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.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "asm-printer"
#include "llvm/CodeGen/AsmPrinter.h"
#include "DwarfDebug.h"
#include "DwarfException.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Assembly/Writer.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/DebugInfo.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Timer.h"
#include "llvm/Target/Mangler.h"
#include "llvm/Target/TargetFrameLowering.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"
using namespace llvm;

static const char *DWARFGroupName = "DWARF Emission";
static const char *DbgTimerName = "DWARF Debug Writer";
static const char *EHTimerName = "DWARF Exception Writer";

STATISTIC(EmittedInsts, "Number of machine instrs printed");

char AsmPrinter::ID = 0;

typedef DenseMap<GCStrategy*,GCMetadataPrinter*> gcp_map_type;
static gcp_map_type &getGCMap(void *&P) {
  if (P == 0)
    P = new gcp_map_type();
  return *(gcp_map_type*)P;
}


/// getGVAlignmentLog2 - Return the alignment to use for the specified global
/// value in log2 form.  This rounds up to the preferred alignment if possible
/// and legal.
static unsigned getGVAlignmentLog2(const GlobalValue *GV, const DataLayout &TD,
                                   unsigned InBits = 0) {
  unsigned NumBits = 0;
  if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV))
    NumBits = TD.getPreferredAlignmentLog(GVar);

  // If InBits is specified, round it to it.
  if (InBits > NumBits)
    NumBits = InBits;

  // If the GV has a specified alignment, take it into account.
  if (GV->getAlignment() == 0)
    return NumBits;

  unsigned GVAlign = Log2_32(GV->getAlignment());

  // If the GVAlign is larger than NumBits, or if we are required to obey
  // NumBits because the GV has an assigned section, obey it.
  if (GVAlign > NumBits || GV->hasSection())
    NumBits = GVAlign;
  return NumBits;
}

AsmPrinter::AsmPrinter(TargetMachine &tm, MCStreamer &Streamer)
  : MachineFunctionPass(ID),
    TM(tm), MAI(tm.getMCAsmInfo()),
    OutContext(Streamer.getContext()),
    OutStreamer(Streamer),
    LastMI(0), LastFn(0), Counter(~0U), SetCounter(0) {
  DD = 0; DE = 0; MMI = 0; LI = 0;
  CurrentFnSym = CurrentFnSymForSize = 0;
  GCMetadataPrinters = 0;
  VerboseAsm = Streamer.isVerboseAsm();
}

AsmPrinter::~AsmPrinter() {
  assert(DD == 0 && DE == 0 && "Debug/EH info didn't get finalized");

  if (GCMetadataPrinters != 0) {
    gcp_map_type &GCMap = getGCMap(GCMetadataPrinters);

    for (gcp_map_type::iterator I = GCMap.begin(), E = GCMap.end(); I != E; ++I)
      delete I->second;
    delete &GCMap;
    GCMetadataPrinters = 0;
  }

  delete &OutStreamer;
}

/// getFunctionNumber - Return a unique ID for the current function.
///
unsigned AsmPrinter::getFunctionNumber() const {
  return MF->getFunctionNumber();
}

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

/// getDataLayout - Return information about data layout.
const DataLayout &AsmPrinter::getDataLayout() const {
  return *TM.getDataLayout();
}

StringRef AsmPrinter::getTargetTriple() const {
  return TM.getTargetTriple();
}

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



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

bool AsmPrinter::doInitialization(Module &M) {
  OutStreamer.InitStreamer();

  MMI = getAnalysisIfAvailable<MachineModuleInfo>();
  MMI->AnalyzeModule(M);

  // Initialize TargetLoweringObjectFile.
  const_cast<TargetLoweringObjectFile&>(getObjFileLowering())
    .Initialize(OutContext, TM);

  Mang = new Mangler(OutContext, &TM);

  // Allow the target to emit any magic that it wants at the start of the file.
  EmitStartOfAsmFile(M);

  // 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 global came from.
  if (MAI->hasSingleParameterDotFile()) {
    // .file "foo.c"
    OutStreamer.EmitFileDirective(M.getModuleIdentifier());
  }

  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(*this);

  // Emit module-level inline asm if it exists.
  if (!M.getModuleInlineAsm().empty()) {
    OutStreamer.AddComment("Start of file scope inline assembly");
    OutStreamer.AddBlankLine();
    EmitInlineAsm(M.getModuleInlineAsm()+"\n");
    OutStreamer.AddComment("End of file scope inline assembly");
    OutStreamer.AddBlankLine();
  }

  if (MAI->doesSupportDebugInformation())
    DD = new DwarfDebug(this, &M);

  switch (MAI->getExceptionHandlingType()) {
  case ExceptionHandling::None:
    return false;
  case ExceptionHandling::SjLj:
  case ExceptionHandling::DwarfCFI:
    DE = new DwarfCFIException(this);
    return false;
  case ExceptionHandling::ARM:
    DE = new ARMException(this);
    return false;
  case ExceptionHandling::Win64:
    DE = new Win64Exception(this);
    return false;
  }

  llvm_unreachable("Unknown exception type.");
}

void AsmPrinter::EmitLinkage(unsigned Linkage, MCSymbol *GVSym) const {
  switch ((GlobalValue::LinkageTypes)Linkage) {
  case GlobalValue::CommonLinkage:
  case GlobalValue::LinkOnceAnyLinkage:
  case GlobalValue::LinkOnceODRLinkage:
  case GlobalValue::LinkOnceODRAutoHideLinkage:
  case GlobalValue::WeakAnyLinkage:
  case GlobalValue::WeakODRLinkage:
  case GlobalValue::LinkerPrivateWeakLinkage:
    if (MAI->getWeakDefDirective() != 0) {
      // .globl _foo
      OutStreamer.EmitSymbolAttribute(GVSym, MCSA_Global);

      if ((GlobalValue::LinkageTypes)Linkage !=
          GlobalValue::LinkOnceODRAutoHideLinkage)
        // .weak_definition _foo
        OutStreamer.EmitSymbolAttribute(GVSym, MCSA_WeakDefinition);
      else
        OutStreamer.EmitSymbolAttribute(GVSym, MCSA_WeakDefAutoPrivate);
    } else if (MAI->getLinkOnceDirective() != 0) {
      // .globl _foo
      OutStreamer.EmitSymbolAttribute(GVSym, MCSA_Global);
      //NOTE: linkonce is handled by the section the symbol was assigned to.
    } else {
      // .weak _foo
      OutStreamer.EmitSymbolAttribute(GVSym, MCSA_Weak);
    }
    break;
  case GlobalValue::DLLExportLinkage:
  case GlobalValue::AppendingLinkage:
    // FIXME: appending linkage variables should go into a section of
    // their name or something.  For now, just emit them as external.
  case GlobalValue::ExternalLinkage:
    // If external or appending, declare as a global symbol.
    // .globl _foo
    OutStreamer.EmitSymbolAttribute(GVSym, MCSA_Global);
    break;
  case GlobalValue::PrivateLinkage:
  case GlobalValue::InternalLinkage:
  case GlobalValue::LinkerPrivateLinkage:
    break;
  default:
    llvm_unreachable("Unknown linkage type!");
  }
}


/// EmitGlobalVariable - Emit the specified global variable to the .s file.
void AsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
  if (GV->hasInitializer()) {
    // Check to see if this is a special global used by LLVM, if so, emit it.
    if (EmitSpecialLLVMGlobal(GV))
      return;

    if (isVerbose()) {
      WriteAsOperand(OutStreamer.GetCommentOS(), GV,
                     /*PrintType=*/false, GV->getParent());
      OutStreamer.GetCommentOS() << '\n';
    }
  }

  MCSymbol *GVSym = Mang->getSymbol(GV);
  EmitVisibility(GVSym, GV->getVisibility(), !GV->isDeclaration());

  if (!GV->hasInitializer())   // External globals require no extra code.
    return;

  if (MAI->hasDotTypeDotSizeDirective())
    OutStreamer.EmitSymbolAttribute(GVSym, MCSA_ELF_TypeObject);

  SectionKind GVKind = TargetLoweringObjectFile::getKindForGlobal(GV, TM);

  const DataLayout *TD = TM.getDataLayout();
  uint64_t Size = TD->getTypeAllocSize(GV->getType()->getElementType());

  // If the alignment is specified, we *must* obey it.  Overaligning a global
  // with a specified alignment is a prompt way to break globals emitted to
  // sections and expected to be contiguous (e.g. ObjC metadata).
  unsigned AlignLog = getGVAlignmentLog2(GV, *TD);

  // Handle common and BSS local symbols (.lcomm).
  if (GVKind.isCommon() || GVKind.isBSSLocal()) {
    if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
    unsigned Align = 1 << AlignLog;

    // Handle common symbols.
    if (GVKind.isCommon()) {
      if (!getObjFileLowering().getCommDirectiveSupportsAlignment())
        Align = 0;

      // .comm _foo, 42, 4
      OutStreamer.EmitCommonSymbol(GVSym, Size, Align);
      return;
    }

    // Handle local BSS symbols.
    if (MAI->hasMachoZeroFillDirective()) {
      const MCSection *TheSection =
        getObjFileLowering().SectionForGlobal(GV, GVKind, Mang, TM);
      // .zerofill __DATA, __bss, _foo, 400, 5
      OutStreamer.EmitZerofill(TheSection, GVSym, Size, Align);
      return;
    }

    // Use .lcomm only if it supports user-specified alignment.
    // Otherwise, while it would still be correct to use .lcomm in some
    // cases (e.g. when Align == 1), the external assembler might enfore
    // some -unknown- default alignment behavior, which could cause
    // spurious differences between external and integrated assembler.
    // Prefer to simply fall back to .local / .comm in this case.
    if (MAI->getLCOMMDirectiveAlignmentType() != LCOMM::NoAlignment) {
      // .lcomm _foo, 42
      OutStreamer.EmitLocalCommonSymbol(GVSym, Size, Align);
      return;
    }

    if (!getObjFileLowering().getCommDirectiveSupportsAlignment())
      Align = 0;

    // .local _foo
    OutStreamer.EmitSymbolAttribute(GVSym, MCSA_Local);
    // .comm _foo, 42, 4
    OutStreamer.EmitCommonSymbol(GVSym, Size, Align);
    return;
  }

  const MCSection *TheSection =
    getObjFileLowering().SectionForGlobal(GV, GVKind, Mang, TM);

  // Handle the zerofill directive on darwin, which is a special form of BSS
  // emission.
  if (GVKind.isBSSExtern() && MAI->hasMachoZeroFillDirective()) {
    if (Size == 0) Size = 1;  // zerofill of 0 bytes is undefined.

    // .globl _foo
    OutStreamer.EmitSymbolAttribute(GVSym, MCSA_Global);
    // .zerofill __DATA, __common, _foo, 400, 5
    OutStreamer.EmitZerofill(TheSection, GVSym, Size, 1 << AlignLog);
    return;
  }

  // Handle thread local data for mach-o which requires us to output an
  // additional structure of data and mangle the original symbol so that we
  // can reference it later.
  //
  // TODO: This should become an "emit thread local global" method on TLOF.
  // All of this macho specific stuff should be sunk down into TLOFMachO and
  // stuff like "TLSExtraDataSection" should no longer be part of the parent
  // TLOF class.  This will also make it more obvious that stuff like
  // MCStreamer::EmitTBSSSymbol is macho specific and only called from macho
  // specific code.
  if (GVKind.isThreadLocal() && MAI->hasMachoTBSSDirective()) {
    // Emit the .tbss symbol
    MCSymbol *MangSym =
      OutContext.GetOrCreateSymbol(GVSym->getName() + Twine("$tlv$init"));

    if (GVKind.isThreadBSS())
      OutStreamer.EmitTBSSSymbol(TheSection, MangSym, Size, 1 << AlignLog);
    else if (GVKind.isThreadData()) {
      OutStreamer.SwitchSection(TheSection);

      EmitAlignment(AlignLog, GV);
      OutStreamer.EmitLabel(MangSym);

      EmitGlobalConstant(GV->getInitializer());
    }

    OutStreamer.AddBlankLine();

    // Emit the variable struct for the runtime.
    const MCSection *TLVSect
      = getObjFileLowering().getTLSExtraDataSection();

    OutStreamer.SwitchSection(TLVSect);
    // Emit the linkage here.
    EmitLinkage(GV->getLinkage(), GVSym);
    OutStreamer.EmitLabel(GVSym);

    // Three pointers in size:
    //   - __tlv_bootstrap - used to make sure support exists
    //   - spare pointer, used when mapped by the runtime
    //   - pointer to mangled symbol above with initializer
    unsigned PtrSize = TD->getPointerSizeInBits()/8;
    OutStreamer.EmitSymbolValue(GetExternalSymbolSymbol("_tlv_bootstrap"),
				PtrSize);
    OutStreamer.EmitIntValue(0, PtrSize);
    OutStreamer.EmitSymbolValue(MangSym, PtrSize);

    OutStreamer.AddBlankLine();
    return;
  }

  OutStreamer.SwitchSection(TheSection);

  EmitLinkage(GV->getLinkage(), GVSym);
  EmitAlignment(AlignLog, GV);

  OutStreamer.EmitLabel(GVSym);

  EmitGlobalConstant(GV->getInitializer());

  if (MAI->hasDotTypeDotSizeDirective())
    // .size foo, 42
    OutStreamer.EmitELFSize(GVSym, MCConstantExpr::Create(Size, OutContext));

  OutStreamer.AddBlankLine();
}

/// EmitFunctionHeader - This method emits the header for the current
/// function.
void AsmPrinter::EmitFunctionHeader() {
  // Print out constants referenced by the function
  EmitConstantPool();

  // Print the 'header' of function.
  const Function *F = MF->getFunction();

  OutStreamer.SwitchSection(getObjFileLowering().SectionForGlobal(F, Mang, TM));
  EmitVisibility(CurrentFnSym, F->getVisibility());

  EmitLinkage(F->getLinkage(), CurrentFnSym);
  EmitAlignment(MF->getAlignment(), F);

  if (MAI->hasDotTypeDotSizeDirective())
    OutStreamer.EmitSymbolAttribute(CurrentFnSym, MCSA_ELF_TypeFunction);

  if (isVerbose()) {
    WriteAsOperand(OutStreamer.GetCommentOS(), F,
                   /*PrintType=*/false, F->getParent());
    OutStreamer.GetCommentOS() << '\n';
  }

  // Emit the CurrentFnSym.  This is a virtual function to allow targets to
  // do their wild and crazy things as required.
  EmitFunctionEntryLabel();

  // If the function had address-taken blocks that got deleted, then we have
  // references to the dangling symbols.  Emit them at the start of the function
  // so that we don't get references to undefined symbols.
  std::vector<MCSymbol*> DeadBlockSyms;
  MMI->takeDeletedSymbolsForFunction(F, DeadBlockSyms);
  for (unsigned i = 0, e = DeadBlockSyms.size(); i != e; ++i) {
    OutStreamer.AddComment("Address taken block that was later removed");
    OutStreamer.EmitLabel(DeadBlockSyms[i]);
  }

  // Add some workaround for linkonce linkage on Cygwin\MinGW.
  if (MAI->getLinkOnceDirective() != 0 &&
      (F->hasLinkOnceLinkage() || F->hasWeakLinkage())) {
    // FIXME: What is this?
    MCSymbol *FakeStub =
      OutContext.GetOrCreateSymbol(Twine("Lllvm$workaround$fake$stub$")+
                                   CurrentFnSym->getName());
    OutStreamer.EmitLabel(FakeStub);
  }

  // Emit pre-function debug and/or EH information.
  if (DE) {
    NamedRegionTimer T(EHTimerName, DWARFGroupName, TimePassesIsEnabled);
    DE->BeginFunction(MF);
  }
  if (DD) {
    NamedRegionTimer T(DbgTimerName, DWARFGroupName, TimePassesIsEnabled);
    DD->beginFunction(MF);
  }
}

/// EmitFunctionEntryLabel - Emit the label that is the entrypoint for the
/// function.  This can be overridden by targets as required to do custom stuff.
void AsmPrinter::EmitFunctionEntryLabel() {
  // The function label could have already been emitted if two symbols end up
  // conflicting due to asm renaming.  Detect this and emit an error.
  if (CurrentFnSym->isUndefined())
    return OutStreamer.EmitLabel(CurrentFnSym);

  report_fatal_error("'" + Twine(CurrentFnSym->getName()) +
                     "' label emitted multiple times to assembly file");
}

/// emitComments - Pretty-print comments for instructions.
static void emitComments(const MachineInstr &MI, raw_ostream &CommentOS) {
  const MachineFunction *MF = MI.getParent()->getParent();
  const TargetMachine &TM = MF->getTarget();

  // Check for spills and reloads
  int FI;

  const MachineFrameInfo *FrameInfo = MF->getFrameInfo();

  // We assume a single instruction only has a spill or reload, not
  // both.
  const MachineMemOperand *MMO;
  if (TM.getInstrInfo()->isLoadFromStackSlotPostFE(&MI, FI)) {
    if (FrameInfo->isSpillSlotObjectIndex(FI)) {
      MMO = *MI.memoperands_begin();
      CommentOS << MMO->getSize() << "-byte Reload\n";
    }
  } else if (TM.getInstrInfo()->hasLoadFromStackSlot(&MI, MMO, FI)) {
    if (FrameInfo->isSpillSlotObjectIndex(FI))
      CommentOS << MMO->getSize() << "-byte Folded Reload\n";
  } else if (TM.getInstrInfo()->isStoreToStackSlotPostFE(&MI, FI)) {
    if (FrameInfo->isSpillSlotObjectIndex(FI)) {
      MMO = *MI.memoperands_begin();
      CommentOS << MMO->getSize() << "-byte Spill\n";
    }
  } else if (TM.getInstrInfo()->hasStoreToStackSlot(&MI, MMO, FI)) {
    if (FrameInfo->isSpillSlotObjectIndex(FI))
      CommentOS << MMO->getSize() << "-byte Folded Spill\n";
  }

  // Check for spill-induced copies
  if (MI.getAsmPrinterFlag(MachineInstr::ReloadReuse))
    CommentOS << " Reload Reuse\n";
}

/// emitImplicitDef - This method emits the specified machine instruction
/// that is an implicit def.
static void emitImplicitDef(const MachineInstr *MI, AsmPrinter &AP) {
  unsigned RegNo = MI->getOperand(0).getReg();
  AP.OutStreamer.AddComment(Twine("implicit-def: ") +
                            AP.TM.getRegisterInfo()->getName(RegNo));
  AP.OutStreamer.AddBlankLine();
}

static void emitKill(const MachineInstr *MI, AsmPrinter &AP) {
  std::string Str = "kill:";
  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
    const MachineOperand &Op = MI->getOperand(i);
    assert(Op.isReg() && "KILL instruction must have only register operands");
    Str += ' ';
    Str += AP.TM.getRegisterInfo()->getName(Op.getReg());
    Str += (Op.isDef() ? "<def>" : "<kill>");
  }
  AP.OutStreamer.AddComment(Str);
  AP.OutStreamer.AddBlankLine();
}

/// emitDebugValueComment - This method handles the target-independent form
/// of DBG_VALUE, returning true if it was able to do so.  A false return
/// means the target will need to handle MI in EmitInstruction.
static bool emitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
  // This code handles only the 3-operand target-independent form.
  if (MI->getNumOperands() != 3)
    return false;

  SmallString<128> Str;
  raw_svector_ostream OS(Str);
  OS << '\t' << AP.MAI->getCommentString() << "DEBUG_VALUE: ";

  // cast away const; DIetc do not take const operands for some reason.
  DIVariable V(const_cast<MDNode*>(MI->getOperand(2).getMetadata()));
  if (V.getContext().isSubprogram()) {
    StringRef Name = DISubprogram(V.getContext()).getDisplayName();
    if (!Name.empty())
      OS << Name << ":";
  }
  OS << V.getName() << " <- ";

  int64_t Offset = MI->getOperand(1).getImm();
  bool Deref = false;
  // Register or immediate value. Register 0 means undef.
  if (MI->getOperand(0).isFPImm()) {
    APFloat APF = APFloat(MI->getOperand(0).getFPImm()->getValueAPF());
    if (MI->getOperand(0).getFPImm()->getType()->isFloatTy()) {
      OS << (double)APF.convertToFloat();
    } else if (MI->getOperand(0).getFPImm()->getType()->isDoubleTy()) {
      OS << APF.convertToDouble();
    } else {
      // There is no good way to print long double.  Convert a copy to
      // double.  Ah well, it's only a comment.
      bool ignored;
      APF.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven,
                  &ignored);
      OS << "(long double) " << APF.convertToDouble();
    }
  } else if (MI->getOperand(0).isImm()) {
    OS << MI->getOperand(0).getImm();
  } else if (MI->getOperand(0).isCImm()) {
    MI->getOperand(0).getCImm()->getValue().print(OS, false /*isSigned*/);
  } else {
    unsigned Reg;
    if (MI->getOperand(0).isReg()) {
      Reg = MI->getOperand(0).getReg();
      Deref = Offset != 0; // FIXME: use a better sentinel value so that deref
                           // of a reg with a zero offset is valid
    } else {
      assert(MI->getOperand(0).isFI() && "Unknown operand type");
      const TargetFrameLowering *TFI = AP.TM.getFrameLowering();
      Offset += TFI->getFrameIndexReference(*AP.MF, MI->getOperand(0).getIndex(), Reg);
      Deref = true;
    }
    if (Reg == 0) {
      // Suppress offset, it is not meaningful here.
      OS << "undef";
      // NOTE: Want this comment at start of line, don't emit with AddComment.
      AP.OutStreamer.EmitRawText(OS.str());
      return true;
    }
    if (Deref)
      OS << '[';
    OS << AP.TM.getRegisterInfo()->getName(Reg);
  }

  if (Offset)
    OS << '+' << Offset;
  if (Deref)
    OS << ']';
  // NOTE: Want this comment at start of line, don't emit with AddComment.
  AP.OutStreamer.EmitRawText(OS.str());
  return true;
}

AsmPrinter::CFIMoveType AsmPrinter::needsCFIMoves() {
  if (MAI->getExceptionHandlingType() == ExceptionHandling::DwarfCFI &&
      MF->getFunction()->needsUnwindTableEntry())
    return CFI_M_EH;

  if (MMI->hasDebugInfo())
    return CFI_M_Debug;

  return CFI_M_None;
}

bool AsmPrinter::needsSEHMoves() {
  return MAI->getExceptionHandlingType() == ExceptionHandling::Win64 &&
    MF->getFunction()->needsUnwindTableEntry();
}

bool AsmPrinter::needsRelocationsForDwarfStringPool() const {
  return MAI->doesDwarfUseRelocationsAcrossSections();
}

void AsmPrinter::emitPrologLabel(const MachineInstr &MI) {
  MCSymbol *Label = MI.getOperand(0).getMCSymbol();

  if (MAI->getExceptionHandlingType() != ExceptionHandling::DwarfCFI)
    return;

  if (needsCFIMoves() == CFI_M_None)
    return;

  if (MMI->getCompactUnwindEncoding() != 0)
    OutStreamer.EmitCompactUnwindEncoding(MMI->getCompactUnwindEncoding());

  MachineModuleInfo &MMI = MF->getMMI();
  std::vector<MCCFIInstruction> Instructions = MMI.getFrameInstructions();
  bool FoundOne = false;
  (void)FoundOne;
  for (std::vector<MCCFIInstruction>::iterator I = Instructions.begin(),
         E = Instructions.end(); I != E; ++I) {
    if (I->getLabel() == Label) {
      emitCFIInstruction(*I);
      FoundOne = true;
    }
  }
  assert(FoundOne);
}

/// EmitFunctionBody - This method emits the body and trailer for a
/// function.
void AsmPrinter::EmitFunctionBody() {
  // Emit target-specific gunk before the function body.
  EmitFunctionBodyStart();

  bool ShouldPrintDebugScopes = DD && MMI->hasDebugInfo();

  // Print out code for the function.
  bool HasAnyRealCode = false;
  const MachineInstr *LastMI = 0;
  for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
       I != E; ++I) {
    // Print a label for the basic block.
    EmitBasicBlockStart(I);
    for (MachineBasicBlock::const_iterator II = I->begin(), IE = I->end();
         II != IE; ++II) {
      LastMI = II;

      // Print the assembly for the instruction.
      if (!II->isLabel() && !II->isImplicitDef() && !II->isKill() &&
          !II->isDebugValue()) {
        HasAnyRealCode = true;
        ++EmittedInsts;
      }

      if (ShouldPrintDebugScopes) {
        NamedRegionTimer T(DbgTimerName, DWARFGroupName, TimePassesIsEnabled);
        DD->beginInstruction(II);
      }

      if (isVerbose())
        emitComments(*II, OutStreamer.GetCommentOS());

      switch (II->getOpcode()) {
      case TargetOpcode::PROLOG_LABEL:
        emitPrologLabel(*II);
        break;

      case TargetOpcode::EH_LABEL:
      case TargetOpcode::GC_LABEL:
        OutStreamer.EmitLabel(II->getOperand(0).getMCSymbol());
        break;
      case TargetOpcode::INLINEASM:
        EmitInlineAsm(II);
        break;
      case TargetOpcode::DBG_VALUE:
        if (isVerbose()) {
          if (!emitDebugValueComment(II, *this))
            EmitInstruction(II);
        }
        break;
      case TargetOpcode::IMPLICIT_DEF:
        if (isVerbose()) emitImplicitDef(II, *this);
        break;
      case TargetOpcode::KILL:
        if (isVerbose()) emitKill(II, *this);
        break;
      default:
        if (!TM.hasMCUseLoc())
          MCLineEntry::Make(&OutStreamer, getCurrentSection());

        EmitInstruction(II);
        break;
      }

      if (ShouldPrintDebugScopes) {
        NamedRegionTimer T(DbgTimerName, DWARFGroupName, TimePassesIsEnabled);
        DD->endInstruction(II);
      }
    }
  }

  // If the last instruction was a prolog label, then we have a situation where
  // we emitted a prolog but no function body. This results in the ending prolog
  // label equaling the end of function label and an invalid "row" in the
  // FDE. We need to emit a noop in this situation so that the FDE's rows are
  // valid.
  bool RequiresNoop = LastMI && LastMI->isPrologLabel();

  // If the function is empty and the object file uses .subsections_via_symbols,
  // then we need to emit *something* to the function body to prevent the
  // labels from collapsing together.  Just emit a noop.
  if ((MAI->hasSubsectionsViaSymbols() && !HasAnyRealCode) || RequiresNoop) {
    MCInst Noop;
    TM.getInstrInfo()->getNoopForMachoTarget(Noop);
    if (Noop.getOpcode()) {
      OutStreamer.AddComment("avoids zero-length function");
      OutStreamer.EmitInstruction(Noop);
    } else  // Target not mc-ized yet.
      OutStreamer.EmitRawText(StringRef("\tnop\n"));
  }

  const Function *F = MF->getFunction();
  for (Function::const_iterator i = F->begin(), e = F->end(); i != e; ++i) {
    const BasicBlock *BB = i;
    if (!BB->hasAddressTaken())
      continue;
    MCSymbol *Sym = GetBlockAddressSymbol(BB);
    if (Sym->isDefined())
      continue;
    OutStreamer.AddComment("Address of block that was removed by CodeGen");
    OutStreamer.EmitLabel(Sym);
  }

  // Emit target-specific gunk after the function body.
  EmitFunctionBodyEnd();

  // If the target wants a .size directive for the size of the function, emit
  // it.
  if (MAI->hasDotTypeDotSizeDirective()) {
    // Create a symbol for the end of function, so we can get the size as
    // difference between the function label and the temp label.
    MCSymbol *FnEndLabel = OutContext.CreateTempSymbol();
    OutStreamer.EmitLabel(FnEndLabel);

    const MCExpr *SizeExp =
      MCBinaryExpr::CreateSub(MCSymbolRefExpr::Create(FnEndLabel, OutContext),
                              MCSymbolRefExpr::Create(CurrentFnSymForSize,
                                                      OutContext),
                              OutContext);
    OutStreamer.EmitELFSize(CurrentFnSym, SizeExp);
  }

  // Emit post-function debug information.
  if (DD) {
    NamedRegionTimer T(DbgTimerName, DWARFGroupName, TimePassesIsEnabled);
    DD->endFunction(MF);
  }
  if (DE) {
    NamedRegionTimer T(EHTimerName, DWARFGroupName, TimePassesIsEnabled);
    DE->EndFunction();
  }
  MMI->EndFunction();

  // Print out jump tables referenced by the function.
  EmitJumpTableInfo();

  OutStreamer.AddBlankLine();
}

/// getDebugValueLocation - Get location information encoded by DBG_VALUE
/// operands.
MachineLocation AsmPrinter::
getDebugValueLocation(const MachineInstr *MI) const {
  // Target specific DBG_VALUE instructions are handled by each target.
  return MachineLocation();
}

/// EmitDwarfRegOp - Emit dwarf register operation.
void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc) const {
  const TargetRegisterInfo *TRI = TM.getRegisterInfo();
  int Reg = TRI->getDwarfRegNum(MLoc.getReg(), false);

  for (MCSuperRegIterator SR(MLoc.getReg(), TRI); SR.isValid() && Reg < 0;
       ++SR) {
    Reg = TRI->getDwarfRegNum(*SR, false);
    // FIXME: Get the bit range this register uses of the superregister
    // so that we can produce a DW_OP_bit_piece
  }

  // FIXME: Handle cases like a super register being encoded as
  // DW_OP_reg 32 DW_OP_piece 4 DW_OP_reg 33

  // FIXME: We have no reasonable way of handling errors in here. The
  // caller might be in the middle of an dwarf expression. We should
  // probably assert that Reg >= 0 once debug info generation is more mature.

  if (MLoc.isIndirect()) {
    if (Reg < 32) {
      OutStreamer.AddComment(
        dwarf::OperationEncodingString(dwarf::DW_OP_breg0 + Reg));
      EmitInt8(dwarf::DW_OP_breg0 + Reg);
    } else {
      OutStreamer.AddComment("DW_OP_bregx");
      EmitInt8(dwarf::DW_OP_bregx);
      OutStreamer.AddComment(Twine(Reg));
      EmitULEB128(Reg);
    }
    EmitSLEB128(MLoc.getOffset());
  } else {
    if (Reg < 32) {
      OutStreamer.AddComment(
        dwarf::OperationEncodingString(dwarf::DW_OP_reg0 + Reg));
      EmitInt8(dwarf::DW_OP_reg0 + Reg);
    } else {
      OutStreamer.AddComment("DW_OP_regx");
      EmitInt8(dwarf::DW_OP_regx);
      OutStreamer.AddComment(Twine(Reg));
      EmitULEB128(Reg);
    }
  }

  // FIXME: Produce a DW_OP_bit_piece if we used a superregister
}

bool AsmPrinter::doFinalization(Module &M) {
  // Emit global variables.
  for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I)
    EmitGlobalVariable(I);

  // Emit visibility info for declarations
  for (Module::const_iterator I = M.begin(), E = M.end(); I != E; ++I) {
    const Function &F = *I;
    if (!F.isDeclaration())
      continue;
    GlobalValue::VisibilityTypes V = F.getVisibility();
    if (V == GlobalValue::DefaultVisibility)
      continue;

    MCSymbol *Name = Mang->getSymbol(&F);
    EmitVisibility(Name, V, false);
  }

  // Emit module flags.
  SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
  M.getModuleFlagsMetadata(ModuleFlags);
  if (!ModuleFlags.empty())
    getObjFileLowering().emitModuleFlags(OutStreamer, ModuleFlags, Mang, TM);

  // Finalize debug and EH information.
  if (DE) {
    {
      NamedRegionTimer T(EHTimerName, DWARFGroupName, TimePassesIsEnabled);
      DE->EndModule();
    }
    delete DE; DE = 0;
  }
  if (DD) {
    {
      NamedRegionTimer T(DbgTimerName, DWARFGroupName, TimePassesIsEnabled);
      DD->endModule();
    }
    delete DD; DD = 0;
  }

  // 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;
      OutStreamer.EmitSymbolAttribute(Mang->getSymbol(I), MCSA_WeakReference);
    }

    for (Module::const_iterator I = M.begin(), E = M.end(); I != E; ++I) {
      if (!I->hasExternalWeakLinkage()) continue;
      OutStreamer.EmitSymbolAttribute(Mang->getSymbol(I), MCSA_WeakReference);
    }
  }

  if (MAI->hasSetDirective()) {
    OutStreamer.AddBlankLine();
    for (Module::const_alias_iterator I = M.alias_begin(), E = M.alias_end();
         I != E; ++I) {
      MCSymbol *Name = Mang->getSymbol(I);

      const GlobalValue *GV = I->getAliasedGlobal();
      MCSymbol *Target = Mang->getSymbol(GV);

      if (I->hasExternalLinkage() || !MAI->getWeakRefDirective())
        OutStreamer.EmitSymbolAttribute(Name, MCSA_Global);
      else if (I->hasWeakLinkage())
        OutStreamer.EmitSymbolAttribute(Name, MCSA_WeakReference);
      else
        assert(I->hasLocalLinkage() && "Invalid alias linkage");

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

      // Emit the directives as assignments aka .set:
      OutStreamer.EmitAssignment(Name,
                                 MCSymbolRefExpr::Create(Target, OutContext));
    }
  }

  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(*this);

  // 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 (const MCSection *S = MAI->getNonexecutableStackSection(OutContext))
      OutStreamer.SwitchSection(S);

  // 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;
  MMI = 0;

  OutStreamer.Finish();
  OutStreamer.reset();

  return false;
}

void AsmPrinter::SetupMachineFunction(MachineFunction &MF) {
  this->MF = &MF;
  // Get the function symbol.
  CurrentFnSym = Mang->getSymbol(MF.getFunction());
  CurrentFnSymForSize = CurrentFnSym;

  if (isVerbose())
    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