lib/MC/MCELFStreamer.cpp

   1 //===- lib/MC/MCELFStreamer.cpp - ELF Object Output -----------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file assembles .s files and emits ELF .o object files.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/MC/MCELFStreamer.h"
  14 #include "llvm/ADT/SmallString.h"
  15 #include "llvm/ADT/SmallVector.h"
  16 #include "llvm/BinaryFormat/ELF.h"
  17 #include "llvm/MC/MCAsmBackend.h"
  18 #include "llvm/MC/MCAsmInfo.h"
  19 #include "llvm/MC/MCAssembler.h"
  20 #include "llvm/MC/MCCodeEmitter.h"
  21 #include "llvm/MC/MCContext.h"
  22 #include "llvm/MC/MCExpr.h"
  23 #include "llvm/MC/MCFixup.h"
  24 #include "llvm/MC/MCFragment.h"
  25 #include "llvm/MC/MCObjectFileInfo.h"
  26 #include "llvm/MC/MCObjectWriter.h"
  27 #include "llvm/MC/MCSection.h"
  28 #include "llvm/MC/MCSectionELF.h"
  29 #include "llvm/MC/MCStreamer.h"
  30 #include "llvm/MC/MCSymbol.h"
  31 #include "llvm/MC/MCSymbolELF.h"
  32 #include "llvm/Support/Casting.h"
  33 #include "llvm/Support/ErrorHandling.h"
  34 #include "llvm/Support/TargetRegistry.h"
  35 #include "llvm/Support/raw_ostream.h"
  36 #include <cassert>
  37 #include <cstdint>
  38
  39 using namespace llvm;
  40
  41 MCELFStreamer::MCELFStreamer(MCContext &Context,
  42                              std::unique_ptr<MCAsmBackend> TAB,
  43                              std::unique_ptr<MCObjectWriter> OW,
  44                              std::unique_ptr<MCCodeEmitter> Emitter)
  45     : MCObjectStreamer(Context, std::move(TAB), std::move(OW),
  46                        std::move(Emitter)) {}
  47
  48 bool MCELFStreamer::isBundleLocked() const {
  49   return getCurrentSectionOnly()->isBundleLocked();
  50 }
  51
  52 void MCELFStreamer::mergeFragment(MCDataFragment *DF,
  53                                   MCDataFragment *EF) {
  54   MCAssembler &Assembler = getAssembler();
  55
  56   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
  57     uint64_t FSize = EF->getContents().size();
  58
  59     if (FSize > Assembler.getBundleAlignSize())
  60       report_fatal_error("Fragment can't be larger than a bundle size");
  61
  62     uint64_t RequiredBundlePadding = computeBundlePadding(
  63         Assembler, EF, DF->getContents().size(), FSize);
  64
  65     if (RequiredBundlePadding > UINT8_MAX)
  66       report_fatal_error("Padding cannot exceed 255 bytes");
  67
  68     if (RequiredBundlePadding > 0) {
  69       SmallString<256> Code;
  70       raw_svector_ostream VecOS(Code);
  71       EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
  72       Assembler.writeFragmentPadding(VecOS, *EF, FSize);
  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   if (DF->getSubtargetInfo() == nullptr && EF->getSubtargetInfo())
  86     DF->setHasInstructions(*EF->getSubtargetInfo());
  87   DF->getContents().append(EF->getContents().begin(), EF->getContents().end());
  88 }
  89
  90 void MCELFStreamer::InitSections(bool NoExecStack) {
  91   MCContext &Ctx = getContext();
  92   SwitchSection(Ctx.getObjectFileInfo()->getTextSection());
  93   EmitCodeAlignment(4);
  94
  95   if (NoExecStack)
  96     SwitchSection(Ctx.getAsmInfo()->getNonexecutableStackSection(Ctx));
  97 }
  98
  99 void MCELFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc) {
 100   auto *Symbol = cast<MCSymbolELF>(S);
 101   MCObjectStreamer::EmitLabel(Symbol, Loc);
 102
 103   const MCSectionELF &Section =
 104       static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
 105   if (Section.getFlags() & ELF::SHF_TLS)
 106     Symbol->setType(ELF::STT_TLS);
 107 }
 108
 109 void MCELFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc, MCFragment *F) {
 110   auto *Symbol = cast<MCSymbolELF>(S);
 111   MCObjectStreamer::EmitLabel(Symbol, Loc, F);
 112
 113   const MCSectionELF &Section =
 114       static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
 115   if (Section.getFlags() & ELF::SHF_TLS)
 116     Symbol->setType(ELF::STT_TLS);
 117 }
 118
 119 void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
 120   // Let the target do whatever target specific stuff it needs to do.
 121   getAssembler().getBackend().handleAssemblerFlag(Flag);
 122   // Do any generic stuff we need to do.
 123   switch (Flag) {
 124   case MCAF_SyntaxUnified: return; // no-op here.
 125   case MCAF_Code16: return; // Change parsing mode; no-op here.
 126   case MCAF_Code32: return; // Change parsing mode; no-op here.
 127   case MCAF_Code64: return; // Change parsing mode; no-op here.
 128   case MCAF_SubsectionsViaSymbols:
 129     getAssembler().setSubsectionsViaSymbols(true);
 130     return;
 131   }
 132
 133   llvm_unreachable("invalid assembler flag!");
 134 }
 135
 136 // If bundle alignment is used and there are any instructions in the section, it
 137 // needs to be aligned to at least the bundle size.
 138 static void setSectionAlignmentForBundling(const MCAssembler &Assembler,
 139                                            MCSection *Section) {
 140   if (Section && Assembler.isBundlingEnabled() && Section->hasInstructions() &&
 141       Section->getAlignment() < Assembler.getBundleAlignSize())
 142     Section->setAlignment(Align(Assembler.getBundleAlignSize()));
 143 }
 144
 145 void MCELFStreamer::ChangeSection(MCSection *Section,
 146                                   const MCExpr *Subsection) {
 147   MCSection *CurSection = getCurrentSectionOnly();
 148   if (CurSection && isBundleLocked())
 149     report_fatal_error("Unterminated .bundle_lock when changing a section");
 150
 151   MCAssembler &Asm = getAssembler();
 152   // Ensure the previous section gets aligned if necessary.
 153   setSectionAlignmentForBundling(Asm, CurSection);
 154   auto *SectionELF = static_cast<const MCSectionELF *>(Section);
 155   const MCSymbol *Grp = SectionELF->getGroup();
 156   if (Grp)
 157     Asm.registerSymbol(*Grp);
 158
 159   changeSectionImpl(Section, Subsection);
 160   Asm.registerSymbol(*Section->getBeginSymbol());
 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
 192   // Adding a symbol attribute always introduces the symbol, note that an
 193   // important side effect of calling registerSymbol here is to register
 194   // the symbol with the assembler.
 195   getAssembler().registerSymbol(*Symbol);
 196
 197   // The implementation of symbol attributes is designed to match 'as', but it
 198   // leaves much to desired. It doesn't really make sense to arbitrarily add and
 199   // remove flags, but 'as' allows this (in particular, see .desc).
 200   //
 201   // In the future it might be worth trying to make these operations more well
 202   // defined.
 203   switch (Attribute) {
 204   case MCSA_Cold:
 205   case MCSA_LazyReference:
 206   case MCSA_Reference:
 207   case MCSA_SymbolResolver:
 208   case MCSA_PrivateExtern:
 209   case MCSA_WeakDefinition:
 210   case MCSA_WeakDefAutoPrivate:
 211   case MCSA_Invalid:
 212   case MCSA_IndirectSymbol:
 213     return false;
 214
 215   case MCSA_NoDeadStrip:
 216     // Ignore for now.
 217     break;
 218
 219   case MCSA_ELF_TypeGnuUniqueObject:
 220     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
 221     Symbol->setBinding(ELF::STB_GNU_UNIQUE);
 222     Symbol->setExternal(true);
 223     break;
 224
 225   case MCSA_Global:
 226     Symbol->setBinding(ELF::STB_GLOBAL);
 227     Symbol->setExternal(true);
 228     break;
 229
 230   case MCSA_WeakReference:
 231   case MCSA_Weak:
 232     Symbol->setBinding(ELF::STB_WEAK);
 233     Symbol->setExternal(true);
 234     break;
 235
 236   case MCSA_Local:
 237     Symbol->setBinding(ELF::STB_LOCAL);
 238     Symbol->setExternal(false);
 239     break;
 240
 241   case MCSA_ELF_TypeFunction:
 242     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_FUNC));
 243     break;
 244
 245   case MCSA_ELF_TypeIndFunction:
 246     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_GNU_IFUNC));
 247     break;
 248
 249   case MCSA_ELF_TypeObject:
 250     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
 251     break;
 252
 253   case MCSA_ELF_TypeTLS:
 254     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_TLS));
 255     break;
 256
 257   case MCSA_ELF_TypeCommon:
 258     // TODO: Emit these as a common symbol.
 259     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
 260     break;
 261
 262   case MCSA_ELF_TypeNoType:
 263     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_NOTYPE));
 264     break;
 265
 266   case MCSA_Protected:
 267     Symbol->setVisibility(ELF::STV_PROTECTED);
 268     break;
 269
 270   case MCSA_Hidden:
 271     Symbol->setVisibility(ELF::STV_HIDDEN);
 272     break;
 273
 274   case MCSA_Internal:
 275     Symbol->setVisibility(ELF::STV_INTERNAL);
 276     break;
 277
 278   case MCSA_AltEntry:
 279     llvm_unreachable("ELF doesn't support the .alt_entry attribute");
 280
 281   case MCSA_LGlobal:
 282     llvm_unreachable("ELF doesn't support the .lglobl attribute");
 283   }
 284
 285   return true;
 286 }
 287
 288 void MCELFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
 289                                      unsigned ByteAlignment) {
 290   auto *Symbol = cast<MCSymbolELF>(S);
 291   getAssembler().registerSymbol(*Symbol);
 292
 293   if (!Symbol->isBindingSet()) {
 294     Symbol->setBinding(ELF::STB_GLOBAL);
 295     Symbol->setExternal(true);
 296   }
 297
 298   Symbol->setType(ELF::STT_OBJECT);
 299
 300   if (Symbol->getBinding() == ELF::STB_LOCAL) {
 301     MCSection &Section = *getAssembler().getContext().getELFSection(
 302         ".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
 303     MCSectionSubPair P = getCurrentSection();
 304     SwitchSection(&Section);
 305
 306     EmitValueToAlignment(ByteAlignment, 0, 1, 0);
 307     EmitLabel(Symbol);
 308     EmitZeros(Size);
 309
 310     // Update the maximum alignment of the section if necessary.
 311     if (ByteAlignment > Section.getAlignment())
 312       Section.setAlignment(Align(ByteAlignment));
 313
 314     SwitchSection(P.first, P.second);
 315   } else {
 316     if(Symbol->declareCommon(Size, ByteAlignment))
 317       report_fatal_error("Symbol: " + Symbol->getName() +
 318                          " redeclared as different type");
 319   }
 320
 321   cast<MCSymbolELF>(Symbol)
 322       ->setSize(MCConstantExpr::create(Size, getContext()));
 323 }
 324
 325 void MCELFStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
 326   cast<MCSymbolELF>(Symbol)->setSize(Value);
 327 }
 328
 329 void MCELFStreamer::emitELFSymverDirective(StringRef AliasName,
 330                                            const MCSymbol *Aliasee) {
 331   getAssembler().Symvers.push_back({AliasName, Aliasee});
 332 }
 333
 334 void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
 335                                           unsigned ByteAlignment) {
 336   auto *Symbol = cast<MCSymbolELF>(S);
 337   // FIXME: Should this be caught and done earlier?
 338   getAssembler().registerSymbol(*Symbol);
 339   Symbol->setBinding(ELF::STB_LOCAL);
 340   Symbol->setExternal(false);
 341   EmitCommonSymbol(Symbol, Size, ByteAlignment);
 342 }
 343
 344 void MCELFStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
 345                                   SMLoc Loc) {
 346   if (isBundleLocked())
 347     report_fatal_error("Emitting values inside a locked bundle is forbidden");
 348   fixSymbolsInTLSFixups(Value);
 349   MCObjectStreamer::EmitValueImpl(Value, Size, Loc);
 350 }
 351
 352 void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
 353                                          int64_t Value,
 354                                          unsigned ValueSize,
 355                                          unsigned MaxBytesToEmit) {
 356   if (isBundleLocked())
 357     report_fatal_error("Emitting values inside a locked bundle is forbidden");
 358   MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value,
 359                                          ValueSize, MaxBytesToEmit);
 360 }
 361
 362 void MCELFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
 363                                        const MCSymbolRefExpr *To,
 364                                        uint64_t Count) {
 365   getAssembler().CGProfile.push_back({From, To, Count});
 366 }
 367
 368 void MCELFStreamer::EmitIdent(StringRef IdentString) {
 369   MCSection *Comment = getAssembler().getContext().getELFSection(
 370       ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
 371   PushSection();
 372   SwitchSection(Comment);
 373   if (!SeenIdent) {
 374     EmitIntValue(0, 1);
 375     SeenIdent = true;
 376   }
 377   EmitBytes(IdentString);
 378   EmitIntValue(0, 1);
 379   PopSection();
 380 }
 381
 382 void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
 383   switch (expr->getKind()) {
 384   case MCExpr::Target:
 385     cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
 386     break;
 387   case MCExpr::Constant:
 388     break;
 389
 390   case MCExpr::Binary: {
 391     const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
 392     fixSymbolsInTLSFixups(be->getLHS());
 393     fixSymbolsInTLSFixups(be->getRHS());
 394     break;
 395   }
 396
 397   case MCExpr::SymbolRef: {
 398     const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
 399     switch (symRef.getKind()) {
 400     default:
 401       return;
 402     case MCSymbolRefExpr::VK_GOTTPOFF:
 403     case MCSymbolRefExpr::VK_INDNTPOFF:
 404     case MCSymbolRefExpr::VK_NTPOFF:
 405     case MCSymbolRefExpr::VK_GOTNTPOFF:
 406     case MCSymbolRefExpr::VK_TLSCALL:
 407     case MCSymbolRefExpr::VK_TLSDESC:
 408     case MCSymbolRefExpr::VK_TLSGD:
 409     case MCSymbolRefExpr::VK_TLSLD:
 410     case MCSymbolRefExpr::VK_TLSLDM:
 411     case MCSymbolRefExpr::VK_TPOFF:
 412     case MCSymbolRefExpr::VK_TPREL:
 413     case MCSymbolRefExpr::VK_DTPOFF:
 414     case MCSymbolRefExpr::VK_DTPREL:
 415     case MCSymbolRefExpr::VK_PPC_DTPMOD:
 416     case MCSymbolRefExpr::VK_PPC_TPREL_LO:
 417     case MCSymbolRefExpr::VK_PPC_TPREL_HI:
 418     case MCSymbolRefExpr::VK_PPC_TPREL_HA:
 419     case MCSymbolRefExpr::VK_PPC_TPREL_HIGH:
 420     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHA:
 421     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
 422     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
 423     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
 424     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
 425     case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
 426     case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
 427     case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
 428     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGH:
 429     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHA:
 430     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
 431     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
 432     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
 433     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
 434     case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
 435     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
 436     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
 437     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
 438     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
 439     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
 440     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
 441     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
 442     case MCSymbolRefExpr::VK_PPC_TLS:
 443     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
 444     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
 445     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
 446     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
 447     case MCSymbolRefExpr::VK_PPC_TLSGD:
 448     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
 449     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
 450     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
 451     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
 452     case MCSymbolRefExpr::VK_PPC_TLSLD:
 453       break;
 454     }
 455     getAssembler().registerSymbol(symRef.getSymbol());
 456     cast<MCSymbolELF>(symRef.getSymbol()).setType(ELF::STT_TLS);
 457     break;
 458   }
 459
 460   case MCExpr::Unary:
 461     fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
 462     break;
 463   }
 464 }
 465
 466 void MCELFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
 467   const MCSymbol *S = &SRE->getSymbol();
 468   if (S->isTemporary()) {
 469     if (!S->isInSection()) {
 470       getContext().reportError(
 471           SRE->getLoc(), Twine("Reference to undefined temporary symbol ") +
 472                              "`" + S->getName() + "`");
 473       return;
 474     }
 475     S = S->getSection().getBeginSymbol();
 476     S->setUsedInReloc();
 477     SRE =
 478         MCSymbolRefExpr::create(S, SRE->getKind(), getContext(), SRE->getLoc());
 479     return;
 480   }
 481   // Not a temporary, referece it as a weak undefined.
 482   bool Created;
 483   getAssembler().registerSymbol(*S, &Created);
 484   if (Created) {
 485     cast<MCSymbolELF>(S)->setBinding(ELF::STB_WEAK);
 486     cast<MCSymbolELF>(S)->setExternal(true);
 487   }
 488 }
 489
 490 void MCELFStreamer::finalizeCGProfile() {
 491   for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
 492     finalizeCGProfileEntry(E.From);
 493     finalizeCGProfileEntry(E.To);
 494   }
 495 }
 496
 497 void MCELFStreamer::EmitInstToFragment(const MCInst &Inst,
 498                                        const MCSubtargetInfo &STI) {
 499   this->MCObjectStreamer::EmitInstToFragment(Inst, STI);
 500   MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
 501
 502   for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
 503     fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
 504 }
 505
 506 // A fragment can only have one Subtarget, and when bundling is enabled we
 507 // sometimes need to use the same fragment. We give an error if there
 508 // are conflicting Subtargets.
 509 static void CheckBundleSubtargets(const MCSubtargetInfo *OldSTI,
 510                                   const MCSubtargetInfo *NewSTI) {
 511   if (OldSTI && NewSTI && OldSTI != NewSTI)
 512     report_fatal_error("A Bundle can only have one Subtarget.");
 513 }
 514
 515 void MCELFStreamer::EmitInstToData(const MCInst &Inst,
 516                                    const MCSubtargetInfo &STI) {
 517   MCAssembler &Assembler = getAssembler();
 518   SmallVector<MCFixup, 4> Fixups;
 519   SmallString<256> Code;
 520   raw_svector_ostream VecOS(Code);
 521   Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
 522
 523   for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
 524     fixSymbolsInTLSFixups(Fixups[i].getValue());
 525
 526   // There are several possibilities here:
 527   //
 528   // If bundling is disabled, append the encoded instruction to the current data
 529   // fragment (or create a new such fragment if the current fragment is not a
 530   // data fragment, or the Subtarget has changed).
 531   //
 532   // If bundling is enabled:
 533   // - If we're not in a bundle-locked group, emit the instruction into a
 534   //   fragment of its own. If there are no fixups registered for the
 535   //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
 536   //   MCDataFragment.
 537   // - If we're in a bundle-locked group, append the instruction to the current
 538   //   data fragment because we want all the instructions in a group to get into
 539   //   the same fragment. Be careful not to do that for the first instruction in
 540   //   the group, though.
 541   MCDataFragment *DF;
 542
 543   if (Assembler.isBundlingEnabled()) {
 544     MCSection &Sec = *getCurrentSectionOnly();
 545     if (Assembler.getRelaxAll() && isBundleLocked()) {
 546       // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
 547       // the current bundle group.
 548       DF = BundleGroups.back();
 549       CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
 550     }
 551     else if (Assembler.getRelaxAll() && !isBundleLocked())
 552       // When not in a bundle-locked group and the -mc-relax-all flag is used,
 553       // we create a new temporary fragment which will be later merged into
 554       // the current fragment.
 555       DF = new MCDataFragment();
 556     else if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst()) {
 557       // If we are bundle-locked, we re-use the current fragment.
 558       // The bundle-locking directive ensures this is a new data fragment.
 559       DF = cast<MCDataFragment>(getCurrentFragment());
 560       CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
 561     }
 562     else if (!isBundleLocked() && Fixups.size() == 0) {
 563       // Optimize memory usage by emitting the instruction to a
 564       // MCCompactEncodedInstFragment when not in a bundle-locked group and
 565       // there are no fixups registered.
 566       MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
 567       insert(CEIF);
 568       CEIF->getContents().append(Code.begin(), Code.end());
 569       CEIF->setHasInstructions(STI);
 570       return;
 571     } else {
 572       DF = new MCDataFragment();
 573       insert(DF);
 574     }
 575     if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
 576       // If this fragment is for a group marked "align_to_end", set a flag
 577       // in the fragment. This can happen after the fragment has already been
 578       // created if there are nested bundle_align groups and an inner one
 579       // is the one marked align_to_end.
 580       DF->setAlignToBundleEnd(true);
 581     }
 582
 583     // We're now emitting an instruction in a bundle group, so this flag has
 584     // to be turned off.
 585     Sec.setBundleGroupBeforeFirstInst(false);
 586   } else {
 587     DF = getOrCreateDataFragment(&STI);
 588   }
 589
 590   // Add the fixups and data.
 591   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
 592     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
 593     DF->getFixups().push_back(Fixups[i]);
 594   }
 595   DF->setHasInstructions(STI);
 596   DF->getContents().append(Code.begin(), Code.end());
 597
 598   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
 599     if (!isBundleLocked()) {
 600       mergeFragment(getOrCreateDataFragment(&STI), DF);
 601       delete DF;
 602     }
 603   }
 604 }
 605
 606 void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
 607   assert(AlignPow2 <= 30 && "Invalid bundle alignment");
 608   MCAssembler &Assembler = getAssembler();
 609   if (AlignPow2 > 0 && (Assembler.getBundleAlignSize() == 0 ||
 610                         Assembler.getBundleAlignSize() == 1U << AlignPow2))
 611     Assembler.setBundleAlignSize(1U << AlignPow2);
 612   else
 613     report_fatal_error(".bundle_align_mode cannot be changed once set");
 614 }
 615
 616 void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
 617   MCSection &Sec = *getCurrentSectionOnly();
 618
 619   // Sanity checks
 620   //
 621   if (!getAssembler().isBundlingEnabled())
 622     report_fatal_error(".bundle_lock forbidden when bundling is disabled");
 623
 624   if (!isBundleLocked())
 625     Sec.setBundleGroupBeforeFirstInst(true);
 626
 627   if (getAssembler().getRelaxAll() && !isBundleLocked()) {
 628     // TODO: drop the lock state and set directly in the fragment
 629     MCDataFragment *DF = new MCDataFragment();
 630     BundleGroups.push_back(DF);
 631   }
 632
 633   Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
 634                                     : MCSection::BundleLocked);
 635 }
 636
 637 void MCELFStreamer::EmitBundleUnlock() {
 638   MCSection &Sec = *getCurrentSectionOnly();
 639
 640   // Sanity checks
 641   if (!getAssembler().isBundlingEnabled())
 642     report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
 643   else if (!isBundleLocked())
 644     report_fatal_error(".bundle_unlock without matching lock");
 645   else if (Sec.isBundleGroupBeforeFirstInst())
 646     report_fatal_error("Empty bundle-locked group is forbidden");
 647
 648   // When the -mc-relax-all flag is used, we emit instructions to fragments
 649   // stored on a stack. When the bundle unlock is emitted, we pop a fragment
 650   // from the stack a merge it to the one below.
 651   if (getAssembler().getRelaxAll()) {
 652     assert(!BundleGroups.empty() && "There are no bundle groups");
 653     MCDataFragment *DF = BundleGroups.back();
 654
 655     // FIXME: Use BundleGroups to track the lock state instead.
 656     Sec.setBundleLockState(MCSection::NotBundleLocked);
 657
 658     // FIXME: Use more separate fragments for nested groups.
 659     if (!isBundleLocked()) {
 660       mergeFragment(getOrCreateDataFragment(DF->getSubtargetInfo()), DF);
 661       BundleGroups.pop_back();
 662       delete DF;
 663     }
 664
 665     if (Sec.getBundleLockState() != MCSection::BundleLockedAlignToEnd)
 666       getOrCreateDataFragment()->setAlignToBundleEnd(false);
 667   } else
 668     Sec.setBundleLockState(MCSection::NotBundleLocked);
 669 }
 670
 671 void MCELFStreamer::FinishImpl() {
 672   // Ensure the last section gets aligned if necessary.
 673   MCSection *CurSection = getCurrentSectionOnly();
 674   setSectionAlignmentForBundling(getAssembler(), CurSection);
 675
 676   finalizeCGProfile();
 677   EmitFrames(nullptr);
 678
 679   this->MCObjectStreamer::FinishImpl();
 680 }
 681
 682 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
 683   llvm_unreachable("Generic ELF doesn't support this directive");
 684 }
 685
 686 void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 687   llvm_unreachable("ELF doesn't support this directive");
 688 }
 689
 690 void MCELFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
 691                                  uint64_t Size, unsigned ByteAlignment,
 692                                  SMLoc Loc) {
 693   llvm_unreachable("ELF doesn't support this directive");
 694 }
 695
 696 void MCELFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
 697                                    uint64_t Size, unsigned ByteAlignment) {
 698   llvm_unreachable("ELF doesn't support this directive");
 699 }
 700
 701 MCStreamer *llvm::createELFStreamer(MCContext &Context,
 702                                     std::unique_ptr<MCAsmBackend> &&MAB,
 703                                     std::unique_ptr<MCObjectWriter> &&OW,
 704                                     std::unique_ptr<MCCodeEmitter> &&CE,
 705                                     bool RelaxAll) {
 706   MCELFStreamer *S =
 707       new MCELFStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
 708   if (RelaxAll)
 709     S->getAssembler().setRelaxAll(true);
 710   return S;
 711 }