diff --git a/clang/include/clang/Frontend/PCHReader.h b/clang/include/clang/Frontend/PCHReader.h
index 3d29fccf8f19..0e1904f018a5 100644
--- a/clang/include/clang/Frontend/PCHReader.h
+++ b/clang/include/clang/Frontend/PCHReader.h
@@ -583,7 +583,7 @@ public:
   void InitializeContext(ASTContext &Context);
 
   /// \brief Retrieve the name of the PCH file
-  const std::string &getFileName() { return FileName; }
+  const std::string &getFileName() const { return FileName; }
 
   /// \brief Retrieve the name of the original source file name
   const std::string &getOriginalSourceFile() { return OriginalFileName; }
diff --git a/clang/include/clang/Frontend/PCHWriter.h b/clang/include/clang/Frontend/PCHWriter.h
index 0b0c866bd6df..c23dde6fd59d 100644
--- a/clang/include/clang/Frontend/PCHWriter.h
+++ b/clang/include/clang/Frontend/PCHWriter.h
@@ -220,7 +220,7 @@ private:
   void WriteSubStmt(Stmt *S);
 
   void WriteBlockInfoBlock();
-  void WriteMetadata(ASTContext &Context, const char *isysroot);
+  void WriteMetadata(ASTContext &Context, const PCHReader *Chain, const char *isysroot);
   void WriteLanguageOptions(const LangOptions &LangOpts);
   void WriteStatCache(MemorizeStatCalls &StatCalls, const char* isysroot);
   void WriteSourceManagerBlock(SourceManager &SourceMgr,
diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index b761f30adf4f..dbbf69c8b12c 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -111,11 +111,10 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
   /// action.
   if (!usesPreprocessorOnly()) {
     CI.createASTContext();
-    CI.setASTConsumer(CreateASTConsumer(CI, Filename));
-    if (!CI.hasASTConsumer())
-      goto failure;
 
-    /// Use PCH?
+    /// Use PCH? If so, we want the PCHReader active before the consumer
+    /// is created, because the consumer might be interested in the reader
+    /// (e.g. the PCH writer for chaining).
     if (!CI.getPreprocessorOpts().ImplicitPCHInclude.empty()) {
       assert(hasPCHSupport() && "This action does not have PCH support!");
       CI.createPCHExternalASTSource(
@@ -123,6 +122,10 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
       if (!CI.getASTContext().getExternalSource())
         goto failure;
     }
+
+    CI.setASTConsumer(CreateASTConsumer(CI, Filename));
+    if (!CI.hasASTConsumer())
+      goto failure;
   }
 
   // Initialize builtin info as long as we aren't using an external AST
diff --git a/clang/lib/Frontend/PCHWriter.cpp b/clang/lib/Frontend/PCHWriter.cpp
index 47347cac5eee..10701d1a25e1 100644
--- a/clang/lib/Frontend/PCHWriter.cpp
+++ b/clang/lib/Frontend/PCHWriter.cpp
@@ -20,6 +20,7 @@
 #include "clang/AST/Expr.h"
 #include "clang/AST/Type.h"
 #include "clang/AST/TypeLocVisitor.h"
+#include "clang/Frontend/PCHReader.h"
 #include "clang/Lex/MacroInfo.h"
 #include "clang/Lex/PreprocessingRecord.h"
 #include "clang/Lex/Preprocessor.h"
@@ -742,30 +743,34 @@ adjustFilenameForRelocatablePCH(const char *Filename, const char *isysroot) {
 }
 
 /// \brief Write the PCH metadata (e.g., i686-apple-darwin9).
-void PCHWriter::WriteMetadata(ASTContext &Context, const char *isysroot) {
+void PCHWriter::WriteMetadata(ASTContext &Context, const PCHReader *Chain,
+                              const char *isysroot) {
   using namespace llvm;
 
   // Metadata
   const TargetInfo &Target = Context.Target;
   BitCodeAbbrev *MetaAbbrev = new BitCodeAbbrev();
-  MetaAbbrev->Add(BitCodeAbbrevOp(pch::METADATA));
+  MetaAbbrev->Add(BitCodeAbbrevOp(
+                    Chain ? pch::CHAINED_METADATA : pch::METADATA));
   MetaAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 16)); // PCH major
   MetaAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 16)); // PCH minor
   MetaAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 16)); // Clang major
   MetaAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 16)); // Clang minor
   MetaAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // Relocatable
-  MetaAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob)); // Target triple
+  // Target triple or chained PCH name
+  MetaAbbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob));
   unsigned MetaAbbrevCode = Stream.EmitAbbrev(MetaAbbrev);
 
   RecordData Record;
-  Record.push_back(pch::METADATA);
+  Record.push_back(Chain ? pch::CHAINED_METADATA : pch::METADATA);
   Record.push_back(pch::VERSION_MAJOR);
   Record.push_back(pch::VERSION_MINOR);
   Record.push_back(CLANG_VERSION_MAJOR);
   Record.push_back(CLANG_VERSION_MINOR);
   Record.push_back(isysroot != 0);
-  const std::string &TripleStr = Target.getTriple().getTriple();
-  Stream.EmitRecordWithBlob(MetaAbbrevCode, Record, TripleStr);
+  // FIXME: This writes the absolute path for chained headers.
+  const std::string &BlobStr = Chain ? Chain->getFileName() : Target.getTriple().getTriple();
+  Stream.EmitRecordWithBlob(MetaAbbrevCode, Record, BlobStr);
 
   // Original file name
   SourceManager &SM = Context.getSourceManager();
@@ -2153,8 +2158,9 @@ void PCHWriter::WritePCH(Sema &SemaRef, MemorizeStatCalls *StatCalls,
   // Write the remaining PCH contents.
   RecordData Record;
   Stream.EnterSubblock(pch::PCH_BLOCK_ID, 5);
-  WriteMetadata(Context, isysroot);
-  WriteLanguageOptions(Context.getLangOptions());
+  WriteMetadata(Context, Chain, isysroot);
+  if (!Chain)
+    WriteLanguageOptions(Context.getLangOptions());
   if (StatCalls && !isysroot)
     WriteStatCache(*StatCalls, isysroot);
   WriteSourceManagerBlock(Context.getSourceManager(), PP, isysroot);