lib/MC/MCContext.cpp

   1 //===- lib/MC/MCContext.cpp - Machine Code Context ------------------------===//
   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 #include "llvm/MC/MCContext.h"
  11 #include "llvm/ADT/Optional.h"
  12 #include "llvm/ADT/SmallString.h"
  13 #include "llvm/ADT/SmallVector.h"
  14 #include "llvm/ADT/StringMap.h"
  15 #include "llvm/ADT/StringRef.h"
  16 #include "llvm/ADT/Twine.h"
  17 #include "llvm/BinaryFormat/COFF.h"
  18 #include "llvm/BinaryFormat/ELF.h"
  19 #include "llvm/MC/MCAsmInfo.h"
  20 #include "llvm/MC/MCCodeView.h"
  21 #include "llvm/MC/MCDwarf.h"
  22 #include "llvm/MC/MCExpr.h"
  23 #include "llvm/MC/MCFragment.h"
  24 #include "llvm/MC/MCLabel.h"
  25 #include "llvm/MC/MCObjectFileInfo.h"
  26 #include "llvm/MC/MCSectionCOFF.h"
  27 #include "llvm/MC/MCSectionELF.h"
  28 #include "llvm/MC/MCSectionMachO.h"
  29 #include "llvm/MC/MCSectionWasm.h"
  30 #include "llvm/MC/MCStreamer.h"
  31 #include "llvm/MC/MCSymbol.h"
  32 #include "llvm/MC/MCSymbolCOFF.h"
  33 #include "llvm/MC/MCSymbolELF.h"
  34 #include "llvm/MC/MCSymbolMachO.h"
  35 #include "llvm/MC/MCSymbolWasm.h"
  36 #include "llvm/MC/SectionKind.h"
  37 #include "llvm/Support/Casting.h"
  38 #include "llvm/Support/CommandLine.h"
  39 #include "llvm/Support/ErrorHandling.h"
  40 #include "llvm/Support/MemoryBuffer.h"
  41 #include "llvm/Support/Signals.h"
  42 #include "llvm/Support/SourceMgr.h"
  43 #include "llvm/Support/raw_ostream.h"
  44 #include <cassert>
  45 #include <cstdlib>
  46 #include <tuple>
  47 #include <utility>
  48
  49 using namespace llvm;
  50
  51 static cl::opt<char*>
  52 AsSecureLogFileName("as-secure-log-file-name",
  53         cl::desc("As secure log file name (initialized from "
  54                  "AS_SECURE_LOG_FILE env variable)"),
  55         cl::init(getenv("AS_SECURE_LOG_FILE")), cl::Hidden);
  56
  57 MCContext::MCContext(const MCAsmInfo *mai, const MCRegisterInfo *mri,
  58                      const MCObjectFileInfo *mofi, const SourceMgr *mgr,
  59                      bool DoAutoReset)
  60     : SrcMgr(mgr), InlineSrcMgr(nullptr), MAI(mai), MRI(mri), MOFI(mofi),
  61       Symbols(Allocator), UsedNames(Allocator),
  62       CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0),
  63       AutoReset(DoAutoReset) {
  64   SecureLogFile = AsSecureLogFileName;
  65
  66   if (SrcMgr && SrcMgr->getNumBuffers())
  67     MainFileName =
  68         SrcMgr->getMemoryBuffer(SrcMgr->getMainFileID())->getBufferIdentifier();
  69 }
  70
  71 MCContext::~MCContext() {
  72   if (AutoReset)
  73     reset();
  74
  75   // NOTE: The symbols are all allocated out of a bump pointer allocator,
  76   // we don't need to free them here.
  77 }
  78
  79 //===----------------------------------------------------------------------===//
  80 // Module Lifetime Management
  81 //===----------------------------------------------------------------------===//
  82
  83 void MCContext::reset() {
  84   // Call the destructors so the fragments are freed
  85   COFFAllocator.DestroyAll();
  86   ELFAllocator.DestroyAll();
  87   MachOAllocator.DestroyAll();
  88
  89   MCSubtargetAllocator.DestroyAll();
  90   UsedNames.clear();
  91   Symbols.clear();
  92   Allocator.Reset();
  93   Instances.clear();
  94   CompilationDir.clear();
  95   MainFileName.clear();
  96   MCDwarfLineTablesCUMap.clear();
  97   SectionsForRanges.clear();
  98   MCGenDwarfLabelEntries.clear();
  99   DwarfDebugFlags = StringRef();
 100   DwarfCompileUnitID = 0;
 101   CurrentDwarfLoc = MCDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0);
 102
 103   CVContext.reset();
 104
 105   MachOUniquingMap.clear();
 106   ELFUniquingMap.clear();
 107   COFFUniquingMap.clear();
 108   WasmUniquingMap.clear();
 109
 110   NextID.clear();
 111   AllowTemporaryLabels = true;
 112   DwarfLocSeen = false;
 113   GenDwarfForAssembly = false;
 114   GenDwarfFileNumber = 0;
 115
 116   HadError = false;
 117 }
 118
 119 //===----------------------------------------------------------------------===//
 120 // Symbol Manipulation
 121 //===----------------------------------------------------------------------===//
 122
 123 MCSymbol *MCContext::getOrCreateSymbol(const Twine &Name) {
 124   SmallString<128> NameSV;
 125   StringRef NameRef = Name.toStringRef(NameSV);
 126
 127   assert(!NameRef.empty() && "Normal symbols cannot be unnamed!");
 128
 129   MCSymbol *&Sym = Symbols[NameRef];
 130   if (!Sym)
 131     Sym = createSymbol(NameRef, false, false);
 132
 133   return Sym;
 134 }
 135
 136 MCSymbol *MCContext::getOrCreateFrameAllocSymbol(StringRef FuncName,
 137                                                  unsigned Idx) {
 138   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
 139                            "$frame_escape_" + Twine(Idx));
 140 }
 141
 142 MCSymbol *MCContext::getOrCreateParentFrameOffsetSymbol(StringRef FuncName) {
 143   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
 144                            "$parent_frame_offset");
 145 }
 146
 147 MCSymbol *MCContext::getOrCreateLSDASymbol(StringRef FuncName) {
 148   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + "__ehtable$" +
 149                            FuncName);
 150 }
 151
 152 MCSymbol *MCContext::createSymbolImpl(const StringMapEntry<bool> *Name,
 153                                       bool IsTemporary) {
 154   if (MOFI) {
 155     switch (MOFI->getObjectFileType()) {
 156     case MCObjectFileInfo::IsCOFF:
 157       return new (Name, *this) MCSymbolCOFF(Name, IsTemporary);
 158     case MCObjectFileInfo::IsELF:
 159       return new (Name, *this) MCSymbolELF(Name, IsTemporary);
 160     case MCObjectFileInfo::IsMachO:
 161       return new (Name, *this) MCSymbolMachO(Name, IsTemporary);
 162     case MCObjectFileInfo::IsWasm:
 163       return new (Name, *this) MCSymbolWasm(Name, IsTemporary);
 164     }
 165   }
 166   return new (Name, *this) MCSymbol(MCSymbol::SymbolKindUnset, Name,
 167                                     IsTemporary);
 168 }
 169
 170 MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
 171                                   bool CanBeUnnamed) {
 172   if (CanBeUnnamed && !UseNamesOnTempLabels)
 173     return createSymbolImpl(nullptr, true);
 174
 175   // Determine whether this is a user written assembler temporary or normal
 176   // label, if used.
 177   bool IsTemporary = CanBeUnnamed;
 178   if (AllowTemporaryLabels && !IsTemporary)
 179     IsTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
 180
 181   SmallString<128> NewName = Name;
 182   bool AddSuffix = AlwaysAddSuffix;
 183   unsigned &NextUniqueID = NextID[Name];
 184   while (true) {
 185     if (AddSuffix) {
 186       NewName.resize(Name.size());
 187       raw_svector_ostream(NewName) << NextUniqueID++;
 188     }
 189     auto NameEntry = UsedNames.insert(std::make_pair(NewName, true));
 190     if (NameEntry.second || !NameEntry.first->second) {
 191       // Ok, we found a name.
 192       // Mark it as used for a non-section symbol.
 193       NameEntry.first->second = true;
 194       // Have the MCSymbol object itself refer to the copy of the string that is
 195       // embedded in the UsedNames entry.
 196       return createSymbolImpl(&*NameEntry.first, IsTemporary);
 197     }
 198     assert(IsTemporary && "Cannot rename non-temporary symbols");
 199     AddSuffix = true;
 200   }
 201   llvm_unreachable("Infinite loop");
 202 }
 203
 204 MCSymbol *MCContext::createTempSymbol(const Twine &Name, bool AlwaysAddSuffix,
 205                                       bool CanBeUnnamed) {
 206   SmallString<128> NameSV;
 207   raw_svector_ostream(NameSV) << MAI->getPrivateGlobalPrefix() << Name;
 208   return createSymbol(NameSV, AlwaysAddSuffix, CanBeUnnamed);
 209 }
 210
 211 MCSymbol *MCContext::createLinkerPrivateTempSymbol() {
 212   SmallString<128> NameSV;
 213   raw_svector_ostream(NameSV) << MAI->getLinkerPrivateGlobalPrefix() << "tmp";
 214   return createSymbol(NameSV, true, false);
 215 }
 216
 217 MCSymbol *MCContext::createTempSymbol(bool CanBeUnnamed) {
 218   return createTempSymbol("tmp", true, CanBeUnnamed);
 219 }
 220
 221 unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
 222   MCLabel *&Label = Instances[LocalLabelVal];
 223   if (!Label)
 224     Label = new (*this) MCLabel(0);
 225   return Label->incInstance();
 226 }
 227
 228 unsigned MCContext::GetInstance(unsigned LocalLabelVal) {
 229   MCLabel *&Label = Instances[LocalLabelVal];
 230   if (!Label)
 231     Label = new (*this) MCLabel(0);
 232   return Label->getInstance();
 233 }
 234
 235 MCSymbol *MCContext::getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
 236                                                        unsigned Instance) {
 237   MCSymbol *&Sym = LocalSymbols[std::make_pair(LocalLabelVal, Instance)];
 238   if (!Sym)
 239     Sym = createTempSymbol(false);
 240   return Sym;
 241 }
 242
 243 MCSymbol *MCContext::createDirectionalLocalSymbol(unsigned LocalLabelVal) {
 244   unsigned Instance = NextInstance(LocalLabelVal);
 245   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
 246 }
 247
 248 MCSymbol *MCContext::getDirectionalLocalSymbol(unsigned LocalLabelVal,
 249                                                bool Before) {
 250   unsigned Instance = GetInstance(LocalLabelVal);
 251   if (!Before)
 252     ++Instance;
 253   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
 254 }
 255
 256 MCSymbol *MCContext::lookupSymbol(const Twine &Name) const {
 257   SmallString<128> NameSV;
 258   StringRef NameRef = Name.toStringRef(NameSV);
 259   return Symbols.lookup(NameRef);
 260 }
 261
 262 void MCContext::setSymbolValue(MCStreamer &Streamer,
 263                               StringRef Sym,
 264                               uint64_t Val) {
 265   auto Symbol = getOrCreateSymbol(Sym);
 266   Streamer.EmitAssignment(Symbol, MCConstantExpr::create(Val, *this));
 267 }
 268
 269 //===----------------------------------------------------------------------===//
 270 // Section Management
 271 //===----------------------------------------------------------------------===//
 272
 273 MCSectionMachO *MCContext::getMachOSection(StringRef Segment, StringRef Section,
 274                                            unsigned TypeAndAttributes,
 275                                            unsigned Reserved2, SectionKind Kind,
 276                                            const char *BeginSymName) {
 277   // We unique sections by their segment/section pair.  The returned section
 278   // may not have the same flags as the requested section, if so this should be
 279   // diagnosed by the client as an error.
 280
 281   // Form the name to look up.
 282   SmallString<64> Name;
 283   Name += Segment;
 284   Name.push_back(',');
 285   Name += Section;
 286
 287   // Do the lookup, if we have a hit, return it.
 288   MCSectionMachO *&Entry = MachOUniquingMap[Name];
 289   if (Entry)
 290     return Entry;
 291
 292   MCSymbol *Begin = nullptr;
 293   if (BeginSymName)
 294     Begin = createTempSymbol(BeginSymName, false);
 295
 296   // Otherwise, return a new section.
 297   return Entry = new (MachOAllocator.Allocate()) MCSectionMachO(
 298              Segment, Section, TypeAndAttributes, Reserved2, Kind, Begin);
 299 }
 300
 301 void MCContext::renameELFSection(MCSectionELF *Section, StringRef Name) {
 302   StringRef GroupName;
 303   if (const MCSymbol *Group = Section->getGroup())
 304     GroupName = Group->getName();
 305
 306   unsigned UniqueID = Section->getUniqueID();
 307   ELFUniquingMap.erase(
 308       ELFSectionKey{Section->getSectionName(), GroupName, UniqueID});
 309   auto I = ELFUniquingMap.insert(std::make_pair(
 310                                      ELFSectionKey{Name, GroupName, UniqueID},
 311                                      Section))
 312                .first;
 313   StringRef CachedName = I->first.SectionName;
 314   const_cast<MCSectionELF *>(Section)->setSectionName(CachedName);
 315 }
 316
 317 MCSectionELF *MCContext::createELFSectionImpl(StringRef Section, unsigned Type,
 318                                               unsigned Flags, SectionKind K,
 319                                               unsigned EntrySize,
 320                                               const MCSymbolELF *Group,
 321                                               unsigned UniqueID,
 322                                               const MCSymbolELF *Associated) {
 323   MCSymbolELF *R;
 324   MCSymbol *&Sym = Symbols[Section];
 325   // A section symbol can not redefine regular symbols. There may be multiple
 326   // sections with the same name, in which case the first such section wins.
 327   if (Sym && Sym->isDefined() &&
 328       (!Sym->isInSection() || Sym->getSection().getBeginSymbol() != Sym))
 329     reportError(SMLoc(), "invalid symbol redefinition");
 330   if (Sym && Sym->isUndefined()) {
 331     R = cast<MCSymbolELF>(Sym);
 332   } else {
 333     auto NameIter = UsedNames.insert(std::make_pair(Section, false)).first;
 334     R = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
 335     if (!Sym)
 336       Sym = R;
 337   }
 338   R->setBinding(ELF::STB_LOCAL);
 339   R->setType(ELF::STT_SECTION);
 340
 341   auto *Ret = new (ELFAllocator.Allocate()) MCSectionELF(
 342       Section, Type, Flags, K, EntrySize, Group, UniqueID, R, Associated);
 343
 344   auto *F = new MCDataFragment();
 345   Ret->getFragmentList().insert(Ret->begin(), F);
 346   F->setParent(Ret);
 347   R->setFragment(F);
 348
 349   return Ret;
 350 }
 351
 352 MCSectionELF *MCContext::createELFRelSection(const Twine &Name, unsigned Type,
 353                                              unsigned Flags, unsigned EntrySize,
 354                                              const MCSymbolELF *Group,
 355                                              const MCSectionELF *RelInfoSection) {
 356   StringMap<bool>::iterator I;
 357   bool Inserted;
 358   std::tie(I, Inserted) =
 359       RelSecNames.insert(std::make_pair(Name.str(), true));
 360
 361   return createELFSectionImpl(
 362       I->getKey(), Type, Flags, SectionKind::getReadOnly(), EntrySize, Group,
 363       true, cast<MCSymbolELF>(RelInfoSection->getBeginSymbol()));
 364 }
 365
 366 MCSectionELF *MCContext::getELFNamedSection(const Twine &Prefix,
 367                                             const Twine &Suffix, unsigned Type,
 368                                             unsigned Flags,
 369                                             unsigned EntrySize) {
 370   return getELFSection(Prefix + "." + Suffix, Type, Flags, EntrySize, Suffix);
 371 }
 372
 373 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
 374                                        unsigned Flags, unsigned EntrySize,
 375                                        const Twine &Group, unsigned UniqueID,
 376                                        const MCSymbolELF *Associated) {
 377   MCSymbolELF *GroupSym = nullptr;
 378   if (!Group.isTriviallyEmpty() && !Group.str().empty())
 379     GroupSym = cast<MCSymbolELF>(getOrCreateSymbol(Group));
 380
 381   return getELFSection(Section, Type, Flags, EntrySize, GroupSym, UniqueID,
 382                        Associated);
 383 }
 384
 385 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
 386                                        unsigned Flags, unsigned EntrySize,
 387                                        const MCSymbolELF *GroupSym,
 388                                        unsigned UniqueID,
 389                                        const MCSymbolELF *Associated) {
 390   StringRef Group = "";
 391   if (GroupSym)
 392     Group = GroupSym->getName();
 393   // Do the lookup, if we have a hit, return it.
 394   auto IterBool = ELFUniquingMap.insert(
 395       std::make_pair(ELFSectionKey{Section.str(), Group, UniqueID}, nullptr));
 396   auto &Entry = *IterBool.first;
 397   if (!IterBool.second)
 398     return Entry.second;
 399
 400   StringRef CachedName = Entry.first.SectionName;
 401
 402   SectionKind Kind;
 403   if (Flags & ELF::SHF_ARM_PURECODE)
 404     Kind = SectionKind::getExecuteOnly();
 405   else if (Flags & ELF::SHF_EXECINSTR)
 406     Kind = SectionKind::getText();
 407   else
 408     Kind = SectionKind::getReadOnly();
 409
 410   MCSectionELF *Result = createELFSectionImpl(
 411       CachedName, Type, Flags, Kind, EntrySize, GroupSym, UniqueID, Associated);
 412   Entry.second = Result;
 413   return Result;
 414 }
 415
 416 MCSectionELF *MCContext::createELFGroupSection(const MCSymbolELF *Group) {
 417   return createELFSectionImpl(".group", ELF::SHT_GROUP, 0,
 418                               SectionKind::getReadOnly(), 4, Group, ~0,
 419                               nullptr);
 420 }
 421
 422 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
 423                                          unsigned Characteristics,
 424                                          SectionKind Kind,
 425                                          StringRef COMDATSymName, int Selection,
 426                                          unsigned UniqueID,
 427                                          const char *BeginSymName) {
 428   MCSymbol *COMDATSymbol = nullptr;
 429   if (!COMDATSymName.empty()) {
 430     COMDATSymbol = getOrCreateSymbol(COMDATSymName);
 431     COMDATSymName = COMDATSymbol->getName();
 432   }
 433
 434
 435   // Do the lookup, if we have a hit, return it.
 436   COFFSectionKey T{Section, COMDATSymName, Selection, UniqueID};
 437   auto IterBool = COFFUniquingMap.insert(std::make_pair(T, nullptr));
 438   auto Iter = IterBool.first;
 439   if (!IterBool.second)
 440     return Iter->second;
 441
 442   MCSymbol *Begin = nullptr;
 443   if (BeginSymName)
 444     Begin = createTempSymbol(BeginSymName, false);
 445
 446   StringRef CachedName = Iter->first.SectionName;
 447   MCSectionCOFF *Result = new (COFFAllocator.Allocate()) MCSectionCOFF(
 448       CachedName, Characteristics, COMDATSymbol, Selection, Kind, Begin);
 449
 450   Iter->second = Result;
 451   return Result;
 452 }
 453
 454 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
 455                                          unsigned Characteristics,
 456                                          SectionKind Kind,
 457                                          const char *BeginSymName) {
 458   return getCOFFSection(Section, Characteristics, Kind, "", 0, GenericSectionID,
 459                         BeginSymName);
 460 }
 461
 462 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section) {
 463   COFFSectionKey T{Section, "", 0, GenericSectionID};
 464   auto Iter = COFFUniquingMap.find(T);
 465   if (Iter == COFFUniquingMap.end())
 466     return nullptr;
 467   return Iter->second;
 468 }
 469
 470 MCSectionCOFF *MCContext::getAssociativeCOFFSection(MCSectionCOFF *Sec,
 471                                                     const MCSymbol *KeySym,
 472                                                     unsigned UniqueID) {
 473   // Return the normal section if we don't have to be associative or unique.
 474   if (!KeySym && UniqueID == GenericSectionID)
 475     return Sec;
 476
 477   // If we have a key symbol, make an associative section with the same name and
 478   // kind as the normal section.
 479   unsigned Characteristics = Sec->getCharacteristics();
 480   if (KeySym) {
 481     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
 482     return getCOFFSection(Sec->getSectionName(), Characteristics,
 483                           Sec->getKind(), KeySym->getName(),
 484                           COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
 485   }
 486
 487   return getCOFFSection(Sec->getSectionName(), Characteristics, Sec->getKind(),
 488                         "", 0, UniqueID);
 489 }
 490
 491 MCSectionWasm *MCContext::getWasmSection(const Twine &Section, SectionKind K,
 492                                          const Twine &Group, unsigned UniqueID,
 493                                          const char *BeginSymName) {
 494   MCSymbolWasm *GroupSym = nullptr;
 495   if (!Group.isTriviallyEmpty() && !Group.str().empty()) {
 496     GroupSym = cast<MCSymbolWasm>(getOrCreateSymbol(Group));
 497     GroupSym->setComdat(true);
 498   }
 499
 500   return getWasmSection(Section, K, GroupSym, UniqueID, BeginSymName);
 501 }
 502
 503 MCSectionWasm *MCContext::getWasmSection(const Twine &Section, SectionKind Kind,
 504                                          const MCSymbolWasm *GroupSym,
 505                                          unsigned UniqueID,
 506                                          const char *BeginSymName) {
 507   StringRef Group = "";
 508   if (GroupSym)
 509     Group = GroupSym->getName();
 510   // Do the lookup, if we have a hit, return it.
 511   auto IterBool = WasmUniquingMap.insert(
 512       std::make_pair(WasmSectionKey{Section.str(), Group, UniqueID}, nullptr));
 513   auto &Entry = *IterBool.first;
 514   if (!IterBool.second)
 515     return Entry.second;
 516
 517   StringRef CachedName = Entry.first.SectionName;
 518
 519   MCSymbol *Begin = createSymbol(CachedName, false, false);
 520   cast<MCSymbolWasm>(Begin)->setType(wasm::WASM_SYMBOL_TYPE_SECTION);
 521
 522   MCSectionWasm *Result = new (WasmAllocator.Allocate())
 523       MCSectionWasm(CachedName, Kind, GroupSym, UniqueID, Begin);
 524   Entry.second = Result;
 525
 526   auto *F = new MCDataFragment();
 527   Result->getFragmentList().insert(Result->begin(), F);
 528   F->setParent(Result);
 529   Begin->setFragment(F);
 530
 531   return Result;
 532 }
 533
 534 MCSubtargetInfo &MCContext::getSubtargetCopy(const MCSubtargetInfo &STI) {
 535   return *new (MCSubtargetAllocator.Allocate()) MCSubtargetInfo(STI);
 536 }
 537
 538 void MCContext::addDebugPrefixMapEntry(const std::string &From,
 539                                        const std::string &To) {
 540   DebugPrefixMap.insert(std::make_pair(From, To));
 541 }
 542
 543 void MCContext::RemapDebugPaths() {
 544   const auto &DebugPrefixMap = this->DebugPrefixMap;
 545   const auto RemapDebugPath = [&DebugPrefixMap](std::string &Path) {
 546     for (const auto &Entry : DebugPrefixMap)
 547       if (StringRef(Path).startswith(Entry.first)) {
 548         std::string RemappedPath =
 549             (Twine(Entry.second) + Path.substr(Entry.first.size())).str();
 550         Path.swap(RemappedPath);
 551       }
 552   };
 553
 554   // Remap compilation directory.
 555   std::string CompDir = CompilationDir.str();
 556   RemapDebugPath(CompDir);
 557   CompilationDir = CompDir;
 558
 559   // Remap MCDwarfDirs in all compilation units.
 560   for (auto &CUIDTablePair : MCDwarfLineTablesCUMap)
 561     for (auto &Dir : CUIDTablePair.second.getMCDwarfDirs())
 562       RemapDebugPath(Dir);
 563 }
 564
 565 //===----------------------------------------------------------------------===//
 566 // Dwarf Management
 567 //===----------------------------------------------------------------------===//
 568
 569 /// getDwarfFile - takes a file name and number to place in the dwarf file and
 570 /// directory tables.  If the file number has already been allocated it is an
 571 /// error and zero is returned and the client reports the error, else the
 572 /// allocated file number is returned.  The file numbers may be in any order.
 573 Expected<unsigned> MCContext::getDwarfFile(StringRef Directory,
 574                                            StringRef FileName,
 575                                            unsigned FileNumber,
 576                                            MD5::MD5Result *Checksum,
 577                                            Optional<StringRef> Source,
 578                                            unsigned CUID) {
 579   MCDwarfLineTable &Table = MCDwarfLineTablesCUMap[CUID];
 580   return Table.tryGetFile(Directory, FileName, Checksum, Source, FileNumber);
 581 }
 582
 583 /// isValidDwarfFileNumber - takes a dwarf file number and returns true if it
 584 /// currently is assigned and false otherwise.
 585 bool MCContext::isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID) {
 586   const MCDwarfLineTable &LineTable = getMCDwarfLineTable(CUID);
 587   if (FileNumber == 0)
 588     return getDwarfVersion() >= 5 && LineTable.hasRootFile();
 589   if (FileNumber >= LineTable.getMCDwarfFiles().size())
 590     return false;
 591
 592   return !LineTable.getMCDwarfFiles()[FileNumber].Name.empty();
 593 }
 594
 595 /// Remove empty sections from SectionsForRanges, to avoid generating
 596 /// useless debug info for them.
 597 void MCContext::finalizeDwarfSections(MCStreamer &MCOS) {
 598   SectionsForRanges.remove_if(
 599       [&](MCSection *Sec) { return !MCOS.mayHaveInstructions(*Sec); });
 600 }
 601
 602 CodeViewContext &MCContext::getCVContext() {
 603   if (!CVContext.get())
 604     CVContext.reset(new CodeViewContext);
 605   return *CVContext.get();
 606 }
 607
 608 //===----------------------------------------------------------------------===//
 609 // Error Reporting
 610 //===----------------------------------------------------------------------===//
 611
 612 void MCContext::reportError(SMLoc Loc, const Twine &Msg) {
 613   HadError = true;
 614
 615   // If we have a source manager use it. Otherwise, try using the inline source
 616   // manager.
 617   // If that fails, use the generic report_fatal_error().
 618   if (SrcMgr)
 619     SrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
 620   else if (InlineSrcMgr)
 621     InlineSrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
 622   else
 623     report_fatal_error(Msg, false);
 624 }
 625
 626 void MCContext::reportFatalError(SMLoc Loc, const Twine &Msg) {
 627   reportError(Loc, Msg);
 628
 629   // If we reached here, we are failing ungracefully. Run the interrupt handlers
 630   // to make sure any special cleanups get done, in particular that we remove
 631   // files registered with RemoveFileOnSignal.
 632   sys::RunInterruptHandlers();
 633   exit(1);
 634 }