lib/CodeGen/TargetLoweringObjectFileImpl.cpp

   1 //===- llvm/CodeGen/TargetLoweringObjectFileImpl.cpp - Object File Info ---===//
   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 implements classes used to handle lowerings specific to common
  11 // object file formats.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
  16 #include "llvm/ADT/SmallString.h"
  17 #include "llvm/ADT/SmallVector.h"
  18 #include "llvm/ADT/StringExtras.h"
  19 #include "llvm/ADT/StringRef.h"
  20 #include "llvm/ADT/Triple.h"
  21 #include "llvm/BinaryFormat/COFF.h"
  22 #include "llvm/BinaryFormat/Dwarf.h"
  23 #include "llvm/BinaryFormat/ELF.h"
  24 #include "llvm/BinaryFormat/MachO.h"
  25 #include "llvm/CodeGen/MachineModuleInfo.h"
  26 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
  27 #include "llvm/IR/Comdat.h"
  28 #include "llvm/IR/Constants.h"
  29 #include "llvm/IR/DataLayout.h"
  30 #include "llvm/IR/DerivedTypes.h"
  31 #include "llvm/IR/Function.h"
  32 #include "llvm/IR/GlobalAlias.h"
  33 #include "llvm/IR/GlobalObject.h"
  34 #include "llvm/IR/GlobalValue.h"
  35 #include "llvm/IR/GlobalVariable.h"
  36 #include "llvm/IR/Mangler.h"
  37 #include "llvm/IR/Metadata.h"
  38 #include "llvm/IR/Module.h"
  39 #include "llvm/IR/Type.h"
  40 #include "llvm/MC/MCAsmInfo.h"
  41 #include "llvm/MC/MCContext.h"
  42 #include "llvm/MC/MCExpr.h"
  43 #include "llvm/MC/MCSectionCOFF.h"
  44 #include "llvm/MC/MCSectionELF.h"
  45 #include "llvm/MC/MCSectionMachO.h"
  46 #include "llvm/MC/MCSectionWasm.h"
  47 #include "llvm/MC/MCStreamer.h"
  48 #include "llvm/MC/MCSymbol.h"
  49 #include "llvm/MC/MCSymbolELF.h"
  50 #include "llvm/MC/MCValue.h"
  51 #include "llvm/MC/SectionKind.h"
  52 #include "llvm/ProfileData/InstrProf.h"
  53 #include "llvm/Support/Casting.h"
  54 #include "llvm/Support/CodeGen.h"
  55 #include "llvm/Support/Format.h"
  56 #include "llvm/Support/ErrorHandling.h"
  57 #include "llvm/Support/raw_ostream.h"
  58 #include "llvm/Target/TargetMachine.h"
  59 #include <cassert>
  60 #include <string>
  61
  62 using namespace llvm;
  63 using namespace dwarf;
  64
  65 static void GetObjCImageInfo(Module &M, unsigned &Version, unsigned &Flags,
  66                              StringRef &Section) {
  67   SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
  68   M.getModuleFlagsMetadata(ModuleFlags);
  69
  70   for (const auto &MFE: ModuleFlags) {
  71     // Ignore flags with 'Require' behaviour.
  72     if (MFE.Behavior == Module::Require)
  73       continue;
  74
  75     StringRef Key = MFE.Key->getString();
  76     if (Key == "Objective-C Image Info Version") {
  77       Version = mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
  78     } else if (Key == "Objective-C Garbage Collection" ||
  79                Key == "Objective-C GC Only" ||
  80                Key == "Objective-C Is Simulated" ||
  81                Key == "Objective-C Class Properties" ||
  82                Key == "Objective-C Image Swift Version") {
  83       Flags |= mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
  84     } else if (Key == "Objective-C Image Info Section") {
  85       Section = cast<MDString>(MFE.Val)->getString();
  86     }
  87   }
  88 }
  89
  90 //===----------------------------------------------------------------------===//
  91 //                                  ELF
  92 //===----------------------------------------------------------------------===//
  93
  94 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
  95                                              const TargetMachine &TgtM) {
  96   TargetLoweringObjectFile::Initialize(Ctx, TgtM);
  97   TM = &TgtM;
  98
  99   CodeModel::Model CM = TgtM.getCodeModel();
 100
 101   switch (TgtM.getTargetTriple().getArch()) {
 102   case Triple::arm:
 103   case Triple::armeb:
 104   case Triple::thumb:
 105   case Triple::thumbeb:
 106     if (Ctx.getAsmInfo()->getExceptionHandlingType() == ExceptionHandling::ARM)
 107       break;
 108     // Fallthrough if not using EHABI
 109     LLVM_FALLTHROUGH;
 110   case Triple::ppc:
 111   case Triple::x86:
 112     PersonalityEncoding = isPositionIndependent()
 113                               ? dwarf::DW_EH_PE_indirect |
 114                                     dwarf::DW_EH_PE_pcrel |
 115                                     dwarf::DW_EH_PE_sdata4
 116                               : dwarf::DW_EH_PE_absptr;
 117     LSDAEncoding = isPositionIndependent()
 118                        ? dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
 119                        : dwarf::DW_EH_PE_absptr;
 120     TTypeEncoding = isPositionIndependent()
 121                         ? dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 122                               dwarf::DW_EH_PE_sdata4
 123                         : dwarf::DW_EH_PE_absptr;
 124     break;
 125   case Triple::x86_64:
 126     if (isPositionIndependent()) {
 127       PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 128         ((CM == CodeModel::Small || CM == CodeModel::Medium)
 129          ? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
 130       LSDAEncoding = dwarf::DW_EH_PE_pcrel |
 131         (CM == CodeModel::Small
 132          ? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
 133       TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 134         ((CM == CodeModel::Small || CM == CodeModel::Medium)
 135          ? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
 136     } else {
 137       PersonalityEncoding =
 138         (CM == CodeModel::Small || CM == CodeModel::Medium)
 139         ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
 140       LSDAEncoding = (CM == CodeModel::Small)
 141         ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
 142       TTypeEncoding = (CM == CodeModel::Small)
 143         ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
 144     }
 145     break;
 146   case Triple::hexagon:
 147     PersonalityEncoding = dwarf::DW_EH_PE_absptr;
 148     LSDAEncoding = dwarf::DW_EH_PE_absptr;
 149     TTypeEncoding = dwarf::DW_EH_PE_absptr;
 150     if (isPositionIndependent()) {
 151       PersonalityEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
 152       LSDAEncoding |= dwarf::DW_EH_PE_pcrel;
 153       TTypeEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
 154     }
 155     break;
 156   case Triple::aarch64:
 157   case Triple::aarch64_be:
 158     // The small model guarantees static code/data size < 4GB, but not where it
 159     // will be in memory. Most of these could end up >2GB away so even a signed
 160     // pc-relative 32-bit address is insufficient, theoretically.
 161     if (isPositionIndependent()) {
 162       PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 163         dwarf::DW_EH_PE_sdata8;
 164       LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8;
 165       TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 166         dwarf::DW_EH_PE_sdata8;
 167     } else {
 168       PersonalityEncoding = dwarf::DW_EH_PE_absptr;
 169       LSDAEncoding = dwarf::DW_EH_PE_absptr;
 170       TTypeEncoding = dwarf::DW_EH_PE_absptr;
 171     }
 172     break;
 173   case Triple::lanai:
 174     LSDAEncoding = dwarf::DW_EH_PE_absptr;
 175     PersonalityEncoding = dwarf::DW_EH_PE_absptr;
 176     TTypeEncoding = dwarf::DW_EH_PE_absptr;
 177     break;
 178   case Triple::mips:
 179   case Triple::mipsel:
 180   case Triple::mips64:
 181   case Triple::mips64el:
 182     // MIPS uses indirect pointer to refer personality functions and types, so
 183     // that the eh_frame section can be read-only. DW.ref.personality will be
 184     // generated for relocation.
 185     PersonalityEncoding = dwarf::DW_EH_PE_indirect;
 186     // FIXME: The N64 ABI probably ought to use DW_EH_PE_sdata8 but we can't
 187     //        identify N64 from just a triple.
 188     TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 189                     dwarf::DW_EH_PE_sdata4;
 190     // We don't support PC-relative LSDA references in GAS so we use the default
 191     // DW_EH_PE_absptr for those.
 192
 193     // FreeBSD must be explicit about the data size and using pcrel since it's
 194     // assembler/linker won't do the automatic conversion that the Linux tools
 195     // do.
 196     if (TgtM.getTargetTriple().isOSFreeBSD()) {
 197       PersonalityEncoding |= dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
 198       LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
 199     }
 200     break;
 201   case Triple::ppc64:
 202   case Triple::ppc64le:
 203     PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 204       dwarf::DW_EH_PE_udata8;
 205     LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8;
 206     TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 207       dwarf::DW_EH_PE_udata8;
 208     break;
 209   case Triple::sparcel:
 210   case Triple::sparc:
 211     if (isPositionIndependent()) {
 212       LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
 213       PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 214         dwarf::DW_EH_PE_sdata4;
 215       TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 216         dwarf::DW_EH_PE_sdata4;
 217     } else {
 218       LSDAEncoding = dwarf::DW_EH_PE_absptr;
 219       PersonalityEncoding = dwarf::DW_EH_PE_absptr;
 220       TTypeEncoding = dwarf::DW_EH_PE_absptr;
 221     }
 222     break;
 223   case Triple::sparcv9:
 224     LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
 225     if (isPositionIndependent()) {
 226       PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 227         dwarf::DW_EH_PE_sdata4;
 228       TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 229         dwarf::DW_EH_PE_sdata4;
 230     } else {
 231       PersonalityEncoding = dwarf::DW_EH_PE_absptr;
 232       TTypeEncoding = dwarf::DW_EH_PE_absptr;
 233     }
 234     break;
 235   case Triple::systemz:
 236     // All currently-defined code models guarantee that 4-byte PC-relative
 237     // values will be in range.
 238     if (isPositionIndependent()) {
 239       PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 240         dwarf::DW_EH_PE_sdata4;
 241       LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
 242       TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
 243         dwarf::DW_EH_PE_sdata4;
 244     } else {
 245       PersonalityEncoding = dwarf::DW_EH_PE_absptr;
 246       LSDAEncoding = dwarf::DW_EH_PE_absptr;
 247       TTypeEncoding = dwarf::DW_EH_PE_absptr;
 248     }
 249     break;
 250   default:
 251     break;
 252   }
 253 }
 254
 255 void TargetLoweringObjectFileELF::emitModuleMetadata(MCStreamer &Streamer,
 256                                                      Module &M) const {
 257   auto &C = getContext();
 258
 259   if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
 260     auto *S = C.getELFSection(".linker-options", ELF::SHT_LLVM_LINKER_OPTIONS,
 261                               ELF::SHF_EXCLUDE);
 262
 263     Streamer.SwitchSection(S);
 264
 265     for (const auto &Operand : LinkerOptions->operands()) {
 266       if (cast<MDNode>(Operand)->getNumOperands() != 2)
 267         report_fatal_error("invalid llvm.linker.options");
 268       for (const auto &Option : cast<MDNode>(Operand)->operands()) {
 269         Streamer.EmitBytes(cast<MDString>(Option)->getString());
 270         Streamer.EmitIntValue(0, 1);
 271       }
 272     }
 273   }
 274
 275   unsigned Version = 0;
 276   unsigned Flags = 0;
 277   StringRef Section;
 278
 279   GetObjCImageInfo(M, Version, Flags, Section);
 280   if (!Section.empty()) {
 281     auto *S = C.getELFSection(Section, ELF::SHT_PROGBITS, ELF::SHF_ALLOC);
 282     Streamer.SwitchSection(S);
 283     Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
 284     Streamer.EmitIntValue(Version, 4);
 285     Streamer.EmitIntValue(Flags, 4);
 286     Streamer.AddBlankLine();
 287   }
 288
 289   SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
 290   M.getModuleFlagsMetadata(ModuleFlags);
 291
 292   MDNode *CFGProfile = nullptr;
 293
 294   for (const auto &MFE : ModuleFlags) {
 295     StringRef Key = MFE.Key->getString();
 296     if (Key == "CG Profile") {
 297       CFGProfile = cast<MDNode>(MFE.Val);
 298       break;
 299     }
 300   }
 301
 302   if (!CFGProfile)
 303     return;
 304
 305   auto GetSym = [this](const MDOperand &MDO) -> MCSymbol * {
 306     if (!MDO)
 307       return nullptr;
 308     auto V = cast<ValueAsMetadata>(MDO);
 309     const Function *F = cast<Function>(V->getValue());
 310     return TM->getSymbol(F);
 311   };
 312
 313   for (const auto &Edge : CFGProfile->operands()) {
 314     MDNode *E = cast<MDNode>(Edge);
 315     const MCSymbol *From = GetSym(E->getOperand(0));
 316     const MCSymbol *To = GetSym(E->getOperand(1));
 317     // Skip null functions. This can happen if functions are dead stripped after
 318     // the CGProfile pass has been run.
 319     if (!From || !To)
 320       continue;
 321     uint64_t Count = cast<ConstantAsMetadata>(E->getOperand(2))
 322                          ->getValue()
 323                          ->getUniqueInteger()
 324                          .getZExtValue();
 325     Streamer.emitCGProfileEntry(
 326         MCSymbolRefExpr::create(From, MCSymbolRefExpr::VK_None, C),
 327         MCSymbolRefExpr::create(To, MCSymbolRefExpr::VK_None, C), Count);
 328   }
 329 }
 330
 331 MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
 332     const GlobalValue *GV, const TargetMachine &TM,
 333     MachineModuleInfo *MMI) const {
 334   unsigned Encoding = getPersonalityEncoding();
 335   if ((Encoding & 0x80) == DW_EH_PE_indirect)
 336     return getContext().getOrCreateSymbol(StringRef("DW.ref.") +
 337                                           TM.getSymbol(GV)->getName());
 338   if ((Encoding & 0x70) == DW_EH_PE_absptr)
 339     return TM.getSymbol(GV);
 340   report_fatal_error("We do not support this DWARF encoding yet!");
 341 }
 342
 343 void TargetLoweringObjectFileELF::emitPersonalityValue(
 344     MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
 345   SmallString<64> NameData("DW.ref.");
 346   NameData += Sym->getName();
 347   MCSymbolELF *Label =
 348       cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
 349   Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
 350   Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
 351   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
 352   MCSection *Sec = getContext().getELFNamedSection(".data", Label->getName(),
 353                                                    ELF::SHT_PROGBITS, Flags, 0);
 354   unsigned Size = DL.getPointerSize();
 355   Streamer.SwitchSection(Sec);
 356   Streamer.EmitValueToAlignment(DL.getPointerABIAlignment(0));
 357   Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
 358   const MCExpr *E = MCConstantExpr::create(Size, getContext());
 359   Streamer.emitELFSize(Label, E);
 360   Streamer.EmitLabel(Label);
 361
 362   Streamer.EmitSymbolValue(Sym, Size);
 363 }
 364
 365 const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
 366     const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
 367     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
 368   if (Encoding & DW_EH_PE_indirect) {
 369     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
 370
 371     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", TM);
 372
 373     // Add information about the stub reference to ELFMMI so that the stub
 374     // gets emitted by the asmprinter.
 375     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
 376     if (!StubSym.getPointer()) {
 377       MCSymbol *Sym = TM.getSymbol(GV);
 378       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
 379     }
 380
 381     return TargetLoweringObjectFile::
 382       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
 383                         Encoding & ~DW_EH_PE_indirect, Streamer);
 384   }
 385
 386   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
 387                                                            MMI, Streamer);
 388 }
 389
 390 static SectionKind getELFKindForNamedSection(StringRef Name, SectionKind K) {
 391   // N.B.: The defaults used in here are not the same ones used in MC.
 392   // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
 393   // both gas and MC will produce a section with no flags. Given
 394   // section(".eh_frame") gcc will produce:
 395   //
 396   //   .section   .eh_frame,"a",@progbits
 397
 398   if (Name == getInstrProfSectionName(IPSK_covmap, Triple::ELF,
 399                                       /*AddSegmentInfo=*/false))
 400     return SectionKind::getMetadata();
 401
 402   if (Name.empty() || Name[0] != '.') return K;
 403
 404   // Default implementation based on some magic section names.
 405   if (Name == ".bss" ||
 406       Name.startswith(".bss.") ||
 407       Name.startswith(".gnu.linkonce.b.") ||
 408       Name.startswith(".llvm.linkonce.b.") ||
 409       Name == ".sbss" ||
 410       Name.startswith(".sbss.") ||
 411       Name.startswith(".gnu.linkonce.sb.") ||
 412       Name.startswith(".llvm.linkonce.sb."))
 413     return SectionKind::getBSS();
 414
 415   if (Name == ".tdata" ||
 416       Name.startswith(".tdata.") ||
 417       Name.startswith(".gnu.linkonce.td.") ||
 418       Name.startswith(".llvm.linkonce.td."))
 419     return SectionKind::getThreadData();
 420
 421   if (Name == ".tbss" ||
 422       Name.startswith(".tbss.") ||
 423       Name.startswith(".gnu.linkonce.tb.") ||
 424       Name.startswith(".llvm.linkonce.tb."))
 425     return SectionKind::getThreadBSS();
 426
 427   return K;
 428 }
 429
 430 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
 431   // Use SHT_NOTE for section whose name starts with ".note" to allow
 432   // emitting ELF notes from C variable declaration.
 433   // See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77609
 434   if (Name.startswith(".note"))
 435     return ELF::SHT_NOTE;
 436
 437   if (Name == ".init_array")
 438     return ELF::SHT_INIT_ARRAY;
 439
 440   if (Name == ".fini_array")
 441     return ELF::SHT_FINI_ARRAY;
 442
 443   if (Name == ".preinit_array")
 444     return ELF::SHT_PREINIT_ARRAY;
 445
 446   if (K.isBSS() || K.isThreadBSS())
 447     return ELF::SHT_NOBITS;
 448
 449   return ELF::SHT_PROGBITS;
 450 }
 451
 452 static unsigned getELFSectionFlags(SectionKind K) {
 453   unsigned Flags = 0;
 454
 455   if (!K.isMetadata())
 456     Flags |= ELF::SHF_ALLOC;
 457
 458   if (K.isText())
 459     Flags |= ELF::SHF_EXECINSTR;
 460
 461   if (K.isExecuteOnly())
 462     Flags |= ELF::SHF_ARM_PURECODE;
 463
 464   if (K.isWriteable())
 465     Flags |= ELF::SHF_WRITE;
 466
 467   if (K.isThreadLocal())
 468     Flags |= ELF::SHF_TLS;
 469
 470   if (K.isMergeableCString() || K.isMergeableConst())
 471     Flags |= ELF::SHF_MERGE;
 472
 473   if (K.isMergeableCString())
 474     Flags |= ELF::SHF_STRINGS;
 475
 476   return Flags;
 477 }
 478
 479 static const Comdat *getELFComdat(const GlobalValue *GV) {
 480   const Comdat *C = GV->getComdat();
 481   if (!C)
 482     return nullptr;
 483
 484   if (C->getSelectionKind() != Comdat::Any)
 485     report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
 486                        C->getName() + "' cannot be lowered.");
 487
 488   return C;
 489 }
 490
 491 static const MCSymbolELF *getAssociatedSymbol(const GlobalObject *GO,
 492                                               const TargetMachine &TM) {
 493   MDNode *MD = GO->getMetadata(LLVMContext::MD_associated);
 494   if (!MD)
 495     return nullptr;
 496
 497   const MDOperand &Op = MD->getOperand(0);
 498   if (!Op.get())
 499     return nullptr;
 500
 501   auto *VM = dyn_cast<ValueAsMetadata>(Op);
 502   if (!VM)
 503     report_fatal_error("MD_associated operand is not ValueAsMetadata");
 504
 505   GlobalObject *OtherGO = dyn_cast<GlobalObject>(VM->getValue());
 506   return OtherGO ? dyn_cast<MCSymbolELF>(TM.getSymbol(OtherGO)) : nullptr;
 507 }
 508
 509 MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
 510     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
 511   StringRef SectionName = GO->getSection();
 512
 513   // Check if '#pragma clang section' name is applicable.
 514   // Note that pragma directive overrides -ffunction-section, -fdata-section
 515   // and so section name is exactly as user specified and not uniqued.
 516   const GlobalVariable *GV = dyn_cast<GlobalVariable>(GO);
 517   if (GV && GV->hasImplicitSection()) {
 518     auto Attrs = GV->getAttributes();
 519     if (Attrs.hasAttribute("bss-section") && Kind.isBSS()) {
 520       SectionName = Attrs.getAttribute("bss-section").getValueAsString();
 521     } else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()) {
 522       SectionName = Attrs.getAttribute("rodata-section").getValueAsString();
 523     } else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
 524       SectionName = Attrs.getAttribute("data-section").getValueAsString();
 525     }
 526   }
 527   const Function *F = dyn_cast<Function>(GO);
 528   if (F && F->hasFnAttribute("implicit-section-name")) {
 529     SectionName = F->getFnAttribute("implicit-section-name").getValueAsString();
 530   }
 531
 532   // Infer section flags from the section name if we can.
 533   Kind = getELFKindForNamedSection(SectionName, Kind);
 534
 535   StringRef Group = "";
 536   unsigned Flags = getELFSectionFlags(Kind);
 537   if (const Comdat *C = getELFComdat(GO)) {
 538     Group = C->getName();
 539     Flags |= ELF::SHF_GROUP;
 540   }
 541
 542   // A section can have at most one associated section. Put each global with
 543   // MD_associated in a unique section.
 544   unsigned UniqueID = MCContext::GenericSectionID;
 545   const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
 546   if (AssociatedSymbol) {
 547     UniqueID = NextUniqueID++;
 548     Flags |= ELF::SHF_LINK_ORDER;
 549   }
 550
 551   MCSectionELF *Section = getContext().getELFSection(
 552       SectionName, getELFSectionType(SectionName, Kind), Flags,
 553       /*EntrySize=*/0, Group, UniqueID, AssociatedSymbol);
 554   // Make sure that we did not get some other section with incompatible sh_link.
 555   // This should not be possible due to UniqueID code above.
 556   assert(Section->getAssociatedSymbol() == AssociatedSymbol &&
 557          "Associated symbol mismatch between sections");
 558   return Section;
 559 }
 560
 561 /// Return the section prefix name used by options FunctionsSections and
 562 /// DataSections.
 563 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
 564   if (Kind.isText())
 565     return ".text";
 566   if (Kind.isReadOnly())
 567     return ".rodata";
 568   if (Kind.isBSS())
 569     return ".bss";
 570   if (Kind.isThreadData())
 571     return ".tdata";
 572   if (Kind.isThreadBSS())
 573     return ".tbss";
 574   if (Kind.isData())
 575     return ".data";
 576   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
 577   return ".data.rel.ro";
 578 }
 579
 580 static unsigned getEntrySizeForKind(SectionKind Kind) {
 581   if (Kind.isMergeable1ByteCString())
 582     return 1;
 583   else if (Kind.isMergeable2ByteCString())
 584     return 2;
 585   else if (Kind.isMergeable4ByteCString())
 586     return 4;
 587   else if (Kind.isMergeableConst4())
 588     return 4;
 589   else if (Kind.isMergeableConst8())
 590     return 8;
 591   else if (Kind.isMergeableConst16())
 592     return 16;
 593   else if (Kind.isMergeableConst32())
 594     return 32;
 595   else {
 596     // We shouldn't have mergeable C strings or mergeable constants that we
 597     // didn't handle above.
 598     assert(!Kind.isMergeableCString() && "unknown string width");
 599     assert(!Kind.isMergeableConst() && "unknown data width");
 600     return 0;
 601   }
 602 }
 603
 604 static MCSectionELF *selectELFSectionForGlobal(
 605     MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
 606     const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
 607     unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol) {
 608
 609   StringRef Group = "";
 610   if (const Comdat *C = getELFComdat(GO)) {
 611     Flags |= ELF::SHF_GROUP;
 612     Group = C->getName();
 613   }
 614
 615   // Get the section entry size based on the kind.
 616   unsigned EntrySize = getEntrySizeForKind(Kind);
 617
 618   SmallString<128> Name;
 619   if (Kind.isMergeableCString()) {
 620     // We also need alignment here.
 621     // FIXME: this is getting the alignment of the character, not the
 622     // alignment of the global!
 623     unsigned Align = GO->getParent()->getDataLayout().getPreferredAlignment(
 624         cast<GlobalVariable>(GO));
 625
 626     std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
 627     Name = SizeSpec + utostr(Align);
 628   } else if (Kind.isMergeableConst()) {
 629     Name = ".rodata.cst";
 630     Name += utostr(EntrySize);
 631   } else {
 632     Name = getSectionPrefixForGlobal(Kind);
 633   }
 634
 635   if (const auto *F = dyn_cast<Function>(GO)) {
 636     const auto &OptionalPrefix = F->getSectionPrefix();
 637     if (OptionalPrefix)
 638       Name += *OptionalPrefix;
 639   }
 640
 641   unsigned UniqueID = MCContext::GenericSectionID;
 642   if (EmitUniqueSection) {
 643     if (TM.getUniqueSectionNames()) {
 644       Name.push_back('.');
 645       TM.getNameWithPrefix(Name, GO, Mang, true /*MayAlwaysUsePrivate*/);
 646     } else {
 647       UniqueID = *NextUniqueID;
 648       (*NextUniqueID)++;
 649     }
 650   }
 651   // Use 0 as the unique ID for execute-only text.
 652   if (Kind.isExecuteOnly())
 653     UniqueID = 0;
 654   return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags,
 655                            EntrySize, Group, UniqueID, AssociatedSymbol);
 656 }
 657
 658 MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
 659     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
 660   unsigned Flags = getELFSectionFlags(Kind);
 661
 662   // If we have -ffunction-section or -fdata-section then we should emit the
 663   // global value to a uniqued section specifically for it.
 664   bool EmitUniqueSection = false;
 665   if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
 666     if (Kind.isText())
 667       EmitUniqueSection = TM.getFunctionSections();
 668     else
 669       EmitUniqueSection = TM.getDataSections();
 670   }
 671   EmitUniqueSection |= GO->hasComdat();
 672
 673   const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
 674   if (AssociatedSymbol) {
 675     EmitUniqueSection = true;
 676     Flags |= ELF::SHF_LINK_ORDER;
 677   }
 678
 679   MCSectionELF *Section = selectELFSectionForGlobal(
 680       getContext(), GO, Kind, getMangler(), TM, EmitUniqueSection, Flags,
 681       &NextUniqueID, AssociatedSymbol);
 682   assert(Section->getAssociatedSymbol() == AssociatedSymbol);
 683   return Section;
 684 }
 685
 686 MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
 687     const Function &F, const TargetMachine &TM) const {
 688   // If the function can be removed, produce a unique section so that
 689   // the table doesn't prevent the removal.
 690   const Comdat *C = F.getComdat();
 691   bool EmitUniqueSection = TM.getFunctionSections() || C;
 692   if (!EmitUniqueSection)
 693     return ReadOnlySection;
 694
 695   return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
 696                                    getMangler(), TM, EmitUniqueSection,
 697                                    ELF::SHF_ALLOC, &NextUniqueID,
 698                                    /* AssociatedSymbol */ nullptr);
 699 }
 700
 701 bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
 702     bool UsesLabelDifference, const Function &F) const {
 703   // We can always create relative relocations, so use another section
 704   // that can be marked non-executable.
 705   return false;
 706 }
 707
 708 /// Given a mergeable constant with the specified size and relocation
 709 /// information, return a section that it should be placed in.
 710 MCSection *TargetLoweringObjectFileELF::getSectionForConstant(
 711     const DataLayout &DL, SectionKind Kind, const Constant *C,
 712     unsigned &Align) const {
 713   if (Kind.isMergeableConst4() && MergeableConst4Section)
 714     return MergeableConst4Section;
 715   if (Kind.isMergeableConst8() && MergeableConst8Section)
 716     return MergeableConst8Section;
 717   if (Kind.isMergeableConst16() && MergeableConst16Section)
 718     return MergeableConst16Section;
 719   if (Kind.isMergeableConst32() && MergeableConst32Section)
 720     return MergeableConst32Section;
 721   if (Kind.isReadOnly())
 722     return ReadOnlySection;
 723
 724   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
 725   return DataRelROSection;
 726 }
 727
 728 static MCSectionELF *getStaticStructorSection(MCContext &Ctx, bool UseInitArray,
 729                                               bool IsCtor, unsigned Priority,
 730                                               const MCSymbol *KeySym) {
 731   std::string Name;
 732   unsigned Type;
 733   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
 734   StringRef COMDAT = KeySym ? KeySym->getName() : "";
 735
 736   if (KeySym)
 737     Flags |= ELF::SHF_GROUP;
 738
 739   if (UseInitArray) {
 740     if (IsCtor) {
 741       Type = ELF::SHT_INIT_ARRAY;
 742       Name = ".init_array";
 743     } else {
 744       Type = ELF::SHT_FINI_ARRAY;
 745       Name = ".fini_array";
 746     }
 747     if (Priority != 65535) {
 748       Name += '.';
 749       Name += utostr(Priority);
 750     }
 751   } else {
 752     // The default scheme is .ctor / .dtor, so we have to invert the priority
 753     // numbering.
 754     if (IsCtor)
 755       Name = ".ctors";
 756     else
 757       Name = ".dtors";
 758     if (Priority != 65535)
 759       raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
 760     Type = ELF::SHT_PROGBITS;
 761   }
 762
 763   return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
 764 }
 765
 766 MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
 767     unsigned Priority, const MCSymbol *KeySym) const {
 768   return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
 769                                   KeySym);
 770 }
 771
 772 MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
 773     unsigned Priority, const MCSymbol *KeySym) const {
 774   return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
 775                                   KeySym);
 776 }
 777
 778 const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
 779     const GlobalValue *LHS, const GlobalValue *RHS,
 780     const TargetMachine &TM) const {
 781   // We may only use a PLT-relative relocation to refer to unnamed_addr
 782   // functions.
 783   if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
 784     return nullptr;
 785
 786   // Basic sanity checks.
 787   if (LHS->getType()->getPointerAddressSpace() != 0 ||
 788       RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
 789       RHS->isThreadLocal())
 790     return nullptr;
 791
 792   return MCBinaryExpr::createSub(
 793       MCSymbolRefExpr::create(TM.getSymbol(LHS), PLTRelativeVariantKind,
 794                               getContext()),
 795       MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
 796 }
 797
 798 void
 799 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
 800   UseInitArray = UseInitArray_;
 801   MCContext &Ctx = getContext();
 802   if (!UseInitArray) {
 803     StaticCtorSection = Ctx.getELFSection(".ctors", ELF::SHT_PROGBITS,
 804                                           ELF::SHF_ALLOC | ELF::SHF_WRITE);
 805
 806     StaticDtorSection = Ctx.getELFSection(".dtors", ELF::SHT_PROGBITS,
 807                                           ELF::SHF_ALLOC | ELF::SHF_WRITE);
 808     return;
 809   }
 810
 811   StaticCtorSection = Ctx.getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
 812                                         ELF::SHF_WRITE | ELF::SHF_ALLOC);
 813   StaticDtorSection = Ctx.getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
 814                                         ELF::SHF_WRITE | ELF::SHF_ALLOC);
 815 }
 816
 817 //===----------------------------------------------------------------------===//
 818 //                                 MachO
 819 //===----------------------------------------------------------------------===//
 820
 821 TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
 822   : TargetLoweringObjectFile() {
 823   SupportIndirectSymViaGOTPCRel = true;
 824 }
 825
 826 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
 827                                                const TargetMachine &TM) {
 828   TargetLoweringObjectFile::Initialize(Ctx, TM);
 829   if (TM.getRelocationModel() == Reloc::Static) {
 830     StaticCtorSection = Ctx.getMachOSection("__TEXT", "__constructor", 0,
 831                                             SectionKind::getData());
 832     StaticDtorSection = Ctx.getMachOSection("__TEXT", "__destructor", 0,
 833                                             SectionKind::getData());
 834   } else {
 835     StaticCtorSection = Ctx.getMachOSection("__DATA", "__mod_init_func",
 836                                             MachO::S_MOD_INIT_FUNC_POINTERS,
 837                                             SectionKind::getData());
 838     StaticDtorSection = Ctx.getMachOSection("__DATA", "__mod_term_func",
 839                                             MachO::S_MOD_TERM_FUNC_POINTERS,
 840                                             SectionKind::getData());
 841   }
 842
 843   PersonalityEncoding =
 844       dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
 845   LSDAEncoding = dwarf::DW_EH_PE_pcrel;
 846   TTypeEncoding =
 847       dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
 848 }
 849
 850 void TargetLoweringObjectFileMachO::emitModuleMetadata(MCStreamer &Streamer,
 851                                                        Module &M) const {
 852   // Emit the linker options if present.
 853   if (auto *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
 854     for (const auto &Option : LinkerOptions->operands()) {
 855       SmallVector<std::string, 4> StrOptions;
 856       for (const auto &Piece : cast<MDNode>(Option)->operands())
 857         StrOptions.push_back(cast<MDString>(Piece)->getString());
 858       Streamer.EmitLinkerOptions(StrOptions);
 859     }
 860   }
 861
 862   unsigned VersionVal = 0;
 863   unsigned ImageInfoFlags = 0;
 864   StringRef SectionVal;
 865
 866   GetObjCImageInfo(M, VersionVal, ImageInfoFlags, SectionVal);
 867
 868   // The section is mandatory. If we don't have it, then we don't have GC info.
 869   if (SectionVal.empty())
 870     return;
 871
 872   StringRef Segment, Section;
 873   unsigned TAA = 0, StubSize = 0;
 874   bool TAAParsed;
 875   std::string ErrorCode =
 876     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
 877                                           TAA, TAAParsed, StubSize);
 878   if (!ErrorCode.empty())
 879     // If invalid, report the error with report_fatal_error.
 880     report_fatal_error("Invalid section specifier '" + Section + "': " +
 881                        ErrorCode + ".");
 882
 883   // Get the section.
 884   MCSectionMachO *S = getContext().getMachOSection(
 885       Segment, Section, TAA, StubSize, SectionKind::getData());
 886   Streamer.SwitchSection(S);
 887   Streamer.EmitLabel(getContext().
 888                      getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
 889   Streamer.EmitIntValue(VersionVal, 4);
 890   Streamer.EmitIntValue(ImageInfoFlags, 4);
 891   Streamer.AddBlankLine();
 892 }
 893
 894 static void checkMachOComdat(const GlobalValue *GV) {
 895   const Comdat *C = GV->getComdat();
 896   if (!C)
 897     return;
 898
 899   report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
 900                      "' cannot be lowered.");
 901 }
 902
 903 MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
 904     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
 905   // Parse the section specifier and create it if valid.
 906   StringRef Segment, Section;
 907   unsigned TAA = 0, StubSize = 0;
 908   bool TAAParsed;
 909
 910   checkMachOComdat(GO);
 911
 912   std::string ErrorCode =
 913     MCSectionMachO::ParseSectionSpecifier(GO->getSection(), Segment, Section,
 914                                           TAA, TAAParsed, StubSize);
 915   if (!ErrorCode.empty()) {
 916     // If invalid, report the error with report_fatal_error.
 917     report_fatal_error("Global variable '" + GO->getName() +
 918                        "' has an invalid section specifier '" +
 919                        GO->getSection() + "': " + ErrorCode + ".");
 920   }
 921
 922   // Get the section.
 923   MCSectionMachO *S =
 924       getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
 925
 926   // If TAA wasn't set by ParseSectionSpecifier() above,
 927   // use the value returned by getMachOSection() as a default.
 928   if (!TAAParsed)
 929     TAA = S->getTypeAndAttributes();
 930
 931   // Okay, now that we got the section, verify that the TAA & StubSize agree.
 932   // If the user declared multiple globals with different section flags, we need
 933   // to reject it here.
 934   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
 935     // If invalid, report the error with report_fatal_error.
 936     report_fatal_error("Global variable '" + GO->getName() +
 937                        "' section type or attributes does not match previous"
 938                        " section specifier");
 939   }
 940
 941   return S;
 942 }
 943
 944 MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
 945     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
 946   checkMachOComdat(GO);
 947
 948   // Handle thread local data.
 949   if (Kind.isThreadBSS()) return TLSBSSSection;
 950   if (Kind.isThreadData()) return TLSDataSection;
 951
 952   if (Kind.isText())
 953     return GO->isWeakForLinker() ? TextCoalSection : TextSection;
 954
 955   // If this is weak/linkonce, put this in a coalescable section, either in text
 956   // or data depending on if it is writable.
 957   if (GO->isWeakForLinker()) {
 958     if (Kind.isReadOnly())
 959       return ConstTextCoalSection;
 960     if (Kind.isReadOnlyWithRel())
 961       return ConstDataCoalSection;
 962     return DataCoalSection;
 963   }
 964
 965   // FIXME: Alignment check should be handled by section classifier.
 966   if (Kind.isMergeable1ByteCString() &&
 967       GO->getParent()->getDataLayout().getPreferredAlignment(
 968           cast<GlobalVariable>(GO)) < 32)
 969     return CStringSection;
 970
 971   // Do not put 16-bit arrays in the UString section if they have an
 972   // externally visible label, this runs into issues with certain linker
 973   // versions.
 974   if (Kind.isMergeable2ByteCString() && !GO->hasExternalLinkage() &&
 975       GO->getParent()->getDataLayout().getPreferredAlignment(
 976           cast<GlobalVariable>(GO)) < 32)
 977     return UStringSection;
 978
 979   // With MachO only variables whose corresponding symbol starts with 'l' or
 980   // 'L' can be merged, so we only try merging GVs with private linkage.
 981   if (GO->hasPrivateLinkage() && Kind.isMergeableConst()) {
 982     if (Kind.isMergeableConst4())
 983       return FourByteConstantSection;
 984     if (Kind.isMergeableConst8())
 985       return EightByteConstantSection;
 986     if (Kind.isMergeableConst16())
 987       return SixteenByteConstantSection;
 988   }
 989
 990   // Otherwise, if it is readonly, but not something we can specially optimize,
 991   // just drop it in .const.
 992   if (Kind.isReadOnly())
 993     return ReadOnlySection;
 994
 995   // If this is marked const, put it into a const section.  But if the dynamic
 996   // linker needs to write to it, put it in the data segment.
 997   if (Kind.isReadOnlyWithRel())
 998     return ConstDataSection;
 999
1000   // Put zero initialized globals with strong external linkage in the
1001   // DATA, __common section with the .zerofill directive.
1002   if (Kind.isBSSExtern())
1003     return DataCommonSection;
1004
1005   // Put zero initialized globals with local linkage in __DATA,__bss directive
1006   // with the .zerofill directive (aka .lcomm).
1007   if (Kind.isBSSLocal())
1008     return DataBSSSection;
1009
1010   // Otherwise, just drop the variable in the normal data section.
1011   return DataSection;
1012 }
1013
1014 MCSection *TargetLoweringObjectFileMachO::getSectionForConstant(
1015     const DataLayout &DL, SectionKind Kind, const Constant *C,
1016     unsigned &Align) const {
1017   // If this constant requires a relocation, we have to put it in the data
1018   // segment, not in the text segment.
1019   if (Kind.isData() || Kind.isReadOnlyWithRel())
1020     return ConstDataSection;
1021
1022   if (Kind.isMergeableConst4())
1023     return FourByteConstantSection;
1024   if (Kind.isMergeableConst8())
1025     return EightByteConstantSection;
1026   if (Kind.isMergeableConst16())
1027     return SixteenByteConstantSection;
1028   return ReadOnlySection;  // .const
1029 }
1030
1031 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
1032     const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
1033     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
1034   // The mach-o version of this method defaults to returning a stub reference.
1035
1036   if (Encoding & DW_EH_PE_indirect) {
1037     MachineModuleInfoMachO &MachOMMI =
1038       MMI->getObjFileInfo<MachineModuleInfoMachO>();
1039
1040     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
1041
1042     // Add information about the stub reference to MachOMMI so that the stub
1043     // gets emitted by the asmprinter.
1044     MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
1045     if (!StubSym.getPointer()) {
1046       MCSymbol *Sym = TM.getSymbol(GV);
1047       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
1048     }
1049
1050     return TargetLoweringObjectFile::
1051       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
1052                         Encoding & ~DW_EH_PE_indirect, Streamer);
1053   }
1054
1055   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
1056                                                            MMI, Streamer);
1057 }
1058
1059 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
1060     const GlobalValue *GV, const TargetMachine &TM,
1061     MachineModuleInfo *MMI) const {
1062   // The mach-o version of this method defaults to returning a stub reference.
1063   MachineModuleInfoMachO &MachOMMI =
1064     MMI->getObjFileInfo<MachineModuleInfoMachO>();
1065
1066   MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
1067
1068   // Add information about the stub reference to MachOMMI so that the stub
1069   // gets emitted by the asmprinter.
1070   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
1071   if (!StubSym.getPointer()) {
1072     MCSymbol *Sym = TM.getSymbol(GV);
1073     StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
1074   }
1075
1076   return SSym;
1077 }
1078
1079 const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
1080     const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
1081     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
1082   // Although MachO 32-bit targets do not explicitly have a GOTPCREL relocation
1083   // as 64-bit do, we replace the GOT equivalent by accessing the final symbol
1084   // through a non_lazy_ptr stub instead. One advantage is that it allows the
1085   // computation of deltas to final external symbols. Example:
1086   //
1087   //    _extgotequiv:
1088   //       .long   _extfoo
1089   //
1090   //    _delta:
1091   //       .long   _extgotequiv-_delta
1092   //
1093   // is transformed to:
1094   //
1095   //    _delta:
1096   //       .long   L_extfoo$non_lazy_ptr-(_delta+0)
1097   //
1098   //       .section        __IMPORT,__pointers,non_lazy_symbol_pointers
1099   //    L_extfoo$non_lazy_ptr:
1100   //       .indirect_symbol        _extfoo
1101   //       .long   0
1102   //
1103   MachineModuleInfoMachO &MachOMMI =
1104     MMI->getObjFileInfo<MachineModuleInfoMachO>();
1105   MCContext &Ctx = getContext();
1106
1107   // The offset must consider the original displacement from the base symbol
1108   // since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
1109   Offset = -MV.getConstant();
1110   const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
1111
1112   // Access the final symbol via sym$non_lazy_ptr and generate the appropriated
1113   // non_lazy_ptr stubs.
1114   SmallString<128> Name;
1115   StringRef Suffix = "$non_lazy_ptr";
1116   Name += MMI->getModule()->getDataLayout().getPrivateGlobalPrefix();
1117   Name += Sym->getName();
1118   Name += Suffix;
1119   MCSymbol *Stub = Ctx.getOrCreateSymbol(Name);
1120
1121   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
1122   if (!StubSym.getPointer())
1123     StubSym = MachineModuleInfoImpl::
1124       StubValueTy(const_cast<MCSymbol *>(Sym), true /* access indirectly */);
1125
1126   const MCExpr *BSymExpr =
1127     MCSymbolRefExpr::create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
1128   const MCExpr *LHS =
1129     MCSymbolRefExpr::create(Stub, MCSymbolRefExpr::VK_None, Ctx);
1130
1131   if (!Offset)
1132     return MCBinaryExpr::createSub(LHS, BSymExpr, Ctx);
1133
1134   const MCExpr *RHS =
1135     MCBinaryExpr::createAdd(BSymExpr, MCConstantExpr::create(Offset, Ctx), Ctx);
1136   return MCBinaryExpr::createSub(LHS, RHS, Ctx);
1137 }
1138
1139 static bool canUsePrivateLabel(const MCAsmInfo &AsmInfo,
1140                                const MCSection &Section) {
1141   if (!AsmInfo.isSectionAtomizableBySymbols(Section))
1142     return true;
1143
1144   // If it is not dead stripped, it is safe to use private labels.
1145   const MCSectionMachO &SMO = cast<MCSectionMachO>(Section);
1146   if (SMO.hasAttribute(MachO::S_ATTR_NO_DEAD_STRIP))
1147     return true;
1148
1149   return false;
1150 }
1151
1152 void TargetLoweringObjectFileMachO::getNameWithPrefix(
1153     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
1154     const TargetMachine &TM) const {
1155   bool CannotUsePrivateLabel = true;
1156   if (auto *GO = GV->getBaseObject()) {
1157     SectionKind GOKind = TargetLoweringObjectFile::getKindForGlobal(GO, TM);
1158     const MCSection *TheSection = SectionForGlobal(GO, GOKind, TM);
1159     CannotUsePrivateLabel =
1160         !canUsePrivateLabel(*TM.getMCAsmInfo(), *TheSection);
1161   }
1162   getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1163 }
1164
1165 //===----------------------------------------------------------------------===//
1166 //                                  COFF
1167 //===----------------------------------------------------------------------===//
1168
1169 static unsigned
1170 getCOFFSectionFlags(SectionKind K, const TargetMachine &TM) {
1171   unsigned Flags = 0;
1172   bool isThumb = TM.getTargetTriple().getArch() == Triple::thumb;
1173
1174   if (K.isMetadata())
1175     Flags |=
1176       COFF::IMAGE_SCN_MEM_DISCARDABLE;
1177   else if (K.isText())
1178     Flags |=
1179       COFF::IMAGE_SCN_MEM_EXECUTE |
1180       COFF::IMAGE_SCN_MEM_READ |
1181       COFF::IMAGE_SCN_CNT_CODE |
1182       (isThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0);
1183   else if (K.isBSS())
1184     Flags |=
1185       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
1186       COFF::IMAGE_SCN_MEM_READ |
1187       COFF::IMAGE_SCN_MEM_WRITE;
1188   else if (K.isThreadLocal())
1189     Flags |=
1190       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1191       COFF::IMAGE_SCN_MEM_READ |
1192       COFF::IMAGE_SCN_MEM_WRITE;
1193   else if (K.isReadOnly() || K.isReadOnlyWithRel())
1194     Flags |=
1195       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1196       COFF::IMAGE_SCN_MEM_READ;
1197   else if (K.isWriteable())
1198     Flags |=
1199       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1200       COFF::IMAGE_SCN_MEM_READ |
1201       COFF::IMAGE_SCN_MEM_WRITE;
1202
1203   return Flags;
1204 }
1205
1206 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
1207   const Comdat *C = GV->getComdat();
1208   assert(C && "expected GV to have a Comdat!");
1209
1210   StringRef ComdatGVName = C->getName();
1211   const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
1212   if (!ComdatGV)
1213     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
1214                        "' does not exist.");
1215
1216   if (ComdatGV->getComdat() != C)
1217     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
1218                        "' is not a key for its COMDAT.");
1219
1220   return ComdatGV;
1221 }
1222
1223 static int getSelectionForCOFF(const GlobalValue *GV) {
1224   if (const Comdat *C = GV->getComdat()) {
1225     const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
1226     if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
1227       ComdatKey = GA->getBaseObject();
1228     if (ComdatKey == GV) {
1229       switch (C->getSelectionKind()) {
1230       case Comdat::Any:
1231         return COFF::IMAGE_COMDAT_SELECT_ANY;
1232       case Comdat::ExactMatch:
1233         return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
1234       case Comdat::Largest:
1235         return COFF::IMAGE_COMDAT_SELECT_LARGEST;
1236       case Comdat::NoDuplicates:
1237         return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1238       case Comdat::SameSize:
1239         return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
1240       }
1241     } else {
1242       return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
1243     }
1244   }
1245   return 0;
1246 }
1247
1248 MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
1249     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1250   int Selection = 0;
1251   unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1252   StringRef Name = GO->getSection();
1253   StringRef COMDATSymName = "";
1254   if (GO->hasComdat()) {
1255     Selection = getSelectionForCOFF(GO);
1256     const GlobalValue *ComdatGV;
1257     if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
1258       ComdatGV = getComdatGVForCOFF(GO);
1259     else
1260       ComdatGV = GO;
1261
1262     if (!ComdatGV->hasPrivateLinkage()) {
1263       MCSymbol *Sym = TM.getSymbol(ComdatGV);
1264       COMDATSymName = Sym->getName();
1265       Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1266     } else {
1267       Selection = 0;
1268     }
1269   }
1270
1271   return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
1272                                      Selection);
1273 }
1274
1275 static StringRef getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
1276   if (Kind.isText())
1277     return ".text";
1278   if (Kind.isBSS())
1279     return ".bss";
1280   if (Kind.isThreadLocal())
1281     return ".tls$";
1282   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1283     return ".rdata";
1284   return ".data";
1285 }
1286
1287 MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
1288     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1289   // If we have -ffunction-sections then we should emit the global value to a
1290   // uniqued section specifically for it.
1291   bool EmitUniquedSection;
1292   if (Kind.isText())
1293     EmitUniquedSection = TM.getFunctionSections();
1294   else
1295     EmitUniquedSection = TM.getDataSections();
1296
1297   if ((EmitUniquedSection && !Kind.isCommon()) || GO->hasComdat()) {
1298     SmallString<256> Name = getCOFFSectionNameForUniqueGlobal(Kind);
1299
1300     unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1301
1302     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1303     int Selection = getSelectionForCOFF(GO);
1304     if (!Selection)
1305       Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1306     const GlobalValue *ComdatGV;
1307     if (GO->hasComdat())
1308       ComdatGV = getComdatGVForCOFF(GO);
1309     else
1310       ComdatGV = GO;
1311
1312     unsigned UniqueID = MCContext::GenericSectionID;
1313     if (EmitUniquedSection)
1314       UniqueID = NextUniqueID++;
1315
1316     if (!ComdatGV->hasPrivateLinkage()) {
1317       MCSymbol *Sym = TM.getSymbol(ComdatGV);
1318       StringRef COMDATSymName = Sym->getName();
1319
1320       // Append "$symbol" to the section name when targetting mingw. The ld.bfd
1321       // COFF linker will not properly handle comdats otherwise.
1322       if (getTargetTriple().isWindowsGNUEnvironment())
1323         raw_svector_ostream(Name) << '$' << COMDATSymName;
1324
1325       return getContext().getCOFFSection(Name, Characteristics, Kind,
1326                                          COMDATSymName, Selection, UniqueID);
1327     } else {
1328       SmallString<256> TmpData;
1329       getMangler().getNameWithPrefix(TmpData, GO, /*CannotUsePrivateLabel=*/true);
1330       return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
1331                                          Selection, UniqueID);
1332     }
1333   }
1334
1335   if (Kind.isText())
1336     return TextSection;
1337
1338   if (Kind.isThreadLocal())
1339     return TLSDataSection;
1340
1341   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1342     return ReadOnlySection;
1343
1344   // Note: we claim that common symbols are put in BSSSection, but they are
1345   // really emitted with the magic .comm directive, which creates a symbol table
1346   // entry but not a section.
1347   if (Kind.isBSS() || Kind.isCommon())
1348     return BSSSection;
1349
1350   return DataSection;
1351 }
1352
1353 void TargetLoweringObjectFileCOFF::getNameWithPrefix(
1354     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
1355     const TargetMachine &TM) const {
1356   bool CannotUsePrivateLabel = false;
1357   if (GV->hasPrivateLinkage() &&
1358       ((isa<Function>(GV) && TM.getFunctionSections()) ||
1359        (isa<GlobalVariable>(GV) && TM.getDataSections())))
1360     CannotUsePrivateLabel = true;
1361
1362   getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1363 }
1364
1365 MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
1366     const Function &F, const TargetMachine &TM) const {
1367   // If the function can be removed, produce a unique section so that
1368   // the table doesn't prevent the removal.
1369   const Comdat *C = F.getComdat();
1370   bool EmitUniqueSection = TM.getFunctionSections() || C;
1371   if (!EmitUniqueSection)
1372     return ReadOnlySection;
1373
1374   // FIXME: we should produce a symbol for F instead.
1375   if (F.hasPrivateLinkage())
1376     return ReadOnlySection;
1377
1378   MCSymbol *Sym = TM.getSymbol(&F);
1379   StringRef COMDATSymName = Sym->getName();
1380
1381   SectionKind Kind = SectionKind::getReadOnly();
1382   StringRef SecName = getCOFFSectionNameForUniqueGlobal(Kind);
1383   unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1384   Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1385   unsigned UniqueID = NextUniqueID++;
1386
1387   return getContext().getCOFFSection(
1388       SecName, Characteristics, Kind, COMDATSymName,
1389       COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
1390 }
1391
1392 void TargetLoweringObjectFileCOFF::emitModuleMetadata(MCStreamer &Streamer,
1393                                                       Module &M) const {
1394   if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
1395     // Emit the linker options to the linker .drectve section.  According to the
1396     // spec, this section is a space-separated string containing flags for
1397     // linker.
1398     MCSection *Sec = getDrectveSection();
1399     Streamer.SwitchSection(Sec);
1400     for (const auto &Option : LinkerOptions->operands()) {
1401       for (const auto &Piece : cast<MDNode>(Option)->operands()) {
1402         // Lead with a space for consistency with our dllexport implementation.
1403         std::string Directive(" ");
1404         Directive.append(cast<MDString>(Piece)->getString());
1405         Streamer.EmitBytes(Directive);
1406       }
1407     }
1408   }
1409
1410   unsigned Version = 0;
1411   unsigned Flags = 0;
1412   StringRef Section;
1413
1414   GetObjCImageInfo(M, Version, Flags, Section);
1415   if (Section.empty())
1416     return;
1417
1418   auto &C = getContext();
1419   auto *S = C.getCOFFSection(
1420       Section, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
1421       SectionKind::getReadOnly());
1422   Streamer.SwitchSection(S);
1423   Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
1424   Streamer.EmitIntValue(Version, 4);
1425   Streamer.EmitIntValue(Flags, 4);
1426   Streamer.AddBlankLine();
1427 }
1428
1429 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
1430                                               const TargetMachine &TM) {
1431   TargetLoweringObjectFile::Initialize(Ctx, TM);
1432   const Triple &T = TM.getTargetTriple();
1433   if (T.isKnownWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
1434     StaticCtorSection =
1435         Ctx.getCOFFSection(".CRT$XCU", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1436                                            COFF::IMAGE_SCN_MEM_READ,
1437                            SectionKind::getReadOnly());
1438     StaticDtorSection =
1439         Ctx.getCOFFSection(".CRT$XTX", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1440                                            COFF::IMAGE_SCN_MEM_READ,
1441                            SectionKind::getReadOnly());
1442   } else {
1443     StaticCtorSection = Ctx.getCOFFSection(
1444         ".ctors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1445                       COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1446         SectionKind::getData());
1447     StaticDtorSection = Ctx.getCOFFSection(
1448         ".dtors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1449                       COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1450         SectionKind::getData());
1451   }
1452 }
1453
1454 static MCSectionCOFF *getCOFFStaticStructorSection(MCContext &Ctx,
1455                                                    const Triple &T, bool IsCtor,
1456                                                    unsigned Priority,
1457                                                    const MCSymbol *KeySym,
1458                                                    MCSectionCOFF *Default) {
1459   if (T.isKnownWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
1460     // If the priority is the default, use .CRT$XCU, possibly associative.
1461     if (Priority == 65535)
1462       return Ctx.getAssociativeCOFFSection(Default, KeySym, 0);
1463
1464     // Otherwise, we need to compute a new section name. Low priorities should
1465     // run earlier. The linker will sort sections ASCII-betically, and we need a
1466     // string that sorts between .CRT$XCA and .CRT$XCU. In the general case, we
1467     // make a name like ".CRT$XCT12345", since that runs before .CRT$XCU. Really
1468     // low priorities need to sort before 'L', since the CRT uses that
1469     // internally, so we use ".CRT$XCA00001" for them.
1470     SmallString<24> Name;
1471     raw_svector_ostream OS(Name);
1472     OS << ".CRT$XC" << (Priority < 200 ? 'A' : 'T') << format("%05u", Priority);
1473     MCSectionCOFF *Sec = Ctx.getCOFFSection(
1474         Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
1475         SectionKind::getReadOnly());
1476     return Ctx.getAssociativeCOFFSection(Sec, KeySym, 0);
1477   }
1478
1479   std::string Name = IsCtor ? ".ctors" : ".dtors";
1480   if (Priority != 65535)
1481     raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
1482
1483   return Ctx.getAssociativeCOFFSection(
1484       Ctx.getCOFFSection(Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1485                                    COFF::IMAGE_SCN_MEM_READ |
1486                                    COFF::IMAGE_SCN_MEM_WRITE,
1487                          SectionKind::getData()),
1488       KeySym, 0);
1489 }
1490
1491 MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
1492     unsigned Priority, const MCSymbol *KeySym) const {
1493   return getCOFFStaticStructorSection(getContext(), getTargetTriple(), true,
1494                                       Priority, KeySym,
1495                                       cast<MCSectionCOFF>(StaticCtorSection));
1496 }
1497
1498 MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
1499     unsigned Priority, const MCSymbol *KeySym) const {
1500   return getCOFFStaticStructorSection(getContext(), getTargetTriple(), false,
1501                                       Priority, KeySym,
1502                                       cast<MCSectionCOFF>(StaticDtorSection));
1503 }
1504
1505 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
1506     raw_ostream &OS, const GlobalValue *GV) const {
1507   emitLinkerFlagsForGlobalCOFF(OS, GV, getTargetTriple(), getMangler());
1508 }
1509
1510 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForUsed(
1511     raw_ostream &OS, const GlobalValue *GV) const {
1512   emitLinkerFlagsForUsedCOFF(OS, GV, getTargetTriple(), getMangler());
1513 }
1514
1515 const MCExpr *TargetLoweringObjectFileCOFF::lowerRelativeReference(
1516     const GlobalValue *LHS, const GlobalValue *RHS,
1517     const TargetMachine &TM) const {
1518   const Triple &T = TM.getTargetTriple();
1519   if (!T.isKnownWindowsMSVCEnvironment() &&
1520       !T.isWindowsItaniumEnvironment() &&
1521       !T.isWindowsCoreCLREnvironment())
1522     return nullptr;
1523
1524   // Our symbols should exist in address space zero, cowardly no-op if
1525   // otherwise.
1526   if (LHS->getType()->getPointerAddressSpace() != 0 ||
1527       RHS->getType()->getPointerAddressSpace() != 0)
1528     return nullptr;
1529
1530   // Both ptrtoint instructions must wrap global objects:
1531   // - Only global variables are eligible for image relative relocations.
1532   // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
1533   // We expect __ImageBase to be a global variable without a section, externally
1534   // defined.
1535   //
1536   // It should look something like this: @__ImageBase = external constant i8
1537   if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) ||
1538       LHS->isThreadLocal() || RHS->isThreadLocal() ||
1539       RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() ||
1540       cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection())
1541     return nullptr;
1542
1543   return MCSymbolRefExpr::create(TM.getSymbol(LHS),
1544                                  MCSymbolRefExpr::VK_COFF_IMGREL32,
1545                                  getContext());
1546 }
1547
1548 static std::string APIntToHexString(const APInt &AI) {
1549   unsigned Width = (AI.getBitWidth() / 8) * 2;
1550   std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true);
1551   unsigned Size = HexString.size();
1552   assert(Width >= Size && "hex string is too large!");
1553   HexString.insert(HexString.begin(), Width - Size, '0');
1554
1555   return HexString;
1556 }
1557
1558 static std::string scalarConstantToHexString(const Constant *C) {
1559   Type *Ty = C->getType();
1560   if (isa<UndefValue>(C)) {
1561     return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits()));
1562   } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) {
1563     return APIntToHexString(CFP->getValueAPF().bitcastToAPInt());
1564   } else if (const auto *CI = dyn_cast<ConstantInt>(C)) {
1565     return APIntToHexString(CI->getValue());
1566   } else {
1567     unsigned NumElements;
1568     if (isa<VectorType>(Ty))
1569       NumElements = Ty->getVectorNumElements();
1570     else
1571       NumElements = Ty->getArrayNumElements();
1572     std::string HexString;
1573     for (int I = NumElements - 1, E = -1; I != E; --I)
1574       HexString += scalarConstantToHexString(C->getAggregateElement(I));
1575     return HexString;
1576   }
1577 }
1578
1579 MCSection *TargetLoweringObjectFileCOFF::getSectionForConstant(
1580     const DataLayout &DL, SectionKind Kind, const Constant *C,
1581     unsigned &Align) const {
1582   if (Kind.isMergeableConst() && C &&
1583       getContext().getAsmInfo()->hasCOFFComdatConstants()) {
1584     // This creates comdat sections with the given symbol name, but unless
1585     // AsmPrinter::GetCPISymbol actually makes the symbol global, the symbol
1586     // will be created with a null storage class, which makes GNU binutils
1587     // error out.
1588     const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1589                                      COFF::IMAGE_SCN_MEM_READ |
1590                                      COFF::IMAGE_SCN_LNK_COMDAT;
1591     std::string COMDATSymName;
1592     if (Kind.isMergeableConst4()) {
1593       if (Align <= 4) {
1594         COMDATSymName = "__real@" + scalarConstantToHexString(C);
1595         Align = 4;
1596       }
1597     } else if (Kind.isMergeableConst8()) {
1598       if (Align <= 8) {
1599         COMDATSymName = "__real@" + scalarConstantToHexString(C);
1600         Align = 8;
1601       }
1602     } else if (Kind.isMergeableConst16()) {
1603       // FIXME: These may not be appropriate for non-x86 architectures.
1604       if (Align <= 16) {
1605         COMDATSymName = "__xmm@" + scalarConstantToHexString(C);
1606         Align = 16;
1607       }
1608     } else if (Kind.isMergeableConst32()) {
1609       if (Align <= 32) {
1610         COMDATSymName = "__ymm@" + scalarConstantToHexString(C);
1611         Align = 32;
1612       }
1613     }
1614
1615     if (!COMDATSymName.empty())
1616       return getContext().getCOFFSection(".rdata", Characteristics, Kind,
1617                                          COMDATSymName,
1618                                          COFF::IMAGE_COMDAT_SELECT_ANY);
1619   }
1620
1621   return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C, Align);
1622 }
1623
1624
1625 //===----------------------------------------------------------------------===//
1626 //                                  Wasm
1627 //===----------------------------------------------------------------------===//
1628
1629 static const Comdat *getWasmComdat(const GlobalValue *GV) {
1630   const Comdat *C = GV->getComdat();
1631   if (!C)
1632     return nullptr;
1633
1634   if (C->getSelectionKind() != Comdat::Any)
1635     report_fatal_error("WebAssembly COMDATs only support "
1636                        "SelectionKind::Any, '" + C->getName() + "' cannot be "
1637                        "lowered.");
1638
1639   return C;
1640 }
1641
1642 static SectionKind getWasmKindForNamedSection(StringRef Name, SectionKind K) {
1643   // If we're told we have function data, then use that.
1644   if (K.isText())
1645     return SectionKind::getText();
1646
1647   // Otherwise, ignore whatever section type the generic impl detected and use
1648   // a plain data section.
1649   return SectionKind::getData();
1650 }
1651
1652 MCSection *TargetLoweringObjectFileWasm::getExplicitSectionGlobal(
1653     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1654   // We don't support explict section names for functions in the wasm object
1655   // format.  Each function has to be in its own unique section.
1656   if (isa<Function>(GO)) {
1657     return SelectSectionForGlobal(GO, Kind, TM);
1658   }
1659
1660   StringRef Name = GO->getSection();
1661
1662   Kind = getWasmKindForNamedSection(Name, Kind);
1663
1664   StringRef Group = "";
1665   if (const Comdat *C = getWasmComdat(GO)) {
1666     Group = C->getName();
1667   }
1668
1669   return getContext().getWasmSection(Name, Kind, Group,
1670                                      MCContext::GenericSectionID);
1671 }
1672
1673 static MCSectionWasm *selectWasmSectionForGlobal(
1674     MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
1675     const TargetMachine &TM, bool EmitUniqueSection, unsigned *NextUniqueID) {
1676   StringRef Group = "";
1677   if (const Comdat *C = getWasmComdat(GO)) {
1678     Group = C->getName();
1679   }
1680
1681   bool UniqueSectionNames = TM.getUniqueSectionNames();
1682   SmallString<128> Name = getSectionPrefixForGlobal(Kind);
1683
1684   if (const auto *F = dyn_cast<Function>(GO)) {
1685     const auto &OptionalPrefix = F->getSectionPrefix();
1686     if (OptionalPrefix)
1687       Name += *OptionalPrefix;
1688   }
1689
1690   if (EmitUniqueSection && UniqueSectionNames) {
1691     Name.push_back('.');
1692     TM.getNameWithPrefix(Name, GO, Mang, true);
1693   }
1694   unsigned UniqueID = MCContext::GenericSectionID;
1695   if (EmitUniqueSection && !UniqueSectionNames) {
1696     UniqueID = *NextUniqueID;
1697     (*NextUniqueID)++;
1698   }
1699   return Ctx.getWasmSection(Name, Kind, Group, UniqueID);
1700 }
1701
1702 MCSection *TargetLoweringObjectFileWasm::SelectSectionForGlobal(
1703     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1704
1705   if (Kind.isCommon())
1706     report_fatal_error("mergable sections not supported yet on wasm");
1707
1708   // If we have -ffunction-section or -fdata-section then we should emit the
1709   // global value to a uniqued section specifically for it.
1710   bool EmitUniqueSection = false;
1711   if (Kind.isText())
1712     EmitUniqueSection = TM.getFunctionSections();
1713   else
1714     EmitUniqueSection = TM.getDataSections();
1715   EmitUniqueSection |= GO->hasComdat();
1716
1717   return selectWasmSectionForGlobal(getContext(), GO, Kind, getMangler(), TM,
1718                                     EmitUniqueSection, &NextUniqueID);
1719 }
1720
1721 bool TargetLoweringObjectFileWasm::shouldPutJumpTableInFunctionSection(
1722     bool UsesLabelDifference, const Function &F) const {
1723   // We can always create relative relocations, so use another section
1724   // that can be marked non-executable.
1725   return false;
1726 }
1727
1728 const MCExpr *TargetLoweringObjectFileWasm::lowerRelativeReference(
1729     const GlobalValue *LHS, const GlobalValue *RHS,
1730     const TargetMachine &TM) const {
1731   // We may only use a PLT-relative relocation to refer to unnamed_addr
1732   // functions.
1733   if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
1734     return nullptr;
1735
1736   // Basic sanity checks.
1737   if (LHS->getType()->getPointerAddressSpace() != 0 ||
1738       RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
1739       RHS->isThreadLocal())
1740     return nullptr;
1741
1742   return MCBinaryExpr::createSub(
1743       MCSymbolRefExpr::create(TM.getSymbol(LHS), MCSymbolRefExpr::VK_None,
1744                               getContext()),
1745       MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
1746 }
1747
1748 void TargetLoweringObjectFileWasm::InitializeWasm() {
1749   StaticCtorSection =
1750       getContext().getWasmSection(".init_array", SectionKind::getData());
1751 }
1752
1753 MCSection *TargetLoweringObjectFileWasm::getStaticCtorSection(
1754     unsigned Priority, const MCSymbol *KeySym) const {
1755   return Priority == UINT16_MAX ?
1756          StaticCtorSection :
1757          getContext().getWasmSection(".init_array." + utostr(Priority),
1758                                      SectionKind::getData());
1759 }
1760
1761 MCSection *TargetLoweringObjectFileWasm::getStaticDtorSection(
1762     unsigned Priority, const MCSymbol *KeySym) const {
1763   llvm_unreachable("@llvm.global_dtors should have been lowered already");
1764   return nullptr;
1765 }