diff --git a/include/clang/Driver/CC1Options.td b/include/clang/Driver/CC1Options.td
index 4502401..72dca18 100644
--- a/include/clang/Driver/CC1Options.td
+++ b/include/clang/Driver/CC1Options.td
@@ -304,6 +304,9 @@
   HelpText<"Apply fix-it advice creating a file with the given suffix">;
 def parse_print_callbacks : Flag<"-parse-print-callbacks">,
   HelpText<"Run parser and print each callback invoked">;
+def print_preamble : Flag<"-print-preamble">,
+  HelpText<"Print the \"preamble\" of a file, which is a candidate for implicit"
+           " precompiled headers.">;
 def emit_html : Flag<"-emit-html">,
   HelpText<"Output input source as HTML">;
 def ast_print : Flag<"-ast-print">,
diff --git a/include/clang/Frontend/FrontendActions.h b/include/clang/Frontend/FrontendActions.h
index 26262cf..c172066 100644
--- a/include/clang/Frontend/FrontendActions.h
+++ b/include/clang/Frontend/FrontendActions.h
@@ -134,6 +134,16 @@
   virtual bool hasCodeCompletionSupport() const;
 };
 
+class PrintPreambleAction : public FrontendAction {
+protected:
+  void ExecuteAction();
+  virtual ASTConsumer *CreateASTConsumer(CompilerInstance &, llvm::StringRef) { 
+    return 0; 
+  }
+  
+  virtual bool usesPreprocessorOnly() const { return true; }
+};
+  
 //===----------------------------------------------------------------------===//
 // Preprocessor Actions
 //===----------------------------------------------------------------------===//
@@ -174,7 +184,7 @@
 
   virtual bool hasPCHSupport() const { return true; }
 };
-
+  
 }  // end namespace clang
 
 #endif
diff --git a/include/clang/Frontend/FrontendOptions.h b/include/clang/Frontend/FrontendOptions.h
index 4010ea6..263e571 100644
--- a/include/clang/Frontend/FrontendOptions.h
+++ b/include/clang/Frontend/FrontendOptions.h
@@ -44,6 +44,7 @@
     ParseSyntaxOnly,        ///< Parse and perform semantic analysis.
     PluginAction,           ///< Run a plugin action, \see ActionName.
     PrintDeclContext,       ///< Print DeclContext and their Decls.
+    PrintPreamble,          ///< Print the "preamble" of the input file
     PrintPreprocessedInput, ///< -E mode.
     RewriteMacros,          ///< Expand macros but not #includes.
     RewriteObjC,            ///< ObjC->C Rewriter.
diff --git a/include/clang/Lex/Lexer.h b/include/clang/Lex/Lexer.h
index 6a6e319..96d7605 100644
--- a/include/clang/Lex/Lexer.h
+++ b/include/clang/Lex/Lexer.h
@@ -219,6 +219,19 @@
                                      const SourceManager &SM,
                                      const LangOptions &LangOpts);
 
+  /// \brief Compute the preamble of the given file.
+  ///
+  /// The preamble of a file contains the initial comments, include directives,
+  /// and other preprocessor directives that occur before the code in this
+  /// particular file actually begins. The preamble of the main source file is
+  /// a potential prefix header.
+  ///
+  /// \param Buffer The memory buffer containing the file's contents.
+  ///
+  /// \returns The offset into the file where the preamble ends and the rest
+  /// of the file begins.
+  static unsigned ComputePreamble(const llvm::MemoryBuffer *Buffer);
+                                        
   //===--------------------------------------------------------------------===//
   // Internal implementation interfaces.
 private: