aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/llvm14/lib/MC/MCMachOStreamer.cpp
blob: 88aeeb9807386be0f1680b1e982a7d88712aa487 (plain) (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
//===- MCMachOStreamer.cpp - MachO Streamer -------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDirectives.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCFragment.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCLinkerOptimizationHint.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCSymbolMachO.h"
#include "llvm/MC/MCValue.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <vector>

using namespace llvm;

namespace {

class MCMachOStreamer : public MCObjectStreamer {
private:
  /// LabelSections - true if each section change should emit a linker local
  /// label for use in relocations for assembler local references. Obviates the
  /// need for local relocations. False by default.
  bool LabelSections;

  bool DWARFMustBeAtTheEnd;
  bool CreatedADWARFSection;

  /// HasSectionLabel - map of which sections have already had a non-local
  /// label emitted to them. Used so we don't emit extraneous linker local
  /// labels in the middle of the section.
  DenseMap<const MCSection*, bool> HasSectionLabel;

  void emitInstToData(const MCInst &Inst, const MCSubtargetInfo &STI) override;

  void emitDataRegion(DataRegionData::KindTy Kind);
  void emitDataRegionEnd();

public:
  MCMachOStreamer(MCContext &Context, std::unique_ptr<MCAsmBackend> MAB,
                  std::unique_ptr<MCObjectWriter> OW,
                  std::unique_ptr<MCCodeEmitter> Emitter,
                  bool DWARFMustBeAtTheEnd, bool label)
      : MCObjectStreamer(Context, std::move(MAB), std::move(OW),
                         std::move(Emitter)),
        LabelSections(label), DWARFMustBeAtTheEnd(DWARFMustBeAtTheEnd),
        CreatedADWARFSection(false) {}

  /// state management
  void reset() override {
    CreatedADWARFSection = false;
    HasSectionLabel.clear();
    MCObjectStreamer::reset();
  }

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

  void changeSection(MCSection *Sect, const MCExpr *Subsect) override;
  void emitLabel(MCSymbol *Symbol, SMLoc Loc = SMLoc()) override;
  void emitAssignment(MCSymbol *Symbol, const MCExpr *Value) override;
  void emitEHSymAttributes(const MCSymbol *Symbol, MCSymbol *EHSymbol) override;
  void emitAssemblerFlag(MCAssemblerFlag Flag) override;
  void emitLinkerOptions(ArrayRef<std::string> Options) override;
  void emitDataRegion(MCDataRegionType Kind) override;
  void emitVersionMin(MCVersionMinType Kind, unsigned Major, unsigned Minor,
                      unsigned Update, VersionTuple SDKVersion) override;
  void emitBuildVersion(unsigned Platform, unsigned Major, unsigned Minor,
                        unsigned Update, VersionTuple SDKVersion) override;
  void emitDarwinTargetVariantBuildVersion(unsigned Platform, unsigned Major,
                                           unsigned Minor, unsigned Update,
                                           VersionTuple SDKVersion) override;
  void emitThumbFunc(MCSymbol *Func) override;
  bool emitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) override;
  void emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) override;
  void emitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                        unsigned ByteAlignment) override;

  void emitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                             unsigned ByteAlignment) override;
  void emitZerofill(MCSection *Section, MCSymbol *Symbol = nullptr,
                    uint64_t Size = 0, unsigned ByteAlignment = 0,
                    SMLoc Loc = SMLoc()) override;
  void emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol, uint64_t Size,
                      unsigned ByteAlignment = 0) override;

  void emitIdent(StringRef IdentString) override {
    llvm_unreachable("macho doesn't support this directive");
  }

  void emitLOHDirective(MCLOHType Kind, const MCLOHArgs &Args) override {
    getAssembler().getLOHContainer().addDirective(Kind, Args);
  }
  void emitCGProfileEntry(const MCSymbolRefExpr *From,
                          const MCSymbolRefExpr *To, uint64_t Count) override {
    if (!From->getSymbol().isTemporary() && !To->getSymbol().isTemporary())
      getAssembler().CGProfile.push_back({From, To, Count});
  }

  void finishImpl() override;

  void finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE);
  void finalizeCGProfile();
};

} // end anonymous namespace.

static bool canGoAfterDWARF(const MCSectionMachO &MSec) {
  // These sections are created by the assembler itself after the end of
  // the .s file.
  StringRef SegName = MSec.getSegmentName();
  StringRef SecName = MSec.getName();

  if (SegName == "__LD" && SecName == "__compact_unwind")
    return true;

  if (SegName == "__IMPORT") {
    if (SecName == "__jump_table")
      return true;

    if (SecName == "__pointers")
      return true;
  }

  if (SegName == "__TEXT" && SecName == "__eh_frame")
    return true;

  if (SegName == "__DATA" && (SecName == "__nl_symbol_ptr" ||
                              SecName == "__thread_ptr"))
    return true;
  if (SegName == "__LLVM" && SecName == "__cg_profile")
    return true;
  return false;
}

void MCMachOStreamer::changeSection(MCSection *Section,
                                    const MCExpr *Subsection) {
  // Change the section normally.
  bool Created = changeSectionImpl(Section, Subsection);
  const MCSectionMachO &MSec = *cast<MCSectionMachO>(Section);
  StringRef SegName = MSec.getSegmentName();
  if (SegName == "__DWARF")
    CreatedADWARFSection = true;
  else if (Created && DWARFMustBeAtTheEnd && !canGoAfterDWARF(MSec))
    assert((!CreatedADWARFSection ||
            Section == getContext().getObjectFileInfo()->getStackMapSection())
           && "Creating regular section after DWARF");

  // Output a linker-local symbol so we don't need section-relative local
  // relocations. The linker hates us when we do that.
  if (LabelSections && !HasSectionLabel[Section] &&
      !Section->getBeginSymbol()) {
    MCSymbol *Label = getContext().createLinkerPrivateTempSymbol();
    Section->setBeginSymbol(Label);
    HasSectionLabel[Section] = true;
  }
}

void MCMachOStreamer::emitEHSymAttributes(const MCSymbol *Symbol,
                                          MCSymbol *EHSymbol) {
  getAssembler().registerSymbol(*Symbol);
  if (Symbol->isExternal())
    emitSymbolAttribute(EHSymbol, MCSA_Global);
  if (cast<MCSymbolMachO>(Symbol)->isWeakDefinition())
    emitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
  if (Symbol->isPrivateExtern())
    emitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
}

void MCMachOStreamer::emitLabel(MCSymbol *Symbol, SMLoc Loc) {
  // We have to create a new fragment if this is an atom defining symbol,
  // fragments cannot span atoms.
  if (getAssembler().isSymbolLinkerVisible(*Symbol))
    insert(new MCDataFragment());

  MCObjectStreamer::emitLabel(Symbol, Loc);

  // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
  // to clear the weak reference and weak definition bits too, but the
  // implementation was buggy. For now we just try to match 'as', for
  // diffability.
  //
  // FIXME: Cleanup this code, these bits should be emitted based on semantic
  // properties, not on the order of definition, etc.
  cast<MCSymbolMachO>(Symbol)->clearReferenceType();
}

void MCMachOStreamer::emitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
  MCValue Res;

  if (Value->evaluateAsRelocatable(Res, nullptr, nullptr)) {
    if (const MCSymbolRefExpr *SymAExpr = Res.getSymA()) {
      const MCSymbol &SymA = SymAExpr->getSymbol();
      if (!Res.getSymB() && (SymA.getName() == "" || Res.getConstant() != 0))
        cast<MCSymbolMachO>(Symbol)->setAltEntry();
    }
  }
  MCObjectStreamer::emitAssignment(Symbol, Value);
}

void MCMachOStreamer::emitDataRegion(DataRegionData::KindTy Kind) {
  // Create a temporary label to mark the start of the data region.
  MCSymbol *Start = getContext().createTempSymbol();
  emitLabel(Start);
  // Record the region for the object writer to use.
  DataRegionData Data = { Kind, Start, nullptr };
  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
  Regions.push_back(Data);
}

void MCMachOStreamer::emitDataRegionEnd() {
  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
  assert(!Regions.empty() && "Mismatched .end_data_region!");
  DataRegionData &Data = Regions.back();
  assert(!Data.End && "Mismatched .end_data_region!");
  // Create a temporary label to mark the end of the data region.
  Data.End = getContext().createTempSymbol();
  emitLabel(Data.End);
}

void MCMachOStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
  // Let the target do whatever target specific stuff it needs to do.
  getAssembler().getBackend().handleAssemblerFlag(Flag);
  // Do any generic stuff we need to do.
  switch (Flag) {
  case MCAF_SyntaxUnified: return; // no-op here.
  case MCAF_Code16: return; // Change parsing mode; no-op here.
  case MCAF_Code32: return; // Change parsing mode; no-op here.
  case MCAF_Code64: return; // Change parsing mode; no-op here.
  case MCAF_SubsectionsViaSymbols:
    getAssembler().setSubsectionsViaSymbols(true);
    return;
  }
}

void MCMachOStreamer::emitLinkerOptions(ArrayRef<std::string> Options) {
  getAssembler().getLinkerOptions().push_back(Options);
}

void MCMachOStreamer::emitDataRegion(MCDataRegionType Kind) {
  switch (Kind) {
  case MCDR_DataRegion:
    emitDataRegion(DataRegionData::Data);
    return;
  case MCDR_DataRegionJT8:
    emitDataRegion(DataRegionData::JumpTable8);
    return;
  case MCDR_DataRegionJT16:
    emitDataRegion(DataRegionData::JumpTable16);
    return;
  case MCDR_DataRegionJT32:
    emitDataRegion(DataRegionData::JumpTable32);
    return;
  case MCDR_DataRegionEnd:
    emitDataRegionEnd();
    return;
  }
}

void MCMachOStreamer::emitVersionMin(MCVersionMinType Kind, unsigned Major,
                                     unsigned Minor, unsigned Update,
                                     VersionTuple SDKVersion) {
  getAssembler().setVersionMin(Kind, Major, Minor, Update, SDKVersion);
}

void MCMachOStreamer::emitBuildVersion(unsigned Platform, unsigned Major,
                                       unsigned Minor, unsigned Update,
                                       VersionTuple SDKVersion) {
  getAssembler().setBuildVersion((MachO::PlatformType)Platform, Major, Minor,
                                 Update, SDKVersion);
}

void MCMachOStreamer::emitDarwinTargetVariantBuildVersion(
    unsigned Platform, unsigned Major, unsigned Minor, unsigned Update,
    VersionTuple SDKVersion) {
  getAssembler().setDarwinTargetVariantBuildVersion(
      (MachO::PlatformType)Platform, Major, Minor, Update, SDKVersion);
}

void MCMachOStreamer::emitThumbFunc(MCSymbol *Symbol) {
  // Remember that the function is a thumb function. Fixup and relocation
  // values will need adjusted.
  getAssembler().setIsThumbFunc(Symbol);
  cast<MCSymbolMachO>(Symbol)->setThumbFunc();
}

bool MCMachOStreamer::emitSymbolAttribute(MCSymbol *Sym,
                                          MCSymbolAttr Attribute) {
  MCSymbolMachO *Symbol = cast<MCSymbolMachO>(Sym);

  // Indirect symbols are handled differently, to match how 'as' handles
  // them. This makes writing matching .o files easier.
  if (Attribute == MCSA_IndirectSymbol) {
    // Note that we intentionally cannot use the symbol data here; this is
    // important for matching the string table that 'as' generates.
    IndirectSymbolData ISD;
    ISD.Symbol = Symbol;
    ISD.Section = getCurrentSectionOnly();
    getAssembler().getIndirectSymbols().push_back(ISD);
    return true;
  }

  // Adding a symbol attribute always introduces the symbol, note that an
  // important side effect of calling registerSymbol here is to register
  // the symbol with the assembler.
  getAssembler().registerSymbol(*Symbol);

  // The implementation of symbol attributes is designed to match 'as', but it
  // leaves much to desired. It doesn't really make sense to arbitrarily add and
  // remove flags, but 'as' allows this (in particular, see .desc).
  //
  // In the future it might be worth trying to make these operations more well
  // defined.
  switch (Attribute) {
  case MCSA_Invalid:
  case MCSA_ELF_TypeFunction:
  case MCSA_ELF_TypeIndFunction:
  case MCSA_ELF_TypeObject:
  case MCSA_ELF_TypeTLS:
  case MCSA_ELF_TypeCommon:
  case MCSA_ELF_TypeNoType:
  case MCSA_ELF_TypeGnuUniqueObject:
  case MCSA_Extern:
  case MCSA_Hidden:
  case MCSA_IndirectSymbol:
  case MCSA_Internal:
  case MCSA_Protected:
  case MCSA_Weak:
  case MCSA_Local:
  case MCSA_LGlobal:
    return false;

  case MCSA_Global:
    Symbol->setExternal(true);
    // This effectively clears the undefined lazy bit, in Darwin 'as', although
    // it isn't very consistent because it implements this as part of symbol
    // lookup.
    //
    // FIXME: Cleanup this code, these bits should be emitted based on semantic
    // properties, not on the order of definition, etc.
    Symbol->setReferenceTypeUndefinedLazy(false);
    break;

  case MCSA_LazyReference:
    // FIXME: This requires -dynamic.
    Symbol->setNoDeadStrip();
    if (Symbol->isUndefined())
      Symbol->setReferenceTypeUndefinedLazy(true);
    break;

    // Since .reference sets the no dead strip bit, it is equivalent to
    // .no_dead_strip in practice.
  case MCSA_Reference:
  case MCSA_NoDeadStrip:
    Symbol->setNoDeadStrip();
    break;

  case MCSA_SymbolResolver:
    Symbol->setSymbolResolver();
    break;

  case MCSA_AltEntry:
    Symbol->setAltEntry();
    break;

  case MCSA_PrivateExtern:
    Symbol->setExternal(true);
    Symbol->setPrivateExtern(true);
    break;

  case MCSA_WeakReference:
    // FIXME: This requires -dynamic.
    if (Symbol->isUndefined())
      Symbol->setWeakReference();
    break;

  case MCSA_WeakDefinition:
    // FIXME: 'as' enforces that this is defined and global. The manual claims
    // it has to be in a coalesced section, but this isn't enforced.
    Symbol->setWeakDefinition();
    break;

  case MCSA_WeakDefAutoPrivate:
    Symbol->setWeakDefinition();
    Symbol->setWeakReference();
    break;

  case MCSA_Cold:
    Symbol->setCold();
    break;
  }

  return true;
}

void MCMachOStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
  // Encode the 'desc' value into the lowest implementation defined bits.
  getAssembler().registerSymbol(*Symbol);
  cast<MCSymbolMachO>(Symbol)->setDesc(DescValue);
}

void MCMachOStreamer::emitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                       unsigned ByteAlignment) {
  // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");

  getAssembler().registerSymbol(*Symbol);
  Symbol->setExternal(true);
  Symbol->setCommon(Size, ByteAlignment);
}

void MCMachOStreamer::emitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                            unsigned ByteAlignment) {
  // '.lcomm' is equivalent to '.zerofill'.
  return emitZerofill(getContext().getObjectFileInfo()->getDataBSSSection(),
                      Symbol, Size, ByteAlignment);
}

void MCMachOStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
                                   uint64_t Size, unsigned ByteAlignment,
                                   SMLoc Loc) {
  // On darwin all virtual sections have zerofill type. Disallow the usage of
  // .zerofill in non-virtual functions. If something similar is needed, use
  // .space or .zero.
  if (!Section->isVirtualSection()) {
    getContext().reportError(
        Loc, "The usage of .zerofill is restricted to sections of "
             "ZEROFILL type. Use .zero or .space instead.");
    return; // Early returning here shouldn't harm. EmitZeros should work on any
            // section.
  }

  PushSection();
  SwitchSection(Section);

  // The symbol may not be present, which only creates the section.
  if (Symbol) {
    emitValueToAlignment(ByteAlignment, 0, 1, 0);
    emitLabel(Symbol);
    emitZeros(Size);
  }
  PopSection();
}

// This should always be called with the thread local bss section.  Like the
// .zerofill directive this doesn't actually switch sections on us.
void MCMachOStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
                                     uint64_t Size, unsigned ByteAlignment) {
  emitZerofill(Section, Symbol, Size, ByteAlignment);
}

void MCMachOStreamer::emitInstToData(const MCInst &Inst,
                                     const MCSubtargetInfo &STI) {
  MCDataFragment *DF = getOrCreateDataFragment();

  SmallVector<MCFixup, 4> Fixups;
  SmallString<256> Code;
  raw_svector_ostream VecOS(Code);
  getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);

  // Add the fixups and data.
  for (MCFixup &Fixup : Fixups) {
    Fixup.setOffset(Fixup.getOffset() + DF->getContents().size());
    DF->getFixups().push_back(Fixup);
  }
  DF->setHasInstructions(STI);
  DF->getContents().append(Code.begin(), Code.end());
}

void MCMachOStreamer::finishImpl() {
  emitFrames(&getAssembler().getBackend());

  // We have to set the fragment atom associations so we can relax properly for
  // Mach-O.

  // First, scan the symbol table to build a lookup table from fragments to
  // defining symbols.
  DenseMap<const MCFragment *, const MCSymbol *> DefiningSymbolMap;
  for (const MCSymbol &Symbol : getAssembler().symbols()) {
    if (getAssembler().isSymbolLinkerVisible(Symbol) && Symbol.isInSection() &&
        !Symbol.isVariable()) {
      // An atom defining symbol should never be internal to a fragment.
      assert(Symbol.getOffset() == 0 &&
             "Invalid offset in atom defining symbol!");
      DefiningSymbolMap[Symbol.getFragment()] = &Symbol;
    }
  }

  // Set the fragment atom associations by tracking the last seen atom defining
  // symbol.
  for (MCSection &Sec : getAssembler()) {
    const MCSymbol *CurrentAtom = nullptr;
    for (MCFragment &Frag : Sec) {
      if (const MCSymbol *Symbol = DefiningSymbolMap.lookup(&Frag))
        CurrentAtom = Symbol;
      Frag.setAtom(CurrentAtom);
    }
  }

  finalizeCGProfile();

  this->MCObjectStreamer::finishImpl();
}

void MCMachOStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
  const MCSymbol *S = &SRE->getSymbol();
  bool Created;
  getAssembler().registerSymbol(*S, &Created);
  if (Created)
    S->setExternal(true);
}

void MCMachOStreamer::finalizeCGProfile() {
  MCAssembler &Asm = getAssembler();
  if (Asm.CGProfile.empty())
    return;
  for (MCAssembler::CGProfileEntry &E : Asm.CGProfile) {
    finalizeCGProfileEntry(E.From);
    finalizeCGProfileEntry(E.To);
  }
  // We can't write the section out until symbol indices are finalized which
  // doesn't happen until after section layout. We need to create the section
  // and set its size now so that it's accounted for in layout.
  MCSection *CGProfileSection = Asm.getContext().getMachOSection(
      "__LLVM", "__cg_profile", 0, SectionKind::getMetadata());
  Asm.registerSection(*CGProfileSection);
  auto *Frag = new MCDataFragment(CGProfileSection);
  // For each entry, reserve space for 2 32-bit indices and a 64-bit count.
  size_t SectionBytes =
      Asm.CGProfile.size() * (2 * sizeof(uint32_t) + sizeof(uint64_t));
  Frag->getContents().resize(SectionBytes);
}

MCStreamer *llvm::createMachOStreamer(MCContext &Context,
                                      std::unique_ptr<MCAsmBackend> &&MAB,
                                      std::unique_ptr<MCObjectWriter> &&OW,
                                      std::unique_ptr<MCCodeEmitter> &&CE,
                                      bool RelaxAll, bool DWARFMustBeAtTheEnd,
                                      bool LabelSections) {
  MCMachOStreamer *S =
      new MCMachOStreamer(Context, std::move(MAB), std::move(OW), std::move(CE),
                          DWARFMustBeAtTheEnd, LabelSections);
  const Triple &Target = Context.getTargetTriple();
  S->emitVersionForTarget(
      Target, Context.getObjectFileInfo()->getSDKVersion(),
      Context.getObjectFileInfo()->getDarwinTargetVariantTriple(),
      Context.getObjectFileInfo()->getDarwinTargetVariantSDKVersion());
  if (RelaxAll)
    S->getAssembler().setRelaxAll(true);
  return S;
}