diff --git tools/clang/include/clang/Driver/CC1Options.td tools/clang/include/clang/Driver/CC1Options.td
index 83c988a..b278082 100644
--- tools/clang/include/clang/Driver/CC1Options.td
+++ tools/clang/include/clang/Driver/CC1Options.td
@@ -452,6 +452,8 @@ def rewrite_objc : Flag<"-rewrite-objc">,
   HelpText<"Rewrite ObjC into C (code rewriter example)">;
 def rewrite_macros : Flag<"-rewrite-macros">,
   HelpText<"Expand macros without full preprocessing">;
+def rewrite_includes : Flag<"-rewrite-includes">,
+  HelpText<"Expand includes without full preprocessing">;
 def migrate : Flag<"-migrate">,
   HelpText<"Migrate source code">;
 }
diff --git tools/clang/include/clang/Frontend/FrontendOptions.h tools/clang/include/clang/Frontend/FrontendOptions.h
index 888388c..78d3adf 100644
--- tools/clang/include/clang/Frontend/FrontendOptions.h
+++ tools/clang/include/clang/Frontend/FrontendOptions.h
@@ -43,6 +43,7 @@ namespace frontend {
     PrintPreamble,          ///< Print the "preamble" of the input file
     PrintPreprocessedInput, ///< -E mode.
     RewriteMacros,          ///< Expand macros but not #includes.
+    RewriteIncludes,        ///< Expand #includes but not macros.
     RewriteObjC,            ///< ObjC->C Rewriter.
     RewriteTest,            ///< Rewriter playground
     RunAnalysis,            ///< Run one or more source code analyses.
diff --git tools/clang/include/clang/Lex/Preprocessor.h tools/clang/include/clang/Lex/Preprocessor.h
index 055008f..638b4aa 100644
--- tools/clang/include/clang/Lex/Preprocessor.h
+++ tools/clang/include/clang/Lex/Preprocessor.h
@@ -121,6 +121,13 @@ class Preprocessor : public RefCountedBase<Preprocessor> {
   /// DisableMacroExpansion - True if macro expansion is disabled.
   bool DisableMacroExpansion : 1;
 
+  /// MacroExpansionInDirectivesOverride - Temporarily disables
+  /// DisableMacroExpansion (i.e. enables expansion) when parsing preprocessor
+  /// directives.
+  bool MacroExpansionInDirectivesOverride : 1;
+
+  class ResetMacroExpansionHelper;
+
   /// \brief Whether we have already loaded macros from the external source.
   mutable bool ReadMacrosFromExternalSource : 1;
 
@@ -634,6 +641,12 @@ public:
     while (Result.getKind() == tok::comment);
   }
 
+  /// Disables macro expansion everywhere except for preprocessor directives.
+  void SetMacroExpansionOnlyInDirectives() {
+    DisableMacroExpansion = true;
+    MacroExpansionInDirectivesOverride = true;
+  }
+
   /// LookAhead - This peeks ahead N tokens and returns that token without
   /// consuming any tokens.  LookAhead(0) returns the next token that would be
   /// returned by Lex(), LookAhead(1) returns the token after it, etc.  This
diff --git tools/clang/include/clang/Rewrite/FrontendActions.h tools/clang/include/clang/Rewrite/FrontendActions.h
index 6e9ecac..ea876d9 100644
--- tools/clang/include/clang/Rewrite/FrontendActions.h
+++ tools/clang/include/clang/Rewrite/FrontendActions.h
@@ -73,6 +73,11 @@ protected:
   void ExecuteAction();
 };
 
+class RewriteIncludesAction : public PreprocessorFrontendAction {
+protected:
+  void ExecuteAction();
+};
+
 }  // end namespace clang
 
 #endif
diff --git tools/clang/include/clang/Rewrite/Rewriters.h tools/clang/include/clang/Rewrite/Rewriters.h
index 203b9bc..9704fe3 100644
--- tools/clang/include/clang/Rewrite/Rewriters.h
+++ tools/clang/include/clang/Rewrite/Rewriters.h
@@ -18,6 +18,7 @@
 
 namespace clang {
 class Preprocessor;
+class PreprocessorOutputOptions;
 
 /// RewriteMacrosInInput - Implement -rewrite-macros mode.
 void RewriteMacrosInInput(Preprocessor &PP, raw_ostream *OS);
@@ -25,6 +26,9 @@ void RewriteMacrosInInput(Preprocessor &PP, raw_ostream *OS);
 /// DoRewriteTest - A simple test for the TokenRewriter class.
 void DoRewriteTest(Preprocessor &PP, raw_ostream *OS);
 
+/// RewriteIncludesInInput - Implement -rewrite-includes mode.
+void RewriteIncludesInInput(Preprocessor &PP, raw_ostream *OS, const PreprocessorOutputOptions &Opts);
+
 }  // end namespace clang
 
 #endif
diff --git tools/clang/lib/Frontend/CompilerInvocation.cpp tools/clang/lib/Frontend/CompilerInvocation.cpp
index 4c5b063..4e46973 100644
--- tools/clang/lib/Frontend/CompilerInvocation.cpp
+++ tools/clang/lib/Frontend/CompilerInvocation.cpp
@@ -430,6 +430,7 @@ static const char *getActionName(frontend::ActionKind Kind) {
   case frontend::PrintPreamble:          return "-print-preamble";
   case frontend::PrintPreprocessedInput: return "-E";
   case frontend::RewriteMacros:          return "-rewrite-macros";
+  case frontend::RewriteIncludes:        return "-rewrite-includes";
   case frontend::RewriteObjC:            return "-rewrite-objc";
   case frontend::RewriteTest:            return "-rewrite-test";
   case frontend::RunAnalysis:            return "-analyze";
@@ -1370,6 +1371,8 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
       Opts.ProgramAction = frontend::PrintPreprocessedInput; break;
     case OPT_rewrite_macros:
       Opts.ProgramAction = frontend::RewriteMacros; break;
+    case OPT_rewrite_includes:
+      Opts.ProgramAction = frontend::RewriteIncludes; break;
     case OPT_rewrite_objc:
       Opts.ProgramAction = frontend::RewriteObjC; break;
     case OPT_rewrite_test:
diff --git tools/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp tools/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
index 07d2b8d..49d0bb8 100644
--- tools/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
+++ tools/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
@@ -73,6 +73,7 @@ static FrontendAction *CreateFrontendBaseAction(CompilerInstance &CI) {
   case PrintPreamble:          return new PrintPreambleAction();
   case PrintPreprocessedInput: return new PrintPreprocessedAction();
   case RewriteMacros:          return new RewriteMacrosAction();
+  case RewriteIncludes:        return new RewriteIncludesAction();
   case RewriteObjC:            return new RewriteObjCAction();
   case RewriteTest:            return new RewriteTestAction();
   case RunAnalysis:            return new ento::AnalysisAction();
diff --git tools/clang/lib/Lex/Lexer.cpp tools/clang/lib/Lex/Lexer.cpp
index 535a852..aa424b4 100644
--- tools/clang/lib/Lex/Lexer.cpp
+++ tools/clang/lib/Lex/Lexer.cpp
@@ -2022,7 +2022,7 @@ bool Lexer::SaveBCPLComment(Token &Result, const char *CurPtr) {
   // directly.
   FormTokenWithChars(Result, CurPtr, tok::comment);
 
-  if (!ParsingPreprocessorDirective)
+  if (!ParsingPreprocessorDirective || LexingRawMode)
     return true;
 
   // If this BCPL-style comment is in a macro definition, transmogrify it into
@@ -2625,7 +2625,8 @@ LexNextToken:
       ParsingPreprocessorDirective = false;
 
       // Restore comment saving mode, in case it was disabled for directive.
-      SetCommentRetentionState(PP->getCommentRetentionState());
+      if (!LexingRawMode)
+        SetCommentRetentionState(PP->getCommentRetentionState());
 
       // Since we consumed a newline, we are back at the start of a line.
       IsAtStartOfLine = true;
diff --git tools/clang/lib/Lex/PPDirectives.cpp tools/clang/lib/Lex/PPDirectives.cpp
index 625a204..29a8614 100644
--- tools/clang/lib/Lex/PPDirectives.cpp
+++ tools/clang/lib/Lex/PPDirectives.cpp
@@ -553,6 +553,22 @@ const FileEntry *Preprocessor::LookupFile(
 // Preprocessor Directive Handling.
 //===----------------------------------------------------------------------===//
 
+class Preprocessor::ResetMacroExpansionHelper
+{
+public:
+  ResetMacroExpansionHelper(Preprocessor*pp)
+    : PP(pp), save(pp->DisableMacroExpansion) {
+    if (pp->MacroExpansionInDirectivesOverride)
+      pp->DisableMacroExpansion = false;
+  }
+  ~ResetMacroExpansionHelper() {
+    PP->DisableMacroExpansion = save;
+  }
+private:
+  Preprocessor* PP;
+  bool save;
+};
+
 /// HandleDirective - This callback is invoked when the lexer sees a # token
 /// at the start of a line.  This consumes the directive, modifies the
 /// lexer/preprocessor state, and advances the lexer(s) so that the next token
@@ -604,6 +620,10 @@ void Preprocessor::HandleDirective(Token &Result) {
     Diag(Result, diag::ext_embedded_directive);
   }
 
+  // temporarily enable macro expansion if set so
+  // and reset to previous state when returning from this function
+  ResetMacroExpansionHelper helper(this);
+
 TryAgain:
   switch (Result.getKind()) {
   case tok::eod:
diff --git tools/clang/lib/Lex/Preprocessor.cpp tools/clang/lib/Lex/Preprocessor.cpp
index 06e5685..f5d7a51 100644
--- tools/clang/lib/Lex/Preprocessor.cpp
+++ tools/clang/lib/Lex/Preprocessor.cpp
@@ -134,6 +134,7 @@ void Preprocessor::Initialize(const TargetInfo &Target) {
   
   // Macro expansion is enabled.
   DisableMacroExpansion = false;
+  MacroExpansionInDirectivesOverride = false;
   InMacroArgs = false;
   InMacroArgPreExpansion = false;
   NumCachedTokenLexers = 0;
diff --git tools/clang/lib/Rewrite/CMakeLists.txt tools/clang/lib/Rewrite/CMakeLists.txt
index 2a05040..8070ba2 100644
--- tools/clang/lib/Rewrite/CMakeLists.txt
+++ tools/clang/lib/Rewrite/CMakeLists.txt
@@ -6,6 +6,7 @@ add_clang_library(clangRewrite
   FrontendActions.cpp
   HTMLPrint.cpp
   HTMLRewrite.cpp
+  RewriteIncludes.cpp
   RewriteMacros.cpp
   RewriteModernObjC.cpp
   RewriteObjC.cpp
diff --git tools/clang/lib/Rewrite/FrontendActions.cpp tools/clang/lib/Rewrite/FrontendActions.cpp
index 1753325..e462671 100644
--- tools/clang/lib/Rewrite/FrontendActions.cpp
+++ tools/clang/lib/Rewrite/FrontendActions.cpp
@@ -181,3 +181,11 @@ void RewriteTestAction::ExecuteAction() {
 
   DoRewriteTest(CI.getPreprocessor(), OS);
 }
+
+void RewriteIncludesAction::ExecuteAction() {
+  CompilerInstance &CI = getCompilerInstance();
+  raw_ostream *OS = CI.createDefaultOutputFile(true, getCurrentFile());
+  if (!OS) return;
+
+  RewriteIncludesInInput(CI.getPreprocessor(), OS, CI.getPreprocessorOutputOpts());
+}
diff --git tools/clang/lib/Rewrite/RewriteIncludes.cpp tools/clang/lib/Rewrite/RewriteIncludes.cpp
new file mode 100644
index 0000000..54e09c5
--- /dev/null
+++ tools/clang/lib/Rewrite/RewriteIncludes.cpp
@@ -0,0 +1,542 @@
+//===--- RewriteIncludes.cpp - Rewrite includes into their expansions -----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This code rewrites include invocations into their expansions.  This gives you
+// a file with all included files merged into it.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Rewrite/Rewriters.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Frontend/PreprocessorOutputOptions.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace clang;
+using namespace llvm;
+
+namespace {
+
+/// Class representing the whole rewriting process and global data for it.
+class IncludeRewriter : public PPCallbacks, public CommentHandler {
+  /// Information about which #includes were actually performed,
+  /// created by preprocessor callbacks.
+  struct FileChange {
+    SourceLocation From;
+    FileID Id;
+    SrcMgr::CharacteristicKind Type;
+  };
+  Preprocessor &PP;
+  SourceManager &SM;
+  raw_ostream &OS;
+  bool DisableLineMarkers;
+  bool UseLineDirective;
+  typedef std::map<unsigned, FileChange> FileChangeMap;
+  FileChangeMap FileChanges;
+  unsigned LastInsertedFileChange;
+  /// From HandleComment() callback, two raw-encoded SourceLocation's,
+  /// will be sorted by the location.
+  typedef std::vector< std::pair<unsigned, unsigned> > CommentRangeVector;
+  CommentRangeVector CommentRanges;
+  bool KeepAllComments;
+  /// Keep comments in lines which are not only comments (such comments may be
+  /// visible in error/warning messages).
+  bool KeepCommentsInCodeLines;
+  class File;
+public:
+  IncludeRewriter(Preprocessor &PP, raw_ostream &OS,
+                  const PreprocessorOutputOptions &Opts);
+  void Process();
+  virtual void FileChanged(SourceLocation Loc, FileChangeReason Reason,
+                           SrcMgr::CharacteristicKind FileType,
+                           FileID PrevFID);
+  virtual void InclusionDirective(SourceLocation HashLoc,
+                                  const Token &IncludeTok,
+                                  StringRef FileName,
+                                  bool IsAngled,
+                                  const FileEntry *File,
+                                  SourceLocation EndLoc,
+                                  StringRef SearchPath,
+                                  StringRef RelativePath);
+  virtual bool HandleComment(Preprocessor &PP, SourceRange Comment);
+private:
+  const FileChange* FindFileChangeLocation(SourceLocation Loc) const;
+};
+
+/// Class representing the process of rewriting one source file.
+class IncludeRewriter::File {
+  IncludeRewriter* Rewriter;
+  Preprocessor &PP;
+  SourceManager &SM;
+  raw_ostream &OS;
+  FileID FileId;
+  SrcMgr::CharacteristicKind Type;
+  const MemoryBuffer *FromFile;
+  const char* FileName;
+  SourceLocation StartLocation;
+  bool Invalid;
+  const char* EOL;
+  OwningPtr<Lexer> RawLex;
+  // file position from which the content has not yet been copied to the output
+  unsigned NextToWrite;
+  // In case of KeepCommentsInCodeLines, this is actually the position from
+  // which the content has not yet been written, as in that mode the last line
+  // is output only if it's known there is some non-whitespace content in it. 
+  unsigned NextToWriteLine;
+  // the next CommentRange item that processed file contents contain (i.e.
+  // the current source location is >= NextToWrite's source location)
+  unsigned NextCommentRange;
+  int Line; // current input file line number
+public:
+  File(IncludeRewriter* Rewriter, FileID FileId,
+       SrcMgr::CharacteristicKind Type);
+  bool Process();
+private:
+  void WriteLineInfo(StringRef Extra = StringRef());
+  void OutputContentUpTo(unsigned WriteEnd, bool EnsureNewline = false);
+  void CommentOutDirective(const Token& StartToken);
+  void OutputContentStripComments(unsigned WriteEnd, bool RemoveAll);
+  StringRef NextIdentifierName(Token& RawToken);
+  void DetectEOL();
+  unsigned CountNewLines(const char* Pos, int Len);
+};
+
+}  // end anonymous namespace
+
+IncludeRewriter::IncludeRewriter(Preprocessor &pp, raw_ostream &os,
+                                 const PreprocessorOutputOptions &Opts)
+  : PP(pp)
+  , SM(PP.getSourceManager())
+  , OS(os)
+  , DisableLineMarkers(!Opts.ShowLineMarkers)
+  , LastInsertedFileChange(0)
+  , KeepAllComments(false)
+  , KeepCommentsInCodeLines(false) {
+  // If we're in microsoft mode, use normal #line instead of line markers.
+  UseLineDirective = PP.getLangOpts().MicrosoftExt;
+  // TODO: This is interpreting the -C and -CC options a bit differently than
+  // plain -E does, either document it or create new options.
+  if (Opts.ShowMacroComments)
+    KeepAllComments = true;
+  else if (Opts.ShowComments)
+    KeepCommentsInCodeLines = true;
+}
+
+/// FileChanged - Whenever the preprocessor enters or exits a #include file
+/// it invokes this handler.
+void IncludeRewriter::FileChanged(SourceLocation Loc,
+                                  FileChangeReason Reason,
+                                  SrcMgr::CharacteristicKind NewFileType,
+                                  FileID) {
+  if (Reason == EnterFile) {
+    // InclusionDirective() has already been called, add more info
+    FileID Id = FullSourceLoc(Loc,SM).getFileID();
+    if (LastInsertedFileChange != 0) { // there may be e.g. "<built-in>" first
+        FileChange& Ref = FileChanges[LastInsertedFileChange];
+        Ref.Id = Id;
+        Ref.Type = NewFileType;
+    }
+  }
+}
+
+/// This should be called whenever the preprocessor encounters include
+/// directives. It does not say whether the file has been included, but it
+/// provides more information about the directive (hash location istead
+/// of location inside the included file. It is assumed that the matching
+/// FileChanged() is called after this (if at all).
+void IncludeRewriter::InclusionDirective(SourceLocation HashLoc,
+                                         const Token &/*IncludeTok*/,
+                                         StringRef /*FileName*/,
+                                         bool /*IsAngled*/,
+                                         const FileEntry* /*File*/,
+                                         SourceLocation /*EndLoc*/,
+                                         StringRef /*SearchPath*/,
+                                         StringRef /*RelativePath*/) {
+  FileChange Change;
+  Change.From = HashLoc;
+  LastInsertedFileChange = HashLoc.getRawEncoding();
+  FileChanges[LastInsertedFileChange] = Change;
+}
+
+const IncludeRewriter::FileChange*
+IncludeRewriter::FindFileChangeLocation(SourceLocation Loc) const {
+  FileChangeMap ::const_iterator Find = FileChanges.find(Loc.getRawEncoding());
+  if(Find != FileChanges.end())
+    return &Find->second;
+  return NULL;
+}
+
+bool IncludeRewriter::HandleComment(Preprocessor &, SourceRange Comment) {
+  CommentRanges.push_back( std::make_pair(Comment.getBegin().getRawEncoding(),
+    Comment.getEnd().getRawEncoding()));
+  return false;
+}
+
+static bool CompareCommentRanges( const std::pair<unsigned, unsigned>& left,
+                                  const std::pair<unsigned, unsigned>& right ) {
+  return left.first < right.first;
+}
+
+void IncludeRewriter::Process() {
+// Sort comment ranges for easy finding of the next one from a given location.
+  std::sort(CommentRanges.begin(), CommentRanges.end(), CompareCommentRanges);
+  File MainFile(this, SM.getMainFileID(), SrcMgr::C_User);
+  MainFile.Process();
+}
+
+
+IncludeRewriter::File::File(IncludeRewriter* Rewriter,
+                            FileID FileId,
+                            SrcMgr::CharacteristicKind Type)
+  : Rewriter(Rewriter)
+  , PP(Rewriter->PP)
+  , SM(Rewriter->SM)
+  , OS(Rewriter->OS)
+  , FileId(FileId)
+  , Type(Type)
+  , Invalid(true)
+  , NextToWrite(0)
+  , NextToWriteLine(0)
+  , NextCommentRange(0)
+  , Line(1) {
+
+  StartLocation = SM.getLocForStartOfFile(FileId);
+  FileName = SM.getBufferName(StartLocation, &Invalid);
+  if (Invalid)
+    return;
+
+  // Use a raw lexer to analyze the input file, incrementally copying parts of
+  // it and including content of included files recursively.
+  FromFile = SM.getBuffer(FileId);
+  RawLex.reset( new Lexer(FileId, FromFile, PP.getSourceManager(), PP.getLangOpts()));
+  RawLex->SetCommentRetentionState(false);
+  DetectEOL();
+
+  WriteLineInfo(" 1");
+}
+
+bool IncludeRewriter::File::Process()
+{
+  if (Invalid)
+    return false;
+  if (SM.getFileIDSize(FileId) == 0)
+    return true;
+
+  Token RawToken;
+  RawLex->LexFromRawLexer(RawToken);
+
+  while (RawToken.isNot(tok::eof)) {
+    if (RawToken.is(tok::hash) && RawToken.isAtStartOfLine()) {
+      RawLex->setParsingPreprocessorDirective(true);
+      Token HashToken = RawToken;
+      RawLex->LexFromRawLexer(RawToken);
+      if (RawToken.is(tok::raw_identifier))
+        PP.LookUpIdentifierInfo(RawToken);
+      if (RawToken.is(tok::identifier)) {
+        switch (RawToken.getIdentifierInfo()->getPPKeywordID()) {
+          case tok::pp_include:
+          case tok::pp_include_next:
+          case tok::pp_import: {
+            // keep the directive in, commented out
+            // (clang sometimes optimizes and does not repeatedly include some
+            // files even though it should, so all includes need to be
+            // commented, otherwise valid directives would be left in)
+            CommentOutDirective(HashToken);
+            // fix up lineinfo, commenting out has added lines
+            bool NeedFixup = true;
+            if (const FileChange* Change = Rewriter->FindFileChangeLocation(
+                HashToken.getLocation())) {
+              // now include and recursively process the file
+              File IncludedFile(Rewriter, Change->Id, Change->Type);
+              if (IncludedFile.Process()) {
+                // and set lineinfo back to this file, if the nested one was
+                // actually included
+                WriteLineInfo(" 2");
+                NeedFixup = false;
+              }
+            }
+            if(NeedFixup)
+              WriteLineInfo();
+            break;
+          }
+          case tok::pp_pragma: {
+            StringRef Identifier = NextIdentifierName(RawToken);
+            if (Identifier == "clang" || Identifier == "GCC") {
+              if (NextIdentifierName(RawToken) == "system_header") {
+                // keep the directive in, commented out
+                CommentOutDirective(HashToken);
+                // update our own type
+                Type = SM.getFileCharacteristic(RawToken.getLocation());
+                WriteLineInfo();
+              }
+            } else if (Identifier == "once") {
+              // keep the directive in, commented out
+              CommentOutDirective(HashToken);
+              WriteLineInfo();
+            }
+            break;
+          }
+          default:
+            break;
+        }
+      }
+      RawLex->setParsingPreprocessorDirective(false);
+      RawLex->SetCommentRetentionState(false);
+    }
+  RawLex->LexFromRawLexer(RawToken);
+  }
+  OutputContentUpTo(SM.getFileIDSize(FileId), true);
+  return true;
+}
+
+void IncludeRewriter::File::DetectEOL() {
+  // detect what line endings the file uses, so that added content does not mix
+  // the style
+  const char* Pos = strchr(FromFile->getBufferStart(), '\n');
+  if (Pos == NULL)
+    EOL = "\n";
+  else if (Pos+1 < FromFile->getBufferEnd() && *(Pos+1) == '\r')
+    EOL = "\n\r";
+  else if (Pos-1 >= FromFile->getBufferStart() && *(Pos+1) == '\r')
+    EOL = "\r\n";
+  else 
+    EOL = "\n";
+}
+
+void IncludeRewriter::File::WriteLineInfo(StringRef Extra) {
+  if (Rewriter->DisableLineMarkers) {
+    OS << EOL; // Still need to at least separate lines.
+    return;
+  }
+  // Emit #line directives or GNU line markers depending on what mode we're in.
+  if (Rewriter->UseLineDirective) {
+    OS << "#line" << ' ' << Line << ' ' << '"' << FileName << '"';
+  } else {
+    OS << '#' << ' ' << Line << ' ' << '"' << FileName << '"';
+    if (!Extra.empty())
+      OS << Extra;
+    if (Type == SrcMgr::C_System)
+      OS << " 3";
+    else if (Type == SrcMgr::C_ExternCSystem)
+      OS << " 3 4";
+  }
+  OS << EOL;
+}
+
+inline unsigned IncludeRewriter::File::CountNewLines(const char* Pos, int Len) {
+  const char* End = Pos + Len;
+  unsigned Lines = 0;
+  --Pos;
+  while ((Pos = static_cast<const char*>(memchr(Pos + 1, '\n', End - Pos - 1))))
+    ++Lines;
+  return Lines;
+}
+
+// Used by OutputContentUpTo() to output content depending on comment
+// removing options (either all comments are removed if RemoveAll),
+// or only comments on lines that have other non-whitespace).
+void IncludeRewriter::File::OutputContentStripComments(unsigned WriteEnd,
+                                                       bool RemoveAll) {
+  unsigned LocalNextToWrite = NextToWrite;
+  // Only in !RemoveAll mode, true means there's something on the line
+  // besides whitespace and comments, so the comments should be kept.
+  bool LineKeepComment = false;
+  // Only in !RemoveAll mode, number of \n's in all comments
+  // from NextToWriteLine (in case they can be removed and just replaced
+  // with this number of \n's).
+  unsigned NewLinesInComments = 0;
+  for (;;) {
+    while (NextCommentRange < Rewriter->CommentRanges.size()
+           && Rewriter->CommentRanges[NextCommentRange].first
+             < LocalNextToWrite + StartLocation.getRawEncoding())
+      ++NextCommentRange;
+    // WriteEnd cannot be in the middle of a comment.
+    assert( !(NextCommentRange < Rewriter->CommentRanges.size()
+              && Rewriter->CommentRanges[NextCommentRange].first
+                 <= StartLocation.getRawEncoding() + WriteEnd - 1
+              && Rewriter->CommentRanges[NextCommentRange].second
+                 > StartLocation.getRawEncoding() + WriteEnd));
+    if (NextCommentRange >= Rewriter->CommentRanges.size()
+        || StartLocation.getRawEncoding() + WriteEnd - 1
+          < Rewriter->CommentRanges[NextCommentRange].first) {
+      // no further comment up to WriteEnd, write out all what we have
+      if (RemoveAll) {
+        OS.write(FromFile->getBufferStart() + LocalNextToWrite,
+          WriteEnd - LocalNextToWrite);
+      } else {
+        unsigned Pos = LocalNextToWrite;
+        unsigned ToWrite = WriteEnd - LocalNextToWrite;
+        for (unsigned int I = 0; I < ToWrite; ++I, ++Pos) {
+          char C = FromFile->getBufferStart()[Pos];
+          // TODO This is possibly wrong for EOL different from plain \n.
+          if (C == '\n') {
+            if (LineKeepComment)
+              OS.write(FromFile->getBufferStart() + NextToWriteLine,
+                Pos - NextToWriteLine + 1);
+            else {
+              for (unsigned I = 0; I < NewLinesInComments; ++I)
+                OS << EOL;
+              OS << EOL;
+            }
+            NextToWriteLine = Pos + 1;
+            LineKeepComment = false;
+            NewLinesInComments = 0;
+          }
+          if (!isspace(C))
+            LineKeepComment = true;
+        }
+        if (WriteEnd == SM.getFileIDSize(FileId)) {
+          // End of file, write out the rest if needed (there's no comment
+          // in it, so just write it out).
+          OS.write(FromFile->getBufferStart() + NextToWriteLine,
+            WriteEnd - NextToWriteLine);
+          NextToWriteLine = WriteEnd;
+        }
+      }
+      return;
+    }
+    const unsigned CommentStart = Rewriter->CommentRanges
+      [NextCommentRange].first - StartLocation.getRawEncoding();
+    const unsigned CommentEnd = Rewriter->CommentRanges
+      [NextCommentRange].second - StartLocation.getRawEncoding();//first after
+    // data up to the next comment
+    unsigned ToWrite = CommentStart - LocalNextToWrite;
+    if (RemoveAll) {
+      if (ToWrite > 0)
+        OS.write(FromFile->getBufferStart() + LocalNextToWrite, ToWrite);
+      // keep \n's and trailing \'s from the comment
+      unsigned Pos = CommentStart;
+      for (unsigned int I = 0; I < CommentEnd - CommentStart; ++I, ++Pos) {
+        char C = FromFile->getBufferStart()[Pos];
+        // TODO This is possibly wrong for EOL different from plain \n.
+        if (C == '\n') 
+          OS << EOL;
+        else if (C == '\\' && I + 1 < CommentEnd - CommentStart
+                    && FromFile->getBufferStart()[Pos + 1] == '\n') {
+          OS << '\\';
+        }
+      }
+    } else {
+      // Check if there's any \n, if yes, check if the line before it
+      // should be output (including comments) or whether it has only
+      // whitespace and comments, in which case output only \n for it.
+      unsigned Pos = LocalNextToWrite;
+      for (unsigned int I = 0; I < ToWrite; ++I, ++Pos) {
+        char C = FromFile->getBufferStart()[Pos];
+        // TODO This is possibly wrong for EOL different from plain \n.
+        if (C == '\n') {
+          if (LineKeepComment)
+            OS.write(FromFile->getBufferStart() + NextToWriteLine,
+              Pos - NextToWriteLine + 1);
+          else {
+            for (unsigned I = 0; I < NewLinesInComments; ++I)
+              OS << EOL;
+            OS << EOL;
+          }
+          NextToWriteLine = Pos + 1;
+          LineKeepComment = false;
+          NewLinesInComments = 0;
+        }
+        if (!isspace(C))
+          LineKeepComment = true;
+      }
+      // Process the comment - count the number of \n's in it, in case
+      // it can be removed.
+      // TODO Ideally, if there is a multiline comment, all lines inside
+      // the comment should be replaced with empty lines, to further reduce
+      // the size of the resulting output, even if the first and/or last
+      // line of the comment contain also other non-whitespace and should
+      // therefore be kept. Currently such a comment is kept as a whole.
+      // However in practice multiline comments, especially large ones
+      // (doxygen comments, file headers) usually can be removed as a whole,
+      // so this probably would not make a big difference.
+      for (unsigned int I = 0; I < CommentEnd - CommentStart; ++I, ++Pos) {
+        char C = FromFile->getBufferStart()[Pos];
+        if (C == '\n') {
+          ++NewLinesInComments;
+        } else if (C == '\\' && I + 1 < CommentEnd - CommentStart
+                    && FromFile->getBufferStart()[Pos + 1] == '\n') {
+          // Do not remove lines in multiline comments that end with \,
+          // as that could be a body of a macro.
+          // TODO This is possibly wrong with EOL different from plain \n.
+          LineKeepComment = true;
+        }
+      }
+    }
+    // and move after the comment
+    LocalNextToWrite = CommentEnd;
+  }  
+}
+
+/// Copies next not yet written file content up (and not including) to writeEnd.
+void IncludeRewriter::File::OutputContentUpTo(unsigned WriteEnd,
+                                              bool EnsureNewline) {
+  if (WriteEnd > NextToWrite) {
+    if (Rewriter->KeepAllComments)
+      OS.write(FromFile->getBufferStart() + NextToWrite, WriteEnd - NextToWrite);
+    else if (Rewriter->KeepCommentsInCodeLines)
+      OutputContentStripComments(WriteEnd, false);
+    else // Remove all comments.
+      OutputContentStripComments(WriteEnd, true);
+    // count lines manually, it's faster than getPresumedLoc()
+    Line += CountNewLines(FromFile->getBufferStart() + NextToWrite,
+      WriteEnd - NextToWrite);
+    if (EnsureNewline) {
+      char LastChar = FromFile->getBufferStart()[WriteEnd - 1];
+      if (LastChar != '\n' && LastChar != '\r')
+        OS << EOL;
+    }
+    NextToWrite = WriteEnd;
+  }
+}
+
+void IncludeRewriter::File::CommentOutDirective(const Token& StartToken) {
+  OutputContentUpTo(SM.getFileOffset(StartToken.getLocation()));
+  Token DirectiveToken;
+  do {
+    RawLex->LexFromRawLexer(DirectiveToken);
+  } while (!DirectiveToken.is(tok::eod) && DirectiveToken.isNot(tok::eof));
+  OS << "#if 0 /* expanded by -rewrite-includes */" << EOL;
+  OutputContentUpTo(SM.getFileOffset(DirectiveToken.getLocation())
+    + DirectiveToken.getLength());
+  OS << "#endif /* expanded by -rewrite-includes */" << EOL;
+}
+
+StringRef IncludeRewriter::File::NextIdentifierName(Token& RawToken) {
+  RawLex->LexFromRawLexer(RawToken);
+  if (RawToken.is(tok::raw_identifier))
+    PP.LookUpIdentifierInfo(RawToken);
+  if (RawToken.is(tok::identifier))
+    return RawToken.getIdentifierInfo()->getName();
+  return StringRef();
+}
+
+/// RewriteIncludesInInput - Implement -rewrite-includes mode.
+void clang::RewriteIncludesInInput(Preprocessor &PP, raw_ostream *OS,
+                                   const PreprocessorOutputOptions &Opts) {
+  IncludeRewriter* Rewrite = new IncludeRewriter(PP, *OS, Opts);
+  PP.addPPCallbacks(Rewrite);
+  PP.AddCommentHandler(Rewrite);
+
+  // First let the preprocessor process the entire file and call callbacks.
+  // Callbacks will record which #include's were actually performed.
+  PP.EnterMainSourceFile();
+  Token Tok;
+  // Only preprocessor directives matter here, so disable macro expansion
+  // everywhere else as an optimization.
+  // TODO: It would be even faster if the preprocessor could be switched
+  // to a mode where it would parse only preprocessor directives and comments,
+  // nothing else matters for parsing or processing.
+  PP.SetMacroExpansionOnlyInDirectives();
+  do {
+    PP.Lex(Tok);
+  } while (Tok.isNot(tok::eof));
+  Rewrite->Process();
+  OS->flush();
+}
diff --git tools/clang/make_patch tools/clang/make_patch
index d42af26..61a263d 100755
diff --git tools/clang/test/Frontend/Inputs/rewrite-includes1.h tools/clang/test/Frontend/Inputs/rewrite-includes1.h
new file mode 100644
index 0000000..1b6c80d
--- /dev/null
+++ tools/clang/test/Frontend/Inputs/rewrite-includes1.h
@@ -0,0 +1,3 @@
+#pragma clang system_header
+included_line1
+#include "rewrite-includes2.h"
diff --git tools/clang/test/Frontend/Inputs/rewrite-includes2.h tools/clang/test/Frontend/Inputs/rewrite-includes2.h
new file mode 100644
index 0000000..1114e51
--- /dev/null
+++ tools/clang/test/Frontend/Inputs/rewrite-includes2.h
@@ -0,0 +1 @@
+included_line2
diff --git tools/clang/test/Frontend/Inputs/rewrite-includes3.h tools/clang/test/Frontend/Inputs/rewrite-includes3.h
new file mode 100644
index 0000000..3757bc8
--- /dev/null
+++ tools/clang/test/Frontend/Inputs/rewrite-includes3.h
@@ -0,0 +1 @@
+included_line3
diff --git tools/clang/test/Frontend/Inputs/rewrite-includes4.h tools/clang/test/Frontend/Inputs/rewrite-includes4.h
new file mode 100644
index 0000000..b4e25d2
--- /dev/null
+++ tools/clang/test/Frontend/Inputs/rewrite-includes4.h
@@ -0,0 +1 @@
+included_line4
diff --git tools/clang/test/Frontend/Inputs/rewrite-includes5.h tools/clang/test/Frontend/Inputs/rewrite-includes5.h
new file mode 100644
index 0000000..934bf41
--- /dev/null
+++ tools/clang/test/Frontend/Inputs/rewrite-includes5.h
@@ -0,0 +1 @@
+included_line5
diff --git tools/clang/test/Frontend/Inputs/rewrite-includes6.h tools/clang/test/Frontend/Inputs/rewrite-includes6.h
new file mode 100644
index 0000000..c18e501
--- /dev/null
+++ tools/clang/test/Frontend/Inputs/rewrite-includes6.h
@@ -0,0 +1,2 @@
+#pragma once
+included_line6
diff --git tools/clang/test/Frontend/Inputs/rewrite-includes7.h tools/clang/test/Frontend/Inputs/rewrite-includes7.h
new file mode 100644
index 0000000..85428fd
--- /dev/null
+++ tools/clang/test/Frontend/Inputs/rewrite-includes7.h
@@ -0,0 +1,4 @@
+#ifndef REWRITE_INCLUDES7_H
+#define REWRITE_INCLUDES7_H
+included_line7
+#endif
diff --git tools/clang/test/Frontend/Inputs/rewrite-includes8.h tools/clang/test/Frontend/Inputs/rewrite-includes8.h
new file mode 100644
index 0000000..7ab5fd9
--- /dev/null
+++ tools/clang/test/Frontend/Inputs/rewrite-includes8.h
@@ -0,0 +1 @@
+included_line8
\ No newline at end of file
diff --git tools/clang/test/Frontend/Inputs/rewrite-includes9.h tools/clang/test/Frontend/Inputs/rewrite-includes9.h
new file mode 100644
index 0000000..e69de29
diff --git tools/clang/test/Frontend/rewrite-includes.c tools/clang/test/Frontend/rewrite-includes.c
new file mode 100644
index 0000000..52be495
--- /dev/null
+++ tools/clang/test/Frontend/rewrite-includes.c
@@ -0,0 +1,46 @@
+// RUN: %clang_cc1 -verify -rewrite-includes -DFIRST -I %S/Inputs %s -CC -o - | FileCheck -check-prefix=CHECK-C2 -strict-whitespace %s.check
+// RUN: %clang_cc1 -verify -rewrite-includes -DFIRST -I %S/Inputs %s -C -o - | FileCheck -check-prefix=CHECK-C1 -strict-whitespace %s.check
+// RUN: %clang_cc1 -verify -rewrite-includes -DFIRST -I %S/Inputs %s -o - | FileCheck -check-prefix=CHECK-C0 -strict-whitespace %s.check
+
+STARTCOMPARE
+#define A(a,b) a ## b
+A(1,2)
+#include "rewrite-includes1.h"
+#ifdef FIRST
+#define HEADER "rewrite-includes3.h"
+#include HEADER
+#else
+#include "rewrite-includes4.h"
+#endif
+#/**/include /**/ "rewrite-includes5.h" /**/ \
+ 
+#include "rewrite-includes6.h" // comment
+ 
+ // comment
+ /*
+ multiline
+ comment
+ */
+#define MACRO \
+ /*comment*/ \
+ /*multi \
+   line*/ \
+ 
+MACRO
+/*
+\
+comment
+*/
+foo /* multiline
+with code
+prepended */
+/* multiline
+with code
+appended */ bar
+#include "rewrite-includes6.h" /* comment
+                                  continues */
+#include "rewrite-includes7.h"
+#include "rewrite-includes7.h"
+#include "rewrite-includes8.h" // no trailing \n in file
+#include "rewrite-includes9.h" // empty file
+ENDCOMPARE
diff --git tools/clang/test/Frontend/rewrite-includes.c.check tools/clang/test/Frontend/rewrite-includes.c.check
new file mode 100644
index 0000000..7e920a5
--- /dev/null
+++ tools/clang/test/Frontend/rewrite-includes.c.check
@@ -0,0 +1,308 @@
+Modes that remove comments would also remove these check lines, so keep them in a separate file.
+
+Note that FileCheck does not seem to have a way to check for an empty line,
+so there is just a comment, the next non-empty line is not -NEXT but a plain check line
+and the line correctness is checked by same later # directive check.
+
+This one checks -CC, i.e. all comments are kept. It's the primary mode for the test.
+
+// CHECK-C2: {{^}}STARTCOMPARE{{$}}
+// CHECK-C2-NEXT: {{^}}#define A(a,b) a ## b{{$}}
+// CHECK-C2-NEXT: {{^}}A(1,2){{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#include "rewrite-includes1.h"{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes1.h" 1{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#pragma clang system_header{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 2 "{{.*}}/Inputs/rewrite-includes1.h" 3{{$}}
+// CHECK-C2-NEXT: {{^}}included_line1{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#include "rewrite-includes2.h"{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes2.h" 1 3{{$}}
+// CHECK-C2-NEXT: {{^}}included_line2{{$}}
+// CHECK-C2-NEXT: {{^}}# 4 "{{.*}}/Inputs/rewrite-includes1.h" 2 3{{$}}
+// CHECK-C2-NEXT: {{^}}# 9 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C2-NEXT: {{^}}#ifdef FIRST{{$}}
+// CHECK-C2-NEXT: {{^}}#define HEADER "rewrite-includes3.h"{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#include HEADER{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes3.h" 1{{$}}
+// CHECK-C2-NEXT: {{^}}included_line3{{$}}
+// CHECK-C2-NEXT: {{^}}# 12 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C2-NEXT: {{^}}#else{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#include "rewrite-includes4.h"{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 14 "{{.*}}rewrite-includes.c"{{$}}
+// CHECK-C2-NEXT: {{^}}#endif{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#/**/include /**/ "rewrite-includes5.h" /**/ {{\\}}{{$}}
+// CHECK-C2-NEXT: {{^}} {{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes5.h" 1{{$}}
+// CHECK-C2-NEXT: {{^}}included_line5{{$}}
+// CHECK-C2-NEXT: {{^}}# 17 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#include "rewrite-includes6.h" // comment{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes6.h" 1{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#pragma once{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 2 "{{.*}}/Inputs/rewrite-includes6.h"{{$}}
+// CHECK-C2-NEXT: {{^}}included_line6{{$}}
+// CHECK-C2-NEXT: {{^}}# 18 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C2-NEXT: {{^}} {{$}}
+// CHECK-C2-NEXT: {{^}} // comment{{$}}
+// CHECK-C2-NEXT: {{^}} /*{{$}}
+// CHECK-C2-NEXT: {{^}} multiline{{$}}
+// CHECK-C2-NEXT: {{^}} comment{{$}}
+// CHECK-C2-NEXT: {{^}} */{{$}}
+// CHECK-C2-NEXT: {{^}}#define MACRO \{{$}}
+// CHECK-C2-NEXT: {{^}} /*comment*/ \{{$}}
+// CHECK-C2-NEXT: {{^}} /*multi \{{$}}
+// CHECK-C2-NEXT: {{^}}   line*/ \{{$}}
+// CHECK-C2-NEXT: {{^}} {{$}}
+// CHECK-C2-NEXT: {{^}}MACRO{{$}}
+// CHECK-C2-NEXT: {{^}}/*{{$}}
+// CHECK-C2-NEXT: {{^}}\{{$}}
+// CHECK-C2-NEXT: {{^}}comment{{$}}
+// CHECK-C2-NEXT: {{^}}*/{{$}}
+// CHECK-C2-NEXT: {{^}}foo /* multiline{{$}}
+// CHECK-C2-NEXT: {{^}}with code{{$}}
+// CHECK-C2-NEXT: {{^}}prepended */{{$}}
+// CHECK-C2-NEXT: {{^}}/* multiline{{$}}
+// CHECK-C2-NEXT: {{^}}with code{{$}}
+// CHECK-C2-NEXT: {{^}}appended */ bar{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#include "rewrite-includes6.h" /* comment{{$}}
+// CHECK-C2-NEXT: {{^}}                                  continues */{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 42 "{{.*}}rewrite-includes.c"{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#include "rewrite-includes7.h"{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes7.h" 1{{$}}
+// CHECK-C2-NEXT: {{^}}#ifndef REWRITE_INCLUDES7_H{{$}}
+// CHECK-C2-NEXT: {{^}}#define REWRITE_INCLUDES7_H{{$}}
+// CHECK-C2-NEXT: {{^}}included_line7{{$}}
+// CHECK-C2-NEXT: {{^}}#endif{{$}}
+// CHECK-C2-NEXT: {{^}}# 43 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#include "rewrite-includes7.h"{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 44 "{{.*}}rewrite-includes.c"{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#include "rewrite-includes8.h" // no trailing \n in file{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes8.h" 1{{$}}
+// CHECK-C2-NEXT: {{^}}included_line8{{$}}
+// CHECK-C2-NEXT: {{^}}# 45 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C2-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}#include "rewrite-includes9.h" // empty file{{$}}
+// CHECK-C2-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C2-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes9.h" 1{{$}}
+// CHECK-C2-NEXT: {{^}}# 46 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C2-NEXT: {{^}}ENDCOMPARE{{$}}
+
+This one checks -C, i.e. only comments on lines with other non-whitespace are kept.
+Note that lines containing only whitespace are not preserved exactly and are converted to empty lines.
+
+// CHECK-C1: {{^}}STARTCOMPARE{{$}}
+// CHECK-C1-NEXT: {{^}}#define A(a,b) a ## b{{$}}
+// CHECK-C1-NEXT: {{^}}A(1,2){{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#include "rewrite-includes1.h"{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes1.h" 1{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#pragma clang system_header{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 2 "{{.*}}/Inputs/rewrite-includes1.h" 3{{$}}
+// CHECK-C1-NEXT: {{^}}included_line1{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#include "rewrite-includes2.h"{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes2.h" 1 3{{$}}
+// CHECK-C1-NEXT: {{^}}included_line2{{$}}
+// CHECK-C1-NEXT: {{^}}# 4 "{{.*}}/Inputs/rewrite-includes1.h" 2 3{{$}}
+// CHECK-C1-NEXT: {{^}}# 9 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C1-NEXT: {{^}}#ifdef FIRST{{$}}
+// CHECK-C1-NEXT: {{^}}#define HEADER "rewrite-includes3.h"{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#include HEADER{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes3.h" 1{{$}}
+// CHECK-C1-NEXT: {{^}}included_line3{{$}}
+// CHECK-C1-NEXT: {{^}}# 12 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C1-NEXT: {{^}}#else{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#include "rewrite-includes4.h"{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 14 "{{.*}}rewrite-includes.c"{{$}}
+// CHECK-C1-NEXT: {{^}}#endif{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#/**/include /**/ "rewrite-includes5.h" /**/ {{\\}}{{$}}
+// here's an empty line
+// CHECK-C1: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes5.h" 1{{$}}
+// CHECK-C1-NEXT: {{^}}included_line5{{$}}
+// CHECK-C1-NEXT: {{^}}# 17 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#include "rewrite-includes6.h" // comment{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes6.h" 1{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#pragma once{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 2 "{{.*}}/Inputs/rewrite-includes6.h"{{$}}
+// CHECK-C1-NEXT: {{^}}included_line6{{$}}
+// CHECK-C1-NEXT: {{^}}# 18 "{{.*}}rewrite-includes.c" 2{{$}}
+// here are 6 empty lines
+// CHECK-C1: {{^}}#define MACRO \{{$}}
+// CHECK-C1-NEXT: {{^}} /*comment*/ \{{$}}
+// CHECK-C1-NEXT: {{^}} /*multi \{{$}}
+// CHECK-C1-NEXT: {{^}}   line*/ \{{$}}
+// here's an empty line
+// CHECK-C1: {{^}}MACRO{{$}}
+// CHECK-C1-NEXT: {{^}}/*{{$}}
+// CHECK-C1-NEXT: {{^}}\{{$}}
+// CHECK-C1-NEXT: {{^}}comment{{$}}
+// CHECK-C1-NEXT: {{^}}*/{{$}}
+// CHECK-C1-NEXT: {{^}}foo /* multiline{{$}}
+// CHECK-C1-NEXT: {{^}}with code{{$}}
+// CHECK-C1-NEXT: {{^}}prepended */{{$}}
+// CHECK-C1-NEXT: {{^}}/* multiline{{$}}
+// CHECK-C1-NEXT: {{^}}with code{{$}}
+// CHECK-C1-NEXT: {{^}}appended */ bar{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#include "rewrite-includes6.h" /* comment{{$}}
+// CHECK-C1-NEXT: {{^}}                                  continues */{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 42 "{{.*}}rewrite-includes.c"{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#include "rewrite-includes7.h"{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes7.h" 1{{$}}
+// CHECK-C1-NEXT: {{^}}#ifndef REWRITE_INCLUDES7_H{{$}}
+// CHECK-C1-NEXT: {{^}}#define REWRITE_INCLUDES7_H{{$}}
+// CHECK-C1-NEXT: {{^}}included_line7{{$}}
+// CHECK-C1-NEXT: {{^}}#endif{{$}}
+// CHECK-C1-NEXT: {{^}}# 43 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#include "rewrite-includes7.h"{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 44 "{{.*}}rewrite-includes.c"{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#include "rewrite-includes8.h" // no trailing \n in file{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes8.h" 1{{$}}
+// CHECK-C1-NEXT: {{^}}included_line8{{$}}
+// CHECK-C1-NEXT: {{^}}# 45 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C1-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}#include "rewrite-includes9.h" // empty file{{$}}
+// CHECK-C1-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C1-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes9.h" 1{{$}}
+// CHECK-C1-NEXT: {{^}}# 46 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C1-NEXT: {{^}}ENDCOMPARE{{$}}
+
+This one checks without -C or -CC, i.e. comments removed.
+
+// CHECK-C0: {{^}}STARTCOMPARE{{$}}
+// CHECK-C0-NEXT: {{^}}#define A(a,b) a ## b{{$}}
+// CHECK-C0-NEXT: {{^}}A(1,2){{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#include "rewrite-includes1.h"{{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes1.h" 1{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#pragma clang system_header{{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 2 "{{.*}}/Inputs/rewrite-includes1.h" 3{{$}}
+// CHECK-C0-NEXT: {{^}}included_line1{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#include "rewrite-includes2.h"{{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes2.h" 1 3{{$}}
+// CHECK-C0-NEXT: {{^}}included_line2{{$}}
+// CHECK-C0-NEXT: {{^}}# 4 "{{.*}}/Inputs/rewrite-includes1.h" 2 3{{$}}
+// CHECK-C0-NEXT: {{^}}# 9 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C0-NEXT: {{^}}#ifdef FIRST{{$}}
+// CHECK-C0-NEXT: {{^}}#define HEADER "rewrite-includes3.h"{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#include HEADER{{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes3.h" 1{{$}}
+// CHECK-C0-NEXT: {{^}}included_line3{{$}}
+// CHECK-C0-NEXT: {{^}}# 12 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C0-NEXT: {{^}}#else{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#include "rewrite-includes4.h"{{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 14 "{{.*}}rewrite-includes.c"{{$}}
+// CHECK-C0-NEXT: {{^}}#endif{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#include  "rewrite-includes5.h"  {{\\}}{{$}}
+// CHECK-C0-NEXT: {{^}} {{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes5.h" 1{{$}}
+// CHECK-C0-NEXT: {{^}}included_line5{{$}}
+// CHECK-C0-NEXT: {{^}}# 17 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#include "rewrite-includes6.h" {{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes6.h" 1{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#pragma once{{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 2 "{{.*}}/Inputs/rewrite-includes6.h"{{$}}
+// CHECK-C0-NEXT: {{^}}included_line6{{$}}
+// CHECK-C0-NEXT: {{^}}# 18 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C0-NEXT: {{^}} {{$}}
+// here are 5 empty lines
+// CHECK-C0: {{^}}#define MACRO \{{$}}
+// CHECK-C0-NEXT: {{^}}  \{{$}}
+// CHECK-C0-NEXT: {{^}} \{{$}}
+// CHECK-C0-NEXT: {{^}} \{{$}}
+// here's an empty line
+// CHECK-C0: {{^}}MACRO{{$}}
+// here's an empty line
+// CHECK-C0: {{^}}\{{$}}
+// here are 2 empty lines
+// CHECK-C0: {{^}}foo {{$}}
+// here are 4 empty lines
+// CHECK-C0: {{^}} bar{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#include "rewrite-includes6.h" {{$}}
+// here's an empty line
+// CHECK-C0: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 42 "{{.*}}rewrite-includes.c"{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#include "rewrite-includes7.h"{{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes7.h" 1{{$}}
+// CHECK-C0-NEXT: {{^}}#ifndef REWRITE_INCLUDES7_H{{$}}
+// CHECK-C0-NEXT: {{^}}#define REWRITE_INCLUDES7_H{{$}}
+// CHECK-C0-NEXT: {{^}}included_line7{{$}}
+// CHECK-C0-NEXT: {{^}}#endif{{$}}
+// CHECK-C0-NEXT: {{^}}# 43 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#include "rewrite-includes7.h"{{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 44 "{{.*}}rewrite-includes.c"{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#include "rewrite-includes8.h" {{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes8.h" 1{{$}}
+// CHECK-C0-NEXT: {{^}}included_line8{{$}}
+// CHECK-C0-NEXT: {{^}}# 45 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C0-NEXT: {{^}}#if 0 /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}#include "rewrite-includes9.h" {{$}}
+// CHECK-C0-NEXT: {{^}}#endif /* expanded by -rewrite-includes */{{$}}
+// CHECK-C0-NEXT: {{^}}# 1 "{{.*}}/Inputs/rewrite-includes9.h" 1{{$}}
+// CHECK-C0-NEXT: {{^}}# 46 "{{.*}}rewrite-includes.c" 2{{$}}
+// CHECK-C0-NEXT: {{^}}ENDCOMPARE{{$}}