lib/MC/MCAsmStreamer.cpp

//===- lib/MC/MCAsmStreamer.cpp - Text Assembly Output --------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstPrinter.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/FormattedStream.h"
using namespace llvm;

namespace {

class MCAsmStreamer : public MCStreamer {
  formatted_raw_ostream &OS;
  const MCAsmInfo &MAI;
  OwningPtr<MCInstPrinter> InstPrinter;
  OwningPtr<MCCodeEmitter> Emitter;

  SmallString<128> CommentToEmit;
  raw_svector_ostream CommentStream;

  unsigned IsLittleEndian : 1;
  unsigned IsVerboseAsm : 1;
  unsigned ShowInst : 1;

public:
  MCAsmStreamer(MCContext &Context, formatted_raw_ostream &os,
                bool isLittleEndian, bool isVerboseAsm, MCInstPrinter *printer,
                MCCodeEmitter *emitter, bool showInst)
    : MCStreamer(Context), OS(os), MAI(Context.getAsmInfo()),
      InstPrinter(printer), Emitter(emitter), CommentStream(CommentToEmit),
      IsLittleEndian(isLittleEndian), IsVerboseAsm(isVerboseAsm),
      ShowInst(showInst) {
    if (InstPrinter && IsVerboseAsm)
      InstPrinter->setCommentStream(CommentStream);
  }
  ~MCAsmStreamer() {}

  bool isLittleEndian() const { return IsLittleEndian; }

  inline void EmitEOL() {
    // If we don't have any comments, just emit a \n.
    if (!IsVerboseAsm) {
      OS << '\n';
      return;
    }
    EmitCommentsAndEOL();
  }
  void EmitCommentsAndEOL();

  /// isVerboseAsm - Return true if this streamer supports verbose assembly at
  /// all.
  virtual bool isVerboseAsm() const { return IsVerboseAsm; }

  /// hasRawTextSupport - We support EmitRawText.
  virtual bool hasRawTextSupport() const { return true; }

  /// AddComment - Add a comment that can be emitted to the generated .s
  /// file if applicable as a QoI issue to make the output of the compiler
  /// more readable.  This only affects the MCAsmStreamer, and only when
  /// verbose assembly output is enabled.
  virtual void AddComment(const Twine &T);

  /// AddEncodingComment - Add a comment showing the encoding of an instruction.
  virtual void AddEncodingComment(const MCInst &Inst);

  /// GetCommentOS - Return a raw_ostream that comments can be written to.
  /// Unlike AddComment, you are required to terminate comments with \n if you
  /// use this method.
  virtual raw_ostream &GetCommentOS() {
    if (!IsVerboseAsm)
      return nulls();  // Discard comments unless in verbose asm mode.
    return CommentStream;
  }

  /// AddBlankLine - Emit a blank line to a .s file to pretty it up.
  virtual void AddBlankLine() {
    EmitEOL();
  }

  /// @name MCStreamer Interface
  /// @{

  virtual void SwitchSection(const MCSection *Section);

  virtual void InitSections() {
    // FIXME, this is MachO specific, but the testsuite
    // expects this.
    SwitchSection(getContext().getMachOSection("__TEXT", "__text",
                         MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
                         0, SectionKind::getText()));
  }

  virtual void EmitLabel(MCSymbol *Symbol);

  virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);

  virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
  virtual void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol);

  virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);

  virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
  virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol);
  virtual void EmitCOFFSymbolStorageClass(int StorageClass);
  virtual void EmitCOFFSymbolType(int Type);
  virtual void EndCOFFSymbolDef();
  virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value);
  virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                unsigned ByteAlignment);

  /// EmitLocalCommonSymbol - Emit a local common (.lcomm) symbol.
  ///
  /// @param Symbol - The common symbol to emit.
  /// @param Size - The size of the common symbol.
  virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size);

  virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
                            unsigned Size = 0, unsigned ByteAlignment = 0);

  virtual void EmitTBSSSymbol (const MCSection *Section, MCSymbol *Symbol,
                               uint64_t Size, unsigned ByteAlignment = 0);

  virtual void EmitBytes(StringRef Data, unsigned AddrSpace);

  virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);

  virtual void EmitIntValue(uint64_t Value, unsigned Size, unsigned AddrSpace);

  virtual void EmitULEB128Value(const MCExpr *Value, unsigned AddrSpace = 0);

  virtual void EmitSLEB128Value(const MCExpr *Value, unsigned AddrSpace = 0);

  virtual void EmitGPRel32Value(const MCExpr *Value);


  virtual void EmitFill(uint64_t NumBytes, uint8_t FillValue,
                        unsigned AddrSpace);

  virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
                                    unsigned ValueSize = 1,
                                    unsigned MaxBytesToEmit = 0);

  virtual void EmitCodeAlignment(unsigned ByteAlignment,
                                 unsigned MaxBytesToEmit = 0);

  virtual void EmitValueToOffset(const MCExpr *Offset,
                                 unsigned char Value = 0);

  virtual void EmitFileDirective(StringRef Filename);
  virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename);

  virtual void EmitInstruction(const MCInst &Inst);

  /// EmitRawText - If this file is backed by an assembly streamer, this dumps
  /// the specified string in the output .s file.  This capability is
  /// indicated by the hasRawTextSupport() predicate.
  virtual void EmitRawText(StringRef String);

  virtual void Finish();

  /// @}
};

} // end anonymous namespace.

/// AddComment - Add a comment that can be emitted to the generated .s
/// file if applicable as a QoI issue to make the output of the compiler
/// more readable.  This only affects the MCAsmStreamer, and only when
/// verbose assembly output is enabled.
void MCAsmStreamer::AddComment(const Twine &T) {
  if (!IsVerboseAsm) return;

  // Make sure that CommentStream is flushed.
  CommentStream.flush();

  T.toVector(CommentToEmit);
  // Each comment goes on its own line.
  CommentToEmit.push_back('\n');

  // Tell the comment stream that the vector changed underneath it.
  CommentStream.resync();
}

void MCAsmStreamer::EmitCommentsAndEOL() {
  if (CommentToEmit.empty() && CommentStream.GetNumBytesInBuffer() == 0) {
    OS << '\n';
    return;
  }

  CommentStream.flush();
  StringRef Comments = CommentToEmit.str();

  assert(Comments.back() == '\n' &&
         "Comment array not newline terminated");
  do {
    // Emit a line of comments.
    OS.PadToColumn(MAI.getCommentColumn());
    size_t Position = Comments.find('\n');
    OS << MAI.getCommentString() << ' ' << Comments.substr(0, Position) << '\n';

    Comments = Comments.substr(Position+1);
  } while (!Comments.empty());

  CommentToEmit.clear();
  // Tell the comment stream that the vector changed underneath it.
  CommentStream.resync();
}

static inline int64_t truncateToSize(int64_t Value, unsigned Bytes) {
  assert(Bytes && "Invalid size!");
  return Value & ((uint64_t) (int64_t) -1 >> (64 - Bytes * 8));
}

void MCAsmStreamer::SwitchSection(const MCSection *Section) {
  assert(Section && "Cannot switch to a null section!");
  if (Section != CurSection) {
    PrevSection = CurSection;
    CurSection = Section;
    Section->PrintSwitchToSection(MAI, OS);
  }
}

void MCAsmStreamer::EmitLabel(MCSymbol *Symbol) {
  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
  assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
  assert(CurSection && "Cannot emit before setting section!");

  OS << *Symbol << MAI.getLabelSuffix();
  EmitEOL();
  Symbol->setSection(*CurSection);
}

void MCAsmStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
  switch (Flag) {
  default: assert(0 && "Invalid flag!");
  case MCAF_SyntaxUnified:         OS << "\t.syntax unified"; break;
  case MCAF_SubsectionsViaSymbols: OS << ".subsections_via_symbols"; break;
  }
  EmitEOL();
}

void MCAsmStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
  OS << *Symbol << " = " << *Value;
  EmitEOL();

  // FIXME: Lift context changes into super class.
  Symbol->setVariableValue(Value);
}

void MCAsmStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
  OS << ".weakref " << *Alias << ", " << *Symbol;
  EmitEOL();
}

void MCAsmStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
                                        MCSymbolAttr Attribute) {
  switch (Attribute) {
  case MCSA_Invalid: assert(0 && "Invalid symbol attribute");
  case MCSA_ELF_TypeFunction:    /// .type _foo, STT_FUNC  # aka @function
  case MCSA_ELF_TypeIndFunction: /// .type _foo, STT_GNU_IFUNC
  case MCSA_ELF_TypeObject:      /// .type _foo, STT_OBJECT  # aka @object
  case MCSA_ELF_TypeTLS:         /// .type _foo, STT_TLS     # aka @tls_object
  case MCSA_ELF_TypeCommon:      /// .type _foo, STT_COMMON  # aka @common
  case MCSA_ELF_TypeNoType:      /// .type _foo, STT_NOTYPE  # aka @notype
    assert(MAI.hasDotTypeDotSizeDirective() && "Symbol Attr not supported");
    OS << "\t.type\t" << *Symbol << ','
       << ((MAI.getCommentString()[0] != '@') ? '@' : '%');
    switch (Attribute) {
    default: assert(0 && "Unknown ELF .type");
    case MCSA_ELF_TypeFunction:    OS << "function"; break;
    case MCSA_ELF_TypeIndFunction: OS << "gnu_indirect_function"; break;
    case MCSA_ELF_TypeObject:      OS << "object"; break;
    case MCSA_ELF_TypeTLS:         OS << "tls_object"; break;
    case MCSA_ELF_TypeCommon:      OS << "common"; break;
    case MCSA_ELF_TypeNoType:      OS << "no_type"; break;
    }
    EmitEOL();
    return;
  case MCSA_Global: // .globl/.global
    OS << MAI.getGlobalDirective();
    break;
  case MCSA_Hidden:         OS << "\t.hidden\t";          break;
  case MCSA_IndirectSymbol: OS << "\t.indirect_symbol\t"; break;
  case MCSA_Internal:       OS << "\t.internal\t";        break;
  case MCSA_LazyReference:  OS << "\t.lazy_reference\t";  break;
  case MCSA_Local:          OS << "\t.local\t";           break;
  case MCSA_NoDeadStrip:    OS << "\t.no_dead_strip\t";   break;
  case MCSA_PrivateExtern:  OS << "\t.private_extern\t";  break;
  case MCSA_Protected:      OS << "\t.protected\t";       break;
  case MCSA_Reference:      OS << "\t.reference\t";       break;
  case MCSA_Weak:           OS << "\t.weak\t";            break;
  case MCSA_WeakDefinition: OS << "\t.weak_definition\t"; break;
      // .weak_reference
  case MCSA_WeakReference:  OS << MAI.getWeakRefDirective(); break;
  case MCSA_WeakDefAutoPrivate: OS << "\t.weak_def_can_be_hidden\t"; break;
  }

  OS << *Symbol;
  EmitEOL();
}

void MCAsmStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
  OS << ".desc" << ' ' << *Symbol << ',' << DescValue;
  EmitEOL();
}

void MCAsmStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
  OS << "\t.def\t " << *Symbol << ';';
  EmitEOL();
}

void MCAsmStreamer::EmitCOFFSymbolStorageClass (int StorageClass) {
  OS << "\t.scl\t" << StorageClass << ';';
  EmitEOL();
}

void MCAsmStreamer::EmitCOFFSymbolType (int Type) {
  OS << "\t.type\t" << Type << ';';
  EmitEOL();
}

void MCAsmStreamer::EndCOFFSymbolDef() {
  OS << "\t.endef";
  EmitEOL();
}

void MCAsmStreamer::EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
  assert(MAI.hasDotTypeDotSizeDirective());
  OS << "\t.size\t" << *Symbol << ", " << *Value << '\n';
}

void MCAsmStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                     unsigned ByteAlignment) {
  OS << "\t.comm\t" << *Symbol << ',' << Size;
  if (ByteAlignment != 0) {
    if (MAI.getCOMMDirectiveAlignmentIsInBytes())
      OS << ',' << ByteAlignment;
    else
      OS << ',' << Log2_32(ByteAlignment);
  }
  EmitEOL();
}

/// EmitLocalCommonSymbol - Emit a local common (.lcomm) symbol.
///
/// @param Symbol - The common symbol to emit.
/// @param Size - The size of the common symbol.
void MCAsmStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
  assert(MAI.hasLCOMMDirective() && "Doesn't have .lcomm, can't emit it!");
  OS << "\t.lcomm\t" << *Symbol << ',' << Size;
  EmitEOL();
}

void MCAsmStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
                                 unsigned Size, unsigned ByteAlignment) {
  // Note: a .zerofill directive does not switch sections.
  OS << ".zerofill ";

  // This is a mach-o specific directive.
  const MCSectionMachO *MOSection = ((const MCSectionMachO*)Section);
  OS << MOSection->getSegmentName() << "," << MOSection->getSectionName();

  if (Symbol != NULL) {
    OS << ',' << *Symbol << ',' << Size;
    if (ByteAlignment != 0)
      OS << ',' << Log2_32(ByteAlignment);
  }
  EmitEOL();
}

// .tbss sym, size, align
// This depends that the symbol has already been mangled from the original,
// e.g. _a.
void MCAsmStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
                                   uint64_t Size, unsigned ByteAlignment) {
  assert(Symbol != NULL && "Symbol shouldn't be NULL!");
  // Instead of using the Section we'll just use the shortcut.
  // This is a mach-o specific directive and section.
  OS << ".tbss " << *Symbol << ", " << Size;

  // Output align if we have it.  We default to 1 so don't bother printing
  // that.
  if (ByteAlignment > 1) OS << ", " << Log2_32(ByteAlignment);

  EmitEOL();
}

static inline char toOctal(int X) { return (X&7)+'0'; }

static void PrintQuotedString(StringRef Data, raw_ostream &OS) {
  OS << '"';

  for (unsigned i = 0, e = Data.size(); i != e; ++i) {
    unsigned char C = Data[i];
    if (C == '"' || C == '\\') {
      OS << '\\' << (char)C;
      continue;
    }

    if (isprint((unsigned char)C)) {
      OS << (char)C;
      continue;
    }

    switch (C) {
      case '\b': OS << "\\b"; break;
      case '\f': OS << "\\f"; break;
      case '\n': OS << "\\n"; break;
      case '\r': OS << "\\r"; break;
      case '\t': OS << "\\t"; break;
      default:
        OS << '\\';
        OS << toOctal(C >> 6);
        OS << toOctal(C >> 3);
        OS << toOctal(C >> 0);
        break;
    }
  }

  OS << '"';
}


void MCAsmStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
  assert(CurSection && "Cannot emit contents before setting section!");
  if (Data.empty()) return;

  if (Data.size() == 1) {
    OS << MAI.getData8bitsDirective(AddrSpace);
    OS << (unsigned)(unsigned char)Data[0];
    EmitEOL();
    return;
  }

  // If the data ends with 0 and the target supports .asciz, use it, otherwise
  // use .ascii
  if (MAI.getAscizDirective() && Data.back() == 0) {
    OS << MAI.getAscizDirective();
    Data = Data.substr(0, Data.size()-1);
  } else {
    OS << MAI.getAsciiDirective();
  }

  OS << ' ';
  PrintQuotedString(Data, OS);
  EmitEOL();
}

/// EmitIntValue - Special case of EmitValue that avoids the client having
/// to pass in a MCExpr for constant integers.
void MCAsmStreamer::EmitIntValue(uint64_t Value, unsigned Size,
                                 unsigned AddrSpace) {
  assert(CurSection && "Cannot emit contents before setting section!");
  const char *Directive = 0;
  switch (Size) {
  default: break;
  case 1: Directive = MAI.getData8bitsDirective(AddrSpace); break;
  case 2: Directive = MAI.getData16bitsDirective(AddrSpace); break;
  case 4: Directive = MAI.getData32bitsDirective(AddrSpace); break;
  case 8:
    Directive = MAI.getData64bitsDirective(AddrSpace);
    // If the target doesn't support 64-bit data, emit as two 32-bit halves.
    if (Directive) break;
    if (isLittleEndian()) {
      EmitIntValue((uint32_t)(Value >> 0 ), 4, AddrSpace);
      EmitIntValue((uint32_t)(Value >> 32), 4, AddrSpace);
    } else {
      EmitIntValue((uint32_t)(Value >> 32), 4, AddrSpace);
      EmitIntValue((uint32_t)(Value >> 0 ), 4, AddrSpace);
    }
    return;
  }

  assert(Directive && "Invalid size for machine code value!");
  OS << Directive << truncateToSize(Value, Size);
  EmitEOL();
}

void MCAsmStreamer::EmitValue(const MCExpr *Value, unsigned Size,
                              unsigned AddrSpace) {
  assert(CurSection && "Cannot emit contents before setting section!");
  const char *Directive = 0;
  switch (Size) {
  default: break;
  case 1: Directive = MAI.getData8bitsDirective(AddrSpace); break;
  case 2: Directive = MAI.getData16bitsDirective(AddrSpace); break;
  case 4: Directive = MAI.getData32bitsDirective(AddrSpace); break;
  case 8: Directive = MAI.getData64bitsDirective(AddrSpace); break;
  }

  assert(Directive && "Invalid size for machine code value!");
  OS << Directive << *Value;
  EmitEOL();
}

void MCAsmStreamer::EmitULEB128Value(const MCExpr *Value, unsigned AddrSpace) {
  assert(MAI.hasLEB128() && "Cannot print a .uleb");
  OS << ".uleb128 " << *Value;
  EmitEOL();
}

void MCAsmStreamer::EmitSLEB128Value(const MCExpr *Value, unsigned AddrSpace) {
  assert(MAI.hasLEB128() && "Cannot print a .sleb");
  OS << ".sleb128 " << *Value;
  EmitEOL();
}

void MCAsmStreamer::EmitGPRel32Value(const MCExpr *Value) {
  assert(MAI.getGPRel32Directive() != 0);
  OS << MAI.getGPRel32Directive() << *Value;
  EmitEOL();
}


/// EmitFill - Emit NumBytes bytes worth of the value specified by
/// FillValue.  This implements directives such as '.space'.
void MCAsmStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue,
                             unsigned AddrSpace) {
  if (NumBytes == 0) return;

  if (AddrSpace == 0)
    if (const char *ZeroDirective = MAI.getZeroDirective()) {
      OS << ZeroDirective << NumBytes;
      if (FillValue != 0)
        OS << ',' << (int)FillValue;
      EmitEOL();
      return;
    }

  // Emit a byte at a time.
  MCStreamer::EmitFill(NumBytes, FillValue, AddrSpace);
}

void MCAsmStreamer::EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
                                         unsigned ValueSize,
                                         unsigned MaxBytesToEmit) {
  // Some assemblers don't support non-power of two alignments, so we always
  // emit alignments as a power of two if possible.
  if (isPowerOf2_32(ByteAlignment)) {
    switch (ValueSize) {
    default: llvm_unreachable("Invalid size for machine code value!");
    case 1: OS << MAI.getAlignDirective(); break;
    // FIXME: use MAI for this!
    case 2: OS << ".p2alignw "; break;
    case 4: OS << ".p2alignl "; break;
    case 8: llvm_unreachable("Unsupported alignment size!");
    }

    if (MAI.getAlignmentIsInBytes())
      OS << ByteAlignment;
    else
      OS << Log2_32(ByteAlignment);

    if (Value || MaxBytesToEmit) {
      OS << ", 0x";
      OS.write_hex(truncateToSize(Value, ValueSize));

      if (MaxBytesToEmit)
        OS << ", " << MaxBytesToEmit;
    }
    EmitEOL();
    return;
  }

  // Non-power of two alignment.  This is not widely supported by assemblers.
  // FIXME: Parameterize this based on MAI.
  switch (ValueSize) {
  default: llvm_unreachable("Invalid size for machine code value!");
  case 1: OS << ".balign";  break;
  case 2: OS << ".balignw"; break;
  case 4: OS << ".balignl"; break;
  case 8: llvm_unreachable("Unsupported alignment size!");
  }

  OS << ' ' << ByteAlignment;
  OS << ", " << truncateToSize(Value, ValueSize);
  if (MaxBytesToEmit)
    OS << ", " << MaxBytesToEmit;
  EmitEOL();
}

void MCAsmStreamer::EmitCodeAlignment(unsigned ByteAlignment,
                                      unsigned MaxBytesToEmit) {
  // Emit with a text fill value.
  EmitValueToAlignment(ByteAlignment, MAI.getTextAlignFillValue(),
                       1, MaxBytesToEmit);
}

void MCAsmStreamer::EmitValueToOffset(const MCExpr *Offset,
                                      unsigned char Value) {
  // FIXME: Verify that Offset is associated with the current section.
  OS << ".org " << *Offset << ", " << (unsigned) Value;
  EmitEOL();
}


void MCAsmStreamer::EmitFileDirective(StringRef Filename) {
  assert(MAI.hasSingleParameterDotFile());
  OS << "\t.file\t";
  PrintQuotedString(Filename, OS);
  EmitEOL();
}

void MCAsmStreamer::EmitDwarfFileDirective(unsigned FileNo, StringRef Filename){
  OS << "\t.file\t" << FileNo << ' ';
  PrintQuotedString(Filename, OS);
  EmitEOL();
}

void MCAsmStreamer::AddEncodingComment(const MCInst &Inst) {
  raw_ostream &OS = GetCommentOS();
  SmallString<256> Code;
  SmallVector<MCFixup, 4> Fixups;
  raw_svector_ostream VecOS(Code);
  Emitter->EncodeInstruction(Inst, VecOS, Fixups);
  VecOS.flush();

  // If we are showing fixups, create symbolic markers in the encoded
  // representation. We do this by making a per-bit map to the fixup item index,
  // then trying to display it as nicely as possible.
  SmallVector<uint8_t, 64> FixupMap;
  FixupMap.resize(Code.size() * 8);
  for (unsigned i = 0, e = Code.size() * 8; i != e; ++i)
    FixupMap[i] = 0;

  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
    MCFixup &F = Fixups[i];
    const MCFixupKindInfo &Info = Emitter->getFixupKindInfo(F.getKind());
    for (unsigned j = 0; j != Info.TargetSize; ++j) {
      unsigned Index = F.getOffset() * 8 + Info.TargetOffset + j;
      assert(Index < Code.size() * 8 && "Invalid offset in fixup!");
      FixupMap[Index] = 1 + i;
    }
  }

  OS << "encoding: [";
  for (unsigned i = 0, e = Code.size(); i != e; ++i) {
    if (i)
      OS << ',';

    // See if all bits are the same map entry.
    uint8_t MapEntry = FixupMap[i * 8 + 0];
    for (unsigned j = 1; j != 8; ++j) {
      if (FixupMap[i * 8 + j] == MapEntry)
        continue;

      MapEntry = uint8_t(~0U);
      break;
    }

    if (MapEntry != uint8_t(~0U)) {
      if (MapEntry == 0) {
        OS << format("0x%02x", uint8_t(Code[i]));
      } else {
        assert(Code[i] == 0 && "Encoder wrote into fixed up bit!");
        OS << char('A' + MapEntry - 1);
      }
    } else {
      // Otherwise, write out in binary.
      OS << "0b";
      for (unsigned j = 8; j--;) {
        unsigned Bit = (Code[i] >> j) & 1;
        if (uint8_t MapEntry = FixupMap[i * 8 + j]) {
          assert(Bit == 0 && "Encoder wrote into fixed up bit!");
          OS << char('A' + MapEntry - 1);
        } else
          OS << Bit;
      }
    }
  }
  OS << "]\n";

  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
    MCFixup &F = Fixups[i];
    const MCFixupKindInfo &Info = Emitter->getFixupKindInfo(F.getKind());
    OS << "  fixup " << char('A' + i) << " - " << "offset: " << F.getOffset()
       << ", value: " << *F.getValue() << ", kind: " << Info.Name << "\n";
  }
}

void MCAsmStreamer::EmitInstruction(const MCInst &Inst) {
  assert(CurSection && "Cannot emit contents before setting section!");

  // Show the encoding in a comment if we have a code emitter.
  if (Emitter)
    AddEncodingComment(Inst);

  // Show the MCInst if enabled.
  if (ShowInst) {
    Inst.dump_pretty(GetCommentOS(), &MAI, InstPrinter.get(), "\n ");
    GetCommentOS() << "\n";
  }

  // If we have an AsmPrinter, use that to print, otherwise print the MCInst.
  if (InstPrinter)
    InstPrinter->printInst(&Inst, OS);
  else
    Inst.print(OS, &MAI);
  EmitEOL();
}

/// EmitRawText - If this file is backed by an assembly streamer, this dumps
/// the specified string in the output .s file.  This capability is
/// indicated by the hasRawTextSupport() predicate.
void MCAsmStreamer::EmitRawText(StringRef String) {
  if (!String.empty() && String.back() == '\n')
    String = String.substr(0, String.size()-1);
  OS << String;
  EmitEOL();
}

void MCAsmStreamer::Finish() {
}

MCStreamer *llvm::createAsmStreamer(MCContext &Context,
                                    formatted_raw_ostream &OS,
                                    bool isLittleEndian,
                                    bool isVerboseAsm, MCInstPrinter *IP,
                                    MCCodeEmitter *CE, bool ShowInst) {
  return new MCAsmStreamer(Context, OS, isLittleEndian, isVerboseAsm,
                           IP, CE, ShowInst);
}