llvm-project/llvm/lib/CodeGen/AsmPrinter/DwarfWriter.cpp

//===-- llvm/CodeGen/DwarfWriter.cpp - Dwarf Framework --------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing dwarf info into asm files.
//
//===----------------------------------------------------------------------===//

#include "llvm/CodeGen/DwarfWriter.h"
#include "DIE.h"
#include "DwarfException.h"
#include "DwarfPrinter.h"
#include "llvm/Module.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Constants.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineLocation.h"
#include "llvm/Analysis/DebugInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/Mangler.h"
#include "llvm/Support/Timer.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/System/Path.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringMap.h"
#include <ostream>
#include <string>
using namespace llvm;
using namespace llvm::dwarf;

static RegisterPass<DwarfWriter>
X("dwarfwriter", "DWARF Information Writer");
char DwarfWriter::ID = 0;

static TimerGroup &getDwarfTimerGroup() {
  static TimerGroup DwarfTimerGroup("Dwarf Exception and Debugging");
  return DwarfTimerGroup;
}

namespace llvm {

//===----------------------------------------------------------------------===//

/// Configuration values for initial hash set sizes (log2).
///
static const unsigned InitDiesSetSize          = 9; // log2(512)
static const unsigned InitAbbreviationsSetSize = 9; // log2(512)
static const unsigned InitValuesSetSize        = 9; // log2(512)

//===----------------------------------------------------------------------===//
/// CompileUnit - This dwarf writer support class manages information associate
/// with a source file.
class VISIBILITY_HIDDEN CompileUnit {
  /// ID - File identifier for source.
  ///
  unsigned ID;

  /// Die - Compile unit debug information entry.
  ///
  DIE *Die;

  /// GVToDieMap - Tracks the mapping of unit level debug informaton
  /// variables to debug information entries.
  std::map<GlobalVariable *, DIE *> GVToDieMap;

  /// GVToDIEEntryMap - Tracks the mapping of unit level debug informaton
  /// descriptors to debug information entries using a DIEEntry proxy.
  std::map<GlobalVariable *, DIEEntry *> GVToDIEEntryMap;

  /// Globals - A map of globally visible named entities for this unit.
  ///
  StringMap<DIE*> Globals;

  /// DiesSet - Used to uniquely define dies within the compile unit.
  ///
  FoldingSet<DIE> DiesSet;
public:
  CompileUnit(unsigned I, DIE *D)
    : ID(I), Die(D), GVToDieMap(),
      GVToDIEEntryMap(), Globals(), DiesSet(InitDiesSetSize)
  {}

  ~CompileUnit() {
    delete Die;
  }

  // Accessors.
  unsigned getID()           const { return ID; }
  DIE* getDie()              const { return Die; }
  StringMap<DIE*> &getGlobals() { return Globals; }

  /// hasContent - Return true if this compile unit has something to write out.
  ///
  bool hasContent() const {
    return !Die->getChildren().empty();
  }

  /// AddGlobal - Add a new global entity to the compile unit.
  ///
  void AddGlobal(const std::string &Name, DIE *Die) {
    Globals[Name] = Die;
  }

  /// getDieMapSlotFor - Returns the debug information entry map slot for the
  /// specified debug variable.
  DIE *&getDieMapSlotFor(GlobalVariable *GV) {
    return GVToDieMap[GV];
  }

  /// getDIEEntrySlotFor - Returns the debug information entry proxy slot for the
  /// specified debug variable.
  DIEEntry *&getDIEEntrySlotFor(GlobalVariable *GV) {
    return GVToDIEEntryMap[GV];
  }

  /// AddDie - Adds or interns the DIE to the compile unit.
  ///
  DIE *AddDie(DIE &Buffer) {
    FoldingSetNodeID ID;
    Buffer.Profile(ID);
    void *Where;
    DIE *Die = DiesSet.FindNodeOrInsertPos(ID, Where);

    if (!Die) {
      Die = new DIE(Buffer);
      DiesSet.InsertNode(Die, Where);
      this->Die->AddChild(Die);
      Buffer.Detach();
    }

    return Die;
  }
};

//===----------------------------------------------------------------------===//
/// SrcLineInfo - This class is used to record source line correspondence.
///
class VISIBILITY_HIDDEN SrcLineInfo {
  unsigned Line;                     // Source line number.
  unsigned Column;                   // Source column.
  unsigned SourceID;                 // Source ID number.
  unsigned LabelID;                  // Label in code ID number.
public:
  SrcLineInfo(unsigned L, unsigned C, unsigned S, unsigned I)
    : Line(L), Column(C), SourceID(S), LabelID(I) {}

  // Accessors
  unsigned getLine()     const { return Line; }
  unsigned getColumn()   const { return Column; }
  unsigned getSourceID() const { return SourceID; }
  unsigned getLabelID()  const { return LabelID; }
};

//===----------------------------------------------------------------------===//
/// DbgVariable - This class is used to track local variable information.
///
class VISIBILITY_HIDDEN DbgVariable {
  DIVariable Var;                    // Variable Descriptor.
  unsigned FrameIndex;               // Variable frame index.
public:
  DbgVariable(DIVariable V, unsigned I) : Var(V), FrameIndex(I)  {}
  
  // Accessors.
  DIVariable getVariable()  const { return Var; }
  unsigned getFrameIndex() const { return FrameIndex; }
};

//===----------------------------------------------------------------------===//
/// DbgScope - This class is used to track scope information.
///
class DbgConcreteScope;
class VISIBILITY_HIDDEN DbgScope {
  DbgScope *Parent;                   // Parent to this scope.
  DIDescriptor Desc;                  // Debug info descriptor for scope.
                                      // Either subprogram or block.
  unsigned StartLabelID;              // Label ID of the beginning of scope.
  unsigned EndLabelID;                // Label ID of the end of scope.
  SmallVector<DbgScope *, 4> Scopes;  // Scopes defined in scope.
  SmallVector<DbgVariable *, 8> Variables;// Variables declared in scope.
  SmallVector<DbgConcreteScope *, 8> ConcreteInsts;// Concrete insts of funcs.
public:
  DbgScope(DbgScope *P, DIDescriptor D)
    : Parent(P), Desc(D), StartLabelID(0), EndLabelID(0) {}
  virtual ~DbgScope();
  
  // Accessors.
  DbgScope *getParent()          const { return Parent; }
  DIDescriptor getDesc()         const { return Desc; }
  unsigned getStartLabelID()     const { return StartLabelID; }
  unsigned getEndLabelID()       const { return EndLabelID; }
  SmallVector<DbgScope *, 4> &getScopes() { return Scopes; }
  SmallVector<DbgVariable *, 8> &getVariables() { return Variables; }
  SmallVector<DbgConcreteScope*,8> &getConcreteInsts() { return ConcreteInsts; }
  void setStartLabelID(unsigned S) { StartLabelID = S; }
  void setEndLabelID(unsigned E)   { EndLabelID = E; }
  
  /// AddScope - Add a scope to the scope.
  ///
  void AddScope(DbgScope *S) { Scopes.push_back(S); }
  
  /// AddVariable - Add a variable to the scope.
  ///
  void AddVariable(DbgVariable *V) { Variables.push_back(V); }

  /// AddConcreteInst - Add a concrete instance to the scope.
  ///
  void AddConcreteInst(DbgConcreteScope *C) { ConcreteInsts.push_back(C); }

#ifndef NDEBUG
  void dump() const;
#endif
};

#ifndef NDEBUG
void DbgScope::dump() const {
  static unsigned IndentLevel = 0;
  std::string Indent(IndentLevel, ' ');

  cerr << Indent; Desc.dump();
  cerr << " [" << StartLabelID << ", " << EndLabelID << "]\n";

  IndentLevel += 2;

  for (unsigned i = 0, e = Scopes.size(); i != e; ++i)
    if (Scopes[i] != this)
      Scopes[i]->dump();

  IndentLevel -= 2;
}
#endif

//===----------------------------------------------------------------------===//
/// DbgConcreteScope - This class is used to track a scope that holds concrete
/// instance information.
/// 
class VISIBILITY_HIDDEN DbgConcreteScope : public DbgScope {
  CompileUnit *Unit;
  DIE *Die;                           // Debug info for this concrete scope.
public:
  DbgConcreteScope(DIDescriptor D) : DbgScope(NULL, D) {}

  // Accessors.
  DIE *getDie() const { return Die; }
  void setDie(DIE *D) { Die = D; }
};

DbgScope::~DbgScope() {
  for (unsigned i = 0, N = Scopes.size(); i < N; ++i)
    delete Scopes[i];
  for (unsigned j = 0, M = Variables.size(); j < M; ++j)
    delete Variables[j];
  for (unsigned k = 0, O = ConcreteInsts.size(); k < O; ++k)
    delete ConcreteInsts[k];
}

//===----------------------------------------------------------------------===//
/// DwarfDebug - Emits Dwarf debug directives.
///
class VISIBILITY_HIDDEN DwarfDebug : public Dwarf {
  //===--------------------------------------------------------------------===//
  // Attributes used to construct specific Dwarf sections.
  //

  /// CompileUnitMap - A map of global variables representing compile units to
  /// compile units.
  DenseMap<Value *, CompileUnit *> CompileUnitMap;

  /// CompileUnits - All the compile units in this module.
  ///
  SmallVector<CompileUnit *, 8> CompileUnits;

  /// 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;

  /// Abbreviations - A list of all the unique abbreviations in use.
  ///
  std::vector<DIEAbbrev *> Abbreviations;

  /// DirectoryIdMap - Directory name to directory id map.
  ///
  StringMap<unsigned> DirectoryIdMap;

  /// DirectoryNames - A list of directory names.
  SmallVector<std::string, 8> DirectoryNames;

  /// SourceFileIdMap - Source file name to source file id map.
  ///
  StringMap<unsigned> SourceFileIdMap;

  /// SourceFileNames - A list of source file names.
  SmallVector<std::string, 8> SourceFileNames;

  /// SourceIdMap - Source id map, i.e. pair of directory id and source file
  /// id mapped to a unique id.
  DenseMap<std::pair<unsigned, unsigned>, unsigned> SourceIdMap;

  /// SourceIds - Reverse map from source id to directory id + file id pair.
  ///
  SmallVector<std::pair<unsigned, unsigned>, 8> SourceIds;

  /// Lines - List of of source line correspondence.
  std::vector<SrcLineInfo> Lines;

  /// ValuesSet - Used to uniquely define values.
  ///
  FoldingSet<DIEValue> ValuesSet;

  /// Values - A list of all the unique values in use.
  ///
  std::vector<DIEValue *> Values;

  /// StringPool - A UniqueVector of strings used by indirect references.
  ///
  UniqueVector<std::string> StringPool;

  /// SectionMap - Provides a unique id per text section.
  ///
  UniqueVector<const Section*> SectionMap;

  /// SectionSourceLines - Tracks line numbers per text section.
  ///
  std::vector<std::vector<SrcLineInfo> > SectionSourceLines;

  /// didInitial - Flag to indicate if initial emission has been done.
  ///
  bool didInitial;

  /// shouldEmit - Flag to indicate if debug information should be emitted.
  ///
  bool shouldEmit;

  // FunctionDbgScope - Top level scope for the current function.
  //
  DbgScope *FunctionDbgScope;
  
  /// DbgScopeMap - Tracks the scopes in the current function.
  DenseMap<GlobalVariable *, DbgScope *> DbgScopeMap;

  /// DbgAbstractScopeMap - Tracks abstract instance scopes in the current
  /// function.
  DenseMap<GlobalVariable *, DbgScope *> DbgAbstractScopeMap;

  /// DbgConcreteScopeMap - Tracks concrete instance scopes in the current
  /// function.
  DenseMap<GlobalVariable *,
           SmallVector<DbgScope *, 8> > DbgConcreteScopeMap;

  /// InlineInfo - Keep track of inlined functions and their location.  This
  /// information is used to populate debug_inlined section.
  DenseMap<GlobalVariable *, SmallVector<unsigned, 4> > InlineInfo;

  /// InlinedVariableScopes - Scopes information for the inlined subroutine
  /// variables.
  DenseMap<const MachineInstr *, DbgScope *> InlinedVariableScopes;

  /// AbstractInstanceRootMap - Map of abstract instance roots of inlined
  /// functions. These are subroutine entries that contain a DW_AT_inline
  /// attribute.
  DenseMap<const GlobalVariable *, DbgScope *> AbstractInstanceRootMap;

  /// AbstractInstanceRootList - List of abstract instance roots of inlined
  /// functions. These are subroutine entries that contain a DW_AT_inline
  /// attribute.
  SmallVector<DbgScope *, 32> AbstractInstanceRootList;

  /// LexicalScopeStack - A stack of lexical scopes. The top one is the current
  /// scope.
  SmallVector<DbgScope *, 16> LexicalScopeStack;

  /// CompileUnitOffsets - A vector of the offsets of the compile units. This is
  /// used when calculating the "origin" of a concrete instance of an inlined
  /// function.
  DenseMap<CompileUnit *, unsigned> CompileUnitOffsets;

  /// DebugTimer - Timer for the Dwarf debug writer.
  Timer *DebugTimer;
  
  struct FunctionDebugFrameInfo {
    unsigned Number;
    std::vector<MachineMove> Moves;

    FunctionDebugFrameInfo(unsigned Num, const std::vector<MachineMove> &M):
      Number(Num), Moves(M) { }
  };

  std::vector<FunctionDebugFrameInfo> DebugFrames;

private:
  /// getSourceDirectoryAndFileIds - Return the directory and file ids that
  /// maps to the source id. Source id starts at 1.
  std::pair<unsigned, unsigned>
  getSourceDirectoryAndFileIds(unsigned SId) const {
    return SourceIds[SId-1];
  }

  /// getNumSourceDirectories - Return the number of source directories in the
  /// debug info.
  unsigned getNumSourceDirectories() const {
    return DirectoryNames.size();
  }

  /// getSourceDirectoryName - Return the name of the directory corresponding
  /// to the id.
  const std::string &getSourceDirectoryName(unsigned Id) const {
    return DirectoryNames[Id - 1];
  }

  /// getSourceFileName - Return the name of the source file corresponding
  /// to the id.
  const std::string &getSourceFileName(unsigned Id) const {
    return SourceFileNames[Id - 1];
  }

  /// getNumSourceIds - Return the number of unique source ids.
  unsigned getNumSourceIds() const {
    return SourceIds.size();
  }

  /// AssignAbbrevNumber - Define a unique number for the abbreviation.
  ///
  void AssignAbbrevNumber(DIEAbbrev &Abbrev) {
    // Profile the node so that we can make it unique.
    FoldingSetNodeID ID;
    Abbrev.Profile(ID);

    // Check the set for priors.
    DIEAbbrev *InSet = AbbreviationsSet.GetOrInsertNode(&Abbrev);

    // If it's newly added.
    if (InSet == &Abbrev) {
      // Add to abbreviation list.
      Abbreviations.push_back(&Abbrev);
      // Assign the vector position + 1 as its number.
      Abbrev.setNumber(Abbreviations.size());
    } else {
      // Assign existing abbreviation number.
      Abbrev.setNumber(InSet->getNumber());
    }
  }

  /// NewString - Add a string to the constant pool and returns a label.
  ///
  DWLabel NewString(const std::string &String) {
    unsigned StringID = StringPool.insert(String);
    return DWLabel("string", StringID);
  }

  /// NewDIEEntry - Creates a new DIEEntry to be a proxy for a debug information
  /// entry.
  DIEEntry *NewDIEEntry(DIE *Entry = NULL) {
    DIEEntry *Value;

    if (Entry) {
      FoldingSetNodeID ID;
      DIEEntry::Profile(ID, Entry);
      void *Where;
      Value = static_cast<DIEEntry *>(ValuesSet.FindNodeOrInsertPos(ID, Where));

      if (Value) return Value;

      Value = new DIEEntry(Entry);
      ValuesSet.InsertNode(Value, Where);
    } else {
      Value = new DIEEntry(Entry);
    }

    Values.push_back(Value);
    return Value;
  }

  /// SetDIEEntry - Set a DIEEntry once the debug information entry is defined.
  ///
  void SetDIEEntry(DIEEntry *Value, DIE *Entry) {
    Value->setEntry(Entry);
    // Add to values set if not already there.  If it is, we merely have a
    // duplicate in the values list (no harm.)
    ValuesSet.GetOrInsertNode(Value);
  }

  /// AddUInt - Add an unsigned integer attribute data and value.
  ///
  void AddUInt(DIE *Die, unsigned Attribute, unsigned Form, uint64_t Integer) {
    if (!Form) Form = DIEInteger::BestForm(false, Integer);

    FoldingSetNodeID ID;
    DIEInteger::Profile(ID, Integer);
    void *Where;
    DIEValue *Value = ValuesSet.FindNodeOrInsertPos(ID, Where);
    if (!Value) {
      Value = new DIEInteger(Integer);
      ValuesSet.InsertNode(Value, Where);
      Values.push_back(Value);
    }

    Die->AddValue(Attribute, Form, Value);
  }

  /// AddSInt - Add an signed integer attribute data and value.
  ///
  void AddSInt(DIE *Die, unsigned Attribute, unsigned Form, int64_t Integer) {
    if (!Form) Form = DIEInteger::BestForm(true, Integer);

    FoldingSetNodeID ID;
    DIEInteger::Profile(ID, (uint64_t)Integer);
    void *Where;
    DIEValue *Value = ValuesSet.FindNodeOrInsertPos(ID, Where);
    if (!Value) {
      Value = new DIEInteger(Integer);
      ValuesSet.InsertNode(Value, Where);
      Values.push_back(Value);
    }

    Die->AddValue(Attribute, Form, Value);
  }

  /// AddString - Add a string attribute data and value.
  ///
  void AddString(DIE *Die, unsigned Attribute, unsigned Form,
                 const std::string &String) {
    FoldingSetNodeID ID;
    DIEString::Profile(ID, String);
    void *Where;
    DIEValue *Value = ValuesSet.FindNodeOrInsertPos(ID, Where);
    if (!Value) {
      Value = new DIEString(String);
      ValuesSet.InsertNode(Value, Where);
      Values.push_back(Value);
    }

    Die->AddValue(Attribute, Form, Value);
  }

  /// AddLabel - Add a Dwarf label attribute data and value.
  ///
  void AddLabel(DIE *Die, unsigned Attribute, unsigned Form,
                const DWLabel &Label) {
    FoldingSetNodeID ID;
    DIEDwarfLabel::Profile(ID, Label);
    void *Where;
    DIEValue *Value = ValuesSet.FindNodeOrInsertPos(ID, Where);
    if (!Value) {
      Value = new DIEDwarfLabel(Label);
      ValuesSet.InsertNode(Value, Where);
      Values.push_back(Value);
    }

    Die->AddValue(Attribute, Form, Value);
  }

  /// AddObjectLabel - Add an non-Dwarf label attribute data and value.
  ///
  void AddObjectLabel(DIE *Die, unsigned Attribute, unsigned Form,
                      const std::string &Label) {
    FoldingSetNodeID ID;
    DIEObjectLabel::Profile(ID, Label);
    void *Where;
    DIEValue *Value = ValuesSet.FindNodeOrInsertPos(ID, Where);
    if (!Value) {
      Value = new DIEObjectLabel(Label);
      ValuesSet.InsertNode(Value, Where);
      Values.push_back(Value);
    }

    Die->AddValue(Attribute, Form, Value);
  }

  /// AddSectionOffset - Add a section offset label attribute data and value.
  ///
  void AddSectionOffset(DIE *Die, unsigned Attribute, unsigned Form,
                        const DWLabel &Label, const DWLabel &Section,
                        bool isEH = false, bool useSet = true) {
    FoldingSetNodeID ID;
    DIESectionOffset::Profile(ID, Label, Section);
    void *Where;
    DIEValue *Value = ValuesSet.FindNodeOrInsertPos(ID, Where);
    if (!Value) {
      Value = new DIESectionOffset(Label, Section, isEH, useSet);
      ValuesSet.InsertNode(Value, Where);
      Values.push_back(Value);
    }

    Die->AddValue(Attribute, Form, Value);
  }

  /// AddDelta - Add a label delta attribute data and value.
  ///
  void AddDelta(DIE *Die, unsigned Attribute, unsigned Form,
                const DWLabel &Hi, const DWLabel &Lo) {
    FoldingSetNodeID ID;
    DIEDelta::Profile(ID, Hi, Lo);
    void *Where;
    DIEValue *Value = ValuesSet.FindNodeOrInsertPos(ID, Where);
    if (!Value) {
      Value = new DIEDelta(Hi, Lo);
      ValuesSet.InsertNode(Value, Where);
      Values.push_back(Value);
    }

    Die->AddValue(Attribute, Form, Value);
  }

  /// AddDIEEntry - Add a DIE attribute data and value.
  ///
  void AddDIEEntry(DIE *Die, unsigned Attribute, unsigned Form, DIE *Entry) {
    Die->AddValue(Attribute, Form, NewDIEEntry(Entry));
  }

  /// AddBlock - Add block data.
  ///
  void AddBlock(DIE *Die, unsigned Attribute, unsigned Form, DIEBlock *Block) {
    Block->ComputeSize(TD);
    FoldingSetNodeID ID;
    Block->Profile(ID);
    void *Where;
    DIEValue *Value = ValuesSet.FindNodeOrInsertPos(ID, Where);
    if (!Value) {
      Value = Block;
      ValuesSet.InsertNode(Value, Where);
      Values.push_back(Value);
    } else {
      // Already exists, reuse the previous one.
      delete Block;
      Block = cast<DIEBlock>(Value);
    }

    Die->AddValue(Attribute, Block->BestForm(), Value);
  }

  /// AddSourceLine - Add location information to specified debug information
  /// entry.
  void AddSourceLine(DIE *Die, const DIVariable *V) {
    // If there is no compile unit specified, don't add a line #.
    if (V->getCompileUnit().isNull())
      return;

    unsigned Line = V->getLineNumber();
    unsigned FileID = FindCompileUnit(V->getCompileUnit()).getID();
    assert(FileID && "Invalid file id");
    AddUInt(Die, DW_AT_decl_file, 0, FileID);
    AddUInt(Die, DW_AT_decl_line, 0, Line);
  }

  /// AddSourceLine - Add location information to specified debug information
  /// entry.
  void AddSourceLine(DIE *Die, const DIGlobal *G) {
    // If there is no compile unit specified, don't add a line #.
    if (G->getCompileUnit().isNull())
      return;
    unsigned Line = G->getLineNumber();
    unsigned FileID = FindCompileUnit(G->getCompileUnit()).getID();
    assert(FileID && "Invalid file id");
    AddUInt(Die, DW_AT_decl_file, 0, FileID);
    AddUInt(Die, DW_AT_decl_line, 0, Line);
  }

  void AddSourceLine(DIE *Die, const DIType *Ty) {
    // If there is no compile unit specified, don't add a line #.
    DICompileUnit CU = Ty->getCompileUnit();
    if (CU.isNull())
      return;
    
    unsigned Line = Ty->getLineNumber();
    unsigned FileID = FindCompileUnit(CU).getID();
    assert(FileID && "Invalid file id");
    AddUInt(Die, DW_AT_decl_file, 0, FileID);
    AddUInt(Die, DW_AT_decl_line, 0, Line);
  }

  /// AddAddress - Add an address attribute to a die based on the location
  /// provided.
  void AddAddress(DIE *Die, unsigned Attribute,
                  const MachineLocation &Location) {
    unsigned Reg = RI->getDwarfRegNum(Location.getReg(), false);
    DIEBlock *Block = new DIEBlock();

    if (Location.isReg()) {
      if (Reg < 32) {
        AddUInt(Block, 0, DW_FORM_data1, DW_OP_reg0 + Reg);
      } else {
        AddUInt(Block, 0, DW_FORM_data1, DW_OP_regx);
        AddUInt(Block, 0, DW_FORM_udata, Reg);
      }
    } else {
      if (Reg < 32) {
        AddUInt(Block, 0, DW_FORM_data1, DW_OP_breg0 + Reg);
      } else {
        AddUInt(Block, 0, DW_FORM_data1, DW_OP_bregx);
        AddUInt(Block, 0, DW_FORM_udata, Reg);
      }
      AddUInt(Block, 0, DW_FORM_sdata, Location.getOffset());
    }

    AddBlock(Die, Attribute, 0, Block);
  }

  /// AddType - Add a new type attribute to the specified entity.
  void AddType(CompileUnit *DW_Unit, DIE *Entity, DIType Ty) {
    if (Ty.isNull())
      return;

    // Check for pre-existence.
    DIEEntry *&Slot = DW_Unit->getDIEEntrySlotFor(Ty.getGV());
    // If it exists then use the existing value.
    if (Slot) {
      Entity->AddValue(DW_AT_type, DW_FORM_ref4, Slot);
      return;
    }

    // Set up proxy. 
    Slot = NewDIEEntry();

    // Construct type.
    DIE Buffer(DW_TAG_base_type);
    if (Ty.isBasicType(Ty.getTag()))
      ConstructTypeDIE(DW_Unit, Buffer, DIBasicType(Ty.getGV()));
    else if (Ty.isDerivedType(Ty.getTag()))
      ConstructTypeDIE(DW_Unit, Buffer, DIDerivedType(Ty.getGV()));
    else {
      assert(Ty.isCompositeType(Ty.getTag()) && "Unknown kind of DIType");
      ConstructTypeDIE(DW_Unit, Buffer, DICompositeType(Ty.getGV()));
    }
    
    // Add debug information entry to entity and appropriate context.
    DIE *Die = NULL;
    DIDescriptor Context = Ty.getContext();
    if (!Context.isNull())
      Die = DW_Unit->getDieMapSlotFor(Context.getGV());

    if (Die) {
      DIE *Child = new DIE(Buffer);
      Die->AddChild(Child);
      Buffer.Detach();
      SetDIEEntry(Slot, Child);
    } else {
      Die = DW_Unit->AddDie(Buffer);
      SetDIEEntry(Slot, Die);
    }

    Entity->AddValue(DW_AT_type, DW_FORM_ref4, Slot);
  }

  /// ConstructTypeDIE - Construct basic type die from DIBasicType.
  void ConstructTypeDIE(CompileUnit *DW_Unit, DIE &Buffer,
                        DIBasicType BTy) {
    
    // Get core information.
    std::string Name;
    BTy.getName(Name);
    Buffer.setTag(DW_TAG_base_type);
    AddUInt(&Buffer, DW_AT_encoding,  DW_FORM_data1, BTy.getEncoding());
    // Add name if not anonymous or intermediate type.
    if (!Name.empty())
      AddString(&Buffer, DW_AT_name, DW_FORM_string, Name);
    uint64_t Size = BTy.getSizeInBits() >> 3;
    AddUInt(&Buffer, DW_AT_byte_size, 0, Size);
  }

  /// ConstructTypeDIE - Construct derived type die from DIDerivedType.
  void ConstructTypeDIE(CompileUnit *DW_Unit, DIE &Buffer,
                        DIDerivedType DTy) {

    // Get core information.
    std::string Name;
    DTy.getName(Name);
    uint64_t Size = DTy.getSizeInBits() >> 3;
    unsigned Tag = DTy.getTag();

    // FIXME - Workaround for templates.
    if (Tag == DW_TAG_inheritance) Tag = DW_TAG_reference_type;

    Buffer.setTag(Tag);

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

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

    // Add size if non-zero (derived types might be zero-sized.)
    if (Size)
      AddUInt(&Buffer, 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 ConstructTypeDIE(CompileUnit *DW_Unit, DIE &Buffer,
                        DICompositeType CTy) {
    // Get core information.
    std::string Name;
    CTy.getName(Name);

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

    switch (Tag) {
    case DW_TAG_vector_type:
    case DW_TAG_array_type:
      ConstructArrayTypeDIE(DW_Unit, Buffer, &CTy);
      break;
    case 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;
          DIEnumerator Enum(Elements.getElement(i).getGV());
          ElemDie = ConstructEnumTypeDIE(DW_Unit, &Enum);
          Buffer.AddChild(ElemDie);
        }
      }
      break;
    case DW_TAG_subroutine_type: 
      {
        // Add return type.
        DIArray Elements = CTy.getTypeArray();
        DIDescriptor RTy = Elements.getElement(0);
        AddType(DW_Unit, &Buffer, DIType(RTy.getGV()));

        // Add prototype flag.
        AddUInt(&Buffer, DW_AT_prototyped, DW_FORM_flag, 1);

        // Add arguments.
        for (unsigned i = 1, N = Elements.getNumElements(); i < N; ++i) {
          DIE *Arg = new DIE(DW_TAG_formal_parameter);
          DIDescriptor Ty = Elements.getElement(i);
          AddType(DW_Unit, Arg, DIType(Ty.getGV()));
          Buffer.AddChild(Arg);
        }
      }
      break;
    case DW_TAG_structure_type:
    case DW_TAG_union_type: 
    case DW_TAG_class_type:
      {
        // Add elements to structure type.
        DIArray Elements = CTy.getTypeArray();

        // A forward struct declared type may not have elements available.
        if (Elements.isNull())
          break;

        // Add elements to structure type.
        for (unsigned i = 0, N = Elements.getNumElements(); i < N; ++i) {
          DIDescriptor Element = Elements.getElement(i);
          DIE *ElemDie = NULL;
          if (Element.getTag() == dwarf::DW_TAG_subprogram)
            ElemDie = CreateSubprogramDIE(DW_Unit, 
                                          DISubprogram(Element.getGV()));
          else if (Element.getTag() == dwarf::DW_TAG_variable) // ??
            ElemDie = CreateGlobalVariableDIE(DW_Unit, 
                                              DIGlobalVariable(Element.getGV()));
          else
            ElemDie = CreateMemberDIE(DW_Unit, 
                                      DIDerivedType(Element.getGV()));
          Buffer.AddChild(ElemDie);
        }

        // FIXME: We'd like an API to register additional attributes for the
        // frontend to use while synthesizing, and then we'd use that api in
        // clang instead of this.
        if (Name == "__block_literal_generic")
          AddUInt(&Buffer, DW_AT_APPLE_block, DW_FORM_flag, 1);

        unsigned RLang = CTy.getRunTimeLang();
        if (RLang) 
          AddUInt(&Buffer, DW_AT_APPLE_runtime_class, DW_FORM_data1, RLang);
      }
      break;
    default:
      break;
    }

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

    if (Tag == DW_TAG_enumeration_type || Tag == DW_TAG_structure_type
        || Tag == DW_TAG_union_type) {
      // Add size if non-zero (derived types might be zero-sized.)
      if (Size)
        AddUInt(&Buffer, DW_AT_byte_size, 0, Size);
      else {
        // Add zero size if it is not a forward declaration.
        if (CTy.isForwardDecl())
          AddUInt(&Buffer, DW_AT_declaration, DW_FORM_flag, 1);
        else
          AddUInt(&Buffer, 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 ConstructSubrangeDIE(DIE &Buffer, DISubrange SR, DIE *IndexTy) {
    int64_t L = SR.getLo();
    int64_t H = SR.getHi();
    DIE *DW_Subrange = new DIE(DW_TAG_subrange_type);
    if (L != H) {
      AddDIEEntry(DW_Subrange, DW_AT_type, DW_FORM_ref4, IndexTy);
      if (L)
        AddSInt(DW_Subrange, DW_AT_lower_bound, 0, L);
      AddSInt(DW_Subrange, DW_AT_upper_bound, 0, H);
    }
    Buffer.AddChild(DW_Subrange);
  }

  /// ConstructArrayTypeDIE - Construct array type DIE from DICompositeType.
  void ConstructArrayTypeDIE(CompileUnit *DW_Unit, DIE &Buffer, 
                             DICompositeType *CTy) {
    Buffer.setTag(DW_TAG_array_type);
    if (CTy->getTag() == DW_TAG_vector_type)
      AddUInt(&Buffer, DW_AT_GNU_vector, DW_FORM_flag, 1);
    
    // Emit derived type.
    AddType(DW_Unit, &Buffer, CTy->getTypeDerivedFrom());    
    DIArray Elements = CTy->getTypeArray();

    // Construct an anonymous type for index type.
    DIE IdxBuffer(DW_TAG_base_type);
    AddUInt(&IdxBuffer, DW_AT_byte_size, 0, sizeof(int32_t));
    AddUInt(&IdxBuffer, DW_AT_encoding, DW_FORM_data1, DW_ATE_signed);
    DIE *IndexTy = DW_Unit->AddDie(IdxBuffer);

    // 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.getGV()), IndexTy);
    }
  }

  /// ConstructEnumTypeDIE - Construct enum type DIE from DIEnumerator.
  DIE *ConstructEnumTypeDIE(CompileUnit *DW_Unit, DIEnumerator *ETy) {

    DIE *Enumerator = new DIE(DW_TAG_enumerator);
    std::string Name;
    ETy->getName(Name);
    AddString(Enumerator, DW_AT_name, DW_FORM_string, Name);
    int64_t Value = ETy->getEnumValue();                             
    AddSInt(Enumerator, DW_AT_const_value, DW_FORM_sdata, Value);
    return Enumerator;
  }

  /// CreateGlobalVariableDIE - Create new DIE using GV.
  DIE *CreateGlobalVariableDIE(CompileUnit *DW_Unit, const DIGlobalVariable &GV)
  {
    DIE *GVDie = new DIE(DW_TAG_variable);
    std::string Name;
    GV.getDisplayName(Name);
    AddString(GVDie, DW_AT_name, DW_FORM_string, Name);
    std::string LinkageName;
    GV.getLinkageName(LinkageName);
    if (!LinkageName.empty())
      AddString(GVDie, DW_AT_MIPS_linkage_name, DW_FORM_string, LinkageName);
    AddType(DW_Unit, GVDie, GV.getType());
    if (!GV.isLocalToUnit())
      AddUInt(GVDie, DW_AT_external, DW_FORM_flag, 1);
    AddSourceLine(GVDie, &GV);
    return GVDie;
  }

  /// CreateMemberDIE - Create new member DIE.
  DIE *CreateMemberDIE(CompileUnit *DW_Unit, const DIDerivedType &DT) {
    DIE *MemberDie = new DIE(DT.getTag());
    std::string Name;
    DT.getName(Name);
    if (!Name.empty())
      AddString(MemberDie, DW_AT_name, DW_FORM_string, Name);

    AddType(DW_Unit, MemberDie, DT.getTypeDerivedFrom());

    AddSourceLine(MemberDie, &DT);

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

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

      uint64_t Offset = DT.getOffsetInBits();
      uint64_t FieldOffset = Offset;
      uint64_t AlignMask = ~(DT.getAlignInBits() - 1);
      uint64_t HiMark = (Offset + FieldSize) & AlignMask;
      FieldOffset = (HiMark - FieldSize);
      Offset -= FieldOffset;
      // Maybe we need to work from the other end.
      if (TD->isLittleEndian()) Offset = FieldSize - (Offset + Size);
      AddUInt(MemberDie, DW_AT_bit_offset, 0, Offset);
    }
    DIEBlock *Block = new DIEBlock();
    AddUInt(Block, 0, DW_FORM_data1, DW_OP_plus_uconst);
    AddUInt(Block, 0, DW_FORM_udata, DT.getOffsetInBits() >> 3);
    AddBlock(MemberDie, DW_AT_data_member_location, 0, Block);

    if (DT.isProtected())
      AddUInt(MemberDie, DW_AT_accessibility, 0, DW_ACCESS_protected);
    else if (DT.isPrivate())
      AddUInt(MemberDie, DW_AT_accessibility, 0, DW_ACCESS_private);

    return MemberDie;
  }

  /// CreateSubprogramDIE - Create new DIE using SP.
  DIE *CreateSubprogramDIE(CompileUnit *DW_Unit,
                           const DISubprogram &SP,
                           bool IsConstructor = false) {
    DIE *SPDie = new DIE(DW_TAG_subprogram);

    std::string Name;
    SP.getName(Name);
    AddString(SPDie, DW_AT_name, DW_FORM_string, Name);

    std::string LinkageName;
    SP.getLinkageName(LinkageName);

    if (!LinkageName.empty())
      AddString(SPDie, DW_AT_MIPS_linkage_name, DW_FORM_string, LinkageName);

    AddSourceLine(SPDie, &SP);

    DICompositeType SPTy = SP.getType();
    DIArray Args = SPTy.getTypeArray();

    // Add prototyped tag, if C or ObjC.
    unsigned Lang = SP.getCompileUnit().getLanguage();
    if (Lang == DW_LANG_C99 || Lang == DW_LANG_C89 || Lang == DW_LANG_ObjC)
      AddUInt(SPDie, DW_AT_prototyped, DW_FORM_flag, 1);
    
    // Add Return Type.
    unsigned SPTag = SPTy.getTag();
    if (!IsConstructor) {
      if (Args.isNull() || SPTag != DW_TAG_subroutine_type)
        AddType(DW_Unit, SPDie, SPTy);
      else
        AddType(DW_Unit, SPDie, DIType(Args.getElement(0).getGV()));
    }

    if (!SP.isDefinition()) {
      AddUInt(SPDie, DW_AT_declaration, DW_FORM_flag, 1);    
      // Add arguments. Do not add arguments for subprogram definition. They
      // will be handled through RecordVariable.
      if (SPTag == DW_TAG_subroutine_type)
        for (unsigned i = 1, N =  Args.getNumElements(); i < N; ++i) {
          DIE *Arg = new DIE(DW_TAG_formal_parameter);
          AddType(DW_Unit, Arg, DIType(Args.getElement(i).getGV()));
          AddUInt(Arg, DW_AT_artificial, DW_FORM_flag, 1); // ??
          SPDie->AddChild(Arg);
        }
    }

    if (!SP.isLocalToUnit())
      AddUInt(SPDie, DW_AT_external, DW_FORM_flag, 1);

    // DW_TAG_inlined_subroutine may refer to this DIE.
    DIE *&Slot = DW_Unit->getDieMapSlotFor(SP.getGV());
    Slot = SPDie;
    return SPDie;
  }

  /// FindCompileUnit - Get the compile unit for the given descriptor. 
  ///
  CompileUnit &FindCompileUnit(DICompileUnit Unit) const {
    DenseMap<Value *, CompileUnit *>::const_iterator I = 
      CompileUnitMap.find(Unit.getGV());
    assert(I != CompileUnitMap.end() && "Missing compile unit.");
    return *I->second;
  }

  /// NewDbgScopeVariable - Create a new scope variable.
  ///
  DIE *NewDbgScopeVariable(DbgVariable *DV, CompileUnit *Unit) {
    // Get the descriptor.
    const DIVariable &VD = DV->getVariable();

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

    // Define variable debug information entry.
    DIE *VariableDie = new DIE(Tag);
    std::string Name;
    VD.getName(Name);
    AddString(VariableDie, DW_AT_name, DW_FORM_string, Name);

    // Add source line info if available.
    AddSourceLine(VariableDie, &VD);

    // Add variable type.
    AddType(Unit, VariableDie, VD.getType());

    // Add variable address.
    MachineLocation Location;
    Location.set(RI->getFrameRegister(*MF),
                 RI->getFrameIndexOffset(*MF, DV->getFrameIndex()));
    AddAddress(VariableDie, DW_AT_location, Location);

    return VariableDie;
  }

  /// getOrCreateScope - Returns the scope associated with the given descriptor.
  ///
  DbgScope *getOrCreateScope(GlobalVariable *V) {
    DbgScope *&Slot = DbgScopeMap[V];
    if (Slot) return Slot;

    DbgScope *Parent = NULL;
    DIBlock Block(V);

    // Don't create a new scope if we already created one for an inlined
    // function.
    DenseMap<const GlobalVariable *, DbgScope *>::iterator
      II = AbstractInstanceRootMap.find(V);
    if (II != AbstractInstanceRootMap.end())
      return LexicalScopeStack.back();

    if (!Block.isNull()) {
      DIDescriptor ParentDesc = Block.getContext();
      Parent = 
        ParentDesc.isNull() ?  NULL : getOrCreateScope(ParentDesc.getGV());
    }

    Slot = new DbgScope(Parent, DIDescriptor(V));

    if (Parent)
      Parent->AddScope(Slot);
    else
      // First function is top level function.
      FunctionDbgScope = Slot;

    return Slot;
  }

  /// ConstructDbgScope - Construct the components of a scope.
  ///
  void ConstructDbgScope(DbgScope *ParentScope,
                         unsigned ParentStartID, unsigned ParentEndID,
                         DIE *ParentDie, CompileUnit *Unit) {
    // Add variables to scope.
    SmallVector<DbgVariable *, 8> &Variables = ParentScope->getVariables();
    for (unsigned i = 0, N = Variables.size(); i < N; ++i) {
      DIE *VariableDie = NewDbgScopeVariable(Variables[i], Unit);
      if (VariableDie) ParentDie->AddChild(VariableDie);
    }

    // Add concrete instances to scope.
    SmallVector<DbgConcreteScope *, 8> &ConcreteInsts = ParentScope->getConcreteInsts();
    for (unsigned i = 0, N = ConcreteInsts.size(); i < N; ++i) {
      DbgConcreteScope *ConcreteInst = ConcreteInsts[i];
      DIE *Die = ConcreteInst->getDie();

      unsigned StartID = ConcreteInst->getStartLabelID();
      unsigned EndID = ConcreteInst->getEndLabelID();

      // Add the scope bounds.
      if (StartID)
        AddLabel(Die, DW_AT_low_pc, DW_FORM_addr,
                 DWLabel("label", StartID));
      else
        AddLabel(Die, DW_AT_low_pc, DW_FORM_addr,
                 DWLabel("func_begin", SubprogramCount));

      if (EndID)
        AddLabel(Die, DW_AT_high_pc, DW_FORM_addr,
                 DWLabel("label", EndID));
      else
        AddLabel(Die, DW_AT_high_pc, DW_FORM_addr,
                 DWLabel("func_end", SubprogramCount));

      ParentDie->AddChild(Die);
    }

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

      unsigned StartID = MMI->MappedLabel(Scope->getStartLabelID());
      unsigned EndID = MMI->MappedLabel(Scope->getEndLabelID());

      // Ignore empty scopes. 
      if (StartID == EndID && StartID != 0) continue;

      // Do not ignore inlined scopes even if they don't have any variables or
      // scopes.
      if (Scope->getScopes().empty() && Scope->getVariables().empty() &&
          Scope->getConcreteInsts().empty())
        continue;

      if (StartID == ParentStartID && EndID == ParentEndID) {
        // Just add stuff to the parent scope.
        ConstructDbgScope(Scope, ParentStartID, ParentEndID, ParentDie, Unit);
      } else {
        DIE *ScopeDie = new DIE(DW_TAG_lexical_block);

        // Add the scope bounds.
        if (StartID)
          AddLabel(ScopeDie, DW_AT_low_pc, DW_FORM_addr,
                   DWLabel("label", StartID));
        else
          AddLabel(ScopeDie, DW_AT_low_pc, DW_FORM_addr,
                   DWLabel("func_begin", SubprogramCount));

        if (EndID)
          AddLabel(ScopeDie, DW_AT_high_pc, DW_FORM_addr,
                   DWLabel("label", EndID));
        else
          AddLabel(ScopeDie, DW_AT_high_pc, DW_FORM_addr,
                   DWLabel("func_end", SubprogramCount));

        // Add the scope's contents.
        ConstructDbgScope(Scope, StartID, EndID, ScopeDie, Unit);
        ParentDie->AddChild(ScopeDie);
      }
    }
  }

  /// ConstructFunctionDbgScope - Construct the scope for the subprogram.
  ///
  void ConstructFunctionDbgScope(DbgScope *RootScope) {
    // Exit if there is no root scope.
    if (!RootScope) return;
    DIDescriptor Desc = RootScope->getDesc();
    if (Desc.isNull())
      return;

    // Get the subprogram debug information entry.
    DISubprogram SPD(Desc.getGV());

    // Get the compile unit context.
    CompileUnit *Unit = MainCU;
    if (!Unit)
      Unit = &FindCompileUnit(SPD.getCompileUnit());

    // Get the subprogram die.
    DIE *SPDie = Unit->getDieMapSlotFor(SPD.getGV());
    assert(SPDie && "Missing subprogram descriptor");

    // Add the function bounds.
    AddLabel(SPDie, DW_AT_low_pc, DW_FORM_addr,
                    DWLabel("func_begin", SubprogramCount));
    AddLabel(SPDie, DW_AT_high_pc, DW_FORM_addr,
                    DWLabel("func_end", SubprogramCount));
    MachineLocation Location(RI->getFrameRegister(*MF));
    AddAddress(SPDie, DW_AT_frame_base, Location);

    ConstructDbgScope(RootScope, 0, 0, SPDie, Unit);
  }

  /// ConstructFunctionDbgScope - Construct the scope for the abstract debug
  /// scope.
  ///
  void ConstructAbstractDbgScope(DbgScope *AbsScope) {
    // Exit if there is no root scope.
    if (!AbsScope) return;

    DIDescriptor Desc = AbsScope->getDesc();
    if (Desc.isNull())
      return;

    // Get the subprogram debug information entry.
    DISubprogram SPD(Desc.getGV());

    // Get the compile unit context.
    CompileUnit *Unit = MainCU;
    if (!Unit)
      Unit = &FindCompileUnit(SPD.getCompileUnit());

    // Get the subprogram die.
    DIE *SPDie = Unit->getDieMapSlotFor(SPD.getGV());
    assert(SPDie && "Missing subprogram descriptor");

    ConstructDbgScope(AbsScope, 0, 0, SPDie, Unit);
  }

  /// ConstructDefaultDbgScope - Construct a default scope for the subprogram.
  ///
  void ConstructDefaultDbgScope(MachineFunction *MF) {
    const char *FnName = MF->getFunction()->getNameStart();
    if (MainCU) {
      StringMap<DIE*> &Globals = MainCU->getGlobals();
      StringMap<DIE*>::iterator GI = Globals.find(FnName);
      if (GI != Globals.end()) {
        DIE *SPDie = GI->second;

        // Add the function bounds.
        AddLabel(SPDie, DW_AT_low_pc, DW_FORM_addr,
                 DWLabel("func_begin", SubprogramCount));
        AddLabel(SPDie, DW_AT_high_pc, DW_FORM_addr,
                 DWLabel("func_end", SubprogramCount));

        MachineLocation Location(RI->getFrameRegister(*MF));
        AddAddress(SPDie, DW_AT_frame_base, Location);
        return;
      }
    } else {
      for (unsigned i = 0, e = CompileUnits.size(); i != e; ++i) {
        CompileUnit *Unit = CompileUnits[i];
        StringMap<DIE*> &Globals = Unit->getGlobals();
        StringMap<DIE*>::iterator GI = Globals.find(FnName);
        if (GI != Globals.end()) {
          DIE *SPDie = GI->second;

          // Add the function bounds.
          AddLabel(SPDie, DW_AT_low_pc, DW_FORM_addr,
                   DWLabel("func_begin", SubprogramCount));
          AddLabel(SPDie, DW_AT_high_pc, DW_FORM_addr,
                   DWLabel("func_end", SubprogramCount));

          MachineLocation Location(RI->getFrameRegister(*MF));
          AddAddress(SPDie, DW_AT_frame_base, Location);
          return;
        }
      }
    }

#if 0
    // FIXME: This is causing an abort because C++ mangled names are compared
    // with their unmangled counterparts. See PR2885. Don't do this assert.
    assert(0 && "Couldn't find DIE for machine function!");
#endif
  }

  /// EmitInitial - Emit initial Dwarf declarations.  This is necessary for cc
  /// tools to recognize the object file contains Dwarf information.
  void EmitInitial() {
    // Check to see if we already emitted intial headers.
    if (didInitial) return;
    didInitial = true;

    // Dwarf sections base addresses.
    if (TAI->doesDwarfRequireFrameSection()) {
      Asm->SwitchToDataSection(TAI->getDwarfFrameSection());
      EmitLabel("section_debug_frame", 0);
    }
    Asm->SwitchToDataSection(TAI->getDwarfInfoSection());
    EmitLabel("section_info", 0);
    Asm->SwitchToDataSection(TAI->getDwarfAbbrevSection());
    EmitLabel("section_abbrev", 0);
    Asm->SwitchToDataSection(TAI->getDwarfARangesSection());
    EmitLabel("section_aranges", 0);
    if (TAI->doesSupportMacInfoSection()) {
      Asm->SwitchToDataSection(TAI->getDwarfMacInfoSection());
      EmitLabel("section_macinfo", 0);
    }
    Asm->SwitchToDataSection(TAI->getDwarfLineSection());
    EmitLabel("section_line", 0);
    Asm->SwitchToDataSection(TAI->getDwarfLocSection());
    EmitLabel("section_loc", 0);
    Asm->SwitchToDataSection(TAI->getDwarfPubNamesSection());
    EmitLabel("section_pubnames", 0);
    Asm->SwitchToDataSection(TAI->getDwarfStrSection());
    EmitLabel("section_str", 0);
    Asm->SwitchToDataSection(TAI->getDwarfRangesSection());
    EmitLabel("section_ranges", 0);

    Asm->SwitchToSection(TAI->getTextSection());
    EmitLabel("text_begin", 0);
    Asm->SwitchToSection(TAI->getDataSection());
    EmitLabel("data_begin", 0);
  }

  /// EmitDIE - Recusively Emits a debug information entry.
  ///
  void EmitDIE(DIE *Die) {
    // Get the abbreviation for this DIE.
    unsigned AbbrevNumber = Die->getAbbrevNumber();
    const DIEAbbrev *Abbrev = Abbreviations[AbbrevNumber - 1];

    Asm->EOL();

    // Emit the code (index) for the abbreviation.
    Asm->EmitULEB128Bytes(AbbrevNumber);

    if (Asm->isVerbose())
      Asm->EOL(std::string("Abbrev [" +
                           utostr(AbbrevNumber) +
                           "] 0x" + utohexstr(Die->getOffset()) +
                           ":0x" + utohexstr(Die->getSize()) + " " +
                           TagString(Abbrev->getTag())));
    else
      Asm->EOL();

    SmallVector<DIEValue*, 32> &Values = Die->getValues();
    const SmallVector<DIEAbbrevData, 8> &AbbrevData = Abbrev->getData();

    // Emit the DIE attribute values.
    for (unsigned i = 0, N = Values.size(); i < N; ++i) {
      unsigned Attr = AbbrevData[i].getAttribute();
      unsigned Form = AbbrevData[i].getForm();
      assert(Form && "Too many attributes for DIE (check abbreviation)");

      switch (Attr) {
      case DW_AT_sibling:
        Asm->EmitInt32(Die->SiblingOffset());
        break;
      case DW_AT_abstract_origin: {
        DIEEntry *E = cast<DIEEntry>(Values[i]);
        DIE *Origin = E->getEntry();
        unsigned Addr =
          CompileUnitOffsets[Die->getAbstractCompileUnit()] +
          Origin->getOffset();

        Asm->EmitInt32(Addr);
        break;
      }
      default:
        // Emit an attribute using the defined form.
        Values[i]->EmitValue(this, Form);
        break;
      }

      Asm->EOL(AttributeString(Attr));
    }

    // Emit the DIE children if any.
    if (Abbrev->getChildrenFlag() == DW_CHILDREN_yes) {
      const std::vector<DIE *> &Children = Die->getChildren();

      for (unsigned j = 0, M = Children.size(); j < M; ++j)
        EmitDIE(Children[j]);

      Asm->EmitInt8(0); Asm->EOL("End Of Children Mark");
    }
  }

  /// SizeAndOffsetDie - Compute the size and offset of a DIE.
  ///
  unsigned SizeAndOffsetDie(DIE *Die, unsigned Offset, bool Last) {
    // Get the children.
    const std::vector<DIE *> &Children = Die->getChildren();

    // If not last sibling and has children then add sibling offset attribute.
    if (!Last && !Children.empty()) Die->AddSiblingOffset();

    // Record the abbreviation.
    AssignAbbrevNumber(Die->getAbbrev());

    // Get the abbreviation for this DIE.
    unsigned AbbrevNumber = Die->getAbbrevNumber();
    const DIEAbbrev *Abbrev = Abbreviations[AbbrevNumber - 1];

    // Set DIE offset
    Die->setOffset(Offset);

    // Start the size with the size of abbreviation code.
    Offset += TargetAsmInfo::getULEB128Size(AbbrevNumber);

    const SmallVector<DIEValue*, 32> &Values = Die->getValues();
    const SmallVector<DIEAbbrevData, 8> &AbbrevData = Abbrev->getData();

    // Size the DIE attribute values.
    for (unsigned i = 0, N = Values.size(); i < N; ++i) {
      // Size attribute value.
      Offset += Values[i]->SizeOf(TD, AbbrevData[i].getForm());
    }

    // Size the DIE children if any.
    if (!Children.empty()) {
      assert(Abbrev->getChildrenFlag() == DW_CHILDREN_yes &&
             "Children flag not set");

      for (unsigned j = 0, M = Children.size(); j < M; ++j) {
        Offset = SizeAndOffsetDie(Children[j], Offset, (j + 1) == M);
      }

      // End of children marker.
      Offset += sizeof(int8_t);
    }

    Die->setSize(Offset - Die->getOffset());
    return Offset;
  }

  /// SizeAndOffsets - Compute the size and offset of all the DIEs.
  ///
  void SizeAndOffsets() {
    // Compute size of compile unit header.
    static 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)

    // Process base compile unit.
    if (MainCU) {
      SizeAndOffsetDie(MainCU->getDie(), Offset, true);
      CompileUnitOffsets[MainCU] = 0;
      return;
    }

    // Process all compile units.
    unsigned PrevOffset = 0;

    for (unsigned i = 0, e = CompileUnits.size(); i != e; ++i) {
      CompileUnit *Unit = CompileUnits[i];
      CompileUnitOffsets[Unit] = PrevOffset;
      PrevOffset += SizeAndOffsetDie(Unit->getDie(), Offset, true)
        + sizeof(int32_t);  // FIXME - extra pad for gdb bug.
    }
  }

  /// EmitDebugInfo / EmitDebugInfoPerCU - Emit the debug info section.
  ///
  void EmitDebugInfoPerCU(CompileUnit *Unit) {
    DIE *Die = Unit->getDie();
    // Emit the compile units header.
    EmitLabel("info_begin", Unit->getID());
    // Emit size of content not including length itself
    unsigned ContentSize = Die->getSize() +
      sizeof(int16_t) + // DWARF version number
      sizeof(int32_t) + // Offset Into Abbrev. Section
      sizeof(int8_t) +  // Pointer Size (in bytes)
      sizeof(int32_t);  // FIXME - extra pad for gdb bug.
      
    Asm->EmitInt32(ContentSize);  Asm->EOL("Length of Compilation Unit Info");
    Asm->EmitInt16(DWARF_VERSION); Asm->EOL("DWARF version number");
    EmitSectionOffset("abbrev_begin", "section_abbrev", 0, 0, true, false);
    Asm->EOL("Offset Into Abbrev. Section");
    Asm->EmitInt8(TD->getPointerSize()); Asm->EOL("Address Size (in bytes)");
      
    EmitDIE(Die);
    // FIXME - extra padding for gdb bug.
    Asm->EmitInt8(0); Asm->EOL("Extra Pad For GDB");
    Asm->EmitInt8(0); Asm->EOL("Extra Pad For GDB");
    Asm->EmitInt8(0); Asm->EOL("Extra Pad For GDB");
    Asm->EmitInt8(0); Asm->EOL("Extra Pad For GDB");
    EmitLabel("info_end", Unit->getID());
      
    Asm->EOL();
  }

  void EmitDebugInfo() {
    // Start debug info section.
    Asm->SwitchToDataSection(TAI->getDwarfInfoSection());

    if (MainCU) {
      EmitDebugInfoPerCU(MainCU);
      return;
    }

    for (unsigned i = 0, e = CompileUnits.size(); i != e; ++i)
      EmitDebugInfoPerCU(CompileUnits[i]);
  }

  /// EmitAbbreviations - Emit the abbreviation section.
  ///
  void EmitAbbreviations() const {
    // Check to see if it is worth the effort.
    if (!Abbreviations.empty()) {
      // Start the debug abbrev section.
      Asm->SwitchToDataSection(TAI->getDwarfAbbrevSection());

      EmitLabel("abbrev_begin", 0);

      // For each abbrevation.
      for (unsigned i = 0, N = Abbreviations.size(); i < N; ++i) {
        // Get abbreviation data
        const DIEAbbrev *Abbrev = Abbreviations[i];

        // Emit the abbrevations code (base 1 index.)
        Asm->EmitULEB128Bytes(Abbrev->getNumber());
        Asm->EOL("Abbreviation Code");

        // Emit the abbreviations data.
        Abbrev->Emit(Asm);

        Asm->EOL();
      }

      // Mark end of abbreviations.
      Asm->EmitULEB128Bytes(0); Asm->EOL("EOM(3)");

      EmitLabel("abbrev_end", 0);

      Asm->EOL();
    }
  }

  /// EmitEndOfLineMatrix - Emit the last address of the section and the end of
  /// the line matrix.
  ///
  void EmitEndOfLineMatrix(unsigned SectionEnd) {
    // Define last address of section.
    Asm->EmitInt8(0); Asm->EOL("Extended Op");
    Asm->EmitInt8(TD->getPointerSize() + 1); Asm->EOL("Op size");
    Asm->EmitInt8(DW_LNE_set_address); Asm->EOL("DW_LNE_set_address");
    EmitReference("section_end", SectionEnd); Asm->EOL("Section end label");

    // Mark end of matrix.
    Asm->EmitInt8(0); Asm->EOL("DW_LNE_end_sequence");
    Asm->EmitULEB128Bytes(1); Asm->EOL();
    Asm->EmitInt8(1); Asm->EOL();
  }

  /// EmitDebugLines - Emit source line information.
  ///
  void EmitDebugLines() {
    // If the target is using .loc/.file, the assembler will be emitting the
    // .debug_line table automatically.
    if (TAI->hasDotLocAndDotFile())
      return;

    // Minimum line delta, thus ranging from -10..(255-10).
    const int MinLineDelta = -(DW_LNS_fixed_advance_pc + 1);
    // Maximum line delta, thus ranging from -10..(255-10).
    const int MaxLineDelta = 255 + MinLineDelta;

    // Start the dwarf line section.
    Asm->SwitchToDataSection(TAI->getDwarfLineSection());

    // Construct the section header.

    EmitDifference("line_end", 0, "line_begin", 0, true);
    Asm->EOL("Length of Source Line Info");
    EmitLabel("line_begin", 0);

    Asm->EmitInt16(DWARF_VERSION); Asm->EOL("DWARF version number");

    EmitDifference("line_prolog_end", 0, "line_prolog_begin", 0, true);
    Asm->EOL("Prolog Length");
    EmitLabel("line_prolog_begin", 0);

    Asm->EmitInt8(1); Asm->EOL("Minimum Instruction Length");

    Asm->EmitInt8(1); Asm->EOL("Default is_stmt_start flag");

    Asm->EmitInt8(MinLineDelta); Asm->EOL("Line Base Value (Special Opcodes)");

    Asm->EmitInt8(MaxLineDelta); Asm->EOL("Line Range Value (Special Opcodes)");

    Asm->EmitInt8(-MinLineDelta); Asm->EOL("Special Opcode Base");

    // Line number standard opcode encodings argument count
    Asm->EmitInt8(0); Asm->EOL("DW_LNS_copy arg count");
    Asm->EmitInt8(1); Asm->EOL("DW_LNS_advance_pc arg count");
    Asm->EmitInt8(1); Asm->EOL("DW_LNS_advance_line arg count");
    Asm->EmitInt8(1); Asm->EOL("DW_LNS_set_file arg count");
    Asm->EmitInt8(1); Asm->EOL("DW_LNS_set_column arg count");
    Asm->EmitInt8(0); Asm->EOL("DW_LNS_negate_stmt arg count");
    Asm->EmitInt8(0); Asm->EOL("DW_LNS_set_basic_block arg count");
    Asm->EmitInt8(0); Asm->EOL("DW_LNS_const_add_pc arg count");
    Asm->EmitInt8(1); Asm->EOL("DW_LNS_fixed_advance_pc arg count");

    // Emit directories.
    for (unsigned DI = 1, DE = getNumSourceDirectories()+1; DI != DE; ++DI) {
      Asm->EmitString(getSourceDirectoryName(DI));
      Asm->EOL("Directory");
    }
    Asm->EmitInt8(0); Asm->EOL("End of directories");

    // Emit files.
    for (unsigned SI = 1, SE = getNumSourceIds()+1; SI != SE; ++SI) {
      // Remember source id starts at 1.
      std::pair<unsigned, unsigned> Id = getSourceDirectoryAndFileIds(SI);
      Asm->EmitString(getSourceFileName(Id.second));
      Asm->EOL("Source");
      Asm->EmitULEB128Bytes(Id.first);
      Asm->EOL("Directory #");
      Asm->EmitULEB128Bytes(0);
      Asm->EOL("Mod date");
      Asm->EmitULEB128Bytes(0);
      Asm->EOL("File size");
    }
    Asm->EmitInt8(0); Asm->EOL("End of files");

    EmitLabel("line_prolog_end", 0);

    // A sequence for each text section.
    unsigned SecSrcLinesSize = SectionSourceLines.size();

    for (unsigned j = 0; j < SecSrcLinesSize; ++j) {
      // Isolate current sections line info.
      const std::vector<SrcLineInfo> &LineInfos = SectionSourceLines[j];

      if (Asm->isVerbose()) {
        const Section* S = SectionMap[j + 1];
        O << '\t' << TAI->getCommentString() << " Section"
          << S->getName() << '\n';
      } else
        Asm->EOL();

      // Dwarf assumes we start with first line of first source file.
      unsigned Source = 1;
      unsigned Line = 1;

      // Construct rows of the address, source, line, column matrix.
      for (unsigned i = 0, N = LineInfos.size(); i < N; ++i) {
        const SrcLineInfo &LineInfo = LineInfos[i];
        unsigned LabelID = MMI->MappedLabel(LineInfo.getLabelID());
        if (!LabelID) continue;

        if (!Asm->isVerbose())
          Asm->EOL();
        else {
          std::pair<unsigned, unsigned> SourceID =
            getSourceDirectoryAndFileIds(LineInfo.getSourceID());
          O << '\t' << TAI->getCommentString() << ' '
            << getSourceDirectoryName(SourceID.first) << ' '
            << getSourceFileName(SourceID.second)
            <<" :" << utostr_32(LineInfo.getLine()) << '\n';
        }

        // Define the line address.
        Asm->EmitInt8(0); Asm->EOL("Extended Op");
        Asm->EmitInt8(TD->getPointerSize() + 1); Asm->EOL("Op size");
        Asm->EmitInt8(DW_LNE_set_address); Asm->EOL("DW_LNE_set_address");
        EmitReference("label",  LabelID); Asm->EOL("Location label");

        // If change of source, then switch to the new source.
        if (Source != LineInfo.getSourceID()) {
          Source = LineInfo.getSourceID();
          Asm->EmitInt8(DW_LNS_set_file); Asm->EOL("DW_LNS_set_file");
          Asm->EmitULEB128Bytes(Source); Asm->EOL("New Source");
        }

        // If change of line.
        if (Line != LineInfo.getLine()) {
          // Determine offset.
          int Offset = LineInfo.getLine() - Line;
          int Delta = Offset - MinLineDelta;

          // Update line.
          Line = LineInfo.getLine();

          // If delta is small enough and in range...
          if (Delta >= 0 && Delta < (MaxLineDelta - 1)) {
            // ... then use fast opcode.
            Asm->EmitInt8(Delta - MinLineDelta); Asm->EOL("Line Delta");
          } else {
            // ... otherwise use long hand.
            Asm->EmitInt8(DW_LNS_advance_line); Asm->EOL("DW_LNS_advance_line");
            Asm->EmitSLEB128Bytes(Offset); Asm->EOL("Line Offset");
            Asm->EmitInt8(DW_LNS_copy); Asm->EOL("DW_LNS_copy");
          }
        } else {
          // Copy the previous row (different address or source)
          Asm->EmitInt8(DW_LNS_copy); Asm->EOL("DW_LNS_copy");
        }
      }

      EmitEndOfLineMatrix(j + 1);
    }

    if (SecSrcLinesSize == 0)
      // Because we're emitting a debug_line section, we still need a line
      // table. The linker and friends expect it to exist. If there's nothing to
      // put into it, emit an empty table.
      EmitEndOfLineMatrix(1);

    EmitLabel("line_end", 0);

    Asm->EOL();
  }

  /// EmitCommonDebugFrame - Emit common frame info into a debug frame section.
  ///
  void EmitCommonDebugFrame() {
    if (!TAI->doesDwarfRequireFrameSection())
      return;

    int stackGrowth =
        Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
          TargetFrameInfo::StackGrowsUp ?
        TD->getPointerSize() : -TD->getPointerSize();

    // Start the dwarf frame section.
    Asm->SwitchToDataSection(TAI->getDwarfFrameSection());

    EmitLabel("debug_frame_common", 0);
    EmitDifference("debug_frame_common_end", 0,
                   "debug_frame_common_begin", 0, true);
    Asm->EOL("Length of Common Information Entry");

    EmitLabel("debug_frame_common_begin", 0);
    Asm->EmitInt32((int)DW_CIE_ID);
    Asm->EOL("CIE Identifier Tag");
    Asm->EmitInt8(DW_CIE_VERSION);
    Asm->EOL("CIE Version");
    Asm->EmitString("");
    Asm->EOL("CIE Augmentation");
    Asm->EmitULEB128Bytes(1);
    Asm->EOL("CIE Code Alignment Factor");
    Asm->EmitSLEB128Bytes(stackGrowth);
    Asm->EOL("CIE Data Alignment Factor");
    Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), false));
    Asm->EOL("CIE RA Column");

    std::vector<MachineMove> Moves;
    RI->getInitialFrameState(Moves);

    EmitFrameMoves(NULL, 0, Moves, false);

    Asm->EmitAlignment(2, 0, 0, false);
    EmitLabel("debug_frame_common_end", 0);

    Asm->EOL();
  }

  /// EmitFunctionDebugFrame - Emit per function frame info into a debug frame
  /// section.
  void EmitFunctionDebugFrame(const FunctionDebugFrameInfo &DebugFrameInfo) {
    if (!TAI->doesDwarfRequireFrameSection())
      return;

    // Start the dwarf frame section.
    Asm->SwitchToDataSection(TAI->getDwarfFrameSection());

    EmitDifference("debug_frame_end", DebugFrameInfo.Number,
                   "debug_frame_begin", DebugFrameInfo.Number, true);
    Asm->EOL("Length of Frame Information Entry");

    EmitLabel("debug_frame_begin", DebugFrameInfo.Number);

    EmitSectionOffset("debug_frame_common", "section_debug_frame",
                      0, 0, true, false);
    Asm->EOL("FDE CIE offset");

    EmitReference("func_begin", DebugFrameInfo.Number);
    Asm->EOL("FDE initial location");
    EmitDifference("func_end", DebugFrameInfo.Number,
                   "func_begin", DebugFrameInfo.Number);
    Asm->EOL("FDE address range");

    EmitFrameMoves("func_begin", DebugFrameInfo.Number, DebugFrameInfo.Moves, 
                   false);

    Asm->EmitAlignment(2, 0, 0, false);
    EmitLabel("debug_frame_end", DebugFrameInfo.Number);

    Asm->EOL();
  }

  void EmitDebugPubNamesPerCU(CompileUnit *Unit) {
    EmitDifference("pubnames_end", Unit->getID(),
                   "pubnames_begin", Unit->getID(), true);
    Asm->EOL("Length of Public Names Info");
      
    EmitLabel("pubnames_begin", Unit->getID());
      
    Asm->EmitInt16(DWARF_VERSION); Asm->EOL("DWARF Version");
      
    EmitSectionOffset("info_begin", "section_info",
                      Unit->getID(), 0, true, false);
    Asm->EOL("Offset of Compilation Unit Info");
      
    EmitDifference("info_end", Unit->getID(), "info_begin", Unit->getID(),
                   true);
    Asm->EOL("Compilation Unit Length");
      
    StringMap<DIE*> &Globals = Unit->getGlobals();
    for (StringMap<DIE*>::const_iterator
           GI = Globals.begin(), GE = Globals.end(); GI != GE; ++GI) {
      const char *Name = GI->getKeyData();
      DIE * Entity = GI->second;
        
      Asm->EmitInt32(Entity->getOffset()); Asm->EOL("DIE offset");
      Asm->EmitString(Name, strlen(Name)); Asm->EOL("External Name");
    }
      
    Asm->EmitInt32(0); Asm->EOL("End Mark");
    EmitLabel("pubnames_end", Unit->getID());
      
    Asm->EOL();
  }

  /// EmitDebugPubNames - Emit visible names into a debug pubnames section.
  ///
  void EmitDebugPubNames() {
    // Start the dwarf pubnames section.
    Asm->SwitchToDataSection(TAI->getDwarfPubNamesSection());

    if (MainCU) {
      EmitDebugPubNamesPerCU(MainCU);
      return;
    }

    for (unsigned i = 0, e = CompileUnits.size(); i != e; ++i)
      EmitDebugPubNamesPerCU(CompileUnits[i]);
  }

  /// EmitDebugStr - Emit visible names into a debug str section.
  ///
  void EmitDebugStr() {
    // Check to see if it is worth the effort.
    if (!StringPool.empty()) {
      // Start the dwarf str section.
      Asm->SwitchToDataSection(TAI->getDwarfStrSection());

      // For each of strings in the string pool.
      for (unsigned StringID = 1, N = StringPool.size();
           StringID <= N; ++StringID) {
        // Emit a label for reference from debug information entries.
        EmitLabel("string", StringID);
        // Emit the string itself.
        const std::string &String = StringPool[StringID];
        Asm->EmitString(String); Asm->EOL();
      }

      Asm->EOL();
    }
  }

  /// EmitDebugLoc - Emit visible names into a debug loc section.
  ///
  void EmitDebugLoc() {
    // Start the dwarf loc section.
    Asm->SwitchToDataSection(TAI->getDwarfLocSection());

    Asm->EOL();
  }

  /// EmitDebugARanges - Emit visible names into a debug aranges section.
  ///
  void EmitDebugARanges() {
    // Start the dwarf aranges section.
    Asm->SwitchToDataSection(TAI->getDwarfARangesSection());

    // FIXME - Mock up
#if 0
    CompileUnit *Unit = GetBaseCompileUnit();

    // Don't include size of length
    Asm->EmitInt32(0x1c); Asm->EOL("Length of Address Ranges Info");

    Asm->EmitInt16(DWARF_VERSION); Asm->EOL("Dwarf Version");

    EmitReference("info_begin", Unit->getID());
    Asm->EOL("Offset of Compilation Unit Info");

    Asm->EmitInt8(TD->getPointerSize()); Asm->EOL("Size of Address");

    Asm->EmitInt8(0); Asm->EOL("Size of Segment Descriptor");

    Asm->EmitInt16(0);  Asm->EOL("Pad (1)");
    Asm->EmitInt16(0);  Asm->EOL("Pad (2)");

    // Range 1
    EmitReference("text_begin", 0); Asm->EOL("Address");
    EmitDifference("text_end", 0, "text_begin", 0, true); Asm->EOL("Length");

    Asm->EmitInt32(0); Asm->EOL("EOM (1)");
    Asm->EmitInt32(0); Asm->EOL("EOM (2)");
#endif

    Asm->EOL();
  }

  /// EmitDebugRanges - Emit visible names into a debug ranges section.
  ///
  void EmitDebugRanges() {
    // Start the dwarf ranges section.
    Asm->SwitchToDataSection(TAI->getDwarfRangesSection());

    Asm->EOL();
  }

  /// EmitDebugMacInfo - Emit visible names into a debug macinfo section.
  ///
  void EmitDebugMacInfo() {
    if (TAI->doesSupportMacInfoSection()) {
      // Start the dwarf macinfo section.
      Asm->SwitchToDataSection(TAI->getDwarfMacInfoSection());

      Asm->EOL();
    }
  }

  /// EmitDebugInlineInfo - Emit inline info using following format.
  /// Section Header:
  /// 1. length of section
  /// 2. Dwarf version number
  /// 3. address size.
  ///
  /// Entries (one "entry" for each function that was inlined):
  ///
  /// 1. offset into __debug_str section for MIPS linkage name, if exists; 
  ///   otherwise offset into __debug_str for regular function name.
  /// 2. offset into __debug_str section for regular function name.
  /// 3. an unsigned LEB128 number indicating the number of distinct inlining 
  /// instances for the function.
  /// 
  /// The rest of the entry consists of a {die_offset, low_pc}  pair for each 
  /// inlined instance; the die_offset points to the inlined_subroutine die in
  /// the __debug_info section, and the low_pc is the starting address  for the
  ///  inlining instance.
  void EmitDebugInlineInfo() {
    if (!TAI->doesDwarfUsesInlineInfoSection())
      return;

    if (!MainCU)
      return;

    Asm->SwitchToDataSection(TAI->getDwarfDebugInlineSection());
    Asm->EOL();
    EmitDifference("debug_inlined_end", 1,
                   "debug_inlined_begin", 1, true);
    Asm->EOL("Length of Debug Inlined Information Entry");

    EmitLabel("debug_inlined_begin", 1);

    Asm->EmitInt16(DWARF_VERSION); Asm->EOL("Dwarf Version");
    Asm->EmitInt8(TD->getPointerSize()); Asm->EOL("Address Size (in bytes)");

    for (DenseMap<GlobalVariable *, SmallVector<unsigned, 4> >::iterator 
           I = InlineInfo.begin(), E = InlineInfo.end(); I != E; ++I) {
      GlobalVariable *GV = I->first;
      SmallVector<unsigned, 4> &Labels = I->second;
      DISubprogram SP(GV);
      std::string Name;
      std::string LName;

      SP.getLinkageName(LName);
      SP.getName(Name);

      Asm->EmitString(LName.empty() ? Name : LName);
      Asm->EOL("MIPS linkage name");

      Asm->EmitString(Name); Asm->EOL("Function name");

      Asm->EmitULEB128Bytes(Labels.size()); Asm->EOL("Inline count");

      for (SmallVector<unsigned, 4>::iterator LI = Labels.begin(),
             LE = Labels.end(); LI != LE; ++LI) {
        DIE *SP = MainCU->getDieMapSlotFor(GV);
        Asm->EmitInt32(SP->getOffset()); Asm->EOL("DIE offset");

        if (TD->getPointerSize() == sizeof(int32_t))
          O << TAI->getData32bitsDirective();
        else
          O << TAI->getData64bitsDirective();
        PrintLabelName("label", *LI); Asm->EOL("low_pc");
      }
    }

    EmitLabel("debug_inlined_end", 1);
    Asm->EOL();
  }

  /// 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 GetOrCreateSourceID(const std::string &DirName,
                               const std::string &FileName) {
    unsigned DId;
    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;
  }

  void ConstructCompileUnit(GlobalVariable *GV) {
    DICompileUnit DIUnit(GV);
    std::string Dir, FN, Prod;
    unsigned ID = GetOrCreateSourceID(DIUnit.getDirectory(Dir),
                                      DIUnit.getFilename(FN));

    DIE *Die = new DIE(DW_TAG_compile_unit);
    AddSectionOffset(Die, DW_AT_stmt_list, DW_FORM_data4,
                     DWLabel("section_line", 0), DWLabel("section_line", 0),
                     false);
    AddString(Die, DW_AT_producer, DW_FORM_string, DIUnit.getProducer(Prod));
    AddUInt(Die, DW_AT_language, DW_FORM_data1, DIUnit.getLanguage());
    AddString(Die, DW_AT_name, DW_FORM_string, FN);
    if (!Dir.empty())
      AddString(Die, DW_AT_comp_dir, DW_FORM_string, Dir);
    if (DIUnit.isOptimized())
      AddUInt(Die, DW_AT_APPLE_optimized, DW_FORM_flag, 1);
    std::string Flags;
    DIUnit.getFlags(Flags);
    if (!Flags.empty())
      AddString(Die, DW_AT_APPLE_flags, DW_FORM_string, Flags);
    unsigned RVer = DIUnit.getRunTimeVersion();
    if (RVer)
      AddUInt(Die, DW_AT_APPLE_major_runtime_vers, DW_FORM_data1, RVer);

    CompileUnit *Unit = new CompileUnit(ID, Die);
    if (DIUnit.isMain()) {
      assert(!MainCU && "Multiple main compile units are found!");
      MainCU = Unit;
    }
    CompileUnitMap[DIUnit.getGV()] = Unit;
    CompileUnits.push_back(Unit);
  }

  /// ConstructCompileUnits - Create a compile unit DIEs.
  void ConstructCompileUnits() {
    GlobalVariable *Root = M->getGlobalVariable("llvm.dbg.compile_units");
    if (!Root)
      return;
    assert(Root->hasLinkOnceLinkage() && Root->hasOneUse() &&
           "Malformed compile unit descriptor anchor type");
    Constant *RootC = cast<Constant>(*Root->use_begin());
    assert(RootC->hasNUsesOrMore(1) &&
           "Malformed compile unit descriptor anchor type");
    for (Value::use_iterator UI = RootC->use_begin(), UE = Root->use_end();
         UI != UE; ++UI)
      for (Value::use_iterator UUI = UI->use_begin(), UUE = UI->use_end();
           UUI != UUE; ++UUI) {
        GlobalVariable *GV = cast<GlobalVariable>(*UUI);
        ConstructCompileUnit(GV);
      }
  }

  bool ConstructGlobalVariableDIE(GlobalVariable *GV) {
    DIGlobalVariable DI_GV(GV);
    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());
    if (Slot)
      return false;

    DIE *VariableDie = CreateGlobalVariableDIE(DW_Unit, DI_GV);

    // Add address.
    DIEBlock *Block = new DIEBlock();
    AddUInt(Block, 0, DW_FORM_data1, DW_OP_addr);
    std::string GLN;
    AddObjectLabel(Block, 0, DW_FORM_udata,
                   Asm->getGlobalLinkName(DI_GV.getGlobal(), GLN));
    AddBlock(VariableDie, DW_AT_location, 0, Block);

    // Add to map.
    Slot = VariableDie;

    // Add to context owner.
    DW_Unit->getDie()->AddChild(VariableDie);

    // Expose as global. FIXME - need to check external flag.
    std::string Name;
    DW_Unit->AddGlobal(DI_GV.getName(Name), VariableDie);
    return true;
  }

  /// ConstructGlobalVariableDIEs - Create DIEs for each of the externally 
  /// visible global variables. Return true if at least one global DIE is
  /// created.
  bool ConstructGlobalVariableDIEs() {
    GlobalVariable *Root = M->getGlobalVariable("llvm.dbg.global_variables");
    if (!Root)
      return false;

    assert(Root->hasLinkOnceLinkage() && Root->hasOneUse() &&
           "Malformed global variable descriptor anchor type");
    Constant *RootC = cast<Constant>(*Root->use_begin());
    assert(RootC->hasNUsesOrMore(1) &&
           "Malformed global variable descriptor anchor type");

    bool Result = false;
    for (Value::use_iterator UI = RootC->use_begin(), UE = Root->use_end();
         UI != UE; ++UI)
      for (Value::use_iterator UUI = UI->use_begin(), UUE = UI->use_end();
           UUI != UUE; ++UUI)
        Result |= ConstructGlobalVariableDIE(cast<GlobalVariable>(*UUI));

    return Result;
  }

  bool ConstructSubprogram(GlobalVariable *GV) {
    DISubprogram SP(GV);
    CompileUnit *Unit = MainCU;
    if (!Unit)
      Unit = &FindCompileUnit(SP.getCompileUnit());

    // Check for pre-existence.
    DIE *&Slot = Unit->getDieMapSlotFor(GV);
    if (Slot)
      return false;

    if (!SP.isDefinition())
      // This is a method declaration which will be handled while
      // constructing class type.
      return false;

    DIE *SubprogramDie = CreateSubprogramDIE(Unit, SP);

    // Add to map.
    Slot = SubprogramDie;
    // Add to context owner.
    Unit->getDie()->AddChild(SubprogramDie);
    // Expose as global.
    std::string Name;
    Unit->AddGlobal(SP.getName(Name), SubprogramDie);
    return true;
  }

  /// ConstructSubprograms - Create DIEs for each of the externally visible
  /// subprograms. Return true if at least one subprogram DIE is created.
  bool ConstructSubprograms() {
    GlobalVariable *Root = M->getGlobalVariable("llvm.dbg.subprograms");
    if (!Root)
      return false;

    assert(Root->hasLinkOnceLinkage() && Root->hasOneUse() &&
           "Malformed subprogram descriptor anchor type");
    Constant *RootC = cast<Constant>(*Root->use_begin());
    assert(RootC->hasNUsesOrMore(1) &&
           "Malformed subprogram descriptor anchor type");

    bool Result = false;
    for (Value::use_iterator UI = RootC->use_begin(), UE = Root->use_end();
         UI != UE; ++UI)
      for (Value::use_iterator UUI = UI->use_begin(), UUE = UI->use_end();
           UUI != UUE; ++UUI)
        Result |= ConstructSubprogram(cast<GlobalVariable>(*UUI));

    return Result;
  }

public:
  //===--------------------------------------------------------------------===//
  // Main entry points.
  //
  DwarfDebug(raw_ostream &OS, AsmPrinter *A, const TargetAsmInfo *T)
    : Dwarf(OS, A, T, "dbg"), MainCU(0),
      AbbreviationsSet(InitAbbreviationsSetSize), Abbreviations(),
      ValuesSet(InitValuesSetSize), Values(), StringPool(), SectionMap(),
      SectionSourceLines(), didInitial(false), shouldEmit(false),
      FunctionDbgScope(0), DebugTimer(0) {
    if (TimePassesIsEnabled)
      DebugTimer = new Timer("Dwarf Debug Writer",
                             getDwarfTimerGroup());
  }
  virtual ~DwarfDebug() {
    for (unsigned j = 0, M = Values.size(); j < M; ++j)
      delete Values[j];

    for (DenseMap<const GlobalVariable *, DbgScope *>::iterator
           I = AbstractInstanceRootMap.begin(),
           E = AbstractInstanceRootMap.end(); I != E;++I)
      delete I->second;

    delete DebugTimer;
  }

  /// ShouldEmitDwarfDebug - Returns true if Dwarf debugging declarations should
  /// be emitted.
  bool ShouldEmitDwarfDebug() const { return shouldEmit; }

  /// SetDebugInfo - Create global DIEs and emit initial debug info sections.
  /// This is inovked by the target AsmPrinter.
  void SetDebugInfo(MachineModuleInfo *mmi) {
    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    // Create all the compile unit DIEs.
    ConstructCompileUnits();
      
    if (CompileUnits.empty()) {
      if (TimePassesIsEnabled)
        DebugTimer->stopTimer();

      return;
    }

    // Create DIEs for each of the externally visible global variables.
    bool globalDIEs = ConstructGlobalVariableDIEs();

    // Create DIEs for each of the externally visible subprograms.
    bool subprogramDIEs = ConstructSubprograms();

    // If there is not any debug info available for any global variables
    // and any subprograms then there is not any debug info to emit.
    if (!globalDIEs && !subprogramDIEs) {
      if (TimePassesIsEnabled)
        DebugTimer->stopTimer();

      return;
    }

    MMI = mmi;
    shouldEmit = true;
    MMI->setDebugInfoAvailability(true);

    // Prime section data.
    SectionMap.insert(TAI->getTextSection());

    // Print out .file directives to specify files for .loc directives. These
    // are printed out early so that they precede any .loc directives.
    if (TAI->hasDotLocAndDotFile()) {
      for (unsigned i = 1, e = getNumSourceIds()+1; i != e; ++i) {
        // Remember source id starts at 1.
        std::pair<unsigned, unsigned> Id = getSourceDirectoryAndFileIds(i);
        sys::Path FullPath(getSourceDirectoryName(Id.first));
        bool AppendOk =
          FullPath.appendComponent(getSourceFileName(Id.second));
        assert(AppendOk && "Could not append filename to directory!");
        AppendOk = false;
        Asm->EmitFile(i, FullPath.toString());
        Asm->EOL();
      }
    }

    // Emit initial sections
    EmitInitial();

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();
  }

  /// BeginModule - Emit all Dwarf sections that should come prior to the
  /// content.
  void BeginModule(Module *M) {
    this->M = M;
  }

  /// EndModule - Emit all Dwarf sections that should come after the content.
  ///
  void EndModule() {
    if (!ShouldEmitDwarfDebug())
      return;

    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    // Standard sections final addresses.
    Asm->SwitchToSection(TAI->getTextSection());
    EmitLabel("text_end", 0);
    Asm->SwitchToSection(TAI->getDataSection());
    EmitLabel("data_end", 0);

    // End text sections.
    for (unsigned i = 1, N = SectionMap.size(); i <= N; ++i) {
      Asm->SwitchToSection(SectionMap[i]);
      EmitLabel("section_end", i);
    }

    // Emit common frame information.
    EmitCommonDebugFrame();

    // Emit function debug frame information
    for (std::vector<FunctionDebugFrameInfo>::iterator I = DebugFrames.begin(),
           E = DebugFrames.end(); I != E; ++I)
      EmitFunctionDebugFrame(*I);

    // Compute DIE offsets and sizes.
    SizeAndOffsets();

    // Emit all the DIEs into a debug info section
    EmitDebugInfo();

    // Corresponding abbreviations into a abbrev section.
    EmitAbbreviations();

    // Emit source line correspondence into a debug line section.
    EmitDebugLines();

    // Emit info into a debug pubnames section.
    EmitDebugPubNames();

    // Emit info into a debug str section.
    EmitDebugStr();

    // Emit info into a debug loc section.
    EmitDebugLoc();

    // Emit info into a debug aranges section.
    EmitDebugARanges();

    // Emit info into a debug ranges section.
    EmitDebugRanges();

    // Emit info into a debug macinfo section.
    EmitDebugMacInfo();

    // Emit inline info.
    EmitDebugInlineInfo();

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();
  }

  /// BeginFunction - Gather pre-function debug information.  Assumes being
  /// emitted immediately after the function entry point.
  void BeginFunction(MachineFunction *MF) {
    this->MF = MF;

    if (!ShouldEmitDwarfDebug()) return;

    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    // Begin accumulating function debug information.
    MMI->BeginFunction(MF);

    // Assumes in correct section after the entry point.
    EmitLabel("func_begin", ++SubprogramCount);

    // Emit label for the implicitly defined dbg.stoppoint at the start of
    // the function.
    DebugLoc FDL = MF->getDefaultDebugLoc();
    if (!FDL.isUnknown()) {
      DebugLocTuple DLT = MF->getDebugLocTuple(FDL);
      unsigned LabelID = RecordSourceLine(DLT.Line, DLT.Col,
                                          DICompileUnit(DLT.CompileUnit));
      Asm->printLabel(LabelID);
    }

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();
  }

  /// EndFunction - Gather and emit post-function debug information.
  ///
  void EndFunction(MachineFunction *MF) {
    if (!ShouldEmitDwarfDebug()) return;

    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    // Define end label for subprogram.
    EmitLabel("func_end", SubprogramCount);

    // Get function line info.
    if (!Lines.empty()) {
      // Get section line info.
      unsigned ID = SectionMap.insert(Asm->CurrentSection_);
      if (SectionSourceLines.size() < ID) SectionSourceLines.resize(ID);
      std::vector<SrcLineInfo> &SectionLineInfos = SectionSourceLines[ID-1];
      // Append the function info to section info.
      SectionLineInfos.insert(SectionLineInfos.end(),
                              Lines.begin(), Lines.end());
    }

    // Construct the DbgScope for abstract instances.
    for (SmallVector<DbgScope *, 32>::iterator
           I = AbstractInstanceRootList.begin(),
           E = AbstractInstanceRootList.end(); I != E; ++I)
      ConstructAbstractDbgScope(*I);

    // Construct scopes for subprogram.
    if (FunctionDbgScope)
      ConstructFunctionDbgScope(FunctionDbgScope);
    else
      // FIXME: This is wrong. We are essentially getting past a problem with
      // debug information not being able to handle unreachable blocks that have
      // debug information in them. In particular, those unreachable blocks that
      // have "region end" info in them. That situation results in the "root
      // scope" not being created. If that's the case, then emit a "default"
      // scope, i.e., one that encompasses the whole function. This isn't
      // desirable. And a better way of handling this (and all of the debugging
      // information) needs to be explored.
      ConstructDefaultDbgScope(MF);

    DebugFrames.push_back(FunctionDebugFrameInfo(SubprogramCount,
                                                 MMI->getFrameMoves()));

    // Clear debug info
    if (FunctionDbgScope) {
      delete FunctionDbgScope;
      DbgScopeMap.clear();
      DbgAbstractScopeMap.clear();
      DbgConcreteScopeMap.clear();
      InlinedVariableScopes.clear();
      FunctionDbgScope = NULL;
      LexicalScopeStack.clear();
      AbstractInstanceRootList.clear();
    }

    Lines.clear();

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();
  }

  /// RecordSourceLine - Records location information and associates it with a 
  /// label. Returns a unique label ID used to generate a label and provide
  /// correspondence to the source line list.
  unsigned RecordSourceLine(Value *V, unsigned Line, unsigned Col) {
    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    CompileUnit *Unit = CompileUnitMap[V];
    assert(Unit && "Unable to find CompileUnit");
    unsigned ID = MMI->NextLabelID();
    Lines.push_back(SrcLineInfo(Line, Col, Unit->getID(), ID));

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();

    return ID;
  }
  
  /// RecordSourceLine - Records location information and associates it with a 
  /// label. Returns a unique label ID used to generate a label and provide
  /// correspondence to the source line list.
  unsigned RecordSourceLine(unsigned Line, unsigned Col, DICompileUnit CU) {
    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    std::string Dir, Fn;
    unsigned Src = GetOrCreateSourceID(CU.getDirectory(Dir),
                                       CU.getFilename(Fn));
    unsigned ID = MMI->NextLabelID();
    Lines.push_back(SrcLineInfo(Line, Col, Src, ID));

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();

    return ID;
  }

  /// getRecordSourceLineCount - Return the number of source lines in the debug
  /// info.
  unsigned getRecordSourceLineCount() const {
    return Lines.size();
  }
                            
  /// getOrCreateSourceID - Public version of GetOrCreateSourceID. This can be
  /// timed. 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 getOrCreateSourceID(const std::string &DirName,
                               const std::string &FileName) {
    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    unsigned SrcId = GetOrCreateSourceID(DirName, FileName);

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();

    return SrcId;
  }

  /// RecordRegionStart - Indicate the start of a region.
  unsigned RecordRegionStart(GlobalVariable *V) {
    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    DbgScope *Scope = getOrCreateScope(V);
    unsigned ID = MMI->NextLabelID();
    if (!Scope->getStartLabelID()) Scope->setStartLabelID(ID);
    LexicalScopeStack.push_back(Scope);

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();

    return ID;
  }

  /// RecordRegionEnd - Indicate the end of a region.
  unsigned RecordRegionEnd(GlobalVariable *V) {
    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    DbgScope *Scope = getOrCreateScope(V);
    unsigned ID = MMI->NextLabelID();
    Scope->setEndLabelID(ID);
    if (LexicalScopeStack.size() != 0)
      LexicalScopeStack.pop_back();

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();

    return ID;
  }

  /// RecordVariable - Indicate the declaration of  a local variable.
  void RecordVariable(GlobalVariable *GV, unsigned FrameIndex,
                      const MachineInstr *MI) {
    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    DIDescriptor Desc(GV);
    DbgScope *Scope = NULL;

    if (Desc.getTag() == DW_TAG_variable) {
      // GV is a global variable.
      DIGlobalVariable DG(GV);
      Scope = getOrCreateScope(DG.getContext().getGV());
    } else {
      DenseMap<const MachineInstr *, DbgScope *>::iterator 
        SI = InlinedVariableScopes.find(MI);

      if (SI != InlinedVariableScopes.end()) {
        // or GV is an inlined local variable.
        Scope = SI->second;
      } else {
        DIVariable DV(GV);
        GlobalVariable *V = DV.getContext().getGV();

        // FIXME: The code that checks for the inlined local variable is a hack!
        DenseMap<const GlobalVariable *, DbgScope *>::iterator
          AI = AbstractInstanceRootMap.find(V);

        if (AI != AbstractInstanceRootMap.end())
          // or GV is an inlined local variable.
          Scope = AI->second;
        else
          // or GV is a local variable.
          Scope = getOrCreateScope(V);
      }
    }

    assert(Scope && "Unable to find the variable's scope");
    DbgVariable *DV = new DbgVariable(DIVariable(GV), FrameIndex);
    Scope->AddVariable(DV);

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();
  }

  //// RecordInlinedFnStart - Indicate the start of inlined subroutine.
  unsigned RecordInlinedFnStart(DISubprogram &SP, DICompileUnit CU,
                                unsigned Line, unsigned Col) {
    unsigned LabelID = MMI->NextLabelID();

    if (!TAI->doesDwarfUsesInlineInfoSection())
      return LabelID;

    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    GlobalVariable *GV = SP.getGV();
    DenseMap<const GlobalVariable *, DbgScope *>::iterator
      II = AbstractInstanceRootMap.find(GV);

    if (II == AbstractInstanceRootMap.end()) {
      // Create an abstract instance entry for this inlined function if it
      // doesn't already exist.
      DbgScope *Scope = new DbgScope(NULL, DIDescriptor(GV));

      // Get the compile unit context.
      CompileUnit *Unit = &FindCompileUnit(SP.getCompileUnit());
      DIE *SPDie = Unit->getDieMapSlotFor(GV);
      if (!SPDie)
        SPDie = CreateSubprogramDIE(Unit, SP);

      // Mark as being inlined. This makes this subprogram entry an abstract
      // instance root.
      // FIXME: Our debugger doesn't care about the value of DW_AT_inline, only
      // that it's defined. It probably won't change in the future, but this
      // could be more elegant.
      AddUInt(SPDie, DW_AT_inline, 0, DW_INL_declared_not_inlined);

      // Keep track of the abstract scope for this function.
      DbgAbstractScopeMap[GV] = Scope;

      AbstractInstanceRootMap[GV] = Scope;
      AbstractInstanceRootList.push_back(Scope);
    }

    // Create a concrete inlined instance for this inlined function.
    DbgConcreteScope *ConcreteScope = new DbgConcreteScope(DIDescriptor(GV));
    DIE *ScopeDie = new DIE(DW_TAG_inlined_subroutine);
    CompileUnit *Unit = &FindCompileUnit(SP.getCompileUnit());
    ScopeDie->setAbstractCompileUnit(Unit);

    DIE *Origin = Unit->getDieMapSlotFor(GV);
    AddDIEEntry(ScopeDie, DW_AT_abstract_origin, DW_FORM_ref4, Origin);
    AddUInt(ScopeDie, DW_AT_call_file, 0, Unit->getID());
    AddUInt(ScopeDie, DW_AT_call_line, 0, Line);
    AddUInt(ScopeDie, DW_AT_call_column, 0, Col);

    ConcreteScope->setDie(ScopeDie);
    ConcreteScope->setStartLabelID(LabelID);
    MMI->RecordUsedDbgLabel(LabelID);

    LexicalScopeStack.back()->AddConcreteInst(ConcreteScope);

    // Keep track of the concrete scope that's inlined into this function.
    DenseMap<GlobalVariable *, SmallVector<DbgScope *, 8> >::iterator
      SI = DbgConcreteScopeMap.find(GV);

    if (SI == DbgConcreteScopeMap.end())
      DbgConcreteScopeMap[GV].push_back(ConcreteScope);
    else
      SI->second.push_back(ConcreteScope);

    // Track the start label for this inlined function.
    DenseMap<GlobalVariable *, SmallVector<unsigned, 4> >::iterator
      I = InlineInfo.find(GV);

    if (I == InlineInfo.end())
      InlineInfo[GV].push_back(LabelID);
    else
      I->second.push_back(LabelID);

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();

    return LabelID;
  }

  /// RecordInlinedFnEnd - Indicate the end of inlined subroutine.
  unsigned RecordInlinedFnEnd(DISubprogram &SP) {
    if (!TAI->doesDwarfUsesInlineInfoSection())
      return 0;

    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    GlobalVariable *GV = SP.getGV();
    DenseMap<GlobalVariable *, SmallVector<DbgScope *, 8> >::iterator
      I = DbgConcreteScopeMap.find(GV);

    if (I == DbgConcreteScopeMap.end()) {
      if (TimePassesIsEnabled)
        DebugTimer->stopTimer();

      return 0;
    }

    SmallVector<DbgScope *, 8> &Scopes = I->second;
    assert(!Scopes.empty() && "We should have at least one debug scope!");
    DbgScope *Scope = Scopes.back(); Scopes.pop_back();
    unsigned ID = MMI->NextLabelID();
    MMI->RecordUsedDbgLabel(ID);
    Scope->setEndLabelID(ID);

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();

    return ID;
  }

  /// RecordVariableScope - Record scope for the variable declared by
  /// DeclareMI. DeclareMI must describe TargetInstrInfo::DECLARE. Record scopes
  /// for only inlined subroutine variables. Other variables's scopes are
  /// determined during RecordVariable().
  void RecordVariableScope(DIVariable &DV, const MachineInstr *DeclareMI) {
    if (TimePassesIsEnabled)
      DebugTimer->startTimer();

    DISubprogram SP(DV.getContext().getGV());

    if (SP.isNull()) {
      if (TimePassesIsEnabled)
        DebugTimer->stopTimer();

      return;
    }

    DenseMap<GlobalVariable *, DbgScope *>::iterator
      I = DbgAbstractScopeMap.find(SP.getGV());
    if (I != DbgAbstractScopeMap.end())
      InlinedVariableScopes[DeclareMI] = I->second;

    if (TimePassesIsEnabled)
      DebugTimer->stopTimer();
  }
};

} // End of namespace llvm

//===----------------------------------------------------------------------===//
/// DwarfWriter Implementation
///

DwarfWriter::DwarfWriter()
  : ImmutablePass(&ID), DD(0), DE(0) {}

DwarfWriter::~DwarfWriter() {
  delete DE;
  delete DD;
}

/// BeginModule - Emit all Dwarf sections that should come prior to the
/// content.
void DwarfWriter::BeginModule(Module *M,
                              MachineModuleInfo *MMI,
                              raw_ostream &OS, AsmPrinter *A,
                              const TargetAsmInfo *T) {
  DE = new DwarfException(OS, A, T);
  DD = new DwarfDebug(OS, A, T);
  DE->BeginModule(M);
  DD->BeginModule(M);
  DD->SetDebugInfo(MMI);
  DE->SetModuleInfo(MMI);
}

/// EndModule - Emit all Dwarf sections that should come after the content.
///
void DwarfWriter::EndModule() {
  DE->EndModule();
  DD->EndModule();
}

/// BeginFunction - Gather pre-function debug information.  Assumes being
/// emitted immediately after the function entry point.
void DwarfWriter::BeginFunction(MachineFunction *MF) {
  DE->BeginFunction(MF);
  DD->BeginFunction(MF);
}

/// EndFunction - Gather and emit post-function debug information.
///
void DwarfWriter::EndFunction(MachineFunction *MF) {
  DD->EndFunction(MF);
  DE->EndFunction();

  if (MachineModuleInfo *MMI = DD->getMMI() ? DD->getMMI() : DE->getMMI())
    // Clear function debug information.
    MMI->EndFunction();
}

/// RecordSourceLine - Records location information and associates it with a 
/// label. Returns a unique label ID used to generate a label and provide
/// correspondence to the source line list.
unsigned DwarfWriter::RecordSourceLine(unsigned Line, unsigned Col, 
                                       DICompileUnit CU) {
  return DD->RecordSourceLine(Line, Col, CU);
}

/// RecordRegionStart - Indicate the start of a region.
unsigned DwarfWriter::RecordRegionStart(GlobalVariable *V) {
  return DD->RecordRegionStart(V);
}

/// RecordRegionEnd - Indicate the end of a region.
unsigned DwarfWriter::RecordRegionEnd(GlobalVariable *V) {
  return DD->RecordRegionEnd(V);
}

/// getRecordSourceLineCount - Count source lines.
unsigned DwarfWriter::getRecordSourceLineCount() {
  return DD->getRecordSourceLineCount();
}

/// RecordVariable - Indicate the declaration of  a local variable.
///
void DwarfWriter::RecordVariable(GlobalVariable *GV, unsigned FrameIndex,
                                 const MachineInstr *MI) {
  DD->RecordVariable(GV, FrameIndex, MI);
}

/// ShouldEmitDwarfDebug - Returns true if Dwarf debugging declarations should
/// be emitted.
bool DwarfWriter::ShouldEmitDwarfDebug() const {
  return DD && DD->ShouldEmitDwarfDebug();
}

//// RecordInlinedFnStart - Global variable GV is inlined at the location marked
//// by LabelID label.
unsigned DwarfWriter::RecordInlinedFnStart(DISubprogram SP, DICompileUnit CU,
                                           unsigned Line, unsigned Col) {
  return DD->RecordInlinedFnStart(SP, CU, Line, Col);
}

/// RecordInlinedFnEnd - Indicate the end of inlined subroutine.
unsigned DwarfWriter::RecordInlinedFnEnd(DISubprogram SP) {
  return DD->RecordInlinedFnEnd(SP);
}

/// RecordVariableScope - Record scope for the variable declared by
/// DeclareMI. DeclareMI must describe TargetInstrInfo::DECLARE.
void DwarfWriter::RecordVariableScope(DIVariable &DV,
                                      const MachineInstr *DeclareMI) {
  DD->RecordVariableScope(DV, DeclareMI);
}