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      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/SmallPtrSet.h"
     16 #include "llvm/ADT/STLExtras.h"
     17 #include "llvm/MC/MCAssembler.h"
     18 #include "llvm/MC/MCCodeEmitter.h"
     19 #include "llvm/MC/MCContext.h"
     20 #include "llvm/MC/MCELF.h"
     21 #include "llvm/MC/MCELFSymbolFlags.h"
     22 #include "llvm/MC/MCExpr.h"
     23 #include "llvm/MC/MCInst.h"
     24 #include "llvm/MC/MCObjectStreamer.h"
     25 #include "llvm/MC/MCSection.h"
     26 #include "llvm/MC/MCSectionELF.h"
     27 #include "llvm/MC/MCSymbol.h"
     28 #include "llvm/MC/MCValue.h"
     29 #include "llvm/Support/Debug.h"
     30 #include "llvm/Support/ELF.h"
     31 #include "llvm/Support/ErrorHandling.h"
     32 #include "llvm/Support/raw_ostream.h"
     33 
     34 using namespace llvm;
     35 
     36 
     37 inline void MCELFStreamer::SetSection(StringRef Section, unsigned Type,
     38                                       unsigned Flags, SectionKind Kind) {
     39   SwitchSection(getContext().getELFSection(Section, Type, Flags, Kind));
     40 }
     41 
     42 inline void MCELFStreamer::SetSectionData() {
     43   SetSection(".data",
     44              ELF::SHT_PROGBITS,
     45              ELF::SHF_WRITE | ELF::SHF_ALLOC,
     46              SectionKind::getDataRel());
     47   EmitCodeAlignment(4, 0);
     48 }
     49 
     50 inline void MCELFStreamer::SetSectionText() {
     51   SetSection(".text",
     52              ELF::SHT_PROGBITS,
     53              ELF::SHF_EXECINSTR | ELF::SHF_ALLOC,
     54              SectionKind::getText());
     55   EmitCodeAlignment(4, 0);
     56 }
     57 
     58 inline void MCELFStreamer::SetSectionBss() {
     59   SetSection(".bss",
     60              ELF::SHT_NOBITS,
     61              ELF::SHF_WRITE | ELF::SHF_ALLOC,
     62              SectionKind::getBSS());
     63   EmitCodeAlignment(4, 0);
     64 }
     65 
     66 MCELFStreamer::~MCELFStreamer() {
     67 }
     68 
     69 void MCELFStreamer::InitToTextSection() {
     70   SetSectionText();
     71 }
     72 
     73 void MCELFStreamer::InitSections() {
     74   // This emulates the same behavior of GNU as. This makes it easier
     75   // to compare the output as the major sections are in the same order.
     76   SetSectionText();
     77   SetSectionData();
     78   SetSectionBss();
     79   SetSectionText();
     80 }
     81 
     82 void MCELFStreamer::EmitLabel(MCSymbol *Symbol) {
     83   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
     84 
     85   MCObjectStreamer::EmitLabel(Symbol);
     86 
     87   const MCSectionELF &Section =
     88     static_cast<const MCSectionELF&>(Symbol->getSection());
     89   MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
     90   if (Section.getFlags() & ELF::SHF_TLS)
     91     MCELF::SetType(SD, ELF::STT_TLS);
     92 }
     93 
     94 void MCELFStreamer::EmitDebugLabel(MCSymbol *Symbol) {
     95   EmitLabel(Symbol);
     96 }
     97 
     98 void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
     99   switch (Flag) {
    100   case MCAF_SyntaxUnified: return; // no-op here.
    101   case MCAF_Code16: return; // Change parsing mode; no-op here.
    102   case MCAF_Code32: return; // Change parsing mode; no-op here.
    103   case MCAF_Code64: return; // Change parsing mode; no-op here.
    104   case MCAF_SubsectionsViaSymbols:
    105     getAssembler().setSubsectionsViaSymbols(true);
    106     return;
    107   }
    108 
    109   llvm_unreachable("invalid assembler flag!");
    110 }
    111 
    112 void MCELFStreamer::ChangeSection(const MCSection *Section,
    113                                   const MCExpr *Subsection) {
    114   MCSectionData *CurSection = getCurrentSectionData();
    115   if (CurSection && CurSection->isBundleLocked())
    116     report_fatal_error("Unterminated .bundle_lock when changing a section");
    117   const MCSymbol *Grp = static_cast<const MCSectionELF *>(Section)->getGroup();
    118   if (Grp)
    119     getAssembler().getOrCreateSymbolData(*Grp);
    120   this->MCObjectStreamer::ChangeSection(Section, Subsection);
    121 }
    122 
    123 void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
    124   getAssembler().getOrCreateSymbolData(*Symbol);
    125   MCSymbolData &AliasSD = getAssembler().getOrCreateSymbolData(*Alias);
    126   AliasSD.setFlags(AliasSD.getFlags() | ELF_Other_Weakref);
    127   const MCExpr *Value = MCSymbolRefExpr::Create(Symbol, getContext());
    128   Alias->setVariableValue(Value);
    129 }
    130 
    131 // When GNU as encounters more than one .type declaration for an object it seems
    132 // to use a mechanism similar to the one below to decide which type is actually
    133 // used in the object file.  The greater of T1 and T2 is selected based on the
    134 // following ordering:
    135 //  STT_NOTYPE < STT_OBJECT < STT_FUNC < STT_GNU_IFUNC < STT_TLS < anything else
    136 // If neither T1 < T2 nor T2 < T1 according to this ordering, use T2 (the user
    137 // provided type).
    138 static unsigned CombineSymbolTypes(unsigned T1, unsigned T2) {
    139   unsigned TypeOrdering[] = {ELF::STT_NOTYPE, ELF::STT_OBJECT, ELF::STT_FUNC,
    140                              ELF::STT_GNU_IFUNC, ELF::STT_TLS};
    141   for (unsigned i = 0; i != array_lengthof(TypeOrdering); ++i) {
    142     if (T1 == TypeOrdering[i])
    143       return T2;
    144     if (T2 == TypeOrdering[i])
    145       return T1;
    146   }
    147 
    148   return T2;
    149 }
    150 
    151 void MCELFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
    152                                           MCSymbolAttr Attribute) {
    153   // Indirect symbols are handled differently, to match how 'as' handles
    154   // them. This makes writing matching .o files easier.
    155   if (Attribute == MCSA_IndirectSymbol) {
    156     // Note that we intentionally cannot use the symbol data here; this is
    157     // important for matching the string table that 'as' generates.
    158     IndirectSymbolData ISD;
    159     ISD.Symbol = Symbol;
    160     ISD.SectionData = getCurrentSectionData();
    161     getAssembler().getIndirectSymbols().push_back(ISD);
    162     return;
    163   }
    164 
    165   // Adding a symbol attribute always introduces the symbol, note that an
    166   // important side effect of calling getOrCreateSymbolData here is to register
    167   // the symbol with the assembler.
    168   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
    169 
    170   // The implementation of symbol attributes is designed to match 'as', but it
    171   // leaves much to desired. It doesn't really make sense to arbitrarily add and
    172   // remove flags, but 'as' allows this (in particular, see .desc).
    173   //
    174   // In the future it might be worth trying to make these operations more well
    175   // defined.
    176   switch (Attribute) {
    177   case MCSA_LazyReference:
    178   case MCSA_Reference:
    179   case MCSA_SymbolResolver:
    180   case MCSA_PrivateExtern:
    181   case MCSA_WeakDefinition:
    182   case MCSA_WeakDefAutoPrivate:
    183   case MCSA_Invalid:
    184   case MCSA_IndirectSymbol:
    185     llvm_unreachable("Invalid symbol attribute for ELF!");
    186 
    187   case MCSA_NoDeadStrip:
    188   case MCSA_ELF_TypeGnuUniqueObject:
    189     // Ignore for now.
    190     break;
    191 
    192   case MCSA_Global:
    193     MCELF::SetBinding(SD, ELF::STB_GLOBAL);
    194     SD.setExternal(true);
    195     BindingExplicitlySet.insert(Symbol);
    196     break;
    197 
    198   case MCSA_WeakReference:
    199   case MCSA_Weak:
    200     MCELF::SetBinding(SD, ELF::STB_WEAK);
    201     SD.setExternal(true);
    202     BindingExplicitlySet.insert(Symbol);
    203     break;
    204 
    205   case MCSA_Local:
    206     MCELF::SetBinding(SD, ELF::STB_LOCAL);
    207     SD.setExternal(false);
    208     BindingExplicitlySet.insert(Symbol);
    209     break;
    210 
    211   case MCSA_ELF_TypeFunction:
    212     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
    213                                           ELF::STT_FUNC));
    214     break;
    215 
    216   case MCSA_ELF_TypeIndFunction:
    217     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
    218                                           ELF::STT_GNU_IFUNC));
    219     break;
    220 
    221   case MCSA_ELF_TypeObject:
    222     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
    223                                           ELF::STT_OBJECT));
    224     break;
    225 
    226   case MCSA_ELF_TypeTLS:
    227     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
    228                                           ELF::STT_TLS));
    229     break;
    230 
    231   case MCSA_ELF_TypeCommon:
    232     // TODO: Emit these as a common symbol.
    233     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
    234                                           ELF::STT_OBJECT));
    235     break;
    236 
    237   case MCSA_ELF_TypeNoType:
    238     MCELF::SetType(SD, CombineSymbolTypes(MCELF::GetType(SD),
    239                                           ELF::STT_NOTYPE));
    240     break;
    241 
    242   case MCSA_Protected:
    243     MCELF::SetVisibility(SD, ELF::STV_PROTECTED);
    244     break;
    245 
    246   case MCSA_Hidden:
    247     MCELF::SetVisibility(SD, ELF::STV_HIDDEN);
    248     break;
    249 
    250   case MCSA_Internal:
    251     MCELF::SetVisibility(SD, ELF::STV_INTERNAL);
    252     break;
    253   }
    254 }
    255 
    256 void MCELFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    257                                        unsigned ByteAlignment) {
    258   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
    259 
    260   if (!BindingExplicitlySet.count(Symbol)) {
    261     MCELF::SetBinding(SD, ELF::STB_GLOBAL);
    262     SD.setExternal(true);
    263   }
    264 
    265   MCELF::SetType(SD, ELF::STT_OBJECT);
    266 
    267   if (MCELF::GetBinding(SD) == ELF_STB_Local) {
    268     const MCSection *Section = getAssembler().getContext().getELFSection(".bss",
    269                                                          ELF::SHT_NOBITS,
    270                                                          ELF::SHF_WRITE |
    271                                                          ELF::SHF_ALLOC,
    272                                                          SectionKind::getBSS());
    273     Symbol->setSection(*Section);
    274 
    275     struct LocalCommon L = {&SD, Size, ByteAlignment};
    276     LocalCommons.push_back(L);
    277   } else {
    278     SD.setCommon(Size, ByteAlignment);
    279   }
    280 
    281   SD.setSize(MCConstantExpr::Create(Size, getContext()));
    282 }
    283 
    284 void MCELFStreamer::EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
    285   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
    286   SD.setSize(Value);
    287 }
    288 
    289 void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    290                                           unsigned ByteAlignment) {
    291   // FIXME: Should this be caught and done earlier?
    292   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
    293   MCELF::SetBinding(SD, ELF::STB_LOCAL);
    294   SD.setExternal(false);
    295   BindingExplicitlySet.insert(Symbol);
    296   EmitCommonSymbol(Symbol, Size, ByteAlignment);
    297 }
    298 
    299 void MCELFStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size) {
    300   if (getCurrentSectionData()->isBundleLocked())
    301     report_fatal_error("Emitting values inside a locked bundle is forbidden");
    302   fixSymbolsInTLSFixups(Value);
    303   MCObjectStreamer::EmitValueImpl(Value, Size);
    304 }
    305 
    306 void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
    307                                          int64_t Value,
    308                                          unsigned ValueSize,
    309                                          unsigned MaxBytesToEmit) {
    310   if (getCurrentSectionData()->isBundleLocked())
    311     report_fatal_error("Emitting values inside a locked bundle is forbidden");
    312   MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value,
    313                                          ValueSize, MaxBytesToEmit);
    314 }
    315 
    316 
    317 // Add a symbol for the file name of this module. This is the second
    318 // entry in the module's symbol table (the first being the null symbol).
    319 void MCELFStreamer::EmitFileDirective(StringRef Filename) {
    320   MCSymbol *Symbol = getAssembler().getContext().GetOrCreateSymbol(Filename);
    321   Symbol->setSection(*getCurrentSection().first);
    322   Symbol->setAbsolute();
    323 
    324   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
    325 
    326   SD.setFlags(ELF_STT_File | ELF_STB_Local | ELF_STV_Default);
    327 }
    328 
    329 void  MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
    330   switch (expr->getKind()) {
    331   case MCExpr::Target:
    332     cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
    333     break;
    334   case MCExpr::Constant:
    335     break;
    336 
    337   case MCExpr::Binary: {
    338     const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
    339     fixSymbolsInTLSFixups(be->getLHS());
    340     fixSymbolsInTLSFixups(be->getRHS());
    341     break;
    342   }
    343 
    344   case MCExpr::SymbolRef: {
    345     const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
    346     switch (symRef.getKind()) {
    347     default:
    348       return;
    349     case MCSymbolRefExpr::VK_GOTTPOFF:
    350     case MCSymbolRefExpr::VK_INDNTPOFF:
    351     case MCSymbolRefExpr::VK_NTPOFF:
    352     case MCSymbolRefExpr::VK_GOTNTPOFF:
    353     case MCSymbolRefExpr::VK_TLSGD:
    354     case MCSymbolRefExpr::VK_TLSLD:
    355     case MCSymbolRefExpr::VK_TLSLDM:
    356     case MCSymbolRefExpr::VK_TPOFF:
    357     case MCSymbolRefExpr::VK_DTPOFF:
    358     case MCSymbolRefExpr::VK_ARM_TLSGD:
    359     case MCSymbolRefExpr::VK_ARM_TPOFF:
    360     case MCSymbolRefExpr::VK_ARM_GOTTPOFF:
    361     case MCSymbolRefExpr::VK_Mips_TLSGD:
    362     case MCSymbolRefExpr::VK_Mips_GOTTPREL:
    363     case MCSymbolRefExpr::VK_Mips_TPREL_HI:
    364     case MCSymbolRefExpr::VK_Mips_TPREL_LO:
    365     case MCSymbolRefExpr::VK_PPC_DTPMOD:
    366     case MCSymbolRefExpr::VK_PPC_TPREL:
    367     case MCSymbolRefExpr::VK_PPC_TPREL_LO:
    368     case MCSymbolRefExpr::VK_PPC_TPREL_HI:
    369     case MCSymbolRefExpr::VK_PPC_TPREL_HA:
    370     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
    371     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
    372     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
    373     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
    374     case MCSymbolRefExpr::VK_PPC_DTPREL:
    375     case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
    376     case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
    377     case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
    378     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
    379     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
    380     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
    381     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
    382     case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
    383     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
    384     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
    385     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
    386     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
    387     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
    388     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
    389     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
    390     case MCSymbolRefExpr::VK_PPC_TLS:
    391     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
    392     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
    393     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
    394     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
    395     case MCSymbolRefExpr::VK_PPC_TLSGD:
    396     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
    397     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
    398     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
    399     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
    400     case MCSymbolRefExpr::VK_PPC_TLSLD:
    401       break;
    402     }
    403     MCSymbolData &SD = getAssembler().getOrCreateSymbolData(symRef.getSymbol());
    404     MCELF::SetType(SD, ELF::STT_TLS);
    405     break;
    406   }
    407 
    408   case MCExpr::Unary:
    409     fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
    410     break;
    411   }
    412 }
    413 
    414 void MCELFStreamer::EmitInstToFragment(const MCInst &Inst) {
    415   this->MCObjectStreamer::EmitInstToFragment(Inst);
    416   MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
    417 
    418   for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
    419     fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
    420 }
    421 
    422 void MCELFStreamer::EmitInstToData(const MCInst &Inst) {
    423   MCAssembler &Assembler = getAssembler();
    424   SmallVector<MCFixup, 4> Fixups;
    425   SmallString<256> Code;
    426   raw_svector_ostream VecOS(Code);
    427   Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
    428   VecOS.flush();
    429 
    430   for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
    431     fixSymbolsInTLSFixups(Fixups[i].getValue());
    432 
    433   // There are several possibilities here:
    434   //
    435   // If bundling is disabled, append the encoded instruction to the current data
    436   // fragment (or create a new such fragment if the current fragment is not a
    437   // data fragment).
    438   //
    439   // If bundling is enabled:
    440   // - If we're not in a bundle-locked group, emit the instruction into a
    441   //   fragment of its own. If there are no fixups registered for the
    442   //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
    443   //   MCDataFragment.
    444   // - If we're in a bundle-locked group, append the instruction to the current
    445   //   data fragment because we want all the instructions in a group to get into
    446   //   the same fragment. Be careful not to do that for the first instruction in
    447   //   the group, though.
    448   MCDataFragment *DF;
    449 
    450   if (Assembler.isBundlingEnabled()) {
    451     MCSectionData *SD = getCurrentSectionData();
    452     if (SD->isBundleLocked() && !SD->isBundleGroupBeforeFirstInst())
    453       // If we are bundle-locked, we re-use the current fragment.
    454       // The bundle-locking directive ensures this is a new data fragment.
    455       DF = cast<MCDataFragment>(getCurrentFragment());
    456     else if (!SD->isBundleLocked() && Fixups.size() == 0) {
    457       // Optimize memory usage by emitting the instruction to a
    458       // MCCompactEncodedInstFragment when not in a bundle-locked group and
    459       // there are no fixups registered.
    460       MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
    461       insert(CEIF);
    462       CEIF->getContents().append(Code.begin(), Code.end());
    463       return;
    464     } else {
    465       DF = new MCDataFragment();
    466       insert(DF);
    467       if (SD->getBundleLockState() == MCSectionData::BundleLockedAlignToEnd) {
    468         // If this is a new fragment created for a bundle-locked group, and the
    469         // group was marked as "align_to_end", set a flag in the fragment.
    470         DF->setAlignToBundleEnd(true);
    471       }
    472     }
    473 
    474     // We're now emitting an instruction in a bundle group, so this flag has
    475     // to be turned off.
    476     SD->setBundleGroupBeforeFirstInst(false);
    477   } else {
    478     DF = getOrCreateDataFragment();
    479   }
    480 
    481   // Add the fixups and data.
    482   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
    483     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
    484     DF->getFixups().push_back(Fixups[i]);
    485   }
    486   DF->setHasInstructions(true);
    487   DF->getContents().append(Code.begin(), Code.end());
    488 }
    489 
    490 void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
    491   assert(AlignPow2 <= 30 && "Invalid bundle alignment");
    492   MCAssembler &Assembler = getAssembler();
    493   if (Assembler.getBundleAlignSize() == 0 && AlignPow2 > 0)
    494     Assembler.setBundleAlignSize(1 << AlignPow2);
    495   else
    496     report_fatal_error(".bundle_align_mode should be only set once per file");
    497 }
    498 
    499 void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
    500   MCSectionData *SD = getCurrentSectionData();
    501 
    502   // Sanity checks
    503   //
    504   if (!getAssembler().isBundlingEnabled())
    505     report_fatal_error(".bundle_lock forbidden when bundling is disabled");
    506   else if (SD->isBundleLocked())
    507     report_fatal_error("Nesting of .bundle_lock is forbidden");
    508 
    509   SD->setBundleLockState(AlignToEnd ? MCSectionData::BundleLockedAlignToEnd :
    510                                       MCSectionData::BundleLocked);
    511   SD->setBundleGroupBeforeFirstInst(true);
    512 }
    513 
    514 void MCELFStreamer::EmitBundleUnlock() {
    515   MCSectionData *SD = getCurrentSectionData();
    516 
    517   // Sanity checks
    518   if (!getAssembler().isBundlingEnabled())
    519     report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
    520   else if (!SD->isBundleLocked())
    521     report_fatal_error(".bundle_unlock without matching lock");
    522   else if (SD->isBundleGroupBeforeFirstInst())
    523     report_fatal_error("Empty bundle-locked group is forbidden");
    524 
    525   SD->setBundleLockState(MCSectionData::NotBundleLocked);
    526 }
    527 
    528 void MCELFStreamer::FinishImpl() {
    529   EmitFrames(true);
    530 
    531   for (std::vector<LocalCommon>::const_iterator i = LocalCommons.begin(),
    532                                                 e = LocalCommons.end();
    533        i != e; ++i) {
    534     MCSymbolData *SD = i->SD;
    535     uint64_t Size = i->Size;
    536     unsigned ByteAlignment = i->ByteAlignment;
    537     const MCSymbol &Symbol = SD->getSymbol();
    538     const MCSection &Section = Symbol.getSection();
    539 
    540     MCSectionData &SectData = getAssembler().getOrCreateSectionData(Section);
    541     new MCAlignFragment(ByteAlignment, 0, 1, ByteAlignment, &SectData);
    542 
    543     MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
    544     SD->setFragment(F);
    545 
    546     // Update the maximum alignment of the section if necessary.
    547     if (ByteAlignment > SectData.getAlignment())
    548       SectData.setAlignment(ByteAlignment);
    549   }
    550 
    551   this->MCObjectStreamer::FinishImpl();
    552 }
    553 void MCELFStreamer::EmitTCEntry(const MCSymbol &S) {
    554   // Creates a R_PPC64_TOC relocation
    555   MCObjectStreamer::EmitSymbolValue(&S, 8);
    556 }
    557 
    558 MCStreamer *llvm::createELFStreamer(MCContext &Context, MCAsmBackend &MAB,
    559                                     raw_ostream &OS, MCCodeEmitter *CE,
    560                                     bool RelaxAll, bool NoExecStack) {
    561   MCELFStreamer *S = new MCELFStreamer(Context, MAB, OS, CE);
    562   if (RelaxAll)
    563     S->getAssembler().setRelaxAll(true);
    564   if (NoExecStack)
    565     S->getAssembler().setNoExecStack(true);
    566   return S;
    567 }
    568 
    569 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
    570   llvm_unreachable("Generic ELF doesn't support this directive");
    571 }
    572 
    573 MCSymbolData &MCELFStreamer::getOrCreateSymbolData(MCSymbol *Symbol) {
    574   return getAssembler().getOrCreateSymbolData(*Symbol);
    575 }
    576 
    577 void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
    578   llvm_unreachable("ELF doesn't support this directive");
    579 }
    580 
    581 void MCELFStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
    582   llvm_unreachable("ELF doesn't support this directive");
    583 }
    584 
    585 void MCELFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
    586   llvm_unreachable("ELF doesn't support this directive");
    587 }
    588 
    589 void MCELFStreamer::EmitCOFFSymbolType(int Type) {
    590   llvm_unreachable("ELF doesn't support this directive");
    591 }
    592 
    593 void MCELFStreamer::EndCOFFSymbolDef() {
    594   llvm_unreachable("ELF doesn't support this directive");
    595 }
    596 
    597 void MCELFStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
    598                                  uint64_t Size, unsigned ByteAlignment) {
    599   llvm_unreachable("ELF doesn't support this directive");
    600 }
    601 
    602 void MCELFStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
    603                                    uint64_t Size, unsigned ByteAlignment) {
    604   llvm_unreachable("ELF doesn't support this directive");
    605 }
    606