1//===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "llvm/MC/MCAssembler.h"
10#include "llvm/ADT/ArrayRef.h"
11#include "llvm/ADT/SmallString.h"
12#include "llvm/ADT/SmallVector.h"
13#include "llvm/ADT/Statistic.h"
14#include "llvm/ADT/StringRef.h"
15#include "llvm/ADT/Twine.h"
16#include "llvm/MC/MCAsmBackend.h"
17#include "llvm/MC/MCAsmInfo.h"
18#include "llvm/MC/MCAsmLayout.h"
19#include "llvm/MC/MCCodeEmitter.h"
20#include "llvm/MC/MCCodeView.h"
21#include "llvm/MC/MCContext.h"
22#include "llvm/MC/MCDwarf.h"
23#include "llvm/MC/MCExpr.h"
24#include "llvm/MC/MCFixup.h"
25#include "llvm/MC/MCFixupKindInfo.h"
26#include "llvm/MC/MCFragment.h"
27#include "llvm/MC/MCInst.h"
28#include "llvm/MC/MCObjectWriter.h"
29#include "llvm/MC/MCSection.h"
30#include "llvm/MC/MCSectionELF.h"
31#include "llvm/MC/MCSymbol.h"
32#include "llvm/MC/MCValue.h"
33#include "llvm/Support/Alignment.h"
34#include "llvm/Support/Casting.h"
35#include "llvm/Support/Debug.h"
36#include "llvm/Support/EndianStream.h"
37#include "llvm/Support/ErrorHandling.h"
38#include "llvm/Support/LEB128.h"
39#include "llvm/Support/MathExtras.h"
40#include "llvm/Support/raw_ostream.h"
41#include <cassert>
42#include <cstdint>
43#include <cstring>
44#include <tuple>
45#include <utility>
46
47using namespace llvm;
48
49#define DEBUG_TYPE "assembler"
50
51namespace {
52namespace stats {
53
54STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total");
55STATISTIC(EmittedRelaxableFragments,
56          "Number of emitted assembler fragments - relaxable");
57STATISTIC(EmittedDataFragments,
58          "Number of emitted assembler fragments - data");
59STATISTIC(EmittedCompactEncodedInstFragments,
60          "Number of emitted assembler fragments - compact encoded inst");
61STATISTIC(EmittedAlignFragments,
62          "Number of emitted assembler fragments - align");
63STATISTIC(EmittedFillFragments,
64          "Number of emitted assembler fragments - fill");
65STATISTIC(EmittedOrgFragments,
66          "Number of emitted assembler fragments - org");
67STATISTIC(evaluateFixup, "Number of evaluated fixups");
68STATISTIC(FragmentLayouts, "Number of fragment layouts");
69STATISTIC(ObjectBytes, "Number of emitted object file bytes");
70STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
71STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
72
73} // end namespace stats
74} // end anonymous namespace
75
76// FIXME FIXME FIXME: There are number of places in this file where we convert
77// what is a 64-bit assembler value used for computation into a value in the
78// object file, which may truncate it. We should detect that truncation where
79// invalid and report errors back.
80
81/* *** */
82
83MCAssembler::MCAssembler(MCContext &Context,
84                         std::unique_ptr<MCAsmBackend> Backend,
85                         std::unique_ptr<MCCodeEmitter> Emitter,
86                         std::unique_ptr<MCObjectWriter> Writer)
87    : Context(Context), Backend(std::move(Backend)),
88      Emitter(std::move(Emitter)), Writer(std::move(Writer)),
89      BundleAlignSize(0), RelaxAll(false), SubsectionsViaSymbols(false),
90      IncrementalLinkerCompatible(false), ELFHeaderEFlags(0) {
91  VersionInfo.Major = 0; // Major version == 0 for "none specified"
92}
93
94MCAssembler::~MCAssembler() = default;
95
96void MCAssembler::reset() {
97  Sections.clear();
98  Symbols.clear();
99  IndirectSymbols.clear();
100  DataRegions.clear();
101  LinkerOptions.clear();
102  FileNames.clear();
103  ThumbFuncs.clear();
104  BundleAlignSize = 0;
105  RelaxAll = false;
106  SubsectionsViaSymbols = false;
107  IncrementalLinkerCompatible = false;
108  ELFHeaderEFlags = 0;
109  LOHContainer.reset();
110  VersionInfo.Major = 0;
111  VersionInfo.SDKVersion = VersionTuple();
112
113  // reset objects owned by us
114  if (getBackendPtr())
115    getBackendPtr()->reset();
116  if (getEmitterPtr())
117    getEmitterPtr()->reset();
118  if (getWriterPtr())
119    getWriterPtr()->reset();
120  getLOHContainer().reset();
121}
122
123bool MCAssembler::registerSection(MCSection &Section) {
124  if (Section.isRegistered())
125    return false;
126  Sections.push_back(&Section);
127  Section.setIsRegistered(true);
128  return true;
129}
130
131bool MCAssembler::isThumbFunc(const MCSymbol *Symbol) const {
132  if (ThumbFuncs.count(Symbol))
133    return true;
134
135  if (!Symbol->isVariable())
136    return false;
137
138  const MCExpr *Expr = Symbol->getVariableValue();
139
140  MCValue V;
141  if (!Expr->evaluateAsRelocatable(V, nullptr, nullptr))
142    return false;
143
144  if (V.getSymB() || V.getRefKind() != MCSymbolRefExpr::VK_None)
145    return false;
146
147  const MCSymbolRefExpr *Ref = V.getSymA();
148  if (!Ref)
149    return false;
150
151  if (Ref->getKind() != MCSymbolRefExpr::VK_None)
152    return false;
153
154  const MCSymbol &Sym = Ref->getSymbol();
155  if (!isThumbFunc(&Sym))
156    return false;
157
158  ThumbFuncs.insert(Symbol); // Cache it.
159  return true;
160}
161
162bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
163  // Non-temporary labels should always be visible to the linker.
164  if (!Symbol.isTemporary())
165    return true;
166
167  if (Symbol.isUsedInReloc())
168    return true;
169
170  return false;
171}
172
173const MCSymbol *MCAssembler::getAtom(const MCSymbol &S) const {
174  // Linker visible symbols define atoms.
175  if (isSymbolLinkerVisible(S))
176    return &S;
177
178  // Absolute and undefined symbols have no defining atom.
179  if (!S.isInSection())
180    return nullptr;
181
182  // Non-linker visible symbols in sections which can't be atomized have no
183  // defining atom.
184  if (!getContext().getAsmInfo()->isSectionAtomizableBySymbols(
185          *S.getFragment()->getParent()))
186    return nullptr;
187
188  // Otherwise, return the atom for the containing fragment.
189  return S.getFragment()->getAtom();
190}
191
192bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
193                                const MCFixup &Fixup, const MCFragment *DF,
194                                MCValue &Target, uint64_t &Value,
195                                bool &WasForced) const {
196  ++stats::evaluateFixup;
197
198  // FIXME: This code has some duplication with recordRelocation. We should
199  // probably merge the two into a single callback that tries to evaluate a
200  // fixup and records a relocation if one is needed.
201
202  // On error claim to have completely evaluated the fixup, to prevent any
203  // further processing from being done.
204  const MCExpr *Expr = Fixup.getValue();
205  MCContext &Ctx = getContext();
206  Value = 0;
207  WasForced = false;
208  if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup)) {
209    Ctx.reportError(Fixup.getLoc(), "expected relocatable expression");
210    return true;
211  }
212  if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
213    if (RefB->getKind() != MCSymbolRefExpr::VK_None) {
214      Ctx.reportError(Fixup.getLoc(),
215                      "unsupported subtraction of qualified symbol");
216      return true;
217    }
218  }
219
220  assert(getBackendPtr() && "Expected assembler backend");
221  bool IsTarget = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags &
222                  MCFixupKindInfo::FKF_IsTarget;
223
224  if (IsTarget)
225    return getBackend().evaluateTargetFixup(*this, Layout, Fixup, DF, Target,
226                                            Value, WasForced);
227
228  unsigned FixupFlags = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags;
229  bool IsPCRel = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags &
230                 MCFixupKindInfo::FKF_IsPCRel;
231
232  bool IsResolved = false;
233  if (IsPCRel) {
234    if (Target.getSymB()) {
235      IsResolved = false;
236    } else if (!Target.getSymA()) {
237      IsResolved = false;
238    } else {
239      const MCSymbolRefExpr *A = Target.getSymA();
240      const MCSymbol &SA = A->getSymbol();
241      if (A->getKind() != MCSymbolRefExpr::VK_None || SA.isUndefined()) {
242        IsResolved = false;
243      } else if (auto *Writer = getWriterPtr()) {
244        IsResolved = (FixupFlags & MCFixupKindInfo::FKF_Constant) ||
245                     Writer->isSymbolRefDifferenceFullyResolvedImpl(
246                         *this, SA, *DF, false, true);
247      }
248    }
249  } else {
250    IsResolved = Target.isAbsolute();
251  }
252
253  Value = Target.getConstant();
254
255  if (const MCSymbolRefExpr *A = Target.getSymA()) {
256    const MCSymbol &Sym = A->getSymbol();
257    if (Sym.isDefined())
258      Value += Layout.getSymbolOffset(Sym);
259  }
260  if (const MCSymbolRefExpr *B = Target.getSymB()) {
261    const MCSymbol &Sym = B->getSymbol();
262    if (Sym.isDefined())
263      Value -= Layout.getSymbolOffset(Sym);
264  }
265
266  bool ShouldAlignPC = getBackend().getFixupKindInfo(Fixup.getKind()).Flags &
267                       MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
268  assert((ShouldAlignPC ? IsPCRel : true) &&
269    "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");
270
271  if (IsPCRel) {
272    uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();
273
274    // A number of ARM fixups in Thumb mode require that the effective PC
275    // address be determined as the 32-bit aligned version of the actual offset.
276    if (ShouldAlignPC) Offset &= ~0x3;
277    Value -= Offset;
278  }
279
280  // Let the backend force a relocation if needed.
281  if (IsResolved && getBackend().shouldForceRelocation(*this, Fixup, Target)) {
282    IsResolved = false;
283    WasForced = true;
284  }
285
286  return IsResolved;
287}
288
289uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
290                                          const MCFragment &F) const {
291  assert(getBackendPtr() && "Requires assembler backend");
292  switch (F.getKind()) {
293  case MCFragment::FT_Data:
294    return cast<MCDataFragment>(F).getContents().size();
295  case MCFragment::FT_Relaxable:
296    return cast<MCRelaxableFragment>(F).getContents().size();
297  case MCFragment::FT_CompactEncodedInst:
298    return cast<MCCompactEncodedInstFragment>(F).getContents().size();
299  case MCFragment::FT_Fill: {
300    auto &FF = cast<MCFillFragment>(F);
301    int64_t NumValues = 0;
302    if (!FF.getNumValues().evaluateAsAbsolute(NumValues, Layout)) {
303      getContext().reportError(FF.getLoc(),
304                               "expected assembly-time absolute expression");
305      return 0;
306    }
307    int64_t Size = NumValues * FF.getValueSize();
308    if (Size < 0) {
309      getContext().reportError(FF.getLoc(), "invalid number of bytes");
310      return 0;
311    }
312    return Size;
313  }
314
315  case MCFragment::FT_LEB:
316    return cast<MCLEBFragment>(F).getContents().size();
317
318  case MCFragment::FT_BoundaryAlign:
319    return cast<MCBoundaryAlignFragment>(F).getSize();
320
321  case MCFragment::FT_SymbolId:
322    return 4;
323
324  case MCFragment::FT_Align: {
325    const MCAlignFragment &AF = cast<MCAlignFragment>(F);
326    unsigned Offset = Layout.getFragmentOffset(&AF);
327    unsigned Size = offsetToAlignment(Offset, Align(AF.getAlignment()));
328
329    // Insert extra Nops for code alignment if the target define
330    // shouldInsertExtraNopBytesForCodeAlign target hook.
331    if (AF.getParent()->UseCodeAlign() && AF.hasEmitNops() &&
332        getBackend().shouldInsertExtraNopBytesForCodeAlign(AF, Size))
333      return Size;
334
335    // If we are padding with nops, force the padding to be larger than the
336    // minimum nop size.
337    if (Size > 0 && AF.hasEmitNops()) {
338      while (Size % getBackend().getMinimumNopSize())
339        Size += AF.getAlignment();
340    }
341    if (Size > AF.getMaxBytesToEmit())
342      return 0;
343    return Size;
344  }
345
346  case MCFragment::FT_Org: {
347    const MCOrgFragment &OF = cast<MCOrgFragment>(F);
348    MCValue Value;
349    if (!OF.getOffset().evaluateAsValue(Value, Layout)) {
350      getContext().reportError(OF.getLoc(),
351                               "expected assembly-time absolute expression");
352        return 0;
353    }
354
355    uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
356    int64_t TargetLocation = Value.getConstant();
357    if (const MCSymbolRefExpr *A = Value.getSymA()) {
358      uint64_t Val;
359      if (!Layout.getSymbolOffset(A->getSymbol(), Val)) {
360        getContext().reportError(OF.getLoc(), "expected absolute expression");
361        return 0;
362      }
363      TargetLocation += Val;
364    }
365    int64_t Size = TargetLocation - FragmentOffset;
366    if (Size < 0 || Size >= 0x40000000) {
367      getContext().reportError(
368          OF.getLoc(), "invalid .org offset '" + Twine(TargetLocation) +
369                           "' (at offset '" + Twine(FragmentOffset) + "')");
370      return 0;
371    }
372    return Size;
373  }
374
375  case MCFragment::FT_Dwarf:
376    return cast<MCDwarfLineAddrFragment>(F).getContents().size();
377  case MCFragment::FT_DwarfFrame:
378    return cast<MCDwarfCallFrameFragment>(F).getContents().size();
379  case MCFragment::FT_CVInlineLines:
380    return cast<MCCVInlineLineTableFragment>(F).getContents().size();
381  case MCFragment::FT_CVDefRange:
382    return cast<MCCVDefRangeFragment>(F).getContents().size();
383  case MCFragment::FT_Dummy:
384    llvm_unreachable("Should not have been added");
385  }
386
387  llvm_unreachable("invalid fragment kind");
388}
389
390void MCAsmLayout::layoutFragment(MCFragment *F) {
391  MCFragment *Prev = F->getPrevNode();
392
393  // We should never try to recompute something which is valid.
394  assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
395  // We should never try to compute the fragment layout if its predecessor
396  // isn't valid.
397  assert((!Prev || isFragmentValid(Prev)) &&
398         "Attempt to compute fragment before its predecessor!");
399
400  assert(!F->IsBeingLaidOut && "Already being laid out!");
401  F->IsBeingLaidOut = true;
402
403  ++stats::FragmentLayouts;
404
405  // Compute fragment offset and size.
406  if (Prev)
407    F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
408  else
409    F->Offset = 0;
410  F->IsBeingLaidOut = false;
411  LastValidFragment[F->getParent()] = F;
412
413  // If bundling is enabled and this fragment has instructions in it, it has to
414  // obey the bundling restrictions. With padding, we'll have:
415  //
416  //
417  //        BundlePadding
418  //             |||
419  // -------------------------------------
420  //   Prev  |##########|       F        |
421  // -------------------------------------
422  //                    ^
423  //                    |
424  //                    F->Offset
425  //
426  // The fragment's offset will point to after the padding, and its computed
427  // size won't include the padding.
428  //
429  // When the -mc-relax-all flag is used, we optimize bundling by writting the
430  // padding directly into fragments when the instructions are emitted inside
431  // the streamer. When the fragment is larger than the bundle size, we need to
432  // ensure that it's bundle aligned. This means that if we end up with
433  // multiple fragments, we must emit bundle padding between fragments.
434  //
435  // ".align N" is an example of a directive that introduces multiple
436  // fragments. We could add a special case to handle ".align N" by emitting
437  // within-fragment padding (which would produce less padding when N is less
438  // than the bundle size), but for now we don't.
439  //
440  if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
441    assert(isa<MCEncodedFragment>(F) &&
442           "Only MCEncodedFragment implementations have instructions");
443    MCEncodedFragment *EF = cast<MCEncodedFragment>(F);
444    uint64_t FSize = Assembler.computeFragmentSize(*this, *EF);
445
446    if (!Assembler.getRelaxAll() && FSize > Assembler.getBundleAlignSize())
447      report_fatal_error("Fragment can't be larger than a bundle size");
448
449    uint64_t RequiredBundlePadding =
450        computeBundlePadding(Assembler, EF, EF->Offset, FSize);
451    if (RequiredBundlePadding > UINT8_MAX)
452      report_fatal_error("Padding cannot exceed 255 bytes");
453    EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
454    EF->Offset += RequiredBundlePadding;
455  }
456}
457
458void MCAssembler::registerSymbol(const MCSymbol &Symbol, bool *Created) {
459  bool New = !Symbol.isRegistered();
460  if (Created)
461    *Created = New;
462  if (New) {
463    Symbol.setIsRegistered(true);
464    Symbols.push_back(&Symbol);
465  }
466}
467
468void MCAssembler::writeFragmentPadding(raw_ostream &OS,
469                                       const MCEncodedFragment &EF,
470                                       uint64_t FSize) const {
471  assert(getBackendPtr() && "Expected assembler backend");
472  // Should NOP padding be written out before this fragment?
473  unsigned BundlePadding = EF.getBundlePadding();
474  if (BundlePadding > 0) {
475    assert(isBundlingEnabled() &&
476           "Writing bundle padding with disabled bundling");
477    assert(EF.hasInstructions() &&
478           "Writing bundle padding for a fragment without instructions");
479
480    unsigned TotalLength = BundlePadding + static_cast<unsigned>(FSize);
481    if (EF.alignToBundleEnd() && TotalLength > getBundleAlignSize()) {
482      // If the padding itself crosses a bundle boundary, it must be emitted
483      // in 2 pieces, since even nop instructions must not cross boundaries.
484      //             v--------------v   <- BundleAlignSize
485      //        v---------v             <- BundlePadding
486      // ----------------------------
487      // | Prev |####|####|    F    |
488      // ----------------------------
489      //        ^-------------------^   <- TotalLength
490      unsigned DistanceToBoundary = TotalLength - getBundleAlignSize();
491      if (!getBackend().writeNopData(OS, DistanceToBoundary))
492        report_fatal_error("unable to write NOP sequence of " +
493                           Twine(DistanceToBoundary) + " bytes");
494      BundlePadding -= DistanceToBoundary;
495    }
496    if (!getBackend().writeNopData(OS, BundlePadding))
497      report_fatal_error("unable to write NOP sequence of " +
498                         Twine(BundlePadding) + " bytes");
499  }
500}
501
502/// Write the fragment \p F to the output file.
503static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
504                          const MCAsmLayout &Layout, const MCFragment &F) {
505  // FIXME: Embed in fragments instead?
506  uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
507
508  support::endianness Endian = Asm.getBackend().Endian;
509
510  if (const MCEncodedFragment *EF = dyn_cast<MCEncodedFragment>(&F))
511    Asm.writeFragmentPadding(OS, *EF, FragmentSize);
512
513  // This variable (and its dummy usage) is to participate in the assert at
514  // the end of the function.
515  uint64_t Start = OS.tell();
516  (void) Start;
517
518  ++stats::EmittedFragments;
519
520  switch (F.getKind()) {
521  case MCFragment::FT_Align: {
522    ++stats::EmittedAlignFragments;
523    const MCAlignFragment &AF = cast<MCAlignFragment>(F);
524    assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
525
526    uint64_t Count = FragmentSize / AF.getValueSize();
527
528    // FIXME: This error shouldn't actually occur (the front end should emit
529    // multiple .align directives to enforce the semantics it wants), but is
530    // severe enough that we want to report it. How to handle this?
531    if (Count * AF.getValueSize() != FragmentSize)
532      report_fatal_error("undefined .align directive, value size '" +
533                        Twine(AF.getValueSize()) +
534                        "' is not a divisor of padding size '" +
535                        Twine(FragmentSize) + "'");
536
537    // See if we are aligning with nops, and if so do that first to try to fill
538    // the Count bytes.  Then if that did not fill any bytes or there are any
539    // bytes left to fill use the Value and ValueSize to fill the rest.
540    // If we are aligning with nops, ask that target to emit the right data.
541    if (AF.hasEmitNops()) {
542      if (!Asm.getBackend().writeNopData(OS, Count))
543        report_fatal_error("unable to write nop sequence of " +
544                          Twine(Count) + " bytes");
545      break;
546    }
547
548    // Otherwise, write out in multiples of the value size.
549    for (uint64_t i = 0; i != Count; ++i) {
550      switch (AF.getValueSize()) {
551      default: llvm_unreachable("Invalid size!");
552      case 1: OS << char(AF.getValue()); break;
553      case 2:
554        support::endian::write<uint16_t>(OS, AF.getValue(), Endian);
555        break;
556      case 4:
557        support::endian::write<uint32_t>(OS, AF.getValue(), Endian);
558        break;
559      case 8:
560        support::endian::write<uint64_t>(OS, AF.getValue(), Endian);
561        break;
562      }
563    }
564    break;
565  }
566
567  case MCFragment::FT_Data:
568    ++stats::EmittedDataFragments;
569    OS << cast<MCDataFragment>(F).getContents();
570    break;
571
572  case MCFragment::FT_Relaxable:
573    ++stats::EmittedRelaxableFragments;
574    OS << cast<MCRelaxableFragment>(F).getContents();
575    break;
576
577  case MCFragment::FT_CompactEncodedInst:
578    ++stats::EmittedCompactEncodedInstFragments;
579    OS << cast<MCCompactEncodedInstFragment>(F).getContents();
580    break;
581
582  case MCFragment::FT_Fill: {
583    ++stats::EmittedFillFragments;
584    const MCFillFragment &FF = cast<MCFillFragment>(F);
585    uint64_t V = FF.getValue();
586    unsigned VSize = FF.getValueSize();
587    const unsigned MaxChunkSize = 16;
588    char Data[MaxChunkSize];
589    assert(0 < VSize && VSize <= MaxChunkSize && "Illegal fragment fill size");
590    // Duplicate V into Data as byte vector to reduce number of
591    // writes done. As such, do endian conversion here.
592    for (unsigned I = 0; I != VSize; ++I) {
593      unsigned index = Endian == support::little ? I : (VSize - I - 1);
594      Data[I] = uint8_t(V >> (index * 8));
595    }
596    for (unsigned I = VSize; I < MaxChunkSize; ++I)
597      Data[I] = Data[I - VSize];
598
599    // Set to largest multiple of VSize in Data.
600    const unsigned NumPerChunk = MaxChunkSize / VSize;
601    // Set ChunkSize to largest multiple of VSize in Data
602    const unsigned ChunkSize = VSize * NumPerChunk;
603
604    // Do copies by chunk.
605    StringRef Ref(Data, ChunkSize);
606    for (uint64_t I = 0, E = FragmentSize / ChunkSize; I != E; ++I)
607      OS << Ref;
608
609    // do remainder if needed.
610    unsigned TrailingCount = FragmentSize % ChunkSize;
611    if (TrailingCount)
612      OS.write(Data, TrailingCount);
613    break;
614  }
615
616  case MCFragment::FT_LEB: {
617    const MCLEBFragment &LF = cast<MCLEBFragment>(F);
618    OS << LF.getContents();
619    break;
620  }
621
622  case MCFragment::FT_BoundaryAlign: {
623    if (!Asm.getBackend().writeNopData(OS, FragmentSize))
624      report_fatal_error("unable to write nop sequence of " +
625                         Twine(FragmentSize) + " bytes");
626    break;
627  }
628
629  case MCFragment::FT_SymbolId: {
630    const MCSymbolIdFragment &SF = cast<MCSymbolIdFragment>(F);
631    support::endian::write<uint32_t>(OS, SF.getSymbol()->getIndex(), Endian);
632    break;
633  }
634
635  case MCFragment::FT_Org: {
636    ++stats::EmittedOrgFragments;
637    const MCOrgFragment &OF = cast<MCOrgFragment>(F);
638
639    for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
640      OS << char(OF.getValue());
641
642    break;
643  }
644
645  case MCFragment::FT_Dwarf: {
646    const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
647    OS << OF.getContents();
648    break;
649  }
650  case MCFragment::FT_DwarfFrame: {
651    const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
652    OS << CF.getContents();
653    break;
654  }
655  case MCFragment::FT_CVInlineLines: {
656    const auto &OF = cast<MCCVInlineLineTableFragment>(F);
657    OS << OF.getContents();
658    break;
659  }
660  case MCFragment::FT_CVDefRange: {
661    const auto &DRF = cast<MCCVDefRangeFragment>(F);
662    OS << DRF.getContents();
663    break;
664  }
665  case MCFragment::FT_Dummy:
666    llvm_unreachable("Should not have been added");
667  }
668
669  assert(OS.tell() - Start == FragmentSize &&
670         "The stream should advance by fragment size");
671}
672
673void MCAssembler::writeSectionData(raw_ostream &OS, const MCSection *Sec,
674                                   const MCAsmLayout &Layout) const {
675  assert(getBackendPtr() && "Expected assembler backend");
676
677  // Ignore virtual sections.
678  if (Sec->isVirtualSection()) {
679    assert(Layout.getSectionFileSize(Sec) == 0 && "Invalid size for section!");
680
681    // Check that contents are only things legal inside a virtual section.
682    for (const MCFragment &F : *Sec) {
683      switch (F.getKind()) {
684      default: llvm_unreachable("Invalid fragment in virtual section!");
685      case MCFragment::FT_Data: {
686        // Check that we aren't trying to write a non-zero contents (or fixups)
687        // into a virtual section. This is to support clients which use standard
688        // directives to fill the contents of virtual sections.
689        const MCDataFragment &DF = cast<MCDataFragment>(F);
690        if (DF.fixup_begin() != DF.fixup_end())
691          getContext().reportError(SMLoc(), Sec->getVirtualSectionKind() +
692                                                " section '" + Sec->getName() +
693                                                "' cannot have fixups");
694        for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
695          if (DF.getContents()[i]) {
696            getContext().reportError(SMLoc(),
697                                     Sec->getVirtualSectionKind() +
698                                         " section '" + Sec->getName() +
699                                         "' cannot have non-zero initializers");
700            break;
701          }
702        break;
703      }
704      case MCFragment::FT_Align:
705        // Check that we aren't trying to write a non-zero value into a virtual
706        // section.
707        assert((cast<MCAlignFragment>(F).getValueSize() == 0 ||
708                cast<MCAlignFragment>(F).getValue() == 0) &&
709               "Invalid align in virtual section!");
710        break;
711      case MCFragment::FT_Fill:
712        assert((cast<MCFillFragment>(F).getValue() == 0) &&
713               "Invalid fill in virtual section!");
714        break;
715      }
716    }
717
718    return;
719  }
720
721  uint64_t Start = OS.tell();
722  (void)Start;
723
724  for (const MCFragment &F : *Sec)
725    writeFragment(OS, *this, Layout, F);
726
727  assert(OS.tell() - Start == Layout.getSectionAddressSize(Sec));
728}
729
730std::tuple<MCValue, uint64_t, bool>
731MCAssembler::handleFixup(const MCAsmLayout &Layout, MCFragment &F,
732                         const MCFixup &Fixup) {
733  // Evaluate the fixup.
734  MCValue Target;
735  uint64_t FixedValue;
736  bool WasForced;
737  bool IsResolved = evaluateFixup(Layout, Fixup, &F, Target, FixedValue,
738                                  WasForced);
739  if (!IsResolved) {
740    // The fixup was unresolved, we need a relocation. Inform the object
741    // writer of the relocation, and give it an opportunity to adjust the
742    // fixup value if need be.
743    if (Target.getSymA() && Target.getSymB() &&
744        getBackend().requiresDiffExpressionRelocations()) {
745      // The fixup represents the difference between two symbols, which the
746      // backend has indicated must be resolved at link time. Split up the fixup
747      // into two relocations, one for the add, and one for the sub, and emit
748      // both of these. The constant will be associated with the add half of the
749      // expression.
750      MCFixup FixupAdd = MCFixup::createAddFor(Fixup);
751      MCValue TargetAdd =
752          MCValue::get(Target.getSymA(), nullptr, Target.getConstant());
753      getWriter().recordRelocation(*this, Layout, &F, FixupAdd, TargetAdd,
754                                   FixedValue);
755      MCFixup FixupSub = MCFixup::createSubFor(Fixup);
756      MCValue TargetSub = MCValue::get(Target.getSymB());
757      getWriter().recordRelocation(*this, Layout, &F, FixupSub, TargetSub,
758                                   FixedValue);
759    } else {
760      getWriter().recordRelocation(*this, Layout, &F, Fixup, Target,
761                                   FixedValue);
762    }
763  }
764  return std::make_tuple(Target, FixedValue, IsResolved);
765}
766
767void MCAssembler::layout(MCAsmLayout &Layout) {
768  assert(getBackendPtr() && "Expected assembler backend");
769  DEBUG_WITH_TYPE("mc-dump", {
770      errs() << "assembler backend - pre-layout\n--\n";
771      dump(); });
772
773  // Create dummy fragments and assign section ordinals.
774  unsigned SectionIndex = 0;
775  for (MCSection &Sec : *this) {
776    // Create dummy fragments to eliminate any empty sections, this simplifies
777    // layout.
778    if (Sec.getFragmentList().empty())
779      new MCDataFragment(&Sec);
780
781    Sec.setOrdinal(SectionIndex++);
782  }
783
784  // Assign layout order indices to sections and fragments.
785  for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
786    MCSection *Sec = Layout.getSectionOrder()[i];
787    Sec->setLayoutOrder(i);
788
789    unsigned FragmentIndex = 0;
790    for (MCFragment &Frag : *Sec)
791      Frag.setLayoutOrder(FragmentIndex++);
792  }
793
794  // Layout until everything fits.
795  while (layoutOnce(Layout)) {
796    if (getContext().hadError())
797      return;
798    // Size of fragments in one section can depend on the size of fragments in
799    // another. If any fragment has changed size, we have to re-layout (and
800    // as a result possibly further relax) all.
801    for (MCSection &Sec : *this)
802      Layout.invalidateFragmentsFrom(&*Sec.begin());
803  }
804
805  DEBUG_WITH_TYPE("mc-dump", {
806      errs() << "assembler backend - post-relaxation\n--\n";
807      dump(); });
808
809  // Finalize the layout, including fragment lowering.
810  finishLayout(Layout);
811
812  DEBUG_WITH_TYPE("mc-dump", {
813      errs() << "assembler backend - final-layout\n--\n";
814      dump(); });
815
816  // Allow the object writer a chance to perform post-layout binding (for
817  // example, to set the index fields in the symbol data).
818  getWriter().executePostLayoutBinding(*this, Layout);
819
820  // Evaluate and apply the fixups, generating relocation entries as necessary.
821  for (MCSection &Sec : *this) {
822    for (MCFragment &Frag : Sec) {
823      ArrayRef<MCFixup> Fixups;
824      MutableArrayRef<char> Contents;
825      const MCSubtargetInfo *STI = nullptr;
826
827      // Process MCAlignFragment and MCEncodedFragmentWithFixups here.
828      switch (Frag.getKind()) {
829      default:
830        continue;
831      case MCFragment::FT_Align: {
832        MCAlignFragment &AF = cast<MCAlignFragment>(Frag);
833        // Insert fixup type for code alignment if the target define
834        // shouldInsertFixupForCodeAlign target hook.
835        if (Sec.UseCodeAlign() && AF.hasEmitNops())
836          getBackend().shouldInsertFixupForCodeAlign(*this, Layout, AF);
837        continue;
838      }
839      case MCFragment::FT_Data: {
840        MCDataFragment &DF = cast<MCDataFragment>(Frag);
841        Fixups = DF.getFixups();
842        Contents = DF.getContents();
843        STI = DF.getSubtargetInfo();
844        assert(!DF.hasInstructions() || STI != nullptr);
845        break;
846      }
847      case MCFragment::FT_Relaxable: {
848        MCRelaxableFragment &RF = cast<MCRelaxableFragment>(Frag);
849        Fixups = RF.getFixups();
850        Contents = RF.getContents();
851        STI = RF.getSubtargetInfo();
852        assert(!RF.hasInstructions() || STI != nullptr);
853        break;
854      }
855      case MCFragment::FT_CVDefRange: {
856        MCCVDefRangeFragment &CF = cast<MCCVDefRangeFragment>(Frag);
857        Fixups = CF.getFixups();
858        Contents = CF.getContents();
859        break;
860      }
861      case MCFragment::FT_Dwarf: {
862        MCDwarfLineAddrFragment &DF = cast<MCDwarfLineAddrFragment>(Frag);
863        Fixups = DF.getFixups();
864        Contents = DF.getContents();
865        break;
866      }
867      case MCFragment::FT_DwarfFrame: {
868        MCDwarfCallFrameFragment &DF = cast<MCDwarfCallFrameFragment>(Frag);
869        Fixups = DF.getFixups();
870        Contents = DF.getContents();
871        break;
872      }
873      }
874      for (const MCFixup &Fixup : Fixups) {
875        uint64_t FixedValue;
876        bool IsResolved;
877        MCValue Target;
878        std::tie(Target, FixedValue, IsResolved) =
879            handleFixup(Layout, Frag, Fixup);
880        getBackend().applyFixup(*this, Fixup, Target, Contents, FixedValue,
881                                IsResolved, STI);
882      }
883    }
884  }
885}
886
887void MCAssembler::Finish() {
888  // Create the layout object.
889  MCAsmLayout Layout(*this);
890  layout(Layout);
891
892  // Write the object file.
893  stats::ObjectBytes += getWriter().writeObject(*this, Layout);
894}
895
896bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
897                                       const MCRelaxableFragment *DF,
898                                       const MCAsmLayout &Layout) const {
899  assert(getBackendPtr() && "Expected assembler backend");
900  MCValue Target;
901  uint64_t Value;
902  bool WasForced;
903  bool Resolved = evaluateFixup(Layout, Fixup, DF, Target, Value, WasForced);
904  if (Target.getSymA() &&
905      Target.getSymA()->getKind() == MCSymbolRefExpr::VK_X86_ABS8 &&
906      Fixup.getKind() == FK_Data_1)
907    return false;
908  return getBackend().fixupNeedsRelaxationAdvanced(Fixup, Resolved, Value, DF,
909                                                   Layout, WasForced);
910}
911
912bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
913                                          const MCAsmLayout &Layout) const {
914  assert(getBackendPtr() && "Expected assembler backend");
915  // If this inst doesn't ever need relaxation, ignore it. This occurs when we
916  // are intentionally pushing out inst fragments, or because we relaxed a
917  // previous instruction to one that doesn't need relaxation.
918  if (!getBackend().mayNeedRelaxation(F->getInst(), *F->getSubtargetInfo()))
919    return false;
920
921  for (const MCFixup &Fixup : F->getFixups())
922    if (fixupNeedsRelaxation(Fixup, F, Layout))
923      return true;
924
925  return false;
926}
927
928bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
929                                   MCRelaxableFragment &F) {
930  assert(getEmitterPtr() &&
931         "Expected CodeEmitter defined for relaxInstruction");
932  if (!fragmentNeedsRelaxation(&F, Layout))
933    return false;
934
935  ++stats::RelaxedInstructions;
936
937  // FIXME-PERF: We could immediately lower out instructions if we can tell
938  // they are fully resolved, to avoid retesting on later passes.
939
940  // Relax the fragment.
941
942  MCInst Relaxed = F.getInst();
943  getBackend().relaxInstruction(Relaxed, *F.getSubtargetInfo());
944
945  // Encode the new instruction.
946  //
947  // FIXME-PERF: If it matters, we could let the target do this. It can
948  // probably do so more efficiently in many cases.
949  SmallVector<MCFixup, 4> Fixups;
950  SmallString<256> Code;
951  raw_svector_ostream VecOS(Code);
952  getEmitter().encodeInstruction(Relaxed, VecOS, Fixups, *F.getSubtargetInfo());
953
954  // Update the fragment.
955  F.setInst(Relaxed);
956  F.getContents() = Code;
957  F.getFixups() = Fixups;
958
959  return true;
960}
961
962bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
963  uint64_t OldSize = LF.getContents().size();
964  int64_t Value;
965  bool Abs = LF.getValue().evaluateKnownAbsolute(Value, Layout);
966  if (!Abs)
967    report_fatal_error("sleb128 and uleb128 expressions must be absolute");
968  SmallString<8> &Data = LF.getContents();
969  Data.clear();
970  raw_svector_ostream OSE(Data);
971  // The compiler can generate EH table assembly that is impossible to assemble
972  // without either adding padding to an LEB fragment or adding extra padding
973  // to a later alignment fragment. To accommodate such tables, relaxation can
974  // only increase an LEB fragment size here, not decrease it. See PR35809.
975  if (LF.isSigned())
976    encodeSLEB128(Value, OSE, OldSize);
977  else
978    encodeULEB128(Value, OSE, OldSize);
979  return OldSize != LF.getContents().size();
980}
981
982/// Check if the branch crosses the boundary.
983///
984/// \param StartAddr start address of the fused/unfused branch.
985/// \param Size size of the fused/unfused branch.
986/// \param BoundaryAlignment alignment requirement of the branch.
987/// \returns true if the branch cross the boundary.
988static bool mayCrossBoundary(uint64_t StartAddr, uint64_t Size,
989                             Align BoundaryAlignment) {
990  uint64_t EndAddr = StartAddr + Size;
991  return (StartAddr >> Log2(BoundaryAlignment)) !=
992         ((EndAddr - 1) >> Log2(BoundaryAlignment));
993}
994
995/// Check if the branch is against the boundary.
996///
997/// \param StartAddr start address of the fused/unfused branch.
998/// \param Size size of the fused/unfused branch.
999/// \param BoundaryAlignment alignment requirement of the branch.
1000/// \returns true if the branch is against the boundary.
1001static bool isAgainstBoundary(uint64_t StartAddr, uint64_t Size,
1002                              Align BoundaryAlignment) {
1003  uint64_t EndAddr = StartAddr + Size;
1004  return (EndAddr & (BoundaryAlignment.value() - 1)) == 0;
1005}
1006
1007/// Check if the branch needs padding.
1008///
1009/// \param StartAddr start address of the fused/unfused branch.
1010/// \param Size size of the fused/unfused branch.
1011/// \param BoundaryAlignment alignment requirement of the branch.
1012/// \returns true if the branch needs padding.
1013static bool needPadding(uint64_t StartAddr, uint64_t Size,
1014                        Align BoundaryAlignment) {
1015  return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) ||
1016         isAgainstBoundary(StartAddr, Size, BoundaryAlignment);
1017}
1018
1019bool MCAssembler::relaxBoundaryAlign(MCAsmLayout &Layout,
1020                                     MCBoundaryAlignFragment &BF) {
1021  // BoundaryAlignFragment that doesn't need to align any fragment should not be
1022  // relaxed.
1023  if (!BF.getLastFragment())
1024    return false;
1025
1026  uint64_t AlignedOffset = Layout.getFragmentOffset(&BF);
1027  uint64_t AlignedSize = 0;
1028  for (const MCFragment *F = BF.getLastFragment(); F != &BF;
1029       F = F->getPrevNode())
1030    AlignedSize += computeFragmentSize(Layout, *F);
1031
1032  Align BoundaryAlignment = BF.getAlignment();
1033  uint64_t NewSize = needPadding(AlignedOffset, AlignedSize, BoundaryAlignment)
1034                         ? offsetToAlignment(AlignedOffset, BoundaryAlignment)
1035                         : 0U;
1036  if (NewSize == BF.getSize())
1037    return false;
1038  BF.setSize(NewSize);
1039  Layout.invalidateFragmentsFrom(&BF);
1040  return true;
1041}
1042
1043bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
1044                                     MCDwarfLineAddrFragment &DF) {
1045  MCContext &Context = Layout.getAssembler().getContext();
1046  uint64_t OldSize = DF.getContents().size();
1047  int64_t AddrDelta;
1048  bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1049  assert(Abs && "We created a line delta with an invalid expression");
1050  (void)Abs;
1051  int64_t LineDelta;
1052  LineDelta = DF.getLineDelta();
1053  SmallVectorImpl<char> &Data = DF.getContents();
1054  Data.clear();
1055  raw_svector_ostream OSE(Data);
1056  DF.getFixups().clear();
1057
1058  if (!getBackend().requiresDiffExpressionRelocations()) {
1059    MCDwarfLineAddr::Encode(Context, getDWARFLinetableParams(), LineDelta,
1060                            AddrDelta, OSE);
1061  } else {
1062    uint32_t Offset;
1063    uint32_t Size;
1064    bool SetDelta = MCDwarfLineAddr::FixedEncode(Context,
1065                                                 getDWARFLinetableParams(),
1066                                                 LineDelta, AddrDelta,
1067                                                 OSE, &Offset, &Size);
1068    // Add Fixups for address delta or new address.
1069    const MCExpr *FixupExpr;
1070    if (SetDelta) {
1071      FixupExpr = &DF.getAddrDelta();
1072    } else {
1073      const MCBinaryExpr *ABE = cast<MCBinaryExpr>(&DF.getAddrDelta());
1074      FixupExpr = ABE->getLHS();
1075    }
1076    DF.getFixups().push_back(
1077        MCFixup::create(Offset, FixupExpr,
1078                        MCFixup::getKindForSize(Size, false /*isPCRel*/)));
1079  }
1080
1081  return OldSize != Data.size();
1082}
1083
1084bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
1085                                              MCDwarfCallFrameFragment &DF) {
1086  MCContext &Context = Layout.getAssembler().getContext();
1087  uint64_t OldSize = DF.getContents().size();
1088  int64_t AddrDelta;
1089  bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1090  assert(Abs && "We created call frame with an invalid expression");
1091  (void) Abs;
1092  SmallVectorImpl<char> &Data = DF.getContents();
1093  Data.clear();
1094  raw_svector_ostream OSE(Data);
1095  DF.getFixups().clear();
1096
1097  if (getBackend().requiresDiffExpressionRelocations()) {
1098    uint32_t Offset;
1099    uint32_t Size;
1100    MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE, &Offset,
1101                                          &Size);
1102    if (Size) {
1103      DF.getFixups().push_back(MCFixup::create(
1104          Offset, &DF.getAddrDelta(),
1105          MCFixup::getKindForSizeInBits(Size /*In bits.*/, false /*isPCRel*/)));
1106    }
1107  } else {
1108    MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE);
1109  }
1110
1111  return OldSize != Data.size();
1112}
1113
1114bool MCAssembler::relaxCVInlineLineTable(MCAsmLayout &Layout,
1115                                         MCCVInlineLineTableFragment &F) {
1116  unsigned OldSize = F.getContents().size();
1117  getContext().getCVContext().encodeInlineLineTable(Layout, F);
1118  return OldSize != F.getContents().size();
1119}
1120
1121bool MCAssembler::relaxCVDefRange(MCAsmLayout &Layout,
1122                                  MCCVDefRangeFragment &F) {
1123  unsigned OldSize = F.getContents().size();
1124  getContext().getCVContext().encodeDefRange(Layout, F);
1125  return OldSize != F.getContents().size();
1126}
1127
1128bool MCAssembler::relaxFragment(MCAsmLayout &Layout, MCFragment &F) {
1129  switch(F.getKind()) {
1130  default:
1131    return false;
1132  case MCFragment::FT_Relaxable:
1133    assert(!getRelaxAll() &&
1134           "Did not expect a MCRelaxableFragment in RelaxAll mode");
1135    return relaxInstruction(Layout, cast<MCRelaxableFragment>(F));
1136  case MCFragment::FT_Dwarf:
1137    return relaxDwarfLineAddr(Layout, cast<MCDwarfLineAddrFragment>(F));
1138  case MCFragment::FT_DwarfFrame:
1139    return relaxDwarfCallFrameFragment(Layout,
1140                                       cast<MCDwarfCallFrameFragment>(F));
1141  case MCFragment::FT_LEB:
1142    return relaxLEB(Layout, cast<MCLEBFragment>(F));
1143  case MCFragment::FT_BoundaryAlign:
1144    return relaxBoundaryAlign(Layout, cast<MCBoundaryAlignFragment>(F));
1145  case MCFragment::FT_CVInlineLines:
1146    return relaxCVInlineLineTable(Layout, cast<MCCVInlineLineTableFragment>(F));
1147  case MCFragment::FT_CVDefRange:
1148    return relaxCVDefRange(Layout, cast<MCCVDefRangeFragment>(F));
1149  }
1150}
1151
1152bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec) {
1153  // Holds the first fragment which needed relaxing during this layout. It will
1154  // remain NULL if none were relaxed.
1155  // When a fragment is relaxed, all the fragments following it should get
1156  // invalidated because their offset is going to change.
1157  MCFragment *FirstRelaxedFragment = nullptr;
1158
1159  // Attempt to relax all the fragments in the section.
1160  for (MCFragment &Frag : Sec) {
1161    // Check if this is a fragment that needs relaxation.
1162    bool RelaxedFrag = relaxFragment(Layout, Frag);
1163    if (RelaxedFrag && !FirstRelaxedFragment)
1164      FirstRelaxedFragment = &Frag;
1165  }
1166  if (FirstRelaxedFragment) {
1167    Layout.invalidateFragmentsFrom(FirstRelaxedFragment);
1168    return true;
1169  }
1170  return false;
1171}
1172
1173bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
1174  ++stats::RelaxationSteps;
1175
1176  bool WasRelaxed = false;
1177  for (MCSection &Sec : *this) {
1178    while (layoutSectionOnce(Layout, Sec))
1179      WasRelaxed = true;
1180  }
1181
1182  return WasRelaxed;
1183}
1184
1185void MCAssembler::finishLayout(MCAsmLayout &Layout) {
1186  assert(getBackendPtr() && "Expected assembler backend");
1187  // The layout is done. Mark every fragment as valid.
1188  for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
1189    MCSection &Section = *Layout.getSectionOrder()[i];
1190    Layout.getFragmentOffset(&*Section.getFragmentList().rbegin());
1191    computeFragmentSize(Layout, *Section.getFragmentList().rbegin());
1192  }
1193  getBackend().finishLayout(*this, Layout);
1194}
1195
1196#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1197LLVM_DUMP_METHOD void MCAssembler::dump() const{
1198  raw_ostream &OS = errs();
1199
1200  OS << "<MCAssembler\n";
1201  OS << "  Sections:[\n    ";
1202  for (const_iterator it = begin(), ie = end(); it != ie; ++it) {
1203    if (it != begin()) OS << ",\n    ";
1204    it->dump();
1205  }
1206  OS << "],\n";
1207  OS << "  Symbols:[";
1208
1209  for (const_symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1210    if (it != symbol_begin()) OS << ",\n           ";
1211    OS << "(";
1212    it->dump();
1213    OS << ", Index:" << it->getIndex() << ", ";
1214    OS << ")";
1215  }
1216  OS << "]>\n";
1217}
1218#endif
1219