diff --git a/clang/include/clang/Basic/SourceLocation.h b/clang/include/clang/Basic/SourceLocation.h
index 227313b7bfdf..4c0f0e9d462e 100644
--- a/clang/include/clang/Basic/SourceLocation.h
+++ b/clang/include/clang/Basic/SourceLocation.h
@@ -68,10 +68,10 @@ public:
   enum {
     // FileID Layout:
     // bit 31: 0 -> FileID, 1 -> MacroID (invalid for FileID)
-    //     30...17 -> FileID of source location, index into SourceManager table.
-    FileIDBits  = 14,
-    //      0...16 -> Index into the chunk of the specified FileID.
-    FilePosBits = 32-1-FileIDBits,
+    //     30...17 -> ChunkID of location, index into SourceManager table.
+    ChunkIDBits  = 14,
+    //      0...16 -> Index into the chunk of the specified ChunkID.
+    FilePosBits = 32-1-ChunkIDBits,
     
     // MacroID Layout:
     // bit 31: 1 -> MacroID, 0 -> FileID (invalid for MacroID)
@@ -100,20 +100,20 @@ public:
   bool isValid() const { return ID != 0; }
   bool isInvalid() const { return ID == 0; }
   
-  static SourceLocation getFileLoc(unsigned FileID, unsigned FilePos) {
+  static SourceLocation getFileLoc(unsigned ChunkID, unsigned FilePos) {
     SourceLocation L;
     // If a FilePos is larger than (1<<FilePosBits), the SourceManager makes
-    // enough consequtive FileIDs that we have one for each chunk.
+    // enough consequtive ChunkIDs that we have one for each chunk.
     if (FilePos >= ChunkSize) {
-      FileID += FilePos >> FilePosBits;
+      ChunkID += FilePos >> FilePosBits;
       FilePos &= ChunkSize-1;
     }
     
-    // FIXME: Find a way to handle out of FileID bits!  Maybe MaxFileID is an
+    // FIXME: Find a way to handle out of ChunkID bits!  Maybe MaxFileID is an
     // escape of some sort?
-    assert(FileID < (1 << FileIDBits) && "Out of fileid's");
+    assert(ChunkID < (1 << ChunkIDBits) && "Out of ChunkID's");
     
-    L.ID = (FileID << FilePosBits) | FilePos;
+    L.ID = (ChunkID << FilePosBits) | FilePos;
     return L;
   }
   
@@ -138,16 +138,16 @@ public:
   }
   
   
-  /// getFileID - Return the file identifier for this SourceLocation.  This
-  /// FileID can be used with the SourceManager object to obtain an entire
+  /// getChunkID - Return the chunk identifier for this SourceLocation.  This
+  /// ChunkID can be used with the SourceManager object to obtain an entire
   /// include stack for a file position reference.
-  unsigned getFileID() const {
+  unsigned getChunkID() const {
     assert(isFileID() && "can't get the file id of a non-file sloc!");
     return ID >> FilePosBits;
   }
   
   /// getRawFilePos - Return the byte offset from the start of the file-chunk
-  /// referred to by FileID.  This method should not be used to get the offset
+  /// referred to by ChunkID.  This method should not be used to get the offset
   /// from the start of the file, instead you should use
   /// SourceManager::getDecomposedFileLoc.  This method will be 
   //  incorrect for large files.
@@ -172,14 +172,14 @@ public:
   /// getFileLocWithOffset - Return a source location with the specified offset
   /// from this file SourceLocation.
   SourceLocation getFileLocWithOffset(int Offset) const {
-    unsigned FileID = getFileID();
+    unsigned ChunkID = getChunkID();
     Offset += getRawFilePos();
     // Handle negative offsets correctly.
     while (Offset < 0) {
-      --FileID;
+      --ChunkID;
       Offset += ChunkSize;
     }
-    return getFileLoc(FileID, Offset);
+    return getFileLoc(ChunkID, Offset);
   }
   
   /// getRawEncoding - When a SourceLocation itself cannot be used, this returns
@@ -261,6 +261,8 @@ public:
     return *SrcMgr;
   }
   
+  FileID getFileID() const;
+  
   FullSourceLoc getInstantiationLoc() const;
   FullSourceLoc getSpellingLoc() const;
   FullSourceLoc getIncludeLoc() const;
diff --git a/clang/include/clang/Basic/SourceManager.h b/clang/include/clang/Basic/SourceManager.h
index 4f46bad8db15..08929e39c1e5 100644
--- a/clang/include/clang/Basic/SourceManager.h
+++ b/clang/include/clang/Basic/SourceManager.h
@@ -350,7 +350,7 @@ public:
   /// SourceLocation.  If this is a macro expansion, this transparently figures
   /// out which file includes the file being expanded into.
   SourceLocation getIncludeLoc(SourceLocation ID) const {
-    return getFIDInfo(getInstantiationLoc(ID).getFileID())->getIncludeLoc();
+    return getFIDInfo(getInstantiationLoc(ID).getChunkID())->getIncludeLoc();
   }
   
   /// getCharacterData - Return a pointer to the start of the specified location
@@ -415,9 +415,9 @@ public:
   /// the specified SourceLocation, if one exists.
   const SrcMgr::ContentCache* getContentCacheForLoc(SourceLocation Loc) const {
     Loc = getSpellingLoc(Loc);
-    unsigned FileID = Loc.getFileID();
-    assert(FileID-1 < FileIDs.size() && "Invalid FileID!");
-    return FileIDs[FileID-1].getContentCache();
+    unsigned ChunkID = Loc.getChunkID();
+    assert(ChunkID-1 < FileIDs.size() && "Invalid FileID!");
+    return FileIDs[ChunkID-1].getContentCache();
   }
   
   /// getFileEntryForLoc - Return the FileEntry record for the spelling loc of
@@ -447,7 +447,7 @@ public:
     assert(Loc.isFileID() && "Isn't a File SourceLocation");
     
     // TODO: Add a flag "is first chunk" to SLOC.
-    const SrcMgr::FileIDInfo *FIDInfo = getFIDInfo(Loc.getFileID());
+    const SrcMgr::FileIDInfo *FIDInfo = getFIDInfo(Loc.getChunkID());
       
     // If this file has been split up into chunks, factor in the chunk number
     // that the FileID references.
@@ -455,9 +455,9 @@ public:
     unsigned Offset = Loc.getRawFilePos();
     Offset += (ChunkNo << SourceLocation::FilePosBits);
 
-    assert(Loc.getFileID() >= ChunkNo && "Unexpected offset");
+    assert(Loc.getChunkID() >= ChunkNo && "Unexpected offset");
     
-    return std::make_pair(FileID::Create(Loc.getFileID()-ChunkNo), Offset);
+    return std::make_pair(FileID::Create(Loc.getChunkID()-ChunkNo), Offset);
   }
     
   /// getFullFilePos - This (efficient) method returns the offset from the start
@@ -485,7 +485,8 @@ public:
     return getFileCharacteristic(Loc) != SrcMgr::C_User;
   }
   SrcMgr::CharacteristicKind getFileCharacteristic(SourceLocation Loc) const {
-    return getFIDInfo(getSpellingLoc(Loc).getFileID())->getFileCharacteristic();
+    return getFIDInfo(getSpellingLoc(Loc).getChunkID())
+                  ->getFileCharacteristic();
   }
   SrcMgr::CharacteristicKind getFileCharacteristic(FileID FID) const {
     return getFIDInfo(FID)->getFileCharacteristic();
diff --git a/clang/include/clang/Driver/TextDiagnosticPrinter.h b/clang/include/clang/Driver/TextDiagnosticPrinter.h
index e6d570c5e3b7..550c337b50b1 100644
--- a/clang/include/clang/Driver/TextDiagnosticPrinter.h
+++ b/clang/include/clang/Driver/TextDiagnosticPrinter.h
@@ -40,7 +40,7 @@ public:
 
   void HighlightRange(const SourceRange &R,
                       const SourceManager& SrcMgr,
-                      unsigned LineNo, unsigned FileID,
+                      unsigned LineNo, FileID FID,
                       std::string &CaretLine,
                       const std::string &SourceLine);
 
diff --git a/clang/lib/Basic/SourceLocation.cpp b/clang/lib/Basic/SourceLocation.cpp
index 84fac86a6df7..dcfd547eec4b 100644
--- a/clang/lib/Basic/SourceLocation.cpp
+++ b/clang/lib/Basic/SourceLocation.cpp
@@ -37,6 +37,12 @@ SourceRange SourceRange::ReadVal(llvm::Deserializer& D) {
   return SourceRange(A,B);
 }
 
+FileID FullSourceLoc::getFileID() const {
+  assert(isValid());
+  return SrcMgr->getCanonicalFileID(*this);
+}
+
+
 FullSourceLoc FullSourceLoc::getInstantiationLoc() const {
   assert(isValid());
   return FullSourceLoc(SrcMgr->getInstantiationLoc(*this), *SrcMgr);
diff --git a/clang/lib/Basic/SourceManager.cpp b/clang/lib/Basic/SourceManager.cpp
index b6c4ffab4db0..f793c978ccbb 100644
--- a/clang/lib/Basic/SourceManager.cpp
+++ b/clang/lib/Basic/SourceManager.cpp
@@ -121,7 +121,7 @@ FileID SourceManager::createFileID(const ContentCache *File,
   unsigned FileSize = File->getSize();
   if (FileSize+1 < (1 << SourceLocation::FilePosBits)) {
     FileIDs.push_back(FileIDInfo::get(IncludePos, 0, File, FileCharacter));
-    assert(FileIDs.size() < (1 << SourceLocation::FileIDBits) &&
+    assert(FileIDs.size() < (1 << SourceLocation::ChunkIDBits) &&
            "Ran out of file ID's!");
     return FileID::Create(FileIDs.size());
   }
@@ -138,7 +138,7 @@ FileID SourceManager::createFileID(const ContentCache *File,
     FileSize -= (1 << SourceLocation::FilePosBits);
   }
 
-  assert(FileIDs.size() < (1 << SourceLocation::FileIDBits) &&
+  assert(FileIDs.size() < (1 << SourceLocation::ChunkIDBits) &&
          "Ran out of file ID's!");
   return FileID::Create(Result);
 }
@@ -165,7 +165,7 @@ SourceLocation SourceManager::getInstantiationLoc(SourceLocation SpellingLoc,
     // The instanitation point and source SpellingLoc have to exactly match to
     // reuse (for now).  We could allow "nearby" instantiations in the future.
     if (LastOne.getInstantiationLoc() != InstantLoc ||
-        LastOne.getSpellingLoc().getFileID() != SpellingLoc.getFileID())
+        LastOne.getSpellingLoc().getChunkID() != SpellingLoc.getChunkID())
       continue;
   
     // Check to see if the spellloc of the token came from near enough to reuse.
@@ -215,7 +215,7 @@ const char *SourceManager::getCharacterData(SourceLocation SL) const {
 /// this is significantly cheaper to compute than the line number.  This returns
 /// zero if the column number isn't known.
 unsigned SourceManager::getColumnNumber(SourceLocation Loc) const {
-  if (Loc.getFileID() == 0) return 0;
+  if (Loc.getChunkID() == 0) return 0;
   
   std::pair<FileID, unsigned> LocInfo = getDecomposedFileLoc(Loc);
   unsigned FilePos = LocInfo.second;
@@ -232,7 +232,7 @@ unsigned SourceManager::getColumnNumber(SourceLocation Loc) const {
 /// the SourceLocation specifies.  This can be modified with #line directives,
 /// etc.
 const char *SourceManager::getSourceName(SourceLocation Loc) const {
-  if (Loc.getFileID() == 0) return "";
+  if (Loc.getChunkID() == 0) return "";
   
   // To get the source name, first consult the FileEntry (if one exists) before
   // the MemBuffer as this will avoid unnecessarily paging in the MemBuffer.
@@ -290,7 +290,7 @@ static void ComputeLineNumbers(ContentCache* FI) {
 /// line offsets for the MemoryBuffer, so this is not cheap: use only when
 /// about to emit a diagnostic.
 unsigned SourceManager::getLineNumber(SourceLocation Loc) const {
-  if (Loc.getFileID() == 0) return 0;
+  if (Loc.getChunkID() == 0) return 0;
 
   ContentCache *Content;
   
diff --git a/clang/lib/Driver/TextDiagnosticPrinter.cpp b/clang/lib/Driver/TextDiagnosticPrinter.cpp
index 8523723278f1..4080b748ad5a 100644
--- a/clang/lib/Driver/TextDiagnosticPrinter.cpp
+++ b/clang/lib/Driver/TextDiagnosticPrinter.cpp
@@ -36,8 +36,8 @@ PrintIncludeStack(FullSourceLoc Pos) {
 /// HighlightRange - Given a SourceRange and a line number, highlight (with ~'s)
 /// any characters in LineNo that intersect the SourceRange.
 void TextDiagnosticPrinter::HighlightRange(const SourceRange &R,
-                                           const SourceManager& SourceMgr,
-                                           unsigned LineNo, unsigned FileID,
+                                           const SourceManager &SourceMgr,
+                                           unsigned LineNo, FileID FID,
                                            std::string &CaretLine,
                                            const std::string &SourceLine) {
   assert(CaretLine.size() == SourceLine.size() &&
@@ -47,12 +47,14 @@ void TextDiagnosticPrinter::HighlightRange(const SourceRange &R,
   SourceLocation InstantiationStart =
     SourceMgr.getInstantiationLoc(R.getBegin());
   unsigned StartLineNo = SourceMgr.getLineNumber(InstantiationStart);
-  if (StartLineNo > LineNo || InstantiationStart.getFileID() != FileID)
+  if (StartLineNo > LineNo ||
+      SourceMgr.getCanonicalFileID(InstantiationStart) != FID)
     return;  // No intersection.
   
   SourceLocation InstantiationEnd = SourceMgr.getInstantiationLoc(R.getEnd());
   unsigned EndLineNo = SourceMgr.getLineNumber(InstantiationEnd);
-  if (EndLineNo < LineNo || InstantiationEnd.getFileID() != FileID)
+  if (EndLineNo < LineNo ||
+      SourceMgr.getCanonicalFileID(InstantiationEnd) != FID)
     return;  // No intersection.
   
   // Compute the column number of the start.
@@ -98,14 +100,14 @@ void TextDiagnosticPrinter::HighlightRange(const SourceRange &R,
 void TextDiagnosticPrinter::HandleDiagnostic(Diagnostic::Level Level, 
                                              const DiagnosticInfo &Info) {
   unsigned LineNo = 0, ColNo = 0;
-  unsigned FileID = 0;
+  FileID FID;
   const char *LineStart = 0, *LineEnd = 0;
   const FullSourceLoc &Pos = Info.getLocation();
   
   if (Pos.isValid()) {
     FullSourceLoc LPos = Pos.getInstantiationLoc();
+    FID = LPos.getFileID();
     LineNo = LPos.getLineNumber();
-    FileID = LPos.getFileID();
     
     // First, if this diagnostic is not in the main file, print out the
     // "included from" lines.
@@ -161,7 +163,7 @@ void TextDiagnosticPrinter::HandleDiagnostic(Diagnostic::Level Level,
     
     // Highlight all of the characters covered by Ranges with ~ characters.
     for (unsigned i = 0; i != Info.getNumRanges(); ++i)
-      HighlightRange(Info.getRange(i), Pos.getManager(), LineNo, FileID,
+      HighlightRange(Info.getRange(i), Pos.getManager(), LineNo, FID,
                      CaretLine, SourceLine);
     
     // Next, insert the caret itself.
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index 90785b5e1930..6e5402e8a375 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -321,7 +321,7 @@ static SourceLocation GetMappedTokenLoc(Preprocessor &PP,
   // characters come from spelling(FileLoc)+Offset.
   SourceLocation InstLoc = SourceMgr.getInstantiationLoc(FileLoc);
   SourceLocation SpellingLoc = SourceMgr.getSpellingLoc(FileLoc);
-  SpellingLoc = SourceLocation::getFileLoc(SpellingLoc.getFileID(), CharNo);
+  SpellingLoc = SourceLocation::getFileLoc(SpellingLoc.getChunkID(), CharNo);
   return SourceMgr.getInstantiationLoc(SpellingLoc, InstLoc);
 }
 
@@ -335,7 +335,7 @@ SourceLocation Lexer::getSourceLocation(const char *Loc) const {
   // the file id from FileLoc with the offset specified.
   unsigned CharNo = Loc-BufferStart;
   if (FileLoc.isFileID())
-    return SourceLocation::getFileLoc(FileLoc.getFileID(), CharNo);
+    return SourceLocation::getFileLoc(FileLoc.getChunkID(), CharNo);
   
   // Otherwise, this is the _Pragma lexer case, which pretends that all of the
   // tokens are lexed from where the _Pragma was defined.