DwarfDebug.cpp

        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->OutStreamer.AddComment("Line Delta");
          Asm->EmitInt8(Delta - MinLineDelta);
        } else {
          // ... otherwise use long hand.
          Asm->OutStreamer.AddComment("DW_LNS_advance_line");
          Asm->EmitInt8(dwarf::DW_LNS_advance_line);
          Asm->EmitSLEB128(Offset, "Line Offset");
          Asm->OutStreamer.AddComment("DW_LNS_copy");
          Asm->EmitInt8(dwarf::DW_LNS_copy);
        }
      } else {
        // Copy the previous row (different address or source)
        Asm->OutStreamer.AddComment("DW_LNS_copy");
        Asm->EmitInt8(dwarf::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);

  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("line_end"));
}

/// emitCommonDebugFrame - Emit common frame info into a debug frame section.
///
void DwarfDebug::emitCommonDebugFrame() {
  if (!Asm->MAI->doesDwarfRequireFrameSection())
    return;

  int stackGrowth = Asm->getTargetData().getPointerSize();
  if (Asm->TM.getFrameInfo()->getStackGrowthDirection() ==
      TargetFrameInfo::StackGrowsDown)
    stackGrowth *= -1;

  // Start the dwarf frame section.
  Asm->OutStreamer.SwitchSection(
                              Asm->getObjFileLowering().getDwarfFrameSection());

  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("debug_frame_common"));
  Asm->OutStreamer.AddComment("Length of Common Information Entry");
  Asm->EmitLabelDifference(Asm->GetTempSymbol("debug_frame_common_end"),
                           Asm->GetTempSymbol("debug_frame_common_begin"), 4);

  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("debug_frame_common_begin"));
  Asm->OutStreamer.AddComment("CIE Identifier Tag");
  Asm->EmitInt32((int)dwarf::DW_CIE_ID);
  Asm->OutStreamer.AddComment("CIE Version");
  Asm->EmitInt8(dwarf::DW_CIE_VERSION);
  Asm->OutStreamer.AddComment("CIE Augmentation");
  Asm->OutStreamer.EmitIntValue(0, 1, /*addrspace*/0); // nul terminator.
  Asm->EmitULEB128(1, "CIE Code Alignment Factor");
  Asm->EmitSLEB128(stackGrowth, "CIE Data Alignment Factor");
  Asm->OutStreamer.AddComment("CIE RA Column");
  const TargetRegisterInfo *RI = Asm->TM.getRegisterInfo();
  Asm->EmitInt8(RI->getDwarfRegNum(RI->getRARegister(), false));

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

  Asm->EmitFrameMoves(Moves, 0, false);

  Asm->EmitAlignment(2);
  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("debug_frame_common_end"));
}

/// emitFunctionDebugFrame - Emit per function frame info into a debug frame
/// section.
void DwarfDebug::
emitFunctionDebugFrame(const FunctionDebugFrameInfo &DebugFrameInfo) {
  if (!Asm->MAI->doesDwarfRequireFrameSection())
    return;

  // Start the dwarf frame section.
  Asm->OutStreamer.SwitchSection(
                              Asm->getObjFileLowering().getDwarfFrameSection());

  Asm->OutStreamer.AddComment("Length of Frame Information Entry");
  MCSymbol *DebugFrameBegin =
    Asm->GetTempSymbol("debug_frame_begin", DebugFrameInfo.Number);
  MCSymbol *DebugFrameEnd =
    Asm->GetTempSymbol("debug_frame_end", DebugFrameInfo.Number);
  Asm->EmitLabelDifference(DebugFrameEnd, DebugFrameBegin, 4);

  Asm->OutStreamer.EmitLabel(DebugFrameBegin);

  Asm->OutStreamer.AddComment("FDE CIE offset");
  Asm->EmitSectionOffset(Asm->GetTempSymbol("debug_frame_common"), 
                         DwarfFrameSectionSym);

  Asm->OutStreamer.AddComment("FDE initial location");
  MCSymbol *FuncBeginSym =
    Asm->GetTempSymbol("func_begin", DebugFrameInfo.Number);
  Asm->OutStreamer.EmitSymbolValue(FuncBeginSym,
                                   Asm->getTargetData().getPointerSize(),
                                   0/*AddrSpace*/);
  
  
  Asm->OutStreamer.AddComment("FDE address range");
  Asm->EmitLabelDifference(Asm->GetTempSymbol("func_end",DebugFrameInfo.Number),
                           FuncBeginSym, Asm->getTargetData().getPointerSize());

  Asm->EmitFrameMoves(DebugFrameInfo.Moves, FuncBeginSym, false);

  Asm->EmitAlignment(2);
  Asm->OutStreamer.EmitLabel(DebugFrameEnd);
}

/// emitDebugPubNames - Emit visible names into a debug pubnames section.
///
void DwarfDebug::emitDebugPubNames() {
  // Start the dwarf pubnames section.
  Asm->OutStreamer.SwitchSection(
                          Asm->getObjFileLowering().getDwarfPubNamesSection());

  Asm->OutStreamer.AddComment("Length of Public Names Info");
  Asm->EmitLabelDifference(
                 Asm->GetTempSymbol("pubnames_end", ModuleCU->getID()),
                 Asm->GetTempSymbol("pubnames_begin", ModuleCU->getID()), 4);

  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("pubnames_begin",
                                                ModuleCU->getID()));

  Asm->OutStreamer.AddComment("DWARF Version");
  Asm->EmitInt16(dwarf::DWARF_VERSION); 

  Asm->OutStreamer.AddComment("Offset of Compilation Unit Info");
  Asm->EmitSectionOffset(Asm->GetTempSymbol("info_begin", ModuleCU->getID()), 
                         DwarfInfoSectionSym);

  Asm->OutStreamer.AddComment("Compilation Unit Length");
  Asm->EmitLabelDifference(Asm->GetTempSymbol("info_end", ModuleCU->getID()),
                           Asm->GetTempSymbol("info_begin", ModuleCU->getID()),
                           4);

  const StringMap<DIE*> &Globals = ModuleCU->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->OutStreamer.AddComment("DIE offset");
    Asm->EmitInt32(Entity->getOffset());
    
    if (Asm->isVerbose())
      Asm->OutStreamer.AddComment("External Name");
    Asm->OutStreamer.EmitBytes(StringRef(Name, strlen(Name)+1), 0);
  }

  Asm->OutStreamer.AddComment("End Mark");
  Asm->EmitInt32(0);
  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("pubnames_end",
                                                ModuleCU->getID()));
}

void DwarfDebug::emitDebugPubTypes() {
  // Start the dwarf pubnames section.
  Asm->OutStreamer.SwitchSection(
                          Asm->getObjFileLowering().getDwarfPubTypesSection());
  Asm->OutStreamer.AddComment("Length of Public Types Info");
  Asm->EmitLabelDifference(
                    Asm->GetTempSymbol("pubtypes_end", ModuleCU->getID()),
                    Asm->GetTempSymbol("pubtypes_begin", ModuleCU->getID()), 4);

  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("pubtypes_begin",
                                                ModuleCU->getID()));

  if (Asm->isVerbose()) Asm->OutStreamer.AddComment("DWARF Version");
  Asm->EmitInt16(dwarf::DWARF_VERSION);

  Asm->OutStreamer.AddComment("Offset of Compilation ModuleCU Info");
  Asm->EmitSectionOffset(Asm->GetTempSymbol("info_begin", ModuleCU->getID()),
                         DwarfInfoSectionSym);

  Asm->OutStreamer.AddComment("Compilation ModuleCU Length");
  Asm->EmitLabelDifference(Asm->GetTempSymbol("info_end", ModuleCU->getID()),
                           Asm->GetTempSymbol("info_begin", ModuleCU->getID()),
                           4);

  const StringMap<DIE*> &Globals = ModuleCU->getGlobalTypes();
  for (StringMap<DIE*>::const_iterator
         GI = Globals.begin(), GE = Globals.end(); GI != GE; ++GI) {
    const char *Name = GI->getKeyData();
    DIE * Entity = GI->second;

    if (Asm->isVerbose()) Asm->OutStreamer.AddComment("DIE offset");
    Asm->EmitInt32(Entity->getOffset());
    
    if (Asm->isVerbose()) Asm->OutStreamer.AddComment("External Name");
    Asm->OutStreamer.EmitBytes(StringRef(Name, GI->getKeyLength()+1), 0);
  }

  Asm->OutStreamer.AddComment("End Mark");
  Asm->EmitInt32(0); 
  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("pubtypes_end",
                                                ModuleCU->getID()));
}

/// emitDebugStr - Emit visible names into a debug str section.
///
void DwarfDebug::emitDebugStr() {
  // Check to see if it is worth the effort.
  if (StringPool.empty()) return;
  
  // Start the dwarf str section.
  Asm->OutStreamer.SwitchSection(
                                Asm->getObjFileLowering().getDwarfStrSection());

  // Get all of the string pool entries and put them in an array by their ID so
  // we can sort them.
  SmallVector<std::pair<unsigned, 
      StringMapEntry<std::pair<MCSymbol*, unsigned> >*>, 64> Entries;
  
  for (StringMap<std::pair<MCSymbol*, unsigned> >::iterator
       I = StringPool.begin(), E = StringPool.end(); I != E; ++I)
    Entries.push_back(std::make_pair(I->second.second, &*I));
  
  array_pod_sort(Entries.begin(), Entries.end());
  
  for (unsigned i = 0, e = Entries.size(); i != e; ++i) {
    // Emit a label for reference from debug information entries.
    Asm->OutStreamer.EmitLabel(Entries[i].second->getValue().first);
    
    // Emit the string itself.
    Asm->OutStreamer.EmitBytes(Entries[i].second->getKey(), 0/*addrspace*/);
  }
}

/// emitDebugLoc - Emit visible names into a debug loc section.
///
void DwarfDebug::emitDebugLoc() {
  // Start the dwarf loc section.
  Asm->OutStreamer.SwitchSection(
                              Asm->getObjFileLowering().getDwarfLocSection());
}

/// EmitDebugARanges - Emit visible names into a debug aranges section.
///
void DwarfDebug::EmitDebugARanges() {
  // Start the dwarf aranges section.
  Asm->OutStreamer.SwitchSection(
                          Asm->getObjFileLowering().getDwarfARangesSection());
}

/// emitDebugRanges - Emit visible names into a debug ranges section.
///
void DwarfDebug::emitDebugRanges() {
  // Start the dwarf ranges section.
  Asm->OutStreamer.SwitchSection(
    Asm->getObjFileLowering().getDwarfRangesSection());
  unsigned char Size = Asm->getTargetData().getPointerSize();
  for (SmallVector<const MCSymbol *, 8>::iterator
         I = DebugRangeSymbols.begin(), E = DebugRangeSymbols.end(); 
       I != E; ++I) {
    if (*I)
      Asm->OutStreamer.EmitSymbolValue(const_cast<MCSymbol*>(*I), Size, 0);
    else
      Asm->OutStreamer.EmitIntValue(0, Size, /*addrspace*/0);
  }
}

/// emitDebugMacInfo - Emit visible names into a debug macinfo section.
///
void DwarfDebug::emitDebugMacInfo() {
  if (const MCSection *LineInfo =
      Asm->getObjFileLowering().getDwarfMacroInfoSection()) {
    // Start the dwarf macinfo section.
    Asm->OutStreamer.SwitchSection(LineInfo);
  }
}

/// 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 DwarfDebug::emitDebugInlineInfo() {
  if (!Asm->MAI->doesDwarfUsesInlineInfoSection())
    return;

  if (!ModuleCU)
    return;

  Asm->OutStreamer.SwitchSection(
                        Asm->getObjFileLowering().getDwarfDebugInlineSection());

  Asm->OutStreamer.AddComment("Length of Debug Inlined Information Entry");
  Asm->EmitLabelDifference(Asm->GetTempSymbol("debug_inlined_end", 1),
                           Asm->GetTempSymbol("debug_inlined_begin", 1), 4);

  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("debug_inlined_begin", 1));

  Asm->OutStreamer.AddComment("Dwarf Version");
  Asm->EmitInt16(dwarf::DWARF_VERSION);
  Asm->OutStreamer.AddComment("Address Size (in bytes)");
  Asm->EmitInt8(Asm->getTargetData().getPointerSize());

  for (SmallVector<MDNode *, 4>::iterator I = InlinedSPNodes.begin(),
         E = InlinedSPNodes.end(); I != E; ++I) {

    MDNode *Node = *I;
    DenseMap<MDNode *, SmallVector<InlineInfoLabels, 4> >::iterator II
      = InlineInfo.find(Node);
    SmallVector<InlineInfoLabels, 4> &Labels = II->second;
    DISubprogram SP(Node);
    StringRef LName = SP.getLinkageName();
    StringRef Name = SP.getName();

    Asm->OutStreamer.AddComment("MIPS linkage name");
    if (LName.empty()) {
      Asm->OutStreamer.EmitBytes(Name, 0);
      Asm->OutStreamer.EmitIntValue(0, 1, 0); // nul terminator.
    } else 
      Asm->EmitSectionOffset(getStringPoolEntry(getRealLinkageName(LName)),
                             DwarfStrSectionSym);

    Asm->OutStreamer.AddComment("Function name");
    Asm->EmitSectionOffset(getStringPoolEntry(Name), DwarfStrSectionSym);
    Asm->EmitULEB128(Labels.size(), "Inline count");

    for (SmallVector<InlineInfoLabels, 4>::iterator LI = Labels.begin(),
           LE = Labels.end(); LI != LE; ++LI) {
      if (Asm->isVerbose()) Asm->OutStreamer.AddComment("DIE offset");
      Asm->EmitInt32(LI->second->getOffset());

      if (Asm->isVerbose()) Asm->OutStreamer.AddComment("low_pc");
      Asm->OutStreamer.EmitSymbolValue(LI->first,
                                       Asm->getTargetData().getPointerSize(),0);
    }
  }

  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("debug_inlined_end", 1));
}