lib/MC/MCELFStreamer.cpp

   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
  34 using namespace llvm;
  35
  36 namespace {
  37
  38 static 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
  45 static 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
  52 static 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
  62 static 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
  70 class MCELFStreamer : public MCObjectStreamer {
  71 public:
  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 EmitGPRel32Value(const MCExpr *Value) {
 129     assert(0 && "ELF doesn't support this directive");
 130   }
 131   virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
 132                                     unsigned ValueSize = 1,
 133                                     unsigned MaxBytesToEmit = 0);
 134   virtual void EmitCodeAlignment(unsigned ByteAlignment,
 135                                  unsigned MaxBytesToEmit = 0);
 136   virtual void EmitValueToOffset(const MCExpr *Offset,
 137                                  unsigned char Value = 0);
 138
 139   virtual void EmitFileDirective(StringRef Filename);
 140
 141   virtual void Finish();
 142
 143 private:
 144   virtual void EmitInstToFragment(const MCInst &Inst);
 145   virtual void EmitInstToData(const MCInst &Inst);
 146
 147   void fixSymbolsInTLSFixups(const MCExpr *expr);
 148
 149   struct LocalCommon {
 150     MCSymbolData *SD;
 151     uint64_t Size;
 152     unsigned ByteAlignment;
 153   };
 154   std::vector<LocalCommon> LocalCommons;
 155
 156   SmallPtrSet<MCSymbol *, 16> BindingExplicitlySet;
 157   /// @}
 158   void SetSection(StringRef Section, unsigned Type, unsigned Flags,
 159                   SectionKind Kind) {
 160     SwitchSection(getContext().getELFSection(Section, Type, Flags, Kind));
 161   }
 162
 163   void SetSectionData() {
 164     SetSection(".data", MCSectionELF::SHT_PROGBITS,
 165                MCSectionELF::SHF_WRITE |MCSectionELF::SHF_ALLOC,
 166                SectionKind::getDataRel());
 167     EmitCodeAlignment(4, 0);
 168   }
 169   void SetSectionText() {
 170     SetSection(".text", MCSectionELF::SHT_PROGBITS,
 171                MCSectionELF::SHF_EXECINSTR |
 172                MCSectionELF::SHF_ALLOC, SectionKind::getText());
 173     EmitCodeAlignment(4, 0);
 174   }
 175   void SetSectionBss() {
 176     SetSection(".bss", MCSectionELF::SHT_NOBITS,
 177                MCSectionELF::SHF_WRITE |
 178                MCSectionELF::SHF_ALLOC, SectionKind::getBSS());
 179     EmitCodeAlignment(4, 0);
 180   }
 181 };
 182
 183 } // end anonymous namespace.
 184
 185 void MCELFStreamer::InitSections() {
 186   // This emulates the same behavior of GNU as. This makes it easier
 187   // to compare the output as the major sections are in the same order.
 188   SetSectionText();
 189   SetSectionData();
 190   SetSectionBss();
 191   SetSectionText();
 192 }
 193
 194 void MCELFStreamer::EmitLabel(MCSymbol *Symbol) {
 195   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 196
 197   Symbol->setSection(*CurSection);
 198
 199   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 200
 201   const MCSectionELF &Section =
 202     static_cast<const MCSectionELF&>(Symbol->getSection());
 203   if (Section.getFlags() & MCSectionELF::SHF_TLS)
 204     SetType(SD, ELF::STT_TLS);
 205
 206   // FIXME: This is wasteful, we don't necessarily need to create a data
 207   // fragment. Instead, we should mark the symbol as pointing into the data
 208   // fragment if it exists, otherwise we should just queue the label and set its
 209   // fragment pointer when we emit the next fragment.
 210   MCDataFragment *F = getOrCreateDataFragment();
 211
 212   assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
 213   SD.setFragment(F);
 214   SD.setOffset(F->getContents().size());
 215 }
 216
 217 void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
 218   switch (Flag) {
 219   case MCAF_SyntaxUnified: return; // no-op here.
 220   case MCAF_Code16: return; // no-op here.
 221   case MCAF_Code32: return; // no-op here.
 222   case MCAF_SubsectionsViaSymbols:
 223     getAssembler().setSubsectionsViaSymbols(true);
 224     return;
 225   }
 226
 227   assert(0 && "invalid assembler flag!");
 228 }
 229
 230 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
 231   // FIXME: Anything needed here to flag the function as thumb?
 232 }
 233
 234 void MCELFStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
 235   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 236   // MCObjectStreamer.
 237   // FIXME: Lift context changes into super class.
 238   getAssembler().getOrCreateSymbolData(*Symbol);
 239   Symbol->setVariableValue(AddValueSymbols(Value));
 240 }
 241
 242 void MCELFStreamer::SwitchSection(const MCSection *Section) {
 243   const MCSymbol *Grp = static_cast<const MCSectionELF *>(Section)->getGroup();
 244   if (Grp)
 245     getAssembler().getOrCreateSymbolData(*Grp);
 246   this->MCObjectStreamer::SwitchSection(Section);
 247 }
 248
 249 void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
 250   getAssembler().getOrCreateSymbolData(*Symbol);
 251   MCSymbolData &AliasSD = getAssembler().getOrCreateSymbolData(*Alias);
 252   AliasSD.setFlags(AliasSD.getFlags() | ELF_Other_Weakref);
 253   const MCExpr *Value = MCSymbolRefExpr::Create(Symbol, getContext());
 254   Alias->setVariableValue(Value);
 255 }
 256
 257 void MCELFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
 258                                           MCSymbolAttr Attribute) {
 259   // Indirect symbols are handled differently, to match how 'as' handles
 260   // them. This makes writing matching .o files easier.
 261   if (Attribute == MCSA_IndirectSymbol) {
 262     // Note that we intentionally cannot use the symbol data here; this is
 263     // important for matching the string table that 'as' generates.
 264     IndirectSymbolData ISD;
 265     ISD.Symbol = Symbol;
 266     ISD.SectionData = getCurrentSectionData();
 267     getAssembler().getIndirectSymbols().push_back(ISD);
 268     return;
 269   }
 270
 271   // Adding a symbol attribute always introduces the symbol, note that an
 272   // important side effect of calling getOrCreateSymbolData here is to register
 273   // the symbol with the assembler.
 274   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 275
 276   // The implementation of symbol attributes is designed to match 'as', but it
 277   // leaves much to desired. It doesn't really make sense to arbitrarily add and
 278   // remove flags, but 'as' allows this (in particular, see .desc).
 279   //
 280   // In the future it might be worth trying to make these operations more well
 281   // defined.
 282   switch (Attribute) {
 283   case MCSA_LazyReference:
 284   case MCSA_Reference:
 285   case MCSA_NoDeadStrip:
 286   case MCSA_SymbolResolver:
 287   case MCSA_PrivateExtern:
 288   case MCSA_WeakDefinition:
 289   case MCSA_WeakDefAutoPrivate:
 290   case MCSA_Invalid:
 291   case MCSA_ELF_TypeIndFunction:
 292   case MCSA_IndirectSymbol:
 293     assert(0 && "Invalid symbol attribute for ELF!");
 294     break;
 295
 296   case MCSA_ELF_TypeGnuUniqueObject:
 297     // Ignore for now.
 298     break;
 299
 300   case MCSA_Global:
 301     SetBinding(SD, ELF::STB_GLOBAL);
 302     SD.setExternal(true);
 303     BindingExplicitlySet.insert(Symbol);
 304     break;
 305
 306   case MCSA_WeakReference:
 307   case MCSA_Weak:
 308     SetBinding(SD, ELF::STB_WEAK);
 309     SD.setExternal(true);
 310     BindingExplicitlySet.insert(Symbol);
 311     break;
 312
 313   case MCSA_Local:
 314     SetBinding(SD, ELF::STB_LOCAL);
 315     SD.setExternal(false);
 316     BindingExplicitlySet.insert(Symbol);
 317     break;
 318
 319   case MCSA_ELF_TypeFunction:
 320     SetType(SD, ELF::STT_FUNC);
 321     break;
 322
 323   case MCSA_ELF_TypeObject:
 324     SetType(SD, ELF::STT_OBJECT);
 325     break;
 326
 327   case MCSA_ELF_TypeTLS:
 328     SetType(SD, ELF::STT_TLS);
 329     break;
 330
 331   case MCSA_ELF_TypeCommon:
 332     SetType(SD, ELF::STT_COMMON);
 333     break;
 334
 335   case MCSA_ELF_TypeNoType:
 336     SetType(SD, ELF::STT_NOTYPE);
 337     break;
 338
 339   case MCSA_Protected:
 340     SetVisibility(SD, ELF::STV_PROTECTED);
 341     break;
 342
 343   case MCSA_Hidden:
 344     SetVisibility(SD, ELF::STV_HIDDEN);
 345     break;
 346
 347   case MCSA_Internal:
 348     SetVisibility(SD, ELF::STV_INTERNAL);
 349     break;
 350   }
 351 }
 352
 353 void MCELFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
 354                                        unsigned ByteAlignment) {
 355   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 356
 357   if (!BindingExplicitlySet.count(Symbol)) {
 358     SetBinding(SD, ELF::STB_GLOBAL);
 359     SD.setExternal(true);
 360   }
 361
 362   SetType(SD, ELF::STT_OBJECT);
 363
 364   if (GetBinding(SD) == ELF_STB_Local) {
 365     const MCSection *Section = getAssembler().getContext().getELFSection(".bss",
 366                                                                     MCSectionELF::SHT_NOBITS,
 367                                                                     MCSectionELF::SHF_WRITE |
 368                                                                     MCSectionELF::SHF_ALLOC,
 369                                                                     SectionKind::getBSS());
 370     Symbol->setSection(*Section);
 371
 372     struct LocalCommon L = {&SD, Size, ByteAlignment};
 373     LocalCommons.push_back(L);
 374   } else {
 375     SD.setCommon(Size, ByteAlignment);
 376   }
 377
 378   SD.setSize(MCConstantExpr::Create(Size, getContext()));
 379 }
 380
 381 void MCELFStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
 382   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 383   // MCObjectStreamer.
 384   getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
 385 }
 386
 387 void MCELFStreamer::EmitValue(const MCExpr *Value, unsigned Size,
 388                                 unsigned AddrSpace) {
 389   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 390   // MCObjectStreamer.
 391   MCDataFragment *DF = getOrCreateDataFragment();
 392
 393   // Avoid fixups when possible.
 394   int64_t AbsValue;
 395   if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
 396     // FIXME: Endianness assumption.
 397     for (unsigned i = 0; i != Size; ++i)
 398       DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
 399   } else {
 400     DF->addFixup(MCFixup::Create(DF->getContents().size(), AddValueSymbols(Value),
 401                                  MCFixup::getKindForSize(Size)));
 402     DF->getContents().resize(DF->getContents().size() + Size, 0);
 403   }
 404 }
 405
 406 void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
 407                                            int64_t Value, unsigned ValueSize,
 408                                            unsigned MaxBytesToEmit) {
 409   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 410   // MCObjectStreamer.
 411   if (MaxBytesToEmit == 0)
 412     MaxBytesToEmit = ByteAlignment;
 413   new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
 414                       getCurrentSectionData());
 415
 416   // Update the maximum alignment on the current section if necessary.
 417   if (ByteAlignment > getCurrentSectionData()->getAlignment())
 418     getCurrentSectionData()->setAlignment(ByteAlignment);
 419 }
 420
 421 void MCELFStreamer::EmitCodeAlignment(unsigned ByteAlignment,
 422                                         unsigned MaxBytesToEmit) {
 423   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 424   // MCObjectStreamer.
 425   if (MaxBytesToEmit == 0)
 426     MaxBytesToEmit = ByteAlignment;
 427   MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
 428                                            getCurrentSectionData());
 429   F->setEmitNops(true);
 430
 431   // Update the maximum alignment on the current section if necessary.
 432   if (ByteAlignment > getCurrentSectionData()->getAlignment())
 433     getCurrentSectionData()->setAlignment(ByteAlignment);
 434 }
 435
 436 void MCELFStreamer::EmitValueToOffset(const MCExpr *Offset,
 437                                         unsigned char Value) {
 438   // TODO: This is exactly the same as MCMachOStreamer. Consider merging into
 439   // MCObjectStreamer.
 440   new MCOrgFragment(*Offset, Value, getCurrentSectionData());
 441 }
 442
 443 // Add a symbol for the file name of this module. This is the second
 444 // entry in the module's symbol table (the first being the null symbol).
 445 void MCELFStreamer::EmitFileDirective(StringRef Filename) {
 446   MCSymbol *Symbol = getAssembler().getContext().GetOrCreateSymbol(Filename);
 447   Symbol->setSection(*CurSection);
 448   Symbol->setAbsolute();
 449
 450   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 451
 452   SD.setFlags(ELF_STT_File | ELF_STB_Local | ELF_STV_Default);
 453 }
 454
 455 void  MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
 456   switch (expr->getKind()) {
 457   case MCExpr::Target: llvm_unreachable("Can't handle target exprs yet!");
 458   case MCExpr::Constant:
 459     break;
 460
 461   case MCExpr::Binary: {
 462     const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
 463     fixSymbolsInTLSFixups(be->getLHS());
 464     fixSymbolsInTLSFixups(be->getRHS());
 465     break;
 466   }
 467
 468   case MCExpr::SymbolRef: {
 469     const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
 470     switch (symRef.getKind()) {
 471     default:
 472       return;
 473     case MCSymbolRefExpr::VK_NTPOFF:
 474     case MCSymbolRefExpr::VK_GOTNTPOFF:
 475     case MCSymbolRefExpr::VK_TLSGD:
 476     case MCSymbolRefExpr::VK_TLSLDM:
 477     case MCSymbolRefExpr::VK_TPOFF:
 478     case MCSymbolRefExpr::VK_DTPOFF:
 479     case MCSymbolRefExpr::VK_GOTTPOFF:
 480     case MCSymbolRefExpr::VK_TLSLD:
 481     case MCSymbolRefExpr::VK_ARM_TLSGD:
 482       break;
 483     }
 484     MCSymbolData &SD = getAssembler().getOrCreateSymbolData(symRef.getSymbol());
 485     SetType(SD, ELF::STT_TLS);
 486     break;
 487   }
 488
 489   case MCExpr::Unary:
 490     fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
 491     break;
 492   }
 493 }
 494
 495 void MCELFStreamer::EmitInstToFragment(const MCInst &Inst) {
 496   MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
 497
 498   // Add the fixups and data.
 499   //
 500   // FIXME: Revisit this design decision when relaxation is done, we may be
 501   // able to get away with not storing any extra data in the MCInst.
 502   SmallVector<MCFixup, 4> Fixups;
 503   SmallString<256> Code;
 504   raw_svector_ostream VecOS(Code);
 505   getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
 506   VecOS.flush();
 507
 508   for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
 509     fixSymbolsInTLSFixups(Fixups[i].getValue());
 510
 511   IF->getCode() = Code;
 512   IF->getFixups() = Fixups;
 513 }
 514
 515 void MCELFStreamer::EmitInstToData(const MCInst &Inst) {
 516   MCDataFragment *DF = getOrCreateDataFragment();
 517
 518   SmallVector<MCFixup, 4> Fixups;
 519   SmallString<256> Code;
 520   raw_svector_ostream VecOS(Code);
 521   getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
 522   VecOS.flush();
 523
 524   for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
 525     fixSymbolsInTLSFixups(Fixups[i].getValue());
 526
 527   // Add the fixups and data.
 528   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
 529     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
 530     DF->addFixup(Fixups[i]);
 531   }
 532   DF->getContents().append(Code.begin(), Code.end());
 533 }
 534
 535 void MCELFStreamer::Finish() {
 536   // FIXME: duplicated code with the MachO streamer.
 537   // Dump out the dwarf file & directory tables and line tables.
 538   if (getContext().hasDwarfFiles()) {
 539     const MCSection *DwarfLineSection =
 540       getContext().getELFSection(".debug_line", 0, 0,
 541                                  SectionKind::getDataRelLocal());
 542     MCSectionData &DLS =
 543       getAssembler().getOrCreateSectionData(*DwarfLineSection);
 544     int PointerSize = getAssembler().getBackend().getPointerSize();
 545     MCDwarfFileTable::Emit(this, DwarfLineSection, &DLS, PointerSize);
 546   }
 547
 548   for (std::vector<LocalCommon>::const_iterator i = LocalCommons.begin(),
 549                                                 e = LocalCommons.end();
 550        i != e; ++i) {
 551     MCSymbolData *SD = i->SD;
 552     uint64_t Size = i->Size;
 553     unsigned ByteAlignment = i->ByteAlignment;
 554     const MCSymbol &Symbol = SD->getSymbol();
 555     const MCSection &Section = Symbol.getSection();
 556
 557     MCSectionData &SectData = getAssembler().getOrCreateSectionData(Section);
 558     new MCAlignFragment(ByteAlignment, 0, 1, ByteAlignment, &SectData);
 559
 560     MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
 561     SD->setFragment(F);
 562
 563     // Update the maximum alignment of the section if necessary.
 564     if (ByteAlignment > SectData.getAlignment())
 565       SectData.setAlignment(ByteAlignment);
 566   }
 567
 568   this->MCObjectStreamer::Finish();
 569 }
 570
 571 MCStreamer *llvm::createELFStreamer(MCContext &Context, TargetAsmBackend &TAB,
 572                                       raw_ostream &OS, MCCodeEmitter *CE,
 573                                       bool RelaxAll) {
 574   MCELFStreamer *S = new MCELFStreamer(Context, TAB, OS, CE);
 575   if (RelaxAll)
 576     S->getAssembler().setRelaxAll(true);
 577   return S;
 578 }