MCELFStreamer.cpp revision dce4a407a24b04eebc6a376f8e62b41aaa7b071f 
1//===- lib/MC/MCELFStreamer.cpp - ELF Object Output -----------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file assembles .s files and emits ELF .o object files.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/MC/MCELFStreamer.h"
15#include "llvm/ADT/STLExtras.h"
16#include "llvm/ADT/SmallPtrSet.h"
17#include "llvm/MC/MCAsmBackend.h"
18#include "llvm/MC/MCAssembler.h"
19#include "llvm/MC/MCCodeEmitter.h"
20#include "llvm/MC/MCContext.h"
21#include "llvm/MC/MCELF.h"
22#include "llvm/MC/MCELFSymbolFlags.h"
23#include "llvm/MC/MCExpr.h"
24#include "llvm/MC/MCInst.h"
25#include "llvm/MC/MCObjectFileInfo.h"
26#include "llvm/MC/MCObjectStreamer.h"
27#include "llvm/MC/MCSection.h"
28#include "llvm/MC/MCSectionELF.h"
29#include "llvm/MC/MCSymbol.h"
30#include "llvm/MC/MCValue.h"
31#include "llvm/Support/Debug.h"
32#include "llvm/Support/ELF.h"
33#include "llvm/Support/ErrorHandling.h"
34#include "llvm/Support/raw_ostream.h"
35
36using namespace llvm;
37
38MCELFStreamer::~MCELFStreamer() {
39}
40
41void MCELFStreamer::InitSections() {
42  // This emulates the same behavior of GNU as. This makes it easier
43  // to compare the output as the major sections are in the same order.
44  SwitchSection(getContext().getObjectFileInfo()->getTextSection());
45  EmitCodeAlignment(4);
46
47  SwitchSection(getContext().getObjectFileInfo()->getDataSection());
48  EmitCodeAlignment(4);
49
50  SwitchSection(getContext().getObjectFileInfo()->getBSSSection());
51  EmitCodeAlignment(4);
52
53  SwitchSection(getContext().getObjectFileInfo()->getTextSection());
54}
55
56void MCELFStreamer::EmitLabel(MCSymbol *Symbol) {
57  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
58
59  MCObjectStreamer::EmitLabel(Symbol);
60
61  const MCSectionELF &Section =
62    static_cast<const MCSectionELF&>(Symbol->getSection());
63  MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
64  if (Section.getFlags() & ELF::SHF_TLS)
65    MCELF::SetType(SD, ELF::STT_TLS);
66}
67
68void MCELFStreamer::EmitDebugLabel(MCSymbol *Symbol) {
69  EmitLabel(Symbol);
70}
71
72void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
73  // Let the target do whatever target specific stuff it needs to do.
74  getAssembler().getBackend().handleAssemblerFlag(Flag);
75  // Do any generic stuff we need to do.
76  switch (Flag) {
77  case MCAF_SyntaxUnified: return; // no-op here.
78  case MCAF_Code16: return; // Change parsing mode; no-op here.
79  case MCAF_Code32: return; // Change parsing mode; no-op here.
80  case MCAF_Code64: return; // Change parsing mode; no-op here.
81  case MCAF_SubsectionsViaSymbols:
82    getAssembler().setSubsectionsViaSymbols(true);
83    return;
84  }
85
86  llvm_unreachable("invalid assembler flag!");
87}
88
89void MCELFStreamer::ChangeSection(const MCSection *Section,
90                                  const MCExpr *Subsection) {
91  MCSectionData *CurSection = getCurrentSectionData();
92  if (CurSection && CurSection->isBundleLocked())
93    report_fatal_error("Unterminated .bundle_lock when changing a section");
94  const MCSymbol *Grp = static_cast<const MCSectionELF *>(Section)->getGroup();
95  if (Grp)
96    getAssembler().getOrCreateSymbolData(*Grp);
97  this->MCObjectStreamer::ChangeSection(Section, Subsection);
98}
99
100void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
101  getAssembler().getOrCreateSymbolData(*Symbol);
102  const MCExpr *Value = MCSymbolRefExpr::Create(
103      Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext());
104  Alias->setVariableValue(Value);
105}
106
107// When GNU as encounters more than one .type declaration for an object it seems
108// to use a mechanism similar to the one below to decide which type is actually
109// used in the object file.  The greater of T1 and T2 is selected based on the
110// following ordering:
111//  STT_NOTYPE < STT_OBJECT < STT_FUNC < STT_GNU_IFUNC < STT_TLS < anything else
112// If neither T1 < T2 nor T2 < T1 according to this ordering, use T2 (the user
113// provided type).
114static unsigned CombineSymbolTypes(unsigned T1, unsigned T2) {
115  unsigned TypeOrdering[] = {ELF::STT_NOTYPE, ELF::STT_OBJECT, ELF::STT_FUNC,
116                             ELF::STT_GNU_IFUNC, ELF::STT_TLS};
117  for (unsigned i = 0; i != array_lengthof(TypeOrdering); ++i) {
118    if (T1 == TypeOrdering[i])
119      return T2;
120    if (T2 == TypeOrdering[i])
121      return T1;
122  }
123
124  return T2;
125}
126
127bool MCELFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
128                                        MCSymbolAttr Attribute) {
129  // Indirect symbols are handled differently, to match how 'as' handles
130  // them. This makes writing matching .o files easier.
131  if (Attribute == MCSA_IndirectSymbol) {
132    // Note that we intentionally cannot use the symbol data here; this is
133    // important for matching the string table that 'as' generates.
134    IndirectSymbolData ISD;
135    ISD.Symbol = Symbol;
136    ISD.SectionData = getCurrentSectionData();
137    getAssembler().getIndirectSymbols().push_back(ISD);
138    return true;
139  }
140
141  // Adding a symbol attribute always introduces the symbol, note that an
142  // important side effect of calling getOrCreateSymbolData here is to register
143  // the symbol with the assembler.
144  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
145
146  // The implementation of symbol attributes is designed to match 'as', but it
147  // leaves much to desired. It doesn't really make sense to arbitrarily add and
148  // remove flags, but 'as' allows this (in particular, see .desc).
149  //
150  // In the future it might be worth trying to make these operations more well
151  // defined.
152  switch (Attribute) {
153  case MCSA_LazyReference:
154  case MCSA_Reference:
155  case MCSA_SymbolResolver:
156  case MCSA_PrivateExtern:
157  case MCSA_WeakDefinition:
158  case MCSA_WeakDefAutoPrivate:
159  case MCSA_Invalid:
160  case MCSA_IndirectSymbol:
161    return false;
162
163  case MCSA_NoDeadStrip:
164  case MCSA_ELF_TypeGnuUniqueObject:
165    // Ignore for now.
166    break;
167
168  case MCSA_Global:
169    MCELF::SetBinding(SD, ELF::STB_GLOBAL);
170    SD.setExternal(true);
171    BindingExplicitlySet.insert(Symbol);
172    break;
173
174  case MCSA_WeakReference:
175  case MCSA_Weak:
176    MCELF::SetBinding(SD, ELF::STB_WEAK);
177    SD.setExternal(true);
178    BindingExplicitlySet.insert(Symbol);
179    break;
180
181  case MCSA_Local:
182    MCELF::SetBinding(SD, ELF::STB_LOCAL);
183    SD.setExternal(false);
184    BindingExplicitlySet.insert(Symbol);
185    break;
186
187  case MCSA_ELF_TypeFunction:
188    MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
189                                          ELF::STT_FUNC));
190    break;
191
192  case MCSA_ELF_TypeIndFunction:
193    MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
194                                          ELF::STT_GNU_IFUNC));
195    break;
196
197  case MCSA_ELF_TypeObject:
198    MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
199                                          ELF::STT_OBJECT));
200    break;
201
202  case MCSA_ELF_TypeTLS:
203    MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
204                                          ELF::STT_TLS));
205    break;
206
207  case MCSA_ELF_TypeCommon:
208    // TODO: Emit these as a common symbol.
209    MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
210                                          ELF::STT_OBJECT));
211    break;
212
213  case MCSA_ELF_TypeNoType:
214    MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
215                                          ELF::STT_NOTYPE));
216    break;
217
218  case MCSA_Protected:
219    MCELF::SetVisibility(SD, ELF::STV_PROTECTED);
220    break;
221
222  case MCSA_Hidden:
223    MCELF::SetVisibility(SD, ELF::STV_HIDDEN);
224    break;
225
226  case MCSA_Internal:
227    MCELF::SetVisibility(SD, ELF::STV_INTERNAL);
228    break;
229  }
230
231  return true;
232}
233
234void MCELFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
235                                       unsigned ByteAlignment) {
236  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
237
238  if (!BindingExplicitlySet.count(Symbol)) {
239    MCELF::SetBinding(SD, ELF::STB_GLOBAL);
240    SD.setExternal(true);
241  }
242
243  MCELF::SetType(SD, ELF::STT_OBJECT);
244
245  if (MCELF::GetBinding(SD) == ELF_STB_Local) {
246    const MCSection *Section = getAssembler().getContext().getELFSection(".bss",
247                                                         ELF::SHT_NOBITS,
248                                                         ELF::SHF_WRITE |
249                                                         ELF::SHF_ALLOC,
250                                                         SectionKind::getBSS());
251
252    AssignSection(Symbol, Section);
253
254    struct LocalCommon L = {&SD, Size, ByteAlignment};
255    LocalCommons.push_back(L);
256  } else {
257    SD.setCommon(Size, ByteAlignment);
258  }
259
260  SD.setSize(MCConstantExpr::Create(Size, getContext()));
261}
262
263void MCELFStreamer::EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
264  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
265  SD.setSize(Value);
266}
267
268void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
269                                          unsigned ByteAlignment) {
270  // FIXME: Should this be caught and done earlier?
271  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
272  MCELF::SetBinding(SD, ELF::STB_LOCAL);
273  SD.setExternal(false);
274  BindingExplicitlySet.insert(Symbol);
275  EmitCommonSymbol(Symbol, Size, ByteAlignment);
276}
277
278void MCELFStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
279                                  const SMLoc &Loc) {
280  if (getCurrentSectionData()->isBundleLocked())
281    report_fatal_error("Emitting values inside a locked bundle is forbidden");
282  fixSymbolsInTLSFixups(Value);
283  MCObjectStreamer::EmitValueImpl(Value, Size, Loc);
284}
285
286void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
287                                         int64_t Value,
288                                         unsigned ValueSize,
289                                         unsigned MaxBytesToEmit) {
290  if (getCurrentSectionData()->isBundleLocked())
291    report_fatal_error("Emitting values inside a locked bundle is forbidden");
292  MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value,
293                                         ValueSize, MaxBytesToEmit);
294}
295
296// Add a symbol for the file name of this module. They start after the
297// null symbol and don't count as normal symbol, i.e. a non-STT_FILE symbol
298// with the same name may appear.
299void MCELFStreamer::EmitFileDirective(StringRef Filename) {
300  getAssembler().addFileName(Filename);
301}
302
303void MCELFStreamer::EmitIdent(StringRef IdentString) {
304  const MCSection *Comment = getAssembler().getContext().getELFSection(
305      ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS,
306      SectionKind::getReadOnly(), 1, "");
307  PushSection();
308  SwitchSection(Comment);
309  if (!SeenIdent) {
310    EmitIntValue(0, 1);
311    SeenIdent = true;
312  }
313  EmitBytes(IdentString);
314  EmitIntValue(0, 1);
315  PopSection();
316}
317
318void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
319  switch (expr->getKind()) {
320  case MCExpr::Target:
321    cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
322    break;
323  case MCExpr::Constant:
324    break;
325
326  case MCExpr::Binary: {
327    const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
328    fixSymbolsInTLSFixups(be->getLHS());
329    fixSymbolsInTLSFixups(be->getRHS());
330    break;
331  }
332
333  case MCExpr::SymbolRef: {
334    const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
335    switch (symRef.getKind()) {
336    default:
337      return;
338    case MCSymbolRefExpr::VK_GOTTPOFF:
339    case MCSymbolRefExpr::VK_INDNTPOFF:
340    case MCSymbolRefExpr::VK_NTPOFF:
341    case MCSymbolRefExpr::VK_GOTNTPOFF:
342    case MCSymbolRefExpr::VK_TLSGD:
343    case MCSymbolRefExpr::VK_TLSLD:
344    case MCSymbolRefExpr::VK_TLSLDM:
345    case MCSymbolRefExpr::VK_TPOFF:
346    case MCSymbolRefExpr::VK_DTPOFF:
347    case MCSymbolRefExpr::VK_Mips_TLSGD:
348    case MCSymbolRefExpr::VK_Mips_GOTTPREL:
349    case MCSymbolRefExpr::VK_Mips_TPREL_HI:
350    case MCSymbolRefExpr::VK_Mips_TPREL_LO:
351    case MCSymbolRefExpr::VK_PPC_DTPMOD:
352    case MCSymbolRefExpr::VK_PPC_TPREL:
353    case MCSymbolRefExpr::VK_PPC_TPREL_LO:
354    case MCSymbolRefExpr::VK_PPC_TPREL_HI:
355    case MCSymbolRefExpr::VK_PPC_TPREL_HA:
356    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
357    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
358    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
359    case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
360    case MCSymbolRefExpr::VK_PPC_DTPREL:
361    case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
362    case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
363    case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
364    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
365    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
366    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
367    case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
368    case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
369    case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
370    case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
371    case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
372    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
373    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
374    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
375    case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
376    case MCSymbolRefExpr::VK_PPC_TLS:
377    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
378    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
379    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
380    case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
381    case MCSymbolRefExpr::VK_PPC_TLSGD:
382    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
383    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
384    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
385    case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
386    case MCSymbolRefExpr::VK_PPC_TLSLD:
387      break;
388    }
389    MCSymbolData &SD = getAssembler().getOrCreateSymbolData(symRef.getSymbol());
390    MCELF::SetType(SD, ELF::STT_TLS);
391    break;
392  }
393
394  case MCExpr::Unary:
395    fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
396    break;
397  }
398}
399
400void MCELFStreamer::EmitInstToFragment(const MCInst &Inst,
401                                       const MCSubtargetInfo &STI) {
402  this->MCObjectStreamer::EmitInstToFragment(Inst, STI);
403  MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
404
405  for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
406    fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
407}
408
409void MCELFStreamer::EmitInstToData(const MCInst &Inst,
410                                   const MCSubtargetInfo &STI) {
411  MCAssembler &Assembler = getAssembler();
412  SmallVector<MCFixup, 4> Fixups;
413  SmallString<256> Code;
414  raw_svector_ostream VecOS(Code);
415  Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups, STI);
416  VecOS.flush();
417
418  for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
419    fixSymbolsInTLSFixups(Fixups[i].getValue());
420
421  // There are several possibilities here:
422  //
423  // If bundling is disabled, append the encoded instruction to the current data
424  // fragment (or create a new such fragment if the current fragment is not a
425  // data fragment).
426  //
427  // If bundling is enabled:
428  // - If we're not in a bundle-locked group, emit the instruction into a
429  //   fragment of its own. If there are no fixups registered for the
430  //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
431  //   MCDataFragment.
432  // - If we're in a bundle-locked group, append the instruction to the current
433  //   data fragment because we want all the instructions in a group to get into
434  //   the same fragment. Be careful not to do that for the first instruction in
435  //   the group, though.
436  MCDataFragment *DF;
437
438  if (Assembler.isBundlingEnabled()) {
439    MCSectionData *SD = getCurrentSectionData();
440    if (SD->isBundleLocked() && !SD->isBundleGroupBeforeFirstInst())
441      // If we are bundle-locked, we re-use the current fragment.
442      // The bundle-locking directive ensures this is a new data fragment.
443      DF = cast<MCDataFragment>(getCurrentFragment());
444    else if (!SD->isBundleLocked() && Fixups.size() == 0) {
445      // Optimize memory usage by emitting the instruction to a
446      // MCCompactEncodedInstFragment when not in a bundle-locked group and
447      // there are no fixups registered.
448      MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
449      insert(CEIF);
450      CEIF->getContents().append(Code.begin(), Code.end());
451      return;
452    } else {
453      DF = new MCDataFragment();
454      insert(DF);
455      if (SD->getBundleLockState() == MCSectionData::BundleLockedAlignToEnd) {
456        // If this is a new fragment created for a bundle-locked group, and the
457        // group was marked as "align_to_end", set a flag in the fragment.
458        DF->setAlignToBundleEnd(true);
459      }
460    }
461
462    // We're now emitting an instruction in a bundle group, so this flag has
463    // to be turned off.
464    SD->setBundleGroupBeforeFirstInst(false);
465  } else {
466    DF = getOrCreateDataFragment();
467  }
468
469  // Add the fixups and data.
470  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
471    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
472    DF->getFixups().push_back(Fixups[i]);
473  }
474  DF->setHasInstructions(true);
475  DF->getContents().append(Code.begin(), Code.end());
476}
477
478void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
479  assert(AlignPow2 <= 30 && "Invalid bundle alignment");
480  MCAssembler &Assembler = getAssembler();
481  if (Assembler.getBundleAlignSize() == 0 && AlignPow2 > 0)
482    Assembler.setBundleAlignSize(1 << AlignPow2);
483  else
484    report_fatal_error(".bundle_align_mode should be only set once per file");
485}
486
487void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
488  MCSectionData *SD = getCurrentSectionData();
489
490  // Sanity checks
491  //
492  if (!getAssembler().isBundlingEnabled())
493    report_fatal_error(".bundle_lock forbidden when bundling is disabled");
494  else if (SD->isBundleLocked())
495    report_fatal_error("Nesting of .bundle_lock is forbidden");
496
497  SD->setBundleLockState(AlignToEnd ? MCSectionData::BundleLockedAlignToEnd :
498                                      MCSectionData::BundleLocked);
499  SD->setBundleGroupBeforeFirstInst(true);
500}
501
502void MCELFStreamer::EmitBundleUnlock() {
503  MCSectionData *SD = getCurrentSectionData();
504
505  // Sanity checks
506  if (!getAssembler().isBundlingEnabled())
507    report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
508  else if (!SD->isBundleLocked())
509    report_fatal_error(".bundle_unlock without matching lock");
510  else if (SD->isBundleGroupBeforeFirstInst())
511    report_fatal_error("Empty bundle-locked group is forbidden");
512
513  SD->setBundleLockState(MCSectionData::NotBundleLocked);
514}
515
516void MCELFStreamer::Flush() {
517  for (std::vector<LocalCommon>::const_iterator i = LocalCommons.begin(),
518                                                e = LocalCommons.end();
519       i != e; ++i) {
520    MCSymbolData *SD = i->SD;
521    uint64_t Size = i->Size;
522    unsigned ByteAlignment = i->ByteAlignment;
523    const MCSymbol &Symbol = SD->getSymbol();
524    const MCSection &Section = Symbol.getSection();
525
526    MCSectionData &SectData = getAssembler().getOrCreateSectionData(Section);
527    new MCAlignFragment(ByteAlignment, 0, 1, ByteAlignment, &SectData);
528
529    MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
530    SD->setFragment(F);
531
532    // Update the maximum alignment of the section if necessary.
533    if (ByteAlignment > SectData.getAlignment())
534      SectData.setAlignment(ByteAlignment);
535  }
536
537  LocalCommons.clear();
538}
539
540void MCELFStreamer::FinishImpl() {
541  EmitFrames(nullptr);
542
543  Flush();
544
545  this->MCObjectStreamer::FinishImpl();
546}
547
548MCStreamer *llvm::createELFStreamer(MCContext &Context, MCAsmBackend &MAB,
549                                    raw_ostream &OS, MCCodeEmitter *CE,
550                                    bool RelaxAll, bool NoExecStack) {
551  MCELFStreamer *S = new MCELFStreamer(Context, MAB, OS, CE);
552  if (RelaxAll)
553    S->getAssembler().setRelaxAll(true);
554  if (NoExecStack)
555    S->getAssembler().setNoExecStack(true);
556  return S;
557}
558
559void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
560  llvm_unreachable("Generic ELF doesn't support this directive");
561}
562
563void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
564  llvm_unreachable("ELF doesn't support this directive");
565}
566
567void MCELFStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
568  llvm_unreachable("ELF doesn't support this directive");
569}
570
571void MCELFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
572  llvm_unreachable("ELF doesn't support this directive");
573}
574
575void MCELFStreamer::EmitCOFFSymbolType(int Type) {
576  llvm_unreachable("ELF doesn't support this directive");
577}
578
579void MCELFStreamer::EndCOFFSymbolDef() {
580  llvm_unreachable("ELF doesn't support this directive");
581}
582
583void MCELFStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
584                                 uint64_t Size, unsigned ByteAlignment) {
585  llvm_unreachable("ELF doesn't support this directive");
586}
587
588void MCELFStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
589                                   uint64_t Size, unsigned ByteAlignment) {
590  llvm_unreachable("ELF doesn't support this directive");
591}
592