MCAssembler.cpp revision 360784 
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/ErrorHandling.h"
37#include "llvm/Support/LEB128.h"
38#include "llvm/Support/MathExtras.h"
39#include "llvm/Support/raw_ostream.h"
40#include <cassert>
41#include <cstdint>
42#include <cstring>
43#include <tuple>
44#include <utility>
45
46using namespace llvm;
47
48#define DEBUG_TYPE "assembler"
49
50namespace {
51namespace stats {
52
53STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total");
54STATISTIC(EmittedRelaxableFragments,
55          "Number of emitted assembler fragments - relaxable");
56STATISTIC(EmittedDataFragments,
57          "Number of emitted assembler fragments - data");
58STATISTIC(EmittedCompactEncodedInstFragments,
59          "Number of emitted assembler fragments - compact encoded inst");
60STATISTIC(EmittedAlignFragments,
61          "Number of emitted assembler fragments - align");
62STATISTIC(EmittedFillFragments,
63          "Number of emitted assembler fragments - fill");
64STATISTIC(EmittedOrgFragments,
65          "Number of emitted assembler fragments - org");
66STATISTIC(evaluateFixup, "Number of evaluated fixups");
67STATISTIC(FragmentLayouts, "Number of fragment layouts");
68STATISTIC(ObjectBytes, "Number of emitted object file bytes");
69STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
70STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
71
72} // end namespace stats
73} // end anonymous namespace
74
75// FIXME FIXME FIXME: There are number of places in this file where we convert
76// what is a 64-bit assembler value used for computation into a value in the
77// object file, which may truncate it. We should detect that truncation where
78// invalid and report errors back.
79
80/* *** */
81
82MCAssembler::MCAssembler(MCContext &Context,
83                         std::unique_ptr<MCAsmBackend> Backend,
84                         std::unique_ptr<MCCodeEmitter> Emitter,
85                         std::unique_ptr<MCObjectWriter> Writer)
86    : Context(Context), Backend(std::move(Backend)),
87      Emitter(std::move(Emitter)), Writer(std::move(Writer)),
88      BundleAlignSize(0), RelaxAll(false), SubsectionsViaSymbols(false),
89      IncrementalLinkerCompatible(false), ELFHeaderEFlags(0) {
90  VersionInfo.Major = 0; // Major version == 0 for "none specified"
91}
92
93MCAssembler::~MCAssembler() = default;
94
95void MCAssembler::reset() {
96  Sections.clear();
97  Symbols.clear();
98  IndirectSymbols.clear();
99  DataRegions.clear();
100  LinkerOptions.clear();
101  FileNames.clear();
102  ThumbFuncs.clear();
103  BundleAlignSize = 0;
104  RelaxAll = false;
105  SubsectionsViaSymbols = false;
106  IncrementalLinkerCompatible = false;
107  ELFHeaderEFlags = 0;
108  LOHContainer.reset();
109  VersionInfo.Major = 0;
110  VersionInfo.SDKVersion = VersionTuple();
111
112  // reset objects owned by us
113  if (getBackendPtr())
114    getBackendPtr()->reset();
115  if (getEmitterPtr())
116    getEmitterPtr()->reset();
117  if (getWriterPtr())
118    getWriterPtr()->reset();
119  getLOHContainer().reset();
120}
121
122bool MCAssembler::registerSection(MCSection &Section) {
123  if (Section.isRegistered())
124    return false;
125  Sections.push_back(&Section);
126  Section.setIsRegistered(true);
127  return true;
128}
129
130bool MCAssembler::isThumbFunc(const MCSymbol *Symbol) const {
131  if (ThumbFuncs.count(Symbol))
132    return true;
133
134  if (!Symbol->isVariable())
135    return false;
136
137  const MCExpr *Expr = Symbol->getVariableValue();
138
139  MCValue V;
140  if (!Expr->evaluateAsRelocatable(V, nullptr, nullptr))
141    return false;
142
143  if (V.getSymB() || V.getRefKind() != MCSymbolRefExpr::VK_None)
144    return false;
145
146  const MCSymbolRefExpr *Ref = V.getSymA();
147  if (!Ref)
148    return false;
149
150  if (Ref->getKind() != MCSymbolRefExpr::VK_None)
151    return false;
152
153  const MCSymbol &Sym = Ref->getSymbol();
154  if (!isThumbFunc(&Sym))
155    return false;
156
157  ThumbFuncs.insert(Symbol); // Cache it.
158  return true;
159}
160
161bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
162  // Non-temporary labels should always be visible to the linker.
163  if (!Symbol.isTemporary())
164    return true;
165
166  if (Symbol.isUsedInReloc())
167    return true;
168
169  return false;
170}
171
172const MCSymbol *MCAssembler::getAtom(const MCSymbol &S) const {
173  // Linker visible symbols define atoms.
174  if (isSymbolLinkerVisible(S))
175    return &S;
176
177  // Absolute and undefined symbols have no defining atom.
178  if (!S.isInSection())
179    return nullptr;
180
181  // Non-linker visible symbols in sections which can't be atomized have no
182  // defining atom.
183  if (!getContext().getAsmInfo()->isSectionAtomizableBySymbols(
184          *S.getFragment()->getParent()))
185    return nullptr;
186
187  // Otherwise, return the atom for the containing fragment.
188  return S.getFragment()->getAtom();
189}
190
191bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
192                                const MCFixup &Fixup, const MCFragment *DF,
193                                MCValue &Target, uint64_t &Value,
194                                bool &WasForced) const {
195  ++stats::evaluateFixup;
196
197  // FIXME: This code has some duplication with recordRelocation. We should
198  // probably merge the two into a single callback that tries to evaluate a
199  // fixup and records a relocation if one is needed.
200
201  // On error claim to have completely evaluated the fixup, to prevent any
202  // further processing from being done.
203  const MCExpr *Expr = Fixup.getValue();
204  MCContext &Ctx = getContext();
205  Value = 0;
206  WasForced = false;
207  if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup)) {
208    Ctx.reportError(Fixup.getLoc(), "expected relocatable expression");
209    return true;
210  }
211  if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
212    if (RefB->getKind() != MCSymbolRefExpr::VK_None) {
213      Ctx.reportError(Fixup.getLoc(),
214                      "unsupported subtraction of qualified symbol");
215      return true;
216    }
217  }
218
219  assert(getBackendPtr() && "Expected assembler backend");
220  bool IsTarget = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags &
221                  MCFixupKindInfo::FKF_IsTarget;
222
223  if (IsTarget)
224    return getBackend().evaluateTargetFixup(*this, Layout, Fixup, DF, Target,
225                                            Value, WasForced);
226
227  unsigned FixupFlags = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags;
228  bool IsPCRel = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags &
229                 MCFixupKindInfo::FKF_IsPCRel;
230
231  bool IsResolved = false;
232  if (IsPCRel) {
233    if (Target.getSymB()) {
234      IsResolved = false;
235    } else if (!Target.getSymA()) {
236      IsResolved = false;
237    } else {
238      const MCSymbolRefExpr *A = Target.getSymA();
239      const MCSymbol &SA = A->getSymbol();
240      if (A->getKind() != MCSymbolRefExpr::VK_None || SA.isUndefined()) {
241        IsResolved = false;
242      } else if (auto *Writer = getWriterPtr()) {
243        IsResolved = (FixupFlags & MCFixupKindInfo::FKF_Constant) ||
244                     Writer->isSymbolRefDifferenceFullyResolvedImpl(
245                         *this, SA, *DF, false, true);
246      }
247    }
248  } else {
249    IsResolved = Target.isAbsolute();
250  }
251
252  Value = Target.getConstant();
253
254  if (const MCSymbolRefExpr *A = Target.getSymA()) {
255    const MCSymbol &Sym = A->getSymbol();
256    if (Sym.isDefined())
257      Value += Layout.getSymbolOffset(Sym);
258  }
259  if (const MCSymbolRefExpr *B = Target.getSymB()) {
260    const MCSymbol &Sym = B->getSymbol();
261    if (Sym.isDefined())
262      Value -= Layout.getSymbolOffset(Sym);
263  }
264
265  bool ShouldAlignPC = getBackend().getFixupKindInfo(Fixup.getKind()).Flags &
266                       MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
267  assert((ShouldAlignPC ? IsPCRel : true) &&
268    "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");
269
270  if (IsPCRel) {
271    uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();
272
273    // A number of ARM fixups in Thumb mode require that the effective PC
274    // address be determined as the 32-bit aligned version of the actual offset.
275    if (ShouldAlignPC) Offset &= ~0x3;
276    Value -= Offset;
277  }
278
279  // Let the backend force a relocation if needed.
280  if (IsResolved && getBackend().shouldForceRelocation(*this, Fixup, Target)) {
281    IsResolved = false;
282    WasForced = true;
283  }
284
285  return IsResolved;
286}
287
288uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
289                                          const MCFragment &F) const {
290  assert(getBackendPtr() && "Requires assembler backend");
291  switch (F.getKind()) {
292  case MCFragment::FT_Data:
293    return cast<MCDataFragment>(F).getContents().size();
294  case MCFragment::FT_Relaxable:
295    return cast<MCRelaxableFragment>(F).getContents().size();
296  case MCFragment::FT_CompactEncodedInst:
297    return cast<MCCompactEncodedInstFragment>(F).getContents().size();
298  case MCFragment::FT_Fill: {
299    auto &FF = cast<MCFillFragment>(F);
300    int64_t NumValues = 0;
301    if (!FF.getNumValues().evaluateAsAbsolute(NumValues, Layout)) {
302      getContext().reportError(FF.getLoc(),
303                               "expected assembly-time absolute expression");
304      return 0;
305    }
306    int64_t Size = NumValues * FF.getValueSize();
307    if (Size < 0) {
308      getContext().reportError(FF.getLoc(), "invalid number of bytes");
309      return 0;
310    }
311    return Size;
312  }
313
314  case MCFragment::FT_LEB:
315    return cast<MCLEBFragment>(F).getContents().size();
316
317  case MCFragment::FT_BoundaryAlign:
318    return cast<MCBoundaryAlignFragment>(F).getSize();
319
320  case MCFragment::FT_SymbolId:
321    return 4;
322
323  case MCFragment::FT_Align: {
324    const MCAlignFragment &AF = cast<MCAlignFragment>(F);
325    unsigned Offset = Layout.getFragmentOffset(&AF);
326    unsigned Size = offsetToAlignment(Offset, Align(AF.getAlignment()));
327
328    // Insert extra Nops for code alignment if the target define
329    // shouldInsertExtraNopBytesForCodeAlign target hook.
330    if (AF.getParent()->UseCodeAlign() && AF.hasEmitNops() &&
331        getBackend().shouldInsertExtraNopBytesForCodeAlign(AF, Size))
332      return Size;
333
334    // If we are padding with nops, force the padding to be larger than the
335    // minimum nop size.
336    if (Size > 0 && AF.hasEmitNops()) {
337      while (Size % getBackend().getMinimumNopSize())
338        Size += AF.getAlignment();
339    }
340    if (Size > AF.getMaxBytesToEmit())
341      return 0;
342    return Size;
343  }
344
345  case MCFragment::FT_Org: {
346    const MCOrgFragment &OF = cast<MCOrgFragment>(F);
347    MCValue Value;
348    if (!OF.getOffset().evaluateAsValue(Value, Layout)) {
349      getContext().reportError(OF.getLoc(),
350                               "expected assembly-time absolute expression");
351        return 0;
352    }
353
354    uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
355    int64_t TargetLocation = Value.getConstant();
356    if (const MCSymbolRefExpr *A = Value.getSymA()) {
357      uint64_t Val;
358      if (!Layout.getSymbolOffset(A->getSymbol(), Val)) {
359        getContext().reportError(OF.getLoc(), "expected absolute expression");
360        return 0;
361      }
362      TargetLocation += Val;
363    }
364    int64_t Size = TargetLocation - FragmentOffset;
365    if (Size < 0 || Size >= 0x40000000) {
366      getContext().reportError(
367          OF.getLoc(), "invalid .org offset '" + Twine(TargetLocation) +
368                           "' (at offset '" + Twine(FragmentOffset) + "')");
369      return 0;
370    }
371    return Size;
372  }
373
374  case MCFragment::FT_Dwarf:
375    return cast<MCDwarfLineAddrFragment>(F).getContents().size();
376  case MCFragment::FT_DwarfFrame:
377    return cast<MCDwarfCallFrameFragment>(F).getContents().size();
378  case MCFragment::FT_CVInlineLines:
379    return cast<MCCVInlineLineTableFragment>(F).getContents().size();
380  case MCFragment::FT_CVDefRange:
381    return cast<MCCVDefRangeFragment>(F).getContents().size();
382  case MCFragment::FT_Dummy:
383    llvm_unreachable("Should not have been added");
384  }
385
386  llvm_unreachable("invalid fragment kind");
387}
388
389void MCAsmLayout::layoutFragment(MCFragment *F) {
390  MCFragment *Prev = F->getPrevNode();
391
392  // We should never try to recompute something which is valid.
393  assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
394  // We should never try to compute the fragment layout if its predecessor
395  // isn't valid.
396  assert((!Prev || isFragmentValid(Prev)) &&
397         "Attempt to compute fragment before its predecessor!");
398
399  ++stats::FragmentLayouts;
400
401  // Compute fragment offset and size.
402  if (Prev)
403    F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
404  else
405    F->Offset = 0;
406  LastValidFragment[F->getParent()] = F;
407
408  // If bundling is enabled and this fragment has instructions in it, it has to
409  // obey the bundling restrictions. With padding, we'll have:
410  //
411  //
412  //        BundlePadding
413  //             |||
414  // -------------------------------------
415  //   Prev  |##########|       F        |
416  // -------------------------------------
417  //                    ^
418  //                    |
419  //                    F->Offset
420  //
421  // The fragment's offset will point to after the padding, and its computed
422  // size won't include the padding.
423  //
424  // When the -mc-relax-all flag is used, we optimize bundling by writting the
425  // padding directly into fragments when the instructions are emitted inside
426  // the streamer. When the fragment is larger than the bundle size, we need to
427  // ensure that it's bundle aligned. This means that if we end up with
428  // multiple fragments, we must emit bundle padding between fragments.
429  //
430  // ".align N" is an example of a directive that introduces multiple
431  // fragments. We could add a special case to handle ".align N" by emitting
432  // within-fragment padding (which would produce less padding when N is less
433  // than the bundle size), but for now we don't.
434  //
435  if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
436    assert(isa<MCEncodedFragment>(F) &&
437           "Only MCEncodedFragment implementations have instructions");
438    MCEncodedFragment *EF = cast<MCEncodedFragment>(F);
439    uint64_t FSize = Assembler.computeFragmentSize(*this, *EF);
440
441    if (!Assembler.getRelaxAll() && FSize > Assembler.getBundleAlignSize())
442      report_fatal_error("Fragment can't be larger than a bundle size");
443
444    uint64_t RequiredBundlePadding =
445        computeBundlePadding(Assembler, EF, EF->Offset, FSize);
446    if (RequiredBundlePadding > UINT8_MAX)
447      report_fatal_error("Padding cannot exceed 255 bytes");
448    EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
449    EF->Offset += RequiredBundlePadding;
450  }
451}
452
453void MCAssembler::registerSymbol(const MCSymbol &Symbol, bool *Created) {
454  bool New = !Symbol.isRegistered();
455  if (Created)
456    *Created = New;
457  if (New) {
458    Symbol.setIsRegistered(true);
459    Symbols.push_back(&Symbol);
460  }
461}
462
463void MCAssembler::writeFragmentPadding(raw_ostream &OS,
464                                       const MCEncodedFragment &EF,
465                                       uint64_t FSize) const {
466  assert(getBackendPtr() && "Expected assembler backend");
467  // Should NOP padding be written out before this fragment?
468  unsigned BundlePadding = EF.getBundlePadding();
469  if (BundlePadding > 0) {
470    assert(isBundlingEnabled() &&
471           "Writing bundle padding with disabled bundling");
472    assert(EF.hasInstructions() &&
473           "Writing bundle padding for a fragment without instructions");
474
475    unsigned TotalLength = BundlePadding + static_cast<unsigned>(FSize);
476    if (EF.alignToBundleEnd() && TotalLength > getBundleAlignSize()) {
477      // If the padding itself crosses a bundle boundary, it must be emitted
478      // in 2 pieces, since even nop instructions must not cross boundaries.
479      //             v--------------v   <- BundleAlignSize
480      //        v---------v             <- BundlePadding
481      // ----------------------------
482      // | Prev |####|####|    F    |
483      // ----------------------------
484      //        ^-------------------^   <- TotalLength
485      unsigned DistanceToBoundary = TotalLength - getBundleAlignSize();
486      if (!getBackend().writeNopData(OS, DistanceToBoundary))
487        report_fatal_error("unable to write NOP sequence of " +
488                           Twine(DistanceToBoundary) + " bytes");
489      BundlePadding -= DistanceToBoundary;
490    }
491    if (!getBackend().writeNopData(OS, BundlePadding))
492      report_fatal_error("unable to write NOP sequence of " +
493                         Twine(BundlePadding) + " bytes");
494  }
495}
496
497/// Write the fragment \p F to the output file.
498static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
499                          const MCAsmLayout &Layout, const MCFragment &F) {
500  // FIXME: Embed in fragments instead?
501  uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
502
503  support::endianness Endian = Asm.getBackend().Endian;
504
505  if (const MCEncodedFragment *EF = dyn_cast<MCEncodedFragment>(&F))
506    Asm.writeFragmentPadding(OS, *EF, FragmentSize);
507
508  // This variable (and its dummy usage) is to participate in the assert at
509  // the end of the function.
510  uint64_t Start = OS.tell();
511  (void) Start;
512
513  ++stats::EmittedFragments;
514
515  switch (F.getKind()) {
516  case MCFragment::FT_Align: {
517    ++stats::EmittedAlignFragments;
518    const MCAlignFragment &AF = cast<MCAlignFragment>(F);
519    assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
520
521    uint64_t Count = FragmentSize / AF.getValueSize();
522
523    // FIXME: This error shouldn't actually occur (the front end should emit
524    // multiple .align directives to enforce the semantics it wants), but is
525    // severe enough that we want to report it. How to handle this?
526    if (Count * AF.getValueSize() != FragmentSize)
527      report_fatal_error("undefined .align directive, value size '" +
528                        Twine(AF.getValueSize()) +
529                        "' is not a divisor of padding size '" +
530                        Twine(FragmentSize) + "'");
531
532    // See if we are aligning with nops, and if so do that first to try to fill
533    // the Count bytes.  Then if that did not fill any bytes or there are any
534    // bytes left to fill use the Value and ValueSize to fill the rest.
535    // If we are aligning with nops, ask that target to emit the right data.
536    if (AF.hasEmitNops()) {
537      if (!Asm.getBackend().writeNopData(OS, Count))
538        report_fatal_error("unable to write nop sequence of " +
539                          Twine(Count) + " bytes");
540      break;
541    }
542
543    // Otherwise, write out in multiples of the value size.
544    for (uint64_t i = 0; i != Count; ++i) {
545      switch (AF.getValueSize()) {
546      default: llvm_unreachable("Invalid size!");
547      case 1: OS << char(AF.getValue()); break;
548      case 2:
549        support::endian::write<uint16_t>(OS, AF.getValue(), Endian);
550        break;
551      case 4:
552        support::endian::write<uint32_t>(OS, AF.getValue(), Endian);
553        break;
554      case 8:
555        support::endian::write<uint64_t>(OS, AF.getValue(), Endian);
556        break;
557      }
558    }
559    break;
560  }
561
562  case MCFragment::FT_Data:
563    ++stats::EmittedDataFragments;
564    OS << cast<MCDataFragment>(F).getContents();
565    break;
566
567  case MCFragment::FT_Relaxable:
568    ++stats::EmittedRelaxableFragments;
569    OS << cast<MCRelaxableFragment>(F).getContents();
570    break;
571
572  case MCFragment::FT_CompactEncodedInst:
573    ++stats::EmittedCompactEncodedInstFragments;
574    OS << cast<MCCompactEncodedInstFragment>(F).getContents();
575    break;
576
577  case MCFragment::FT_Fill: {
578    ++stats::EmittedFillFragments;
579    const MCFillFragment &FF = cast<MCFillFragment>(F);
580    uint64_t V = FF.getValue();
581    unsigned VSize = FF.getValueSize();
582    const unsigned MaxChunkSize = 16;
583    char Data[MaxChunkSize];
584    assert(0 < VSize && VSize <= MaxChunkSize && "Illegal fragment fill size");
585    // Duplicate V into Data as byte vector to reduce number of
586    // writes done. As such, do endian conversion here.
587    for (unsigned I = 0; I != VSize; ++I) {
588      unsigned index = Endian == support::little ? I : (VSize - I - 1);
589      Data[I] = uint8_t(V >> (index * 8));
590    }
591    for (unsigned I = VSize; I < MaxChunkSize; ++I)
592      Data[I] = Data[I - VSize];
593
594    // Set to largest multiple of VSize in Data.
595    const unsigned NumPerChunk = MaxChunkSize / VSize;
596    // Set ChunkSize to largest multiple of VSize in Data
597    const unsigned ChunkSize = VSize * NumPerChunk;
598
599    // Do copies by chunk.
600    StringRef Ref(Data, ChunkSize);
601    for (uint64_t I = 0, E = FragmentSize / ChunkSize; I != E; ++I)
602      OS << Ref;
603
604    // do remainder if needed.
605    unsigned TrailingCount = FragmentSize % ChunkSize;
606    if (TrailingCount)
607      OS.write(Data, TrailingCount);
608    break;
609  }
610
611  case MCFragment::FT_LEB: {
612    const MCLEBFragment &LF = cast<MCLEBFragment>(F);
613    OS << LF.getContents();
614    break;
615  }
616
617  case MCFragment::FT_BoundaryAlign: {
618    if (!Asm.getBackend().writeNopData(OS, FragmentSize))
619      report_fatal_error("unable to write nop sequence of " +
620                         Twine(FragmentSize) + " bytes");
621    break;
622  }
623
624  case MCFragment::FT_SymbolId: {
625    const MCSymbolIdFragment &SF = cast<MCSymbolIdFragment>(F);
626    support::endian::write<uint32_t>(OS, SF.getSymbol()->getIndex(), Endian);
627    break;
628  }
629
630  case MCFragment::FT_Org: {
631    ++stats::EmittedOrgFragments;
632    const MCOrgFragment &OF = cast<MCOrgFragment>(F);
633
634    for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
635      OS << char(OF.getValue());
636
637    break;
638  }
639
640  case MCFragment::FT_Dwarf: {
641    const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
642    OS << OF.getContents();
643    break;
644  }
645  case MCFragment::FT_DwarfFrame: {
646    const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
647    OS << CF.getContents();
648    break;
649  }
650  case MCFragment::FT_CVInlineLines: {
651    const auto &OF = cast<MCCVInlineLineTableFragment>(F);
652    OS << OF.getContents();
653    break;
654  }
655  case MCFragment::FT_CVDefRange: {
656    const auto &DRF = cast<MCCVDefRangeFragment>(F);
657    OS << DRF.getContents();
658    break;
659  }
660  case MCFragment::FT_Dummy:
661    llvm_unreachable("Should not have been added");
662  }
663
664  assert(OS.tell() - Start == FragmentSize &&
665         "The stream should advance by fragment size");
666}
667
668void MCAssembler::writeSectionData(raw_ostream &OS, const MCSection *Sec,
669                                   const MCAsmLayout &Layout) const {
670  assert(getBackendPtr() && "Expected assembler backend");
671
672  // Ignore virtual sections.
673  if (Sec->isVirtualSection()) {
674    assert(Layout.getSectionFileSize(Sec) == 0 && "Invalid size for section!");
675
676    // Check that contents are only things legal inside a virtual section.
677    for (const MCFragment &F : *Sec) {
678      switch (F.getKind()) {
679      default: llvm_unreachable("Invalid fragment in virtual section!");
680      case MCFragment::FT_Data: {
681        // Check that we aren't trying to write a non-zero contents (or fixups)
682        // into a virtual section. This is to support clients which use standard
683        // directives to fill the contents of virtual sections.
684        const MCDataFragment &DF = cast<MCDataFragment>(F);
685        if (DF.fixup_begin() != DF.fixup_end())
686          report_fatal_error("cannot have fixups in virtual section!");
687        for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
688          if (DF.getContents()[i]) {
689            if (auto *ELFSec = dyn_cast<const MCSectionELF>(Sec))
690              report_fatal_error("non-zero initializer found in section '" +
691                  ELFSec->getSectionName() + "'");
692            else
693              report_fatal_error("non-zero initializer found in virtual section");
694          }
695        break;
696      }
697      case MCFragment::FT_Align:
698        // Check that we aren't trying to write a non-zero value into a virtual
699        // section.
700        assert((cast<MCAlignFragment>(F).getValueSize() == 0 ||
701                cast<MCAlignFragment>(F).getValue() == 0) &&
702               "Invalid align in virtual section!");
703        break;
704      case MCFragment::FT_Fill:
705        assert((cast<MCFillFragment>(F).getValue() == 0) &&
706               "Invalid fill in virtual section!");
707        break;
708      }
709    }
710
711    return;
712  }
713
714  uint64_t Start = OS.tell();
715  (void)Start;
716
717  for (const MCFragment &F : *Sec)
718    writeFragment(OS, *this, Layout, F);
719
720  assert(OS.tell() - Start == Layout.getSectionAddressSize(Sec));
721}
722
723std::tuple<MCValue, uint64_t, bool>
724MCAssembler::handleFixup(const MCAsmLayout &Layout, MCFragment &F,
725                         const MCFixup &Fixup) {
726  // Evaluate the fixup.
727  MCValue Target;
728  uint64_t FixedValue;
729  bool WasForced;
730  bool IsResolved = evaluateFixup(Layout, Fixup, &F, Target, FixedValue,
731                                  WasForced);
732  if (!IsResolved) {
733    // The fixup was unresolved, we need a relocation. Inform the object
734    // writer of the relocation, and give it an opportunity to adjust the
735    // fixup value if need be.
736    if (Target.getSymA() && Target.getSymB() &&
737        getBackend().requiresDiffExpressionRelocations()) {
738      // The fixup represents the difference between two symbols, which the
739      // backend has indicated must be resolved at link time. Split up the fixup
740      // into two relocations, one for the add, and one for the sub, and emit
741      // both of these. The constant will be associated with the add half of the
742      // expression.
743      MCFixup FixupAdd = MCFixup::createAddFor(Fixup);
744      MCValue TargetAdd =
745          MCValue::get(Target.getSymA(), nullptr, Target.getConstant());
746      getWriter().recordRelocation(*this, Layout, &F, FixupAdd, TargetAdd,
747                                   FixedValue);
748      MCFixup FixupSub = MCFixup::createSubFor(Fixup);
749      MCValue TargetSub = MCValue::get(Target.getSymB());
750      getWriter().recordRelocation(*this, Layout, &F, FixupSub, TargetSub,
751                                   FixedValue);
752    } else {
753      getWriter().recordRelocation(*this, Layout, &F, Fixup, Target,
754                                   FixedValue);
755    }
756  }
757  return std::make_tuple(Target, FixedValue, IsResolved);
758}
759
760void MCAssembler::layout(MCAsmLayout &Layout) {
761  assert(getBackendPtr() && "Expected assembler backend");
762  DEBUG_WITH_TYPE("mc-dump", {
763      errs() << "assembler backend - pre-layout\n--\n";
764      dump(); });
765
766  // Create dummy fragments and assign section ordinals.
767  unsigned SectionIndex = 0;
768  for (MCSection &Sec : *this) {
769    // Create dummy fragments to eliminate any empty sections, this simplifies
770    // layout.
771    if (Sec.getFragmentList().empty())
772      new MCDataFragment(&Sec);
773
774    Sec.setOrdinal(SectionIndex++);
775  }
776
777  // Assign layout order indices to sections and fragments.
778  for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
779    MCSection *Sec = Layout.getSectionOrder()[i];
780    Sec->setLayoutOrder(i);
781
782    unsigned FragmentIndex = 0;
783    for (MCFragment &Frag : *Sec)
784      Frag.setLayoutOrder(FragmentIndex++);
785  }
786
787  // Layout until everything fits.
788  while (layoutOnce(Layout))
789    if (getContext().hadError())
790      return;
791
792  DEBUG_WITH_TYPE("mc-dump", {
793      errs() << "assembler backend - post-relaxation\n--\n";
794      dump(); });
795
796  // Finalize the layout, including fragment lowering.
797  finishLayout(Layout);
798
799  DEBUG_WITH_TYPE("mc-dump", {
800      errs() << "assembler backend - final-layout\n--\n";
801      dump(); });
802
803  // Allow the object writer a chance to perform post-layout binding (for
804  // example, to set the index fields in the symbol data).
805  getWriter().executePostLayoutBinding(*this, Layout);
806
807  // Evaluate and apply the fixups, generating relocation entries as necessary.
808  for (MCSection &Sec : *this) {
809    for (MCFragment &Frag : Sec) {
810      // Data and relaxable fragments both have fixups.  So only process
811      // those here.
812      // FIXME: Is there a better way to do this?  MCEncodedFragmentWithFixups
813      // being templated makes this tricky.
814      if (isa<MCEncodedFragment>(&Frag) &&
815          isa<MCCompactEncodedInstFragment>(&Frag))
816        continue;
817      if (!isa<MCEncodedFragment>(&Frag) && !isa<MCCVDefRangeFragment>(&Frag) &&
818          !isa<MCAlignFragment>(&Frag))
819        continue;
820      ArrayRef<MCFixup> Fixups;
821      MutableArrayRef<char> Contents;
822      const MCSubtargetInfo *STI = nullptr;
823      if (auto *FragWithFixups = dyn_cast<MCDataFragment>(&Frag)) {
824        Fixups = FragWithFixups->getFixups();
825        Contents = FragWithFixups->getContents();
826        STI = FragWithFixups->getSubtargetInfo();
827        assert(!FragWithFixups->hasInstructions() || STI != nullptr);
828      } else if (auto *FragWithFixups = dyn_cast<MCRelaxableFragment>(&Frag)) {
829        Fixups = FragWithFixups->getFixups();
830        Contents = FragWithFixups->getContents();
831        STI = FragWithFixups->getSubtargetInfo();
832        assert(!FragWithFixups->hasInstructions() || STI != nullptr);
833      } else if (auto *FragWithFixups = dyn_cast<MCCVDefRangeFragment>(&Frag)) {
834        Fixups = FragWithFixups->getFixups();
835        Contents = FragWithFixups->getContents();
836      } else if (auto *FragWithFixups = dyn_cast<MCDwarfLineAddrFragment>(&Frag)) {
837        Fixups = FragWithFixups->getFixups();
838        Contents = FragWithFixups->getContents();
839      } else if (auto *AF = dyn_cast<MCAlignFragment>(&Frag)) {
840        // Insert fixup type for code alignment if the target define
841        // shouldInsertFixupForCodeAlign target hook.
842        if (Sec.UseCodeAlign() && AF->hasEmitNops()) {
843          getBackend().shouldInsertFixupForCodeAlign(*this, Layout, *AF);
844        }
845        continue;
846      } else if (auto *FragWithFixups =
847                     dyn_cast<MCDwarfCallFrameFragment>(&Frag)) {
848        Fixups = FragWithFixups->getFixups();
849        Contents = FragWithFixups->getContents();
850      } else
851        llvm_unreachable("Unknown fragment with fixups!");
852      for (const MCFixup &Fixup : Fixups) {
853        uint64_t FixedValue;
854        bool IsResolved;
855        MCValue Target;
856        std::tie(Target, FixedValue, IsResolved) =
857            handleFixup(Layout, Frag, Fixup);
858        getBackend().applyFixup(*this, Fixup, Target, Contents, FixedValue,
859                                IsResolved, STI);
860      }
861    }
862  }
863}
864
865void MCAssembler::Finish() {
866  // Create the layout object.
867  MCAsmLayout Layout(*this);
868  layout(Layout);
869
870  // Write the object file.
871  stats::ObjectBytes += getWriter().writeObject(*this, Layout);
872}
873
874bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
875                                       const MCRelaxableFragment *DF,
876                                       const MCAsmLayout &Layout) const {
877  assert(getBackendPtr() && "Expected assembler backend");
878  MCValue Target;
879  uint64_t Value;
880  bool WasForced;
881  bool Resolved = evaluateFixup(Layout, Fixup, DF, Target, Value, WasForced);
882  if (Target.getSymA() &&
883      Target.getSymA()->getKind() == MCSymbolRefExpr::VK_X86_ABS8 &&
884      Fixup.getKind() == FK_Data_1)
885    return false;
886  return getBackend().fixupNeedsRelaxationAdvanced(Fixup, Resolved, Value, DF,
887                                                   Layout, WasForced);
888}
889
890bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
891                                          const MCAsmLayout &Layout) const {
892  assert(getBackendPtr() && "Expected assembler backend");
893  // If this inst doesn't ever need relaxation, ignore it. This occurs when we
894  // are intentionally pushing out inst fragments, or because we relaxed a
895  // previous instruction to one that doesn't need relaxation.
896  if (!getBackend().mayNeedRelaxation(F->getInst(), *F->getSubtargetInfo()))
897    return false;
898
899  for (const MCFixup &Fixup : F->getFixups())
900    if (fixupNeedsRelaxation(Fixup, F, Layout))
901      return true;
902
903  return false;
904}
905
906bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
907                                   MCRelaxableFragment &F) {
908  assert(getEmitterPtr() &&
909         "Expected CodeEmitter defined for relaxInstruction");
910  if (!fragmentNeedsRelaxation(&F, Layout))
911    return false;
912
913  ++stats::RelaxedInstructions;
914
915  // FIXME-PERF: We could immediately lower out instructions if we can tell
916  // they are fully resolved, to avoid retesting on later passes.
917
918  // Relax the fragment.
919
920  MCInst Relaxed;
921  getBackend().relaxInstruction(F.getInst(), *F.getSubtargetInfo(), Relaxed);
922
923  // Encode the new instruction.
924  //
925  // FIXME-PERF: If it matters, we could let the target do this. It can
926  // probably do so more efficiently in many cases.
927  SmallVector<MCFixup, 4> Fixups;
928  SmallString<256> Code;
929  raw_svector_ostream VecOS(Code);
930  getEmitter().encodeInstruction(Relaxed, VecOS, Fixups, *F.getSubtargetInfo());
931
932  // Update the fragment.
933  F.setInst(Relaxed);
934  F.getContents() = Code;
935  F.getFixups() = Fixups;
936
937  return true;
938}
939
940bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
941  uint64_t OldSize = LF.getContents().size();
942  int64_t Value;
943  bool Abs = LF.getValue().evaluateKnownAbsolute(Value, Layout);
944  if (!Abs)
945    report_fatal_error("sleb128 and uleb128 expressions must be absolute");
946  SmallString<8> &Data = LF.getContents();
947  Data.clear();
948  raw_svector_ostream OSE(Data);
949  // The compiler can generate EH table assembly that is impossible to assemble
950  // without either adding padding to an LEB fragment or adding extra padding
951  // to a later alignment fragment. To accommodate such tables, relaxation can
952  // only increase an LEB fragment size here, not decrease it. See PR35809.
953  if (LF.isSigned())
954    encodeSLEB128(Value, OSE, OldSize);
955  else
956    encodeULEB128(Value, OSE, OldSize);
957  return OldSize != LF.getContents().size();
958}
959
960/// Check if the branch crosses the boundary.
961///
962/// \param StartAddr start address of the fused/unfused branch.
963/// \param Size size of the fused/unfused branch.
964/// \param BoundaryAlignment alignment requirement of the branch.
965/// \returns true if the branch cross the boundary.
966static bool mayCrossBoundary(uint64_t StartAddr, uint64_t Size,
967                             Align BoundaryAlignment) {
968  uint64_t EndAddr = StartAddr + Size;
969  return (StartAddr >> Log2(BoundaryAlignment)) !=
970         ((EndAddr - 1) >> Log2(BoundaryAlignment));
971}
972
973/// Check if the branch is against the boundary.
974///
975/// \param StartAddr start address of the fused/unfused branch.
976/// \param Size size of the fused/unfused branch.
977/// \param BoundaryAlignment alignment requirement of the branch.
978/// \returns true if the branch is against the boundary.
979static bool isAgainstBoundary(uint64_t StartAddr, uint64_t Size,
980                              Align BoundaryAlignment) {
981  uint64_t EndAddr = StartAddr + Size;
982  return (EndAddr & (BoundaryAlignment.value() - 1)) == 0;
983}
984
985/// Check if the branch needs padding.
986///
987/// \param StartAddr start address of the fused/unfused branch.
988/// \param Size size of the fused/unfused branch.
989/// \param BoundaryAlignment alignment requirement of the branch.
990/// \returns true if the branch needs padding.
991static bool needPadding(uint64_t StartAddr, uint64_t Size,
992                        Align BoundaryAlignment) {
993  return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) ||
994         isAgainstBoundary(StartAddr, Size, BoundaryAlignment);
995}
996
997bool MCAssembler::relaxBoundaryAlign(MCAsmLayout &Layout,
998                                     MCBoundaryAlignFragment &BF) {
999  // The MCBoundaryAlignFragment that doesn't emit NOP should not be relaxed.
1000  if (!BF.canEmitNops())
1001    return false;
1002
1003  uint64_t AlignedOffset = Layout.getFragmentOffset(BF.getNextNode());
1004  uint64_t AlignedSize = 0;
1005  const MCFragment *F = BF.getNextNode();
1006  // If the branch is unfused, it is emitted into one fragment, otherwise it is
1007  // emitted into two fragments at most, the next MCBoundaryAlignFragment(if
1008  // exists) also marks the end of the branch.
1009  for (auto i = 0, N = BF.isFused() ? 2 : 1;
1010       i != N && !isa<MCBoundaryAlignFragment>(F); ++i, F = F->getNextNode()) {
1011    AlignedSize += computeFragmentSize(Layout, *F);
1012  }
1013  uint64_t OldSize = BF.getSize();
1014  AlignedOffset -= OldSize;
1015  Align BoundaryAlignment = BF.getAlignment();
1016  uint64_t NewSize = needPadding(AlignedOffset, AlignedSize, BoundaryAlignment)
1017                         ? offsetToAlignment(AlignedOffset, BoundaryAlignment)
1018                         : 0U;
1019  if (NewSize == OldSize)
1020    return false;
1021  BF.setSize(NewSize);
1022  Layout.invalidateFragmentsFrom(&BF);
1023  return true;
1024}
1025
1026bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
1027                                     MCDwarfLineAddrFragment &DF) {
1028  MCContext &Context = Layout.getAssembler().getContext();
1029  uint64_t OldSize = DF.getContents().size();
1030  int64_t AddrDelta;
1031  bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1032  assert(Abs && "We created a line delta with an invalid expression");
1033  (void)Abs;
1034  int64_t LineDelta;
1035  LineDelta = DF.getLineDelta();
1036  SmallVectorImpl<char> &Data = DF.getContents();
1037  Data.clear();
1038  raw_svector_ostream OSE(Data);
1039  DF.getFixups().clear();
1040
1041  if (!getBackend().requiresDiffExpressionRelocations()) {
1042    MCDwarfLineAddr::Encode(Context, getDWARFLinetableParams(), LineDelta,
1043                            AddrDelta, OSE);
1044  } else {
1045    uint32_t Offset;
1046    uint32_t Size;
1047    bool SetDelta = MCDwarfLineAddr::FixedEncode(Context,
1048                                                 getDWARFLinetableParams(),
1049                                                 LineDelta, AddrDelta,
1050                                                 OSE, &Offset, &Size);
1051    // Add Fixups for address delta or new address.
1052    const MCExpr *FixupExpr;
1053    if (SetDelta) {
1054      FixupExpr = &DF.getAddrDelta();
1055    } else {
1056      const MCBinaryExpr *ABE = cast<MCBinaryExpr>(&DF.getAddrDelta());
1057      FixupExpr = ABE->getLHS();
1058    }
1059    DF.getFixups().push_back(
1060        MCFixup::create(Offset, FixupExpr,
1061                        MCFixup::getKindForSize(Size, false /*isPCRel*/)));
1062  }
1063
1064  return OldSize != Data.size();
1065}
1066
1067bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
1068                                              MCDwarfCallFrameFragment &DF) {
1069  MCContext &Context = Layout.getAssembler().getContext();
1070  uint64_t OldSize = DF.getContents().size();
1071  int64_t AddrDelta;
1072  bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
1073  assert(Abs && "We created call frame with an invalid expression");
1074  (void) Abs;
1075  SmallVectorImpl<char> &Data = DF.getContents();
1076  Data.clear();
1077  raw_svector_ostream OSE(Data);
1078  DF.getFixups().clear();
1079
1080  if (getBackend().requiresDiffExpressionRelocations()) {
1081    uint32_t Offset;
1082    uint32_t Size;
1083    MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE, &Offset,
1084                                          &Size);
1085    if (Size) {
1086      DF.getFixups().push_back(MCFixup::create(
1087          Offset, &DF.getAddrDelta(),
1088          MCFixup::getKindForSizeInBits(Size /*In bits.*/, false /*isPCRel*/)));
1089    }
1090  } else {
1091    MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE);
1092  }
1093
1094  return OldSize != Data.size();
1095}
1096
1097bool MCAssembler::relaxCVInlineLineTable(MCAsmLayout &Layout,
1098                                         MCCVInlineLineTableFragment &F) {
1099  unsigned OldSize = F.getContents().size();
1100  getContext().getCVContext().encodeInlineLineTable(Layout, F);
1101  return OldSize != F.getContents().size();
1102}
1103
1104bool MCAssembler::relaxCVDefRange(MCAsmLayout &Layout,
1105                                  MCCVDefRangeFragment &F) {
1106  unsigned OldSize = F.getContents().size();
1107  getContext().getCVContext().encodeDefRange(Layout, F);
1108  return OldSize != F.getContents().size();
1109}
1110
1111bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec) {
1112  // Holds the first fragment which needed relaxing during this layout. It will
1113  // remain NULL if none were relaxed.
1114  // When a fragment is relaxed, all the fragments following it should get
1115  // invalidated because their offset is going to change.
1116  MCFragment *FirstRelaxedFragment = nullptr;
1117
1118  // Attempt to relax all the fragments in the section.
1119  for (MCSection::iterator I = Sec.begin(), IE = Sec.end(); I != IE; ++I) {
1120    // Check if this is a fragment that needs relaxation.
1121    bool RelaxedFrag = false;
1122    switch(I->getKind()) {
1123    default:
1124      break;
1125    case MCFragment::FT_Relaxable:
1126      assert(!getRelaxAll() &&
1127             "Did not expect a MCRelaxableFragment in RelaxAll mode");
1128      RelaxedFrag = relaxInstruction(Layout, *cast<MCRelaxableFragment>(I));
1129      break;
1130    case MCFragment::FT_Dwarf:
1131      RelaxedFrag = relaxDwarfLineAddr(Layout,
1132                                       *cast<MCDwarfLineAddrFragment>(I));
1133      break;
1134    case MCFragment::FT_DwarfFrame:
1135      RelaxedFrag =
1136        relaxDwarfCallFrameFragment(Layout,
1137                                    *cast<MCDwarfCallFrameFragment>(I));
1138      break;
1139    case MCFragment::FT_LEB:
1140      RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
1141      break;
1142    case MCFragment::FT_BoundaryAlign:
1143      RelaxedFrag =
1144          relaxBoundaryAlign(Layout, *cast<MCBoundaryAlignFragment>(I));
1145      break;
1146    case MCFragment::FT_CVInlineLines:
1147      RelaxedFrag =
1148          relaxCVInlineLineTable(Layout, *cast<MCCVInlineLineTableFragment>(I));
1149      break;
1150    case MCFragment::FT_CVDefRange:
1151      RelaxedFrag = relaxCVDefRange(Layout, *cast<MCCVDefRangeFragment>(I));
1152      break;
1153    }
1154    if (RelaxedFrag && !FirstRelaxedFragment)
1155      FirstRelaxedFragment = &*I;
1156  }
1157  if (FirstRelaxedFragment) {
1158    Layout.invalidateFragmentsFrom(FirstRelaxedFragment);
1159    return true;
1160  }
1161  return false;
1162}
1163
1164bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
1165  ++stats::RelaxationSteps;
1166
1167  bool WasRelaxed = false;
1168  for (iterator it = begin(), ie = end(); it != ie; ++it) {
1169    MCSection &Sec = *it;
1170    while (layoutSectionOnce(Layout, Sec))
1171      WasRelaxed = true;
1172  }
1173
1174  return WasRelaxed;
1175}
1176
1177void MCAssembler::finishLayout(MCAsmLayout &Layout) {
1178  assert(getBackendPtr() && "Expected assembler backend");
1179  // The layout is done. Mark every fragment as valid.
1180  for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
1181    MCSection &Section = *Layout.getSectionOrder()[i];
1182    Layout.getFragmentOffset(&*Section.getFragmentList().rbegin());
1183    computeFragmentSize(Layout, *Section.getFragmentList().rbegin());
1184  }
1185  getBackend().finishLayout(*this, Layout);
1186}
1187
1188#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1189LLVM_DUMP_METHOD void MCAssembler::dump() const{
1190  raw_ostream &OS = errs();
1191
1192  OS << "<MCAssembler\n";
1193  OS << "  Sections:[\n    ";
1194  for (const_iterator it = begin(), ie = end(); it != ie; ++it) {
1195    if (it != begin()) OS << ",\n    ";
1196    it->dump();
1197  }
1198  OS << "],\n";
1199  OS << "  Symbols:[";
1200
1201  for (const_symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1202    if (it != symbol_begin()) OS << ",\n           ";
1203    OS << "(";
1204    it->dump();
1205    OS << ", Index:" << it->getIndex() << ", ";
1206    OS << ")";
1207  }
1208  OS << "]>\n";
1209}
1210#endif
1211