llvm.org GIT mirror llvm / 3a50eea lib / MC / MCObjectStreamer.cpp
3a50eea

Tree @3a50eea (Download .tar.gz)

MCObjectStreamer.cpp @3a50eearaw · 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
//===- lib/MC/MCObjectStreamer.cpp - Object File MCStreamer Interface -----===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCCodeView.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/TargetRegistry.h"
using namespace llvm;

MCObjectStreamer::MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB,
                                   raw_pwrite_stream &OS,
                                   MCCodeEmitter *Emitter_)
    : MCStreamer(Context),
      Assembler(new MCAssembler(Context, TAB, *Emitter_,
                                *TAB.createObjectWriter(OS))),
      EmitEHFrame(true), EmitDebugFrame(false) {}

MCObjectStreamer::~MCObjectStreamer() {
  delete &Assembler->getBackend();
  delete &Assembler->getEmitter();
  delete &Assembler->getWriter();
  delete Assembler;
}

void MCObjectStreamer::flushPendingLabels(MCFragment *F, uint64_t FOffset) {
  if (PendingLabels.empty())
    return;
  if (!F) {
    F = new MCDataFragment();
    MCSection *CurSection = getCurrentSectionOnly();
    CurSection->getFragmentList().insert(CurInsertionPoint, F);
    F->setParent(CurSection);
  }
  for (MCSymbol *Sym : PendingLabels) {
    Sym->setFragment(F);
    Sym->setOffset(FOffset);
  }
  PendingLabels.clear();
}

void MCObjectStreamer::emitAbsoluteSymbolDiff(const MCSymbol *Hi,
                                              const MCSymbol *Lo,
                                              unsigned Size) {
  // If not assigned to the same (valid) fragment, fallback.
  if (!Hi->getFragment() || Hi->getFragment() != Lo->getFragment() ||
      Hi->isVariable() || Lo->isVariable()) {
    MCStreamer::emitAbsoluteSymbolDiff(Hi, Lo, Size);
    return;
  }

  EmitIntValue(Hi->getOffset() - Lo->getOffset(), Size);
}

void MCObjectStreamer::reset() {
  if (Assembler)
    Assembler->reset();
  CurInsertionPoint = MCSection::iterator();
  EmitEHFrame = true;
  EmitDebugFrame = false;
  PendingLabels.clear();
  MCStreamer::reset();
}

void MCObjectStreamer::EmitFrames(MCAsmBackend *MAB) {
  if (!getNumFrameInfos())
    return;

  if (EmitEHFrame)
    MCDwarfFrameEmitter::Emit(*this, MAB, true);

  if (EmitDebugFrame)
    MCDwarfFrameEmitter::Emit(*this, MAB, false);
}

MCFragment *MCObjectStreamer::getCurrentFragment() const {
  assert(getCurrentSectionOnly() && "No current section!");

  if (CurInsertionPoint != getCurrentSectionOnly()->getFragmentList().begin())
    return &*std::prev(CurInsertionPoint);

  return nullptr;
}

MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() {
  MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
  // When bundling is enabled, we don't want to add data to a fragment that
  // already has instructions (see MCELFStreamer::EmitInstToData for details)
  if (!F || (Assembler->isBundlingEnabled() && !Assembler->getRelaxAll() &&
             F->hasInstructions())) {
    F = new MCDataFragment();
    insert(F);
  }
  return F;
}

void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) {
  Assembler->registerSymbol(Sym);
}

void MCObjectStreamer::EmitCFISections(bool EH, bool Debug) {
  MCStreamer::EmitCFISections(EH, Debug);
  EmitEHFrame = EH;
  EmitDebugFrame = Debug;
}

void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
                                     SMLoc Loc) {
  MCStreamer::EmitValueImpl(Value, Size, Loc);
  MCDataFragment *DF = getOrCreateDataFragment();
  flushPendingLabels(DF, DF->getContents().size());

  MCCVLineEntry::Make(this);
  MCDwarfLineEntry::Make(this, getCurrentSectionOnly());

  // Avoid fixups when possible.
  int64_t AbsValue;
  if (Value->evaluateAsAbsolute(AbsValue, getAssembler())) {
    EmitIntValue(AbsValue, Size);
    return;
  }
  DF->getFixups().push_back(
      MCFixup::create(DF->getContents().size(), Value,
                      MCFixup::getKindForSize(Size, false), Loc));
  DF->getContents().resize(DF->getContents().size() + Size, 0);
}

void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) {
  // We need to create a local symbol to avoid relocations.
  Frame.Begin = getContext().createTempSymbol();
  EmitLabel(Frame.Begin);
}

void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) {
  Frame.End = getContext().createTempSymbol();
  EmitLabel(Frame.End);
}

void MCObjectStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc) {
  MCStreamer::EmitLabel(Symbol, Loc);

  getAssembler().registerSymbol(*Symbol);

  // If there is a current fragment, mark the symbol as pointing into it.
  // Otherwise queue the label and set its fragment pointer when we emit the
  // next fragment.
  auto *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
  if (F && !(getAssembler().isBundlingEnabled() &&
             getAssembler().getRelaxAll())) {
    Symbol->setFragment(F);
    Symbol->setOffset(F->getContents().size());
  } else {
    PendingLabels.push_back(Symbol);
  }
}

void MCObjectStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc, MCFragment *F) {
  MCStreamer::EmitLabel(Symbol, Loc);
  getAssembler().registerSymbol(*Symbol);
  auto *DF = dyn_cast_or_null<MCDataFragment>(F);
  if (DF)
    Symbol->setFragment(F);
  else
    PendingLabels.push_back(Symbol);
}

void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) {
  int64_t IntValue;
  if (Value->evaluateAsAbsolute(IntValue, getAssembler())) {
    EmitULEB128IntValue(IntValue);
    return;
  }
  insert(new MCLEBFragment(*Value, false));
}

void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value) {
  int64_t IntValue;
  if (Value->evaluateAsAbsolute(IntValue, getAssembler())) {
    EmitSLEB128IntValue(IntValue);
    return;
  }
  insert(new MCLEBFragment(*Value, true));
}

void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias,
                                         const MCSymbol *Symbol) {
  report_fatal_error("This file format doesn't support weak aliases.");
}

void MCObjectStreamer::ChangeSection(MCSection *Section,
                                     const MCExpr *Subsection) {
  changeSectionImpl(Section, Subsection);
}

bool MCObjectStreamer::changeSectionImpl(MCSection *Section,
                                         const MCExpr *Subsection) {
  assert(Section && "Cannot switch to a null section!");
  flushPendingLabels(nullptr);
  getContext().clearDwarfLocSeen();

  bool Created = getAssembler().registerSection(*Section);

  int64_t IntSubsection = 0;
  if (Subsection &&
      !Subsection->evaluateAsAbsolute(IntSubsection, getAssembler()))
    report_fatal_error("Cannot evaluate subsection number");
  if (IntSubsection < 0 || IntSubsection > 8192)
    report_fatal_error("Subsection number out of range");
  CurInsertionPoint =
      Section->getSubsectionInsertionPoint(unsigned(IntSubsection));
  return Created;
}

void MCObjectStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
  getAssembler().registerSymbol(*Symbol);
  MCStreamer::EmitAssignment(Symbol, Value);
}

bool MCObjectStreamer::mayHaveInstructions(MCSection &Sec) const {
  return Sec.hasInstructions();
}

void MCObjectStreamer::EmitInstruction(const MCInst &Inst,
                                       const MCSubtargetInfo &STI) {
  MCStreamer::EmitInstruction(Inst, STI);

  MCSection *Sec = getCurrentSectionOnly();
  Sec->setHasInstructions(true);

  // Now that a machine instruction has been assembled into this section, make
  // a line entry for any .loc directive that has been seen.
  MCCVLineEntry::Make(this);
  MCDwarfLineEntry::Make(this, getCurrentSectionOnly());

  // If this instruction doesn't need relaxation, just emit it as data.
  MCAssembler &Assembler = getAssembler();
  if (!Assembler.getBackend().mayNeedRelaxation(Inst)) {
    EmitInstToData(Inst, STI);
    return;
  }

  // Otherwise, relax and emit it as data if either:
  // - The RelaxAll flag was passed
  // - Bundling is enabled and this instruction is inside a bundle-locked
  //   group. We want to emit all such instructions into the same data
  //   fragment.
  if (Assembler.getRelaxAll() ||
      (Assembler.isBundlingEnabled() && Sec->isBundleLocked())) {
    MCInst Relaxed;
    getAssembler().getBackend().relaxInstruction(Inst, STI, Relaxed);
    while (getAssembler().getBackend().mayNeedRelaxation(Relaxed))
      getAssembler().getBackend().relaxInstruction(Relaxed, STI, Relaxed);
    EmitInstToData(Relaxed, STI);
    return;
  }

  // Otherwise emit to a separate fragment.
  EmitInstToFragment(Inst, STI);
}

void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst,
                                          const MCSubtargetInfo &STI) {
  if (getAssembler().getRelaxAll() && getAssembler().isBundlingEnabled())
    llvm_unreachable("All instructions should have already been relaxed");

  // Always create a new, separate fragment here, because its size can change
  // during relaxation.
  MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI);
  insert(IF);

  SmallString<128> Code;
  raw_svector_ostream VecOS(Code);
  getAssembler().getEmitter().encodeInstruction(Inst, VecOS, IF->getFixups(),
                                                STI);
  IF->getContents().append(Code.begin(), Code.end());
}

#ifndef NDEBUG
static const char *const BundlingNotImplementedMsg =
  "Aligned bundling is not implemented for this object format";
#endif

void MCObjectStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
  llvm_unreachable(BundlingNotImplementedMsg);
}

void MCObjectStreamer::EmitBundleLock(bool AlignToEnd) {
  llvm_unreachable(BundlingNotImplementedMsg);
}

void MCObjectStreamer::EmitBundleUnlock() {
  llvm_unreachable(BundlingNotImplementedMsg);
}

void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
                                             unsigned Column, unsigned Flags,
                                             unsigned Isa,
                                             unsigned Discriminator,
                                             StringRef FileName) {
  // In case we see two .loc directives in a row, make sure the
  // first one gets a line entry.
  MCDwarfLineEntry::Make(this, getCurrentSectionOnly());

  this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
                                          Isa, Discriminator, FileName);
}

static const MCExpr *buildSymbolDiff(MCObjectStreamer &OS, const MCSymbol *A,
                                     const MCSymbol *B) {
  MCContext &Context = OS.getContext();
  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
  const MCExpr *ARef = MCSymbolRefExpr::create(A, Variant, Context);
  const MCExpr *BRef = MCSymbolRefExpr::create(B, Variant, Context);
  const MCExpr *AddrDelta =
      MCBinaryExpr::create(MCBinaryExpr::Sub, ARef, BRef, Context);
  return AddrDelta;
}

static void emitDwarfSetLineAddr(MCObjectStreamer &OS,
                                 MCDwarfLineTableParams Params,
                                 int64_t LineDelta, const MCSymbol *Label,
                                 int PointerSize) {
  // emit the sequence to set the address
  OS.EmitIntValue(dwarf::DW_LNS_extended_op, 1);
  OS.EmitULEB128IntValue(PointerSize + 1);
  OS.EmitIntValue(dwarf::DW_LNE_set_address, 1);
  OS.EmitSymbolValue(Label, PointerSize);

  // emit the sequence for the LineDelta (from 1) and a zero address delta.
  MCDwarfLineAddr::Emit(&OS, Params, LineDelta, 0);
}

void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
                                                const MCSymbol *LastLabel,
                                                const MCSymbol *Label,
                                                unsigned PointerSize) {
  if (!LastLabel) {
    emitDwarfSetLineAddr(*this, Assembler->getDWARFLinetableParams(), LineDelta,
                         Label, PointerSize);
    return;
  }
  const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
  int64_t Res;
  if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) {
    MCDwarfLineAddr::Emit(this, Assembler->getDWARFLinetableParams(), LineDelta,
                          Res);
    return;
  }
  insert(new MCDwarfLineAddrFragment(LineDelta, *AddrDelta));
}

void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
                                                 const MCSymbol *Label) {
  const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
  int64_t Res;
  if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) {
    MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res);
    return;
  }
  insert(new MCDwarfCallFrameFragment(*AddrDelta));
}

void MCObjectStreamer::EmitCVLocDirective(unsigned FunctionId, unsigned FileNo,
                                          unsigned Line, unsigned Column,
                                          bool PrologueEnd, bool IsStmt,
                                          StringRef FileName, SMLoc Loc) {
  // In case we see two .cv_loc directives in a row, make sure the
  // first one gets a line entry.
  MCCVLineEntry::Make(this);

  this->MCStreamer::EmitCVLocDirective(FunctionId, FileNo, Line, Column,
                                       PrologueEnd, IsStmt, FileName, Loc);
}

void MCObjectStreamer::EmitCVLinetableDirective(unsigned FunctionId,
                                                const MCSymbol *Begin,
                                                const MCSymbol *End) {
  getContext().getCVContext().emitLineTableForFunction(*this, FunctionId, Begin,
                                                       End);
  this->MCStreamer::EmitCVLinetableDirective(FunctionId, Begin, End);
}

void MCObjectStreamer::EmitCVInlineLinetableDirective(
    unsigned PrimaryFunctionId, unsigned SourceFileId, unsigned SourceLineNum,
    const MCSymbol *FnStartSym, const MCSymbol *FnEndSym) {
  getContext().getCVContext().emitInlineLineTableForFunction(
      *this, PrimaryFunctionId, SourceFileId, SourceLineNum, FnStartSym,
      FnEndSym);
  this->MCStreamer::EmitCVInlineLinetableDirective(
      PrimaryFunctionId, SourceFileId, SourceLineNum, FnStartSym, FnEndSym);
}

void MCObjectStreamer::EmitCVDefRangeDirective(
    ArrayRef<std::pair<const MCSymbol *, const MCSymbol *>> Ranges,
    StringRef FixedSizePortion) {
  getContext().getCVContext().emitDefRange(*this, Ranges, FixedSizePortion);
  this->MCStreamer::EmitCVDefRangeDirective(Ranges, FixedSizePortion);
}

void MCObjectStreamer::EmitCVStringTableDirective() {
  getContext().getCVContext().emitStringTable(*this);
}
void MCObjectStreamer::EmitCVFileChecksumsDirective() {
  getContext().getCVContext().emitFileChecksums(*this);
}


void MCObjectStreamer::EmitBytes(StringRef Data) {
  MCCVLineEntry::Make(this);
  MCDwarfLineEntry::Make(this, getCurrentSectionOnly());
  MCDataFragment *DF = getOrCreateDataFragment();
  flushPendingLabels(DF, DF->getContents().size());
  DF->getContents().append(Data.begin(), Data.end());
}

void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,
                                            int64_t Value,
                                            unsigned ValueSize,
                                            unsigned MaxBytesToEmit) {
  if (MaxBytesToEmit == 0)
    MaxBytesToEmit = ByteAlignment;
  insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit));

  // Update the maximum alignment on the current section if necessary.
  MCSection *CurSec = getCurrentSectionOnly();
  if (ByteAlignment > CurSec->getAlignment())
    CurSec->setAlignment(ByteAlignment);
}

void MCObjectStreamer::EmitCodeAlignment(unsigned ByteAlignment,
                                         unsigned MaxBytesToEmit) {
  EmitValueToAlignment(ByteAlignment, 0, 1, MaxBytesToEmit);
  cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true);
}

void MCObjectStreamer::emitValueToOffset(const MCExpr *Offset,
                                         unsigned char Value,
                                         SMLoc Loc) {
  insert(new MCOrgFragment(*Offset, Value, Loc));
}

// Associate DTPRel32 fixup with data and resize data area
void MCObjectStreamer::EmitDTPRel32Value(const MCExpr *Value) {
  MCDataFragment *DF = getOrCreateDataFragment();
  flushPendingLabels(DF, DF->getContents().size());

  DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
                                            Value, FK_DTPRel_4));
  DF->getContents().resize(DF->getContents().size() + 4, 0);
}

// Associate DTPRel64 fixup with data and resize data area
void MCObjectStreamer::EmitDTPRel64Value(const MCExpr *Value) {
  MCDataFragment *DF = getOrCreateDataFragment();
  flushPendingLabels(DF, DF->getContents().size());

  DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
                                            Value, FK_DTPRel_8));
  DF->getContents().resize(DF->getContents().size() + 8, 0);
}

// Associate TPRel32 fixup with data and resize data area
void MCObjectStreamer::EmitTPRel32Value(const MCExpr *Value) {
  MCDataFragment *DF = getOrCreateDataFragment();
  flushPendingLabels(DF, DF->getContents().size());

  DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
                                            Value, FK_TPRel_4));
  DF->getContents().resize(DF->getContents().size() + 4, 0);
}

// Associate TPRel64 fixup with data and resize data area
void MCObjectStreamer::EmitTPRel64Value(const MCExpr *Value) {
  MCDataFragment *DF = getOrCreateDataFragment();
  flushPendingLabels(DF, DF->getContents().size());

  DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
                                            Value, FK_TPRel_8));
  DF->getContents().resize(DF->getContents().size() + 8, 0);
}

// Associate GPRel32 fixup with data and resize data area
void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) {
  MCDataFragment *DF = getOrCreateDataFragment();
  flushPendingLabels(DF, DF->getContents().size());

  DF->getFixups().push_back(
      MCFixup::create(DF->getContents().size(), Value, FK_GPRel_4));
  DF->getContents().resize(DF->getContents().size() + 4, 0);
}

// Associate GPRel64 fixup with data and resize data area
void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) {
  MCDataFragment *DF = getOrCreateDataFragment();
  flushPendingLabels(DF, DF->getContents().size());

  DF->getFixups().push_back(
      MCFixup::create(DF->getContents().size(), Value, FK_GPRel_4));
  DF->getContents().resize(DF->getContents().size() + 8, 0);
}

bool MCObjectStreamer::EmitRelocDirective(const MCExpr &Offset, StringRef Name,
                                          const MCExpr *Expr, SMLoc Loc) {
  int64_t OffsetValue;
  if (!Offset.evaluateAsAbsolute(OffsetValue))
    llvm_unreachable("Offset is not absolute");

  if (OffsetValue < 0)
    llvm_unreachable("Offset is negative");

  MCDataFragment *DF = getOrCreateDataFragment();
  flushPendingLabels(DF, DF->getContents().size());

  Optional<MCFixupKind> MaybeKind = Assembler->getBackend().getFixupKind(Name);
  if (!MaybeKind.hasValue())
    return true;

  MCFixupKind Kind = *MaybeKind;

  if (Expr == nullptr)
    Expr =
        MCSymbolRefExpr::create(getContext().createTempSymbol(), getContext());
  DF->getFixups().push_back(MCFixup::create(OffsetValue, Expr, Kind, Loc));
  return false;
}

void MCObjectStreamer::emitFill(uint64_t NumBytes, uint8_t FillValue) {
  assert(getCurrentSectionOnly() && "need a section");
  insert(new MCFillFragment(FillValue, NumBytes));
}

void MCObjectStreamer::emitFill(const MCExpr &NumBytes, uint64_t FillValue,
                                SMLoc Loc) {
  MCDataFragment *DF = getOrCreateDataFragment();
  flushPendingLabels(DF, DF->getContents().size());

  int64_t IntNumBytes;
  if (!NumBytes.evaluateAsAbsolute(IntNumBytes, getAssembler())) {
    getContext().reportError(Loc, "expected absolute expression");
    return;
  }

  if (IntNumBytes <= 0) {
    getContext().reportError(Loc, "invalid number of bytes");
    return;
  }

  emitFill(IntNumBytes, FillValue);
}

void MCObjectStreamer::emitFill(const MCExpr &NumValues, int64_t Size,
                                int64_t Expr, SMLoc Loc) {
  int64_t IntNumValues;
  if (!NumValues.evaluateAsAbsolute(IntNumValues, getAssembler())) {
    getContext().reportError(Loc, "expected absolute expression");
    return;
  }

  if (IntNumValues < 0) {
    getContext().getSourceManager()->PrintMessage(
        Loc, SourceMgr::DK_Warning,
        "'.fill' directive with negative repeat count has no effect");
    return;
  }

  MCStreamer::emitFill(IntNumValues, Size, Expr);
}

void MCObjectStreamer::EmitFileDirective(StringRef Filename) {
  getAssembler().addFileName(Filename);
}

void MCObjectStreamer::FinishImpl() {
  // If we are generating dwarf for assembly source files dump out the sections.
  if (getContext().getGenDwarfForAssembly())
    MCGenDwarfInfo::Emit(this);

  // Dump out the dwarf file & directory tables and line tables.
  MCDwarfLineTable::Emit(this, getAssembler().getDWARFLinetableParams());

  flushPendingLabels(nullptr);
  getAssembler().Finish();
}