MCAssembler.cpp revision 0bcf074867d4d366f7988a219c7a53265fcb4f23 
1//===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#define DEBUG_TYPE "assembler"
11#include "llvm/MC/MCAssembler.h"
12#include "llvm/MC/MCExpr.h"
13#include "llvm/MC/MCSectionMachO.h"
14#include "llvm/MC/MCSymbol.h"
15#include "llvm/MC/MCValue.h"
16#include "llvm/ADT/DenseMap.h"
17#include "llvm/ADT/SmallString.h"
18#include "llvm/ADT/Statistic.h"
19#include "llvm/ADT/StringExtras.h"
20#include "llvm/ADT/StringMap.h"
21#include "llvm/ADT/Twine.h"
22#include "llvm/Support/ErrorHandling.h"
23#include "llvm/Support/MachO.h"
24#include "llvm/Support/raw_ostream.h"
25#include "llvm/Support/Debug.h"
26#include <vector>
27using namespace llvm;
28
29class MachObjectWriter;
30
31STATISTIC(EmittedFragments, "Number of emitted assembler fragments");
32
33// FIXME FIXME FIXME: There are number of places in this file where we convert
34// what is a 64-bit assembler value used for computation into a value in the
35// object file, which may truncate it. We should detect that truncation where
36// invalid and report errors back.
37
38static void WriteFileData(raw_ostream &OS, const MCSectionData &SD,
39                          MachObjectWriter &MOW);
40
41/// isVirtualSection - Check if this is a section which does not actually exist
42/// in the object file.
43static bool isVirtualSection(const MCSection &Section) {
44  // FIXME: Lame.
45  const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
46  unsigned Type = SMO.getTypeAndAttributes() & MCSectionMachO::SECTION_TYPE;
47  return (Type == MCSectionMachO::S_ZEROFILL);
48}
49
50class MachObjectWriter {
51  // See <mach-o/loader.h>.
52  enum {
53    Header_Magic32 = 0xFEEDFACE,
54    Header_Magic64 = 0xFEEDFACF
55  };
56
57  static const unsigned Header32Size = 28;
58  static const unsigned Header64Size = 32;
59  static const unsigned SegmentLoadCommand32Size = 56;
60  static const unsigned Section32Size = 68;
61  static const unsigned SymtabLoadCommandSize = 24;
62  static const unsigned DysymtabLoadCommandSize = 80;
63  static const unsigned Nlist32Size = 12;
64  static const unsigned RelocationInfoSize = 8;
65
66  enum HeaderFileType {
67    HFT_Object = 0x1
68  };
69
70  enum HeaderFlags {
71    HF_SubsectionsViaSymbols = 0x2000
72  };
73
74  enum LoadCommandType {
75    LCT_Segment = 0x1,
76    LCT_Symtab = 0x2,
77    LCT_Dysymtab = 0xb
78  };
79
80  // See <mach-o/nlist.h>.
81  enum SymbolTypeType {
82    STT_Undefined = 0x00,
83    STT_Absolute  = 0x02,
84    STT_Section   = 0x0e
85  };
86
87  enum SymbolTypeFlags {
88    // If any of these bits are set, then the entry is a stab entry number (see
89    // <mach-o/stab.h>. Otherwise the other masks apply.
90    STF_StabsEntryMask = 0xe0,
91
92    STF_TypeMask       = 0x0e,
93    STF_External       = 0x01,
94    STF_PrivateExtern  = 0x10
95  };
96
97  /// IndirectSymbolFlags - Flags for encoding special values in the indirect
98  /// symbol entry.
99  enum IndirectSymbolFlags {
100    ISF_Local    = 0x80000000,
101    ISF_Absolute = 0x40000000
102  };
103
104  /// RelocationFlags - Special flags for addresses.
105  enum RelocationFlags {
106    RF_Scattered = 0x80000000
107  };
108
109  enum RelocationInfoType {
110    RIT_Vanilla             = 0,
111    RIT_Pair                = 1,
112    RIT_Difference          = 2,
113    RIT_PreboundLazyPointer = 3,
114    RIT_LocalDifference     = 4
115  };
116
117  /// MachSymbolData - Helper struct for containing some precomputed information
118  /// on symbols.
119  struct MachSymbolData {
120    MCSymbolData *SymbolData;
121    uint64_t StringIndex;
122    uint8_t SectionIndex;
123
124    // Support lexicographic sorting.
125    bool operator<(const MachSymbolData &RHS) const {
126      const std::string &Name = SymbolData->getSymbol().getName();
127      return Name < RHS.SymbolData->getSymbol().getName();
128    }
129  };
130
131  raw_ostream &OS;
132  bool IsLSB;
133
134public:
135  MachObjectWriter(raw_ostream &_OS, bool _IsLSB = true)
136    : OS(_OS), IsLSB(_IsLSB) {
137  }
138
139  /// @name Helper Methods
140  /// @{
141
142  void Write8(uint8_t Value) {
143    OS << char(Value);
144  }
145
146  void Write16(uint16_t Value) {
147    if (IsLSB) {
148      Write8(uint8_t(Value >> 0));
149      Write8(uint8_t(Value >> 8));
150    } else {
151      Write8(uint8_t(Value >> 8));
152      Write8(uint8_t(Value >> 0));
153    }
154  }
155
156  void Write32(uint32_t Value) {
157    if (IsLSB) {
158      Write16(uint16_t(Value >> 0));
159      Write16(uint16_t(Value >> 16));
160    } else {
161      Write16(uint16_t(Value >> 16));
162      Write16(uint16_t(Value >> 0));
163    }
164  }
165
166  void Write64(uint64_t Value) {
167    if (IsLSB) {
168      Write32(uint32_t(Value >> 0));
169      Write32(uint32_t(Value >> 32));
170    } else {
171      Write32(uint32_t(Value >> 32));
172      Write32(uint32_t(Value >> 0));
173    }
174  }
175
176  void WriteZeros(unsigned N) {
177    const char Zeros[16] = { 0 };
178
179    for (unsigned i = 0, e = N / 16; i != e; ++i)
180      OS << StringRef(Zeros, 16);
181
182    OS << StringRef(Zeros, N % 16);
183  }
184
185  void WriteString(StringRef Str, unsigned ZeroFillSize = 0) {
186    OS << Str;
187    if (ZeroFillSize)
188      WriteZeros(ZeroFillSize - Str.size());
189  }
190
191  /// @}
192
193  void WriteHeader32(unsigned NumLoadCommands, unsigned LoadCommandsSize,
194                     bool SubsectionsViaSymbols) {
195    uint32_t Flags = 0;
196
197    if (SubsectionsViaSymbols)
198      Flags |= HF_SubsectionsViaSymbols;
199
200    // struct mach_header (28 bytes)
201
202    uint64_t Start = OS.tell();
203    (void) Start;
204
205    Write32(Header_Magic32);
206
207    // FIXME: Support cputype.
208    Write32(MachO::CPUTypeI386);
209    // FIXME: Support cpusubtype.
210    Write32(MachO::CPUSubType_I386_ALL);
211    Write32(HFT_Object);
212    Write32(NumLoadCommands);    // Object files have a single load command, the
213                                 // segment.
214    Write32(LoadCommandsSize);
215    Write32(Flags);
216
217    assert(OS.tell() - Start == Header32Size);
218  }
219
220  /// WriteSegmentLoadCommand32 - Write a 32-bit segment load command.
221  ///
222  /// \arg NumSections - The number of sections in this segment.
223  /// \arg SectionDataSize - The total size of the sections.
224  void WriteSegmentLoadCommand32(unsigned NumSections,
225                                 uint64_t VMSize,
226                                 uint64_t SectionDataStartOffset,
227                                 uint64_t SectionDataSize) {
228    // struct segment_command (56 bytes)
229
230    uint64_t Start = OS.tell();
231    (void) Start;
232
233    Write32(LCT_Segment);
234    Write32(SegmentLoadCommand32Size + NumSections * Section32Size);
235
236    WriteString("", 16);
237    Write32(0); // vmaddr
238    Write32(VMSize); // vmsize
239    Write32(SectionDataStartOffset); // file offset
240    Write32(SectionDataSize); // file size
241    Write32(0x7); // maxprot
242    Write32(0x7); // initprot
243    Write32(NumSections);
244    Write32(0); // flags
245
246    assert(OS.tell() - Start == SegmentLoadCommand32Size);
247  }
248
249  void WriteSection32(const MCSectionData &SD, uint64_t FileOffset,
250                      uint64_t RelocationsStart, unsigned NumRelocations) {
251    // The offset is unused for virtual sections.
252    if (isVirtualSection(SD.getSection())) {
253      assert(SD.getFileSize() == 0 && "Invalid file size!");
254      FileOffset = 0;
255    }
256
257    // struct section (68 bytes)
258
259    uint64_t Start = OS.tell();
260    (void) Start;
261
262    // FIXME: cast<> support!
263    const MCSectionMachO &Section =
264      static_cast<const MCSectionMachO&>(SD.getSection());
265    WriteString(Section.getSectionName(), 16);
266    WriteString(Section.getSegmentName(), 16);
267    Write32(SD.getAddress()); // address
268    Write32(SD.getSize()); // size
269    Write32(FileOffset);
270
271    unsigned Flags = Section.getTypeAndAttributes();
272    if (SD.hasInstructions())
273      Flags |= MCSectionMachO::S_ATTR_SOME_INSTRUCTIONS;
274
275    assert(isPowerOf2_32(SD.getAlignment()) && "Invalid alignment!");
276    Write32(Log2_32(SD.getAlignment()));
277    Write32(NumRelocations ? RelocationsStart : 0);
278    Write32(NumRelocations);
279    Write32(Flags);
280    Write32(0); // reserved1
281    Write32(Section.getStubSize()); // reserved2
282
283    assert(OS.tell() - Start == Section32Size);
284  }
285
286  void WriteSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols,
287                              uint32_t StringTableOffset,
288                              uint32_t StringTableSize) {
289    // struct symtab_command (24 bytes)
290
291    uint64_t Start = OS.tell();
292    (void) Start;
293
294    Write32(LCT_Symtab);
295    Write32(SymtabLoadCommandSize);
296    Write32(SymbolOffset);
297    Write32(NumSymbols);
298    Write32(StringTableOffset);
299    Write32(StringTableSize);
300
301    assert(OS.tell() - Start == SymtabLoadCommandSize);
302  }
303
304  void WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
305                                uint32_t NumLocalSymbols,
306                                uint32_t FirstExternalSymbol,
307                                uint32_t NumExternalSymbols,
308                                uint32_t FirstUndefinedSymbol,
309                                uint32_t NumUndefinedSymbols,
310                                uint32_t IndirectSymbolOffset,
311                                uint32_t NumIndirectSymbols) {
312    // struct dysymtab_command (80 bytes)
313
314    uint64_t Start = OS.tell();
315    (void) Start;
316
317    Write32(LCT_Dysymtab);
318    Write32(DysymtabLoadCommandSize);
319    Write32(FirstLocalSymbol);
320    Write32(NumLocalSymbols);
321    Write32(FirstExternalSymbol);
322    Write32(NumExternalSymbols);
323    Write32(FirstUndefinedSymbol);
324    Write32(NumUndefinedSymbols);
325    Write32(0); // tocoff
326    Write32(0); // ntoc
327    Write32(0); // modtaboff
328    Write32(0); // nmodtab
329    Write32(0); // extrefsymoff
330    Write32(0); // nextrefsyms
331    Write32(IndirectSymbolOffset);
332    Write32(NumIndirectSymbols);
333    Write32(0); // extreloff
334    Write32(0); // nextrel
335    Write32(0); // locreloff
336    Write32(0); // nlocrel
337
338    assert(OS.tell() - Start == DysymtabLoadCommandSize);
339  }
340
341  void WriteNlist32(MachSymbolData &MSD) {
342    MCSymbolData &Data = *MSD.SymbolData;
343    const MCSymbol &Symbol = Data.getSymbol();
344    uint8_t Type = 0;
345    uint16_t Flags = Data.getFlags();
346    uint32_t Address = 0;
347
348    // Set the N_TYPE bits. See <mach-o/nlist.h>.
349    //
350    // FIXME: Are the prebound or indirect fields possible here?
351    if (Symbol.isUndefined())
352      Type = STT_Undefined;
353    else if (Symbol.isAbsolute())
354      Type = STT_Absolute;
355    else
356      Type = STT_Section;
357
358    // FIXME: Set STAB bits.
359
360    if (Data.isPrivateExtern())
361      Type |= STF_PrivateExtern;
362
363    // Set external bit.
364    if (Data.isExternal() || Symbol.isUndefined())
365      Type |= STF_External;
366
367    // Compute the symbol address.
368    if (Symbol.isDefined()) {
369      if (Symbol.isAbsolute()) {
370        llvm_unreachable("FIXME: Not yet implemented!");
371      } else {
372        Address = Data.getFragment()->getAddress() + Data.getOffset();
373      }
374    } else if (Data.isCommon()) {
375      // Common symbols are encoded with the size in the address
376      // field, and their alignment in the flags.
377      Address = Data.getCommonSize();
378
379      // Common alignment is packed into the 'desc' bits.
380      if (unsigned Align = Data.getCommonAlignment()) {
381        unsigned Log2Size = Log2_32(Align);
382        assert((1U << Log2Size) == Align && "Invalid 'common' alignment!");
383        if (Log2Size > 15)
384          llvm_report_error("invalid 'common' alignment '" +
385                            Twine(Align) + "'");
386        // FIXME: Keep this mask with the SymbolFlags enumeration.
387        Flags = (Flags & 0xF0FF) | (Log2Size << 8);
388      }
389    }
390
391    // struct nlist (12 bytes)
392
393    Write32(MSD.StringIndex);
394    Write8(Type);
395    Write8(MSD.SectionIndex);
396
397    // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
398    // value.
399    Write16(Flags);
400    Write32(Address);
401  }
402
403  struct MachRelocationEntry {
404    uint32_t Word0;
405    uint32_t Word1;
406  };
407  void ComputeScatteredRelocationInfo(MCAssembler &Asm, MCFragment &Fragment,
408                                      MCAsmFixup &Fixup,
409                                      const MCValue &Target,
410                             DenseMap<const MCSymbol*,MCSymbolData*> &SymbolMap,
411                                     std::vector<MachRelocationEntry> &Relocs) {
412    uint32_t Address = Fragment.getOffset() + Fixup.Offset;
413    unsigned IsPCRel = 0;
414    unsigned Type = RIT_Vanilla;
415
416    // See <reloc.h>.
417    const MCSymbol *A = Target.getSymA();
418    MCSymbolData *SD = SymbolMap.lookup(A);
419    uint32_t Value = SD->getFragment()->getAddress() + SD->getOffset();
420    uint32_t Value2 = 0;
421
422    if (const MCSymbol *B = Target.getSymB()) {
423      Type = RIT_LocalDifference;
424
425      MCSymbolData *SD = SymbolMap.lookup(B);
426      Value2 = SD->getFragment()->getAddress() + SD->getOffset();
427    }
428
429    unsigned Log2Size = Log2_32(Fixup.Size);
430    assert((1U << Log2Size) == Fixup.Size && "Invalid fixup size!");
431
432    // The value which goes in the fixup is current value of the expression.
433    Fixup.FixedValue = Value - Value2 + Target.getConstant();
434
435    MachRelocationEntry MRE;
436    MRE.Word0 = ((Address   <<  0) |
437                 (Type      << 24) |
438                 (Log2Size  << 28) |
439                 (IsPCRel   << 30) |
440                 RF_Scattered);
441    MRE.Word1 = Value;
442    Relocs.push_back(MRE);
443
444    if (Type == RIT_LocalDifference) {
445      Type = RIT_Pair;
446
447      MachRelocationEntry MRE;
448      MRE.Word0 = ((0         <<  0) |
449                   (Type      << 24) |
450                   (Log2Size  << 28) |
451                   (0   << 30) |
452                   RF_Scattered);
453      MRE.Word1 = Value2;
454      Relocs.push_back(MRE);
455    }
456  }
457
458  void ComputeRelocationInfo(MCAssembler &Asm, MCDataFragment &Fragment,
459                             MCAsmFixup &Fixup,
460                             DenseMap<const MCSymbol*,MCSymbolData*> &SymbolMap,
461                             std::vector<MachRelocationEntry> &Relocs) {
462    MCValue Target;
463    if (!Fixup.Value->EvaluateAsRelocatable(Target))
464      llvm_report_error("expected relocatable expression");
465
466    // If this is a difference or a local symbol plus an offset, then we need a
467    // scattered relocation entry.
468    if (Target.getSymB() ||
469        (Target.getSymA() && !Target.getSymA()->isUndefined() &&
470         Target.getConstant()))
471      return ComputeScatteredRelocationInfo(Asm, Fragment, Fixup, Target,
472                                            SymbolMap, Relocs);
473
474    // See <reloc.h>.
475    uint32_t Address = Fragment.getOffset() + Fixup.Offset;
476    uint32_t Value = 0;
477    unsigned Index = 0;
478    unsigned IsPCRel = 0;
479    unsigned IsExtern = 0;
480    unsigned Type = 0;
481
482    if (Target.isAbsolute()) { // constant
483      // SymbolNum of 0 indicates the absolute section.
484      //
485      // FIXME: When is this generated?
486      Type = RIT_Vanilla;
487      Value = 0;
488      llvm_unreachable("FIXME: Not yet implemented!");
489    } else {
490      const MCSymbol *Symbol = Target.getSymA();
491      MCSymbolData *SD = SymbolMap.lookup(Symbol);
492
493      if (Symbol->isUndefined()) {
494        IsExtern = 1;
495        Index = SD->getIndex();
496        Value = 0;
497      } else {
498        // The index is the section ordinal.
499        //
500        // FIXME: O(N)
501        Index = 1;
502        for (MCAssembler::iterator it = Asm.begin(),
503               ie = Asm.end(); it != ie; ++it, ++Index)
504          if (&*it == SD->getFragment()->getParent())
505            break;
506        Value = SD->getFragment()->getAddress() + SD->getOffset();
507      }
508
509      Type = RIT_Vanilla;
510    }
511
512    // The value which goes in the fixup is current value of the expression.
513    Fixup.FixedValue = Value + Target.getConstant();
514
515    unsigned Log2Size = Log2_32(Fixup.Size);
516    assert((1U << Log2Size) == Fixup.Size && "Invalid fixup size!");
517
518    // struct relocation_info (8 bytes)
519    MachRelocationEntry MRE;
520    MRE.Word0 = Address;
521    MRE.Word1 = ((Index     <<  0) |
522                 (IsPCRel   << 24) |
523                 (Log2Size  << 25) |
524                 (IsExtern  << 27) |
525                 (Type      << 28));
526    Relocs.push_back(MRE);
527  }
528
529  void BindIndirectSymbols(MCAssembler &Asm,
530                           DenseMap<const MCSymbol*,MCSymbolData*> &SymbolMap) {
531    // This is the point where 'as' creates actual symbols for indirect symbols
532    // (in the following two passes). It would be easier for us to do this
533    // sooner when we see the attribute, but that makes getting the order in the
534    // symbol table much more complicated than it is worth.
535    //
536    // FIXME: Revisit this when the dust settles.
537
538    // Bind non lazy symbol pointers first.
539    for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
540           ie = Asm.indirect_symbol_end(); it != ie; ++it) {
541      // FIXME: cast<> support!
542      const MCSectionMachO &Section =
543        static_cast<const MCSectionMachO&>(it->SectionData->getSection());
544
545      unsigned Type =
546        Section.getTypeAndAttributes() & MCSectionMachO::SECTION_TYPE;
547      if (Type != MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS)
548        continue;
549
550      MCSymbolData *&Entry = SymbolMap[it->Symbol];
551      if (!Entry)
552        Entry = new MCSymbolData(*it->Symbol, 0, 0, &Asm);
553    }
554
555    // Then lazy symbol pointers and symbol stubs.
556    for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
557           ie = Asm.indirect_symbol_end(); it != ie; ++it) {
558      // FIXME: cast<> support!
559      const MCSectionMachO &Section =
560        static_cast<const MCSectionMachO&>(it->SectionData->getSection());
561
562      unsigned Type =
563        Section.getTypeAndAttributes() & MCSectionMachO::SECTION_TYPE;
564      if (Type != MCSectionMachO::S_LAZY_SYMBOL_POINTERS &&
565          Type != MCSectionMachO::S_SYMBOL_STUBS)
566        continue;
567
568      MCSymbolData *&Entry = SymbolMap[it->Symbol];
569      if (!Entry) {
570        Entry = new MCSymbolData(*it->Symbol, 0, 0, &Asm);
571
572        // Set the symbol type to undefined lazy, but only on construction.
573        //
574        // FIXME: Do not hardcode.
575        Entry->setFlags(Entry->getFlags() | 0x0001);
576      }
577    }
578  }
579
580  /// ComputeSymbolTable - Compute the symbol table data
581  ///
582  /// \param StringTable [out] - The string table data.
583  /// \param StringIndexMap [out] - Map from symbol names to offsets in the
584  /// string table.
585  void ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
586                          std::vector<MachSymbolData> &LocalSymbolData,
587                          std::vector<MachSymbolData> &ExternalSymbolData,
588                          std::vector<MachSymbolData> &UndefinedSymbolData) {
589    // Build section lookup table.
590    DenseMap<const MCSection*, uint8_t> SectionIndexMap;
591    unsigned Index = 1;
592    for (MCAssembler::iterator it = Asm.begin(),
593           ie = Asm.end(); it != ie; ++it, ++Index)
594      SectionIndexMap[&it->getSection()] = Index;
595    assert(Index <= 256 && "Too many sections!");
596
597    // Index 0 is always the empty string.
598    StringMap<uint64_t> StringIndexMap;
599    StringTable += '\x00';
600
601    // Build the symbol arrays and the string table, but only for non-local
602    // symbols.
603    //
604    // The particular order that we collect the symbols and create the string
605    // table, then sort the symbols is chosen to match 'as'. Even though it
606    // doesn't matter for correctness, this is important for letting us diff .o
607    // files.
608    for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
609           ie = Asm.symbol_end(); it != ie; ++it) {
610      const MCSymbol &Symbol = it->getSymbol();
611
612      // Ignore assembler temporaries.
613      if (it->getSymbol().isTemporary())
614        continue;
615
616      if (!it->isExternal() && !Symbol.isUndefined())
617        continue;
618
619      uint64_t &Entry = StringIndexMap[Symbol.getName()];
620      if (!Entry) {
621        Entry = StringTable.size();
622        StringTable += Symbol.getName();
623        StringTable += '\x00';
624      }
625
626      MachSymbolData MSD;
627      MSD.SymbolData = it;
628      MSD.StringIndex = Entry;
629
630      if (Symbol.isUndefined()) {
631        MSD.SectionIndex = 0;
632        UndefinedSymbolData.push_back(MSD);
633      } else if (Symbol.isAbsolute()) {
634        MSD.SectionIndex = 0;
635        ExternalSymbolData.push_back(MSD);
636      } else {
637        MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
638        assert(MSD.SectionIndex && "Invalid section index!");
639        ExternalSymbolData.push_back(MSD);
640      }
641    }
642
643    // Now add the data for local symbols.
644    for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
645           ie = Asm.symbol_end(); it != ie; ++it) {
646      const MCSymbol &Symbol = it->getSymbol();
647
648      // Ignore assembler temporaries.
649      if (it->getSymbol().isTemporary())
650        continue;
651
652      if (it->isExternal() || Symbol.isUndefined())
653        continue;
654
655      uint64_t &Entry = StringIndexMap[Symbol.getName()];
656      if (!Entry) {
657        Entry = StringTable.size();
658        StringTable += Symbol.getName();
659        StringTable += '\x00';
660      }
661
662      MachSymbolData MSD;
663      MSD.SymbolData = it;
664      MSD.StringIndex = Entry;
665
666      if (Symbol.isAbsolute()) {
667        MSD.SectionIndex = 0;
668        LocalSymbolData.push_back(MSD);
669      } else {
670        MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
671        assert(MSD.SectionIndex && "Invalid section index!");
672        LocalSymbolData.push_back(MSD);
673      }
674    }
675
676    // External and undefined symbols are required to be in lexicographic order.
677    std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
678    std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
679
680    // Set the symbol indices.
681    Index = 0;
682    for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
683      LocalSymbolData[i].SymbolData->setIndex(Index++);
684    for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
685      ExternalSymbolData[i].SymbolData->setIndex(Index++);
686    for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
687      UndefinedSymbolData[i].SymbolData->setIndex(Index++);
688
689    // The string table is padded to a multiple of 4.
690    while (StringTable.size() % 4)
691      StringTable += '\x00';
692  }
693
694  void WriteObject(MCAssembler &Asm) {
695    unsigned NumSections = Asm.size();
696
697    // Compute the symbol -> symbol data map.
698    //
699    // FIXME: This should not be here.
700    DenseMap<const MCSymbol*, MCSymbolData *> SymbolMap;
701    for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
702           ie = Asm.symbol_end(); it != ie; ++it)
703      SymbolMap[&it->getSymbol()] = it;
704
705    // Create symbol data for any indirect symbols.
706    BindIndirectSymbols(Asm, SymbolMap);
707
708    // Compute symbol table information.
709    SmallString<256> StringTable;
710    std::vector<MachSymbolData> LocalSymbolData;
711    std::vector<MachSymbolData> ExternalSymbolData;
712    std::vector<MachSymbolData> UndefinedSymbolData;
713    unsigned NumSymbols = Asm.symbol_size();
714
715    // No symbol table command is written if there are no symbols.
716    if (NumSymbols)
717      ComputeSymbolTable(Asm, StringTable, LocalSymbolData, ExternalSymbolData,
718                         UndefinedSymbolData);
719
720    // The section data starts after the header, the segment load command (and
721    // section headers) and the symbol table.
722    unsigned NumLoadCommands = 1;
723    uint64_t LoadCommandsSize =
724      SegmentLoadCommand32Size + NumSections * Section32Size;
725
726    // Add the symbol table load command sizes, if used.
727    if (NumSymbols) {
728      NumLoadCommands += 2;
729      LoadCommandsSize += SymtabLoadCommandSize + DysymtabLoadCommandSize;
730    }
731
732    // Compute the total size of the section data, as well as its file size and
733    // vm size.
734    uint64_t SectionDataStart = Header32Size + LoadCommandsSize;
735    uint64_t SectionDataSize = 0;
736    uint64_t SectionDataFileSize = 0;
737    uint64_t VMSize = 0;
738    for (MCAssembler::iterator it = Asm.begin(),
739           ie = Asm.end(); it != ie; ++it) {
740      MCSectionData &SD = *it;
741
742      VMSize = std::max(VMSize, SD.getAddress() + SD.getSize());
743
744      if (isVirtualSection(SD.getSection()))
745        continue;
746
747      SectionDataSize = std::max(SectionDataSize,
748                                 SD.getAddress() + SD.getSize());
749      SectionDataFileSize = std::max(SectionDataFileSize,
750                                     SD.getAddress() + SD.getFileSize());
751    }
752
753    // The section data is padded to 4 bytes.
754    //
755    // FIXME: Is this machine dependent?
756    unsigned SectionDataPadding = OffsetToAlignment(SectionDataFileSize, 4);
757    SectionDataFileSize += SectionDataPadding;
758
759    // Write the prolog, starting with the header and load command...
760    WriteHeader32(NumLoadCommands, LoadCommandsSize,
761                  Asm.getSubsectionsViaSymbols());
762    WriteSegmentLoadCommand32(NumSections, VMSize,
763                              SectionDataStart, SectionDataSize);
764
765    // ... and then the section headers.
766    //
767    // We also compute the section relocations while we do this. Note that
768    // computing relocation info will also update the fixup to have the correct
769    // value; this will overwrite the appropriate data in the fragment when it
770    // is written.
771    std::vector<MachRelocationEntry> RelocInfos;
772    uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
773    for (MCAssembler::iterator it = Asm.begin(),
774           ie = Asm.end(); it != ie; ++it) {
775      MCSectionData &SD = *it;
776
777      // The assembler writes relocations in the reverse order they were seen.
778      //
779      // FIXME: It is probably more complicated than this.
780      unsigned NumRelocsStart = RelocInfos.size();
781      for (MCSectionData::reverse_iterator it2 = SD.rbegin(),
782             ie2 = SD.rend(); it2 != ie2; ++it2)
783        if (MCDataFragment *DF = dyn_cast<MCDataFragment>(&*it2))
784          for (unsigned i = 0, e = DF->fixup_size(); i != e; ++i)
785            ComputeRelocationInfo(Asm, *DF, DF->getFixups()[e - i - 1],
786                                  SymbolMap, RelocInfos);
787
788      unsigned NumRelocs = RelocInfos.size() - NumRelocsStart;
789      uint64_t SectionStart = SectionDataStart + SD.getAddress();
790      WriteSection32(SD, SectionStart, RelocTableEnd, NumRelocs);
791      RelocTableEnd += NumRelocs * RelocationInfoSize;
792    }
793
794    // Write the symbol table load command, if used.
795    if (NumSymbols) {
796      unsigned FirstLocalSymbol = 0;
797      unsigned NumLocalSymbols = LocalSymbolData.size();
798      unsigned FirstExternalSymbol = FirstLocalSymbol + NumLocalSymbols;
799      unsigned NumExternalSymbols = ExternalSymbolData.size();
800      unsigned FirstUndefinedSymbol = FirstExternalSymbol + NumExternalSymbols;
801      unsigned NumUndefinedSymbols = UndefinedSymbolData.size();
802      unsigned NumIndirectSymbols = Asm.indirect_symbol_size();
803      unsigned NumSymTabSymbols =
804        NumLocalSymbols + NumExternalSymbols + NumUndefinedSymbols;
805      uint64_t IndirectSymbolSize = NumIndirectSymbols * 4;
806      uint64_t IndirectSymbolOffset = 0;
807
808      // If used, the indirect symbols are written after the section data.
809      if (NumIndirectSymbols)
810        IndirectSymbolOffset = RelocTableEnd;
811
812      // The symbol table is written after the indirect symbol data.
813      uint64_t SymbolTableOffset = RelocTableEnd + IndirectSymbolSize;
814
815      // The string table is written after symbol table.
816      uint64_t StringTableOffset =
817        SymbolTableOffset + NumSymTabSymbols * Nlist32Size;
818      WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols,
819                             StringTableOffset, StringTable.size());
820
821      WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
822                               FirstExternalSymbol, NumExternalSymbols,
823                               FirstUndefinedSymbol, NumUndefinedSymbols,
824                               IndirectSymbolOffset, NumIndirectSymbols);
825    }
826
827    // Write the actual section data.
828    for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
829      WriteFileData(OS, *it, *this);
830
831    // Write the extra padding.
832    WriteZeros(SectionDataPadding);
833
834    // Write the relocation entries.
835    for (unsigned i = 0, e = RelocInfos.size(); i != e; ++i) {
836      Write32(RelocInfos[i].Word0);
837      Write32(RelocInfos[i].Word1);
838    }
839
840    // Write the symbol table data, if used.
841    if (NumSymbols) {
842      // Write the indirect symbol entries.
843      for (MCAssembler::indirect_symbol_iterator
844             it = Asm.indirect_symbol_begin(),
845             ie = Asm.indirect_symbol_end(); it != ie; ++it) {
846        // Indirect symbols in the non lazy symbol pointer section have some
847        // special handling.
848        const MCSectionMachO &Section =
849          static_cast<const MCSectionMachO&>(it->SectionData->getSection());
850        unsigned Type =
851          Section.getTypeAndAttributes() & MCSectionMachO::SECTION_TYPE;
852        if (Type == MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS) {
853          // If this symbol is defined and internal, mark it as such.
854          if (it->Symbol->isDefined() &&
855              !SymbolMap.lookup(it->Symbol)->isExternal()) {
856            uint32_t Flags = ISF_Local;
857            if (it->Symbol->isAbsolute())
858              Flags |= ISF_Absolute;
859            Write32(Flags);
860            continue;
861          }
862        }
863
864        Write32(SymbolMap[it->Symbol]->getIndex());
865      }
866
867      // FIXME: Check that offsets match computed ones.
868
869      // Write the symbol table entries.
870      for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
871        WriteNlist32(LocalSymbolData[i]);
872      for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
873        WriteNlist32(ExternalSymbolData[i]);
874      for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
875        WriteNlist32(UndefinedSymbolData[i]);
876
877      // Write the string table.
878      OS << StringTable.str();
879    }
880  }
881
882  void ApplyFixup(const MCAsmFixup &Fixup, MCDataFragment &DF) {
883    // FIXME: Endianness assumption.
884    for (unsigned i = 0; i != Fixup.Size; ++i)
885      DF.getContents()[Fixup.Offset + i] = uint8_t(Fixup.FixedValue >> (i * 8));
886  }
887};
888
889/* *** */
890
891MCFragment::MCFragment() : Kind(FragmentType(~0)) {
892}
893
894MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
895  : Kind(_Kind),
896    Parent(_Parent),
897    FileSize(~UINT64_C(0))
898{
899  if (Parent)
900    Parent->getFragmentList().push_back(this);
901}
902
903MCFragment::~MCFragment() {
904}
905
906uint64_t MCFragment::getAddress() const {
907  assert(getParent() && "Missing Section!");
908  return getParent()->getAddress() + Offset;
909}
910
911/* *** */
912
913MCSectionData::MCSectionData() : Section(0) {}
914
915MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
916  : Section(&_Section),
917    Alignment(1),
918    Address(~UINT64_C(0)),
919    Size(~UINT64_C(0)),
920    FileSize(~UINT64_C(0)),
921    HasInstructions(false)
922{
923  if (A)
924    A->getSectionList().push_back(this);
925}
926
927/* *** */
928
929MCSymbolData::MCSymbolData() : Symbol(0) {}
930
931MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
932                           uint64_t _Offset, MCAssembler *A)
933  : Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
934    IsExternal(false), IsPrivateExtern(false),
935    CommonSize(0), CommonAlign(0), Flags(0), Index(0)
936{
937  if (A)
938    A->getSymbolList().push_back(this);
939}
940
941/* *** */
942
943MCAssembler::MCAssembler(MCContext &_Context, raw_ostream &_OS)
944  : Context(_Context), OS(_OS), SubsectionsViaSymbols(false)
945{
946}
947
948MCAssembler::~MCAssembler() {
949}
950
951void MCAssembler::LayoutSection(MCSectionData &SD) {
952  uint64_t Address = SD.getAddress();
953
954  for (MCSectionData::iterator it = SD.begin(), ie = SD.end(); it != ie; ++it) {
955    MCFragment &F = *it;
956
957    F.setOffset(Address - SD.getAddress());
958
959    // Evaluate fragment size.
960    switch (F.getKind()) {
961    case MCFragment::FT_Align: {
962      MCAlignFragment &AF = cast<MCAlignFragment>(F);
963
964      uint64_t Size = OffsetToAlignment(Address, AF.getAlignment());
965      if (Size > AF.getMaxBytesToEmit())
966        AF.setFileSize(0);
967      else
968        AF.setFileSize(Size);
969      break;
970    }
971
972    case MCFragment::FT_Data:
973    case MCFragment::FT_Fill:
974      F.setFileSize(F.getMaxFileSize());
975      break;
976
977    case MCFragment::FT_Org: {
978      MCOrgFragment &OF = cast<MCOrgFragment>(F);
979
980      MCValue Target;
981      if (!OF.getOffset().EvaluateAsRelocatable(Target))
982        llvm_report_error("expected relocatable expression");
983
984      if (!Target.isAbsolute())
985        llvm_unreachable("FIXME: Not yet implemented!");
986      uint64_t OrgOffset = Target.getConstant();
987      uint64_t Offset = Address - SD.getAddress();
988
989      // FIXME: We need a way to communicate this error.
990      if (OrgOffset < Offset)
991        llvm_report_error("invalid .org offset '" + Twine(OrgOffset) +
992                          "' (at offset '" + Twine(Offset) + "'");
993
994      F.setFileSize(OrgOffset - Offset);
995      break;
996    }
997
998    case MCFragment::FT_ZeroFill: {
999      MCZeroFillFragment &ZFF = cast<MCZeroFillFragment>(F);
1000
1001      // Align the fragment offset; it is safe to adjust the offset freely since
1002      // this is only in virtual sections.
1003      uint64_t Aligned = RoundUpToAlignment(Address, ZFF.getAlignment());
1004      F.setOffset(Aligned - SD.getAddress());
1005
1006      // FIXME: This is misnamed.
1007      F.setFileSize(ZFF.getSize());
1008      break;
1009    }
1010    }
1011
1012    Address += F.getFileSize();
1013  }
1014
1015  // Set the section sizes.
1016  SD.setSize(Address - SD.getAddress());
1017  if (isVirtualSection(SD.getSection()))
1018    SD.setFileSize(0);
1019  else
1020    SD.setFileSize(Address - SD.getAddress());
1021}
1022
1023/// WriteFileData - Write the \arg F data to the output file.
1024static void WriteFileData(raw_ostream &OS, const MCFragment &F,
1025                          MachObjectWriter &MOW) {
1026  uint64_t Start = OS.tell();
1027  (void) Start;
1028
1029  ++EmittedFragments;
1030
1031  // FIXME: Embed in fragments instead?
1032  switch (F.getKind()) {
1033  case MCFragment::FT_Align: {
1034    MCAlignFragment &AF = cast<MCAlignFragment>(F);
1035    uint64_t Count = AF.getFileSize() / AF.getValueSize();
1036
1037    // FIXME: This error shouldn't actually occur (the front end should emit
1038    // multiple .align directives to enforce the semantics it wants), but is
1039    // severe enough that we want to report it. How to handle this?
1040    if (Count * AF.getValueSize() != AF.getFileSize())
1041      llvm_report_error("undefined .align directive, value size '" +
1042                        Twine(AF.getValueSize()) +
1043                        "' is not a divisor of padding size '" +
1044                        Twine(AF.getFileSize()) + "'");
1045
1046    for (uint64_t i = 0; i != Count; ++i) {
1047      switch (AF.getValueSize()) {
1048      default:
1049        assert(0 && "Invalid size!");
1050      case 1: MOW.Write8 (uint8_t (AF.getValue())); break;
1051      case 2: MOW.Write16(uint16_t(AF.getValue())); break;
1052      case 4: MOW.Write32(uint32_t(AF.getValue())); break;
1053      case 8: MOW.Write64(uint64_t(AF.getValue())); break;
1054      }
1055    }
1056    break;
1057  }
1058
1059  case MCFragment::FT_Data: {
1060    MCDataFragment &DF = cast<MCDataFragment>(F);
1061
1062    // Apply the fixups.
1063    //
1064    // FIXME: Move elsewhere.
1065    for (MCDataFragment::const_fixup_iterator it = DF.fixup_begin(),
1066           ie = DF.fixup_end(); it != ie; ++it)
1067      MOW.ApplyFixup(*it, DF);
1068
1069    OS << cast<MCDataFragment>(F).getContents().str();
1070    break;
1071  }
1072
1073  case MCFragment::FT_Fill: {
1074    MCFillFragment &FF = cast<MCFillFragment>(F);
1075    for (uint64_t i = 0, e = FF.getCount(); i != e; ++i) {
1076      switch (FF.getValueSize()) {
1077      default:
1078        assert(0 && "Invalid size!");
1079      case 1: MOW.Write8 (uint8_t (FF.getValue())); break;
1080      case 2: MOW.Write16(uint16_t(FF.getValue())); break;
1081      case 4: MOW.Write32(uint32_t(FF.getValue())); break;
1082      case 8: MOW.Write64(uint64_t(FF.getValue())); break;
1083      }
1084    }
1085    break;
1086  }
1087
1088  case MCFragment::FT_Org: {
1089    MCOrgFragment &OF = cast<MCOrgFragment>(F);
1090
1091    for (uint64_t i = 0, e = OF.getFileSize(); i != e; ++i)
1092      MOW.Write8(uint8_t(OF.getValue()));
1093
1094    break;
1095  }
1096
1097  case MCFragment::FT_ZeroFill: {
1098    assert(0 && "Invalid zero fill fragment in concrete section!");
1099    break;
1100  }
1101  }
1102
1103  assert(OS.tell() - Start == F.getFileSize());
1104}
1105
1106/// WriteFileData - Write the \arg SD data to the output file.
1107static void WriteFileData(raw_ostream &OS, const MCSectionData &SD,
1108                          MachObjectWriter &MOW) {
1109  // Ignore virtual sections.
1110  if (isVirtualSection(SD.getSection())) {
1111    assert(SD.getFileSize() == 0);
1112    return;
1113  }
1114
1115  uint64_t Start = OS.tell();
1116  (void) Start;
1117
1118  for (MCSectionData::const_iterator it = SD.begin(),
1119         ie = SD.end(); it != ie; ++it)
1120    WriteFileData(OS, *it, MOW);
1121
1122  // Add section padding.
1123  assert(SD.getFileSize() >= SD.getSize() && "Invalid section sizes!");
1124  MOW.WriteZeros(SD.getFileSize() - SD.getSize());
1125
1126  assert(OS.tell() - Start == SD.getFileSize());
1127}
1128
1129void MCAssembler::Finish() {
1130  DEBUG_WITH_TYPE("mc-dump", {
1131      llvm::errs() << "assembler backend - pre-layout\n--\n";
1132      dump(); });
1133
1134  // Layout the concrete sections and fragments.
1135  uint64_t Address = 0;
1136  MCSectionData *Prev = 0;
1137  for (iterator it = begin(), ie = end(); it != ie; ++it) {
1138    MCSectionData &SD = *it;
1139
1140    // Skip virtual sections.
1141    if (isVirtualSection(SD.getSection()))
1142      continue;
1143
1144    // Align this section if necessary by adding padding bytes to the previous
1145    // section.
1146    if (uint64_t Pad = OffsetToAlignment(Address, it->getAlignment())) {
1147      assert(Prev && "Missing prev section!");
1148      Prev->setFileSize(Prev->getFileSize() + Pad);
1149      Address += Pad;
1150    }
1151
1152    // Layout the section fragments and its size.
1153    SD.setAddress(Address);
1154    LayoutSection(SD);
1155    Address += SD.getFileSize();
1156
1157    Prev = &SD;
1158  }
1159
1160  // Layout the virtual sections.
1161  for (iterator it = begin(), ie = end(); it != ie; ++it) {
1162    MCSectionData &SD = *it;
1163
1164    if (!isVirtualSection(SD.getSection()))
1165      continue;
1166
1167    SD.setAddress(Address);
1168    LayoutSection(SD);
1169    Address += SD.getSize();
1170  }
1171
1172  DEBUG_WITH_TYPE("mc-dump", {
1173      llvm::errs() << "assembler backend - post-layout\n--\n";
1174      dump(); });
1175
1176  // Write the object file.
1177  MachObjectWriter MOW(OS);
1178  MOW.WriteObject(*this);
1179
1180  OS.flush();
1181}
1182
1183
1184// Debugging methods
1185
1186namespace llvm {
1187
1188raw_ostream &operator<<(raw_ostream &OS, const MCAsmFixup &AF) {
1189  OS << "<MCAsmFixup" << " Offset:" << AF.Offset << " Value:" << AF.Value
1190     << " Size:" << AF.Size << ">";
1191  return OS;
1192}
1193
1194}
1195
1196void MCFragment::dump() {
1197  raw_ostream &OS = llvm::errs();
1198
1199  OS << "<MCFragment " << (void*) this << " Offset:" << Offset
1200     << " FileSize:" << FileSize;
1201
1202  OS << ">";
1203}
1204
1205void MCAlignFragment::dump() {
1206  raw_ostream &OS = llvm::errs();
1207
1208  OS << "<MCAlignFragment ";
1209  this->MCFragment::dump();
1210  OS << "\n       ";
1211  OS << " Alignment:" << getAlignment()
1212     << " Value:" << getValue() << " ValueSize:" << getValueSize()
1213     << " MaxBytesToEmit:" << getMaxBytesToEmit() << ">";
1214}
1215
1216void MCDataFragment::dump() {
1217  raw_ostream &OS = llvm::errs();
1218
1219  OS << "<MCDataFragment ";
1220  this->MCFragment::dump();
1221  OS << "\n       ";
1222  OS << " Contents:[";
1223  for (unsigned i = 0, e = getContents().size(); i != e; ++i) {
1224    if (i) OS << ",";
1225    OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1226  }
1227  OS << "]";
1228
1229  if (!getFixups().empty()) {
1230    OS << ",\n       ";
1231    OS << " Fixups:[";
1232    for (fixup_iterator it = fixup_begin(), ie = fixup_end(); it != ie; ++it) {
1233      if (it != fixup_begin()) OS << ",\n            ";
1234      OS << *it;
1235    }
1236    OS << "]";
1237  }
1238
1239  OS << ">";
1240}
1241
1242void MCFillFragment::dump() {
1243  raw_ostream &OS = llvm::errs();
1244
1245  OS << "<MCFillFragment ";
1246  this->MCFragment::dump();
1247  OS << "\n       ";
1248  OS << " Value:" << getValue() << " ValueSize:" << getValueSize()
1249     << " Count:" << getCount() << ">";
1250}
1251
1252void MCOrgFragment::dump() {
1253  raw_ostream &OS = llvm::errs();
1254
1255  OS << "<MCOrgFragment ";
1256  this->MCFragment::dump();
1257  OS << "\n       ";
1258  OS << " Offset:" << getOffset() << " Value:" << getValue() << ">";
1259}
1260
1261void MCZeroFillFragment::dump() {
1262  raw_ostream &OS = llvm::errs();
1263
1264  OS << "<MCZeroFillFragment ";
1265  this->MCFragment::dump();
1266  OS << "\n       ";
1267  OS << " Size:" << getSize() << " Alignment:" << getAlignment() << ">";
1268}
1269
1270void MCSectionData::dump() {
1271  raw_ostream &OS = llvm::errs();
1272
1273  OS << "<MCSectionData";
1274  OS << " Alignment:" << getAlignment() << " Address:" << Address
1275     << " Size:" << Size << " FileSize:" << FileSize
1276     << " Fragments:[";
1277  for (iterator it = begin(), ie = end(); it != ie; ++it) {
1278    if (it != begin()) OS << ",\n      ";
1279    it->dump();
1280  }
1281  OS << "]>";
1282}
1283
1284void MCSymbolData::dump() {
1285  raw_ostream &OS = llvm::errs();
1286
1287  OS << "<MCSymbolData Symbol:" << getSymbol()
1288     << " Fragment:" << getFragment() << " Offset:" << getOffset()
1289     << " Flags:" << getFlags() << " Index:" << getIndex();
1290  if (isCommon())
1291    OS << " (common, size:" << getCommonSize()
1292       << " align: " << getCommonAlignment() << ")";
1293  if (isExternal())
1294    OS << " (external)";
1295  if (isPrivateExtern())
1296    OS << " (private extern)";
1297  OS << ">";
1298}
1299
1300void MCAssembler::dump() {
1301  raw_ostream &OS = llvm::errs();
1302
1303  OS << "<MCAssembler\n";
1304  OS << "  Sections:[";
1305  for (iterator it = begin(), ie = end(); it != ie; ++it) {
1306    if (it != begin()) OS << ",\n    ";
1307    it->dump();
1308  }
1309  OS << "],\n";
1310  OS << "  Symbols:[";
1311
1312  for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1313    if (it != symbol_begin()) OS << ",\n    ";
1314    it->dump();
1315  }
1316  OS << "]>\n";
1317}
1318