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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/STLExtras.h"
     16 #include "llvm/ADT/SmallPtrSet.h"
     17 #include "llvm/MC/MCAsmBackend.h"
     18 #include "llvm/MC/MCAsmLayout.h"
     19 #include "llvm/MC/MCAsmInfo.h"
     20 #include "llvm/MC/MCAssembler.h"
     21 #include "llvm/MC/MCCodeEmitter.h"
     22 #include "llvm/MC/MCContext.h"
     23 #include "llvm/MC/MCExpr.h"
     24 #include "llvm/MC/MCInst.h"
     25 #include "llvm/MC/MCObjectFileInfo.h"
     26 #include "llvm/MC/MCObjectStreamer.h"
     27 #include "llvm/MC/MCObjectWriter.h"
     28 #include "llvm/MC/MCSection.h"
     29 #include "llvm/MC/MCSectionELF.h"
     30 #include "llvm/MC/MCSymbolELF.h"
     31 #include "llvm/MC/MCSymbol.h"
     32 #include "llvm/MC/MCValue.h"
     33 #include "llvm/Support/Debug.h"
     34 #include "llvm/Support/ELF.h"
     35 #include "llvm/Support/ErrorHandling.h"
     36 #include "llvm/Support/TargetRegistry.h"
     37 #include "llvm/Support/raw_ostream.h"
     38 
     39 using namespace llvm;
     40 
     41 bool MCELFStreamer::isBundleLocked() const {
     42   return getCurrentSectionOnly()->isBundleLocked();
     43 }
     44 
     45 MCELFStreamer::~MCELFStreamer() {
     46 }
     47 
     48 void MCELFStreamer::mergeFragment(MCDataFragment *DF,
     49                                   MCDataFragment *EF) {
     50   MCAssembler &Assembler = getAssembler();
     51 
     52   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
     53     uint64_t FSize = EF->getContents().size();
     54 
     55     if (FSize > Assembler.getBundleAlignSize())
     56       report_fatal_error("Fragment can't be larger than a bundle size");
     57 
     58     uint64_t RequiredBundlePadding = computeBundlePadding(
     59         Assembler, EF, DF->getContents().size(), FSize);
     60 
     61     if (RequiredBundlePadding > UINT8_MAX)
     62       report_fatal_error("Padding cannot exceed 255 bytes");
     63 
     64     if (RequiredBundlePadding > 0) {
     65       SmallString<256> Code;
     66       raw_svector_ostream VecOS(Code);
     67       MCObjectWriter *OW = Assembler.getBackend().createObjectWriter(VecOS);
     68 
     69       EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
     70 
     71       Assembler.writeFragmentPadding(*EF, FSize, OW);
     72       delete OW;
     73 
     74       DF->getContents().append(Code.begin(), Code.end());
     75     }
     76   }
     77 
     78   flushPendingLabels(DF, DF->getContents().size());
     79 
     80   for (unsigned i = 0, e = EF->getFixups().size(); i != e; ++i) {
     81     EF->getFixups()[i].setOffset(EF->getFixups()[i].getOffset() +
     82                                  DF->getContents().size());
     83     DF->getFixups().push_back(EF->getFixups()[i]);
     84   }
     85   DF->setHasInstructions(true);
     86   DF->getContents().append(EF->getContents().begin(), EF->getContents().end());
     87 }
     88 
     89 void MCELFStreamer::InitSections(bool NoExecStack) {
     90   MCContext &Ctx = getContext();
     91   SwitchSection(Ctx.getObjectFileInfo()->getTextSection());
     92   EmitCodeAlignment(4);
     93 
     94   if (NoExecStack)
     95     SwitchSection(Ctx.getAsmInfo()->getNonexecutableStackSection(Ctx));
     96 }
     97 
     98 void MCELFStreamer::EmitLabel(MCSymbol *S) {
     99   auto *Symbol = cast<MCSymbolELF>(S);
    100   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
    101 
    102   MCObjectStreamer::EmitLabel(Symbol);
    103 
    104   const MCSectionELF &Section =
    105       static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
    106   if (Section.getFlags() & ELF::SHF_TLS)
    107     Symbol->setType(ELF::STT_TLS);
    108 }
    109 
    110 void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
    111   // Let the target do whatever target specific stuff it needs to do.
    112   getAssembler().getBackend().handleAssemblerFlag(Flag);
    113   // Do any generic stuff we need to do.
    114   switch (Flag) {
    115   case MCAF_SyntaxUnified: return; // no-op here.
    116   case MCAF_Code16: return; // Change parsing mode; no-op here.
    117   case MCAF_Code32: return; // Change parsing mode; no-op here.
    118   case MCAF_Code64: return; // Change parsing mode; no-op here.
    119   case MCAF_SubsectionsViaSymbols:
    120     getAssembler().setSubsectionsViaSymbols(true);
    121     return;
    122   }
    123 
    124   llvm_unreachable("invalid assembler flag!");
    125 }
    126 
    127 // If bundle alignment is used and there are any instructions in the section, it
    128 // needs to be aligned to at least the bundle size.
    129 static void setSectionAlignmentForBundling(const MCAssembler &Assembler,
    130                                            MCSection *Section) {
    131   if (Section && Assembler.isBundlingEnabled() && Section->hasInstructions() &&
    132       Section->getAlignment() < Assembler.getBundleAlignSize())
    133     Section->setAlignment(Assembler.getBundleAlignSize());
    134 }
    135 
    136 void MCELFStreamer::ChangeSection(MCSection *Section,
    137                                   const MCExpr *Subsection) {
    138   MCSection *CurSection = getCurrentSectionOnly();
    139   if (CurSection && isBundleLocked())
    140     report_fatal_error("Unterminated .bundle_lock when changing a section");
    141 
    142   MCAssembler &Asm = getAssembler();
    143   // Ensure the previous section gets aligned if necessary.
    144   setSectionAlignmentForBundling(Asm, CurSection);
    145   auto *SectionELF = static_cast<const MCSectionELF *>(Section);
    146   const MCSymbol *Grp = SectionELF->getGroup();
    147   if (Grp)
    148     Asm.registerSymbol(*Grp);
    149 
    150   this->MCObjectStreamer::ChangeSection(Section, Subsection);
    151   MCContext &Ctx = getContext();
    152   auto *Begin = cast_or_null<MCSymbolELF>(Section->getBeginSymbol());
    153   if (!Begin) {
    154     Begin = Ctx.getOrCreateSectionSymbol(*SectionELF);
    155     Section->setBeginSymbol(Begin);
    156   }
    157   if (Begin->isUndefined()) {
    158     Asm.registerSymbol(*Begin);
    159     Begin->setType(ELF::STT_SECTION);
    160   }
    161 }
    162 
    163 void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
    164   getAssembler().registerSymbol(*Symbol);
    165   const MCExpr *Value = MCSymbolRefExpr::create(
    166       Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext());
    167   Alias->setVariableValue(Value);
    168 }
    169 
    170 // When GNU as encounters more than one .type declaration for an object it seems
    171 // to use a mechanism similar to the one below to decide which type is actually
    172 // used in the object file.  The greater of T1 and T2 is selected based on the
    173 // following ordering:
    174 //  STT_NOTYPE < STT_OBJECT < STT_FUNC < STT_GNU_IFUNC < STT_TLS < anything else
    175 // If neither T1 < T2 nor T2 < T1 according to this ordering, use T2 (the user
    176 // provided type).
    177 static unsigned CombineSymbolTypes(unsigned T1, unsigned T2) {
    178   for (unsigned Type : {ELF::STT_NOTYPE, ELF::STT_OBJECT, ELF::STT_FUNC,
    179                         ELF::STT_GNU_IFUNC, ELF::STT_TLS}) {
    180     if (T1 == Type)
    181       return T2;
    182     if (T2 == Type)
    183       return T1;
    184   }
    185 
    186   return T2;
    187 }
    188 
    189 bool MCELFStreamer::EmitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
    190   auto *Symbol = cast<MCSymbolELF>(S);
    191   // Indirect symbols are handled differently, to match how 'as' handles
    192   // them. This makes writing matching .o files easier.
    193   if (Attribute == MCSA_IndirectSymbol) {
    194     // Note that we intentionally cannot use the symbol data here; this is
    195     // important for matching the string table that 'as' generates.
    196     IndirectSymbolData ISD;
    197     ISD.Symbol = Symbol;
    198     ISD.Section = getCurrentSectionOnly();
    199     getAssembler().getIndirectSymbols().push_back(ISD);
    200     return true;
    201   }
    202 
    203   // Adding a symbol attribute always introduces the symbol, note that an
    204   // important side effect of calling registerSymbol here is to register
    205   // the symbol with the assembler.
    206   getAssembler().registerSymbol(*Symbol);
    207 
    208   // The implementation of symbol attributes is designed to match 'as', but it
    209   // leaves much to desired. It doesn't really make sense to arbitrarily add and
    210   // remove flags, but 'as' allows this (in particular, see .desc).
    211   //
    212   // In the future it might be worth trying to make these operations more well
    213   // defined.
    214   switch (Attribute) {
    215   case MCSA_LazyReference:
    216   case MCSA_Reference:
    217   case MCSA_SymbolResolver:
    218   case MCSA_PrivateExtern:
    219   case MCSA_WeakDefinition:
    220   case MCSA_WeakDefAutoPrivate:
    221   case MCSA_Invalid:
    222   case MCSA_IndirectSymbol:
    223     return false;
    224 
    225   case MCSA_NoDeadStrip:
    226     // Ignore for now.
    227     break;
    228 
    229   case MCSA_ELF_TypeGnuUniqueObject:
    230     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
    231     Symbol->setBinding(ELF::STB_GNU_UNIQUE);
    232     Symbol->setExternal(true);
    233     break;
    234 
    235   case MCSA_Global:
    236     Symbol->setBinding(ELF::STB_GLOBAL);
    237     Symbol->setExternal(true);
    238     break;
    239 
    240   case MCSA_WeakReference:
    241   case MCSA_Weak:
    242     Symbol->setBinding(ELF::STB_WEAK);
    243     Symbol->setExternal(true);
    244     break;
    245 
    246   case MCSA_Local:
    247     Symbol->setBinding(ELF::STB_LOCAL);
    248     Symbol->setExternal(false);
    249     break;
    250 
    251   case MCSA_ELF_TypeFunction:
    252     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_FUNC));
    253     break;
    254 
    255   case MCSA_ELF_TypeIndFunction:
    256     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_GNU_IFUNC));
    257     break;
    258 
    259   case MCSA_ELF_TypeObject:
    260     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
    261     break;
    262 
    263   case MCSA_ELF_TypeTLS:
    264     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_TLS));
    265     break;
    266 
    267   case MCSA_ELF_TypeCommon:
    268     // TODO: Emit these as a common symbol.
    269     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
    270     break;
    271 
    272   case MCSA_ELF_TypeNoType:
    273     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_NOTYPE));
    274     break;
    275 
    276   case MCSA_Protected:
    277     Symbol->setVisibility(ELF::STV_PROTECTED);
    278     break;
    279 
    280   case MCSA_Hidden:
    281     Symbol->setVisibility(ELF::STV_HIDDEN);
    282     break;
    283 
    284   case MCSA_Internal:
    285     Symbol->setVisibility(ELF::STV_INTERNAL);
    286     break;
    287 
    288   case MCSA_AltEntry:
    289     llvm_unreachable("ELF doesn't support the .alt_entry attribute");
    290   }
    291 
    292   return true;
    293 }
    294 
    295 void MCELFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
    296                                      unsigned ByteAlignment) {
    297   auto *Symbol = cast<MCSymbolELF>(S);
    298   getAssembler().registerSymbol(*Symbol);
    299 
    300   if (!Symbol->isBindingSet()) {
    301     Symbol->setBinding(ELF::STB_GLOBAL);
    302     Symbol->setExternal(true);
    303   }
    304 
    305   Symbol->setType(ELF::STT_OBJECT);
    306 
    307   if (Symbol->getBinding() == ELF::STB_LOCAL) {
    308     MCSection &Section = *getAssembler().getContext().getELFSection(
    309         ".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
    310     MCSectionSubPair P = getCurrentSection();
    311     SwitchSection(&Section);
    312 
    313     EmitValueToAlignment(ByteAlignment, 0, 1, 0);
    314     EmitLabel(Symbol);
    315     EmitZeros(Size);
    316 
    317     // Update the maximum alignment of the section if necessary.
    318     if (ByteAlignment > Section.getAlignment())
    319       Section.setAlignment(ByteAlignment);
    320 
    321     SwitchSection(P.first, P.second);
    322   } else {
    323     if(Symbol->declareCommon(Size, ByteAlignment))
    324       report_fatal_error("Symbol: " + Symbol->getName() +
    325                          " redeclared as different type");
    326   }
    327 
    328   cast<MCSymbolELF>(Symbol)
    329       ->setSize(MCConstantExpr::create(Size, getContext()));
    330 }
    331 
    332 void MCELFStreamer::emitELFSize(MCSymbolELF *Symbol, const MCExpr *Value) {
    333   Symbol->setSize(Value);
    334 }
    335 
    336 void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
    337                                           unsigned ByteAlignment) {
    338   auto *Symbol = cast<MCSymbolELF>(S);
    339   // FIXME: Should this be caught and done earlier?
    340   getAssembler().registerSymbol(*Symbol);
    341   Symbol->setBinding(ELF::STB_LOCAL);
    342   Symbol->setExternal(false);
    343   EmitCommonSymbol(Symbol, Size, ByteAlignment);
    344 }
    345 
    346 void MCELFStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
    347                                   SMLoc Loc) {
    348   if (isBundleLocked())
    349     report_fatal_error("Emitting values inside a locked bundle is forbidden");
    350   fixSymbolsInTLSFixups(Value);
    351   MCObjectStreamer::EmitValueImpl(Value, Size, Loc);
    352 }
    353 
    354 void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
    355                                          int64_t Value,
    356                                          unsigned ValueSize,
    357                                          unsigned MaxBytesToEmit) {
    358   if (isBundleLocked())
    359     report_fatal_error("Emitting values inside a locked bundle is forbidden");
    360   MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value,
    361                                          ValueSize, MaxBytesToEmit);
    362 }
    363 
    364 // Add a symbol for the file name of this module. They start after the
    365 // null symbol and don't count as normal symbol, i.e. a non-STT_FILE symbol
    366 // with the same name may appear.
    367 void MCELFStreamer::EmitFileDirective(StringRef Filename) {
    368   getAssembler().addFileName(Filename);
    369 }
    370 
    371 void MCELFStreamer::EmitIdent(StringRef IdentString) {
    372   MCSection *Comment = getAssembler().getContext().getELFSection(
    373       ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
    374   PushSection();
    375   SwitchSection(Comment);
    376   if (!SeenIdent) {
    377     EmitIntValue(0, 1);
    378     SeenIdent = true;
    379   }
    380   EmitBytes(IdentString);
    381   EmitIntValue(0, 1);
    382   PopSection();
    383 }
    384 
    385 void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
    386   switch (expr->getKind()) {
    387   case MCExpr::Target:
    388     cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
    389     break;
    390   case MCExpr::Constant:
    391     break;
    392 
    393   case MCExpr::Binary: {
    394     const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
    395     fixSymbolsInTLSFixups(be->getLHS());
    396     fixSymbolsInTLSFixups(be->getRHS());
    397     break;
    398   }
    399 
    400   case MCExpr::SymbolRef: {
    401     const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
    402     switch (symRef.getKind()) {
    403     default:
    404       return;
    405     case MCSymbolRefExpr::VK_GOTTPOFF:
    406     case MCSymbolRefExpr::VK_INDNTPOFF:
    407     case MCSymbolRefExpr::VK_NTPOFF:
    408     case MCSymbolRefExpr::VK_GOTNTPOFF:
    409     case MCSymbolRefExpr::VK_TLSGD:
    410     case MCSymbolRefExpr::VK_TLSLD:
    411     case MCSymbolRefExpr::VK_TLSLDM:
    412     case MCSymbolRefExpr::VK_TPOFF:
    413     case MCSymbolRefExpr::VK_TPREL:
    414     case MCSymbolRefExpr::VK_DTPOFF:
    415     case MCSymbolRefExpr::VK_DTPREL:
    416     case MCSymbolRefExpr::VK_PPC_DTPMOD:
    417     case MCSymbolRefExpr::VK_PPC_TPREL_LO:
    418     case MCSymbolRefExpr::VK_PPC_TPREL_HI:
    419     case MCSymbolRefExpr::VK_PPC_TPREL_HA:
    420     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
    421     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
    422     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
    423     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
    424     case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
    425     case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
    426     case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
    427     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
    428     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
    429     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
    430     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
    431     case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
    432     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
    433     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
    434     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
    435     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
    436     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
    437     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
    438     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
    439     case MCSymbolRefExpr::VK_PPC_TLS:
    440     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
    441     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
    442     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
    443     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
    444     case MCSymbolRefExpr::VK_PPC_TLSGD:
    445     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
    446     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
    447     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
    448     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
    449     case MCSymbolRefExpr::VK_PPC_TLSLD:
    450       break;
    451     }
    452     getAssembler().registerSymbol(symRef.getSymbol());
    453     cast<MCSymbolELF>(symRef.getSymbol()).setType(ELF::STT_TLS);
    454     break;
    455   }
    456 
    457   case MCExpr::Unary:
    458     fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
    459     break;
    460   }
    461 }
    462 
    463 void MCELFStreamer::EmitInstToFragment(const MCInst &Inst,
    464                                        const MCSubtargetInfo &STI) {
    465   this->MCObjectStreamer::EmitInstToFragment(Inst, STI);
    466   MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
    467 
    468   for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
    469     fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
    470 }
    471 
    472 void MCELFStreamer::EmitInstToData(const MCInst &Inst,
    473                                    const MCSubtargetInfo &STI) {
    474   MCAssembler &Assembler = getAssembler();
    475   SmallVector<MCFixup, 4> Fixups;
    476   SmallString<256> Code;
    477   raw_svector_ostream VecOS(Code);
    478   Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
    479 
    480   for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
    481     fixSymbolsInTLSFixups(Fixups[i].getValue());
    482 
    483   // There are several possibilities here:
    484   //
    485   // If bundling is disabled, append the encoded instruction to the current data
    486   // fragment (or create a new such fragment if the current fragment is not a
    487   // data fragment).
    488   //
    489   // If bundling is enabled:
    490   // - If we're not in a bundle-locked group, emit the instruction into a
    491   //   fragment of its own. If there are no fixups registered for the
    492   //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
    493   //   MCDataFragment.
    494   // - If we're in a bundle-locked group, append the instruction to the current
    495   //   data fragment because we want all the instructions in a group to get into
    496   //   the same fragment. Be careful not to do that for the first instruction in
    497   //   the group, though.
    498   MCDataFragment *DF;
    499 
    500   if (Assembler.isBundlingEnabled()) {
    501     MCSection &Sec = *getCurrentSectionOnly();
    502     if (Assembler.getRelaxAll() && isBundleLocked())
    503       // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
    504       // the current bundle group.
    505       DF = BundleGroups.back();
    506     else if (Assembler.getRelaxAll() && !isBundleLocked())
    507       // When not in a bundle-locked group and the -mc-relax-all flag is used,
    508       // we create a new temporary fragment which will be later merged into
    509       // the current fragment.
    510       DF = new MCDataFragment();
    511     else if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst())
    512       // If we are bundle-locked, we re-use the current fragment.
    513       // The bundle-locking directive ensures this is a new data fragment.
    514       DF = cast<MCDataFragment>(getCurrentFragment());
    515     else if (!isBundleLocked() && Fixups.size() == 0) {
    516       // Optimize memory usage by emitting the instruction to a
    517       // MCCompactEncodedInstFragment when not in a bundle-locked group and
    518       // there are no fixups registered.
    519       MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
    520       insert(CEIF);
    521       CEIF->getContents().append(Code.begin(), Code.end());
    522       return;
    523     } else {
    524       DF = new MCDataFragment();
    525       insert(DF);
    526     }
    527     if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
    528       // If this fragment is for a group marked "align_to_end", set a flag
    529       // in the fragment. This can happen after the fragment has already been
    530       // created if there are nested bundle_align groups and an inner one
    531       // is the one marked align_to_end.
    532       DF->setAlignToBundleEnd(true);
    533     }
    534 
    535     // We're now emitting an instruction in a bundle group, so this flag has
    536     // to be turned off.
    537     Sec.setBundleGroupBeforeFirstInst(false);
    538   } else {
    539     DF = getOrCreateDataFragment();
    540   }
    541 
    542   // Add the fixups and data.
    543   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
    544     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
    545     DF->getFixups().push_back(Fixups[i]);
    546   }
    547   DF->setHasInstructions(true);
    548   DF->getContents().append(Code.begin(), Code.end());
    549 
    550   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
    551     if (!isBundleLocked()) {
    552       mergeFragment(getOrCreateDataFragment(), DF);
    553       delete DF;
    554     }
    555   }
    556 }
    557 
    558 void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
    559   assert(AlignPow2 <= 30 && "Invalid bundle alignment");
    560   MCAssembler &Assembler = getAssembler();
    561   if (AlignPow2 > 0 && (Assembler.getBundleAlignSize() == 0 ||
    562                         Assembler.getBundleAlignSize() == 1U << AlignPow2))
    563     Assembler.setBundleAlignSize(1U << AlignPow2);
    564   else
    565     report_fatal_error(".bundle_align_mode cannot be changed once set");
    566 }
    567 
    568 void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
    569   MCSection &Sec = *getCurrentSectionOnly();
    570 
    571   // Sanity checks
    572   //
    573   if (!getAssembler().isBundlingEnabled())
    574     report_fatal_error(".bundle_lock forbidden when bundling is disabled");
    575 
    576   if (!isBundleLocked())
    577     Sec.setBundleGroupBeforeFirstInst(true);
    578 
    579   if (getAssembler().getRelaxAll() && !isBundleLocked()) {
    580     // TODO: drop the lock state and set directly in the fragment
    581     MCDataFragment *DF = new MCDataFragment();
    582     BundleGroups.push_back(DF);
    583   }
    584 
    585   Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
    586                                     : MCSection::BundleLocked);
    587 }
    588 
    589 void MCELFStreamer::EmitBundleUnlock() {
    590   MCSection &Sec = *getCurrentSectionOnly();
    591 
    592   // Sanity checks
    593   if (!getAssembler().isBundlingEnabled())
    594     report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
    595   else if (!isBundleLocked())
    596     report_fatal_error(".bundle_unlock without matching lock");
    597   else if (Sec.isBundleGroupBeforeFirstInst())
    598     report_fatal_error("Empty bundle-locked group is forbidden");
    599 
    600   // When the -mc-relax-all flag is used, we emit instructions to fragments
    601   // stored on a stack. When the bundle unlock is emitted, we pop a fragment
    602   // from the stack a merge it to the one below.
    603   if (getAssembler().getRelaxAll()) {
    604     assert(!BundleGroups.empty() && "There are no bundle groups");
    605     MCDataFragment *DF = BundleGroups.back();
    606 
    607     // FIXME: Use BundleGroups to track the lock state instead.
    608     Sec.setBundleLockState(MCSection::NotBundleLocked);
    609 
    610     // FIXME: Use more separate fragments for nested groups.
    611     if (!isBundleLocked()) {
    612       mergeFragment(getOrCreateDataFragment(), DF);
    613       BundleGroups.pop_back();
    614       delete DF;
    615     }
    616 
    617     if (Sec.getBundleLockState() != MCSection::BundleLockedAlignToEnd)
    618       getOrCreateDataFragment()->setAlignToBundleEnd(false);
    619   } else
    620     Sec.setBundleLockState(MCSection::NotBundleLocked);
    621 }
    622 
    623 void MCELFStreamer::FinishImpl() {
    624   // Ensure the last section gets aligned if necessary.
    625   MCSection *CurSection = getCurrentSectionOnly();
    626   setSectionAlignmentForBundling(getAssembler(), CurSection);
    627 
    628   EmitFrames(nullptr);
    629 
    630   this->MCObjectStreamer::FinishImpl();
    631 }
    632 
    633 MCStreamer *llvm::createELFStreamer(MCContext &Context, MCAsmBackend &MAB,
    634                                     raw_pwrite_stream &OS, MCCodeEmitter *CE,
    635                                     bool RelaxAll) {
    636   MCELFStreamer *S = new MCELFStreamer(Context, MAB, OS, CE);
    637   if (RelaxAll)
    638     S->getAssembler().setRelaxAll(true);
    639   return S;
    640 }
    641 
    642 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
    643   llvm_unreachable("Generic ELF doesn't support this directive");
    644 }
    645 
    646 void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
    647   llvm_unreachable("ELF doesn't support this directive");
    648 }
    649 
    650 void MCELFStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
    651   llvm_unreachable("ELF doesn't support this directive");
    652 }
    653 
    654 void MCELFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
    655   llvm_unreachable("ELF doesn't support this directive");
    656 }
    657 
    658 void MCELFStreamer::EmitCOFFSymbolType(int Type) {
    659   llvm_unreachable("ELF doesn't support this directive");
    660 }
    661 
    662 void MCELFStreamer::EndCOFFSymbolDef() {
    663   llvm_unreachable("ELF doesn't support this directive");
    664 }
    665 
    666 void MCELFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
    667                                  uint64_t Size, unsigned ByteAlignment) {
    668   llvm_unreachable("ELF doesn't support this directive");
    669 }
    670 
    671 void MCELFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
    672                                    uint64_t Size, unsigned ByteAlignment) {
    673   llvm_unreachable("ELF doesn't support this directive");
    674 }
    675