diff --git a/include/llvm/MC/MCDwarf.h b/include/llvm/MC/MCDwarf.h
index 3b604506144..720da188aa8 100644
--- a/include/llvm/MC/MCDwarf.h
+++ b/include/llvm/MC/MCDwarf.h
@@ -182,7 +182,8 @@ struct MCDwarfLineTableHeader {
   SmallVector<MCDwarfFile, 3> MCDwarfFiles;
   StringMap<unsigned> SourceIdMap;
   MCDwarfLineTableHeader() : Label(nullptr) {}
-  unsigned getFile(StringRef Directory, StringRef FileName, unsigned FileNumber = 0);
+  unsigned getFile(StringRef &Directory, StringRef &FileName,
+                   unsigned FileNumber = 0);
   std::pair<MCSymbol *, MCSymbol *> Emit(MCStreamer *MCOS) const;
 };
 
@@ -197,7 +198,8 @@ public:
   // This emits the Dwarf file and the line tables for a given Compile Unit.
   const MCSymbol *EmitCU(MCStreamer *MCOS) const;
 
-  unsigned getFile(StringRef Directory, StringRef FileName, unsigned FileNumber = 0);
+  unsigned getFile(StringRef &Directory, StringRef &FileName,
+                   unsigned FileNumber = 0);
 
   MCSymbol *getLabel() const {
     return Header.Label;
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index a03da3c452a..4791e6d5ade 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -171,8 +171,7 @@ static unsigned getDwarfVersionFromModule(const Module *M) {
 }
 
 DwarfDebug::DwarfDebug(AsmPrinter *A, Module *M)
-    : Asm(A), MMI(Asm->MMI), FirstCU(0), SourceIdMap(DIEValueAllocator),
-      PrevLabel(NULL), GlobalRangeCount(0),
+    : Asm(A), MMI(Asm->MMI), FirstCU(0), PrevLabel(NULL), GlobalRangeCount(0),
       InfoHolder(A, "info_string", DIEValueAllocator), HasCURanges(false),
       UsedNonDefaultText(false),
       SkeletonHolder(A, "skel_string", DIEValueAllocator) {
@@ -680,36 +679,12 @@ unsigned DwarfDebug::getOrCreateSourceID(StringRef FileName, StringRef DirName,
   if (Asm->OutStreamer.hasRawTextSupport())
     CUID = 0;
 
-  // If FE did not provide a file name, then assume stdin.
-  if (FileName.empty()) {
-    FileName = "<stdin>";
-    DirName = "";
-  }
-
   // TODO: this might not belong here. See if we can factor this better.
   if (DirName == CompilationDir)
     DirName = "";
 
-  // FileIDCUMap stores the current ID for the given compile unit.
-  unsigned SrcId = FileIDCUMap[CUID] + 1;
-
-  // We look up the CUID/file/dir by concatenating them with a zero byte.
-  SmallString<128> NamePair;
-  NamePair += utostr(CUID);
-  NamePair += '\0';
-  NamePair += DirName;
-  NamePair += '\0'; // Zero bytes are not allowed in paths.
-  NamePair += FileName;
-
-  StringMapEntry<unsigned> &Ent = SourceIdMap.GetOrCreateValue(NamePair, SrcId);
-  if (Ent.getValue() != SrcId)
-    return Ent.getValue();
-
-  FileIDCUMap[CUID] = SrcId;
   // Print out a .file directive to specify files for .loc directives.
-  Asm->OutStreamer.EmitDwarfFileDirective(SrcId, DirName, FileName, CUID);
-
-  return SrcId;
+  return Asm->OutStreamer.EmitDwarfFileDirective(0, DirName, FileName, CUID);
 }
 
 void DwarfDebug::addGnuPubAttributes(DwarfUnit *U, DIE *D) const {
@@ -730,8 +705,6 @@ DwarfCompileUnit *DwarfDebug::constructDwarfCompileUnit(DICompileUnit DIUnit) {
       InfoHolder.getUnits().size(), Die, DIUnit, Asm, this, &InfoHolder);
   InfoHolder.addUnit(NewCU);
 
-  FileIDCUMap[NewCU->getUniqueID()] = 0;
-
   NewCU->addString(Die, dwarf::DW_AT_producer, DIUnit.getProducer());
   NewCU->addUInt(Die, dwarf::DW_AT_language, dwarf::DW_FORM_data2,
                  DIUnit.getLanguage());
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.h b/lib/CodeGen/AsmPrinter/DwarfDebug.h
index baf87323178..3ab537037d9 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -356,12 +356,6 @@ class DwarfDebug : public AsmPrinterHandler {
   // Used to unique C++ member function declarations.
   StringMap<const MDNode *> OdrMemberMap;
 
-  // Stores the current file ID for a given compile unit.
-  DenseMap<unsigned, unsigned> FileIDCUMap;
-  // Source id map, i.e. CUID, source filename and directory,
-  // separated by a zero byte, mapped to a unique id.
-  StringMap<unsigned, BumpPtrAllocator &> SourceIdMap;
-
   // List of all labels used in aranges generation.
   std::vector<SymbolCU> ArangeLabels;
 
diff --git a/lib/MC/MCAsmStreamer.cpp b/lib/MC/MCAsmStreamer.cpp
index b40305d0fc2..85263fec626 100644
--- a/lib/MC/MCAsmStreamer.cpp
+++ b/lib/MC/MCAsmStreamer.cpp
@@ -848,13 +848,27 @@ unsigned MCAsmStreamer::EmitDwarfFileDirective(unsigned FileNo,
                                                StringRef Directory,
                                                StringRef Filename,
                                                unsigned CUID) {
+  assert(CUID == 0);
+
+  MCDwarfLineTable &Table = getContext().getMCDwarfLineTable(CUID);
+  unsigned NumFiles = Table.getMCDwarfFiles().size();
+  FileNo = Table.getFile(Directory, Filename, FileNo);
+  if (FileNo == 0)
+    return 0;
+  if (NumFiles == Table.getMCDwarfFiles().size())
+    return FileNo;
+
+  SmallString<128> FullPathName;
+
   if (!UseDwarfDirectory && !Directory.empty()) {
     if (sys::path::is_absolute(Filename))
-      return EmitDwarfFileDirective(FileNo, "", Filename, CUID);
-
-    SmallString<128> FullPathName = Directory;
-    sys::path::append(FullPathName, Filename);
-    return EmitDwarfFileDirective(FileNo, "", FullPathName, CUID);
+      Directory = "";
+    else {
+      FullPathName = Directory;
+      sys::path::append(FullPathName, Filename);
+      Directory = "";
+      Filename = FullPathName;
+    }
   }
 
   OS << "\t.file\t" << FileNo << ' ';
@@ -864,11 +878,8 @@ unsigned MCAsmStreamer::EmitDwarfFileDirective(unsigned FileNo,
   }
   PrintQuotedString(Filename, OS);
   EmitEOL();
-  // All .file will belong to a single CUID.
-  CUID = 0;
 
-  return this->MCStreamer::EmitDwarfFileDirective(FileNo, Directory, Filename,
-                                                  CUID);
+  return FileNo;
 }
 
 void MCAsmStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
index 72ecfa6cb45..edeee20ab47 100644
--- a/lib/MC/MCDwarf.cpp
+++ b/lib/MC/MCDwarf.cpp
@@ -287,6 +287,7 @@ std::pair<MCSymbol *, MCSymbol *> MCDwarfLineTableHeader::Emit(MCStreamer *MCOS)
 
   // Second the file table.
   for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
+    assert(!MCDwarfFiles[i].Name.empty());
     MCOS->EmitBytes(MCDwarfFiles[i].Name); // FileName
     MCOS->EmitBytes(StringRef("\0", 1)); // the null term. of the string
     // the Directory num
@@ -331,14 +332,19 @@ const MCSymbol *MCDwarfLineTable::EmitCU(MCStreamer *MCOS) const {
   return LineStartSym;
 }
 
-unsigned MCDwarfLineTable::getFile(StringRef Directory, StringRef FileName,
+unsigned MCDwarfLineTable::getFile(StringRef &Directory, StringRef &FileName,
                                    unsigned FileNumber) {
   return Header.getFile(Directory, FileName, FileNumber);
 }
 
-unsigned MCDwarfLineTableHeader::getFile(StringRef Directory,
-                                         StringRef FileName,
+unsigned MCDwarfLineTableHeader::getFile(StringRef &Directory,
+                                         StringRef &FileName,
                                          unsigned FileNumber) {
+  if (FileName.empty()) {
+    FileName = "<stdin>";
+    Directory = "";
+  }
+  assert(!FileName.empty());
   if (FileNumber == 0) {
     FileNumber = SourceIdMap.size() + 1;
     assert((MCDwarfFiles.empty() || FileNumber == MCDwarfFiles.size()) &&