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_Extern:
207  case MCSA_LazyReference:
208  case MCSA_Reference:
209  case MCSA_SymbolResolver:
210  case MCSA_PrivateExtern:
211  case MCSA_WeakDefinition:
212  case MCSA_WeakDefAutoPrivate:
213  case MCSA_Invalid:
214  case MCSA_IndirectSymbol:
215    return false;
216
217  case MCSA_NoDeadStrip:
218    // Ignore for now.
219    break;
220
221  case MCSA_ELF_TypeGnuUniqueObject:
222    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
223    Symbol->setBinding(ELF::STB_GNU_UNIQUE);
224    Symbol->setExternal(true);
225    break;
226
227  case MCSA_Global:
228    Symbol->setBinding(ELF::STB_GLOBAL);
229    Symbol->setExternal(true);
230    break;
231
232  case MCSA_WeakReference:
233  case MCSA_Weak:
234    Symbol->setBinding(ELF::STB_WEAK);
235    Symbol->setExternal(true);
236    break;
237
238  case MCSA_Local:
239    Symbol->setBinding(ELF::STB_LOCAL);
240    Symbol->setExternal(false);
241    break;
242
243  case MCSA_ELF_TypeFunction:
244    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_FUNC));
245    break;
246
247  case MCSA_ELF_TypeIndFunction:
248    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_GNU_IFUNC));
249    break;
250
251  case MCSA_ELF_TypeObject:
252    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
253    break;
254
255  case MCSA_ELF_TypeTLS:
256    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_TLS));
257    break;
258
259  case MCSA_ELF_TypeCommon:
260    // TODO: Emit these as a common symbol.
261    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
262    break;
263
264  case MCSA_ELF_TypeNoType:
265    Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_NOTYPE));
266    break;
267
268  case MCSA_Protected:
269    Symbol->setVisibility(ELF::STV_PROTECTED);
270    break;
271
272  case MCSA_Hidden:
273    Symbol->setVisibility(ELF::STV_HIDDEN);
274    break;
275
276  case MCSA_Internal:
277    Symbol->setVisibility(ELF::STV_INTERNAL);
278    break;
279
280  case MCSA_AltEntry:
281    llvm_unreachable("ELF doesn't support the .alt_entry attribute");
282
283  case MCSA_LGlobal:
284    llvm_unreachable("ELF doesn't support the .lglobl attribute");
285  }
286
287  return true;
288}
289
290void MCELFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
291                                     unsigned ByteAlignment) {
292  auto *Symbol = cast<MCSymbolELF>(S);
293  getAssembler().registerSymbol(*Symbol);
294
295  if (!Symbol->isBindingSet()) {
296    Symbol->setBinding(ELF::STB_GLOBAL);
297    Symbol->setExternal(true);
298  }
299
300  Symbol->setType(ELF::STT_OBJECT);
301
302  if (Symbol->getBinding() == ELF::STB_LOCAL) {
303    MCSection &Section = *getAssembler().getContext().getELFSection(
304        ".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
305    MCSectionSubPair P = getCurrentSection();
306    SwitchSection(&Section);
307
308    emitValueToAlignment(ByteAlignment, 0, 1, 0);
309    emitLabel(Symbol);
310    emitZeros(Size);
311
312    SwitchSection(P.first, P.second);
313  } else {
314    if(Symbol->declareCommon(Size, ByteAlignment))
315      report_fatal_error("Symbol: " + Symbol->getName() +
316                         " redeclared as different type");
317  }
318
319  cast<MCSymbolELF>(Symbol)
320      ->setSize(MCConstantExpr::create(Size, getContext()));
321}
322
323void MCELFStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
324  cast<MCSymbolELF>(Symbol)->setSize(Value);
325}
326
327void MCELFStreamer::emitELFSymverDirective(StringRef AliasName,
328                                           const MCSymbol *Aliasee) {
329  getAssembler().Symvers.push_back({AliasName, Aliasee});
330}
331
332void MCELFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
333                                          unsigned ByteAlignment) {
334  auto *Symbol = cast<MCSymbolELF>(S);
335  // FIXME: Should this be caught and done earlier?
336  getAssembler().registerSymbol(*Symbol);
337  Symbol->setBinding(ELF::STB_LOCAL);
338  Symbol->setExternal(false);
339  emitCommonSymbol(Symbol, Size, ByteAlignment);
340}
341
342void MCELFStreamer::emitValueImpl(const MCExpr *Value, unsigned Size,
343                                  SMLoc Loc) {
344  if (isBundleLocked())
345    report_fatal_error("Emitting values inside a locked bundle is forbidden");
346  fixSymbolsInTLSFixups(Value);
347  MCObjectStreamer::emitValueImpl(Value, Size, Loc);
348}
349
350void MCELFStreamer::emitValueToAlignment(unsigned ByteAlignment,
351                                         int64_t Value,
352                                         unsigned ValueSize,
353                                         unsigned MaxBytesToEmit) {
354  if (isBundleLocked())
355    report_fatal_error("Emitting values inside a locked bundle is forbidden");
356  MCObjectStreamer::emitValueToAlignment(ByteAlignment, Value,
357                                         ValueSize, MaxBytesToEmit);
358}
359
360void MCELFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
361                                       const MCSymbolRefExpr *To,
362                                       uint64_t Count) {
363  getAssembler().CGProfile.push_back({From, To, Count});
364}
365
366void MCELFStreamer::emitIdent(StringRef IdentString) {
367  MCSection *Comment = getAssembler().getContext().getELFSection(
368      ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
369  PushSection();
370  SwitchSection(Comment);
371  if (!SeenIdent) {
372    emitInt8(0);
373    SeenIdent = true;
374  }
375  emitBytes(IdentString);
376  emitInt8(0);
377  PopSection();
378}
379
380void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
381  switch (expr->getKind()) {
382  case MCExpr::Target:
383    cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
384    break;
385  case MCExpr::Constant:
386    break;
387
388  case MCExpr::Binary: {
389    const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
390    fixSymbolsInTLSFixups(be->getLHS());
391    fixSymbolsInTLSFixups(be->getRHS());
392    break;
393  }
394
395  case MCExpr::SymbolRef: {
396    const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
397    switch (symRef.getKind()) {
398    default:
399      return;
400    case MCSymbolRefExpr::VK_GOTTPOFF:
401    case MCSymbolRefExpr::VK_INDNTPOFF:
402    case MCSymbolRefExpr::VK_NTPOFF:
403    case MCSymbolRefExpr::VK_GOTNTPOFF:
404    case MCSymbolRefExpr::VK_TLSCALL:
405    case MCSymbolRefExpr::VK_TLSDESC:
406    case MCSymbolRefExpr::VK_TLSGD:
407    case MCSymbolRefExpr::VK_TLSLD:
408    case MCSymbolRefExpr::VK_TLSLDM:
409    case MCSymbolRefExpr::VK_TPOFF:
410    case MCSymbolRefExpr::VK_TPREL:
411    case MCSymbolRefExpr::VK_DTPOFF:
412    case MCSymbolRefExpr::VK_DTPREL:
413    case MCSymbolRefExpr::VK_PPC_DTPMOD:
414    case MCSymbolRefExpr::VK_PPC_TPREL_LO:
415    case MCSymbolRefExpr::VK_PPC_TPREL_HI:
416    case MCSymbolRefExpr::VK_PPC_TPREL_HA:
417    case MCSymbolRefExpr::VK_PPC_TPREL_HIGH:
418    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHA:
419    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
420    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
421    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
422    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
423    case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
424    case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
425    case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
426    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGH:
427    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHA:
428    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
429    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
430    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
431    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
432    case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
433    case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
434    case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
435    case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
436    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
437    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
438    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
439    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
440    case MCSymbolRefExpr::VK_PPC_TLS:
441    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
442    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
443    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
444    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
445    case MCSymbolRefExpr::VK_PPC_TLSGD:
446    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
447    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
448    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
449    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
450    case MCSymbolRefExpr::VK_PPC_TLSLD:
451      break;
452    }
453    getAssembler().registerSymbol(symRef.getSymbol());
454    cast<MCSymbolELF>(symRef.getSymbol()).setType(ELF::STT_TLS);
455    break;
456  }
457
458  case MCExpr::Unary:
459    fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
460    break;
461  }
462}
463
464void MCELFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
465  const MCSymbol *S = &SRE->getSymbol();
466  if (S->isTemporary()) {
467    if (!S->isInSection()) {
468      getContext().reportError(
469          SRE->getLoc(), Twine("Reference to undefined temporary symbol ") +
470                             "`" + S->getName() + "`");
471      return;
472    }
473    S = S->getSection().getBeginSymbol();
474    S->setUsedInReloc();
475    SRE =
476        MCSymbolRefExpr::create(S, SRE->getKind(), getContext(), SRE->getLoc());
477    return;
478  }
479  // Not a temporary, referece it as a weak undefined.
480  bool Created;
481  getAssembler().registerSymbol(*S, &Created);
482  if (Created) {
483    cast<MCSymbolELF>(S)->setBinding(ELF::STB_WEAK);
484    cast<MCSymbolELF>(S)->setExternal(true);
485  }
486}
487
488void MCELFStreamer::finalizeCGProfile() {
489  for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
490    finalizeCGProfileEntry(E.From);
491    finalizeCGProfileEntry(E.To);
492  }
493}
494
495void MCELFStreamer::emitInstToFragment(const MCInst &Inst,
496                                       const MCSubtargetInfo &STI) {
497  this->MCObjectStreamer::emitInstToFragment(Inst, STI);
498  MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
499
500  for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
501    fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
502}
503
504// A fragment can only have one Subtarget, and when bundling is enabled we
505// sometimes need to use the same fragment. We give an error if there
506// are conflicting Subtargets.
507static void CheckBundleSubtargets(const MCSubtargetInfo *OldSTI,
508                                  const MCSubtargetInfo *NewSTI) {
509  if (OldSTI && NewSTI && OldSTI != NewSTI)
510    report_fatal_error("A Bundle can only have one Subtarget.");
511}
512
513void MCELFStreamer::emitInstToData(const MCInst &Inst,
514                                   const MCSubtargetInfo &STI) {
515  MCAssembler &Assembler = getAssembler();
516  SmallVector<MCFixup, 4> Fixups;
517  SmallString<256> Code;
518  raw_svector_ostream VecOS(Code);
519  Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
520
521  for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
522    fixSymbolsInTLSFixups(Fixups[i].getValue());
523
524  // There are several possibilities here:
525  //
526  // If bundling is disabled, append the encoded instruction to the current data
527  // fragment (or create a new such fragment if the current fragment is not a
528  // data fragment, or the Subtarget has changed).
529  //
530  // If bundling is enabled:
531  // - If we're not in a bundle-locked group, emit the instruction into a
532  //   fragment of its own. If there are no fixups registered for the
533  //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
534  //   MCDataFragment.
535  // - If we're in a bundle-locked group, append the instruction to the current
536  //   data fragment because we want all the instructions in a group to get into
537  //   the same fragment. Be careful not to do that for the first instruction in
538  //   the group, though.
539  MCDataFragment *DF;
540
541  if (Assembler.isBundlingEnabled()) {
542    MCSection &Sec = *getCurrentSectionOnly();
543    if (Assembler.getRelaxAll() && isBundleLocked()) {
544      // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
545      // the current bundle group.
546      DF = BundleGroups.back();
547      CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
548    }
549    else if (Assembler.getRelaxAll() && !isBundleLocked())
550      // When not in a bundle-locked group and the -mc-relax-all flag is used,
551      // we create a new temporary fragment which will be later merged into
552      // the current fragment.
553      DF = new MCDataFragment();
554    else if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst()) {
555      // If we are bundle-locked, we re-use the current fragment.
556      // The bundle-locking directive ensures this is a new data fragment.
557      DF = cast<MCDataFragment>(getCurrentFragment());
558      CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
559    }
560    else if (!isBundleLocked() && Fixups.size() == 0) {
561      // Optimize memory usage by emitting the instruction to a
562      // MCCompactEncodedInstFragment when not in a bundle-locked group and
563      // there are no fixups registered.
564      MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
565      insert(CEIF);
566      CEIF->getContents().append(Code.begin(), Code.end());
567      CEIF->setHasInstructions(STI);
568      return;
569    } else {
570      DF = new MCDataFragment();
571      insert(DF);
572    }
573    if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
574      // If this fragment is for a group marked "align_to_end", set a flag
575      // in the fragment. This can happen after the fragment has already been
576      // created if there are nested bundle_align groups and an inner one
577      // is the one marked align_to_end.
578      DF->setAlignToBundleEnd(true);
579    }
580
581    // We're now emitting an instruction in a bundle group, so this flag has
582    // to be turned off.
583    Sec.setBundleGroupBeforeFirstInst(false);
584  } else {
585    DF = getOrCreateDataFragment(&STI);
586  }
587
588  // Add the fixups and data.
589  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
590    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
591    DF->getFixups().push_back(Fixups[i]);
592  }
593  DF->setHasInstructions(STI);
594  DF->getContents().append(Code.begin(), Code.end());
595
596  if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
597    if (!isBundleLocked()) {
598      mergeFragment(getOrCreateDataFragment(&STI), DF);
599      delete DF;
600    }
601  }
602}
603
604void MCELFStreamer::emitBundleAlignMode(unsigned AlignPow2) {
605  assert(AlignPow2 <= 30 && "Invalid bundle alignment");
606  MCAssembler &Assembler = getAssembler();
607  if (AlignPow2 > 0 && (Assembler.getBundleAlignSize() == 0 ||
608                        Assembler.getBundleAlignSize() == 1U << AlignPow2))
609    Assembler.setBundleAlignSize(1U << AlignPow2);
610  else
611    report_fatal_error(".bundle_align_mode cannot be changed once set");
612}
613
614void MCELFStreamer::emitBundleLock(bool AlignToEnd) {
615  MCSection &Sec = *getCurrentSectionOnly();
616
617  // Sanity checks
618  //
619  if (!getAssembler().isBundlingEnabled())
620    report_fatal_error(".bundle_lock forbidden when bundling is disabled");
621
622  if (!isBundleLocked())
623    Sec.setBundleGroupBeforeFirstInst(true);
624
625  if (getAssembler().getRelaxAll() && !isBundleLocked()) {
626    // TODO: drop the lock state and set directly in the fragment
627    MCDataFragment *DF = new MCDataFragment();
628    BundleGroups.push_back(DF);
629  }
630
631  Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
632                                    : MCSection::BundleLocked);
633}
634
635void MCELFStreamer::emitBundleUnlock() {
636  MCSection &Sec = *getCurrentSectionOnly();
637
638  // Sanity checks
639  if (!getAssembler().isBundlingEnabled())
640    report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
641  else if (!isBundleLocked())
642    report_fatal_error(".bundle_unlock without matching lock");
643  else if (Sec.isBundleGroupBeforeFirstInst())
644    report_fatal_error("Empty bundle-locked group is forbidden");
645
646  // When the -mc-relax-all flag is used, we emit instructions to fragments
647  // stored on a stack. When the bundle unlock is emitted, we pop a fragment
648  // from the stack a merge it to the one below.
649  if (getAssembler().getRelaxAll()) {
650    assert(!BundleGroups.empty() && "There are no bundle groups");
651    MCDataFragment *DF = BundleGroups.back();
652
653    // FIXME: Use BundleGroups to track the lock state instead.
654    Sec.setBundleLockState(MCSection::NotBundleLocked);
655
656    // FIXME: Use more separate fragments for nested groups.
657    if (!isBundleLocked()) {
658      mergeFragment(getOrCreateDataFragment(DF->getSubtargetInfo()), DF);
659      BundleGroups.pop_back();
660      delete DF;
661    }
662
663    if (Sec.getBundleLockState() != MCSection::BundleLockedAlignToEnd)
664      getOrCreateDataFragment()->setAlignToBundleEnd(false);
665  } else
666    Sec.setBundleLockState(MCSection::NotBundleLocked);
667}
668
669void MCELFStreamer::finishImpl() {
670  // Ensure the last section gets aligned if necessary.
671  MCSection *CurSection = getCurrentSectionOnly();
672  setSectionAlignmentForBundling(getAssembler(), CurSection);
673
674  finalizeCGProfile();
675  emitFrames(nullptr);
676
677  this->MCObjectStreamer::finishImpl();
678}
679
680void MCELFStreamer::emitThumbFunc(MCSymbol *Func) {
681  llvm_unreachable("Generic ELF doesn't support this directive");
682}
683
684void MCELFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
685  llvm_unreachable("ELF doesn't support this directive");
686}
687
688void MCELFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
689                                 uint64_t Size, unsigned ByteAlignment,
690                                 SMLoc Loc) {
691  llvm_unreachable("ELF doesn't support this directive");
692}
693
694void MCELFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
695                                   uint64_t Size, unsigned ByteAlignment) {
696  llvm_unreachable("ELF doesn't support this directive");
697}
698
699MCStreamer *llvm::createELFStreamer(MCContext &Context,
700                                    std::unique_ptr<MCAsmBackend> &&MAB,
701                                    std::unique_ptr<MCObjectWriter> &&OW,
702                                    std::unique_ptr<MCCodeEmitter> &&CE,
703                                    bool RelaxAll) {
704  MCELFStreamer *S =
705      new MCELFStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
706  if (RelaxAll)
707    S->getAssembler().setRelaxAll(true);
708  return S;
709}
710