diff --git a/lib/MC/CMakeLists.txt b/lib/MC/CMakeLists.txt
index fc4f3c6..7b9b355 100644
--- a/lib/MC/CMakeLists.txt
+++ b/lib/MC/CMakeLists.txt
@@ -11,6 +11,7 @@
   MCInst.cpp
   MCInstPrinter.cpp
   MCLabel.cpp
+  MCDwarf.cpp
   MCLoggingStreamer.cpp
   MCMachOStreamer.cpp
   MCNullStreamer.cpp
diff --git a/lib/MC/MCContext.cpp b/lib/MC/MCContext.cpp
index 1137064..7470e8d 100644
--- a/lib/MC/MCContext.cpp
+++ b/lib/MC/MCContext.cpp
@@ -14,6 +14,7 @@
 #include "llvm/MC/MCSectionCOFF.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCLabel.h"
+#include "llvm/MC/MCDwarf.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/Twine.h"
 using namespace llvm;
@@ -181,3 +182,63 @@
   Entry.setValue(Result);
   return Result;
 }
+
+//===----------------------------------------------------------------------===//
+// Dwarf Management
+//===----------------------------------------------------------------------===//
+
+/// GetDwarfFile - takes a file name an number to place in the dwarf file and
+/// directory tables.  If the file number has already been allocated it is an
+/// error and zero is returned and the client reports the error, else the
+/// allocated file number is returned.  The file numbers may be in any order.
+unsigned MCContext::GetDwarfFile(StringRef FileName, unsigned FileNumber) {
+  // TODO: a FileNumber of zero says to use the next available file number.
+  // Note: in GenericAsmParser::ParseDirectiveFile() FileNumber was checked
+  // to not be less than one.  This needs to be change to be not less than zero.
+
+  // Make space for this FileNumber in the MCDwarfFiles vector if needed.
+  if (FileNumber >= MCDwarfFiles.size()) {
+    MCDwarfFiles.resize(FileNumber + 1);
+  } else {
+    MCDwarfFile *&ExistingFile = MCDwarfFiles[FileNumber];
+    if (ExistingFile)
+      // It is an error to use see the same number more than once.
+      return 0;
+  }
+
+  // Get the new MCDwarfFile slot for this FileNumber.
+  MCDwarfFile *&File = MCDwarfFiles[FileNumber];
+
+  // Separate the directory part from the basename of the FileName.
+  std::pair<StringRef, StringRef> Slash = FileName.rsplit('/');
+
+  // Find or make a entry in the MCDwarfDirs vector for this Directory.
+  StringRef Directory;
+  StringRef Name;
+  unsigned DirIndex;
+  // Capture directory name.
+  if (Slash.second.empty()) {
+    Name = Slash.first;
+    DirIndex = 0; // For FileNames with no directories a DirIndex of 0 is used.
+  } else {
+    Directory = Slash.first;
+    Name = Slash.second;
+    for (DirIndex = 1; DirIndex < MCDwarfDirs.size(); DirIndex++) {
+      std::string *&Dir = MCDwarfDirs[DirIndex];
+      if (Directory == *Dir)
+	break;
+    }
+    if (DirIndex >= MCDwarfDirs.size()) {
+      MCDwarfDirs.resize(DirIndex + 1);
+      std::string *&NewDir = MCDwarfDirs[DirIndex];
+      NewDir = new (*this) std::string(Directory);
+    }
+  }
+  
+  // Now make the MCDwarfFile entry and place it in the slot in the MCDwarfFiles
+  // vector.
+  File = new (*this) MCDwarfFile(Name, DirIndex);
+
+  // return the allocated FileNumber.
+  return FileNumber;
+}
diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
new file mode 100644
index 0000000..2da71f9
--- /dev/null
+++ b/lib/MC/MCDwarf.cpp
@@ -0,0 +1,21 @@
+//===- lib/MC/MCDwarf.cpp - MCDwarf implementation ------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCDwarf.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+void MCDwarfFile::print(raw_ostream &OS) const {
+  OS << '"' << getName() << '"';
+}
+
+void MCDwarfFile::dump() const {
+  print(dbgs());
+}
diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index 61d65b8..e74952a 100644
--- a/lib/MC/MCParser/AsmParser.cpp
+++ b/lib/MC/MCParser/AsmParser.cpp
@@ -26,6 +26,7 @@
 #include "llvm/MC/MCSectionMachO.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCDwarf.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/SourceMgr.h"
@@ -370,6 +371,16 @@
   if (TheCondState.TheCond != StartingCondState.TheCond ||
       TheCondState.Ignore != StartingCondState.Ignore)
     return TokError("unmatched .ifs or .elses");
+
+  // Check to see there are no empty DwarfFile slots.
+  const std::vector<MCDwarfFile *> &MCDwarfFiles =
+    getContext().getMCDwarfFiles();
+  for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
+    if (!MCDwarfFiles[i]){
+      TokError("unassigned file number: " + Twine(i) + " for .file directives");
+      HadError = true;
+    }
+  }
   
   // Finalize the output stream if there are no errors and if the client wants
   // us to.
@@ -1729,6 +1740,7 @@
 bool GenericAsmParser::ParseDirectiveFile(StringRef, SMLoc DirectiveLoc) {
   // FIXME: I'm not sure what this is.
   int64_t FileNumber = -1;
+  SMLoc FileNumberLoc = getLexer().getLoc();
   if (getLexer().is(AsmToken::Integer)) {
     FileNumber = getTok().getIntVal();
     Lex();
@@ -1749,8 +1761,11 @@
 
   if (FileNumber == -1)
     getStreamer().EmitFileDirective(Filename);
-  else
+  else {
+     if (getContext().GetDwarfFile(Filename, FileNumber) == 0)
+	Error(FileNumberLoc, "file number already allocated");
     getStreamer().EmitDwarfFileDirective(FileNumber, Filename);
+  }
 
   return false;
 }