llvm.org GIT mirror llvm / 3f6eb74 lib / CodeGen / MachOWriter.cpp
3f6eb74

Tree @3f6eb74 (Download .tar.gz)

MachOWriter.cpp @3f6eb74raw · history · blame

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
//===-- MachOWriter.cpp - Target-independent Mach-O Writer code -----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by Nate Begeman and is distributed under the
// University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the target-independent Mach-O writer.  This file writes
// out the Mach-O file in the following order:
//
//  #1 FatHeader (universal-only)
//  #2 FatArch (universal-only, 1 per universal arch)
//  Per arch:
//    #3 Header
//    #4 Load Commands
//    #5 Sections
//    #6 Relocations
//    #7 Symbols
//    #8 Strings
//
//===----------------------------------------------------------------------===//

#include "MachOWriter.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/CodeGen/FileWriters.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Target/TargetJITInfo.h"
#include "llvm/Support/Mangler.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/OutputBuffer.h"
#include "llvm/Support/Streams.h"
#include <algorithm>
using namespace llvm;

/// AddMachOWriter - Concrete function to add the Mach-O writer to the function
/// pass manager.
MachineCodeEmitter *llvm::AddMachOWriter(FunctionPassManager &FPM,
                                         std::ostream &O,
                                         TargetMachine &TM) {
  MachOWriter *MOW = new MachOWriter(O, TM);
  FPM.add(MOW);
  return &MOW->getMachineCodeEmitter();
}

//===----------------------------------------------------------------------===//
//                       MachOCodeEmitter Implementation
//===----------------------------------------------------------------------===//

namespace llvm {
  /// MachOCodeEmitter - This class is used by the MachOWriter to emit the code 
  /// for functions to the Mach-O file.
  class MachOCodeEmitter : public MachineCodeEmitter {
    MachOWriter &MOW;

    /// Target machine description.
    TargetMachine &TM;

    /// is64Bit/isLittleEndian - This information is inferred from the target
    /// machine directly, indicating what header values and flags to set.
    bool is64Bit, isLittleEndian;

    /// Relocations - These are the relocations that the function needs, as
    /// emitted.
    std::vector<MachineRelocation> Relocations;
    
    /// CPLocations - This is a map of constant pool indices to offsets from the
    /// start of the section for that constant pool index.
    std::vector<intptr_t> CPLocations;

    /// CPSections - This is a map of constant pool indices to the MachOSection
    /// containing the constant pool entry for that index.
    std::vector<unsigned> CPSections;

    /// JTLocations - This is a map of jump table indices to offsets from the
    /// start of the section for that jump table index.
    std::vector<intptr_t> JTLocations;

    /// MBBLocations - This vector is a mapping from MBB ID's to their address.
    /// It is filled in by the StartMachineBasicBlock callback and queried by
    /// the getMachineBasicBlockAddress callback.
    std::vector<intptr_t> MBBLocations;
    
  public:
    MachOCodeEmitter(MachOWriter &mow) : MOW(mow), TM(MOW.TM) {
      is64Bit = TM.getTargetData()->getPointerSizeInBits() == 64;
      isLittleEndian = TM.getTargetData()->isLittleEndian();
    }

    virtual void startFunction(MachineFunction &MF);
    virtual bool finishFunction(MachineFunction &MF);

    virtual void addRelocation(const MachineRelocation &MR) {
      Relocations.push_back(MR);
    }
    
    void emitConstantPool(MachineConstantPool *MCP);
    void emitJumpTables(MachineJumpTableInfo *MJTI);
    
    virtual intptr_t getConstantPoolEntryAddress(unsigned Index) const {
      assert(CPLocations.size() > Index && "CP not emitted!");
      return CPLocations[Index];
    }
    virtual intptr_t getJumpTableEntryAddress(unsigned Index) const {
      assert(JTLocations.size() > Index && "JT not emitted!");
      return JTLocations[Index];
    }

    virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) {
      if (MBBLocations.size() <= (unsigned)MBB->getNumber())
        MBBLocations.resize((MBB->getNumber()+1)*2);
      MBBLocations[MBB->getNumber()] = getCurrentPCOffset();
    }

    virtual intptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const {
      assert(MBBLocations.size() > (unsigned)MBB->getNumber() && 
             MBBLocations[MBB->getNumber()] && "MBB not emitted!");
      return MBBLocations[MBB->getNumber()];
    }

    /// JIT SPECIFIC FUNCTIONS - DO NOT IMPLEMENT THESE HERE!
    virtual void startFunctionStub(unsigned StubSize, unsigned Alignment = 1) {
      assert(0 && "JIT specific function called!");
      abort();
    }
    virtual void *finishFunctionStub(const Function *F) {
      assert(0 && "JIT specific function called!");
      abort();
      return 0;
    }
  };
}

/// startFunction - This callback is invoked when a new machine function is
/// about to be emitted.
void MachOCodeEmitter::startFunction(MachineFunction &MF) {
  const TargetData *TD = TM.getTargetData();
  const Function *F = MF.getFunction();

  // Align the output buffer to the appropriate alignment, power of 2.
  unsigned FnAlign = F->getAlignment();
  unsigned TDAlign = TD->getPrefTypeAlignment(F->getType());
  unsigned Align = Log2_32(std::max(FnAlign, TDAlign));
  assert(!(Align & (Align-1)) && "Alignment is not a power of two!");

  // Get the Mach-O Section that this function belongs in.
  MachOWriter::MachOSection *MOS = MOW.getTextSection();
  
  // FIXME: better memory management
  MOS->SectionData.reserve(4096);
  BufferBegin = &MOS->SectionData[0];
  BufferEnd = BufferBegin + MOS->SectionData.capacity();

  // Upgrade the section alignment if required.
  if (MOS->align < Align) MOS->align = Align;

  // Round the size up to the correct alignment for starting the new function.
  if ((MOS->size & ((1 << Align) - 1)) != 0) {
    MOS->size += (1 << Align);
    MOS->size &= ~((1 << Align) - 1);
  }

  // FIXME: Using MOS->size directly here instead of calculating it from the
  // output buffer size (impossible because the code emitter deals only in raw
  // bytes) forces us to manually synchronize size and write padding zero bytes
  // to the output buffer for all non-text sections.  For text sections, we do
  // not synchonize the output buffer, and we just blow up if anyone tries to
  // write non-code to it.  An assert should probably be added to
  // AddSymbolToSection to prevent calling it on the text section.
  CurBufferPtr = BufferBegin + MOS->size;

  // Clear per-function data structures.
  CPLocations.clear();
  CPSections.clear();
  JTLocations.clear();
  MBBLocations.clear();
}

/// finishFunction - This callback is invoked after the function is completely
/// finished.
bool MachOCodeEmitter::finishFunction(MachineFunction &MF) {
  // Get the Mach-O Section that this function belongs in.
  MachOWriter::MachOSection *MOS = MOW.getTextSection();

  // Get a symbol for the function to add to the symbol table
  // FIXME: it seems like we should call something like AddSymbolToSection
  // in startFunction rather than changing the section size and symbol n_value
  // here.
  const GlobalValue *FuncV = MF.getFunction();
  MachOSym FnSym(FuncV, MOW.Mang->getValueName(FuncV), MOS->Index, TM);
  FnSym.n_value = MOS->size;
  MOS->size = CurBufferPtr - BufferBegin;
  
  // Emit constant pool to appropriate section(s)
  emitConstantPool(MF.getConstantPool());

  // Emit jump tables to appropriate section
  emitJumpTables(MF.getJumpTableInfo());
  
  // If we have emitted any relocations to function-specific objects such as 
  // basic blocks, constant pools entries, or jump tables, record their
  // addresses now so that we can rewrite them with the correct addresses
  // later.
  for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
    MachineRelocation &MR = Relocations[i];
    intptr_t Addr;

    if (MR.isBasicBlock()) {
      Addr = getMachineBasicBlockAddress(MR.getBasicBlock());
      MR.setConstantVal(MOS->Index);
      MR.setResultPointer((void*)Addr);
    } else if (MR.isJumpTableIndex()) {
      Addr = getJumpTableEntryAddress(MR.getJumpTableIndex());
      MR.setConstantVal(MOW.getJumpTableSection()->Index);
      MR.setResultPointer((void*)Addr);
    } else if (MR.isConstantPoolIndex()) {
      Addr = getConstantPoolEntryAddress(MR.getConstantPoolIndex());
      MR.setConstantVal(CPSections[MR.getConstantPoolIndex()]);
      MR.setResultPointer((void*)Addr);
    } else if (MR.isGlobalValue()) {
      // FIXME: This should be a set or something that uniques
      MOW.PendingGlobals.push_back(MR.getGlobalValue());
    } else {
      assert(0 && "Unhandled relocation type");
    }
    MOS->Relocations.push_back(MR);
  }
  Relocations.clear();
  
  // Finally, add it to the symtab.
  MOW.SymbolTable.push_back(FnSym);
  return false;
}

/// emitConstantPool - For each constant pool entry, figure out which section
/// the constant should live in, allocate space for it, and emit it to the 
/// Section data buffer.
void MachOCodeEmitter::emitConstantPool(MachineConstantPool *MCP) {
  const std::vector<MachineConstantPoolEntry> &CP = MCP->getConstants();
  if (CP.empty()) return;

  // FIXME: handle PIC codegen
  bool isPIC = TM.getRelocationModel() == Reloc::PIC_;
  assert(!isPIC && "PIC codegen not yet handled for mach-o jump tables!");

  // Although there is no strict necessity that I am aware of, we will do what
  // gcc for OS X does and put each constant pool entry in a section of constant
  // objects of a certain size.  That means that float constants go in the
  // literal4 section, and double objects go in literal8, etc.
  //
  // FIXME: revisit this decision if we ever do the "stick everything into one
  // "giant object for PIC" optimization.
  for (unsigned i = 0, e = CP.size(); i != e; ++i) {
    const Type *Ty = CP[i].getType();
    unsigned Size = TM.getTargetData()->getTypeSize(Ty);

    MachOWriter::MachOSection *Sec = MOW.getConstSection(CP[i].Val.ConstVal);
    OutputBuffer SecDataOut(Sec->SectionData, is64Bit, isLittleEndian);

    CPLocations.push_back(Sec->SectionData.size());
    CPSections.push_back(Sec->Index);
    
    // FIXME: remove when we have unified size + output buffer
    Sec->size += Size;

    // Allocate space in the section for the global.
    // FIXME: need alignment?
    // FIXME: share between here and AddSymbolToSection?
    for (unsigned j = 0; j < Size; ++j)
      SecDataOut.outbyte(0);

    MOW.InitMem(CP[i].Val.ConstVal, &Sec->SectionData[0], CPLocations[i],
                TM.getTargetData(), Sec->Relocations);
  }
}

/// emitJumpTables - Emit all the jump tables for a given jump table info
/// record to the appropriate section.
void MachOCodeEmitter::emitJumpTables(MachineJumpTableInfo *MJTI) {
  const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
  if (JT.empty()) return;

  // FIXME: handle PIC codegen
  bool isPIC = TM.getRelocationModel() == Reloc::PIC_;
  assert(!isPIC && "PIC codegen not yet handled for mach-o jump tables!");

  MachOWriter::MachOSection *Sec = MOW.getJumpTableSection();
  unsigned TextSecIndex = MOW.getTextSection()->Index;
  OutputBuffer SecDataOut(Sec->SectionData, is64Bit, isLittleEndian);

  for (unsigned i = 0, e = JT.size(); i != e; ++i) {
    // For each jump table, record its offset from the start of the section,
    // reserve space for the relocations to the MBBs, and add the relocations.
    const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
    JTLocations.push_back(Sec->SectionData.size());
    for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi) {
      MachineRelocation MR(MOW.GetJTRelocation(Sec->SectionData.size(),
                                               MBBs[mi]));
      MR.setResultPointer((void *)JTLocations[i]);
      MR.setConstantVal(TextSecIndex);
      Sec->Relocations.push_back(MR);
      SecDataOut.outaddr(0);
    }
  }
  // FIXME: remove when we have unified size + output buffer
  Sec->size = Sec->SectionData.size();
}

//===----------------------------------------------------------------------===//
//                          MachOWriter Implementation
//===----------------------------------------------------------------------===//

char MachOWriter::ID = 0;
MachOWriter::MachOWriter(std::ostream &o, TargetMachine &tm) 
  : MachineFunctionPass((intptr_t)&ID), O(o), TM(tm) {
  is64Bit = TM.getTargetData()->getPointerSizeInBits() == 64;
  isLittleEndian = TM.getTargetData()->isLittleEndian();

  // Create the machine code emitter object for this target.
  MCE = new MachOCodeEmitter(*this);
}

MachOWriter::~MachOWriter() {
  delete MCE;
}

void MachOWriter::AddSymbolToSection(MachOSection *Sec, GlobalVariable *GV) {
  const Type *Ty = GV->getType()->getElementType();
  unsigned Size = TM.getTargetData()->getTypeSize(Ty);
  unsigned Align = GV->getAlignment();
  if (Align == 0)
    Align = TM.getTargetData()->getPrefTypeAlignment(Ty);
  
  // Reserve space in the .bss section for this symbol while maintaining the
  // desired section alignment, which must be at least as much as required by
  // this symbol.
  OutputBuffer SecDataOut(Sec->SectionData, is64Bit, isLittleEndian);

  if (Align) {
    uint64_t OrigSize = Sec->size;
    Align = Log2_32(Align);
    Sec->align = std::max(unsigned(Sec->align), Align);
    Sec->size = (Sec->size + Align - 1) & ~(Align-1);
    
    // Add alignment padding to buffer as well.
    // FIXME: remove when we have unified size + output buffer
    unsigned AlignedSize = Sec->size - OrigSize;
    for (unsigned i = 0; i < AlignedSize; ++i)
      SecDataOut.outbyte(0);
  }
  // Globals without external linkage apparently do not go in the symbol table.
  if (GV->getLinkage() != GlobalValue::InternalLinkage) {
    MachOSym Sym(GV, Mang->getValueName(GV), Sec->Index, TM);
    Sym.n_value = Sec->size;
    SymbolTable.push_back(Sym);
  }

  // Record the offset of the symbol, and then allocate space for it.
  // FIXME: remove when we have unified size + output buffer
  Sec->size += Size;
  
  // Now that we know what section the GlovalVariable is going to be emitted 
  // into, update our mappings.
  // FIXME: We may also need to update this when outputting non-GlobalVariable
  // GlobalValues such as functions.
  GVSection[GV] = Sec;
  GVOffset[GV] = Sec->SectionData.size();
  
  // Allocate space in the section for the global.
  for (unsigned i = 0; i < Size; ++i)
    SecDataOut.outbyte(0);
}

void MachOWriter::EmitGlobal(GlobalVariable *GV) {
  const Type *Ty = GV->getType()->getElementType();
  unsigned Size = TM.getTargetData()->getTypeSize(Ty);
  bool NoInit = !GV->hasInitializer();
  
  // If this global has a zero initializer, it is part of the .bss or common
  // section.
  if (NoInit || GV->getInitializer()->isNullValue()) {
    // If this global is part of the common block, add it now.  Variables are
    // part of the common block if they are zero initialized and allowed to be
    // merged with other symbols.
    if (NoInit || GV->hasLinkOnceLinkage() || GV->hasWeakLinkage()) {
      MachOSym ExtOrCommonSym(GV, Mang->getValueName(GV), MachOSym::NO_SECT,TM);
      // For undefined (N_UNDF) external (N_EXT) types, n_value is the size in
      // bytes of the symbol.
      ExtOrCommonSym.n_value = Size;
      SymbolTable.push_back(ExtOrCommonSym);
      // Remember that we've seen this symbol
      GVOffset[GV] = Size;
      return;
    }
    // Otherwise, this symbol is part of the .bss section.
    MachOSection *BSS = getBSSSection();
    AddSymbolToSection(BSS, GV);
    return;
  }
  
  // Scalar read-only data goes in a literal section if the scalar is 4, 8, or
  // 16 bytes, or a cstring.  Other read only data goes into a regular const
  // section.  Read-write data goes in the data section.
  MachOSection *Sec = GV->isConstant() ? getConstSection(GV->getInitializer()) : 
                                         getDataSection();
  AddSymbolToSection(Sec, GV);
  InitMem(GV->getInitializer(), &Sec->SectionData[0], GVOffset[GV],
          TM.getTargetData(), Sec->Relocations);
}


bool MachOWriter::runOnMachineFunction(MachineFunction &MF) {
  // Nothing to do here, this is all done through the MCE object.
  return false;
}

bool MachOWriter::doInitialization(Module &M) {
  // Set the magic value, now that we know the pointer size and endianness
  Header.setMagic(isLittleEndian, is64Bit);

  // Set the file type
  // FIXME: this only works for object files, we do not support the creation
  //        of dynamic libraries or executables at this time.
  Header.filetype = MachOHeader::MH_OBJECT;

  Mang = new Mangler(M);
  return false;
}

/// doFinalization - Now that the module has been completely processed, emit
/// the Mach-O file to 'O'.
bool MachOWriter::doFinalization(Module &M) {
  // FIXME: we don't handle debug info yet, we should probably do that.

  // Okay, the.text section has been completed, build the .data, .bss, and 
  // "common" sections next.
  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I)
    EmitGlobal(I);
  
  // Emit the header and load commands.
  EmitHeaderAndLoadCommands();

  // Emit the various sections and their relocation info.
  EmitSections();

  // Write the symbol table and the string table to the end of the file.
  O.write((char*)&SymT[0], SymT.size());
  O.write((char*)&StrT[0], StrT.size());

  // We are done with the abstract symbols.
  SectionList.clear();
  SymbolTable.clear();
  DynamicSymbolTable.clear();

  // Release the name mangler object.
  delete Mang; Mang = 0;
  return false;
}

void MachOWriter::EmitHeaderAndLoadCommands() {
  // Step #0: Fill in the segment load command size, since we need it to figure
  //          out the rest of the header fields
  MachOSegment SEG("", is64Bit);
  SEG.nsects  = SectionList.size();
  SEG.cmdsize = SEG.cmdSize(is64Bit) + 
                SEG.nsects * SectionList[0]->cmdSize(is64Bit);
  
  // Step #1: calculate the number of load commands.  We always have at least
  //          one, for the LC_SEGMENT load command, plus two for the normal
  //          and dynamic symbol tables, if there are any symbols.
  Header.ncmds = SymbolTable.empty() ? 1 : 3;
  
  // Step #2: calculate the size of the load commands
  Header.sizeofcmds = SEG.cmdsize;
  if (!SymbolTable.empty())
    Header.sizeofcmds += SymTab.cmdsize + DySymTab.cmdsize;
    
  // Step #3: write the header to the file
  // Local alias to shortenify coming code.
  DataBuffer &FH = Header.HeaderData;
  OutputBuffer FHOut(FH, is64Bit, isLittleEndian);

  FHOut.outword(Header.magic);
  FHOut.outword(TM.getMachOWriterInfo()->getCPUType());
  FHOut.outword(TM.getMachOWriterInfo()->getCPUSubType());
  FHOut.outword(Header.filetype);
  FHOut.outword(Header.ncmds);
  FHOut.outword(Header.sizeofcmds);
  FHOut.outword(Header.flags);
  if (is64Bit)
    FHOut.outword(Header.reserved);
  
  // Step #4: Finish filling in the segment load command and write it out
  for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
         E = SectionList.end(); I != E; ++I)
    SEG.filesize += (*I)->size;

  SEG.vmsize = SEG.filesize;
  SEG.fileoff = Header.cmdSize(is64Bit) + Header.sizeofcmds;
  
  FHOut.outword(SEG.cmd);
  FHOut.outword(SEG.cmdsize);
  FHOut.outstring(SEG.segname, 16);
  FHOut.outaddr(SEG.vmaddr);
  FHOut.outaddr(SEG.vmsize);
  FHOut.outaddr(SEG.fileoff);
  FHOut.outaddr(SEG.filesize);
  FHOut.outword(SEG.maxprot);
  FHOut.outword(SEG.initprot);
  FHOut.outword(SEG.nsects);
  FHOut.outword(SEG.flags);
  
  // Step #5: Finish filling in the fields of the MachOSections 
  uint64_t currentAddr = 0;
  for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
         E = SectionList.end(); I != E; ++I) {
    MachOSection *MOS = *I;
    MOS->addr = currentAddr;
    MOS->offset = currentAddr + SEG.fileoff;

    // FIXME: do we need to do something with alignment here?
    currentAddr += MOS->size;
  }
  
  // Step #6: Emit the symbol table to temporary buffers, so that we know the
  // size of the string table when we write the next load command.  This also
  // sorts and assigns indices to each of the symbols, which is necessary for
  // emitting relocations to externally-defined objects.
  BufferSymbolAndStringTable();
  
  // Step #7: Calculate the number of relocations for each section and write out
  // the section commands for each section
  currentAddr += SEG.fileoff;
  for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
         E = SectionList.end(); I != E; ++I) {
    MachOSection *MOS = *I;
    // Convert the relocations to target-specific relocations, and fill in the
    // relocation offset for this section.
    CalculateRelocations(*MOS);
    MOS->reloff = MOS->nreloc ? currentAddr : 0;
    currentAddr += MOS->nreloc * 8;
    
    // write the finalized section command to the output buffer
    FHOut.outstring(MOS->sectname, 16);
    FHOut.outstring(MOS->segname, 16);
    FHOut.outaddr(MOS->addr);
    FHOut.outaddr(MOS->size);
    FHOut.outword(MOS->offset);
    FHOut.outword(MOS->align);
    FHOut.outword(MOS->reloff);
    FHOut.outword(MOS->nreloc);
    FHOut.outword(MOS->flags);
    FHOut.outword(MOS->reserved1);
    FHOut.outword(MOS->reserved2);
    if (is64Bit)
      FHOut.outword(MOS->reserved3);
  }
  
  // Step #8: Emit LC_SYMTAB/LC_DYSYMTAB load commands
  SymTab.symoff  = currentAddr;
  SymTab.nsyms   = SymbolTable.size();
  SymTab.stroff  = SymTab.symoff + SymT.size();
  SymTab.strsize = StrT.size();
  FHOut.outword(SymTab.cmd);
  FHOut.outword(SymTab.cmdsize);
  FHOut.outword(SymTab.symoff);
  FHOut.outword(SymTab.nsyms);
  FHOut.outword(SymTab.stroff);
  FHOut.outword(SymTab.strsize);

  // FIXME: set DySymTab fields appropriately
  // We should probably just update these in BufferSymbolAndStringTable since
  // thats where we're partitioning up the different kinds of symbols.
  FHOut.outword(DySymTab.cmd);
  FHOut.outword(DySymTab.cmdsize);
  FHOut.outword(DySymTab.ilocalsym);
  FHOut.outword(DySymTab.nlocalsym);
  FHOut.outword(DySymTab.iextdefsym);
  FHOut.outword(DySymTab.nextdefsym);
  FHOut.outword(DySymTab.iundefsym);
  FHOut.outword(DySymTab.nundefsym);
  FHOut.outword(DySymTab.tocoff);
  FHOut.outword(DySymTab.ntoc);
  FHOut.outword(DySymTab.modtaboff);
  FHOut.outword(DySymTab.nmodtab);
  FHOut.outword(DySymTab.extrefsymoff);
  FHOut.outword(DySymTab.nextrefsyms);
  FHOut.outword(DySymTab.indirectsymoff);
  FHOut.outword(DySymTab.nindirectsyms);
  FHOut.outword(DySymTab.extreloff);
  FHOut.outword(DySymTab.nextrel);
  FHOut.outword(DySymTab.locreloff);
  FHOut.outword(DySymTab.nlocrel);
  
  O.write((char*)&FH[0], FH.size());
}

/// EmitSections - Now that we have constructed the file header and load
/// commands, emit the data for each section to the file.
void MachOWriter::EmitSections() {
  for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
         E = SectionList.end(); I != E; ++I)
    // Emit the contents of each section
    O.write((char*)&(*I)->SectionData[0], (*I)->size);
  for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
         E = SectionList.end(); I != E; ++I)
    // Emit the relocation entry data for each section.
    O.write((char*)&(*I)->RelocBuffer[0], (*I)->RelocBuffer.size());
}

/// PartitionByLocal - Simple boolean predicate that returns true if Sym is
/// a local symbol rather than an external symbol.
bool MachOWriter::PartitionByLocal(const MachOSym &Sym) {
  return (Sym.n_type & (MachOSym::N_EXT | MachOSym::N_PEXT)) == 0;
}

/// PartitionByDefined - Simple boolean predicate that returns true if Sym is
/// defined in this module.
bool MachOWriter::PartitionByDefined(const MachOSym &Sym) {
  // FIXME: Do N_ABS or N_INDR count as defined?
  return (Sym.n_type & MachOSym::N_SECT) == MachOSym::N_SECT;
}

/// BufferSymbolAndStringTable - Sort the symbols we encountered and assign them
/// each a string table index so that they appear in the correct order in the
/// output file.
void MachOWriter::BufferSymbolAndStringTable() {
  // The order of the symbol table is:
  // 1. local symbols
  // 2. defined external symbols (sorted by name)
  // 3. undefined external symbols (sorted by name)
  
  // Before sorting the symbols, check the PendingGlobals for any undefined
  // globals that need to be put in the symbol table.
  for (std::vector<GlobalValue*>::iterator I = PendingGlobals.begin(),
         E = PendingGlobals.end(); I != E; ++I) {
    if (GVOffset[*I] == 0 && GVSection[*I] == 0) {
      MachOSym UndfSym(*I, Mang->getValueName(*I), MachOSym::NO_SECT, TM);
      SymbolTable.push_back(UndfSym);
      GVOffset[*I] = -1;
    }
  }
  
  // Sort the symbols by name, so that when we partition the symbols by scope
  // of definition, we won't have to sort by name within each partition.
  std::sort(SymbolTable.begin(), SymbolTable.end(), MachOSymCmp());

  // Parition the symbol table entries so that all local symbols come before 
  // all symbols with external linkage. { 1 | 2 3 }
  std::partition(SymbolTable.begin(), SymbolTable.end(), PartitionByLocal);
  
  // Advance iterator to beginning of external symbols and partition so that
  // all external symbols defined in this module come before all external
  // symbols defined elsewhere. { 1 | 2 | 3 }
  for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
         E = SymbolTable.end(); I != E; ++I) {
    if (!PartitionByLocal(*I)) {
      std::partition(I, E, PartitionByDefined);
      break;
    }
  }

  // Calculate the starting index for each of the local, extern defined, and 
  // undefined symbols, as well as the number of each to put in the LC_DYSYMTAB
  // load command.
  for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
         E = SymbolTable.end(); I != E; ++I) {
    if (PartitionByLocal(*I)) {
      ++DySymTab.nlocalsym;
      ++DySymTab.iextdefsym;
      ++DySymTab.iundefsym;
    } else if (PartitionByDefined(*I)) {
      ++DySymTab.nextdefsym;
      ++DySymTab.iundefsym;
    } else {
      ++DySymTab.nundefsym;
    }
  }
  
  // Write out a leading zero byte when emitting string table, for n_strx == 0
  // which means an empty string.
  OutputBuffer StrTOut(StrT, is64Bit, isLittleEndian);
  StrTOut.outbyte(0);

  // The order of the string table is:
  // 1. strings for external symbols
  // 2. strings for local symbols
  // Since this is the opposite order from the symbol table, which we have just
  // sorted, we can walk the symbol table backwards to output the string table.
  for (std::vector<MachOSym>::reverse_iterator I = SymbolTable.rbegin(),
        E = SymbolTable.rend(); I != E; ++I) {
    if (I->GVName == "") {
      I->n_strx = 0;
    } else {
      I->n_strx = StrT.size();
      StrTOut.outstring(I->GVName, I->GVName.length()+1);
    }
  }

  OutputBuffer SymTOut(SymT, is64Bit, isLittleEndian);

  unsigned index = 0;
  for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
         E = SymbolTable.end(); I != E; ++I, ++index) {
    // Add the section base address to the section offset in the n_value field
    // to calculate the full address.
    // FIXME: handle symbols where the n_value field is not the address
    GlobalValue *GV = const_cast<GlobalValue*>(I->GV);
    if (GV && GVSection[GV])
      I->n_value += GVSection[GV]->addr;
    if (GV && (GVOffset[GV] == -1))
      GVOffset[GV] = index;
         
    // Emit nlist to buffer
    SymTOut.outword(I->n_strx);
    SymTOut.outbyte(I->n_type);
    SymTOut.outbyte(I->n_sect);
    SymTOut.outhalf(I->n_desc);
    SymTOut.outaddr(I->n_value);
  }
}

/// CalculateRelocations - For each MachineRelocation in the current section,
/// calculate the index of the section containing the object to be relocated,
/// and the offset into that section.  From this information, create the
/// appropriate target-specific MachORelocation type and add buffer it to be
/// written out after we are finished writing out sections.
void MachOWriter::CalculateRelocations(MachOSection &MOS) {
  for (unsigned i = 0, e = MOS.Relocations.size(); i != e; ++i) {
    MachineRelocation &MR = MOS.Relocations[i];
    unsigned TargetSection = MR.getConstantVal();
    unsigned TargetAddr = 0;
    unsigned TargetIndex = 0;

    // This is a scattered relocation entry if it points to a global value with
    // a non-zero offset.
    bool Scattered = false;
    bool Extern = false;

    // Since we may not have seen the GlobalValue we were interested in yet at
    // the time we emitted the relocation for it, fix it up now so that it
    // points to the offset into the correct section.
    if (MR.isGlobalValue()) {
      GlobalValue *GV = MR.getGlobalValue();
      MachOSection *MOSPtr = GVSection[GV];
      intptr_t Offset = GVOffset[GV];
      
      // If we have never seen the global before, it must be to a symbol
      // defined in another module (N_UNDF).
      if (!MOSPtr) {
        // FIXME: need to append stub suffix
        Extern = true;
        TargetAddr = 0;
        TargetIndex = GVOffset[GV];
      } else {
        Scattered = TargetSection != 0;
        TargetSection = MOSPtr->Index;
      }
      MR.setResultPointer((void*)Offset);
    }
    
    // If the symbol is locally defined, pass in the address of the section and
    // the section index to the code which will generate the target relocation.
    if (!Extern) {
        MachOSection &To = *SectionList[TargetSection - 1];
        TargetAddr = To.addr;
        TargetIndex = To.Index;
    }

    OutputBuffer RelocOut(MOS.RelocBuffer, is64Bit, isLittleEndian);
    OutputBuffer SecOut(MOS.SectionData, is64Bit, isLittleEndian);
    
    MOS.nreloc += GetTargetRelocation(MR, MOS.Index, TargetAddr, TargetIndex,
                                      RelocOut, SecOut, Scattered, Extern);
  }
}

// InitMem - Write the value of a Constant to the specified memory location,
// converting it into bytes and relocations.
void MachOWriter::InitMem(const Constant *C, void *Addr, intptr_t Offset,
                          const TargetData *TD, 
                          std::vector<MachineRelocation> &MRs) {
  typedef std::pair<const Constant*, intptr_t> CPair;
  std::vector<CPair> WorkList;
  
  WorkList.push_back(CPair(C,(intptr_t)Addr + Offset));
  
  intptr_t ScatteredOffset = 0;
  
  while (!WorkList.empty()) {
    const Constant *PC = WorkList.back().first;
    intptr_t PA = WorkList.back().second;
    WorkList.pop_back();
    
    if (isa<UndefValue>(PC)) {
      continue;
    } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(PC)) {
      unsigned ElementSize = TD->getTypeSize(CP->getType()->getElementType());
      for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i)
        WorkList.push_back(CPair(CP->getOperand(i), PA+i*ElementSize));
    } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(PC)) {
      //
      // FIXME: Handle ConstantExpression.  See EE::getConstantValue()
      //
      switch (CE->getOpcode()) {
      case Instruction::GetElementPtr: {
        SmallVector<Value*, 8> Indices(CE->op_begin()+1, CE->op_end());
        ScatteredOffset = TD->getIndexedOffset(CE->getOperand(0)->getType(),
                                               &Indices[0], Indices.size());
        WorkList.push_back(CPair(CE->getOperand(0), PA));
        break;
      }
      case Instruction::Add:
      default:
        cerr << "ConstantExpr not handled as global var init: " << *CE << "\n";
        abort();
        break;
      }
    } else if (PC->getType()->isFirstClassType()) {
      unsigned char *ptr = (unsigned char *)PA;
      switch (PC->getType()->getTypeID()) {
      case Type::IntegerTyID: {
        unsigned NumBits = cast<IntegerType>(PC->getType())->getBitWidth();
        uint64_t val = cast<ConstantInt>(PC)->getZExtValue();
        if (NumBits <= 8)
          ptr[0] = val;
        else if (NumBits <= 16) {
          if (TD->isBigEndian())
            val = ByteSwap_16(val);
          ptr[0] = val;
          ptr[1] = val >> 8;
        } else if (NumBits <= 32) {
          if (TD->isBigEndian())
            val = ByteSwap_32(val);
          ptr[0] = val;
          ptr[1] = val >> 8;
          ptr[2] = val >> 16;
          ptr[3] = val >> 24;
        } else if (NumBits <= 64) {
          if (TD->isBigEndian())
            val = ByteSwap_64(val);
          ptr[0] = val;
          ptr[1] = val >> 8;
          ptr[2] = val >> 16;
          ptr[3] = val >> 24;
          ptr[4] = val >> 32;
          ptr[5] = val >> 40;
          ptr[6] = val >> 48;
          ptr[7] = val >> 56;
        } else {
          assert(0 && "Not implemented: bit widths > 64");
        }
        break;
      }
      case Type::FloatTyID: {
        uint32_t val = (uint32_t)*cast<ConstantFP>(PC)->
                                  getValueAPF().convertToAPInt().getRawData();
        if (TD->isBigEndian())
          val = ByteSwap_32(val);
        ptr[0] = val;
        ptr[1] = val >> 8;
        ptr[2] = val >> 16;
        ptr[3] = val >> 24;
        break;
      }
      case Type::DoubleTyID: {
        uint64_t val = *cast<ConstantFP>(PC)->getValueAPF().convertToAPInt().
                         getRawData();
        if (TD->isBigEndian())
          val = ByteSwap_64(val);
        ptr[0] = val;
        ptr[1] = val >> 8;
        ptr[2] = val >> 16;
        ptr[3] = val >> 24;
        ptr[4] = val >> 32;
        ptr[5] = val >> 40;
        ptr[6] = val >> 48;
        ptr[7] = val >> 56;
        break;
      }
      case Type::PointerTyID:
        if (isa<ConstantPointerNull>(PC))
          memset(ptr, 0, TD->getPointerSize());
        else if (const GlobalValue* GV = dyn_cast<GlobalValue>(PC)) {
          // FIXME: what about function stubs?
          MRs.push_back(MachineRelocation::getGV(PA-(intptr_t)Addr, 
                                                 MachineRelocation::VANILLA,
                                                 const_cast<GlobalValue*>(GV),
                                                 ScatteredOffset));
          ScatteredOffset = 0;
        } else
          assert(0 && "Unknown constant pointer type!");
        break;
      default:
        cerr << "ERROR: Constant unimp for type: " << *PC->getType() << "\n";
        abort();
      }
    } else if (isa<ConstantAggregateZero>(PC)) {
      memset((void*)PA, 0, (size_t)TD->getTypeSize(PC->getType()));
    } else if (const ConstantArray *CPA = dyn_cast<ConstantArray>(PC)) {
      unsigned ElementSize = TD->getTypeSize(CPA->getType()->getElementType());
      for (unsigned i = 0, e = CPA->getNumOperands(); i != e; ++i)
        WorkList.push_back(CPair(CPA->getOperand(i), PA+i*ElementSize));
    } else if (const ConstantStruct *CPS = dyn_cast<ConstantStruct>(PC)) {
      const StructLayout *SL =
        TD->getStructLayout(cast<StructType>(CPS->getType()));
      for (unsigned i = 0, e = CPS->getNumOperands(); i != e; ++i)
        WorkList.push_back(CPair(CPS->getOperand(i),
                                 PA+SL->getElementOffset(i)));
    } else {
      cerr << "Bad Type: " << *PC->getType() << "\n";
      assert(0 && "Unknown constant type to initialize memory with!");
    }
  }
}

MachOSym::MachOSym(const GlobalValue *gv, std::string name, uint8_t sect,
                   TargetMachine &TM) :
  GV(gv), n_strx(0), n_type(sect == NO_SECT ? N_UNDF : N_SECT), n_sect(sect),
  n_desc(0), n_value(0) {

  const TargetAsmInfo *TAI = TM.getTargetAsmInfo();  
  
  switch (GV->getLinkage()) {
  default:
    assert(0 && "Unexpected linkage type!");
    break;
  case GlobalValue::WeakLinkage:
  case GlobalValue::LinkOnceLinkage:
    assert(!isa<Function>(gv) && "Unexpected linkage type for Function!");
  case GlobalValue::ExternalLinkage:
    GVName = TAI->getGlobalPrefix() + name;
    n_type |= GV->hasHiddenVisibility() ? N_PEXT : N_EXT;
    break;
  case GlobalValue::InternalLinkage:
    GVName = TAI->getGlobalPrefix() + name;
    break;
  }
}