lib/MC/MCELFStreamer.cpp - llvm - Git at Google

 //===- lib/MC/MCELFStreamer.cpp - ELF Object Output -----------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file assembles .s files and emits ELF .o object files.
 //
 //===----------------------------------------------------------------------===//

 #include "llvm/MC/MCELFStreamer.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCCodeEmitter.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCELF.h"
 #include "llvm/MC/MCELFSymbolFlags.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCObjectStreamer.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCValue.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ELF.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"

 using namespace llvm;


 inline void MCELFStreamer::SetSection(StringRef Section, unsigned Type,
                                       unsigned Flags, SectionKind Kind) {
   SwitchSection(getContext().getELFSection(Section, Type, Flags, Kind));
 }

 inline void MCELFStreamer::SetSectionData() {
   SetSection(".data",
              ELF::SHT_PROGBITS,
              ELF::SHF_WRITE | ELF::SHF_ALLOC,
              SectionKind::getDataRel());
   EmitCodeAlignment(4, 0);
 }

 inline void MCELFStreamer::SetSectionText() {
   SetSection(".text",
              ELF::SHT_PROGBITS,
              ELF::SHF_EXECINSTR | ELF::SHF_ALLOC,
              SectionKind::getText());
   EmitCodeAlignment(4, 0);
 }

 inline void MCELFStreamer::SetSectionBss() {
   SetSection(".bss",
              ELF::SHT_NOBITS,
              ELF::SHF_WRITE | ELF::SHF_ALLOC,
              SectionKind::getBSS());
   EmitCodeAlignment(4, 0);
 }

 MCELFStreamer::~MCELFStreamer() {
 }

 void MCELFStreamer::InitToTextSection() {
   SetSectionText();
 }

 void MCELFStreamer::InitSections() {
   // This emulates the same behavior of GNU as. This makes it easier
   // to compare the output as the major sections are in the same order.
   SetSectionText();
   SetSectionData();
   SetSectionBss();
   SetSectionText();
 }

 void MCELFStreamer::EmitLabel(MCSymbol *Symbol) {
   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");

   MCObjectStreamer::EmitLabel(Symbol);

   const MCSectionELF &Section =
     static_cast<const MCSectionELF&>(Symbol->getSection());
   MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
   if (Section.getFlags() & ELF::SHF_TLS)
     MCELF::SetType(SD, ELF::STT_TLS);
 }

 void MCELFStreamer::EmitDebugLabel(MCSymbol *Symbol) {
   EmitLabel(Symbol);
 }

 void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
   // Let the target do whatever target specific stuff it needs to do.
   getAssembler().getBackend().handleAssemblerFlag(Flag);
   // Do any generic stuff we need to do.
   switch (Flag) {
   case MCAF_SyntaxUnified: return; // no-op here.
   case MCAF_Code16: return; // Change parsing mode; no-op here.
   case MCAF_Code32: return; // Change parsing mode; no-op here.
   case MCAF_Code64: return; // Change parsing mode; no-op here.
   case MCAF_SubsectionsViaSymbols:
     getAssembler().setSubsectionsViaSymbols(true);
     return;
   }

   llvm_unreachable("invalid assembler flag!");
 }

 void MCELFStreamer::ChangeSection(const MCSection *Section,
                                   const MCExpr *Subsection) {
   MCSectionData *CurSection = getCurrentSectionData();
   if (CurSection && CurSection->isBundleLocked())
     report_fatal_error("Unterminated .bundle_lock when changing a section");
   const MCSymbol *Grp = static_cast<const MCSectionELF *>(Section)->getGroup();
   if (Grp)
     getAssembler().getOrCreateSymbolData(*Grp);
   this->MCObjectStreamer::ChangeSection(Section, Subsection);
 }

 void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
   getAssembler().getOrCreateSymbolData(*Symbol);
   MCSymbolData &AliasSD = getAssembler().getOrCreateSymbolData(*Alias);
   AliasSD.setFlags(AliasSD.getFlags() | ELF_Other_Weakref);
   const MCExpr *Value = MCSymbolRefExpr::Create(Symbol, getContext());
   Alias->setVariableValue(Value);
 }

 // When GNU as encounters more than one .type declaration for an object it seems
 // to use a mechanism similar to the one below to decide which type is actually
 // used in the object file.  The greater of T1 and T2 is selected based on the
 // following ordering:
 //  STT_NOTYPE < STT_OBJECT < STT_FUNC < STT_GNU_IFUNC < STT_TLS < anything else
 // If neither T1 < T2 nor T2 < T1 according to this ordering, use T2 (the user
 // provided type).
 static unsigned CombineSymbolTypes(unsigned T1, unsigned T2) {
   unsigned TypeOrdering[] = {ELF::STT_NOTYPE, ELF::STT_OBJECT, ELF::STT_FUNC,
                              ELF::STT_GNU_IFUNC, ELF::STT_TLS};
   for (unsigned i = 0; i != array_lengthof(TypeOrdering); ++i) {
     if (T1 == TypeOrdering[i])
       return T2;
     if (T2 == TypeOrdering[i])
       return T1;
   }

   return T2;
 }

 bool MCELFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
                                         MCSymbolAttr Attribute) {
   // Indirect symbols are handled differently, to match how 'as' handles
   // them. This makes writing matching .o files easier.
   if (Attribute == MCSA_IndirectSymbol) {
     // Note that we intentionally cannot use the symbol data here; this is
     // important for matching the string table that 'as' generates.
     IndirectSymbolData ISD;
     ISD.Symbol = Symbol;
     ISD.SectionData = getCurrentSectionData();
     getAssembler().getIndirectSymbols().push_back(ISD);
     return true;
   }

   // Adding a symbol attribute always introduces the symbol, note that an
   // important side effect of calling getOrCreateSymbolData here is to register
   // the symbol with the assembler.
   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);

   // The implementation of symbol attributes is designed to match 'as', but it
   // leaves much to desired. It doesn't really make sense to arbitrarily add and
   // remove flags, but 'as' allows this (in particular, see .desc).
   //
   // In the future it might be worth trying to make these operations more well
   // defined.
   switch (Attribute) {
   case MCSA_LazyReference:
   case MCSA_Reference:
   case MCSA_SymbolResolver:
   case MCSA_PrivateExtern:
   case MCSA_WeakDefinition:
   case MCSA_WeakDefAutoPrivate:
   case MCSA_Invalid:
   case MCSA_IndirectSymbol:
     return false;

   case MCSA_NoDeadStrip:
   case MCSA_ELF_TypeGnuUniqueObject:
     // Ignore for now.
     break;

   case MCSA_Global:
     MCELF::SetBinding(SD, ELF::STB_GLOBAL);
     SD.setExternal(true);
     BindingExplicitlySet.insert(Symbol);
     break;

   case MCSA_WeakReference:
   case MCSA_Weak:
     MCELF::SetBinding(SD, ELF::STB_WEAK);
     SD.setExternal(true);
     BindingExplicitlySet.insert(Symbol);
     break;

   case MCSA_Local:
     MCELF::SetBinding(SD, ELF::STB_LOCAL);
     SD.setExternal(false);
     BindingExplicitlySet.insert(Symbol);
     break;

   case MCSA_ELF_TypeFunction:
     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
                                           ELF::STT_FUNC));
     break;

   case MCSA_ELF_TypeIndFunction:
     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
                                           ELF::STT_GNU_IFUNC));
     break;

   case MCSA_ELF_TypeObject:
     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
                                           ELF::STT_OBJECT));
     break;

   case MCSA_ELF_TypeTLS:
     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
                                           ELF::STT_TLS));
     break;

   case MCSA_ELF_TypeCommon:
     // TODO: Emit these as a common symbol.
     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
                                           ELF::STT_OBJECT));
     break;

   case MCSA_ELF_TypeNoType:
     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
                                           ELF::STT_NOTYPE));
     break;

   case MCSA_Protected:
     MCELF::SetVisibility(SD, ELF::STV_PROTECTED);
     break;

   case MCSA_Hidden:
     MCELF::SetVisibility(SD, ELF::STV_HIDDEN);
     break;

   case MCSA_Internal:
     MCELF::SetVisibility(SD, ELF::STV_INTERNAL);
     break;
   }

   return true;
 }

 void MCELFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                        unsigned ByteAlignment) {
   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);

   if (!BindingExplicitlySet.count(Symbol)) {
     MCELF::SetBinding(SD, ELF::STB_GLOBAL);
     SD.setExternal(true);
   }

   MCELF::SetType(SD, ELF::STT_OBJECT);

   if (MCELF::GetBinding(SD) == ELF_STB_Local) {
     const MCSection *Section = getAssembler().getContext().getELFSection(".bss",
                                                          ELF::SHT_NOBITS,
                                                          ELF::SHF_WRITE |
                                                          ELF::SHF_ALLOC,
                                                          SectionKind::getBSS());

     AssignSection(Symbol, Section);

     struct LocalCommon L = {&SD, Size, ByteAlignment};
     LocalCommons.push_back(L);
   } else {
     SD.setCommon(Size, ByteAlignment);
   }

   SD.setSize(MCConstantExpr::Create(Size, getContext()));
 }

 void MCELFStreamer::EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
   SD.setSize(Value);
 }

 void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                           unsigned ByteAlignment) {
   // FIXME: Should this be caught and done earlier?
   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
   MCELF::SetBinding(SD, ELF::STB_LOCAL);
   SD.setExternal(false);
   BindingExplicitlySet.insert(Symbol);
   EmitCommonSymbol(Symbol, Size, ByteAlignment);
 }

 void MCELFStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size) {
   if (getCurrentSectionData()->isBundleLocked())
     report_fatal_error("Emitting values inside a locked bundle is forbidden");
   fixSymbolsInTLSFixups(Value);
   MCObjectStreamer::EmitValueImpl(Value, Size);
 }

 void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
                                          int64_t Value,
                                          unsigned ValueSize,
                                          unsigned MaxBytesToEmit) {
   if (getCurrentSectionData()->isBundleLocked())
     report_fatal_error("Emitting values inside a locked bundle is forbidden");
   MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value,
                                          ValueSize, MaxBytesToEmit);
 }

 // Add a symbol for the file name of this module. They start after the
 // null symbol and don't count as normal symbol, i.e. a non-STT_FILE symbol
 // with the same name may appear.
 void MCELFStreamer::EmitFileDirective(StringRef Filename) {
   getAssembler().addFileName(Filename);
 }

 void MCELFStreamer::EmitIdent(StringRef IdentString) {
   const MCSection *Comment = getAssembler().getContext().getELFSection(
       ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS,
       SectionKind::getReadOnly(), 1, "");
   PushSection();
   SwitchSection(Comment);
   if (!SeenIdent) {
     EmitIntValue(0, 1);
     SeenIdent = true;
   }
   EmitBytes(IdentString);
   EmitIntValue(0, 1);
   PopSection();
 }

 void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
   switch (expr->getKind()) {
   case MCExpr::Target:
     cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
     break;
   case MCExpr::Constant:
     break;

   case MCExpr::Binary: {
     const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
     fixSymbolsInTLSFixups(be->getLHS());
     fixSymbolsInTLSFixups(be->getRHS());
     break;
   }

   case MCExpr::SymbolRef: {
     const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
     switch (symRef.getKind()) {
     default:
       return;
     case MCSymbolRefExpr::VK_GOTTPOFF:
     case MCSymbolRefExpr::VK_INDNTPOFF:
     case MCSymbolRefExpr::VK_NTPOFF:
     case MCSymbolRefExpr::VK_GOTNTPOFF:
     case MCSymbolRefExpr::VK_TLSGD:
     case MCSymbolRefExpr::VK_TLSLD:
     case MCSymbolRefExpr::VK_TLSLDM:
     case MCSymbolRefExpr::VK_TPOFF:
     case MCSymbolRefExpr::VK_DTPOFF:
     case MCSymbolRefExpr::VK_ARM_TLSGD:
     case MCSymbolRefExpr::VK_ARM_TPOFF:
     case MCSymbolRefExpr::VK_ARM_GOTTPOFF:
     case MCSymbolRefExpr::VK_Mips_TLSGD:
     case MCSymbolRefExpr::VK_Mips_GOTTPREL:
     case MCSymbolRefExpr::VK_Mips_TPREL_HI:
     case MCSymbolRefExpr::VK_Mips_TPREL_LO:
     case MCSymbolRefExpr::VK_PPC_DTPMOD:
     case MCSymbolRefExpr::VK_PPC_TPREL:
     case MCSymbolRefExpr::VK_PPC_TPREL_LO:
     case MCSymbolRefExpr::VK_PPC_TPREL_HI:
     case MCSymbolRefExpr::VK_PPC_TPREL_HA:
     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
     case MCSymbolRefExpr::VK_PPC_DTPREL:
     case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
     case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
     case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
     case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
     case MCSymbolRefExpr::VK_PPC_TLS:
     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
     case MCSymbolRefExpr::VK_PPC_TLSGD:
     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
     case MCSymbolRefExpr::VK_PPC_TLSLD:
       break;
     }
     MCSymbolData &SD = getAssembler().getOrCreateSymbolData(symRef.getSymbol());
     MCELF::SetType(SD, ELF::STT_TLS);
     break;
   }

   case MCExpr::Unary:
     fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
     break;
   }
 }

 void MCELFStreamer::EmitInstToFragment(const MCInst &Inst) {
   this->MCObjectStreamer::EmitInstToFragment(Inst);
   MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());

   for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
     fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
 }

 void MCELFStreamer::EmitInstToData(const MCInst &Inst) {
   MCAssembler &Assembler = getAssembler();
   SmallVector<MCFixup, 4> Fixups;
   SmallString<256> Code;
   raw_svector_ostream VecOS(Code);
   Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
   VecOS.flush();

   for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
     fixSymbolsInTLSFixups(Fixups[i].getValue());

   // There are several possibilities here:
   //
   // If bundling is disabled, append the encoded instruction to the current data
   // fragment (or create a new such fragment if the current fragment is not a
   // data fragment).
   //
   // If bundling is enabled:
   // - If we're not in a bundle-locked group, emit the instruction into a
   //   fragment of its own. If there are no fixups registered for the
   //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
   //   MCDataFragment.
   // - If we're in a bundle-locked group, append the instruction to the current
   //   data fragment because we want all the instructions in a group to get into
   //   the same fragment. Be careful not to do that for the first instruction in
   //   the group, though.
   MCDataFragment *DF;

   if (Assembler.isBundlingEnabled()) {
     MCSectionData *SD = getCurrentSectionData();
     if (SD->isBundleLocked() && !SD->isBundleGroupBeforeFirstInst())
       // If we are bundle-locked, we re-use the current fragment.
       // The bundle-locking directive ensures this is a new data fragment.
       DF = cast<MCDataFragment>(getCurrentFragment());
     else if (!SD->isBundleLocked() && Fixups.size() == 0) {
       // Optimize memory usage by emitting the instruction to a
       // MCCompactEncodedInstFragment when not in a bundle-locked group and
       // there are no fixups registered.
       MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
       insert(CEIF);
       CEIF->getContents().append(Code.begin(), Code.end());
       return;
     } else {
       DF = new MCDataFragment();
       insert(DF);
       if (SD->getBundleLockState() == MCSectionData::BundleLockedAlignToEnd) {
         // If this is a new fragment created for a bundle-locked group, and the
         // group was marked as "align_to_end", set a flag in the fragment.
         DF->setAlignToBundleEnd(true);
       }
     }

     // We're now emitting an instruction in a bundle group, so this flag has
     // to be turned off.
     SD->setBundleGroupBeforeFirstInst(false);
   } else {
     DF = getOrCreateDataFragment();
   }

   // Add the fixups and data.
   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
     DF->getFixups().push_back(Fixups[i]);
   }
   DF->setHasInstructions(true);
   DF->getContents().append(Code.begin(), Code.end());
 }

 void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
   assert(AlignPow2 <= 30 && "Invalid bundle alignment");
   MCAssembler &Assembler = getAssembler();
   if (Assembler.getBundleAlignSize() == 0 && AlignPow2 > 0)
     Assembler.setBundleAlignSize(1 << AlignPow2);
   else
     report_fatal_error(".bundle_align_mode should be only set once per file");
 }

 void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
   MCSectionData *SD = getCurrentSectionData();

   // Sanity checks
   //
   if (!getAssembler().isBundlingEnabled())
     report_fatal_error(".bundle_lock forbidden when bundling is disabled");
   else if (SD->isBundleLocked())
     report_fatal_error("Nesting of .bundle_lock is forbidden");

   SD->setBundleLockState(AlignToEnd ? MCSectionData::BundleLockedAlignToEnd :
                                       MCSectionData::BundleLocked);
   SD->setBundleGroupBeforeFirstInst(true);
 }

 void MCELFStreamer::EmitBundleUnlock() {
   MCSectionData *SD = getCurrentSectionData();

   // Sanity checks
   if (!getAssembler().isBundlingEnabled())
     report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
   else if (!SD->isBundleLocked())
     report_fatal_error(".bundle_unlock without matching lock");
   else if (SD->isBundleGroupBeforeFirstInst())
     report_fatal_error("Empty bundle-locked group is forbidden");

   SD->setBundleLockState(MCSectionData::NotBundleLocked);
 }

 void MCELFStreamer::Flush() {
   for (std::vector<LocalCommon>::const_iterator i = LocalCommons.begin(),
                                                 e = LocalCommons.end();
        i != e; ++i) {
     MCSymbolData *SD = i->SD;
     uint64_t Size = i->Size;
     unsigned ByteAlignment = i->ByteAlignment;
     const MCSymbol &Symbol = SD->getSymbol();
     const MCSection &Section = Symbol.getSection();

     MCSectionData &SectData = getAssembler().getOrCreateSectionData(Section);
     new MCAlignFragment(ByteAlignment, 0, 1, ByteAlignment, &SectData);

     MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
     SD->setFragment(F);

     // Update the maximum alignment of the section if necessary.
     if (ByteAlignment > SectData.getAlignment())
       SectData.setAlignment(ByteAlignment);
   }

   LocalCommons.clear();
 }

 void MCELFStreamer::FinishImpl() {
   EmitFrames(NULL, true);

   Flush();

   this->MCObjectStreamer::FinishImpl();
 }

 MCStreamer *llvm::createELFStreamer(MCContext &Context,
                                     MCTargetStreamer *Streamer,
                                     MCAsmBackend &MAB, raw_ostream &OS,
                                     MCCodeEmitter *CE, bool RelaxAll,
                                     bool NoExecStack) {
   MCELFStreamer *S = new MCELFStreamer(Context, Streamer, MAB, OS, CE);
   if (RelaxAll)
     S->getAssembler().setRelaxAll(true);
   if (NoExecStack)
     S->getAssembler().setNoExecStack(true);
   return S;
 }

 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
   llvm_unreachable("Generic ELF doesn't support this directive");
 }

 MCSymbolData &MCELFStreamer::getOrCreateSymbolData(MCSymbol *Symbol) {
   return getAssembler().getOrCreateSymbolData(*Symbol);
 }

 void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
   llvm_unreachable("ELF doesn't support this directive");
 }

 void MCELFStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
   llvm_unreachable("ELF doesn't support this directive");
 }

 void MCELFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
   llvm_unreachable("ELF doesn't support this directive");
 }

 void MCELFStreamer::EmitCOFFSymbolType(int Type) {
   llvm_unreachable("ELF doesn't support this directive");
 }

 void MCELFStreamer::EndCOFFSymbolDef() {
   llvm_unreachable("ELF doesn't support this directive");
 }

 void MCELFStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
                                  uint64_t Size, unsigned ByteAlignment) {
   llvm_unreachable("ELF doesn't support this directive");
 }

 void MCELFStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
                                    uint64_t Size, unsigned ByteAlignment) {
   llvm_unreachable("ELF doesn't support this directive");
 }
	//===- lib/MC/MCELFStreamer.cpp - ELF Object Output -----------------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This file assembles .s files and emits ELF .o object files.
	//
	//===----------------------------------------------------------------------===//

	#include "llvm/MC/MCELFStreamer.h"
	#include "llvm/ADT/SmallPtrSet.h"
	#include "llvm/ADT/STLExtras.h"
	#include "llvm/MC/MCAssembler.h"
	#include "llvm/MC/MCAsmBackend.h"
	#include "llvm/MC/MCCodeEmitter.h"
	#include "llvm/MC/MCContext.h"
	#include "llvm/MC/MCELF.h"
	#include "llvm/MC/MCELFSymbolFlags.h"
	#include "llvm/MC/MCExpr.h"
	#include "llvm/MC/MCInst.h"
	#include "llvm/MC/MCObjectStreamer.h"
	#include "llvm/MC/MCSection.h"
	#include "llvm/MC/MCSectionELF.h"
	#include "llvm/MC/MCSymbol.h"
	#include "llvm/MC/MCValue.h"
	#include "llvm/Support/Debug.h"
	#include "llvm/Support/ELF.h"
	#include "llvm/Support/ErrorHandling.h"
	#include "llvm/Support/raw_ostream.h"

	using namespace llvm;


	inline void MCELFStreamer::SetSection(StringRef Section, unsigned Type,
	unsigned Flags, SectionKind Kind) {
	SwitchSection(getContext().getELFSection(Section, Type, Flags, Kind));
	}

	inline void MCELFStreamer::SetSectionData() {
	SetSection(".data",
	ELF::SHT_PROGBITS,
	ELF::SHF_WRITE \| ELF::SHF_ALLOC,
	SectionKind::getDataRel());
	EmitCodeAlignment(4, 0);
	}

	inline void MCELFStreamer::SetSectionText() {
	SetSection(".text",
	ELF::SHT_PROGBITS,
	ELF::SHF_EXECINSTR \| ELF::SHF_ALLOC,
	SectionKind::getText());
	EmitCodeAlignment(4, 0);
	}

	inline void MCELFStreamer::SetSectionBss() {
	SetSection(".bss",
	ELF::SHT_NOBITS,
	ELF::SHF_WRITE \| ELF::SHF_ALLOC,
	SectionKind::getBSS());
	EmitCodeAlignment(4, 0);
	}

	MCELFStreamer::~MCELFStreamer() {
	}

	void MCELFStreamer::InitToTextSection() {
	SetSectionText();
	}

	void MCELFStreamer::InitSections() {
	// This emulates the same behavior of GNU as. This makes it easier
	// to compare the output as the major sections are in the same order.
	SetSectionText();
	SetSectionData();
	SetSectionBss();
	SetSectionText();
	}

	void MCELFStreamer::EmitLabel(MCSymbol *Symbol) {
	assert(Symbol->isUndefined() && "Cannot define a symbol twice!");

	MCObjectStreamer::EmitLabel(Symbol);

	const MCSectionELF &Section =
	static_cast<const MCSectionELF&>(Symbol->getSection());
	MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
	if (Section.getFlags() & ELF::SHF_TLS)
	MCELF::SetType(SD, ELF::STT_TLS);
	}

	void MCELFStreamer::EmitDebugLabel(MCSymbol *Symbol) {
	EmitLabel(Symbol);
	}

	void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
	// Let the target do whatever target specific stuff it needs to do.
	getAssembler().getBackend().handleAssemblerFlag(Flag);
	// Do any generic stuff we need to do.
	switch (Flag) {
	case MCAF_SyntaxUnified: return; // no-op here.
	case MCAF_Code16: return; // Change parsing mode; no-op here.
	case MCAF_Code32: return; // Change parsing mode; no-op here.
	case MCAF_Code64: return; // Change parsing mode; no-op here.
	case MCAF_SubsectionsViaSymbols:
	getAssembler().setSubsectionsViaSymbols(true);
	return;
	}

	llvm_unreachable("invalid assembler flag!");
	}

	void MCELFStreamer::ChangeSection(const MCSection *Section,
	const MCExpr *Subsection) {
	MCSectionData *CurSection = getCurrentSectionData();
	if (CurSection && CurSection->isBundleLocked())
	report_fatal_error("Unterminated .bundle_lock when changing a section");
	const MCSymbol Grp = static_cast<const MCSectionELF >(Section)->getGroup();
	if (Grp)
	getAssembler().getOrCreateSymbolData(*Grp);
	this->MCObjectStreamer::ChangeSection(Section, Subsection);
	}

	void MCELFStreamer::EmitWeakReference(MCSymbol Alias, const MCSymbol Symbol) {
	getAssembler().getOrCreateSymbolData(*Symbol);
	MCSymbolData &AliasSD = getAssembler().getOrCreateSymbolData(*Alias);
	AliasSD.setFlags(AliasSD.getFlags() \| ELF_Other_Weakref);
	const MCExpr *Value = MCSymbolRefExpr::Create(Symbol, getContext());
	Alias->setVariableValue(Value);
	}

	// When GNU as encounters more than one .type declaration for an object it seems
	// to use a mechanism similar to the one below to decide which type is actually
	// used in the object file. The greater of T1 and T2 is selected based on the
	// following ordering:
	// STT_NOTYPE < STT_OBJECT < STT_FUNC < STT_GNU_IFUNC < STT_TLS < anything else
	// If neither T1 < T2 nor T2 < T1 according to this ordering, use T2 (the user
	// provided type).
	static unsigned CombineSymbolTypes(unsigned T1, unsigned T2) {
	unsigned TypeOrdering[] = {ELF::STT_NOTYPE, ELF::STT_OBJECT, ELF::STT_FUNC,
	ELF::STT_GNU_IFUNC, ELF::STT_TLS};
	for (unsigned i = 0; i != array_lengthof(TypeOrdering); ++i) {
	if (T1 == TypeOrdering[i])
	return T2;
	if (T2 == TypeOrdering[i])
	return T1;
	}

	return T2;
	}

	bool MCELFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
	MCSymbolAttr Attribute) {
	// Indirect symbols are handled differently, to match how 'as' handles
	// them. This makes writing matching .o files easier.
	if (Attribute == MCSA_IndirectSymbol) {
	// Note that we intentionally cannot use the symbol data here; this is
	// important for matching the string table that 'as' generates.
	IndirectSymbolData ISD;
	ISD.Symbol = Symbol;
	ISD.SectionData = getCurrentSectionData();
	getAssembler().getIndirectSymbols().push_back(ISD);
	return true;
	}

	// Adding a symbol attribute always introduces the symbol, note that an
	// important side effect of calling getOrCreateSymbolData here is to register
	// the symbol with the assembler.
	MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);

	// The implementation of symbol attributes is designed to match 'as', but it
	// leaves much to desired. It doesn't really make sense to arbitrarily add and
	// remove flags, but 'as' allows this (in particular, see .desc).
	//
	// In the future it might be worth trying to make these operations more well
	// defined.
	switch (Attribute) {
	case MCSA_LazyReference:
	case MCSA_Reference:
	case MCSA_SymbolResolver:
	case MCSA_PrivateExtern:
	case MCSA_WeakDefinition:
	case MCSA_WeakDefAutoPrivate:
	case MCSA_Invalid:
	case MCSA_IndirectSymbol:
	return false;

	case MCSA_NoDeadStrip:
	case MCSA_ELF_TypeGnuUniqueObject:
	// Ignore for now.
	break;

	case MCSA_Global:
	MCELF::SetBinding(SD, ELF::STB_GLOBAL);
	SD.setExternal(true);
	BindingExplicitlySet.insert(Symbol);
	break;

	case MCSA_WeakReference:
	case MCSA_Weak:
	MCELF::SetBinding(SD, ELF::STB_WEAK);
	SD.setExternal(true);
	BindingExplicitlySet.insert(Symbol);
	break;

	case MCSA_Local:
	MCELF::SetBinding(SD, ELF::STB_LOCAL);
	SD.setExternal(false);
	BindingExplicitlySet.insert(Symbol);
	break;

	case MCSA_ELF_TypeFunction:
	MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
	ELF::STT_FUNC));
	break;

	case MCSA_ELF_TypeIndFunction:
	MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
	ELF::STT_GNU_IFUNC));
	break;

	case MCSA_ELF_TypeObject:
	MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
	ELF::STT_OBJECT));
	break;

	case MCSA_ELF_TypeTLS:
	MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
	ELF::STT_TLS));
	break;

	case MCSA_ELF_TypeCommon:
	// TODO: Emit these as a common symbol.
	MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
	ELF::STT_OBJECT));
	break;

	case MCSA_ELF_TypeNoType:
	MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
	ELF::STT_NOTYPE));
	break;

	case MCSA_Protected:
	MCELF::SetVisibility(SD, ELF::STV_PROTECTED);
	break;

	case MCSA_Hidden:
	MCELF::SetVisibility(SD, ELF::STV_HIDDEN);
	break;

	case MCSA_Internal:
	MCELF::SetVisibility(SD, ELF::STV_INTERNAL);
	break;
	}

	return true;
	}

	void MCELFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
	unsigned ByteAlignment) {
	MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);

	if (!BindingExplicitlySet.count(Symbol)) {
	MCELF::SetBinding(SD, ELF::STB_GLOBAL);
	SD.setExternal(true);
	}

	MCELF::SetType(SD, ELF::STT_OBJECT);

	if (MCELF::GetBinding(SD) == ELF_STB_Local) {
	const MCSection *Section = getAssembler().getContext().getELFSection(".bss",
	ELF::SHT_NOBITS,
	ELF::SHF_WRITE \|
	ELF::SHF_ALLOC,
	SectionKind::getBSS());

	AssignSection(Symbol, Section);

	struct LocalCommon L = {&SD, Size, ByteAlignment};
	LocalCommons.push_back(L);
	} else {
	SD.setCommon(Size, ByteAlignment);
	}

	SD.setSize(MCConstantExpr::Create(Size, getContext()));
	}

	void MCELFStreamer::EmitELFSize(MCSymbol Symbol, const MCExpr Value) {
	MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
	SD.setSize(Value);
	}

	void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
	unsigned ByteAlignment) {
	// FIXME: Should this be caught and done earlier?
	MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
	MCELF::SetBinding(SD, ELF::STB_LOCAL);
	SD.setExternal(false);
	BindingExplicitlySet.insert(Symbol);
	EmitCommonSymbol(Symbol, Size, ByteAlignment);
	}

	void MCELFStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size) {
	if (getCurrentSectionData()->isBundleLocked())
	report_fatal_error("Emitting values inside a locked bundle is forbidden");
	fixSymbolsInTLSFixups(Value);
	MCObjectStreamer::EmitValueImpl(Value, Size);
	}

	void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
	int64_t Value,
	unsigned ValueSize,
	unsigned MaxBytesToEmit) {
	if (getCurrentSectionData()->isBundleLocked())
	report_fatal_error("Emitting values inside a locked bundle is forbidden");
	MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value,
	ValueSize, MaxBytesToEmit);
	}

	// Add a symbol for the file name of this module. They start after the
	// null symbol and don't count as normal symbol, i.e. a non-STT_FILE symbol
	// with the same name may appear.
	void MCELFStreamer::EmitFileDirective(StringRef Filename) {
	getAssembler().addFileName(Filename);
	}

	void MCELFStreamer::EmitIdent(StringRef IdentString) {
	const MCSection *Comment = getAssembler().getContext().getELFSection(
	".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE \| ELF::SHF_STRINGS,
	SectionKind::getReadOnly(), 1, "");
	PushSection();
	SwitchSection(Comment);
	if (!SeenIdent) {
	EmitIntValue(0, 1);
	SeenIdent = true;
	}
	EmitBytes(IdentString);
	EmitIntValue(0, 1);
	PopSection();
	}

	void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
	switch (expr->getKind()) {
	case MCExpr::Target:
	cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
	break;
	case MCExpr::Constant:
	break;

	case MCExpr::Binary: {
	const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
	fixSymbolsInTLSFixups(be->getLHS());
	fixSymbolsInTLSFixups(be->getRHS());
	break;
	}

	case MCExpr::SymbolRef: {
	const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
	switch (symRef.getKind()) {
	default:
	return;
	case MCSymbolRefExpr::VK_GOTTPOFF:
	case MCSymbolRefExpr::VK_INDNTPOFF:
	case MCSymbolRefExpr::VK_NTPOFF:
	case MCSymbolRefExpr::VK_GOTNTPOFF:
	case MCSymbolRefExpr::VK_TLSGD:
	case MCSymbolRefExpr::VK_TLSLD:
	case MCSymbolRefExpr::VK_TLSLDM:
	case MCSymbolRefExpr::VK_TPOFF:
	case MCSymbolRefExpr::VK_DTPOFF:
	case MCSymbolRefExpr::VK_ARM_TLSGD:
	case MCSymbolRefExpr::VK_ARM_TPOFF:
	case MCSymbolRefExpr::VK_ARM_GOTTPOFF:
	case MCSymbolRefExpr::VK_Mips_TLSGD:
	case MCSymbolRefExpr::VK_Mips_GOTTPREL:
	case MCSymbolRefExpr::VK_Mips_TPREL_HI:
	case MCSymbolRefExpr::VK_Mips_TPREL_LO:
	case MCSymbolRefExpr::VK_PPC_DTPMOD:
	case MCSymbolRefExpr::VK_PPC_TPREL:
	case MCSymbolRefExpr::VK_PPC_TPREL_LO:
	case MCSymbolRefExpr::VK_PPC_TPREL_HI:
	case MCSymbolRefExpr::VK_PPC_TPREL_HA:
	case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
	case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
	case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
	case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
	case MCSymbolRefExpr::VK_PPC_DTPREL:
	case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
	case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
	case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
	case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
	case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
	case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
	case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
	case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
	case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
	case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
	case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
	case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
	case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
	case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
	case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
	case MCSymbolRefExpr::VK_PPC_TLS:
	case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
	case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
	case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
	case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
	case MCSymbolRefExpr::VK_PPC_TLSGD:
	case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
	case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
	case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
	case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
	case MCSymbolRefExpr::VK_PPC_TLSLD:
	break;
	}
	MCSymbolData &SD = getAssembler().getOrCreateSymbolData(symRef.getSymbol());
	MCELF::SetType(SD, ELF::STT_TLS);
	break;
	}

	case MCExpr::Unary:
	fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
	break;
	}
	}

	void MCELFStreamer::EmitInstToFragment(const MCInst &Inst) {
	this->MCObjectStreamer::EmitInstToFragment(Inst);
	MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());

	for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
	fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
	}

	void MCELFStreamer::EmitInstToData(const MCInst &Inst) {
	MCAssembler &Assembler = getAssembler();
	SmallVector<MCFixup, 4> Fixups;
	SmallString<256> Code;
	raw_svector_ostream VecOS(Code);
	Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
	VecOS.flush();

	for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
	fixSymbolsInTLSFixups(Fixups[i].getValue());

	// There are several possibilities here:
	//
	// If bundling is disabled, append the encoded instruction to the current data
	// fragment (or create a new such fragment if the current fragment is not a
	// data fragment).
	//
	// If bundling is enabled:
	// - If we're not in a bundle-locked group, emit the instruction into a
	// fragment of its own. If there are no fixups registered for the
	// instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
	// MCDataFragment.
	// - If we're in a bundle-locked group, append the instruction to the current
	// data fragment because we want all the instructions in a group to get into
	// the same fragment. Be careful not to do that for the first instruction in
	// the group, though.
	MCDataFragment *DF;

	if (Assembler.isBundlingEnabled()) {
	MCSectionData *SD = getCurrentSectionData();
	if (SD->isBundleLocked() && !SD->isBundleGroupBeforeFirstInst())
	// If we are bundle-locked, we re-use the current fragment.
	// The bundle-locking directive ensures this is a new data fragment.
	DF = cast<MCDataFragment>(getCurrentFragment());
	else if (!SD->isBundleLocked() && Fixups.size() == 0) {
	// Optimize memory usage by emitting the instruction to a
	// MCCompactEncodedInstFragment when not in a bundle-locked group and
	// there are no fixups registered.
	MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
	insert(CEIF);
	CEIF->getContents().append(Code.begin(), Code.end());
	return;
	} else {
	DF = new MCDataFragment();
	insert(DF);
	if (SD->getBundleLockState() == MCSectionData::BundleLockedAlignToEnd) {
	// If this is a new fragment created for a bundle-locked group, and the
	// group was marked as "align_to_end", set a flag in the fragment.
	DF->setAlignToBundleEnd(true);
	}
	}

	// We're now emitting an instruction in a bundle group, so this flag has
	// to be turned off.
	SD->setBundleGroupBeforeFirstInst(false);
	} else {
	DF = getOrCreateDataFragment();
	}

	// Add the fixups and data.
	for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
	Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
	DF->getFixups().push_back(Fixups[i]);
	}
	DF->setHasInstructions(true);
	DF->getContents().append(Code.begin(), Code.end());
	}

	void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
	assert(AlignPow2 <= 30 && "Invalid bundle alignment");
	MCAssembler &Assembler = getAssembler();
	if (Assembler.getBundleAlignSize() == 0 && AlignPow2 > 0)
	Assembler.setBundleAlignSize(1 << AlignPow2);
	else
	report_fatal_error(".bundle_align_mode should be only set once per file");
	}

	void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
	MCSectionData *SD = getCurrentSectionData();

	// Sanity checks
	//
	if (!getAssembler().isBundlingEnabled())
	report_fatal_error(".bundle_lock forbidden when bundling is disabled");
	else if (SD->isBundleLocked())
	report_fatal_error("Nesting of .bundle_lock is forbidden");

	SD->setBundleLockState(AlignToEnd ? MCSectionData::BundleLockedAlignToEnd :
	MCSectionData::BundleLocked);
	SD->setBundleGroupBeforeFirstInst(true);
	}

	void MCELFStreamer::EmitBundleUnlock() {
	MCSectionData *SD = getCurrentSectionData();

	// Sanity checks
	if (!getAssembler().isBundlingEnabled())
	report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
	else if (!SD->isBundleLocked())
	report_fatal_error(".bundle_unlock without matching lock");
	else if (SD->isBundleGroupBeforeFirstInst())
	report_fatal_error("Empty bundle-locked group is forbidden");

	SD->setBundleLockState(MCSectionData::NotBundleLocked);
	}

	void MCELFStreamer::Flush() {
	for (std::vector<LocalCommon>::const_iterator i = LocalCommons.begin(),
	e = LocalCommons.end();
	i != e; ++i) {
	MCSymbolData *SD = i->SD;
	uint64_t Size = i->Size;
	unsigned ByteAlignment = i->ByteAlignment;
	const MCSymbol &Symbol = SD->getSymbol();
	const MCSection &Section = Symbol.getSection();

	MCSectionData &SectData = getAssembler().getOrCreateSectionData(Section);
	new MCAlignFragment(ByteAlignment, 0, 1, ByteAlignment, &SectData);

	MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
	SD->setFragment(F);

	// Update the maximum alignment of the section if necessary.
	if (ByteAlignment > SectData.getAlignment())
	SectData.setAlignment(ByteAlignment);
	}

	LocalCommons.clear();
	}

	void MCELFStreamer::FinishImpl() {
	EmitFrames(NULL, true);

	Flush();

	this->MCObjectStreamer::FinishImpl();
	}

	MCStreamer *llvm::createELFStreamer(MCContext &Context,
	MCTargetStreamer *Streamer,
	MCAsmBackend &MAB, raw_ostream &OS,
	MCCodeEmitter *CE, bool RelaxAll,
	bool NoExecStack) {
	MCELFStreamer *S = new MCELFStreamer(Context, Streamer, MAB, OS, CE);
	if (RelaxAll)
	S->getAssembler().setRelaxAll(true);
	if (NoExecStack)
	S->getAssembler().setNoExecStack(true);
	return S;
	}

	void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
	llvm_unreachable("Generic ELF doesn't support this directive");
	}

	MCSymbolData &MCELFStreamer::getOrCreateSymbolData(MCSymbol *Symbol) {
	return getAssembler().getOrCreateSymbolData(*Symbol);
	}

	void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
	llvm_unreachable("ELF doesn't support this directive");
	}

	void MCELFStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
	llvm_unreachable("ELF doesn't support this directive");
	}

	void MCELFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
	llvm_unreachable("ELF doesn't support this directive");
	}

	void MCELFStreamer::EmitCOFFSymbolType(int Type) {
	llvm_unreachable("ELF doesn't support this directive");
	}

	void MCELFStreamer::EndCOFFSymbolDef() {
	llvm_unreachable("ELF doesn't support this directive");
	}

	void MCELFStreamer::EmitZerofill(const MCSection Section, MCSymbol Symbol,
	uint64_t Size, unsigned ByteAlignment) {
	llvm_unreachable("ELF doesn't support this directive");
	}

	void MCELFStreamer::EmitTBSSSymbol(const MCSection Section, MCSymbol Symbol,
	uint64_t Size, unsigned ByteAlignment) {
	llvm_unreachable("ELF doesn't support this directive");
	}