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(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
 282   return true;
 283 }
 284
 285 void MCELFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
 286                                      unsigned ByteAlignment) {
 287   auto *Symbol = cast<MCSymbolELF>(S);
 288   getAssembler().registerSymbol(*Symbol);
 289
 290   if (!Symbol->isBindingSet()) {
 291     Symbol->setBinding(ELF::STB_GLOBAL);
 292     Symbol->setExternal(true);
 293   }
 294
 295   Symbol->setType(ELF::STT_OBJECT);
 296
 297   if (Symbol->getBinding() == ELF::STB_LOCAL) {
 298     MCSection &Section = *getAssembler().getContext().getELFSection(
 299         ".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
 300     MCSectionSubPair P = getCurrentSection();
 301     SwitchSection(&Section);
 302
 303     EmitValueToAlignment(ByteAlignment, 0, 1, 0);
 304     EmitLabel(Symbol);
 305     EmitZeros(Size);
 306
 307     // Update the maximum alignment of the section if necessary.
 308     if (ByteAlignment > Section.getAlignment())
 309       Section.setAlignment(ByteAlignment);
 310
 311     SwitchSection(P.first, P.second);
 312   } else {
 313     if(Symbol->declareCommon(Size, ByteAlignment))
 314       report_fatal_error("Symbol: " + Symbol->getName() +
 315                          " redeclared as different type");
 316   }
 317
 318   cast<MCSymbolELF>(Symbol)
 319       ->setSize(MCConstantExpr::create(Size, getContext()));
 320 }
 321
 322 void MCELFStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
 323   cast<MCSymbolELF>(Symbol)->setSize(Value);
 324 }
 325
 326 void MCELFStreamer::emitELFSymverDirective(StringRef AliasName,
 327                                            const MCSymbol *Aliasee) {
 328   getAssembler().Symvers.push_back({AliasName, Aliasee});
 329 }
 330
 331 void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
 332                                           unsigned ByteAlignment) {
 333   auto *Symbol = cast<MCSymbolELF>(S);
 334   // FIXME: Should this be caught and done earlier?
 335   getAssembler().registerSymbol(*Symbol);
 336   Symbol->setBinding(ELF::STB_LOCAL);
 337   Symbol->setExternal(false);
 338   EmitCommonSymbol(Symbol, Size, ByteAlignment);
 339 }
 340
 341 void MCELFStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
 342                                   SMLoc Loc) {
 343   if (isBundleLocked())
 344     report_fatal_error("Emitting values inside a locked bundle is forbidden");
 345   fixSymbolsInTLSFixups(Value);
 346   MCObjectStreamer::EmitValueImpl(Value, Size, Loc);
 347 }
 348
 349 void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
 350                                          int64_t Value,
 351                                          unsigned ValueSize,
 352                                          unsigned MaxBytesToEmit) {
 353   if (isBundleLocked())
 354     report_fatal_error("Emitting values inside a locked bundle is forbidden");
 355   MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value,
 356                                          ValueSize, MaxBytesToEmit);
 357 }
 358
 359 void MCELFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
 360                                        const MCSymbolRefExpr *To,
 361                                        uint64_t Count) {
 362   getAssembler().CGProfile.push_back({From, To, Count});
 363 }
 364
 365 void MCELFStreamer::EmitIdent(StringRef IdentString) {
 366   MCSection *Comment = getAssembler().getContext().getELFSection(
 367       ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
 368   PushSection();
 369   SwitchSection(Comment);
 370   if (!SeenIdent) {
 371     EmitIntValue(0, 1);
 372     SeenIdent = true;
 373   }
 374   EmitBytes(IdentString);
 375   EmitIntValue(0, 1);
 376   PopSection();
 377 }
 378
 379 void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
 380   switch (expr->getKind()) {
 381   case MCExpr::Target:
 382     cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
 383     break;
 384   case MCExpr::Constant:
 385     break;
 386
 387   case MCExpr::Binary: {
 388     const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
 389     fixSymbolsInTLSFixups(be->getLHS());
 390     fixSymbolsInTLSFixups(be->getRHS());
 391     break;
 392   }
 393
 394   case MCExpr::SymbolRef: {
 395     const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
 396     switch (symRef.getKind()) {
 397     default:
 398       return;
 399     case MCSymbolRefExpr::VK_GOTTPOFF:
 400     case MCSymbolRefExpr::VK_INDNTPOFF:
 401     case MCSymbolRefExpr::VK_NTPOFF:
 402     case MCSymbolRefExpr::VK_GOTNTPOFF:
 403     case MCSymbolRefExpr::VK_TLSCALL:
 404     case MCSymbolRefExpr::VK_TLSDESC:
 405     case MCSymbolRefExpr::VK_TLSGD:
 406     case MCSymbolRefExpr::VK_TLSLD:
 407     case MCSymbolRefExpr::VK_TLSLDM:
 408     case MCSymbolRefExpr::VK_TPOFF:
 409     case MCSymbolRefExpr::VK_TPREL:
 410     case MCSymbolRefExpr::VK_DTPOFF:
 411     case MCSymbolRefExpr::VK_DTPREL:
 412     case MCSymbolRefExpr::VK_PPC_DTPMOD:
 413     case MCSymbolRefExpr::VK_PPC_TPREL_LO:
 414     case MCSymbolRefExpr::VK_PPC_TPREL_HI:
 415     case MCSymbolRefExpr::VK_PPC_TPREL_HA:
 416     case MCSymbolRefExpr::VK_PPC_TPREL_HIGH:
 417     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHA:
 418     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
 419     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
 420     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
 421     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
 422     case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
 423     case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
 424     case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
 425     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGH:
 426     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHA:
 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::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
 464   const MCSymbol *S = &SRE->getSymbol();
 465   if (S->isTemporary()) {
 466     if (!S->isInSection()) {
 467       getContext().reportError(
 468           SRE->getLoc(), Twine("Reference to undefined temporary symbol ") +
 469                              "`" + S->getName() + "`");
 470       return;
 471     }
 472     S = S->getSection().getBeginSymbol();
 473     S->setUsedInReloc();
 474     SRE =
 475         MCSymbolRefExpr::create(S, SRE->getKind(), getContext(), SRE->getLoc());
 476     return;
 477   }
 478   // Not a temporary, referece it as a weak undefined.
 479   bool Created;
 480   getAssembler().registerSymbol(*S, &Created);
 481   if (Created) {
 482     cast<MCSymbolELF>(S)->setBinding(ELF::STB_WEAK);
 483     cast<MCSymbolELF>(S)->setExternal(true);
 484   }
 485 }
 486
 487 void MCELFStreamer::finalizeCGProfile() {
 488   for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
 489     finalizeCGProfileEntry(E.From);
 490     finalizeCGProfileEntry(E.To);
 491   }
 492 }
 493
 494 void MCELFStreamer::EmitInstToFragment(const MCInst &Inst,
 495                                        const MCSubtargetInfo &STI) {
 496   this->MCObjectStreamer::EmitInstToFragment(Inst, STI);
 497   MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
 498
 499   for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
 500     fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
 501 }
 502
 503 // A fragment can only have one Subtarget, and when bundling is enabled we
 504 // sometimes need to use the same fragment. We give an error if there
 505 // are conflicting Subtargets.
 506 static void CheckBundleSubtargets(const MCSubtargetInfo *OldSTI,
 507                                   const MCSubtargetInfo *NewSTI) {
 508   if (OldSTI && NewSTI && OldSTI != NewSTI)
 509     report_fatal_error("A Bundle can only have one Subtarget.");
 510 }
 511
 512 void MCELFStreamer::EmitInstToData(const MCInst &Inst,
 513                                    const MCSubtargetInfo &STI) {
 514   MCAssembler &Assembler = getAssembler();
 515   SmallVector<MCFixup, 4> Fixups;
 516   SmallString<256> Code;
 517   raw_svector_ostream VecOS(Code);
 518   Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
 519
 520   for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
 521     fixSymbolsInTLSFixups(Fixups[i].getValue());
 522
 523   // There are several possibilities here:
 524   //
 525   // If bundling is disabled, append the encoded instruction to the current data
 526   // fragment (or create a new such fragment if the current fragment is not a
 527   // data fragment, or the Subtarget has changed).
 528   //
 529   // If bundling is enabled:
 530   // - If we're not in a bundle-locked group, emit the instruction into a
 531   //   fragment of its own. If there are no fixups registered for the
 532   //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
 533   //   MCDataFragment.
 534   // - If we're in a bundle-locked group, append the instruction to the current
 535   //   data fragment because we want all the instructions in a group to get into
 536   //   the same fragment. Be careful not to do that for the first instruction in
 537   //   the group, though.
 538   MCDataFragment *DF;
 539
 540   if (Assembler.isBundlingEnabled()) {
 541     MCSection &Sec = *getCurrentSectionOnly();
 542     if (Assembler.getRelaxAll() && isBundleLocked()) {
 543       // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
 544       // the current bundle group.
 545       DF = BundleGroups.back();
 546       CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
 547     }
 548     else if (Assembler.getRelaxAll() && !isBundleLocked())
 549       // When not in a bundle-locked group and the -mc-relax-all flag is used,
 550       // we create a new temporary fragment which will be later merged into
 551       // the current fragment.
 552       DF = new MCDataFragment();
 553     else if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst()) {
 554       // If we are bundle-locked, we re-use the current fragment.
 555       // The bundle-locking directive ensures this is a new data fragment.
 556       DF = cast<MCDataFragment>(getCurrentFragment());
 557       CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
 558     }
 559     else if (!isBundleLocked() && Fixups.size() == 0) {
 560       // Optimize memory usage by emitting the instruction to a
 561       // MCCompactEncodedInstFragment when not in a bundle-locked group and
 562       // there are no fixups registered.
 563       MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
 564       insert(CEIF);
 565       CEIF->getContents().append(Code.begin(), Code.end());
 566       CEIF->setHasInstructions(STI);
 567       return;
 568     } else {
 569       DF = new MCDataFragment();
 570       insert(DF);
 571     }
 572     if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
 573       // If this fragment is for a group marked "align_to_end", set a flag
 574       // in the fragment. This can happen after the fragment has already been
 575       // created if there are nested bundle_align groups and an inner one
 576       // is the one marked align_to_end.
 577       DF->setAlignToBundleEnd(true);
 578     }
 579
 580     // We're now emitting an instruction in a bundle group, so this flag has
 581     // to be turned off.
 582     Sec.setBundleGroupBeforeFirstInst(false);
 583   } else {
 584     DF = getOrCreateDataFragment(&STI);
 585   }
 586
 587   // Add the fixups and data.
 588   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
 589     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
 590     DF->getFixups().push_back(Fixups[i]);
 591   }
 592   DF->setHasInstructions(STI);
 593   DF->getContents().append(Code.begin(), Code.end());
 594
 595   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
 596     if (!isBundleLocked()) {
 597       mergeFragment(getOrCreateDataFragment(&STI), DF);
 598       delete DF;
 599     }
 600   }
 601 }
 602
 603 void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
 604   assert(AlignPow2 <= 30 && "Invalid bundle alignment");
 605   MCAssembler &Assembler = getAssembler();
 606   if (AlignPow2 > 0 && (Assembler.getBundleAlignSize() == 0 ||
 607                         Assembler.getBundleAlignSize() == 1U << AlignPow2))
 608     Assembler.setBundleAlignSize(1U << AlignPow2);
 609   else
 610     report_fatal_error(".bundle_align_mode cannot be changed once set");
 611 }
 612
 613 void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
 614   MCSection &Sec = *getCurrentSectionOnly();
 615
 616   // Sanity checks
 617   //
 618   if (!getAssembler().isBundlingEnabled())
 619     report_fatal_error(".bundle_lock forbidden when bundling is disabled");
 620
 621   if (!isBundleLocked())
 622     Sec.setBundleGroupBeforeFirstInst(true);
 623
 624   if (getAssembler().getRelaxAll() && !isBundleLocked()) {
 625     // TODO: drop the lock state and set directly in the fragment
 626     MCDataFragment *DF = new MCDataFragment();
 627     BundleGroups.push_back(DF);
 628   }
 629
 630   Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
 631                                     : MCSection::BundleLocked);
 632 }
 633
 634 void MCELFStreamer::EmitBundleUnlock() {
 635   MCSection &Sec = *getCurrentSectionOnly();
 636
 637   // Sanity checks
 638   if (!getAssembler().isBundlingEnabled())
 639     report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
 640   else if (!isBundleLocked())
 641     report_fatal_error(".bundle_unlock without matching lock");
 642   else if (Sec.isBundleGroupBeforeFirstInst())
 643     report_fatal_error("Empty bundle-locked group is forbidden");
 644
 645   // When the -mc-relax-all flag is used, we emit instructions to fragments
 646   // stored on a stack. When the bundle unlock is emitted, we pop a fragment
 647   // from the stack a merge it to the one below.
 648   if (getAssembler().getRelaxAll()) {
 649     assert(!BundleGroups.empty() && "There are no bundle groups");
 650     MCDataFragment *DF = BundleGroups.back();
 651
 652     // FIXME: Use BundleGroups to track the lock state instead.
 653     Sec.setBundleLockState(MCSection::NotBundleLocked);
 654
 655     // FIXME: Use more separate fragments for nested groups.
 656     if (!isBundleLocked()) {
 657       mergeFragment(getOrCreateDataFragment(DF->getSubtargetInfo()), DF);
 658       BundleGroups.pop_back();
 659       delete DF;
 660     }
 661
 662     if (Sec.getBundleLockState() != MCSection::BundleLockedAlignToEnd)
 663       getOrCreateDataFragment()->setAlignToBundleEnd(false);
 664   } else
 665     Sec.setBundleLockState(MCSection::NotBundleLocked);
 666 }
 667
 668 void MCELFStreamer::FinishImpl() {
 669   // Ensure the last section gets aligned if necessary.
 670   MCSection *CurSection = getCurrentSectionOnly();
 671   setSectionAlignmentForBundling(getAssembler(), CurSection);
 672
 673   finalizeCGProfile();
 674   EmitFrames(nullptr);
 675
 676   this->MCObjectStreamer::FinishImpl();
 677 }
 678
 679 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
 680   llvm_unreachable("Generic ELF doesn't support this directive");
 681 }
 682
 683 void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 684   llvm_unreachable("ELF doesn't support this directive");
 685 }
 686
 687 void MCELFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
 688                                  uint64_t Size, unsigned ByteAlignment,
 689                                  SMLoc Loc) {
 690   llvm_unreachable("ELF doesn't support this directive");
 691 }
 692
 693 void MCELFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
 694                                    uint64_t Size, unsigned ByteAlignment) {
 695   llvm_unreachable("ELF doesn't support this directive");
 696 }
 697
 698 MCStreamer *llvm::createELFStreamer(MCContext &Context,
 699                                     std::unique_ptr<MCAsmBackend> &&MAB,
 700                                     std::unique_ptr<MCObjectWriter> &&OW,
 701                                     std::unique_ptr<MCCodeEmitter> &&CE,
 702                                     bool RelaxAll) {
 703   MCELFStreamer *S =
 704       new MCELFStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
 705   if (RelaxAll)
 706     S->getAssembler().setRelaxAll(true);
 707   return S;
 708 }