diff --git a/lib/Analysis/DebugInfo.cpp b/lib/Analysis/DebugInfo.cpp
index e5bbbd5..0ec8089 100644
--- a/lib/Analysis/DebugInfo.cpp
+++ b/lib/Analysis/DebugInfo.cpp
@@ -442,6 +442,7 @@
                                            const std::string &Filename,
                                            const std::string &Directory,
                                            const std::string &Producer,
+                                           bool isMain,
                                            bool isOptimized,
                                            const char *Flags) {
   Constant *Elts[] = {
@@ -451,6 +452,7 @@
     GetStringConstant(Filename),
     GetStringConstant(Directory),
     GetStringConstant(Producer),
+    ConstantInt::get(Type::Int1Ty, isMain),
     ConstantInt::get(Type::Int1Ty, isOptimized),
     GetStringConstant(Flags)
   };
@@ -492,9 +494,7 @@
                                        uint64_t SizeInBits,
                                        uint64_t AlignInBits,
                                        uint64_t OffsetInBits, unsigned Flags,
-                                       unsigned Encoding,
-                                       const std::string *FileName,
-                                       const std::string *Directory) {
+                                       unsigned Encoding) {
   Constant *Elts[] = {
     GetTagConstant(dwarf::DW_TAG_base_type),
     getCastToEmpty(Context),
@@ -505,9 +505,7 @@
     ConstantInt::get(Type::Int64Ty, AlignInBits),
     ConstantInt::get(Type::Int64Ty, OffsetInBits),
     ConstantInt::get(Type::Int32Ty, Flags),
-    ConstantInt::get(Type::Int32Ty, Encoding),
-    GetStringConstant(FileName ? FileName->c_str() : ""),
-    GetStringConstant(Directory ? Directory->c_str() : "")
+    ConstantInt::get(Type::Int32Ty, Encoding)
   };
   
   Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
@@ -531,9 +529,7 @@
                                            uint64_t AlignInBits,
                                            uint64_t OffsetInBits,
                                            unsigned Flags,
-                                           DIType DerivedFrom,
-                                           const std::string *FileName,
-                                           const std::string *Directory) {
+                                           DIType DerivedFrom) {
   Constant *Elts[] = {
     GetTagConstant(Tag),
     getCastToEmpty(Context),
@@ -544,9 +540,7 @@
     ConstantInt::get(Type::Int64Ty, AlignInBits),
     ConstantInt::get(Type::Int64Ty, OffsetInBits),
     ConstantInt::get(Type::Int32Ty, Flags),
-    getCastToEmpty(DerivedFrom),
-    GetStringConstant(FileName ? FileName->c_str() : ""),
-    GetStringConstant(Directory ? Directory->c_str() : "")
+    getCastToEmpty(DerivedFrom)
   };
   
   Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
@@ -570,9 +564,7 @@
                                                uint64_t OffsetInBits,
                                                unsigned Flags,
                                                DIType DerivedFrom,
-                                               DIArray Elements,
-                                               const std::string *FileName,
-                                               const std::string *Directory) {
+                                               DIArray Elements) {
 
   Constant *Elts[] = {
     GetTagConstant(Tag),
@@ -585,9 +577,7 @@
     ConstantInt::get(Type::Int64Ty, OffsetInBits),
     ConstantInt::get(Type::Int32Ty, Flags),
     getCastToEmpty(DerivedFrom),
-    getCastToEmpty(Elements),
-    GetStringConstant(FileName ? FileName->c_str() : ""),
-    GetStringConstant(Directory ? Directory->c_str() : "")
+    getCastToEmpty(Elements)
   };
   
   Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
@@ -611,9 +601,7 @@
                                          DICompileUnit CompileUnit,
                                          unsigned LineNo, DIType Type,
                                          bool isLocalToUnit,
-                                         bool isDefinition,
-                                         const std::string *FileName,
-                                         const std::string *Directory) {
+                                         bool isDefinition) {
 
   Constant *Elts[] = {
     GetTagConstant(dwarf::DW_TAG_subprogram),
@@ -626,9 +614,7 @@
     ConstantInt::get(Type::Int32Ty, LineNo),
     getCastToEmpty(Type),
     ConstantInt::get(Type::Int1Ty, isLocalToUnit),
-    ConstantInt::get(Type::Int1Ty, isDefinition),
-    GetStringConstant(FileName ? FileName->c_str() : ""),
-    GetStringConstant(Directory ? Directory->c_str() : "")
+    ConstantInt::get(Type::Int1Ty, isDefinition)
   };
   
   Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
@@ -648,9 +634,7 @@
                                 const std::string &LinkageName,
                                 DICompileUnit CompileUnit,
                                 unsigned LineNo, DIType Type,bool isLocalToUnit,
-                                bool isDefinition, llvm::GlobalVariable *Val,
-                                const std::string *FileName,
-                                const std::string *Directory) {
+                                bool isDefinition, llvm::GlobalVariable *Val) {
   Constant *Elts[] = {
     GetTagConstant(dwarf::DW_TAG_variable),
     getCastToEmpty(GetOrCreateGlobalVariableAnchor()),
@@ -663,9 +647,7 @@
     getCastToEmpty(Type),
     ConstantInt::get(Type::Int1Ty, isLocalToUnit),
     ConstantInt::get(Type::Int1Ty, isDefinition),
-    ConstantExpr::getBitCast(Val, EmptyStructPtr),
-    GetStringConstant(FileName ? FileName->c_str() : ""),
-    GetStringConstant(Directory ? Directory->c_str() : "")
+    ConstantExpr::getBitCast(Val, EmptyStructPtr)
   };
   
   Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
@@ -683,20 +665,14 @@
 DIVariable DIFactory::CreateVariable(unsigned Tag, DIDescriptor Context,
                                      const std::string &Name,
                                      DICompileUnit CompileUnit, unsigned LineNo,
-                                     DIType Type,
-                                     const std::string *FileName,
-                                     const std::string *Directory) {
-
-  
+                                     DIType Type) {
   Constant *Elts[] = {
     GetTagConstant(Tag),
     getCastToEmpty(Context),
     GetStringConstant(Name),
     getCastToEmpty(CompileUnit),
     ConstantInt::get(Type::Int32Ty, LineNo),
-    getCastToEmpty(Type),
-    GetStringConstant(FileName ? FileName->c_str() : ""),
-    GetStringConstant(Directory ? Directory->c_str() : "")
+    getCastToEmpty(Type)
   };
   
   Constant *Init = ConstantStruct::get(Elts, sizeof(Elts)/sizeof(Elts[0]));
diff --git a/lib/CodeGen/AsmPrinter/DwarfWriter.cpp b/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
index b2a52ca..95990cf 100644
--- a/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfWriter.cpp
@@ -1274,6 +1274,9 @@
   /// of each entry in this vector corresponds to the sources in MMI.
   DenseMap<Value *, CompileUnit *> DW_CUs;
 
+  /// MainCU - Some platform prefers one compile unit per .o file. In such
+  /// cases, all dies are inserted in MainCU.
+  CompileUnit *MainCU;
   /// AbbreviationsSet - Used to uniquely define abbreviations.
   ///
   FoldingSet<DIEAbbrev> AbbreviationsSet;
@@ -1559,16 +1562,8 @@
   void AddSourceLine(DIE *Die, const DIVariable *V) {
     unsigned FileID = 0;
     unsigned Line = V->getLineNumber();
-    if (V->getVersion() <= LLVMDebugVersion6) {
-      // Version6 or earlier. Use compile unit info to get file id.
-      CompileUnit *Unit = FindCompileUnit(V->getCompileUnit());
-      FileID = Unit->getID();
-    } else {
-      // Version7 or newer, use filename and directory info from DIVariable
-      // directly.
-      unsigned DID = Directories.idFor(V->getDirectory());
-      FileID = SrcFiles.idFor(SrcFileInfo(DID, V->getFilename()));
-    }
+    CompileUnit *Unit = FindCompileUnit(V->getCompileUnit());
+    FileID = Unit->getID();
     AddUInt(Die, DW_AT_decl_file, 0, FileID);
     AddUInt(Die, DW_AT_decl_line, 0, Line);
   }
@@ -1578,16 +1573,8 @@
   void AddSourceLine(DIE *Die, const DIGlobal *G) {
     unsigned FileID = 0;
     unsigned Line = G->getLineNumber();
-    if (G->getVersion() <= LLVMDebugVersion6) {
-      // Version6 or earlier. Use compile unit info to get file id.
-      CompileUnit *Unit = FindCompileUnit(G->getCompileUnit());
-      FileID = Unit->getID();
-    } else {
-      // Version7 or newer, use filename and directory info from DIGlobal
-      // directly.
-      unsigned DID = Directories.idFor(G->getDirectory());
-      FileID = SrcFiles.idFor(SrcFileInfo(DID, G->getFilename()));
-    }
+    CompileUnit *Unit = FindCompileUnit(G->getCompileUnit());
+    FileID = Unit->getID();
     AddUInt(Die, DW_AT_decl_file, 0, FileID);
     AddUInt(Die, DW_AT_decl_line, 0, Line);
   }
@@ -1595,16 +1582,11 @@
   void AddSourceLine(DIE *Die, const DIType *Ty) {
     unsigned FileID = 0;
     unsigned Line = Ty->getLineNumber();
-    if (Ty->getVersion() <= LLVMDebugVersion6) {
-      // Version6 or earlier. Use compile unit info to get file id.
-      CompileUnit *Unit = FindCompileUnit(Ty->getCompileUnit());
-      FileID = Unit->getID();
-    } else {
-      // Version7 or newer, use filename and directory info from DIType
-      // directly.
-      unsigned DID = Directories.idFor(Ty->getDirectory());
-      FileID = SrcFiles.idFor(SrcFileInfo(DID, Ty->getFilename()));
-    }
+    DICompileUnit CU = Ty->getCompileUnit();
+    if (CU.isNull())
+      return;
+    CompileUnit *Unit = FindCompileUnit(CU);
+    FileID = Unit->getID();
     AddUInt(Die, DW_AT_decl_file, 0, FileID);
     AddUInt(Die, DW_AT_decl_line, 0, Line);
   }
@@ -2091,7 +2073,9 @@
     DISubprogram SPD(Desc.getGV());
 
     // Get the compile unit context.
-    CompileUnit *Unit = FindCompileUnit(SPD.getCompileUnit());
+    CompileUnit *Unit = MainCU;
+    if (!Unit)
+      Unit = FindCompileUnit(SPD.getCompileUnit());
 
     // Get the subprogram die.
     DIE *SPDie = Unit->getDieMapSlotFor(SPD.getGV());
@@ -2122,7 +2106,9 @@
 
       if (SPD.getName() == MF->getFunction()->getName()) {
         // Get the compile unit context.
-        CompileUnit *Unit = FindCompileUnit(SPD.getCompileUnit());
+        CompileUnit *Unit = MainCU;
+        if (!Unit)
+          Unit = FindCompileUnit(SPD.getCompileUnit());
 
         // Get the subprogram die.
         DIE *SPDie = Unit->getDieMapSlotFor(SPD.getGV());
@@ -2294,6 +2280,15 @@
   ///
   void SizeAndOffsets() {
     // Process base compile unit.
+    if (MainCU) {
+      // Compute size of compile unit header
+      unsigned Offset = sizeof(int32_t) + // Length of Compilation Unit Info
+        sizeof(int16_t) + // DWARF version number
+        sizeof(int32_t) + // Offset Into Abbrev. Section
+        sizeof(int8_t);   // Pointer Size (in bytes)
+      SizeAndOffsetDie(MainCU->getDie(), Offset, true);
+      return;
+    }
     for (DenseMap<Value *, CompileUnit *>::iterator CI = DW_CUs.begin(),
            CE = DW_CUs.end(); CI != CE; ++CI) {
       CompileUnit *Unit = CI->second;
@@ -2315,6 +2310,8 @@
     for (DenseMap<Value *, CompileUnit *>::iterator CI = DW_CUs.begin(),
            CE = DW_CUs.end(); CI != CE; ++CI) {
       CompileUnit *Unit = CI->second;
+      if (MainCU)
+        Unit = MainCU;
       DIE *Die = Unit->getDie();
       // Emit the compile units header.
       EmitLabel("info_begin", Unit->getID());
@@ -2340,6 +2337,8 @@
       EmitLabel("info_end", Unit->getID());
       
       Asm->EOL();
+      if (MainCU)
+        return;
     }
   }
 
@@ -2639,6 +2638,8 @@
     for (DenseMap<Value *, CompileUnit *>::iterator CI = DW_CUs.begin(),
            CE = DW_CUs.end(); CI != CE; ++CI) {
       CompileUnit *Unit = CI->second;
+      if (MainCU)
+        Unit = MainCU;
 
       EmitDifference("pubnames_end", Unit->getID(),
                      "pubnames_begin", Unit->getID(), true);
@@ -2672,6 +2673,8 @@
       EmitLabel("pubnames_end", Unit->getID());
       
       Asm->EOL();
+      if (MainCU)
+        return;
     }
   }
 
@@ -2789,6 +2792,10 @@
         AddString(Die, DW_AT_APPLE_flags, DW_FORM_string, Flags);
 
       CompileUnit *Unit = new CompileUnit(ID, Die);
+      if (DIUnit.isMain()) {
+        assert (!MainCU && "Multiple main compile units are found!");
+        MainCU = Unit;
+      }
       DW_CUs[DIUnit.getGV()] = Unit;
     }
   }
@@ -2802,7 +2809,9 @@
     for (std::vector<GlobalVariable *>::iterator GVI = Result.begin(),
            GVE = Result.end(); GVI != GVE; ++GVI) {
       DIGlobalVariable DI_GV(*GVI);
-      CompileUnit *DW_Unit = FindCompileUnit(DI_GV.getCompileUnit());
+      CompileUnit *DW_Unit = MainCU;
+      if (!DW_Unit)
+        DW_Unit = FindCompileUnit(DI_GV.getCompileUnit());
 
       // Check for pre-existence.
       DIE *&Slot = DW_Unit->getDieMapSlotFor(DI_GV.getGV());
@@ -2839,7 +2848,9 @@
            RE = Result.end(); RI != RE; ++RI) {
 
       DISubprogram SP(*RI);
-      CompileUnit *Unit = FindCompileUnit(SP.getCompileUnit());
+      CompileUnit *Unit = MainCU;
+      if (!Unit)
+        Unit = FindCompileUnit(SP.getCompileUnit());
 
       // Check for pre-existence.
       DIE *&Slot = Unit->getDieMapSlotFor(SP.getGV());
@@ -2862,6 +2873,7 @@
   //
   DwarfDebug(raw_ostream &OS, AsmPrinter *A, const TargetAsmInfo *T)
   : Dwarf(OS, A, T, "dbg")
+  , MainCU(NULL)
   , AbbreviationsSet(InitAbbreviationsSetSize)
   , Abbreviations()
   , ValuesSet(InitValuesSetSize)