3 files changed, 17 insertions, 2 deletions
diff --git a/include/clang/Frontend/PCHBitCodes.h b/include/clang/Frontend/PCHBitCodes.h
index 109a78bd88..a07060f800 100644
--- a/include/clang/Frontend/PCHBitCodes.h
+++ b/include/clang/Frontend/PCHBitCodes.h
@@ -245,8 +245,12 @@ namespace clang {
       /// declarations.
       TU_UPDATE_LEXICAL = 28,
 
+      /// \brief Record code for an update to first decls pointing to the
+      /// latest redeclarations.
+      REDECLS_UPDATE_LATEST = 29,
+
       /// \brief Record code for declarations that Sema keeps references of.
-      SEMA_DECL_REFS = 29
+      SEMA_DECL_REFS = 30
     };
 
     /// \brief Record types used within a source manager block.
diff --git a/include/clang/Frontend/PCHReader.h b/include/clang/Frontend/PCHReader.h
index dda15670b5..e19669ec7f 100644
--- a/include/clang/Frontend/PCHReader.h
+++ b/include/clang/Frontend/PCHReader.h
@@ -319,6 +319,11 @@ private:
   /// DeclContext.
   DeclContextOffsetsMap DeclContextOffsets;
 
+  typedef llvm::DenseMap<pch::DeclID, pch::DeclID> FirstLatestDeclIDMap;
+  /// \brief Map of first declarations from a chained PCH that point to the
+  /// most recent declarations in another PCH.
+  FirstLatestDeclIDMap FirstLatestDeclIDs;
+
   /// \brief Read the records that describe the contents of declcontexts.
   bool ReadDeclContextStorage(llvm::BitstreamCursor &Cursor,
                               const std::pair<uint64_t, uint64_t> &Offsets,
@@ -561,7 +566,7 @@ private:
   QualType ReadTypeRecord(unsigned Index);
   RecordLocation TypeCursorForIndex(unsigned Index);
   void LoadedDecl(unsigned Index, Decl *D);
-  Decl *ReadDeclRecord(unsigned Index);
+  Decl *ReadDeclRecord(unsigned Index, pch::DeclID ID);
   RecordLocation DeclCursorForIndex(unsigned Index);
 
   void PassInterestingDeclsToConsumer();
diff --git a/include/clang/Frontend/PCHWriter.h b/include/clang/Frontend/PCHWriter.h
index 92c7085bc6..3403c6e2d1 100644
--- a/include/clang/Frontend/PCHWriter.h
+++ b/include/clang/Frontend/PCHWriter.h
@@ -79,6 +79,7 @@ class PCHWriter : public PCHDeserializationListener {
 public:
   typedef llvm::SmallVector<uint64_t, 64> RecordData;
 
+  friend class PCHDeclWriter;
 private:
   /// \brief The bitstream writer used to emit this precompiled header.
   llvm::BitstreamWriter &Stream;
@@ -195,6 +196,11 @@ private:
   /// \brief Mapping from the macro definition indices in \c MacroDefinitions
   /// to the corresponding offsets within the preprocessor block.
   std::vector<uint32_t> MacroDefinitionOffsets;
+
+  typedef llvm::DenseMap<Decl *, Decl *> FirstLatestDeclMap;
+  /// \brief Map of first declarations from a chained PCH that point to the
+  /// most recent declarations in another PCH.
+  FirstLatestDeclMap FirstLatestDecls;
   
   /// \brief Declarations encountered that might be external
   /// definitions.