DwarfDebug.cpp

  Buffer.setTag(Tag);

  // Map to main type, void will not have a type.
  DIType FromTy = DTy.getTypeDerivedFrom();
  addType(&Buffer, FromTy);

  // Add name if not anonymous or intermediate type.
  if (!Name.empty())
    addString(&Buffer, dwarf::DW_AT_name, dwarf::DW_FORM_string, Name);

  // Add size if non-zero (derived types might be zero-sized.)
  if (Size)
    addUInt(&Buffer, dwarf::DW_AT_byte_size, 0, Size);

  // Add source line info if available and TyDesc is not a forward declaration.
  if (!DTy.isForwardDecl())
    addSourceLine(&Buffer, DTy);
}

/// constructTypeDIE - Construct type DIE from DICompositeType.
void DwarfDebug::constructTypeDIE(DIE &Buffer, DICompositeType CTy) {
  // Get core information.
  StringRef Name = CTy.getName();

  uint64_t Size = CTy.getSizeInBits() >> 3;
  unsigned Tag = CTy.getTag();
  Buffer.setTag(Tag);

  switch (Tag) {
  case dwarf::DW_TAG_vector_type:
  case dwarf::DW_TAG_array_type:
    constructArrayTypeDIE(Buffer, &CTy);
    break;
  case dwarf::DW_TAG_enumeration_type: {
    DIArray Elements = CTy.getTypeArray();

    // Add enumerators to enumeration type.
    for (unsigned i = 0, N = Elements.getNumElements(); i < N; ++i) {
      DIE *ElemDie = NULL;
      DIDescriptor Enum(Elements.getElement(i));
      if (Enum.isEnumerator()) {
        ElemDie = constructEnumTypeDIE(DIEnumerator(Enum));
        Buffer.addChild(ElemDie);
      }
    }
  }
    break;
  case dwarf::DW_TAG_subroutine_type: {
    // Add return type.
    DIArray Elements = CTy.getTypeArray();
    DIDescriptor RTy = Elements.getElement(0);
    addType(&Buffer, DIType(RTy));

    bool isPrototyped = true;
    // Add arguments.
    for (unsigned i = 1, N = Elements.getNumElements(); i < N; ++i) {
      DIDescriptor Ty = Elements.getElement(i);
      if (Ty.isUnspecifiedParameter()) {
        DIE *Arg = new DIE(dwarf::DW_TAG_unspecified_parameters);
        Buffer.addChild(Arg);
        isPrototyped = false;
      } else {
        DIE *Arg = new DIE(dwarf::DW_TAG_formal_parameter);
        addType(Arg, DIType(Ty));
        Buffer.addChild(Arg);
      }
    }
    // Add prototype flag.
    if (isPrototyped)
      addUInt(&Buffer, dwarf::DW_AT_prototyped, dwarf::DW_FORM_flag, 1);
  }
    break;
  case dwarf::DW_TAG_structure_type:
  case dwarf::DW_TAG_union_type:
  case dwarf::DW_TAG_class_type: {
    // Add elements to structure type.
    DIArray Elements = CTy.getTypeArray();

    // A forward struct declared type may not have elements available.
    unsigned N = Elements.getNumElements();
    if (N == 0)
      break;

    // Add elements to structure type.
    for (unsigned i = 0; i < N; ++i) {
      DIDescriptor Element = Elements.getElement(i);
      DIE *ElemDie = NULL;
      if (Element.isSubprogram()) {
        DISubprogram SP(Element);
        ElemDie = createSubprogramDIE(DISubprogram(Element));
        if (SP.isProtected())
          addUInt(ElemDie, dwarf::DW_AT_accessibility, dwarf::DW_FORM_flag,
                  dwarf::DW_ACCESS_protected);
        else if (SP.isPrivate())
          addUInt(ElemDie, dwarf::DW_AT_accessibility, dwarf::DW_FORM_flag,
                  dwarf::DW_ACCESS_private);
        else 
          addUInt(ElemDie, dwarf::DW_AT_accessibility, dwarf::DW_FORM_flag,
            dwarf::DW_ACCESS_public);
        if (SP.isExplicit())
          addUInt(ElemDie, dwarf::DW_AT_explicit, dwarf::DW_FORM_flag, 1);
      }
      else if (Element.isVariable()) {
        DIVariable DV(Element);
        ElemDie = new DIE(dwarf::DW_TAG_variable);
        addString(ElemDie, dwarf::DW_AT_name, dwarf::DW_FORM_string,
                  DV.getName());
        addType(ElemDie, DV.getType());
        addUInt(ElemDie, dwarf::DW_AT_declaration, dwarf::DW_FORM_flag, 1);
        addUInt(ElemDie, dwarf::DW_AT_external, dwarf::DW_FORM_flag, 1);
        addSourceLine(ElemDie, DV);
      } else if (Element.isDerivedType())
        ElemDie = createMemberDIE(DIDerivedType(Element));
      else
        continue;
      Buffer.addChild(ElemDie);
    }

    if (CTy.isAppleBlockExtension())
      addUInt(&Buffer, dwarf::DW_AT_APPLE_block, dwarf::DW_FORM_flag, 1);

    unsigned RLang = CTy.getRunTimeLang();
    if (RLang)
      addUInt(&Buffer, dwarf::DW_AT_APPLE_runtime_class,
              dwarf::DW_FORM_data1, RLang);

    DICompositeType ContainingType = CTy.getContainingType();
    if (DIDescriptor(ContainingType).isCompositeType())
      addDIEEntry(&Buffer, dwarf::DW_AT_containing_type, dwarf::DW_FORM_ref4,
                  getOrCreateTypeDIE(DIType(ContainingType)));
    else {
      DIDescriptor Context = CTy.getContext();
      addToContextOwner(&Buffer, Context);
    }
    break;
  }
  default:
    break;
  }

  // Add name if not anonymous or intermediate type.
  if (!Name.empty())
    addString(&Buffer, dwarf::DW_AT_name, dwarf::DW_FORM_string, Name);

  if (Tag == dwarf::DW_TAG_enumeration_type || Tag == dwarf::DW_TAG_class_type
      || Tag == dwarf::DW_TAG_structure_type || Tag == dwarf::DW_TAG_union_type)
    {
    // Add size if non-zero (derived types might be zero-sized.)
    if (Size)
      addUInt(&Buffer, dwarf::DW_AT_byte_size, 0, Size);
    else {
      // Add zero size if it is not a forward declaration.
      if (CTy.isForwardDecl())
        addUInt(&Buffer, dwarf::DW_AT_declaration, dwarf::DW_FORM_flag, 1);
      else
        addUInt(&Buffer, dwarf::DW_AT_byte_size, 0, 0);
    }

    // Add source line info if available.
    if (!CTy.isForwardDecl())
      addSourceLine(&Buffer, CTy);
  }
}

/// constructSubrangeDIE - Construct subrange DIE from DISubrange.
void DwarfDebug::constructSubrangeDIE(DIE &Buffer, DISubrange SR, DIE *IndexTy){
  int64_t L = SR.getLo();
  int64_t H = SR.getHi();
  DIE *DW_Subrange = new DIE(dwarf::DW_TAG_subrange_type);

  addDIEEntry(DW_Subrange, dwarf::DW_AT_type, dwarf::DW_FORM_ref4, IndexTy);
  if (L)
    addSInt(DW_Subrange, dwarf::DW_AT_lower_bound, 0, L);
  addSInt(DW_Subrange, dwarf::DW_AT_upper_bound, 0, H);

  Buffer.addChild(DW_Subrange);
}

/// constructArrayTypeDIE - Construct array type DIE from DICompositeType.
void DwarfDebug::constructArrayTypeDIE(DIE &Buffer,
                                       DICompositeType *CTy) {
  Buffer.setTag(dwarf::DW_TAG_array_type);
  if (CTy->getTag() == dwarf::DW_TAG_vector_type)
    addUInt(&Buffer, dwarf::DW_AT_GNU_vector, dwarf::DW_FORM_flag, 1);

  // Emit derived type.
  addType(&Buffer, CTy->getTypeDerivedFrom());
  DIArray Elements = CTy->getTypeArray();

  // Get an anonymous type for index type.
  CompileUnit *TheCU = getCompileUnit(*CTy);
  DIE *IdxTy = TheCU->getIndexTyDie();
  if (!IdxTy) {
    // Construct an anonymous type for index type.
    IdxTy = new DIE(dwarf::DW_TAG_base_type);
    addUInt(IdxTy, dwarf::DW_AT_byte_size, 0, sizeof(int32_t));
    addUInt(IdxTy, dwarf::DW_AT_encoding, dwarf::DW_FORM_data1,
            dwarf::DW_ATE_signed);
    TheCU->addDie(IdxTy);
    TheCU->setIndexTyDie(IdxTy);
  }

  // Add subranges to array type.
  for (unsigned i = 0, N = Elements.getNumElements(); i < N; ++i) {
    DIDescriptor Element = Elements.getElement(i);
    if (Element.getTag() == dwarf::DW_TAG_subrange_type)
      constructSubrangeDIE(Buffer, DISubrange(Element), IdxTy);
  }
}

/// constructEnumTypeDIE - Construct enum type DIE from DIEnumerator.
DIE *DwarfDebug::constructEnumTypeDIE(DIEnumerator ETy) {
  DIE *Enumerator = new DIE(dwarf::DW_TAG_enumerator);
  StringRef Name = ETy.getName();
  addString(Enumerator, dwarf::DW_AT_name, dwarf::DW_FORM_string, Name);
  int64_t Value = ETy.getEnumValue();
  addSInt(Enumerator, dwarf::DW_AT_const_value, dwarf::DW_FORM_sdata, Value);
  return Enumerator;
}

/// getRealLinkageName - If special LLVM prefix that is used to inform the asm
/// printer to not emit usual symbol prefix before the symbol name is used then
/// return linkage name after skipping this special LLVM prefix.
static StringRef getRealLinkageName(StringRef LinkageName) {
  char One = '\1';
  if (LinkageName.startswith(StringRef(&One, 1)))
    return LinkageName.substr(1);
  return LinkageName;
}

/// createMemberDIE - Create new member DIE.
DIE *DwarfDebug::createMemberDIE(DIDerivedType DT) {
  DIE *MemberDie = new DIE(DT.getTag());
  StringRef Name = DT.getName();
  if (!Name.empty())
    addString(MemberDie, dwarf::DW_AT_name, dwarf::DW_FORM_string, Name);

  addType(MemberDie, DT.getTypeDerivedFrom());

  addSourceLine(MemberDie, DT);

  DIEBlock *MemLocationDie = new (DIEValueAllocator) DIEBlock();
  addUInt(MemLocationDie, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_plus_uconst);

  uint64_t Size = DT.getSizeInBits();
  uint64_t FieldSize = DT.getOriginalTypeSize();

  if (Size != FieldSize) {
    // Handle bitfield.
    addUInt(MemberDie, dwarf::DW_AT_byte_size, 0, DT.getOriginalTypeSize()>>3);
    addUInt(MemberDie, dwarf::DW_AT_bit_size, 0, DT.getSizeInBits());

    uint64_t Offset = DT.getOffsetInBits();
    uint64_t AlignMask = ~(DT.getAlignInBits() - 1);
    uint64_t HiMark = (Offset + FieldSize) & AlignMask;
    uint64_t FieldOffset = (HiMark - FieldSize);
    Offset -= FieldOffset;

    // Maybe we need to work from the other end.
    if (Asm->getTargetData().isLittleEndian())
      Offset = FieldSize - (Offset + Size);
    addUInt(MemberDie, dwarf::DW_AT_bit_offset, 0, Offset);

    // Here WD_AT_data_member_location points to the anonymous
    // field that includes this bit field.
    addUInt(MemLocationDie, 0, dwarf::DW_FORM_udata, FieldOffset >> 3);

  } else
    // This is not a bitfield.
    addUInt(MemLocationDie, 0, dwarf::DW_FORM_udata, DT.getOffsetInBits() >> 3);

  if (DT.getTag() == dwarf::DW_TAG_inheritance
      && DT.isVirtual()) {

    // For C++, virtual base classes are not at fixed offset. Use following
    // expression to extract appropriate offset from vtable.
    // BaseAddr = ObAddr + *((*ObAddr) - Offset)

    DIEBlock *VBaseLocationDie = new (DIEValueAllocator) DIEBlock();
    addUInt(VBaseLocationDie, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_dup);
    addUInt(VBaseLocationDie, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_deref);
    addUInt(VBaseLocationDie, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_constu);
    addUInt(VBaseLocationDie, 0, dwarf::DW_FORM_udata, DT.getOffsetInBits());
    addUInt(VBaseLocationDie, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_minus);
    addUInt(VBaseLocationDie, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_deref);
    addUInt(VBaseLocationDie, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_plus);

    addBlock(MemberDie, dwarf::DW_AT_data_member_location, 0,
             VBaseLocationDie);
  } else
    addBlock(MemberDie, dwarf::DW_AT_data_member_location, 0, MemLocationDie);

  if (DT.isProtected())
    addUInt(MemberDie, dwarf::DW_AT_accessibility, dwarf::DW_FORM_flag,
            dwarf::DW_ACCESS_protected);
  else if (DT.isPrivate())
    addUInt(MemberDie, dwarf::DW_AT_accessibility, dwarf::DW_FORM_flag,
            dwarf::DW_ACCESS_private);
  // Otherwise C++ member and base classes are considered public.
  else if (DT.getCompileUnit().getLanguage() == dwarf::DW_LANG_C_plus_plus)
    addUInt(MemberDie, dwarf::DW_AT_accessibility, dwarf::DW_FORM_flag,
            dwarf::DW_ACCESS_public);
  if (DT.isVirtual())
    addUInt(MemberDie, dwarf::DW_AT_virtuality, dwarf::DW_FORM_flag,
            dwarf::DW_VIRTUALITY_virtual);
  return MemberDie;
}

/// createSubprogramDIE - Create new DIE using SP.
DIE *DwarfDebug::createSubprogramDIE(DISubprogram SP) {
  CompileUnit *SPCU = getCompileUnit(SP);
  DIE *SPDie = SPCU->getDIE(SP);
  if (SPDie)
    return SPDie;

  SPDie = new DIE(dwarf::DW_TAG_subprogram);
  // Constructors and operators for anonymous aggregates do not have names.
  if (!SP.getName().empty())
    addString(SPDie, dwarf::DW_AT_name, dwarf::DW_FORM_string, SP.getName());

  StringRef LinkageName = SP.getLinkageName();
  if (!LinkageName.empty())
    addString(SPDie, dwarf::DW_AT_MIPS_linkage_name, dwarf::DW_FORM_string,
              getRealLinkageName(LinkageName));

  addSourceLine(SPDie, SP);

  if (SP.isPrototyped()) 
    addUInt(SPDie, dwarf::DW_AT_prototyped, dwarf::DW_FORM_flag, 1);

  // Add Return Type.
  DICompositeType SPTy = SP.getType();
  DIArray Args = SPTy.getTypeArray();
  unsigned SPTag = SPTy.getTag();

  if (Args.getNumElements() == 0 || SPTag != dwarf::DW_TAG_subroutine_type)
    addType(SPDie, SPTy);
  else
    addType(SPDie, DIType(Args.getElement(0)));

  unsigned VK = SP.getVirtuality();
  if (VK) {
    addUInt(SPDie, dwarf::DW_AT_virtuality, dwarf::DW_FORM_flag, VK);
    DIEBlock *Block = new (DIEValueAllocator) DIEBlock();
    addUInt(Block, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_constu);
    addUInt(Block, 0, dwarf::DW_FORM_data1, SP.getVirtualIndex());
    addBlock(SPDie, dwarf::DW_AT_vtable_elem_location, 0, Block);
    ContainingTypeMap.insert(std::make_pair(SPDie,
                                            SP.getContainingType()));
  }

  if (!SP.isDefinition()) {
    addUInt(SPDie, dwarf::DW_AT_declaration, dwarf::DW_FORM_flag, 1);

    // Add arguments. Do not add arguments for subprogram definition. They will
    // be handled while processing variables.
    DICompositeType SPTy = SP.getType();
    DIArray Args = SPTy.getTypeArray();
    unsigned SPTag = SPTy.getTag();

    if (SPTag == dwarf::DW_TAG_subroutine_type)
      for (unsigned i = 1, N =  Args.getNumElements(); i < N; ++i) {
        DIE *Arg = new DIE(dwarf::DW_TAG_formal_parameter);
        DIType ATy = DIType(DIType(Args.getElement(i)));
        addType(Arg, ATy);
        if (ATy.isArtificial())
          addUInt(Arg, dwarf::DW_AT_artificial, dwarf::DW_FORM_flag, 1);
        SPDie->addChild(Arg);
      }
  }

  if (SP.isArtificial())
    addUInt(SPDie, dwarf::DW_AT_artificial, dwarf::DW_FORM_flag, 1);

  if (!SP.isLocalToUnit())
    addUInt(SPDie, dwarf::DW_AT_external, dwarf::DW_FORM_flag, 1);

  if (SP.isOptimized())
    addUInt(SPDie, dwarf::DW_AT_APPLE_optimized, dwarf::DW_FORM_flag, 1);

  if (unsigned isa = Asm->getISAEncoding()) {
    addUInt(SPDie, dwarf::DW_AT_APPLE_isa, dwarf::DW_FORM_flag, isa);
  }

  // DW_TAG_inlined_subroutine may refer to this DIE.
  SPCU->insertDIE(SP, SPDie);

  // Add to context owner.
  addToContextOwner(SPDie, SP.getContext());

  return SPDie;
}

DbgScope *DwarfDebug::getOrCreateAbstractScope(const MDNode *N) {
  assert(N && "Invalid Scope encoding!");

  DbgScope *AScope = AbstractScopes.lookup(N);
  if (AScope)
    return AScope;

  DbgScope *Parent = NULL;

  DIDescriptor Scope(N);
  if (Scope.isLexicalBlock()) {
    DILexicalBlock DB(N);
    DIDescriptor ParentDesc = DB.getContext();
    Parent = getOrCreateAbstractScope(ParentDesc);
  }

  AScope = new DbgScope(Parent, DIDescriptor(N), NULL);

  if (Parent)
    Parent->addScope(AScope);
  AScope->setAbstractScope();
  AbstractScopes[N] = AScope;
  if (DIDescriptor(N).isSubprogram())
    AbstractScopesList.push_back(AScope);
  return AScope;
}

/// isSubprogramContext - Return true if Context is either a subprogram
/// or another context nested inside a subprogram.
static bool isSubprogramContext(const MDNode *Context) {
  if (!Context)
    return false;
  DIDescriptor D(Context);
  if (D.isSubprogram())
    return true;
  if (D.isType())
    return isSubprogramContext(DIType(Context).getContext());
  return false;
}

/// updateSubprogramScopeDIE - Find DIE for the given subprogram and
/// attach appropriate DW_AT_low_pc and DW_AT_high_pc attributes.
/// If there are global variables in this scope then create and insert
/// DIEs for these variables.
DIE *DwarfDebug::updateSubprogramScopeDIE(const MDNode *SPNode) {
  CompileUnit *SPCU = getCompileUnit(SPNode);
  DIE *SPDie = SPCU->getDIE(SPNode);

  assert(SPDie && "Unable to find subprogram DIE!");
  DISubprogram SP(SPNode);

  // There is not any need to generate specification DIE for a function
  // defined at compile unit level. If a function is defined inside another
  // function then gdb prefers the definition at top level and but does not
  // expect specification DIE in parent function. So avoid creating
  // specification DIE for a function defined inside a function.
  if (SP.isDefinition() && !SP.getContext().isCompileUnit() &&
      !SP.getContext().isFile() &&
      !isSubprogramContext(SP.getContext())) {
    addUInt(SPDie, dwarf::DW_AT_declaration, dwarf::DW_FORM_flag, 1);

    // Add arguments.
    DICompositeType SPTy = SP.getType();
    DIArray Args = SPTy.getTypeArray();
    unsigned SPTag = SPTy.getTag();
    if (SPTag == dwarf::DW_TAG_subroutine_type)
      for (unsigned i = 1, N = Args.getNumElements(); i < N; ++i) {
        DIE *Arg = new DIE(dwarf::DW_TAG_formal_parameter);
        DIType ATy = DIType(DIType(Args.getElement(i)));
        addType(Arg, ATy);
        if (ATy.isArtificial())
          addUInt(Arg, dwarf::DW_AT_artificial, dwarf::DW_FORM_flag, 1);
        SPDie->addChild(Arg);
      }
    DIE *SPDeclDie = SPDie;
    SPDie = new DIE(dwarf::DW_TAG_subprogram);
    addDIEEntry(SPDie, dwarf::DW_AT_specification, dwarf::DW_FORM_ref4,
                SPDeclDie);
    SPCU->addDie(SPDie);
  }

  // Pick up abstract subprogram DIE.
  if (DIE *AbsSPDIE = AbstractSPDies.lookup(SPNode)) {
    SPDie = new DIE(dwarf::DW_TAG_subprogram);
    addDIEEntry(SPDie, dwarf::DW_AT_abstract_origin,
                dwarf::DW_FORM_ref4, AbsSPDIE);
    SPCU->addDie(SPDie);
  }

  addLabel(SPDie, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr,
           Asm->GetTempSymbol("func_begin", Asm->getFunctionNumber()));
  addLabel(SPDie, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr,
           Asm->GetTempSymbol("func_end", Asm->getFunctionNumber()));
  const TargetRegisterInfo *RI = Asm->TM.getRegisterInfo();
  MachineLocation Location(RI->getFrameRegister(*Asm->MF));
  addAddress(SPDie, dwarf::DW_AT_frame_base, Location);

  return SPDie;
}

/// constructLexicalScope - Construct new DW_TAG_lexical_block
/// for this scope and attach DW_AT_low_pc/DW_AT_high_pc labels.
DIE *DwarfDebug::constructLexicalScopeDIE(DbgScope *Scope) {

  DIE *ScopeDIE = new DIE(dwarf::DW_TAG_lexical_block);
  if (Scope->isAbstractScope())
    return ScopeDIE;

  const SmallVector<DbgRange, 4> &Ranges = Scope->getRanges();
  if (Ranges.empty())
    return 0;

  SmallVector<DbgRange, 4>::const_iterator RI = Ranges.begin();
  if (Ranges.size() > 1) {
    // .debug_range section has not been laid out yet. Emit offset in
    // .debug_range as a uint, size 4, for now. emitDIE will handle
    // DW_AT_ranges appropriately.
    addUInt(ScopeDIE, dwarf::DW_AT_ranges, dwarf::DW_FORM_data4,
            DebugRangeSymbols.size() * Asm->getTargetData().getPointerSize());
    for (SmallVector<DbgRange, 4>::const_iterator RI = Ranges.begin(),
         RE = Ranges.end(); RI != RE; ++RI) {
      DebugRangeSymbols.push_back(getLabelBeforeInsn(RI->first));
      DebugRangeSymbols.push_back(getLabelAfterInsn(RI->second));
    }
    DebugRangeSymbols.push_back(NULL);
    DebugRangeSymbols.push_back(NULL);
    return ScopeDIE;
  }

  const MCSymbol *Start = getLabelBeforeInsn(RI->first);
  const MCSymbol *End = getLabelAfterInsn(RI->second);

  if (End == 0) return 0;

  assert(Start->isDefined() && "Invalid starting label for an inlined scope!");
  assert(End->isDefined() && "Invalid end label for an inlined scope!");

  addLabel(ScopeDIE, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr, Start);
  addLabel(ScopeDIE, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr, End);

  return ScopeDIE;
}

/// constructInlinedScopeDIE - This scope represents inlined body of
/// a function. Construct DIE to represent this concrete inlined copy
/// of the function.
DIE *DwarfDebug::constructInlinedScopeDIE(DbgScope *Scope) {

  const SmallVector<DbgRange, 4> &Ranges = Scope->getRanges();
  assert (Ranges.empty() == false
          && "DbgScope does not have instruction markers!");

  // FIXME : .debug_inlined section specification does not clearly state how
  // to emit inlined scope that is split into multiple instruction ranges.
  // For now, use first instruction range and emit low_pc/high_pc pair and
  // corresponding .debug_inlined section entry for this pair.
  SmallVector<DbgRange, 4>::const_iterator RI = Ranges.begin();
  const MCSymbol *StartLabel = getLabelBeforeInsn(RI->first);
  const MCSymbol *EndLabel = getLabelAfterInsn(RI->second);

  if (StartLabel == 0 || EndLabel == 0) {
    assert (0 && "Unexpected Start and End  labels for a inlined scope!");
    return 0;
  }
  assert(StartLabel->isDefined() &&
         "Invalid starting label for an inlined scope!");
  assert(EndLabel->isDefined() &&
         "Invalid end label for an inlined scope!");

  if (!Scope->getScopeNode())
    return NULL;
  DIScope DS(Scope->getScopeNode());
  DIE *ScopeDIE = new DIE(dwarf::DW_TAG_inlined_subroutine);

  DISubprogram InlinedSP = getDISubprogram(DS);
  CompileUnit *TheCU = getCompileUnit(InlinedSP);
  DIE *OriginDIE = TheCU->getDIE(InlinedSP);
  assert(OriginDIE && "Unable to find Origin DIE!");
  addDIEEntry(ScopeDIE, dwarf::DW_AT_abstract_origin,
              dwarf::DW_FORM_ref4, OriginDIE);

  addLabel(ScopeDIE, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr, StartLabel);
  addLabel(ScopeDIE, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr, EndLabel);

  InlinedSubprogramDIEs.insert(OriginDIE);

  // Track the start label for this inlined function.
  DenseMap<const MDNode *, SmallVector<InlineInfoLabels, 4> >::iterator
    I = InlineInfo.find(InlinedSP);

  if (I == InlineInfo.end()) {
    InlineInfo[InlinedSP].push_back(std::make_pair(StartLabel,
                                                             ScopeDIE));
    InlinedSPNodes.push_back(InlinedSP);
  } else
    I->second.push_back(std::make_pair(StartLabel, ScopeDIE));

  DILocation DL(Scope->getInlinedAt());
  addUInt(ScopeDIE, dwarf::DW_AT_call_file, 0, TheCU->getID());
  addUInt(ScopeDIE, dwarf::DW_AT_call_line, 0, DL.getLineNumber());

  return ScopeDIE;
}


/// constructVariableDIE - Construct a DIE for the given DbgVariable.
DIE *DwarfDebug::constructVariableDIE(DbgVariable *DV, DbgScope *Scope) {
  StringRef Name = DV->getName();
  if (Name.empty())
    return NULL;

  // Translate tag to proper Dwarf tag.  The result variable is dropped for
  // now.
  unsigned Tag;
  switch (DV->getTag()) {
  case dwarf::DW_TAG_return_variable:
    return NULL;
  case dwarf::DW_TAG_arg_variable:
    Tag = dwarf::DW_TAG_formal_parameter;
    break;
  case dwarf::DW_TAG_auto_variable:    // fall thru
  default:
    Tag = dwarf::DW_TAG_variable;
    break;
  }

  // Define variable debug information entry.
  DIE *VariableDie = new DIE(Tag);

  DIE *AbsDIE = NULL;
  DenseMap<const DbgVariable *, const DbgVariable *>::iterator
    V2AVI = VarToAbstractVarMap.find(DV);
  if (V2AVI != VarToAbstractVarMap.end())
    AbsDIE = V2AVI->second->getDIE();

  if (AbsDIE)
    addDIEEntry(VariableDie, dwarf::DW_AT_abstract_origin,
                dwarf::DW_FORM_ref4, AbsDIE);
  else {
    addString(VariableDie, dwarf::DW_AT_name, dwarf::DW_FORM_string, Name);
    addSourceLine(VariableDie, DV->getVariable());

    // Add variable type.
    addType(VariableDie, DV->getType());
  }

  if (Tag == dwarf::DW_TAG_formal_parameter && DV->getType().isArtificial())
    addUInt(VariableDie, dwarf::DW_AT_artificial, dwarf::DW_FORM_flag, 1);
  else if (DIVariable(DV->getVariable()).isArtificial())
    addUInt(VariableDie, dwarf::DW_AT_artificial, dwarf::DW_FORM_flag, 1);

  if (Scope->isAbstractScope()) {
    DV->setDIE(VariableDie);
    return VariableDie;
  }

  // Add variable address.

  unsigned Offset = DV->getDotDebugLocOffset();
  if (Offset != ~0U) {
    addLabel(VariableDie, dwarf::DW_AT_location, dwarf::DW_FORM_data4,
             Asm->GetTempSymbol("debug_loc", Offset));
    DV->setDIE(VariableDie);
    UseDotDebugLocEntry.insert(VariableDie);
    return VariableDie;
  }

  // Check if variable is described by a  DBG_VALUE instruction.
  DenseMap<const DbgVariable *, const MachineInstr *>::iterator DVI =
    DbgVariableToDbgInstMap.find(DV);
  if (DVI != DbgVariableToDbgInstMap.end()) {
    const MachineInstr *DVInsn = DVI->second;
    const MCSymbol *DVLabel = findVariableLabel(DV);
    bool updated = false;
    // FIXME : Handle getNumOperands != 3
    if (DVInsn->getNumOperands() == 3) {
      if (DVInsn->getOperand(0).isReg()) {
        const MachineOperand RegOp = DVInsn->getOperand(0);
        const TargetRegisterInfo *TRI = Asm->TM.getRegisterInfo();
        if (DVInsn->getOperand(1).isImm() &&
            TRI->getFrameRegister(*Asm->MF) == RegOp.getReg()) {
          addVariableAddress(DV, VariableDie, DVInsn->getOperand(1).getImm());
          updated = true;
        } else
          updated = addRegisterAddress(VariableDie, DVLabel, RegOp);
      }
      else if (DVInsn->getOperand(0).isImm())
        updated = addConstantValue(VariableDie, DVLabel, DVInsn->getOperand(0));
      else if (DVInsn->getOperand(0).isFPImm())
        updated =
          addConstantFPValue(VariableDie, DVLabel, DVInsn->getOperand(0));
    } else {
      MachineLocation Location = Asm->getDebugValueLocation(DVInsn);
      if (Location.getReg()) {
        addAddress(VariableDie, dwarf::DW_AT_location, Location);
        if (DVLabel)
          addLabel(VariableDie, dwarf::DW_AT_start_scope, dwarf::DW_FORM_addr,
                   DVLabel);
        updated = true;
      }
    }
    if (!updated) {
      // If variableDie is not updated then DBG_VALUE instruction does not
      // have valid variable info.
      delete VariableDie;
      return NULL;
    }
    DV->setDIE(VariableDie);
    return VariableDie;
  }

  // .. else use frame index, if available.
  int FI = 0;
  if (findVariableFrameIndex(DV, &FI))
    addVariableAddress(DV, VariableDie, FI);
  
  DV->setDIE(VariableDie);
  return VariableDie;

}

void DwarfDebug::addPubTypes(DISubprogram SP) {
  DICompositeType SPTy = SP.getType();
  unsigned SPTag = SPTy.getTag();
  if (SPTag != dwarf::DW_TAG_subroutine_type)
    return;

  DIArray Args = SPTy.getTypeArray();
  for (unsigned i = 0, e = Args.getNumElements(); i != e; ++i) {
    DIType ATy(Args.getElement(i));
    if (!ATy.Verify())
      continue;
    DICompositeType CATy = getDICompositeType(ATy);
    if (DIDescriptor(CATy).Verify() && !CATy.getName().empty()
        && !CATy.isForwardDecl()) {
      CompileUnit *TheCU = getCompileUnit(CATy);
      if (DIEEntry *Entry = TheCU->getDIEEntry(CATy))
        TheCU->addGlobalType(CATy.getName(), Entry->getEntry());
    }
  }
}

/// constructScopeDIE - Construct a DIE for this scope.
DIE *DwarfDebug::constructScopeDIE(DbgScope *Scope) {
  if (!Scope || !Scope->getScopeNode())
    return NULL;

  DIScope DS(Scope->getScopeNode());
  DIE *ScopeDIE = NULL;
  if (Scope->getInlinedAt())
    ScopeDIE = constructInlinedScopeDIE(Scope);
  else if (DS.isSubprogram()) {
    ProcessedSPNodes.insert(DS);
    if (Scope->isAbstractScope()) {
      ScopeDIE = getCompileUnit(DS)->getDIE(DS);
      // Note down abstract DIE.
      if (ScopeDIE)
        AbstractSPDies.insert(std::make_pair(DS, ScopeDIE));
    }
    else
      ScopeDIE = updateSubprogramScopeDIE(DS);
  }
  else
    ScopeDIE = constructLexicalScopeDIE(Scope);
  if (!ScopeDIE) return NULL;

  // Add variables to scope.
  const SmallVector<DbgVariable *, 8> &Variables = Scope->getDbgVariables();
  for (unsigned i = 0, N = Variables.size(); i < N; ++i) {
    DIE *VariableDIE = constructVariableDIE(Variables[i], Scope);
    if (VariableDIE)
      ScopeDIE->addChild(VariableDIE);
  }

  // Add nested scopes.
  const SmallVector<DbgScope *, 4> &Scopes = Scope->getScopes();
  for (unsigned j = 0, M = Scopes.size(); j < M; ++j) {
    // Define the Scope debug information entry.
    DIE *NestedDIE = constructScopeDIE(Scopes[j]);
    if (NestedDIE)
      ScopeDIE->addChild(NestedDIE);
  }

  if (DS.isSubprogram())
    addPubTypes(DISubprogram(DS));

 return ScopeDIE;
}

/// GetOrCreateSourceID - Look up the source id with the given directory and
/// source file names. If none currently exists, create a new id and insert it
/// in the SourceIds map. This can update DirectoryNames and SourceFileNames
/// maps as well.
unsigned DwarfDebug::GetOrCreateSourceID(StringRef DirName, StringRef FileName){
  unsigned DId;
  assert (DirName.empty() == false && "Invalid directory name!");

  // If FE did not provide a file name, then assume stdin.
  if (FileName.empty())
    return GetOrCreateSourceID(DirName, "<stdin>");

  StringMap<unsigned>::iterator DI = DirectoryIdMap.find(DirName);
  if (DI != DirectoryIdMap.end()) {
    DId = DI->getValue();
  } else {
    DId = DirectoryNames.size() + 1;
    DirectoryIdMap[DirName] = DId;
    DirectoryNames.push_back(DirName);
  }

  unsigned FId;
  StringMap<unsigned>::iterator FI = SourceFileIdMap.find(FileName);
  if (FI != SourceFileIdMap.end()) {
    FId = FI->getValue();
  } else {
    FId = SourceFileNames.size() + 1;
    SourceFileIdMap[FileName] = FId;
    SourceFileNames.push_back(FileName);
  }

  DenseMap<std::pair<unsigned, unsigned>, unsigned>::iterator SI =
    SourceIdMap.find(std::make_pair(DId, FId));
  if (SI != SourceIdMap.end())
    return SI->second;

  unsigned SrcId = SourceIds.size() + 1;  // DW_AT_decl_file cannot be 0.
  SourceIdMap[std::make_pair(DId, FId)] = SrcId;
  SourceIds.push_back(std::make_pair(DId, FId));

  return SrcId;
}

/// getOrCreateNameSpace - Create a DIE for DINameSpace.
DIE *DwarfDebug::getOrCreateNameSpace(DINameSpace NS) {
  CompileUnit *TheCU = getCompileUnit(NS);
  DIE *NDie = TheCU->getDIE(NS);
  if (NDie)
    return NDie;
  NDie = new DIE(dwarf::DW_TAG_namespace);
  TheCU->insertDIE(NS, NDie);
  if (!NS.getName().empty())
    addString(NDie, dwarf::DW_AT_name, dwarf::DW_FORM_string, NS.getName());
  addSourceLine(NDie, NS);
  addToContextOwner(NDie, NS.getContext());
  return NDie;
}

/// constructCompileUnit - Create new CompileUnit for the given
/// metadata node with tag DW_TAG_compile_unit.
void DwarfDebug::constructCompileUnit(const MDNode *N) {
  DICompileUnit DIUnit(N);
  StringRef FN = DIUnit.getFilename();
  StringRef Dir = DIUnit.getDirectory();
  unsigned ID = GetOrCreateSourceID(Dir, FN);

  DIE *Die = new DIE(dwarf::DW_TAG_compile_unit);
  addString(Die, dwarf::DW_AT_producer, dwarf::DW_FORM_string,
            DIUnit.getProducer());
  addUInt(Die, dwarf::DW_AT_language, dwarf::DW_FORM_data1,
          DIUnit.getLanguage());
  addString(Die, dwarf::DW_AT_name, dwarf::DW_FORM_string, FN);
  // Use DW_AT_entry_pc instead of DW_AT_low_pc/DW_AT_high_pc pair. This
  // simplifies debug range entries.
  addUInt(Die, dwarf::DW_AT_entry_pc, dwarf::DW_FORM_addr, 0);
  // DW_AT_stmt_list is a offset of line number information for this
  // compile unit in debug_line section.
  if (Asm->MAI->doesDwarfUsesAbsoluteLabelForStmtList())
    addLabel(Die, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_addr,
             Asm->GetTempSymbol("section_line"));
  else
    addUInt(Die, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_data4, 0);

  if (!Dir.empty())
    addString(Die, dwarf::DW_AT_comp_dir, dwarf::DW_FORM_string, Dir);
  if (DIUnit.isOptimized())
    addUInt(Die, dwarf::DW_AT_APPLE_optimized, dwarf::DW_FORM_flag, 1);

  StringRef Flags = DIUnit.getFlags();
  if (!Flags.empty())
    addString(Die, dwarf::DW_AT_APPLE_flags, dwarf::DW_FORM_string, Flags);

  unsigned RVer = DIUnit.getRunTimeVersion();
  if (RVer)
    addUInt(Die, dwarf::DW_AT_APPLE_major_runtime_vers,
            dwarf::DW_FORM_data1, RVer);

  CompileUnit *NewCU = new CompileUnit(ID, Die);
  if (!FirstCU)
    FirstCU = NewCU;
  CUMap.insert(std::make_pair(N, NewCU));
}

/// getCompielUnit - Get CompileUnit DIE.
CompileUnit *DwarfDebug::getCompileUnit(const MDNode *N) const {
  assert (N && "Invalid DwarfDebug::getCompileUnit argument!");
  DIDescriptor D(N);
  const MDNode *CUNode = NULL;
  if (D.isCompileUnit())
    CUNode = N;
  else if (D.isSubprogram())
    CUNode = DISubprogram(N).getCompileUnit();
  else if (D.isType())
    CUNode = DIType(N).getCompileUnit();
  else if (D.isGlobalVariable())
    CUNode = DIGlobalVariable(N).getCompileUnit();
  else if (D.isVariable())
    CUNode = DIVariable(N).getCompileUnit();
  else if (D.isNameSpace())
    CUNode = DINameSpace(N).getCompileUnit();
  else if (D.isFile())
    CUNode = DIFile(N).getCompileUnit();
  else
    return FirstCU;

  DenseMap<const MDNode *, CompileUnit *>::const_iterator I
    = CUMap.find(CUNode);
  if (I == CUMap.end())
    return FirstCU;
  return I->second;
}

/// isUnsignedDIType - Return true if type encoding is unsigned.
static bool isUnsignedDIType(DIType Ty) {
  DIDerivedType DTy(Ty);
  if (DTy.Verify())
    return isUnsignedDIType(DTy.getTypeDerivedFrom());

  DIBasicType BTy(Ty);
  if (BTy.Verify()) {
    unsigned Encoding = BTy.getEncoding();
    if (Encoding == dwarf::DW_ATE_unsigned ||
        Encoding == dwarf::DW_ATE_unsigned_char)
      return true;
  }
  return false;
}

/// constructGlobalVariableDIE - Construct global variable DIE.
void DwarfDebug::constructGlobalVariableDIE(const MDNode *N) {
  DIGlobalVariable GV(N);

  // If debug information is malformed then ignore it.
  if (GV.Verify() == false)
    return;

  // Check for pre-existence.
  CompileUnit *TheCU = getCompileUnit(N);
  if (TheCU->getDIE(GV))
    return;

  DIType GTy = GV.getType();
  DIE *VariableDIE = new DIE(GV.getTag());

  bool isGlobalVariable = GV.getGlobal() != NULL;

  // Add name.
  addString(VariableDIE, dwarf::DW_AT_name, dwarf::DW_FORM_string,
            GV.getDisplayName());
  StringRef LinkageName = GV.getLinkageName();
  if (!LinkageName.empty() && isGlobalVariable)
    addString(VariableDIE, dwarf::DW_AT_MIPS_linkage_name, dwarf::DW_FORM_string,
              getRealLinkageName(LinkageName));
  // Add type.
  addType(VariableDIE, GTy);
  if (GTy.isCompositeType() && !GTy.getName().empty()
      && !GTy.isForwardDecl()) {
    DIEEntry *Entry = TheCU->getDIEEntry(GTy);
    assert(Entry && "Missing global type!");
    TheCU->addGlobalType(GTy.getName(), Entry->getEntry());
  }
  // Add scoping info.
  if (!GV.isLocalToUnit()) {
    addUInt(VariableDIE, dwarf::DW_AT_external, dwarf::DW_FORM_flag, 1);
    // Expose as global. 
    TheCU->addGlobal(GV.getName(), VariableDIE);
  }
  // Add line number info.
  addSourceLine(VariableDIE, GV);
  // Add to map.
  TheCU->insertDIE(N, VariableDIE);
  // Add to context owner.
  DIDescriptor GVContext = GV.getContext();
  addToContextOwner(VariableDIE, GVContext);
  // Add location.
  if (isGlobalVariable) {
    DIEBlock *Block = new (DIEValueAllocator) DIEBlock();
    addUInt(Block, 0, dwarf::DW_FORM_data1, dwarf::DW_OP_addr);
    addLabel(Block, 0, dwarf::DW_FORM_udata,
             Asm->Mang->getSymbol(GV.getGlobal()));
    // Do not create specification DIE if context is either compile unit
    // or a subprogram.
    if (GV.isDefinition() && !GVContext.isCompileUnit() &&
        !GVContext.isFile() && !isSubprogramContext(GVContext)) {
      // Create specification DIE.
      DIE *VariableSpecDIE = new DIE(dwarf::DW_TAG_variable);
      addDIEEntry(VariableSpecDIE, dwarf::DW_AT_specification,
                  dwarf::DW_FORM_ref4, VariableDIE);
      addBlock(VariableSpecDIE, dwarf::DW_AT_location, 0, Block);
      addUInt(VariableDIE, dwarf::DW_AT_declaration, dwarf::DW_FORM_flag, 1);
      TheCU->addDie(VariableSpecDIE);
    } else {
      addBlock(VariableDIE, dwarf::DW_AT_location, 0, Block);
    } 
  } else if (Constant *C = GV.getConstant()) {
    if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
      if (isUnsignedDIType(GTy))
          addUInt(VariableDIE, dwarf::DW_AT_const_value, dwarf::DW_FORM_udata,