MCELFStreamer.cpp revision ba210243ef7d325ef6954d459091edf580a241f9 
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/MCStreamer.h"
15
16#include "llvm/ADT/SmallPtrSet.h"
17#include "llvm/MC/MCAssembler.h"
18#include "llvm/MC/MCContext.h"
19#include "llvm/MC/MCCodeEmitter.h"
20#include "llvm/MC/MCELFSymbolFlags.h"
21#include "llvm/MC/MCExpr.h"
22#include "llvm/MC/MCInst.h"
23#include "llvm/MC/MCObjectStreamer.h"
24#include "llvm/MC/MCSection.h"
25#include "llvm/MC/MCSectionELF.h"
26#include "llvm/MC/MCSymbol.h"
27#include "llvm/MC/MCValue.h"
28#include "llvm/Support/Debug.h"
29#include "llvm/Support/ELF.h"
30#include "llvm/Support/ErrorHandling.h"
31#include "llvm/Support/raw_ostream.h"
32#include "llvm/Target/TargetAsmBackend.h"
33
34using namespace llvm;
35
36namespace {
37
38static void SetBinding(MCSymbolData &SD, unsigned Binding) {
39  assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
40         Binding == ELF::STB_WEAK);
41  uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STB_Shift);
42  SD.setFlags(OtherFlags | (Binding << ELF_STB_Shift));
43}
44
45static unsigned GetBinding(const MCSymbolData &SD) {
46  uint32_t Binding = (SD.getFlags() & (0xf << ELF_STB_Shift)) >> ELF_STB_Shift;
47  assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
48         Binding == ELF::STB_WEAK);
49  return Binding;
50}
51
52static void SetType(MCSymbolData &SD, unsigned Type) {
53  assert(Type == ELF::STT_NOTYPE || Type == ELF::STT_OBJECT ||
54         Type == ELF::STT_FUNC || Type == ELF::STT_SECTION ||
55         Type == ELF::STT_FILE || Type == ELF::STT_COMMON ||
56         Type == ELF::STT_TLS);
57
58  uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STT_Shift);
59  SD.setFlags(OtherFlags | (Type << ELF_STT_Shift));
60}
61
62static void SetVisibility(MCSymbolData &SD, unsigned Visibility) {
63  assert(Visibility == ELF::STV_DEFAULT || Visibility == ELF::STV_INTERNAL ||
64         Visibility == ELF::STV_HIDDEN || Visibility == ELF::STV_PROTECTED);
65
66  uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STV_Shift);
67  SD.setFlags(OtherFlags | (Visibility << ELF_STV_Shift));
68}
69
70class MCELFStreamer : public MCObjectStreamer {
71public:
72  MCELFStreamer(MCContext &Context, TargetAsmBackend &TAB,
73                  raw_ostream &OS, MCCodeEmitter *Emitter)
74    : MCObjectStreamer(Context, TAB, OS, Emitter, false) {}
75
76  ~MCELFStreamer() {}
77
78  /// @name MCStreamer Interface
79  /// @{
80
81  virtual void InitSections();
82  virtual void EmitLabel(MCSymbol *Symbol);
83  virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
84  virtual void EmitThumbFunc(MCSymbol *Func);
85  virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
86  virtual void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol);
87  virtual void SwitchSection(const MCSection *Section);
88  virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
89  virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
90    assert(0 && "ELF doesn't support this directive");
91  }
92  virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
93                                unsigned ByteAlignment);
94  virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
95    assert(0 && "ELF doesn't support this directive");
96  }
97
98  virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
99    assert(0 && "ELF doesn't support this directive");
100  }
101
102  virtual void EmitCOFFSymbolType(int Type) {
103    assert(0 && "ELF doesn't support this directive");
104  }
105
106  virtual void EndCOFFSymbolDef() {
107    assert(0 && "ELF doesn't support this directive");
108  }
109
110  virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
111     MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
112     SD.setSize(Value);
113  }
114
115  virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
116    assert(0 && "ELF doesn't support this directive");
117  }
118  virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
119                            unsigned Size = 0, unsigned ByteAlignment = 0) {
120    assert(0 && "ELF doesn't support this directive");
121  }
122  virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
123                              uint64_t Size, unsigned ByteAlignment = 0) {
124    assert(0 && "ELF doesn't support this directive");
125  }
126  virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
127  virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);
128  virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
129                                    unsigned ValueSize = 1,
130                                    unsigned MaxBytesToEmit = 0);
131  virtual void EmitCodeAlignment(unsigned ByteAlignment,
132                                 unsigned MaxBytesToEmit = 0);
133  virtual void EmitValueToOffset(const MCExpr *Offset,
134                                 unsigned char Value = 0);
135
136  virtual void EmitFileDirective(StringRef Filename);
137
138  virtual void Finish();
139
140private:
141  virtual void EmitInstToFragment(const MCInst &Inst);
142  virtual void EmitInstToData(const MCInst &Inst);
143
144  void fixSymbolsInTLSFixups(const MCExpr *expr);
145
146  struct LocalCommon {
147    MCSymbolData *SD;
148    uint64_t Size;
149    unsigned ByteAlignment;
150  };
151  std::vector<LocalCommon> LocalCommons;
152
153  SmallPtrSet<MCSymbol *, 16> BindingExplicitlySet;
154  /// @}
155  void SetSection(StringRef Section, unsigned Type, unsigned Flags,
156                  SectionKind Kind) {
157    SwitchSection(getContext().getELFSection(Section, Type, Flags, Kind));
158  }
159
160  void SetSectionData() {
161    SetSection(".data", MCSectionELF::SHT_PROGBITS,
162               MCSectionELF::SHF_WRITE |MCSectionELF::SHF_ALLOC,
163               SectionKind::getDataRel());
164    EmitCodeAlignment(4, 0);
165  }
166  void SetSectionText() {
167    SetSection(".text", MCSectionELF::SHT_PROGBITS,
168               MCSectionELF::SHF_EXECINSTR |
169               MCSectionELF::SHF_ALLOC, SectionKind::getText());
170    EmitCodeAlignment(4, 0);
171  }
172  void SetSectionBss() {
173    SetSection(".bss", MCSectionELF::SHT_NOBITS,
174               MCSectionELF::SHF_WRITE |
175               MCSectionELF::SHF_ALLOC, SectionKind::getBSS());
176    EmitCodeAlignment(4, 0);
177  }
178};
179
180} // end anonymous namespace.
181
182void MCELFStreamer::InitSections() {
183  // This emulates the same behavior of GNU as. This makes it easier
184  // to compare the output as the major sections are in the same order.
185  SetSectionText();
186  SetSectionData();
187  SetSectionBss();
188  SetSectionText();
189}
190
191void MCELFStreamer::EmitLabel(MCSymbol *Symbol) {
192  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
193
194  Symbol->setSection(*CurSection);
195
196  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
197
198  const MCSectionELF &Section =
199    static_cast<const MCSectionELF&>(Symbol->getSection());
200  if (Section.getFlags() & MCSectionELF::SHF_TLS)
201    SetType(SD, ELF::STT_TLS);
202
203  // FIXME: This is wasteful, we don't necessarily need to create a data
204  // fragment. Instead, we should mark the symbol as pointing into the data
205  // fragment if it exists, otherwise we should just queue the label and set its
206  // fragment pointer when we emit the next fragment.
207  MCDataFragment *F = getOrCreateDataFragment();
208
209  assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
210  SD.setFragment(F);
211  SD.setOffset(F->getContents().size());
212}
213
214void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
215  switch (Flag) {
216  case MCAF_SyntaxUnified: return; // no-op here.
217  case MCAF_Code16: return; // no-op here.
218  case MCAF_Code32: return; // no-op here.
219  case MCAF_SubsectionsViaSymbols:
220    getAssembler().setSubsectionsViaSymbols(true);
221    return;
222  }
223
224  assert(0 && "invalid assembler flag!");
225}
226
227void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
228  // FIXME: Anything needed here to flag the function as thumb?
229}
230
231void MCELFStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
232  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
233  // MCObjectStreamer.
234  // FIXME: Lift context changes into super class.
235  getAssembler().getOrCreateSymbolData(*Symbol);
236  Symbol->setVariableValue(AddValueSymbols(Value));
237}
238
239void MCELFStreamer::SwitchSection(const MCSection *Section) {
240  const MCSymbol *Grp = static_cast<const MCSectionELF *>(Section)->getGroup();
241  if (Grp)
242    getAssembler().getOrCreateSymbolData(*Grp);
243  this->MCObjectStreamer::SwitchSection(Section);
244}
245
246void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
247  getAssembler().getOrCreateSymbolData(*Symbol);
248  MCSymbolData &AliasSD = getAssembler().getOrCreateSymbolData(*Alias);
249  AliasSD.setFlags(AliasSD.getFlags() | ELF_Other_Weakref);
250  const MCExpr *Value = MCSymbolRefExpr::Create(Symbol, getContext());
251  Alias->setVariableValue(Value);
252}
253
254void MCELFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
255                                          MCSymbolAttr Attribute) {
256  // Indirect symbols are handled differently, to match how 'as' handles
257  // them. This makes writing matching .o files easier.
258  if (Attribute == MCSA_IndirectSymbol) {
259    // Note that we intentionally cannot use the symbol data here; this is
260    // important for matching the string table that 'as' generates.
261    IndirectSymbolData ISD;
262    ISD.Symbol = Symbol;
263    ISD.SectionData = getCurrentSectionData();
264    getAssembler().getIndirectSymbols().push_back(ISD);
265    return;
266  }
267
268  // Adding a symbol attribute always introduces the symbol, note that an
269  // important side effect of calling getOrCreateSymbolData here is to register
270  // the symbol with the assembler.
271  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
272
273  // The implementation of symbol attributes is designed to match 'as', but it
274  // leaves much to desired. It doesn't really make sense to arbitrarily add and
275  // remove flags, but 'as' allows this (in particular, see .desc).
276  //
277  // In the future it might be worth trying to make these operations more well
278  // defined.
279  switch (Attribute) {
280  case MCSA_LazyReference:
281  case MCSA_Reference:
282  case MCSA_NoDeadStrip:
283  case MCSA_SymbolResolver:
284  case MCSA_PrivateExtern:
285  case MCSA_WeakDefinition:
286  case MCSA_WeakDefAutoPrivate:
287  case MCSA_Invalid:
288  case MCSA_ELF_TypeIndFunction:
289  case MCSA_IndirectSymbol:
290    assert(0 && "Invalid symbol attribute for ELF!");
291    break;
292
293  case MCSA_ELF_TypeGnuUniqueObject:
294    // Ignore for now.
295    break;
296
297  case MCSA_Global:
298    SetBinding(SD, ELF::STB_GLOBAL);
299    SD.setExternal(true);
300    BindingExplicitlySet.insert(Symbol);
301    break;
302
303  case MCSA_WeakReference:
304  case MCSA_Weak:
305    SetBinding(SD, ELF::STB_WEAK);
306    SD.setExternal(true);
307    BindingExplicitlySet.insert(Symbol);
308    break;
309
310  case MCSA_Local:
311    SetBinding(SD, ELF::STB_LOCAL);
312    SD.setExternal(false);
313    BindingExplicitlySet.insert(Symbol);
314    break;
315
316  case MCSA_ELF_TypeFunction:
317    SetType(SD, ELF::STT_FUNC);
318    break;
319
320  case MCSA_ELF_TypeObject:
321    SetType(SD, ELF::STT_OBJECT);
322    break;
323
324  case MCSA_ELF_TypeTLS:
325    SetType(SD, ELF::STT_TLS);
326    break;
327
328  case MCSA_ELF_TypeCommon:
329    SetType(SD, ELF::STT_COMMON);
330    break;
331
332  case MCSA_ELF_TypeNoType:
333    SetType(SD, ELF::STT_NOTYPE);
334    break;
335
336  case MCSA_Protected:
337    SetVisibility(SD, ELF::STV_PROTECTED);
338    break;
339
340  case MCSA_Hidden:
341    SetVisibility(SD, ELF::STV_HIDDEN);
342    break;
343
344  case MCSA_Internal:
345    SetVisibility(SD, ELF::STV_INTERNAL);
346    break;
347  }
348}
349
350void MCELFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
351                                       unsigned ByteAlignment) {
352  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
353
354  if (!BindingExplicitlySet.count(Symbol)) {
355    SetBinding(SD, ELF::STB_GLOBAL);
356    SD.setExternal(true);
357  }
358
359  SetType(SD, ELF::STT_OBJECT);
360
361  if (GetBinding(SD) == ELF_STB_Local) {
362    const MCSection *Section = getAssembler().getContext().getELFSection(".bss",
363                                                                    MCSectionELF::SHT_NOBITS,
364                                                                    MCSectionELF::SHF_WRITE |
365                                                                    MCSectionELF::SHF_ALLOC,
366                                                                    SectionKind::getBSS());
367    Symbol->setSection(*Section);
368
369    struct LocalCommon L = {&SD, Size, ByteAlignment};
370    LocalCommons.push_back(L);
371  } else {
372    SD.setCommon(Size, ByteAlignment);
373  }
374
375  SD.setSize(MCConstantExpr::Create(Size, getContext()));
376}
377
378void MCELFStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
379  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
380  // MCObjectStreamer.
381  getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
382}
383
384void MCELFStreamer::EmitValue(const MCExpr *Value, unsigned Size,
385                                unsigned AddrSpace) {
386  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
387  // MCObjectStreamer.
388  MCDataFragment *DF = getOrCreateDataFragment();
389
390  // Avoid fixups when possible.
391  int64_t AbsValue;
392  if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
393    // FIXME: Endianness assumption.
394    for (unsigned i = 0; i != Size; ++i)
395      DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
396  } else {
397    DF->addFixup(MCFixup::Create(DF->getContents().size(), AddValueSymbols(Value),
398                                 MCFixup::getKindForSize(Size, false)));
399    DF->getContents().resize(DF->getContents().size() + Size, 0);
400  }
401}
402
403void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
404                                           int64_t Value, unsigned ValueSize,
405                                           unsigned MaxBytesToEmit) {
406  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
407  // MCObjectStreamer.
408  if (MaxBytesToEmit == 0)
409    MaxBytesToEmit = ByteAlignment;
410  new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
411                      getCurrentSectionData());
412
413  // Update the maximum alignment on the current section if necessary.
414  if (ByteAlignment > getCurrentSectionData()->getAlignment())
415    getCurrentSectionData()->setAlignment(ByteAlignment);
416}
417
418void MCELFStreamer::EmitCodeAlignment(unsigned ByteAlignment,
419                                        unsigned MaxBytesToEmit) {
420  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
421  // MCObjectStreamer.
422  if (MaxBytesToEmit == 0)
423    MaxBytesToEmit = ByteAlignment;
424  MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
425                                           getCurrentSectionData());
426  F->setEmitNops(true);
427
428  // Update the maximum alignment on the current section if necessary.
429  if (ByteAlignment > getCurrentSectionData()->getAlignment())
430    getCurrentSectionData()->setAlignment(ByteAlignment);
431}
432
433void MCELFStreamer::EmitValueToOffset(const MCExpr *Offset,
434                                        unsigned char Value) {
435  // TODO: This is exactly the same as MCMachOStreamer. Consider merging into
436  // MCObjectStreamer.
437  new MCOrgFragment(*Offset, Value, getCurrentSectionData());
438}
439
440// Add a symbol for the file name of this module. This is the second
441// entry in the module's symbol table (the first being the null symbol).
442void MCELFStreamer::EmitFileDirective(StringRef Filename) {
443  MCSymbol *Symbol = getAssembler().getContext().GetOrCreateSymbol(Filename);
444  Symbol->setSection(*CurSection);
445  Symbol->setAbsolute();
446
447  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
448
449  SD.setFlags(ELF_STT_File | ELF_STB_Local | ELF_STV_Default);
450}
451
452void  MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
453  switch (expr->getKind()) {
454  case MCExpr::Target: llvm_unreachable("Can't handle target exprs yet!");
455  case MCExpr::Constant:
456    break;
457
458  case MCExpr::Binary: {
459    const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
460    fixSymbolsInTLSFixups(be->getLHS());
461    fixSymbolsInTLSFixups(be->getRHS());
462    break;
463  }
464
465  case MCExpr::SymbolRef: {
466    const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
467    switch (symRef.getKind()) {
468    default:
469      return;
470    case MCSymbolRefExpr::VK_NTPOFF:
471    case MCSymbolRefExpr::VK_GOTNTPOFF:
472    case MCSymbolRefExpr::VK_TLSGD:
473    case MCSymbolRefExpr::VK_TLSLDM:
474    case MCSymbolRefExpr::VK_TPOFF:
475    case MCSymbolRefExpr::VK_DTPOFF:
476    case MCSymbolRefExpr::VK_GOTTPOFF:
477    case MCSymbolRefExpr::VK_TLSLD:
478    case MCSymbolRefExpr::VK_ARM_TLSGD:
479      break;
480    }
481    MCSymbolData &SD = getAssembler().getOrCreateSymbolData(symRef.getSymbol());
482    SetType(SD, ELF::STT_TLS);
483    break;
484  }
485
486  case MCExpr::Unary:
487    fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
488    break;
489  }
490}
491
492void MCELFStreamer::EmitInstToFragment(const MCInst &Inst) {
493  MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
494
495  // Add the fixups and data.
496  //
497  // FIXME: Revisit this design decision when relaxation is done, we may be
498  // able to get away with not storing any extra data in the MCInst.
499  SmallVector<MCFixup, 4> Fixups;
500  SmallString<256> Code;
501  raw_svector_ostream VecOS(Code);
502  getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
503  VecOS.flush();
504
505  for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
506    fixSymbolsInTLSFixups(Fixups[i].getValue());
507
508  IF->getCode() = Code;
509  IF->getFixups() = Fixups;
510}
511
512void MCELFStreamer::EmitInstToData(const MCInst &Inst) {
513  MCDataFragment *DF = getOrCreateDataFragment();
514
515  SmallVector<MCFixup, 4> Fixups;
516  SmallString<256> Code;
517  raw_svector_ostream VecOS(Code);
518  getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
519  VecOS.flush();
520
521  for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
522    fixSymbolsInTLSFixups(Fixups[i].getValue());
523
524  // Add the fixups and data.
525  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
526    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
527    DF->addFixup(Fixups[i]);
528  }
529  DF->getContents().append(Code.begin(), Code.end());
530}
531
532void MCELFStreamer::Finish() {
533  // FIXME: duplicated code with the MachO streamer.
534  // Dump out the dwarf file & directory tables and line tables.
535  if (getContext().hasDwarfFiles()) {
536    const MCSection *DwarfLineSection =
537      getContext().getELFSection(".debug_line", 0, 0,
538                                 SectionKind::getDataRelLocal());
539    MCSectionData &DLS =
540      getAssembler().getOrCreateSectionData(*DwarfLineSection);
541    int PointerSize = getAssembler().getBackend().getPointerSize();
542    MCDwarfFileTable::Emit(this, DwarfLineSection, &DLS, PointerSize);
543  }
544
545  for (std::vector<LocalCommon>::const_iterator i = LocalCommons.begin(),
546                                                e = LocalCommons.end();
547       i != e; ++i) {
548    MCSymbolData *SD = i->SD;
549    uint64_t Size = i->Size;
550    unsigned ByteAlignment = i->ByteAlignment;
551    const MCSymbol &Symbol = SD->getSymbol();
552    const MCSection &Section = Symbol.getSection();
553
554    MCSectionData &SectData = getAssembler().getOrCreateSectionData(Section);
555    new MCAlignFragment(ByteAlignment, 0, 1, ByteAlignment, &SectData);
556
557    MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
558    SD->setFragment(F);
559
560    // Update the maximum alignment of the section if necessary.
561    if (ByteAlignment > SectData.getAlignment())
562      SectData.setAlignment(ByteAlignment);
563  }
564
565  this->MCObjectStreamer::Finish();
566}
567
568MCStreamer *llvm::createELFStreamer(MCContext &Context, TargetAsmBackend &TAB,
569                                      raw_ostream &OS, MCCodeEmitter *CE,
570                                      bool RelaxAll) {
571  MCELFStreamer *S = new MCELFStreamer(Context, TAB, OS, CE);
572  if (RelaxAll)
573    S->getAssembler().setRelaxAll(true);
574  return S;
575}
576