record[Idx++];
+    if (IsLambda)
+      D->DefinitionData = new (C) CXXRecordDecl::LambdaDefinitionData(D, false);
+    else
+      D->DefinitionData = new (C) struct CXXRecordDecl::DefinitionData(D);
+    
+    // Propagate the DefinitionData pointer to the canonical declaration, so
+    // that all other deserialized declarations will see it.
+    // FIXME: Complain if there already is a DefinitionData!
+    D->getCanonicalDecl()->DefinitionData = D->DefinitionData;
+    
+    ReadCXXDefinitionData(*D->DefinitionData, Record, Idx);
+    
+    // Note that we have deserialized a definition. Any declarations 
+    // deserialized before this one will be be given the DefinitionData pointer
+    // at the end.
+    Reader.PendingDefinitions.insert(D);
+  } else {
+    // Propagate DefinitionData pointer from the canonical declaration.
+    D->DefinitionData = D->getCanonicalDecl()->DefinitionData;    
+  }
 
   enum CXXRecKind {
     CXXRecNotTemplate = 0, CXXRecTemplate, CXXRecMemberSpecialization
   };
   switch ((CXXRecKind)Record[Idx++]) {
-  default:
-    llvm_unreachable("Out of sync with ASTDeclWriter::VisitCXXRecordDecl?");
   case CXXRecNotTemplate:
     break;
   case CXXRecTemplate:
@@ -1022,6 +1230,16 @@ void ASTDeclReader::VisitCXXConversionDecl(CXXConversionDecl *D) {
   D->IsExplicitSpecified = Record[Idx++];
 }
 
+void ASTDeclReader::VisitImportDecl(ImportDecl *D) {
+  VisitDecl(D);
+  D->ImportedAndComplete.setPointer(readModule(Record, Idx));
+  D->ImportedAndComplete.setInt(Record[Idx++]);
+  SourceLocation *StoredLocs = reinterpret_cast<SourceLocation *>(D + 1);
+  for (unsigned I = 0, N = Record.back(); I != N; ++I)
+    StoredLocs[I] = ReadSourceLocation(Record, Idx);
+  ++Idx;
+}
+
 void ASTDeclReader::VisitAccessSpecDecl(AccessSpecDecl *D) {
   VisitDecl(D);
   D->setColonLoc(ReadSourceLocation(Record, Idx));
@@ -1061,64 +1279,42 @@ void ASTDeclReader::VisitTemplateDecl(TemplateDecl *D) {
   D->init(TemplatedDecl, TemplateParams);
 }
 
-void ASTDeclReader::VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D) {
-  // Initialize CommonOrPrev before VisitTemplateDecl so that getCommonPtr()
-  // can be used while this is still initializing.
-
-  assert(D->CommonOrPrev.isNull() && "getCommonPtr was called earlier on this");
-  DeclID PreviousDeclID = ReadDeclID(Record, Idx);
-  DeclID FirstDeclID =  PreviousDeclID ? ReadDeclID(Record, Idx) : 0;
-  // We delay loading of the redeclaration chain to avoid deeply nested calls.
-  // We temporarily set the first (canonical) declaration as the previous one
-  // which is the one that matters and mark the real previous DeclID to be
-  // loaded & attached later on.
-  RedeclarableTemplateDecl *FirstDecl =
-      cast_or_null<RedeclarableTemplateDecl>(Reader.GetDecl(FirstDeclID));
-  assert((FirstDecl == 0 || FirstDecl->getKind() == D->getKind()) &&
-         "FirstDecl kind mismatch");
-  if (FirstDecl) {
-    D->CommonOrPrev = FirstDecl;
-    // Mark the real previous DeclID to be loaded & attached later on.
-    if (PreviousDeclID != FirstDeclID)
-      Reader.PendingPreviousDecls.push_back(std::make_pair(D, PreviousDeclID));
-  } else {
-    D->CommonOrPrev = D->newCommon(Reader.getContext());
+ASTDeclReader::RedeclarableResult 
+ASTDeclReader::VisitRedeclarableTemplateDecl(RedeclarableTemplateDecl *D) {
+  RedeclarableResult Redecl = VisitRedeclarable(D);
+
+  // Make sure we've allocated the Common pointer first. We do this before
+  // VisitTemplateDecl so that getCommonPtr() can be used during initialization.
+  RedeclarableTemplateDecl *CanonD = D->getCanonicalDecl();
+  if (!CanonD->Common) {
+    CanonD->Common = CanonD->newCommon(Reader.getContext());
+    Reader.PendingDefinitions.insert(CanonD);
+  }
+  D->Common = CanonD->Common;
+
+  // If this is the first declaration of the template, fill in the information
+  // for the 'common' pointer.
+  if (ThisDeclID == Redecl.getFirstID()) {
     if (RedeclarableTemplateDecl *RTD
           = ReadDeclAs<RedeclarableTemplateDecl>(Record, Idx)) {
       assert(RTD->getKind() == D->getKind() &&
              "InstantiatedFromMemberTemplate kind mismatch");
-      D->setInstantiatedFromMemberTemplateImpl(RTD);
+      D->setInstantiatedFromMemberTemplate(RTD);
       if (Record[Idx++])
         D->setMemberSpecialization();
     }
-
-    RedeclarableTemplateDecl *LatestDecl
-      = ReadDeclAs<RedeclarableTemplateDecl>(Record, Idx);
-  
-    // This decl is a first one and the latest declaration that it points to is
-    // in the same AST file. However, if this actually needs to point to a
-    // redeclaration in another AST file, we need to update it by checking
-    // the FirstLatestDeclIDs map which tracks this kind of decls.
-    assert(Reader.GetDecl(ThisDeclID) == D && "Invalid ThisDeclID ?");
-    ASTReader::FirstLatestDeclIDMap::iterator I
-        = Reader.FirstLatestDeclIDs.find(ThisDeclID);
-    if (I != Reader.FirstLatestDeclIDs.end()) {
-      if (Decl *NewLatest = Reader.GetDecl(I->second))
-        LatestDecl = cast<RedeclarableTemplateDecl>(NewLatest);
-    }
-
-    assert(LatestDecl->getKind() == D->getKind() && "Latest kind mismatch");
-    D->getCommonPtr()->Latest = LatestDecl;
   }
-
+     
   VisitTemplateDecl(D);
   D->IdentifierNamespace = Record[Idx++];
+  
+  return Redecl;
 }
 
 void ASTDeclReader::VisitClassTemplateDecl(ClassTemplateDecl *D) {
-  VisitRedeclarableTemplateDecl(D);
+  RedeclarableResult Redecl = VisitRedeclarableTemplateDecl(D);
 
-  if (D->getPreviousDeclaration() == 0) {
+  if (ThisDeclID == Redecl.getFirstID()) {
     // This ClassTemplateDecl owns a CommonPtr; read it to keep track of all of
     // the specializations.
     SmallVector<serialization::DeclID, 2> SpecIDs;
@@ -1140,6 +1336,7 @@ void ASTDeclReader::VisitClassTemplateDecl(ClassTemplateDecl *D) {
       typedef serialization::DeclID DeclID;
       
       ClassTemplateDecl::Common *CommonPtr = D->getCommonPtr();
+      // FIXME: Append specializations!
       CommonPtr->LazySpecializations
         = new (Reader.getContext()) DeclID [SpecIDs.size()];
       memcpy(CommonPtr->LazySpecializations, SpecIDs.data(), 
@@ -1220,7 +1417,7 @@ void ASTDeclReader::VisitClassTemplatePartialSpecializationDecl(
   D->SequenceNumber = Record[Idx++];
 
   // These are read/set from/to the first declaration.
-  if (D->getPreviousDeclaration() == 0) {
+  if (D->getPreviousDecl() == 0) {
     D->InstantiatedFromMember.setPointer(
       ReadDeclAs<ClassTemplatePartialSpecializationDecl>(Record, Idx));
     D->InstantiatedFromMember.setInt(Record[Idx++]);
@@ -1234,9 +1431,9 @@ void ASTDeclReader::VisitClassScopeFunctionSpecializationDecl(
 }
 
 void ASTDeclReader::VisitFunctionTemplateDecl(FunctionTemplateDecl *D) {
-  VisitRedeclarableTemplateDecl(D);
+  RedeclarableResult Redecl = VisitRedeclarableTemplateDecl(D);
 
-  if (D->getPreviousDeclaration() == 0) {
+  if (ThisDeclID == Redecl.getFirstID()) {
     // This FunctionTemplateDecl owns a CommonPtr; read it.
 
     // Read the function specialization declarations.
@@ -1311,54 +1508,90 @@ ASTDeclReader::VisitDeclContext(DeclContext *DC) {
 }
 
 template <typename T>
-void ASTDeclReader::VisitRedeclarable(Redeclarable<T> *D) {
-  enum RedeclKind { NoRedeclaration = 0, PointsToPrevious, PointsToLatest };
-  RedeclKind Kind = (RedeclKind)Record[Idx++];
-  switch (Kind) {
-  default:
-    llvm_unreachable("Out of sync with ASTDeclWriter::VisitRedeclarable or"
-                     " messed up reading");
-  case NoRedeclaration:
-    break;
-  case PointsToPrevious: {
-    DeclID PreviousDeclID = ReadDeclID(Record, Idx);
-    DeclID FirstDeclID = ReadDeclID(Record, Idx);
+ASTDeclReader::RedeclarableResult 
+ASTDeclReader::VisitRedeclarable(Redeclarable<T> *D) {
+  DeclID FirstDeclID = ReadDeclID(Record, Idx);
+  
+  // 0 indicates that this declaration was the only declaration of its entity,
+  // and is used for space optimization.
+  if (FirstDeclID == 0)
+    FirstDeclID = ThisDeclID;
+  
+  T *FirstDecl = cast_or_null<T>(Reader.GetDecl(FirstDeclID));
+  if (FirstDecl != D) {
     // We delay loading of the redeclaration chain to avoid deeply nested calls.
     // We temporarily set the first (canonical) declaration as the previous one
     // which is the one that matters and mark the real previous DeclID to be
     // loaded & attached later on.
-    D->RedeclLink = typename Redeclarable<T>::PreviousDeclLink(
-                                cast_or_null<T>(Reader.GetDecl(FirstDeclID)));
-    if (PreviousDeclID != FirstDeclID)
-      Reader.PendingPreviousDecls.push_back(std::make_pair(static_cast<T*>(D),
-                                                           PreviousDeclID));
-    break;
-  }
-  case PointsToLatest:
-    D->RedeclLink = typename Redeclarable<T>::LatestDeclLink(
-                                                   ReadDeclAs<T>(Record, Idx));
-    break;
-  }
-
-  assert(!(Kind == PointsToPrevious &&
-           Reader.FirstLatestDeclIDs.find(ThisDeclID) !=
-               Reader.FirstLatestDeclIDs.end()) &&
-         "This decl is not first, it should not be in the map");
-  if (Kind == PointsToPrevious)
+    D->RedeclLink = typename Redeclarable<T>::PreviousDeclLink(FirstDecl);
+  }    
+  
+  // Note that this declaration has been deserialized.
+  Reader.RedeclsDeserialized.insert(static_cast<T *>(D));
+                             
+  // The result structure takes care to note that we need to load the 
+  // other declaration chains for this ID.
+  return RedeclarableResult(Reader, FirstDeclID);
+}
+
+/// \brief Attempts to merge the given declaration (D) with another declaration
+/// of the same entity.
+template<typename T>
+void ASTDeclReader::mergeRedeclarable(Redeclarable<T> *D, 
+                                      RedeclarableResult &Redecl) {
+  // If modules are not available, there is no reason to perform this merge.
+  if (!Reader.getContext().getLangOpts().Modules)
     return;
-
-  // This decl is a first one and the latest declaration that it points to is in
-  // the same AST file. However, if this actually needs to point to a
-  // redeclaration in another AST file, we need to update it by checking the
-  // FirstLatestDeclIDs map which tracks this kind of decls.
-  assert(Reader.GetDecl(ThisDeclID) == static_cast<T*>(D) &&
-         "Invalid ThisDeclID ?");
-  ASTReader::FirstLatestDeclIDMap::iterator I
-      = Reader.FirstLatestDeclIDs.find(ThisDeclID);
-  if (I != Reader.FirstLatestDeclIDs.end()) {
-    Decl *NewLatest = Reader.GetDecl(I->second);
-    D->RedeclLink
-        = typename Redeclarable<T>::LatestDeclLink(cast_or_null<T>(NewLatest));
+  
+  if (FindExistingResult ExistingRes = findExisting(static_cast<T*>(D))) {
+    if (T *Existing = ExistingRes) {
+      T *ExistingCanon = Existing->getCanonicalDecl();
+      T *DCanon = static_cast<T*>(D)->getCanonicalDecl();
+      if (ExistingCanon != DCanon) {
+        // Have our redeclaration link point back at the canonical declaration
+        // of the existing declaration, so that this declaration has the 
+        // appropriate canonical declaration.
+        D->RedeclLink 
+          = typename Redeclarable<T>::PreviousDeclLink(ExistingCanon);
+        
+        // When we merge a namespace, update its pointer to the first namespace.
+        if (NamespaceDecl *Namespace
+              = dyn_cast<NamespaceDecl>(static_cast<T*>(D))) {
+          Namespace->AnonOrFirstNamespaceAndInline.setPointer(
+            static_cast<NamespaceDecl *>(static_cast<void*>(ExistingCanon)));
+        }
+        
+        // Don't introduce DCanon into the set of pending declaration chains.
+        Redecl.suppress();
+        
+        // Introduce ExistingCanon into the set of pending declaration chains,
+        // if in fact it came from a module file.
+        if (ExistingCanon->isFromASTFile()) {
+          GlobalDeclID ExistingCanonID = ExistingCanon->getGlobalID();
+          assert(ExistingCanonID && "Unrecorded canonical declaration ID?");
+          if (Reader.PendingDeclChainsKnown.insert(ExistingCanonID))
+            Reader.PendingDeclChains.push_back(ExistingCanonID);
+        }
+        
+        // If this declaration was the canonical declaration, make a note of 
+        // that. We accept the linear algorithm here because the number of 
+        // unique canonical declarations of an entity should always be tiny.
+        if (DCanon == static_cast<T*>(D)) {
+          SmallVectorImpl<DeclID> &Merged = Reader.MergedDecls[ExistingCanon];
+          if (std::find(Merged.begin(), Merged.end(), Redecl.getFirstID())
+                == Merged.end())
+            Merged.push_back(Redecl.getFirstID());
+          
+          // If ExistingCanon did not come from a module file, introduce the
+          // first declaration that *does* come from a module file to the 
+          // set of pending declaration chains, so that we merge this 
+          // declaration.
+          if (!ExistingCanon->isFromASTFile() &&
+              Reader.PendingDeclChainsKnown.insert(Redecl.getFirstID()))
+            Reader.PendingDeclChains.push_back(Merged[0]);
+        }
+      }
+    }
   }
 }
 
@@ -1367,7 +1600,7 @@ void ASTDeclReader::VisitRedeclarable(Redeclarable<T> *D) {
 //===----------------------------------------------------------------------===//
 
 /// \brief Reads attributes from the current stream position.
-void ASTReader::ReadAttributes(Module &F, AttrVec &Attrs,
+void ASTReader::ReadAttributes(ModuleFile &F, AttrVec &Attrs,
                                const RecordData &Record, unsigned &Idx) {
   for (unsigned i = 0, e = Record[Idx++]; i != e; ++i) {
     Attr *New = 0;
@@ -1422,31 +1655,142 @@ static bool isConsumerInterestedIn(Decl *D) {
 
 /// \brief Get the correct cursor and offset for loading a declaration.
 ASTReader::RecordLocation
-ASTReader::DeclCursorForID(DeclID ID) {
+ASTReader::DeclCursorForID(DeclID ID, unsigned &RawLocation) {
   // See if there's an override.
   DeclReplacementMap::iterator It = ReplacedDecls.find(ID);
-  if (It != ReplacedDecls.end())
-    return RecordLocation(It->second.first, It->second.second);
+  if (It != ReplacedDecls.end()) {
+    RawLocation = It->second.RawLoc;
+    return RecordLocation(It->second.Mod, It->second.Offset);
+  }
 
   GlobalDeclMapType::iterator I = GlobalDeclMap.find(ID);
   assert(I != GlobalDeclMap.end() && "Corrupted global declaration map");
-  Module *M = I->second;
-  return RecordLocation(M, 
-           M->DeclOffsets[ID - M->BaseDeclID - NUM_PREDEF_DECL_IDS]);
+  ModuleFile *M = I->second;
+  const DeclOffset &
+    DOffs =  M->DeclOffsets[ID - M->BaseDeclID - NUM_PREDEF_DECL_IDS];
+  RawLocation = DOffs.Loc;
+  return RecordLocation(M, DOffs.BitOffset);
 }
 
 ASTReader::RecordLocation ASTReader::getLocalBitOffset(uint64_t GlobalOffset) {
-  ContinuousRangeMap<uint64_t, Module*, 4>::iterator I
+  ContinuousRangeMap<uint64_t, ModuleFile*, 4>::iterator I
     = GlobalBitOffsetsMap.find(GlobalOffset);
 
   assert(I != GlobalBitOffsetsMap.end() && "Corrupted global bit offsets map");
   return RecordLocation(I->second, GlobalOffset - I->second->GlobalBitOffset);
 }
 
-uint64_t ASTReader::getGlobalBitOffset(Module &M, uint32_t LocalOffset) {
+uint64_t ASTReader::getGlobalBitOffset(ModuleFile &M, uint32_t LocalOffset) {
   return LocalOffset + M.GlobalBitOffset;
 }
 
+/// \brief Determine whether the two declarations refer to the same entity.
+static bool isSameEntity(NamedDecl *X, NamedDecl *Y) {
+  assert(X->getDeclName() == Y->getDeclName() && "Declaration name mismatch!");
+  
+  if (X == Y)
+    return true;
+  
+  // Must be in the same context.
+  if (!X->getDeclContext()->getRedeclContext()->Equals(
+         Y->getDeclContext()->getRedeclContext()))
+    return false;
+
+  // Two typedefs refer to the same entity if they have the same underlying
+  // type.
+  if (TypedefNameDecl *TypedefX = dyn_cast<TypedefNameDecl>(X))
+    if (TypedefNameDecl *TypedefY = dyn_cast<TypedefNameDecl>(Y))
+      return X->getASTContext().hasSameType(TypedefX->getUnderlyingType(),
+                                            TypedefY->getUnderlyingType());
+  
+  // Must have the same kind.
+  if (X->getKind() != Y->getKind())
+    return false;
+    
+  // Objective-C classes and protocols with the same name always match.
+  if (isa<ObjCInterfaceDecl>(X) || isa<ObjCProtocolDecl>(X))
+    return true;
+  
+  // Compatible tags match.
+  if (TagDecl *TagX = dyn_cast<TagDecl>(X)) {
+    TagDecl *TagY = cast<TagDecl>(Y);
+    return (TagX->getTagKind() == TagY->getTagKind()) ||
+      ((TagX->getTagKind() == TTK_Struct || TagX->getTagKind() == TTK_Class) &&
+       (TagY->getTagKind() == TTK_Struct || TagY->getTagKind() == TTK_Class));
+  }
+  
+  // Functions with the same type and linkage match.
+  // FIXME: This needs to cope with function templates, merging of 
+  //prototyped/non-prototyped functions, etc.
+  if (FunctionDecl *FuncX = dyn_cast<FunctionDecl>(X)) {
+    FunctionDecl *FuncY = cast<FunctionDecl>(Y);
+    return (FuncX->getLinkage() == FuncY->getLinkage()) &&
+      FuncX->getASTContext().hasSameType(FuncX->getType(), FuncY->getType());
+  }
+  
+  // Variables with the same type and linkage match.
+  if (VarDecl *VarX = dyn_cast<VarDecl>(X)) {
+    VarDecl *VarY = cast<VarDecl>(Y);
+    return (VarX->getLinkage() == VarY->getLinkage()) &&
+      VarX->getASTContext().hasSameType(VarX->getType(), VarY->getType());
+  }
+  
+  // Namespaces with the same name and inlinedness match.
+  if (NamespaceDecl *NamespaceX = dyn_cast<NamespaceDecl>(X)) {
+    NamespaceDecl *NamespaceY = cast<NamespaceDecl>(Y);
+    return NamespaceX->isInline() == NamespaceY->isInline();
+  }
+      
+  // FIXME: Many other cases to implement.
+  return false;
+}
+
+ASTDeclReader::FindExistingResult::~FindExistingResult() {
+  if (!AddResult || Existing)
+    return;
+  
+  DeclContext *DC = New->getDeclContext()->getRedeclContext();
+  if (DC->isTranslationUnit() && Reader.SemaObj) {
+    Reader.SemaObj->IdResolver.tryAddTopLevelDecl(New, New->getDeclName());
+  } else if (DC->isNamespace()) {
+    DC->addDecl(New);
+  }
+}
+
+ASTDeclReader::FindExistingResult ASTDeclReader::findExisting(NamedDecl *D) {
+  DeclarationName Name = D->getDeclName();
+  if (!Name) {
+    // Don't bother trying to find unnamed declarations.
+    FindExistingResult Result(Reader, D, /*Existing=*/0);
+    Result.suppress();
+    return Result;
+  }
+  
+  DeclContext *DC = D->getDeclContext()->getRedeclContext();
+  if (!DC->isFileContext())
+    return FindExistingResult(Reader);
+  
+  if (DC->isTranslationUnit() && Reader.SemaObj) {
+    IdentifierResolver &IdResolver = Reader.SemaObj->IdResolver;
+    for (IdentifierResolver::iterator I = IdResolver.begin(Name), 
+                                   IEnd = IdResolver.end();
+         I != IEnd; ++I) {
+      if (isSameEntity(*I, D))
+        return FindExistingResult(Reader, D, *I);
+    }
+  }
+
+  if (DC->isNamespace()) {
+    for (DeclContext::lookup_result R = DC->lookup(Name);
+         R.first != R.second; ++R.first) {
+      if (isSameEntity(*R.first, D))
+        return FindExistingResult(Reader, D, *R.first);
+    }
+  }
+  
+  return FindExistingResult(Reader, D, /*Existing=*/0);
+}
+
 void ASTDeclReader::attachPreviousDecl(Decl *D, Decl *previous) {
   assert(D && previous);
   if (TagDecl *TD = dyn_cast<TagDecl>(D)) {
@@ -1455,12 +1799,78 @@ void ASTDeclReader::attachPreviousDecl(Decl *D, Decl *previous) {
     FD->RedeclLink.setPointer(cast<FunctionDecl>(previous));
   } else if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
     VD->RedeclLink.setPointer(cast<VarDecl>(previous));
+  } else if (TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(D)) {
+    TD->RedeclLink.setPointer(cast<TypedefNameDecl>(previous));
+  } else if (ObjCInterfaceDecl *ID = dyn_cast<ObjCInterfaceDecl>(D)) {
+    ID->RedeclLink.setPointer(cast<ObjCInterfaceDecl>(previous));
+  } else if (ObjCProtocolDecl *PD = dyn_cast<ObjCProtocolDecl>(D)) {
+    PD->RedeclLink.setPointer(cast<ObjCProtocolDecl>(previous));
+  } else if (NamespaceDecl *ND = dyn_cast<NamespaceDecl>(D)) {
+    ND->RedeclLink.setPointer(cast<NamespaceDecl>(previous));
   } else {
     RedeclarableTemplateDecl *TD = cast<RedeclarableTemplateDecl>(D);
-    TD->CommonOrPrev = cast<RedeclarableTemplateDecl>(previous);
+    TD->RedeclLink.setPointer(cast<RedeclarableTemplateDecl>(previous));
   }
 }
 
+void ASTDeclReader::attachLatestDecl(Decl *D, Decl *Latest) {
+  assert(D && Latest);
+  if (TagDecl *TD = dyn_cast<TagDecl>(D)) {
+    TD->RedeclLink
+      = Redeclarable<TagDecl>::LatestDeclLink(cast<TagDecl>(Latest));
+  } else if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
+    FD->RedeclLink 
+      = Redeclarable<FunctionDecl>::LatestDeclLink(cast<FunctionDecl>(Latest));
+  } else if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
+    VD->RedeclLink
+      = Redeclarable<VarDecl>::LatestDeclLink(cast<VarDecl>(Latest));
+  } else if (TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(D)) {
+    TD->RedeclLink
+      = Redeclarable<TypedefNameDecl>::LatestDeclLink(
+                                                cast<TypedefNameDecl>(Latest));
+  } else if (ObjCInterfaceDecl *ID = dyn_cast<ObjCInterfaceDecl>(D)) {
+    ID->RedeclLink
+      = Redeclarable<ObjCInterfaceDecl>::LatestDeclLink(
+                                              cast<ObjCInterfaceDecl>(Latest));
+  } else if (ObjCProtocolDecl *PD = dyn_cast<ObjCProtocolDecl>(D)) {
+    PD->RedeclLink
+      = Redeclarable<ObjCProtocolDecl>::LatestDeclLink(
+                                                cast<ObjCProtocolDecl>(Latest));
+  } else if (NamespaceDecl *ND = dyn_cast<NamespaceDecl>(D)) {
+    ND->RedeclLink
+      = Redeclarable<NamespaceDecl>::LatestDeclLink(
+                                                   cast<NamespaceDecl>(Latest));
+  } else {
+    RedeclarableTemplateDecl *TD = cast<RedeclarableTemplateDecl>(D);
+    TD->RedeclLink
+      = Redeclarable<RedeclarableTemplateDecl>::LatestDeclLink(
+                                        cast<RedeclarableTemplateDecl>(Latest));
+  }
+}
+
+ASTReader::MergedDeclsMap::iterator
+ASTReader::combineStoredMergedDecls(Decl *Canon, GlobalDeclID CanonID) {
+  // If we don't have any stored merged declarations, just look in the
+  // merged declarations set.
+  StoredMergedDeclsMap::iterator StoredPos = StoredMergedDecls.find(CanonID);
+  if (StoredPos == StoredMergedDecls.end())
+    return MergedDecls.find(Canon);
+
+  // Append the stored merged declarations to the merged declarations set.
+  MergedDeclsMap::iterator Pos = MergedDecls.find(Canon);
+  if (Pos == MergedDecls.end())
+    Pos = MergedDecls.insert(std::make_pair(Canon, 
+                                            SmallVector<DeclID, 2>())).first;
+  Pos->second.append(StoredPos->second.begin(), StoredPos->second.end());
+  StoredMergedDecls.erase(StoredPos);
+  
+  // Sort and uniquify the set of merged declarations.
+  llvm::array_pod_sort(Pos->second.begin(), Pos->second.end());
+  Pos->second.erase(std::unique(Pos->second.begin(), Pos->second.end()),
+                    Pos->second.end());
+  return Pos;
+}
+
 void ASTReader::loadAndAttachPreviousDecl(Decl *D, serialization::DeclID ID) {
   Decl *previous = GetDecl(ID);
   ASTDeclReader::attachPreviousDecl(D, previous);
@@ -1469,7 +1879,8 @@ void ASTReader::loadAndAttachPreviousDecl(Decl *D, serialization::DeclID ID) {
 /// \brief Read the declaration at the given offset from the AST file.
 Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   unsigned Index = ID - NUM_PREDEF_DECL_IDS;
-  RecordLocation Loc = DeclCursorForID(ID);
+  unsigned RawLocation = 0;
+  RecordLocation Loc = DeclCursorForID(ID, RawLocation);
   llvm::BitstreamCursor &DeclsCursor = Loc.F->DeclsCursor;
   // Keep track of where we are in the stream, then jump back there
   // after reading this declaration.
@@ -1484,7 +1895,7 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   RecordData Record;
   unsigned Code = DeclsCursor.ReadCode();
   unsigned Idx = 0;
-  ASTDeclReader Reader(*this, *Loc.F, DeclsCursor, ID, Record, Idx);
+  ASTDeclReader Reader(*this, *Loc.F, DeclsCursor, ID, RawLocation, Record,Idx);
 
   Decl *D = 0;
   switch ((DeclCode)DeclsCursor.ReadRecord(Code, Record)) {
@@ -1492,222 +1903,177 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   case DECL_CONTEXT_VISIBLE:
     llvm_unreachable("Record cannot be de-serialized with ReadDeclRecord");
   case DECL_TYPEDEF:
-    D = TypedefDecl::Create(Context, 0, SourceLocation(), SourceLocation(),
-                            0, 0);
+    D = TypedefDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_TYPEALIAS:
-    D = TypeAliasDecl::Create(Context, 0, SourceLocation(), SourceLocation(),
-                              0, 0);
+    D = TypeAliasDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_ENUM:
-    D = EnumDecl::Create(Context, Decl::EmptyShell());
+    D = EnumDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_RECORD:
-    D = RecordDecl::Create(Context, Decl::EmptyShell());
+    D = RecordDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_ENUM_CONSTANT:
-    D = EnumConstantDecl::Create(Context, 0, SourceLocation(), 0, QualType(),
-                                 0, llvm::APSInt());
+    D = EnumConstantDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_FUNCTION:
-    D = FunctionDecl::Create(Context, 0, SourceLocation(), SourceLocation(),
-                             DeclarationName(), QualType(), 0);
+    D = FunctionDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_LINKAGE_SPEC:
-    D = LinkageSpecDecl::Create(Context, 0, SourceLocation(), SourceLocation(),
-                                (LinkageSpecDecl::LanguageIDs)0,
-                                SourceLocation());
+    D = LinkageSpecDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_LABEL:
-    D = LabelDecl::Create(Context, 0, SourceLocation(), 0);
+    D = LabelDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_NAMESPACE:
-    D = NamespaceDecl::Create(Context, 0, SourceLocation(),
-                              SourceLocation(), 0);
+    D = NamespaceDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_NAMESPACE_ALIAS:
-    D = NamespaceAliasDecl::Create(Context, 0, SourceLocation(),
-                                   SourceLocation(), 0, 
-                                   NestedNameSpecifierLoc(),
-                                   SourceLocation(), 0);
+    D = NamespaceAliasDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_USING:
-    D = UsingDecl::Create(Context, 0, SourceLocation(),
-                          NestedNameSpecifierLoc(), DeclarationNameInfo(), 
-                          false);
+    D = UsingDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_USING_SHADOW:
-    D = UsingShadowDecl::Create(Context, 0, SourceLocation(), 0, 0);
+    D = UsingShadowDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_USING_DIRECTIVE:
-    D = UsingDirectiveDecl::Create(Context, 0, SourceLocation(),
-                                   SourceLocation(), NestedNameSpecifierLoc(),
-                                   SourceLocation(), 0, 0);
+    D = UsingDirectiveDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_UNRESOLVED_USING_VALUE:
-    D = UnresolvedUsingValueDecl::Create(Context, 0, SourceLocation(),
-                                         NestedNameSpecifierLoc(), 
-                                         DeclarationNameInfo());
+    D = UnresolvedUsingValueDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_UNRESOLVED_USING_TYPENAME:
-    D = UnresolvedUsingTypenameDecl::Create(Context, 0, SourceLocation(),
-                                            SourceLocation(), 
-                                            NestedNameSpecifierLoc(),
-                                            SourceLocation(),
-                                            DeclarationName());
+    D = UnresolvedUsingTypenameDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_CXX_RECORD:
-    D = CXXRecordDecl::Create(Context, Decl::EmptyShell());
+    D = CXXRecordDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_CXX_METHOD:
-    D = CXXMethodDecl::Create(Context, 0, SourceLocation(),
-                              DeclarationNameInfo(), QualType(), 0,
-                              false, SC_None, false, false, SourceLocation());
+    D = CXXMethodDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_CXX_CONSTRUCTOR:
-    D = CXXConstructorDecl::Create(Context, Decl::EmptyShell());
+    D = CXXConstructorDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_CXX_DESTRUCTOR:
-    D = CXXDestructorDecl::Create(Context, Decl::EmptyShell());
+    D = CXXDestructorDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_CXX_CONVERSION:
-    D = CXXConversionDecl::Create(Context, Decl::EmptyShell());
+    D = CXXConversionDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_ACCESS_SPEC:
-    D = AccessSpecDecl::Create(Context, Decl::EmptyShell());
+    D = AccessSpecDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_FRIEND:
-    D = FriendDecl::Create(Context, Decl::EmptyShell());
+    D = FriendDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_FRIEND_TEMPLATE:
-    D = FriendTemplateDecl::Create(Context, Decl::EmptyShell());
+    D = FriendTemplateDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_CLASS_TEMPLATE:
-    D = ClassTemplateDecl::Create(Context, Decl::EmptyShell());
+    D = ClassTemplateDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_CLASS_TEMPLATE_SPECIALIZATION:
-    D = ClassTemplateSpecializationDecl::Create(Context, Decl::EmptyShell());
+    D = ClassTemplateSpecializationDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_CLASS_TEMPLATE_PARTIAL_SPECIALIZATION:
-    D = ClassTemplatePartialSpecializationDecl::Create(Context,
-                                                       Decl::EmptyShell());
+    D = ClassTemplatePartialSpecializationDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_CLASS_SCOPE_FUNCTION_SPECIALIZATION:
-    D = ClassScopeFunctionSpecializationDecl::Create(Context,
-                                                     Decl::EmptyShell());
+    D = ClassScopeFunctionSpecializationDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_FUNCTION_TEMPLATE:
-      D = FunctionTemplateDecl::Create(Context, Decl::EmptyShell());
+    D = FunctionTemplateDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_TEMPLATE_TYPE_PARM:
-    D = TemplateTypeParmDecl::Create(Context, Decl::EmptyShell());
+    D = TemplateTypeParmDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_NON_TYPE_TEMPLATE_PARM:
-    D = NonTypeTemplateParmDecl::Create(Context, 0, SourceLocation(),
-                                        SourceLocation(), 0, 0, 0, QualType(),
-                                        false, 0);
+    D = NonTypeTemplateParmDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_EXPANDED_NON_TYPE_TEMPLATE_PARM_PACK:
-    D = NonTypeTemplateParmDecl::Create(Context, 0, SourceLocation(),
-                                        SourceLocation(), 0, 0, 0, QualType(),
-                                        0, 0, Record[Idx++], 0);
+    D = NonTypeTemplateParmDecl::CreateDeserialized(Context, ID, Record[Idx++]);
     break;
   case DECL_TEMPLATE_TEMPLATE_PARM:
-    D = TemplateTemplateParmDecl::Create(Context, 0, SourceLocation(), 0, 0,
-                                         false, 0, 0);
+    D = TemplateTemplateParmDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_TYPE_ALIAS_TEMPLATE:
-    D = TypeAliasTemplateDecl::Create(Context, Decl::EmptyShell());
+    D = TypeAliasTemplateDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_STATIC_ASSERT:
-    D = StaticAssertDecl::Create(Context, 0, SourceLocation(), 0, 0,
-                                 SourceLocation());
+    D = StaticAssertDecl::CreateDeserialized(Context, ID);
     break;
-
   case DECL_OBJC_METHOD:
-    D = ObjCMethodDecl::Create(Context, SourceLocation(), SourceLocation(),
-                               Selector(), QualType(), 0, 0);
+    D = ObjCMethodDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_OBJC_INTERFACE:
-    D = ObjCInterfaceDecl::Create(Context, 0, SourceLocation(), 0);
+    D = ObjCInterfaceDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_OBJC_IVAR:
-    D = ObjCIvarDecl::Create(Context, 0, SourceLocation(), SourceLocation(),
-                             0, QualType(), 0, ObjCIvarDecl::None);
+    D = ObjCIvarDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_OBJC_PROTOCOL:
-    D = ObjCProtocolDecl::Create(Context, 0, 0, SourceLocation(),
-                                 SourceLocation());
+    D = ObjCProtocolDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_OBJC_AT_DEFS_FIELD:
-    D = ObjCAtDefsFieldDecl::Create(Context, 0, SourceLocation(),
-                                    SourceLocation(), 0, QualType(), 0);
-    break;
-  case DECL_OBJC_CLASS:
-    D = ObjCClassDecl::Create(Context, 0, SourceLocation());
-    break;
-  case DECL_OBJC_FORWARD_PROTOCOL:
-    D = ObjCForwardProtocolDecl::Create(Context, 0, SourceLocation());
+    D = ObjCAtDefsFieldDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_OBJC_CATEGORY:
-    D = ObjCCategoryDecl::Create(Context, Decl::EmptyShell());
+    D = ObjCCategoryDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_OBJC_CATEGORY_IMPL:
-    D = ObjCCategoryImplDecl::Create(Context, 0, 0, 0, SourceLocation(),
-                                     SourceLocation());
+    D = ObjCCategoryImplDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_OBJC_IMPLEMENTATION:
-    D = ObjCImplementationDecl::Create(Context, 0, 0, 0, SourceLocation(),
-                                       SourceLocation());
+    D = ObjCImplementationDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_OBJC_COMPATIBLE_ALIAS:
-    D = ObjCCompatibleAliasDecl::Create(Context, 0, SourceLocation(), 0, 0);
+    D = ObjCCompatibleAliasDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_OBJC_PROPERTY:
-    D = ObjCPropertyDecl::Create(Context, 0, SourceLocation(), 0, SourceLocation(),
-                                 0);
+    D = ObjCPropertyDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_OBJC_PROPERTY_IMPL:
-    D = ObjCPropertyImplDecl::Create(Context, 0, SourceLocation(),
-                                     SourceLocation(), 0,
-                                     ObjCPropertyImplDecl::Dynamic, 0,
-                                     SourceLocation());
+    D = ObjCPropertyImplDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_FIELD:
-    D = FieldDecl::Create(Context, 0, SourceLocation(), SourceLocation(), 0,
-                          QualType(), 0, 0, false, false);
+    D = FieldDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_INDIRECTFIELD:
-    D = IndirectFieldDecl::Create(Context, 0, SourceLocation(), 0, QualType(),
-                                  0, 0);
+    D = IndirectFieldDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_VAR:
-    D = VarDecl::Create(Context, 0, SourceLocation(), SourceLocation(), 0,
-                        QualType(), 0, SC_None, SC_None);
+    D = VarDecl::CreateDeserialized(Context, ID);
     break;
-
   case DECL_IMPLICIT_PARAM:
-    D = ImplicitParamDecl::Create(Context, 0, SourceLocation(), 0, QualType());
+    D = ImplicitParamDecl::CreateDeserialized(Context, ID);
     break;
-
   case DECL_PARM_VAR:
-    D = ParmVarDecl::Create(Context, 0, SourceLocation(), SourceLocation(), 0,
-                            QualType(), 0, SC_None, SC_None, 0);
+    D = ParmVarDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_FILE_SCOPE_ASM:
-    D = FileScopeAsmDecl::Create(Context, 0, 0, SourceLocation(),
-                                 SourceLocation());
+    D = FileScopeAsmDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_BLOCK:
-    D = BlockDecl::Create(Context, 0, SourceLocation());
+    D = BlockDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_CXX_BASE_SPECIFIERS:
     Error("attempt to read a C++ base-specifier record as a declaration");
     return 0;
+  case DECL_IMPORT:
+    // Note: last entry of the ImportDecl record is the number of stored source 
+    // locations.
+    D = ImportDecl::CreateDeserialized(Context, ID, Record.back());
+    break;
   }
 
   assert(D && "Unknown declaration reading AST file");
   LoadedDecl(Index, D);
+  // Set the DeclContext before doing any deserialization, to make sure internal
+  // calls to Decl::getASTContext() by Decl's methods will find the
+  // TranslationUnitDecl without crashing.
+  D->setDeclContext(Context.getTranslationUnitDecl());
   Reader.Visit(D);
 
   // If this declaration is also a declaration context, get the
@@ -1743,16 +2109,18 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
 
   // Load any relevant update records.
   loadDeclUpdateRecords(ID, D);
-  
-  if (ObjCChainedCategoriesInterfaces.count(ID))
-    loadObjCChainedCategories(ID, cast<ObjCInterfaceDecl>(D));
+
+  // Load the categories after recursive loading is finished.
+  if (ObjCInterfaceDecl *Class = dyn_cast<ObjCInterfaceDecl>(D))
+    if (Class->isThisDeclarationADefinition())
+      loadObjCCategories(ID, Class);
   
   // If we have deserialized a declaration that has a definition the
   // AST consumer might need to know about, queue it.
   // We don't pass it to the consumer immediately because we may be in recursive
   // loading, and some declarations may still be initializing.
   if (isConsumerInterestedIn(D))
-      InterestingDecls.push_back(D);
+    InterestingDecls.push_back(D);
   
   return D;
 }
@@ -1766,7 +2134,7 @@ void ASTReader::loadDeclUpdateRecords(serialization::DeclID ID, Decl *D) {
     FileOffsetsTy &UpdateOffsets = UpdI->second;
     for (FileOffsetsTy::iterator
          I = UpdateOffsets.begin(), E = UpdateOffsets.end(); I != E; ++I) {
-      Module *F = I->first;
+      ModuleFile *F = I->first;
       uint64_t Offset = I->second;
       llvm::BitstreamCursor &Cursor = F->DeclsCursor;
       SavedStreamPosition SavedPosition(Cursor);
@@ -1778,179 +2146,328 @@ void ASTReader::loadDeclUpdateRecords(serialization::DeclID ID, Decl *D) {
       assert(RecCode == DECL_UPDATES && "Expected DECL_UPDATES record!");
       
       unsigned Idx = 0;
-      ASTDeclReader Reader(*this, *F, Cursor, ID, Record, Idx);
+      ASTDeclReader Reader(*this, *F, Cursor, ID, 0, Record, Idx);
       Reader.UpdateDecl(D, *F, Record);
     }
   }
 }
 
 namespace {
-  /// \brief Given an ObjC interface, goes through the modules and links to the
-  /// interface all the categories for it.
-  class ObjCChainedCategoriesVisitor {
-    ASTReader &Reader;
-    serialization::GlobalDeclID InterfaceID;
-    ObjCInterfaceDecl *Interface;
-    ObjCCategoryDecl *GlobHeadCat, *GlobTailCat;
-    llvm::DenseMap<DeclarationName, ObjCCategoryDecl *> NameCategoryMap;
-
-  public:
-    ObjCChainedCategoriesVisitor(ASTReader &Reader,
-                                 serialization::GlobalDeclID InterfaceID,
-                                 ObjCInterfaceDecl *Interface)
-      : Reader(Reader), InterfaceID(InterfaceID), Interface(Interface),
-        GlobHeadCat(0), GlobTailCat(0) { }
-
-    static bool visit(Module &M, void *UserData) {
-      return static_cast<ObjCChainedCategoriesVisitor *>(UserData)->visit(M);
+  struct CompareLocalRedeclarationsInfoToID {
+    bool operator()(const LocalRedeclarationsInfo &X, DeclID Y) {
+      return X.FirstID < Y;
     }
 
-    bool visit(Module &M) {
-      if (Reader.isDeclIDFromModule(InterfaceID, M))
-        return true; // We reached the module where the interface originated
-                    // from. Stop traversing the imported modules.
+    bool operator()(DeclID X, const LocalRedeclarationsInfo &Y) {
+      return X < Y.FirstID;
+    }
 
-      Module::ChainedObjCCategoriesMap::iterator
-        I = M.ChainedObjCCategories.find(InterfaceID);
-      if (I == M.ChainedObjCCategories.end())
+    bool operator()(const LocalRedeclarationsInfo &X, 
+                    const LocalRedeclarationsInfo &Y) {
+      return X.FirstID < Y.FirstID;
+    }
+    bool operator()(DeclID X, DeclID Y) {
+      return X < Y;
+    }
+  };
+  
+  /// \brief Module visitor class that finds all of the redeclarations of a 
+  /// 
+  class RedeclChainVisitor {
+    ASTReader &Reader;
+    SmallVectorImpl<DeclID> &SearchDecls;
+    llvm::SmallPtrSet<Decl *, 16> &Deserialized;
+    GlobalDeclID CanonID;
+    llvm::SmallVector<Decl *, 4> Chain;
+    
+  public:
+    RedeclChainVisitor(ASTReader &Reader, SmallVectorImpl<DeclID> &SearchDecls,
+                       llvm::SmallPtrSet<Decl *, 16> &Deserialized,
+                       GlobalDeclID CanonID)
+      : Reader(Reader), SearchDecls(SearchDecls), Deserialized(Deserialized),
+        CanonID(CanonID) { 
+      for (unsigned I = 0, N = SearchDecls.size(); I != N; ++I)
+        addToChain(Reader.GetDecl(SearchDecls[I]));
+    }
+    
+    static bool visit(ModuleFile &M, bool Preorder, void *UserData) {
+      if (Preorder)
         return false;
-
-      ObjCCategoryDecl *
-        HeadCat = Reader.GetLocalDeclAs<ObjCCategoryDecl>(M, I->second.first);
-      ObjCCategoryDecl *
-        TailCat = Reader.GetLocalDeclAs<ObjCCategoryDecl>(M, I->second.second);
-
-      addCategories(HeadCat, TailCat);
-      return false;
+      
+      return static_cast<RedeclChainVisitor *>(UserData)->visit(M);
     }
-
-    void addCategories(ObjCCategoryDecl *HeadCat,
-                       ObjCCategoryDecl *TailCat = 0) {
-      if (!HeadCat) {
-        assert(!TailCat);
+    
+    void addToChain(Decl *D) {
+      if (!D)
         return;
+      
+      if (Deserialized.count(D)) {
+        Deserialized.erase(D);
+        Chain.push_back(D);
       }
-
-      if (!TailCat) {
-        TailCat = HeadCat;
-        while (TailCat->getNextClassCategory())
-          TailCat = TailCat->getNextClassCategory();
+    }
+    
+    void searchForID(ModuleFile &M, GlobalDeclID GlobalID) {
+      // Map global ID of the first declaration down to the local ID
+      // used in this module file.
+      DeclID ID = Reader.mapGlobalIDToModuleFileGlobalID(M, GlobalID);
+      if (!ID)
+        return;
+      
+      // Perform a binary search to find the local redeclarations for this
+      // declaration (if any).
+      const LocalRedeclarationsInfo *Result
+        = std::lower_bound(M.RedeclarationsMap,
+                           M.RedeclarationsMap + M.LocalNumRedeclarationsInMap, 
+                           ID, CompareLocalRedeclarationsInfoToID());
+      if (Result == M.RedeclarationsMap + M.LocalNumRedeclarationsInMap ||
+          Result->FirstID != ID) {
+        // If we have a previously-canonical singleton declaration that was 
+        // merged into another redeclaration chain, create a trivial chain
+        // for this single declaration so that it will get wired into the 
+        // complete redeclaration chain.
+        if (GlobalID != CanonID && 
+            GlobalID - NUM_PREDEF_DECL_IDS >= M.BaseDeclID && 
+            GlobalID - NUM_PREDEF_DECL_IDS < M.BaseDeclID + M.LocalNumDecls) {
+          addToChain(Reader.GetDecl(GlobalID));
+        }
+        
+        return;
       }
+      
+      // Dig out all of the redeclarations.
+      unsigned Offset = Result->Offset;
+      unsigned N = M.RedeclarationChains[Offset];
+      M.RedeclarationChains[Offset++] = 0; // Don't try to deserialize again
+      for (unsigned I = 0; I != N; ++I)
+        addToChain(Reader.GetLocalDecl(M, M.RedeclarationChains[Offset++]));
+    }
+    
+    bool visit(ModuleFile &M) {
+      // Visit each of the declarations.
+      for (unsigned I = 0, N = SearchDecls.size(); I != N; ++I)
+        searchForID(M, SearchDecls[I]);
+      return false;
+    }
+    
+    ArrayRef<Decl *> getChain() const {
+      return Chain;
+    }
+  };
+}
 
-      if (!GlobHeadCat) {
-        GlobHeadCat = HeadCat;
-        GlobTailCat = TailCat;
-      } else {
-        ASTDeclReader::setNextObjCCategory(GlobTailCat, HeadCat);
-        GlobTailCat = TailCat;
-      }
+void ASTReader::loadPendingDeclChain(serialization::GlobalDeclID ID) {
+  Decl *D = GetDecl(ID);  
+  Decl *CanonDecl = D->getCanonicalDecl();
+  
+  // Determine the set of declaration IDs we'll be searching for.
+  llvm::SmallVector<DeclID, 1> SearchDecls;
+  GlobalDeclID CanonID = 0;
+  if (D == CanonDecl) {
+    SearchDecls.push_back(ID); // Always first.
+    CanonID = ID;
+  }
+  MergedDeclsMap::iterator MergedPos = combineStoredMergedDecls(CanonDecl, ID);
+  if (MergedPos != MergedDecls.end())
+    SearchDecls.append(MergedPos->second.begin(), MergedPos->second.end());  
+  
+  // Build up the list of redeclarations.
+  RedeclChainVisitor Visitor(*this, SearchDecls, RedeclsDeserialized, CanonID);
+  ModuleMgr.visitDepthFirst(&RedeclChainVisitor::visit, &Visitor);
+  
+  // Retrieve the chains.
+  ArrayRef<Decl *> Chain = Visitor.getChain();
+  if (Chain.empty())
+    return;
+    
+  // Hook up the chains.
+  Decl *MostRecent = CanonDecl->getMostRecentDecl();
+  for (unsigned I = 0, N = Chain.size(); I != N; ++I) {
+    if (Chain[I] == CanonDecl)
+      continue;
+    
+    ASTDeclReader::attachPreviousDecl(Chain[I], MostRecent);
+    MostRecent = Chain[I];
+  }
+  
+  ASTDeclReader::attachLatestDecl(CanonDecl, MostRecent);  
+}
 
-      llvm::DenseSet<DeclarationName> Checked;
-      for (ObjCCategoryDecl *Cat = HeadCat,
-                            *CatEnd = TailCat->getNextClassCategory();
-             Cat != CatEnd; Cat = Cat->getNextClassCategory()) {
-        if (Checked.count(Cat->getDeclName()))
-          continue;
-        Checked.insert(Cat->getDeclName());
-        checkForDuplicate(Cat);
-      }
+namespace {
+  struct CompareObjCCategoriesInfo {
+    bool operator()(const ObjCCategoriesInfo &X, DeclID Y) {
+      return X.DefinitionID < Y;
     }
+    
+    bool operator()(DeclID X, const ObjCCategoriesInfo &Y) {
+      return X < Y.DefinitionID;
+    }
+    
+    bool operator()(const ObjCCategoriesInfo &X, 
+                    const ObjCCategoriesInfo &Y) {
+      return X.DefinitionID < Y.DefinitionID;
+    }
+    bool operator()(DeclID X, DeclID Y) {
+      return X < Y;
+    }
+  };
 
-    /// \brief Warns for duplicate categories that come from different modules.
-    void checkForDuplicate(ObjCCategoryDecl *Cat) {
-      DeclarationName Name = Cat->getDeclName();
-      // Find the top category with the same name. We do not want to warn for
-      // duplicates along the established chain because there were already
-      // warnings for them when the module was created. We only want to warn for
-      // duplicates between non-dependent modules:
-      //
-      //   MT     //
-      //  /  \    //
-      // ML  MR   //
-      //
-      // We want to warn for duplicates between ML and MR,not between ML and MT.
-      //
-      // FIXME: We should not warn for duplicates in diamond:
-      //
-      //   MT     //
-      //  /  \    //
-      // ML  MR   //
-      //  \  /    //
-      //   MB     //
-      //
-      // If there are duplicates in ML/MR, there will be warning when creating
-      // MB *and* when importing MB. We should not warn when importing.
-      for (ObjCCategoryDecl *Next = Cat->getNextClassCategory(); Next;
-             Next = Next->getNextClassCategory()) {
-        if (Next->getDeclName() == Name)
-          Cat = Next;
+  /// \brief Given an ObjC interface, goes through the modules and links to the
+  /// interface all the categories for it.
+  class ObjCCategoriesVisitor {
+    ASTReader &Reader;
+    serialization::GlobalDeclID InterfaceID;
+    ObjCInterfaceDecl *Interface;
+    llvm::SmallPtrSet<ObjCCategoryDecl *, 16> &Deserialized;
+    unsigned PreviousGeneration;
+    ObjCCategoryDecl *Tail;
+    llvm::DenseMap<DeclarationName, ObjCCategoryDecl *> NameCategoryMap;
+    
+    void add(ObjCCategoryDecl *Cat) {
+      // Only process each category once.
+      if (!Deserialized.count(Cat))
+        return;
+      Deserialized.erase(Cat);
+      
+      // Check for duplicate categories.
+      if (Cat->getDeclName()) {
+        ObjCCategoryDecl *&Existing = NameCategoryMap[Cat->getDeclName()];
+        if (Existing && 
+            Reader.getOwningModuleFile(Existing) 
+                                          != Reader.getOwningModuleFile(Cat)) {
+          // FIXME: We should not warn for duplicates in diamond:
+          //
+          //   MT     //
+          //  /  \    //
+          // ML  MR   //
+          //  \  /    //
+          //   MB     //
+          //
+          // If there are duplicates in ML/MR, there will be warning when 
+          // creating MB *and* when importing MB. We should not warn when 
+          // importing.
+          Reader.Diag(Cat->getLocation(), diag::warn_dup_category_def)
+            << Interface->getDeclName() << Cat->getDeclName();
+          Reader.Diag(Existing->getLocation(), diag::note_previous_definition);
+        } else if (!Existing) {
+          // Record this category.
+          Existing = Cat;
+        }
+      }
+      
+      // Add this category to the end of the chain.
+      if (Tail)
+        ASTDeclReader::setNextObjCCategory(Tail, Cat);
+      else
+        Interface->setCategoryList(Cat);
+      Tail = Cat;
+    }
+    
+  public:
+    ObjCCategoriesVisitor(ASTReader &Reader,
+                          serialization::GlobalDeclID InterfaceID,
+                          ObjCInterfaceDecl *Interface,
+                        llvm::SmallPtrSet<ObjCCategoryDecl *, 16> &Deserialized,
+                          unsigned PreviousGeneration)
+      : Reader(Reader), InterfaceID(InterfaceID), Interface(Interface),
+        Deserialized(Deserialized), PreviousGeneration(PreviousGeneration),
+        Tail(0) 
+    {
+      // Populate the name -> category map with the set of known categories.
+      for (ObjCCategoryDecl *Cat = Interface->getCategoryList(); Cat;
+           Cat = Cat->getNextClassCategory()) {
+        if (Cat->getDeclName())
+          NameCategoryMap[Cat->getDeclName()] = Cat;
+        
+        // Keep track of the tail of the category list.
+        Tail = Cat;
       }
+    }
 
-      ObjCCategoryDecl *&PrevCat = NameCategoryMap[Name];
-      if (!PrevCat)
-        PrevCat = Cat;
+    static bool visit(ModuleFile &M, void *UserData) {
+      return static_cast<ObjCCategoriesVisitor *>(UserData)->visit(M);
+    }
 
-      if (PrevCat != Cat) {
-        Reader.Diag(Cat->getLocation(), diag::warn_dup_category_def)
-          << Interface->getDeclName() << Name;
-        Reader.Diag(PrevCat->getLocation(), diag::note_previous_definition);
+    bool visit(ModuleFile &M) {
+      // If we've loaded all of the category information we care about from
+      // this module file, we're done.
+      if (M.Generation <= PreviousGeneration)
+        return true;
+      
+      // Map global ID of the definition down to the local ID used in this 
+      // module file. If there is no such mapping, we'll find nothing here
+      // (or in any module it imports).
+      DeclID LocalID = Reader.mapGlobalIDToModuleFileGlobalID(M, InterfaceID);
+      if (!LocalID)
+        return true;
+
+      // Perform a binary search to find the local redeclarations for this
+      // declaration (if any).
+      const ObjCCategoriesInfo *Result
+        = std::lower_bound(M.ObjCCategoriesMap,
+                           M.ObjCCategoriesMap + M.LocalNumObjCCategoriesInMap, 
+                           LocalID, CompareObjCCategoriesInfo());
+      if (Result == M.ObjCCategoriesMap + M.LocalNumObjCCategoriesInMap ||
+          Result->DefinitionID != LocalID) {
+        // We didn't find anything. If the class definition is in this module
+        // file, then the module files it depends on cannot have any categories,
+        // so suppress further lookup.
+        return Reader.isDeclIDFromModule(InterfaceID, M);
       }
+      
+      // We found something. Dig out all of the categories.
+      unsigned Offset = Result->Offset;
+      unsigned N = M.ObjCCategories[Offset];
+      M.ObjCCategories[Offset++] = 0; // Don't try to deserialize again
+      for (unsigned I = 0; I != N; ++I)
+        add(cast_or_null<ObjCCategoryDecl>(
+              Reader.GetLocalDecl(M, M.ObjCCategories[Offset++])));
+      return true;
     }
-
-    ObjCCategoryDecl *getHeadCategory() const { return GlobHeadCat; }
   };
 }
 
-void ASTReader::loadObjCChainedCategories(serialization::GlobalDeclID ID,
-                                          ObjCInterfaceDecl *D) {
-  ObjCChainedCategoriesVisitor Visitor(*this, ID, D);
-  ModuleMgr.visit(ObjCChainedCategoriesVisitor::visit, &Visitor);
-  // Also add the categories that the interface already links to.
-  Visitor.addCategories(D->getCategoryList());
-  D->setCategoryList(Visitor.getHeadCategory());
+void ASTReader::loadObjCCategories(serialization::GlobalDeclID ID,
+                                   ObjCInterfaceDecl *D,
+                                   unsigned PreviousGeneration) {
+  ObjCCategoriesVisitor Visitor(*this, ID, D, CategoriesDeserialized,
+                                PreviousGeneration);
+  ModuleMgr.visit(ObjCCategoriesVisitor::visit, &Visitor);
 }
 
-void ASTDeclReader::UpdateDecl(Decl *D, Module &Module,
+void ASTDeclReader::UpdateDecl(Decl *D, ModuleFile &ModuleFile,
                                const RecordData &Record) {
   unsigned Idx = 0;
   while (Idx < Record.size()) {
     switch ((DeclUpdateKind)Record[Idx++]) {
-    case UPD_CXX_SET_DEFINITIONDATA: {
-      CXXRecordDecl *RD = cast<CXXRecordDecl>(D);
-      CXXRecordDecl *DefinitionDecl
-        = Reader.ReadDeclAs<CXXRecordDecl>(Module, Record, Idx);
-      assert(!RD->DefinitionData && "DefinitionData is already set!");
-      InitializeCXXDefinitionData(RD, DefinitionDecl, Record, Idx);
-      break;
-    }
-
     case UPD_CXX_ADDED_IMPLICIT_MEMBER:
-      cast<CXXRecordDecl>(D)->addedMember(Reader.ReadDecl(Module, Record, Idx));
+      cast<CXXRecordDecl>(D)->addedMember(Reader.ReadDecl(ModuleFile, Record, Idx));
       break;
 
     case UPD_CXX_ADDED_TEMPLATE_SPECIALIZATION:
       // It will be added to the template's specializations set when loaded.
-      (void)Reader.ReadDecl(Module, Record, Idx);
+      (void)Reader.ReadDecl(ModuleFile, Record, Idx);
       break;
 
     case UPD_CXX_ADDED_ANONYMOUS_NAMESPACE: {
       NamespaceDecl *Anon
-        = Reader.ReadDeclAs<NamespaceDecl>(Module, Record, Idx);
-      // Guard against these being loaded out of original order. Don't use
-      // getNextNamespace(), since it tries to access the context and can't in
-      // the middle of deserialization.
-      if (!Anon->NextNamespace) {
+        = Reader.ReadDeclAs<NamespaceDecl>(ModuleFile, Record, Idx);
+      
+      // Each module has its own anonymous namespace, which is disjoint from
+      // any other module's anonymous namespaces, so don't attach the anonymous
+      // namespace at all.
+      if (ModuleFile.Kind != MK_Module) {
         if (TranslationUnitDecl *TU = dyn_cast<TranslationUnitDecl>(D))
           TU->setAnonymousNamespace(Anon);
         else
-          cast<NamespaceDecl>(D)->OrigOrAnonNamespace.setPointer(Anon);
+          cast<NamespaceDecl>(D)->setAnonymousNamespace(Anon);
       }
       break;
     }
 
     case UPD_CXX_INSTANTIATED_STATIC_DATA_MEMBER:
       cast<VarDecl>(D)->getMemberSpecializationInfo()->setPointOfInstantiation(
-          Reader.ReadSourceLocation(Module, Record, Idx));
+          Reader.ReadSourceLocation(ModuleFile, Record, Idx));
       break;
     }
   }