MCELFStreamer.cpp revision 360784 
1//===- lib/MC/MCELFStreamer.cpp - ELF Object Output -----------------------===//
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// This file assembles .s files and emits ELF .o object files.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/MC/MCELFStreamer.h"
14#include "llvm/ADT/SmallString.h"
15#include "llvm/ADT/SmallVector.h"
16#include "llvm/BinaryFormat/ELF.h"
17#include "llvm/MC/MCAsmBackend.h"
18#include "llvm/MC/MCAsmInfo.h"
19#include "llvm/MC/MCAssembler.h"
20#include "llvm/MC/MCCodeEmitter.h"
21#include "llvm/MC/MCContext.h"
22#include "llvm/MC/MCExpr.h"
23#include "llvm/MC/MCFixup.h"
24#include "llvm/MC/MCFragment.h"
25#include "llvm/MC/MCObjectFileInfo.h"
26#include "llvm/MC/MCObjectWriter.h"
27#include "llvm/MC/MCSection.h"
28#include "llvm/MC/MCSectionELF.h"
29#include "llvm/MC/MCStreamer.h"
30#include "llvm/MC/MCSymbol.h"
31#include "llvm/MC/MCSymbolELF.h"
32#include "llvm/Support/Casting.h"
33#include "llvm/Support/ErrorHandling.h"
34#include "llvm/Support/TargetRegistry.h"
35#include "llvm/Support/raw_ostream.h"
36#include <cassert>
37#include <cstdint>
38
39using namespace llvm;
40
41MCELFStreamer::MCELFStreamer(MCContext &Context,
42                             std::unique_ptr<MCAsmBackend> TAB,
43                             std::unique_ptr<MCObjectWriter> OW,
44                             std::unique_ptr<MCCodeEmitter> Emitter)
45    : MCObjectStreamer(Context, std::move(TAB), std::move(OW),
46                       std::move(Emitter)) {}
47
48bool MCELFStreamer::isBundleLocked() const {
49  return getCurrentSectionOnly()->isBundleLocked();
50}
51
52void MCELFStreamer::mergeFragment(MCDataFragment *DF,
53                                  MCDataFragment *EF) {
54  MCAssembler &Assembler = getAssembler();
55
56  if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
57    uint64_t FSize = EF->getContents().size();
58
59    if (FSize > Assembler.getBundleAlignSize())
60      report_fatal_error("Fragment can't be larger than a bundle size");
61
62    uint64_t RequiredBundlePadding = computeBundlePadding(
63        Assembler, EF, DF->getContents().size(), FSize);
64
65    if (RequiredBundlePadding > UINT8_MAX)
66      report_fatal_error("Padding cannot exceed 255 bytes");
67
68    if (RequiredBundlePadding > 0) {
69      SmallString<256> Code;
70      raw_svector_ostream VecOS(Code);
71      EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
72      Assembler.writeFragmentPadding(VecOS, *EF, FSize);
73
74      DF->getContents().append(Code.begin(), Code.end());
75    }
76  }
77
78  flushPendingLabels(DF, DF->getContents().size());
79
80  for (unsigned i = 0, e = EF->getFixups().size(); i != e; ++i) {
81    EF->getFixups()[i].setOffset(EF->getFixups()[i].getOffset() +
82                                 DF->getContents().size());
83    DF->getFixups().push_back(EF->getFixups()[i]);
84  }
85  if (DF->getSubtargetInfo() == nullptr && EF->getSubtargetInfo())
86    DF->setHasInstructions(*EF->getSubtargetInfo());
87  DF->getContents().append(EF->getContents().begin(), EF->getContents().end());
88}
89
90void MCELFStreamer::InitSections(bool NoExecStack) {
91  MCContext &Ctx = getContext();
92  SwitchSection(Ctx.getObjectFileInfo()->getTextSection());
93  EmitCodeAlignment(4);
94
95  if (NoExecStack)
96    SwitchSection(Ctx.getAsmInfo()->getNonexecutableStackSection(Ctx));
97}
98
99void MCELFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc) {
100  auto *Symbol = cast<MCSymbolELF>(S);
101  MCObjectStreamer::EmitLabel(Symbol, Loc);
102
103  const MCSectionELF &Section =
104      static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
105  if (Section.getFlags() & ELF::SHF_TLS)
106    Symbol->setType(ELF::STT_TLS);
107}
108
109void MCELFStreamer::EmitLabelAtPos(MCSymbol *S, SMLoc Loc, MCFragment *F,
110                                   uint64_t Offset) {
111  auto *Symbol = cast<MCSymbolELF>(S);
112  MCObjectStreamer::EmitLabelAtPos(Symbol, Loc, F, Offset);
113
114  const MCSectionELF &Section =
115      static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
116  if (Section.getFlags() & ELF::SHF_TLS)
117    Symbol->setType(ELF::STT_TLS);
118}
119
120void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
121  // Let the target do whatever target specific stuff it needs to do.
122  getAssembler().getBackend().handleAssemblerFlag(Flag);
123  // Do any generic stuff we need to do.
124  switch (Flag) {
125  case MCAF_SyntaxUnified: return; // no-op here.
126  case MCAF_Code16: return; // Change parsing mode; no-op here.
127  case MCAF_Code32: return; // Change parsing mode; no-op here.
128  case MCAF_Code64: return; // Change parsing mode; no-op here.
129  case MCAF_SubsectionsViaSymbols:
130    getAssembler().setSubsectionsViaSymbols(true);
131    return;
132  }
133
134  llvm_unreachable("invalid assembler flag!");
135}
136
137// If bundle alignment is used and there are any instructions in the section, it
138// needs to be aligned to at least the bundle size.
139static void setSectionAlignmentForBundling(const MCAssembler &Assembler,
140                                           MCSection *Section) {
141  if (Section && Assembler.isBundlingEnabled() && Section->hasInstructions() &&
142      Section->getAlignment() < Assembler.getBundleAlignSize())
143    Section->setAlignment(Align(Assembler.getBundleAlignSize()));
144}
145
146void MCELFStreamer::ChangeSection(MCSection *Section,
147                                  const MCExpr *Subsection) {
148  MCSection *CurSection = getCurrentSectionOnly();
149  if (CurSection && isBundleLocked())
150    report_fatal_error("Unterminated .bundle_lock when changing a section");
151
152  MCAssembler &Asm = getAssembler();
153  // Ensure the previous section gets aligned if necessary.
154  setSectionAlignmentForBundling(Asm, CurSection);
155  auto *SectionELF = static_cast<const MCSectionELF *>(Section);
156  const MCSymbol *Grp = SectionELF->getGroup();
157  if (Grp)
158    Asm.registerSymbol(*Grp);
159
160  changeSectionImpl(Section, Subsection);
161  Asm.registerSymbol(*Section->getBeginSymbol());
162}
163
164void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
165  getAssembler().registerSymbol(*Symbol);
166  const MCExpr *Value = MCSymbolRefExpr::create(
167      Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext());
168  Alias->setVariableValue(Value);
169}
170
171// When GNU as encounters more than one .type declaration for an object it seems
172// to use a mechanism similar to the one below to decide which type is actually
173// used in the object file.  The greater of T1 and T2 is selected based on the
174// following ordering:
175//  STT_NOTYPE < STT_OBJECT < STT_FUNC < STT_GNU_IFUNC < STT_TLS < anything else
176// If neither T1 < T2 nor T2 < T1 according to this ordering, use T2 (the user
177// provided type).
178static unsigned CombineSymbolTypes(unsigned T1, unsigned T2) {
179  for (unsigned Type : {ELF::STT_NOTYPE, ELF::STT_OBJECT, ELF::STT_FUNC,
180                        ELF::STT_GNU_IFUNC, ELF::STT_TLS}) {
181    if (T1 == Type)
182      return T2;
183    if (T2 == Type)
184      return T1;
185  }
186
187  return T2;
188}
189
190bool MCELFStreamer::EmitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
191  auto *Symbol = cast<MCSymbolELF>(S);
192
193  // Adding a symbol attribute always introduces the symbol, note that an
194  // important side effect of calling registerSymbol here is to register
195  // the symbol with the assembler.
196  getAssembler().registerSymbol(*Symbol);
197
198  // The implementation of symbol attributes is designed to match 'as', but it
199  // leaves much to desired. It doesn't really make sense to arbitrarily add and
200  // remove flags, but 'as' allows this (in particular, see .desc).
201  //
202  // In the future it might be worth trying to make these operations more well
203  // defined.
204  switch (Attribute) {
205  case MCSA_Cold:
206  case MCSA_LazyReference:
207  case MCSA_Reference:
208  case MCSA_SymbolResolver:
209  case MCSA_PrivateExtern:
210  case MCSA_WeakDefinition:
211  case MCSA_WeakDefAutoPrivate:
212  case MCSA_Invalid:
213  case MCSA_IndirectSymbol:
214    return false;
215
216  case MCSA_NoDeadStrip:
217    // Ignore for now.
218    break;
219
220  case MCSA_ELF_TypeGnuUniqueObject:
221    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
222    Symbol->setBinding(ELF::STB_GNU_UNIQUE);
223    Symbol->setExternal(true);
224    break;
225
226  case MCSA_Global:
227    Symbol->setBinding(ELF::STB_GLOBAL);
228    Symbol->setExternal(true);
229    break;
230
231  case MCSA_WeakReference:
232  case MCSA_Weak:
233    Symbol->setBinding(ELF::STB_WEAK);
234    Symbol->setExternal(true);
235    break;
236
237  case MCSA_Local:
238    Symbol->setBinding(ELF::STB_LOCAL);
239    Symbol->setExternal(false);
240    break;
241
242  case MCSA_ELF_TypeFunction:
243    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_FUNC));
244    break;
245
246  case MCSA_ELF_TypeIndFunction:
247    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_GNU_IFUNC));
248    break;
249
250  case MCSA_ELF_TypeObject:
251    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
252    break;
253
254  case MCSA_ELF_TypeTLS:
255    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_TLS));
256    break;
257
258  case MCSA_ELF_TypeCommon:
259    // TODO: Emit these as a common symbol.
260    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
261    break;
262
263  case MCSA_ELF_TypeNoType:
264    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_NOTYPE));
265    break;
266
267  case MCSA_Protected:
268    Symbol->setVisibility(ELF::STV_PROTECTED);
269    break;
270
271  case MCSA_Hidden:
272    Symbol->setVisibility(ELF::STV_HIDDEN);
273    break;
274
275  case MCSA_Internal:
276    Symbol->setVisibility(ELF::STV_INTERNAL);
277    break;
278
279  case MCSA_AltEntry:
280    llvm_unreachable("ELF doesn't support the .alt_entry attribute");
281
282  case MCSA_LGlobal:
283    llvm_unreachable("ELF doesn't support the .lglobl attribute");
284  }
285
286  return true;
287}
288
289void MCELFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
290                                     unsigned ByteAlignment) {
291  auto *Symbol = cast<MCSymbolELF>(S);
292  getAssembler().registerSymbol(*Symbol);
293
294  if (!Symbol->isBindingSet()) {
295    Symbol->setBinding(ELF::STB_GLOBAL);
296    Symbol->setExternal(true);
297  }
298
299  Symbol->setType(ELF::STT_OBJECT);
300
301  if (Symbol->getBinding() == ELF::STB_LOCAL) {
302    MCSection &Section = *getAssembler().getContext().getELFSection(
303        ".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
304    MCSectionSubPair P = getCurrentSection();
305    SwitchSection(&Section);
306
307    EmitValueToAlignment(ByteAlignment, 0, 1, 0);
308    EmitLabel(Symbol);
309    EmitZeros(Size);
310
311    SwitchSection(P.first, P.second);
312  } else {
313    if(Symbol->declareCommon(Size, ByteAlignment))
314      report_fatal_error("Symbol: " + Symbol->getName() +
315                         " redeclared as different type");
316  }
317
318  cast<MCSymbolELF>(Symbol)
319      ->setSize(MCConstantExpr::create(Size, getContext()));
320}
321
322void MCELFStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
323  cast<MCSymbolELF>(Symbol)->setSize(Value);
324}
325
326void MCELFStreamer::emitELFSymverDirective(StringRef AliasName,
327                                           const MCSymbol *Aliasee) {
328  getAssembler().Symvers.push_back({AliasName, Aliasee});
329}
330
331void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
332                                          unsigned ByteAlignment) {
333  auto *Symbol = cast<MCSymbolELF>(S);
334  // FIXME: Should this be caught and done earlier?
335  getAssembler().registerSymbol(*Symbol);
336  Symbol->setBinding(ELF::STB_LOCAL);
337  Symbol->setExternal(false);
338  EmitCommonSymbol(Symbol, Size, ByteAlignment);
339}
340
341void MCELFStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
342                                  SMLoc Loc) {
343  if (isBundleLocked())
344    report_fatal_error("Emitting values inside a locked bundle is forbidden");
345  fixSymbolsInTLSFixups(Value);
346  MCObjectStreamer::EmitValueImpl(Value, Size, Loc);
347}
348
349void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
350                                         int64_t Value,
351                                         unsigned ValueSize,
352                                         unsigned MaxBytesToEmit) {
353  if (isBundleLocked())
354    report_fatal_error("Emitting values inside a locked bundle is forbidden");
355  MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value,
356                                         ValueSize, MaxBytesToEmit);
357}
358
359void MCELFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
360                                       const MCSymbolRefExpr *To,
361                                       uint64_t Count) {
362  getAssembler().CGProfile.push_back({From, To, Count});
363}
364
365void MCELFStreamer::EmitIdent(StringRef IdentString) {
366  MCSection *Comment = getAssembler().getContext().getELFSection(
367      ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
368  PushSection();
369  SwitchSection(Comment);
370  if (!SeenIdent) {
371    EmitIntValue(0, 1);
372    SeenIdent = true;
373  }
374  EmitBytes(IdentString);
375  EmitIntValue(0, 1);
376  PopSection();
377}
378
379void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
380  switch (expr->getKind()) {
381  case MCExpr::Target:
382    cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
383    break;
384  case MCExpr::Constant:
385    break;
386
387  case MCExpr::Binary: {
388    const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
389    fixSymbolsInTLSFixups(be->getLHS());
390    fixSymbolsInTLSFixups(be->getRHS());
391    break;
392  }
393
394  case MCExpr::SymbolRef: {
395    const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
396    switch (symRef.getKind()) {
397    default:
398      return;
399    case MCSymbolRefExpr::VK_GOTTPOFF:
400    case MCSymbolRefExpr::VK_INDNTPOFF:
401    case MCSymbolRefExpr::VK_NTPOFF:
402    case MCSymbolRefExpr::VK_GOTNTPOFF:
403    case MCSymbolRefExpr::VK_TLSCALL:
404    case MCSymbolRefExpr::VK_TLSDESC:
405    case MCSymbolRefExpr::VK_TLSGD:
406    case MCSymbolRefExpr::VK_TLSLD:
407    case MCSymbolRefExpr::VK_TLSLDM:
408    case MCSymbolRefExpr::VK_TPOFF:
409    case MCSymbolRefExpr::VK_TPREL:
410    case MCSymbolRefExpr::VK_DTPOFF:
411    case MCSymbolRefExpr::VK_DTPREL:
412    case MCSymbolRefExpr::VK_PPC_DTPMOD:
413    case MCSymbolRefExpr::VK_PPC_TPREL_LO:
414    case MCSymbolRefExpr::VK_PPC_TPREL_HI:
415    case MCSymbolRefExpr::VK_PPC_TPREL_HA:
416    case MCSymbolRefExpr::VK_PPC_TPREL_HIGH:
417    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHA:
418    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
419    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
420    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
421    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
422    case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
423    case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
424    case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
425    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGH:
426    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHA:
427    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
428    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
429    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
430    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
431    case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
432    case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
433    case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
434    case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
435    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
436    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
437    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
438    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
439    case MCSymbolRefExpr::VK_PPC_TLS:
440    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
441    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
442    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
443    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
444    case MCSymbolRefExpr::VK_PPC_TLSGD:
445    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
446    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
447    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
448    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
449    case MCSymbolRefExpr::VK_PPC_TLSLD:
450      break;
451    }
452    getAssembler().registerSymbol(symRef.getSymbol());
453    cast<MCSymbolELF>(symRef.getSymbol()).setType(ELF::STT_TLS);
454    break;
455  }
456
457  case MCExpr::Unary:
458    fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
459    break;
460  }
461}
462
463void MCELFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
464  const MCSymbol *S = &SRE->getSymbol();
465  if (S->isTemporary()) {
466    if (!S->isInSection()) {
467      getContext().reportError(
468          SRE->getLoc(), Twine("Reference to undefined temporary symbol ") +
469                             "`" + S->getName() + "`");
470      return;
471    }
472    S = S->getSection().getBeginSymbol();
473    S->setUsedInReloc();
474    SRE =
475        MCSymbolRefExpr::create(S, SRE->getKind(), getContext(), SRE->getLoc());
476    return;
477  }
478  // Not a temporary, referece it as a weak undefined.
479  bool Created;
480  getAssembler().registerSymbol(*S, &Created);
481  if (Created) {
482    cast<MCSymbolELF>(S)->setBinding(ELF::STB_WEAK);
483    cast<MCSymbolELF>(S)->setExternal(true);
484  }
485}
486
487void MCELFStreamer::finalizeCGProfile() {
488  for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
489    finalizeCGProfileEntry(E.From);
490    finalizeCGProfileEntry(E.To);
491  }
492}
493
494void MCELFStreamer::EmitInstToFragment(const MCInst &Inst,
495                                       const MCSubtargetInfo &STI) {
496  this->MCObjectStreamer::EmitInstToFragment(Inst, STI);
497  MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
498
499  for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
500    fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
501}
502
503// A fragment can only have one Subtarget, and when bundling is enabled we
504// sometimes need to use the same fragment. We give an error if there
505// are conflicting Subtargets.
506static void CheckBundleSubtargets(const MCSubtargetInfo *OldSTI,
507                                  const MCSubtargetInfo *NewSTI) {
508  if (OldSTI && NewSTI && OldSTI != NewSTI)
509    report_fatal_error("A Bundle can only have one Subtarget.");
510}
511
512void MCELFStreamer::EmitInstToData(const MCInst &Inst,
513                                   const MCSubtargetInfo &STI) {
514  MCAssembler &Assembler = getAssembler();
515  SmallVector<MCFixup, 4> Fixups;
516  SmallString<256> Code;
517  raw_svector_ostream VecOS(Code);
518  Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
519
520  for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
521    fixSymbolsInTLSFixups(Fixups[i].getValue());
522
523  // There are several possibilities here:
524  //
525  // If bundling is disabled, append the encoded instruction to the current data
526  // fragment (or create a new such fragment if the current fragment is not a
527  // data fragment, or the Subtarget has changed).
528  //
529  // If bundling is enabled:
530  // - If we're not in a bundle-locked group, emit the instruction into a
531  //   fragment of its own. If there are no fixups registered for the
532  //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
533  //   MCDataFragment.
534  // - If we're in a bundle-locked group, append the instruction to the current
535  //   data fragment because we want all the instructions in a group to get into
536  //   the same fragment. Be careful not to do that for the first instruction in
537  //   the group, though.
538  MCDataFragment *DF;
539
540  if (Assembler.isBundlingEnabled()) {
541    MCSection &Sec = *getCurrentSectionOnly();
542    if (Assembler.getRelaxAll() && isBundleLocked()) {
543      // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
544      // the current bundle group.
545      DF = BundleGroups.back();
546      CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
547    }
548    else if (Assembler.getRelaxAll() && !isBundleLocked())
549      // When not in a bundle-locked group and the -mc-relax-all flag is used,
550      // we create a new temporary fragment which will be later merged into
551      // the current fragment.
552      DF = new MCDataFragment();
553    else if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst()) {
554      // If we are bundle-locked, we re-use the current fragment.
555      // The bundle-locking directive ensures this is a new data fragment.
556      DF = cast<MCDataFragment>(getCurrentFragment());
557      CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
558    }
559    else if (!isBundleLocked() && Fixups.size() == 0) {
560      // Optimize memory usage by emitting the instruction to a
561      // MCCompactEncodedInstFragment when not in a bundle-locked group and
562      // there are no fixups registered.
563      MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
564      insert(CEIF);
565      CEIF->getContents().append(Code.begin(), Code.end());
566      CEIF->setHasInstructions(STI);
567      return;
568    } else {
569      DF = new MCDataFragment();
570      insert(DF);
571    }
572    if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
573      // If this fragment is for a group marked "align_to_end", set a flag
574      // in the fragment. This can happen after the fragment has already been
575      // created if there are nested bundle_align groups and an inner one
576      // is the one marked align_to_end.
577      DF->setAlignToBundleEnd(true);
578    }
579
580    // We're now emitting an instruction in a bundle group, so this flag has
581    // to be turned off.
582    Sec.setBundleGroupBeforeFirstInst(false);
583  } else {
584    DF = getOrCreateDataFragment(&STI);
585  }
586
587  // Add the fixups and data.
588  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
589    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
590    DF->getFixups().push_back(Fixups[i]);
591  }
592  DF->setHasInstructions(STI);
593  DF->getContents().append(Code.begin(), Code.end());
594
595  if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
596    if (!isBundleLocked()) {
597      mergeFragment(getOrCreateDataFragment(&STI), DF);
598      delete DF;
599    }
600  }
601}
602
603void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
604  assert(AlignPow2 <= 30 && "Invalid bundle alignment");
605  MCAssembler &Assembler = getAssembler();
606  if (AlignPow2 > 0 && (Assembler.getBundleAlignSize() == 0 ||
607                        Assembler.getBundleAlignSize() == 1U << AlignPow2))
608    Assembler.setBundleAlignSize(1U << AlignPow2);
609  else
610    report_fatal_error(".bundle_align_mode cannot be changed once set");
611}
612
613void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
614  MCSection &Sec = *getCurrentSectionOnly();
615
616  // Sanity checks
617  //
618  if (!getAssembler().isBundlingEnabled())
619    report_fatal_error(".bundle_lock forbidden when bundling is disabled");
620
621  if (!isBundleLocked())
622    Sec.setBundleGroupBeforeFirstInst(true);
623
624  if (getAssembler().getRelaxAll() && !isBundleLocked()) {
625    // TODO: drop the lock state and set directly in the fragment
626    MCDataFragment *DF = new MCDataFragment();
627    BundleGroups.push_back(DF);
628  }
629
630  Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
631                                    : MCSection::BundleLocked);
632}
633
634void MCELFStreamer::EmitBundleUnlock() {
635  MCSection &Sec = *getCurrentSectionOnly();
636
637  // Sanity checks
638  if (!getAssembler().isBundlingEnabled())
639    report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
640  else if (!isBundleLocked())
641    report_fatal_error(".bundle_unlock without matching lock");
642  else if (Sec.isBundleGroupBeforeFirstInst())
643    report_fatal_error("Empty bundle-locked group is forbidden");
644
645  // When the -mc-relax-all flag is used, we emit instructions to fragments
646  // stored on a stack. When the bundle unlock is emitted, we pop a fragment
647  // from the stack a merge it to the one below.
648  if (getAssembler().getRelaxAll()) {
649    assert(!BundleGroups.empty() && "There are no bundle groups");
650    MCDataFragment *DF = BundleGroups.back();
651
652    // FIXME: Use BundleGroups to track the lock state instead.
653    Sec.setBundleLockState(MCSection::NotBundleLocked);
654
655    // FIXME: Use more separate fragments for nested groups.
656    if (!isBundleLocked()) {
657      mergeFragment(getOrCreateDataFragment(DF->getSubtargetInfo()), DF);
658      BundleGroups.pop_back();
659      delete DF;
660    }
661
662    if (Sec.getBundleLockState() != MCSection::BundleLockedAlignToEnd)
663      getOrCreateDataFragment()->setAlignToBundleEnd(false);
664  } else
665    Sec.setBundleLockState(MCSection::NotBundleLocked);
666}
667
668void MCELFStreamer::FinishImpl() {
669  // Ensure the last section gets aligned if necessary.
670  MCSection *CurSection = getCurrentSectionOnly();
671  setSectionAlignmentForBundling(getAssembler(), CurSection);
672
673  finalizeCGProfile();
674  EmitFrames(nullptr);
675
676  this->MCObjectStreamer::FinishImpl();
677}
678
679void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
680  llvm_unreachable("Generic ELF doesn't support this directive");
681}
682
683void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
684  llvm_unreachable("ELF doesn't support this directive");
685}
686
687void MCELFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
688                                 uint64_t Size, unsigned ByteAlignment,
689                                 SMLoc Loc) {
690  llvm_unreachable("ELF doesn't support this directive");
691}
692
693void MCELFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
694                                   uint64_t Size, unsigned ByteAlignment) {
695  llvm_unreachable("ELF doesn't support this directive");
696}
697
698MCStreamer *llvm::createELFStreamer(MCContext &Context,
699                                    std::unique_ptr<MCAsmBackend> &&MAB,
700                                    std::unique_ptr<MCObjectWriter> &&OW,
701                                    std::unique_ptr<MCCodeEmitter> &&CE,
702                                    bool RelaxAll) {
703  MCELFStreamer *S =
704      new MCELFStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
705  if (RelaxAll)
706    S->getAssembler().setRelaxAll(true);
707  return S;
708}
709