 +  ///
 +  void addSource(ExternalSemaSource &source);
 +
++  //===--------------------------------------------------------------------===//
++  // ExternalASTSource.
++  //===--------------------------------------------------------------------===//
++
++  /// \brief Resolve a declaration ID into a declaration, potentially
++  /// building a new declaration.
++  ///
++  /// This method only needs to be implemented if the AST source ever
++  /// passes back decl sets as VisibleDeclaration objects.
++  ///
++  /// The default implementation of this method is a no-op.
++  virtual Decl *GetExternalDecl(uint32_t ID);
++
++  /// \brief Resolve a selector ID into a selector.
++  ///
++  /// This operation only needs to be implemented if the AST source
++  /// returns non-zero for GetNumKnownSelectors().
++  ///
++  /// The default implementation of this method is a no-op.
++  virtual Selector GetExternalSelector(uint32_t ID);
++
++  /// \brief Returns the number of selectors known to the external AST
++  /// source.
++  ///
++  /// The default implementation of this method is a no-op.
++  virtual uint32_t GetNumExternalSelectors();
++
++  /// \brief Resolve the offset of a statement in the decl stream into
++  /// a statement.
++  ///
++  /// This operation is meant to be used via a LazyOffsetPtr.  It only
++  /// needs to be implemented if the AST source uses methods like
++  /// FunctionDecl::setLazyBody when building decls.
++  ///
++  /// The default implementation of this method is a no-op.
++  virtual Stmt *GetExternalDeclStmt(uint64_t Offset);
++
++  /// \brief Resolve the offset of a set of C++ base specifiers in the decl
++  /// stream into an array of specifiers.
++  ///
++  /// The default implementation of this method is a no-op.
++  virtual CXXBaseSpecifier *GetExternalCXXBaseSpecifiers(uint64_t Offset);
++
++  /// \brief Finds all declarations with the given name in the
++  /// given context.
++  ///
++  /// Generally the final step of this method is either to call
++  /// SetExternalVisibleDeclsForName or to recursively call lookup on
++  /// the DeclContext after calling SetExternalVisibleDecls.
++  ///
++  /// The default implementation of this method is a no-op.
++  virtual DeclContextLookupResult
++  FindExternalVisibleDeclsByName(const DeclContext *DC, DeclarationName Name);
++
++  /// \brief Ensures that the table of all visible declarations inside this
++  /// context is up to date.
++  ///
++  /// The default implementation of this functino is a no-op.
++  virtual void completeVisibleDeclsMap(const DeclContext *DC);
++
++  /// \brief Finds all declarations lexically contained within the given
++  /// DeclContext, after applying an optional filter predicate.
++  ///
++  /// \param isKindWeWant a predicate function that returns true if the passed
++  /// declaration kind is one we are looking for. If NULL, all declarations
++  /// are returned.
++  ///
++  /// \return an indication of whether the load succeeded or failed.
++  ///
++  /// The default implementation of this method is a no-op.
++  virtual ExternalLoadResult FindExternalLexicalDecls(const DeclContext *DC,
++                                        bool (*isKindWeWant)(Decl::Kind),
++                                        SmallVectorImpl<Decl*> &Result);
++
++  /// \brief Finds all declarations lexically contained within the given
++  /// DeclContext.
++  ///
++  /// \return true if an error occurred
++  ExternalLoadResult FindExternalLexicalDecls(const DeclContext *DC,
++                                SmallVectorImpl<Decl*> &Result) {
++    return FindExternalLexicalDecls(DC, 0, Result);
++  }
++
++  template <typename DeclTy>
++  ExternalLoadResult FindExternalLexicalDeclsBy(const DeclContext *DC,
++                                  SmallVectorImpl<Decl*> &Result) {
++    return FindExternalLexicalDecls(DC, DeclTy::classofKind, Result);
++  }
++
++  /// \brief Get the decls that are contained in a file in the Offset/Length
++  /// range. \p Length can be 0 to indicate a point at \p Offset instead of
++  /// a range. 
++  virtual void FindFileRegionDecls(FileID File, unsigned Offset,unsigned Length,
++                                   SmallVectorImpl<Decl *> &Decls);
++
++  /// \brief Gives the external AST source an opportunity to complete
++  /// an incomplete type.
++  virtual void CompleteType(TagDecl *Tag);
++
++  /// \brief Gives the external AST source an opportunity to complete an
++  /// incomplete Objective-C class.
++  ///
++  /// This routine will only be invoked if the "externally completed" bit is
++  /// set on the ObjCInterfaceDecl via the function 
++  /// \c ObjCInterfaceDecl::setExternallyCompleted().
++  virtual void CompleteType(ObjCInterfaceDecl *Class);
++
++  /// \brief Loads comment ranges.
++  virtual void ReadComments();
++
++  /// \brief Notify ExternalASTSource that we started deserialization of
++  /// a decl or type so until FinishedDeserializing is called there may be
++  /// decls that are initializing. Must be paired with FinishedDeserializing.
++  ///
++  /// The default implementation of this method is a no-op.
++  virtual void StartedDeserializing();
++
++  /// \brief Notify ExternalASTSource that we finished the deserialization of
++  /// a decl or type. Must be paired with StartedDeserializing.
++  ///
++  /// The default implementation of this method is a no-op.
++  virtual void FinishedDeserializing();
++
++  /// \brief Function that will be invoked when we begin parsing a new
++  /// translation unit involving this external AST source.
++  ///
++  /// The default implementation of this method is a no-op.
++  virtual void StartTranslationUnit(ASTConsumer *Consumer);
++
++  /// \brief Print any statistics that have been gathered regarding
++  /// the external AST source.
++  ///
++  /// The default implementation of this method is a no-op.
++  virtual void PrintStats();
++  
++  
++  /// \brief Perform layout on the given record.
++  ///
++  /// This routine allows the external AST source to provide an specific 
++  /// layout for a record, overriding the layout that would normally be
++  /// constructed. It is intended for clients who receive specific layout
++  /// details rather than source code (such as LLDB). The client is expected
++  /// to fill in the field offsets, base offsets, virtual base offsets, and
++  /// complete object size.
++  ///
++  /// \param Record The record whose layout is being requested.
++  ///
++  /// \param Size The final size of the record, in bits.
++  ///
++  /// \param Alignment The final alignment of the record, in bits.
++  ///
++  /// \param FieldOffsets The offset of each of the fields within the record,
++  /// expressed in bits. All of the fields must be provided with offsets.
++  ///
++  /// \param BaseOffsets The offset of each of the direct, non-virtual base
++  /// classes. If any bases are not given offsets, the bases will be laid 
++  /// out according to the ABI.
++  ///
++  /// \param VirtualBaseOffsets The offset of each of the virtual base classes
++  /// (either direct or not). If any bases are not given offsets, the bases will be laid 
++  /// out according to the ABI.
++  /// 
++  /// \returns true if the record layout was provided, false otherwise.
++  virtual bool 
++  layoutRecordType(const RecordDecl *Record,
++                   uint64_t &Size, uint64_t &Alignment,
++                   llvm::DenseMap<const FieldDecl *, uint64_t> &FieldOffsets,
++                 llvm::DenseMap<const CXXRecordDecl *, CharUnits> &BaseOffsets,
++           llvm::DenseMap<const CXXRecordDecl *, CharUnits> &VirtualBaseOffsets);
++
++  /// Return the amount of memory used by memory buffers, breaking down
++  /// by heap-backed versus mmap'ed memory.
++  virtual void getMemoryBufferSizes(MemoryBufferSizes &sizes) const;
++
++  //===--------------------------------------------------------------------===//
++  // ExternalSemaSource.
++  //===--------------------------------------------------------------------===// 
++
 +  /// \brief Initialize the semantic source with the Sema instance
 +  /// being used to perform semantic analysis on the abstract syntax
 +  /// tree.

===================================================================
--- tools/clang/include/clang/Sema/MultiplexExternalSemaSource.h	(revision 0)
+++ tools/clang/include/clang/Sema/MultiplexExternalSemaSource.h	(revision 0)
@@ -0,0 +1,188 @@
+//===--- MultiplexExternalSemaSource.h - External Sema Interface-*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure

===================================================================
--- tools/clang/lib/Sema/MultiplexExternalSemaSource.cpp	(revision 0)
+++ tools/clang/lib/Sema/MultiplexExternalSemaSource.cpp	(revision 0)
@@ -0,0 +1,270 @@
+//===--- MultiplexExternalSemaSource.cpp  ---------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
