AsmPrinter.cpp

//===-- AsmPrinter.cpp - Common AsmPrinter code ---------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the AsmPrinter class.
//
//===----------------------------------------------------------------------===//

#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Constants.h"
#include "llvm/Module.h"
#include "llvm/CodeGen/DwarfWriter.h"
#include "llvm/CodeGen/GCMetadataPrinter.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/Analysis/DebugInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/Target/Mangler.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallString.h"
#include <cerrno>
using namespace llvm;

static cl::opt<cl::boolOrDefault>
AsmVerbose("asm-verbose", cl::desc("Add comments to directives."),
           cl::init(cl::BOU_UNSET));

char AsmPrinter::ID = 0;
AsmPrinter::AsmPrinter(formatted_raw_ostream &o, TargetMachine &tm,
                       const MCAsmInfo *T, bool VDef)
  : MachineFunctionPass(&ID), FunctionNumber(0), O(o),
    TM(tm), MAI(T), TRI(tm.getRegisterInfo()),

    OutContext(*new MCContext()),
    // FIXME: Pass instprinter to streamer.
    OutStreamer(*createAsmStreamer(OutContext, O, *T, 0)),

    LastMI(0), LastFn(0), Counter(~0U), PrevDLT(NULL) {
  DW = 0; MMI = 0;
  switch (AsmVerbose) {
  case cl::BOU_UNSET: VerboseAsm = VDef;  break;
  case cl::BOU_TRUE:  VerboseAsm = true;  break;
  case cl::BOU_FALSE: VerboseAsm = false; break;
  }
}

AsmPrinter::~AsmPrinter() {
  for (gcp_iterator I = GCMetadataPrinters.begin(),
                    E = GCMetadataPrinters.end(); I != E; ++I)
    delete I->second;
  
  delete &OutStreamer;
  delete &OutContext;
}

TargetLoweringObjectFile &AsmPrinter::getObjFileLowering() const {
  return TM.getTargetLowering()->getObjFileLowering();
}

/// getCurrentSection() - Return the current section we are emitting to.
const MCSection *AsmPrinter::getCurrentSection() const {
  return OutStreamer.getCurrentSection();
}


void AsmPrinter::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.setPreservesAll();
  MachineFunctionPass::getAnalysisUsage(AU);
  AU.addRequired<GCModuleInfo>();
  if (VerboseAsm)
    AU.addRequired<MachineLoopInfo>();
}

bool AsmPrinter::doInitialization(Module &M) {
  // Initialize TargetLoweringObjectFile.
  const_cast<TargetLoweringObjectFile&>(getObjFileLowering())
    .Initialize(OutContext, TM);
  
  Mang = new Mangler(M, MAI->getGlobalPrefix(), MAI->getPrivateGlobalPrefix(),
                     MAI->getLinkerPrivateGlobalPrefix());
  
  // Allow the target to emit any magic that it wants at the start of the file.
  EmitStartOfAsmFile(M);

  if (MAI->hasSingleParameterDotFile()) {
    /* Very minimal debug info. It is ignored if we emit actual
       debug info. If we don't, this at least helps the user find where
       a function came from. */
    O << "\t.file\t\"" << M.getModuleIdentifier() << "\"\n";
  }

  GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();
  assert(MI && "AsmPrinter didn't require GCModuleInfo?");
  for (GCModuleInfo::iterator I = MI->begin(), E = MI->end(); I != E; ++I)
    if (GCMetadataPrinter *MP = GetOrCreateGCPrinter(*I))
      MP->beginAssembly(O, *this, *MAI);
  
  if (!M.getModuleInlineAsm().empty())
    O << MAI->getCommentString() << " Start of file scope inline assembly\n"
      << M.getModuleInlineAsm()
      << '\n' << MAI->getCommentString()
      << " End of file scope inline assembly\n";

  MMI = getAnalysisIfAvailable<MachineModuleInfo>();
  if (MMI)
    MMI->AnalyzeModule(M);
  DW = getAnalysisIfAvailable<DwarfWriter>();
  if (DW)
    DW->BeginModule(&M, MMI, O, this, MAI);

  return false;
}

bool AsmPrinter::doFinalization(Module &M) {
  // Emit global variables.
  for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I)
    PrintGlobalVariable(I);
  
  // Emit final debug information.
  if (MAI->doesSupportDebugInformation() || MAI->doesSupportExceptionHandling())
    DW->EndModule();
  
  // If the target wants to know about weak references, print them all.
  if (MAI->getWeakRefDirective()) {
    // FIXME: This is not lazy, it would be nice to only print weak references
    // to stuff that is actually used.  Note that doing so would require targets
    // to notice uses in operands (due to constant exprs etc).  This should
    // happen with the MC stuff eventually.

    // Print out module-level global variables here.
    for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
         I != E; ++I) {
      if (!I->hasExternalWeakLinkage()) continue;
      O << MAI->getWeakRefDirective();
      GetGlobalValueSymbol(I)->print(O, MAI);
      O << '\n';
    }
    
    for (Module::const_iterator I = M.begin(), E = M.end(); I != E; ++I) {
      if (!I->hasExternalWeakLinkage()) continue;
      O << MAI->getWeakRefDirective();
      GetGlobalValueSymbol(I)->print(O, MAI);
      O << '\n';
    }
  }

  if (MAI->getSetDirective()) {
    O << '\n';
    for (Module::const_alias_iterator I = M.alias_begin(), E = M.alias_end();
         I != E; ++I) {
      MCSymbol *Name = GetGlobalValueSymbol(I);

      const GlobalValue *GV = cast<GlobalValue>(I->getAliasedGlobal());
      MCSymbol *Target = GetGlobalValueSymbol(GV);

      if (I->hasExternalLinkage() || !MAI->getWeakRefDirective()) {
        O << "\t.globl\t";
        Name->print(O, MAI);
        O << '\n';
      } else if (I->hasWeakLinkage()) {
        O << MAI->getWeakRefDirective();
        Name->print(O, MAI);
        O << '\n';
      } else {
        assert(I->hasLocalLinkage() && "Invalid alias linkage");
      }

      printVisibility(Name, I->getVisibility());

      O << MAI->getSetDirective() << ' ';
      Name->print(O, MAI);
      O << ", ";
      Target->print(O, MAI);
      O << '\n';
    }
  }

  GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();
  assert(MI && "AsmPrinter didn't require GCModuleInfo?");
  for (GCModuleInfo::iterator I = MI->end(), E = MI->begin(); I != E; )
    if (GCMetadataPrinter *MP = GetOrCreateGCPrinter(*--I))
      MP->finishAssembly(O, *this, *MAI);

  // If we don't have any trampolines, then we don't require stack memory
  // to be executable. Some targets have a directive to declare this.
  Function *InitTrampolineIntrinsic = M.getFunction("llvm.init.trampoline");
  if (!InitTrampolineIntrinsic || InitTrampolineIntrinsic->use_empty())
    if (MAI->getNonexecutableStackDirective())
      O << MAI->getNonexecutableStackDirective() << '\n';

  
  // Allow the target to emit any magic that it wants at the end of the file,
  // after everything else has gone out.
  EmitEndOfAsmFile(M);
  
  delete Mang; Mang = 0;
  DW = 0; MMI = 0;
  
  OutStreamer.Finish();
  return false;
}

void AsmPrinter::SetupMachineFunction(MachineFunction &MF) {
  // Get the function symbol.
  CurrentFnSym = GetGlobalValueSymbol(MF.getFunction());
  IncrementFunctionNumber();

  if (VerboseAsm)
    LI = &getAnalysis<MachineLoopInfo>();
}

namespace {
  // SectionCPs - Keep track the alignment, constpool entries per Section.
  struct SectionCPs {
    const MCSection *S;
    unsigned Alignment;
    SmallVector<unsigned, 4> CPEs;
    SectionCPs(const MCSection *s, unsigned a) : S(s), Alignment(a) {}
  };
}

/// EmitConstantPool - Print to the current output stream assembly
/// representations of the constants in the constant pool MCP. This is
/// used to print out constants which have been "spilled to memory" by
/// the code generator.
///
void AsmPrinter::EmitConstantPool(MachineConstantPool *MCP) {
  const std::vector<MachineConstantPoolEntry> &CP = MCP->getConstants();
  if (CP.empty()) return;

  // Calculate sections for constant pool entries. We collect entries to go into
  // the same section together to reduce amount of section switch statements.
  SmallVector<SectionCPs, 4> CPSections;
  for (unsigned i = 0, e = CP.size(); i != e; ++i) {
    const MachineConstantPoolEntry &CPE = CP[i];
    unsigned Align = CPE.getAlignment();
    
    SectionKind Kind;
    switch (CPE.getRelocationInfo()) {
    default: llvm_unreachable("Unknown section kind");
    case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
    case 1:
      Kind = SectionKind::getReadOnlyWithRelLocal();
      break;
    case 0:
    switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
    case 4:  Kind = SectionKind::getMergeableConst4(); break;
    case 8:  Kind = SectionKind::getMergeableConst8(); break;
    case 16: Kind = SectionKind::getMergeableConst16();break;
    default: Kind = SectionKind::getMergeableConst(); break;
    }
    }

    const MCSection *S = getObjFileLowering().getSectionForConstant(Kind);
    
    // The number of sections are small, just do a linear search from the
    // last section to the first.
    bool Found = false;
    unsigned SecIdx = CPSections.size();
    while (SecIdx != 0) {
      if (CPSections[--SecIdx].S == S) {
        Found = true;
        break;
      }
    }
    if (!Found) {
      SecIdx = CPSections.size();
      CPSections.push_back(SectionCPs(S, Align));
    }

    if (Align > CPSections[SecIdx].Alignment)
      CPSections[SecIdx].Alignment = Align;
    CPSections[SecIdx].CPEs.push_back(i);
  }

  // Now print stuff into the calculated sections.
  for (unsigned i = 0, e = CPSections.size(); i != e; ++i) {
    OutStreamer.SwitchSection(CPSections[i].S);
    EmitAlignment(Log2_32(CPSections[i].Alignment));

    unsigned Offset = 0;
    for (unsigned j = 0, ee = CPSections[i].CPEs.size(); j != ee; ++j) {
      unsigned CPI = CPSections[i].CPEs[j];
      MachineConstantPoolEntry CPE = CP[CPI];

      // Emit inter-object padding for alignment.
      unsigned AlignMask = CPE.getAlignment() - 1;
      unsigned NewOffset = (Offset + AlignMask) & ~AlignMask;
      EmitZeros(NewOffset - Offset);

      const Type *Ty = CPE.getType();
      Offset = NewOffset + TM.getTargetData()->getTypeAllocSize(Ty);

      O << MAI->getPrivateGlobalPrefix() << "CPI" << getFunctionNumber() << '_'
        << CPI << ':';
      if (VerboseAsm) {
        O.PadToColumn(MAI->getCommentColumn());
        O << MAI->getCommentString() << " constant ";
        WriteTypeSymbolic(O, CPE.getType(), MF->getFunction()->getParent());
      }
      O << '\n';
      if (CPE.isMachineConstantPoolEntry())
        EmitMachineConstantPoolValue(CPE.Val.MachineCPVal);
      else
        EmitGlobalConstant(CPE.Val.ConstVal);
    }
  }
}

/// EmitJumpTableInfo - Print assembly representations of the jump tables used
/// by the current function to the current output stream.  
///
void AsmPrinter::EmitJumpTableInfo(MachineJumpTableInfo *MJTI,
                                   MachineFunction &MF) {
  const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
  if (JT.empty()) return;

  bool IsPic = TM.getRelocationModel() == Reloc::PIC_;
  
  // Pick the directive to use to print the jump table entries, and switch to 
  // the appropriate section.
  TargetLowering *LoweringInfo = TM.getTargetLowering();

  const Function *F = MF.getFunction();
  bool JTInDiffSection = false;
  if (F->isWeakForLinker() ||
      (IsPic && !LoweringInfo->usesGlobalOffsetTable())) {
    // In PIC mode, we need to emit the jump table to the same section as the
    // function body itself, otherwise the label differences won't make sense.
    // We should also do if the section name is NULL or function is declared in
    // discardable section.
    OutStreamer.SwitchSection(getObjFileLowering().SectionForGlobal(F, Mang,
                                                                    TM));
  } else {
    // Otherwise, drop it in the readonly section.
    const MCSection *ReadOnlySection = 
      getObjFileLowering().getSectionForConstant(SectionKind::getReadOnly());
    OutStreamer.SwitchSection(ReadOnlySection);
    JTInDiffSection = true;
  }
  
  EmitAlignment(Log2_32(MJTI->getAlignment()));
  
  for (unsigned i = 0, e = JT.size(); i != e; ++i) {
    const std::vector<MachineBasicBlock*> &JTBBs = JT[i].MBBs;
    
    // If this jump table was deleted, ignore it. 
    if (JTBBs.empty()) continue;

    // For PIC codegen, if possible we want to use the SetDirective to reduce
    // the number of relocations the assembler will generate for the jump table.
    // Set directives are all printed before the jump table itself.
    SmallPtrSet<MachineBasicBlock*, 16> EmittedSets;
    if (MAI->getSetDirective() && IsPic)
      for (unsigned ii = 0, ee = JTBBs.size(); ii != ee; ++ii)
        if (EmittedSets.insert(JTBBs[ii]))
          printPICJumpTableSetLabel(i, JTBBs[ii]);
    
    // On some targets (e.g. Darwin) we want to emit two consequtive labels
    // before each jump table.  The first label is never referenced, but tells
    // the assembler and linker the extents of the jump table object.  The
    // second label is actually referenced by the code.
    if (JTInDiffSection && MAI->getLinkerPrivateGlobalPrefix()[0]) {
      O << MAI->getLinkerPrivateGlobalPrefix()
        << "JTI" << getFunctionNumber() << '_' << i << ":\n";
    }
    
    O << MAI->getPrivateGlobalPrefix() << "JTI" << getFunctionNumber() 
      << '_' << i << ":\n";
    
    for (unsigned ii = 0, ee = JTBBs.size(); ii != ee; ++ii) {
      printPICJumpTableEntry(MJTI, JTBBs[ii], i);
      O << '\n';
    }
  }
}

void AsmPrinter::printPICJumpTableEntry(const MachineJumpTableInfo *MJTI,
                                        const MachineBasicBlock *MBB,
                                        unsigned uid)  const {
  bool isPIC = TM.getRelocationModel() == Reloc::PIC_;
  
  // Use JumpTableDirective otherwise honor the entry size from the jump table
  // info.
  const char *JTEntryDirective = MAI->getJumpTableDirective(isPIC);
  bool HadJTEntryDirective = JTEntryDirective != NULL;
  if (!HadJTEntryDirective) {
    JTEntryDirective = MJTI->getEntrySize() == 4 ?
      MAI->getData32bitsDirective() : MAI->getData64bitsDirective();
  }

  O << JTEntryDirective << ' ';

  // If we have emitted set directives for the jump table entries, print 
  // them rather than the entries themselves.  If we're emitting PIC, then
  // emit the table entries as differences between two text section labels.
  // If we're emitting non-PIC code, then emit the entries as direct
  // references to the target basic blocks.
  if (!isPIC) {
    GetMBBSymbol(MBB->getNumber())->print(O, MAI);
  } else if (MAI->getSetDirective()) {
    O << MAI->getPrivateGlobalPrefix() << getFunctionNumber()
      << '_' << uid << "_set_" << MBB->getNumber();
  } else {
    GetMBBSymbol(MBB->getNumber())->print(O, MAI);
    // If the arch uses custom Jump Table directives, don't calc relative to
    // JT
    if (!HadJTEntryDirective) 
      O << '-' << MAI->getPrivateGlobalPrefix() << "JTI"
        << getFunctionNumber() << '_' << uid;
  }
}


/// EmitSpecialLLVMGlobal - Check to see if the specified global is a
/// special global used by LLVM.  If so, emit it and return true, otherwise
/// do nothing and return false.
bool AsmPrinter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
  if (GV->getName() == "llvm.used") {
    if (MAI->getUsedDirective() != 0)    // No need to emit this at all.
      EmitLLVMUsedList(GV->getInitializer());
    return true;
  }

  // Ignore debug and non-emitted data.  This handles llvm.compiler.used.
  if (GV->getSection() == "llvm.metadata" ||
      GV->hasAvailableExternallyLinkage())
    return true;
  
  if (!GV->hasAppendingLinkage()) return false;

  assert(GV->hasInitializer() && "Not a special LLVM global!");
  
  const TargetData *TD = TM.getTargetData();
  unsigned Align = Log2_32(TD->getPointerPrefAlignment());
  if (GV->getName() == "llvm.global_ctors") {
    OutStreamer.SwitchSection(getObjFileLowering().getStaticCtorSection());
    EmitAlignment(Align, 0);
    EmitXXStructorList(GV->getInitializer());
    return true;
  } 
  
  if (GV->getName() == "llvm.global_dtors") {
    OutStreamer.SwitchSection(getObjFileLowering().getStaticDtorSection());
    EmitAlignment(Align, 0);
    EmitXXStructorList(GV->getInitializer());
    return true;
  }
  
  return false;
}

/// EmitLLVMUsedList - For targets that define a MAI::UsedDirective, mark each
/// global in the specified llvm.used list for which emitUsedDirectiveFor
/// is true, as being used with this directive.
void AsmPrinter::EmitLLVMUsedList(Constant *List) {
  const char *Directive = MAI->getUsedDirective();

  // Should be an array of 'i8*'.
  ConstantArray *InitList = dyn_cast<ConstantArray>(List);
  if (InitList == 0) return;
  
  for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
    const GlobalValue *GV =
      dyn_cast<GlobalValue>(InitList->getOperand(i)->stripPointerCasts());
    if (GV && getObjFileLowering().shouldEmitUsedDirectiveFor(GV, Mang)) {
      O << Directive;
      EmitConstantValueOnly(InitList->getOperand(i));
      O << '\n';
    }
  }
}

/// EmitXXStructorList - Emit the ctor or dtor list.  This just prints out the 
/// function pointers, ignoring the init priority.
void AsmPrinter::EmitXXStructorList(Constant *List) {
  // Should be an array of '{ int, void ()* }' structs.  The first value is the
  // init priority, which we ignore.
  if (!isa<ConstantArray>(List)) return;
  ConstantArray *InitList = cast<ConstantArray>(List);
  for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
    if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
      if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.

      if (CS->getOperand(1)->isNullValue())
        return;  // Found a null terminator, exit printing.
      // Emit the function pointer.
      EmitGlobalConstant(CS->getOperand(1));
    }
}


//===----------------------------------------------------------------------===//
/// LEB 128 number encoding.

/// PrintULEB128 - Print a series of hexadecimal values (separated by commas)
/// representing an unsigned leb128 value.
void AsmPrinter::PrintULEB128(unsigned Value) const {
  do {
    unsigned char Byte = static_cast<unsigned char>(Value & 0x7f);
    Value >>= 7;
    if (Value) Byte |= 0x80;
    PrintHex(Byte);
    if (Value) O << ", ";
  } while (Value);
}

/// PrintSLEB128 - Print a series of hexadecimal values (separated by commas)
/// representing a signed leb128 value.
void AsmPrinter::PrintSLEB128(int Value) const {
  int Sign = Value >> (8 * sizeof(Value) - 1);
  bool IsMore;

  do {
    unsigned char Byte = static_cast<unsigned char>(Value & 0x7f);
    Value >>= 7;
    IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
    if (IsMore) Byte |= 0x80;
    PrintHex(Byte);
    if (IsMore) O << ", ";
  } while (IsMore);
}

//===--------------------------------------------------------------------===//
// Emission and print routines
//

/// PrintHex - Print a value as a hexadecimal value.
///
void AsmPrinter::PrintHex(uint64_t Value) const {
  O << "0x";
  O.write_hex(Value);
}

/// EOL - Print a newline character to asm stream.  If a comment is present
/// then it will be printed first.  Comments should not contain '\n'.
void AsmPrinter::EOL() const {
  O << '\n';
}

void AsmPrinter::EOL(const Twine &Comment) const {
  if (VerboseAsm && !Comment.isTriviallyEmpty()) {
    O.PadToColumn(MAI->getCommentColumn());
    O << MAI->getCommentString()
      << ' '
      << Comment;
  }
  O << '\n';
}

static const char *DecodeDWARFEncoding(unsigned Encoding) {
  switch (Encoding) {
  case dwarf::DW_EH_PE_absptr:
    return "absptr";
  case dwarf::DW_EH_PE_omit:
    return "omit";
  case dwarf::DW_EH_PE_pcrel:
    return "pcrel";
  case dwarf::DW_EH_PE_udata4:
    return "udata4";
  case dwarf::DW_EH_PE_udata8:
    return "udata8";
  case dwarf::DW_EH_PE_sdata4:
    return "sdata4";
  case dwarf::DW_EH_PE_sdata8:
    return "sdata8";
  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4:
    return "pcrel udata4";
  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4:
    return "pcrel sdata4";
  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8:
    return "pcrel udata8";
  case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8:
    return "pcrel sdata8";
  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata4:
    return "indirect pcrel udata4";
  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata4:
    return "indirect pcrel sdata4";
  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_udata8:
    return "indirect pcrel udata8";
  case dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |dwarf::DW_EH_PE_sdata8:
    return "indirect pcrel sdata8";
  }

  return 0;
}

void AsmPrinter::EOL(const Twine &Comment, unsigned Encoding) const {
  if (VerboseAsm && !Comment.isTriviallyEmpty()) {
    O.PadToColumn(MAI->getCommentColumn());
    O << MAI->getCommentString()
      << ' '
      << Comment;

    if (const char *EncStr = DecodeDWARFEncoding(Encoding))
      O << " (" << EncStr << ')';
  }
  O << '\n';
}

/// EmitULEB128Bytes - Emit an assembler byte data directive to compose an
/// unsigned leb128 value.
void AsmPrinter::EmitULEB128Bytes(unsigned Value) const {
  if (MAI->hasLEB128()) {
    O << "\t.uleb128\t"
      << Value;
  } else {
    O << MAI->getData8bitsDirective();
    PrintULEB128(Value);
  }
}

/// EmitSLEB128Bytes - print an assembler byte data directive to compose a
/// signed leb128 value.
void AsmPrinter::EmitSLEB128Bytes(int Value) const {
  if (MAI->hasLEB128()) {
    O << "\t.sleb128\t"
      << Value;
  } else {
    O << MAI->getData8bitsDirective();
    PrintSLEB128(Value);
  }
}

/// EmitInt8 - Emit a byte directive and value.
///
void AsmPrinter::EmitInt8(int Value) const {
  O << MAI->getData8bitsDirective();
  PrintHex(Value & 0xFF);
}

/// EmitInt16 - Emit a short directive and value.
///
void AsmPrinter::EmitInt16(int Value) const {
  O << MAI->getData16bitsDirective();
  PrintHex(Value & 0xFFFF);
}

/// EmitInt32 - Emit a long directive and value.
///
void AsmPrinter::EmitInt32(int Value) const {
  O << MAI->getData32bitsDirective();
  PrintHex(Value);
}

/// EmitInt64 - Emit a long long directive and value.
///
void AsmPrinter::EmitInt64(uint64_t Value) const {
  if (MAI->getData64bitsDirective()) {
    O << MAI->getData64bitsDirective();
    PrintHex(Value);
  } else {
    if (TM.getTargetData()->isBigEndian()) {
      EmitInt32(unsigned(Value >> 32)); O << '\n';
      EmitInt32(unsigned(Value));
    } else {
      EmitInt32(unsigned(Value)); O << '\n';
      EmitInt32(unsigned(Value >> 32));
    }
  }
}

/// toOctal - Convert the low order bits of X into an octal digit.
///
static inline char toOctal(int X) {
  return (X&7)+'0';
}

/// printStringChar - Print a char, escaped if necessary.
///
static void printStringChar(formatted_raw_ostream &O, unsigned char C) {
  if (C == '"') {
    O << "\\\"";
  } else if (C == '\\') {
    O << "\\\\";
  } else if (isprint((unsigned char)C)) {
    O << C;
  } else {
    switch(C) {
    case '\b': O << "\\b"; break;
    case '\f': O << "\\f"; break;
    case '\n': O << "\\n"; break;
    case '\r': O << "\\r"; break;
    case '\t': O << "\\t"; break;
    default:
      O << '\\';
      O << toOctal(C >> 6);
      O << toOctal(C >> 3);
      O << toOctal(C >> 0);
      break;
    }
  }
}

/// EmitString - Emit a string with quotes and a null terminator.
/// Special characters are emitted properly.
/// \literal (Eg. '\t') \endliteral
void AsmPrinter::EmitString(const StringRef String) const {
  EmitString(String.data(), String.size());
}

void AsmPrinter::EmitString(const char *String, unsigned Size) const {
  const char* AscizDirective = MAI->getAscizDirective();
  if (AscizDirective)
    O << AscizDirective;
  else
    O << MAI->getAsciiDirective();
  O << '\"';
  for (unsigned i = 0; i < Size; ++i)
    printStringChar(O, String[i]);
  if (AscizDirective)
    O << '\"';
  else
    O << "\\0\"";
}


/// EmitFile - Emit a .file directive.
void AsmPrinter::EmitFile(unsigned Number, StringRef Name) const {
  O << "\t.file\t" << Number << " \"";
  for (unsigned i = 0, N = Name.size(); i < N; ++i)
    printStringChar(O, Name[i]);
  O << '\"';
}


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

// EmitAlignment - Emit an alignment directive to the specified power of
// two boundary.  For example, if you pass in 3 here, you will get an 8
// byte alignment.  If a global value is specified, and if that global has
// an explicit alignment requested, it will unconditionally override the
// alignment request.  However, if ForcedAlignBits is specified, this value
// has final say: the ultimate alignment will be the max of ForcedAlignBits
// and the alignment computed with NumBits and the global.
//
// The algorithm is:
//     Align = NumBits;
//     if (GV && GV->hasalignment) Align = GV->getalignment();
//     Align = std::max(Align, ForcedAlignBits);
//
void AsmPrinter::EmitAlignment(unsigned NumBits, const GlobalValue *GV,
                               unsigned ForcedAlignBits,
                               bool UseFillExpr) const {
  if (GV && GV->getAlignment())
    NumBits = Log2_32(GV->getAlignment());
  NumBits = std::max(NumBits, ForcedAlignBits);
  
  if (NumBits == 0) return;   // No need to emit alignment.
  
  unsigned FillValue = 0;
  if (getCurrentSection()->getKind().isText())
    FillValue = MAI->getTextAlignFillValue();
  
  OutStreamer.EmitValueToAlignment(1 << NumBits, FillValue, 1, 0);
}

/// EmitZeros - Emit a block of zeros.
///
void AsmPrinter::EmitZeros(uint64_t NumZeros, unsigned AddrSpace) const {
  if (NumZeros) {
    if (MAI->getZeroDirective()) {
      O << MAI->getZeroDirective() << NumZeros;
      if (MAI->getZeroDirectiveSuffix())
        O << MAI->getZeroDirectiveSuffix();
      O << '\n';
    } else {
      for (; NumZeros; --NumZeros)
        O << MAI->getData8bitsDirective(AddrSpace) << "0\n";
    }
  }
}

// Print out the specified constant, without a storage class.  Only the
// constants valid in constant expressions can occur here.
void AsmPrinter::EmitConstantValueOnly(const Constant *CV) {
  if (CV->isNullValue() || isa<UndefValue>(CV)) {
    O << '0';
    return;
  }

  if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
    O << CI->getZExtValue();
    return;
  }
  
  if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
    // This is a constant address for a global variable or function. Use the
    // name of the variable or function as the address value.
    GetGlobalValueSymbol(GV)->print(O, MAI);
    return;
  }
  
  if (const BlockAddress *BA = dyn_cast<BlockAddress>(CV)) {
    GetBlockAddressSymbol(BA)->print(O, MAI);
    return;
  }
  
  const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
  if (CE == 0) {
    llvm_unreachable("Unknown constant value!");
    O << '0';
    return;
  }
  
  switch (CE->getOpcode()) {
  case Instruction::ZExt:
  case Instruction::SExt:
  case Instruction::FPTrunc:
  case Instruction::FPExt:
  case Instruction::UIToFP:
  case Instruction::SIToFP:
  case Instruction::FPToUI:
  case Instruction::FPToSI:
  default:
    llvm_unreachable("FIXME: Don't support this constant cast expr");
  case Instruction::GetElementPtr: {
    // generate a symbolic expression for the byte address
    const TargetData *TD = TM.getTargetData();
    const Constant *ptrVal = CE->getOperand(0);
    SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
    int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
                                          idxVec.size());
    if (Offset == 0)
      return EmitConstantValueOnly(ptrVal);
    
    // Truncate/sext the offset to the pointer size.
    if (TD->getPointerSizeInBits() != 64) {
      int SExtAmount = 64-TD->getPointerSizeInBits();
      Offset = (Offset << SExtAmount) >> SExtAmount;
    }
    
    if (Offset)
      O << '(';
    EmitConstantValueOnly(ptrVal);
    if (Offset > 0)
      O << ") + " << Offset;
    else
      O << ") - " << -Offset;
    return;
  }
  case Instruction::BitCast:
    return EmitConstantValueOnly(CE->getOperand(0));

  case Instruction::IntToPtr: {
    // Handle casts to pointers by changing them into casts to the appropriate
    // integer type.  This promotes constant folding and simplifies this code.
    const TargetData *TD = TM.getTargetData();
    Constant *Op = CE->getOperand(0);
    Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(CV->getContext()),
                                      false/*ZExt*/);
    return EmitConstantValueOnly(Op);
  }
    
  case Instruction::PtrToInt: {
    // Support only foldable casts to/from pointers that can be eliminated by
    // changing the pointer to the appropriately sized integer type.
    Constant *Op = CE->getOperand(0);
    const Type *Ty = CE->getType();
    const TargetData *TD = TM.getTargetData();

    // We can emit the pointer value into this slot if the slot is an
    // integer slot greater or equal to the size of the pointer.
    if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
      return EmitConstantValueOnly(Op);

    O << "((";
    EmitConstantValueOnly(Op);
    APInt ptrMask =
      APInt::getAllOnesValue(TD->getTypeAllocSizeInBits(Op->getType()));
    
    SmallString<40> S;
    ptrMask.toStringUnsigned(S);
    O << ") & " << S.str() << ')';
    return;
  }
      
  case Instruction::Trunc:
    // We emit the value and depend on the assembler to truncate the generated
    // expression properly.  This is important for differences between
    // blockaddress labels.  Since the two labels are in the same function, it
    // is reasonable to treat their delta as a 32-bit value.
    return EmitConstantValueOnly(CE->getOperand(0));
      
  case Instruction::Add:
  case Instruction::Sub:
  case Instruction::And:
  case Instruction::Or:
  case Instruction::Xor:
    O << '(';
    EmitConstantValueOnly(CE->getOperand(0));
    O << ')';
    switch (CE->getOpcode()) {
    case Instruction::Add:
     O << " + ";
     break;
    case Instruction::Sub:
     O << " - ";
     break;
    case Instruction::And:
     O << " & ";
     break;
    case Instruction::Or:
     O << " | ";
     break;
    case Instruction::Xor:
     O << " ^ ";
     break;
    default:
     break;
    }
    O << '(';
    EmitConstantValueOnly(CE->getOperand(1));
    O << ')';
    break;
  }
}

/// printAsCString - Print the specified array as a C compatible string, only if
/// the predicate isString is true.
///
static void printAsCString(formatted_raw_ostream &O, const ConstantArray *CVA,
                           unsigned LastElt) {
  assert(CVA->isString() && "Array is not string compatible!");

  O << '\"';
  for (unsigned i = 0; i != LastElt; ++i) {
    unsigned char C =
        (unsigned char)cast<ConstantInt>(CVA->getOperand(i))->getZExtValue();
    printStringChar(O, C);
  }
  O << '\"';
}

/// EmitString - Emit a zero-byte-terminated string constant.
///
void AsmPrinter::EmitString(const ConstantArray *CVA) const {
  unsigned NumElts = CVA->getNumOperands();
  if (MAI->getAscizDirective() && NumElts && 
      cast<ConstantInt>(CVA->getOperand(NumElts-1))->getZExtValue() == 0) {
    O << MAI->getAscizDirective();
    printAsCString(O, CVA, NumElts-1);
  } else {
    O << MAI->getAsciiDirective();
    printAsCString(O, CVA, NumElts);
  }
  O << '\n';
}

void AsmPrinter::EmitGlobalConstantArray(const ConstantArray *CVA,
                                         unsigned AddrSpace) {
  if (CVA->isString()) {
    EmitString(CVA);
  } else { // Not a string.  Print the values in successive locations
    for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
      EmitGlobalConstant(CVA->getOperand(i), AddrSpace);
  }
}

void AsmPrinter::EmitGlobalConstantVector(const ConstantVector *CP) {
  const VectorType *PTy = CP->getType();
  
  for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
    EmitGlobalConstant(CP->getOperand(I));
}

void AsmPrinter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
                                          unsigned AddrSpace) {
  // Print the fields in successive locations. Pad to align if needed!
  const TargetData *TD = TM.getTargetData();
  unsigned Size = TD->getTypeAllocSize(CVS->getType());
  const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
  uint64_t sizeSoFar = 0;
  for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {