lib/MC/MCContext.cpp

   1 //===- lib/MC/MCContext.cpp - Machine Code Context ------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/MC/MCContext.h"
  10 #include "llvm/ADT/Optional.h"
  11 #include "llvm/ADT/SmallString.h"
  12 #include "llvm/ADT/SmallVector.h"
  13 #include "llvm/ADT/StringMap.h"
  14 #include "llvm/ADT/StringRef.h"
  15 #include "llvm/ADT/Twine.h"
  16 #include "llvm/BinaryFormat/COFF.h"
  17 #include "llvm/BinaryFormat/ELF.h"
  18 #include "llvm/MC/MCAsmInfo.h"
  19 #include "llvm/MC/MCCodeView.h"
  20 #include "llvm/MC/MCDwarf.h"
  21 #include "llvm/MC/MCExpr.h"
  22 #include "llvm/MC/MCFragment.h"
  23 #include "llvm/MC/MCLabel.h"
  24 #include "llvm/MC/MCObjectFileInfo.h"
  25 #include "llvm/MC/MCSectionCOFF.h"
  26 #include "llvm/MC/MCSectionELF.h"
  27 #include "llvm/MC/MCSectionMachO.h"
  28 #include "llvm/MC/MCSectionWasm.h"
  29 #include "llvm/MC/MCStreamer.h"
  30 #include "llvm/MC/MCSymbol.h"
  31 #include "llvm/MC/MCSymbolCOFF.h"
  32 #include "llvm/MC/MCSymbolELF.h"
  33 #include "llvm/MC/MCSymbolMachO.h"
  34 #include "llvm/MC/MCSymbolWasm.h"
  35 #include "llvm/MC/SectionKind.h"
  36 #include "llvm/Support/Casting.h"
  37 #include "llvm/Support/CommandLine.h"
  38 #include "llvm/Support/ErrorHandling.h"
  39 #include "llvm/Support/MemoryBuffer.h"
  40 #include "llvm/Support/Signals.h"
  41 #include "llvm/Support/SourceMgr.h"
  42 #include "llvm/Support/raw_ostream.h"
  43 #include <cassert>
  44 #include <cstdlib>
  45 #include <tuple>
  46 #include <utility>
  47
  48 using namespace llvm;
  49
  50 static cl::opt<char*>
  51 AsSecureLogFileName("as-secure-log-file-name",
  52         cl::desc("As secure log file name (initialized from "
  53                  "AS_SECURE_LOG_FILE env variable)"),
  54         cl::init(getenv("AS_SECURE_LOG_FILE")), cl::Hidden);
  55
  56 MCContext::MCContext(const MCAsmInfo *mai, const MCRegisterInfo *mri,
  57                      const MCObjectFileInfo *mofi, const SourceMgr *mgr,
  58                      bool DoAutoReset)
  59     : SrcMgr(mgr), InlineSrcMgr(nullptr), MAI(mai), MRI(mri), MOFI(mofi),
  60       Symbols(Allocator), UsedNames(Allocator),
  61       CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0),
  62       AutoReset(DoAutoReset) {
  63   SecureLogFile = AsSecureLogFileName;
  64
  65   if (SrcMgr && SrcMgr->getNumBuffers())
  66     MainFileName =
  67         SrcMgr->getMemoryBuffer(SrcMgr->getMainFileID())->getBufferIdentifier();
  68 }
  69
  70 MCContext::~MCContext() {
  71   if (AutoReset)
  72     reset();
  73
  74   // NOTE: The symbols are all allocated out of a bump pointer allocator,
  75   // we don't need to free them here.
  76 }
  77
  78 //===----------------------------------------------------------------------===//
  79 // Module Lifetime Management
  80 //===----------------------------------------------------------------------===//
  81
  82 void MCContext::reset() {
  83   // Call the destructors so the fragments are freed
  84   COFFAllocator.DestroyAll();
  85   ELFAllocator.DestroyAll();
  86   MachOAllocator.DestroyAll();
  87
  88   MCSubtargetAllocator.DestroyAll();
  89   UsedNames.clear();
  90   Symbols.clear();
  91   Allocator.Reset();
  92   Instances.clear();
  93   CompilationDir.clear();
  94   MainFileName.clear();
  95   MCDwarfLineTablesCUMap.clear();
  96   SectionsForRanges.clear();
  97   MCGenDwarfLabelEntries.clear();
  98   DwarfDebugFlags = StringRef();
  99   DwarfCompileUnitID = 0;
 100   CurrentDwarfLoc = MCDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0);
 101
 102   CVContext.reset();
 103
 104   MachOUniquingMap.clear();
 105   ELFUniquingMap.clear();
 106   COFFUniquingMap.clear();
 107   WasmUniquingMap.clear();
 108
 109   NextID.clear();
 110   AllowTemporaryLabels = true;
 111   DwarfLocSeen = false;
 112   GenDwarfForAssembly = false;
 113   GenDwarfFileNumber = 0;
 114
 115   HadError = false;
 116 }
 117
 118 //===----------------------------------------------------------------------===//
 119 // Symbol Manipulation
 120 //===----------------------------------------------------------------------===//
 121
 122 MCSymbol *MCContext::getOrCreateSymbol(const Twine &Name) {
 123   SmallString<128> NameSV;
 124   StringRef NameRef = Name.toStringRef(NameSV);
 125
 126   assert(!NameRef.empty() && "Normal symbols cannot be unnamed!");
 127
 128   MCSymbol *&Sym = Symbols[NameRef];
 129   if (!Sym)
 130     Sym = createSymbol(NameRef, false, false);
 131
 132   return Sym;
 133 }
 134
 135 MCSymbol *MCContext::getOrCreateFrameAllocSymbol(StringRef FuncName,
 136                                                  unsigned Idx) {
 137   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
 138                            "$frame_escape_" + Twine(Idx));
 139 }
 140
 141 MCSymbol *MCContext::getOrCreateParentFrameOffsetSymbol(StringRef FuncName) {
 142   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
 143                            "$parent_frame_offset");
 144 }
 145
 146 MCSymbol *MCContext::getOrCreateLSDASymbol(StringRef FuncName) {
 147   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + "__ehtable$" +
 148                            FuncName);
 149 }
 150
 151 MCSymbol *MCContext::createSymbolImpl(const StringMapEntry<bool> *Name,
 152                                       bool IsTemporary) {
 153   if (MOFI) {
 154     switch (MOFI->getObjectFileType()) {
 155     case MCObjectFileInfo::IsCOFF:
 156       return new (Name, *this) MCSymbolCOFF(Name, IsTemporary);
 157     case MCObjectFileInfo::IsELF:
 158       return new (Name, *this) MCSymbolELF(Name, IsTemporary);
 159     case MCObjectFileInfo::IsMachO:
 160       return new (Name, *this) MCSymbolMachO(Name, IsTemporary);
 161     case MCObjectFileInfo::IsWasm:
 162       return new (Name, *this) MCSymbolWasm(Name, IsTemporary);
 163     }
 164   }
 165   return new (Name, *this) MCSymbol(MCSymbol::SymbolKindUnset, Name,
 166                                     IsTemporary);
 167 }
 168
 169 MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
 170                                   bool CanBeUnnamed) {
 171   if (CanBeUnnamed && !UseNamesOnTempLabels)
 172     return createSymbolImpl(nullptr, true);
 173
 174   // Determine whether this is a user written assembler temporary or normal
 175   // label, if used.
 176   bool IsTemporary = CanBeUnnamed;
 177   if (AllowTemporaryLabels && !IsTemporary)
 178     IsTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
 179
 180   SmallString<128> NewName = Name;
 181   bool AddSuffix = AlwaysAddSuffix;
 182   unsigned &NextUniqueID = NextID[Name];
 183   while (true) {
 184     if (AddSuffix) {
 185       NewName.resize(Name.size());
 186       raw_svector_ostream(NewName) << NextUniqueID++;
 187     }
 188     auto NameEntry = UsedNames.insert(std::make_pair(NewName, true));
 189     if (NameEntry.second || !NameEntry.first->second) {
 190       // Ok, we found a name.
 191       // Mark it as used for a non-section symbol.
 192       NameEntry.first->second = true;
 193       // Have the MCSymbol object itself refer to the copy of the string that is
 194       // embedded in the UsedNames entry.
 195       return createSymbolImpl(&*NameEntry.first, IsTemporary);
 196     }
 197     assert(IsTemporary && "Cannot rename non-temporary symbols");
 198     AddSuffix = true;
 199   }
 200   llvm_unreachable("Infinite loop");
 201 }
 202
 203 MCSymbol *MCContext::createTempSymbol(const Twine &Name, bool AlwaysAddSuffix,
 204                                       bool CanBeUnnamed) {
 205   SmallString<128> NameSV;
 206   raw_svector_ostream(NameSV) << MAI->getPrivateGlobalPrefix() << Name;
 207   return createSymbol(NameSV, AlwaysAddSuffix, CanBeUnnamed);
 208 }
 209
 210 MCSymbol *MCContext::createLinkerPrivateTempSymbol() {
 211   SmallString<128> NameSV;
 212   raw_svector_ostream(NameSV) << MAI->getLinkerPrivateGlobalPrefix() << "tmp";
 213   return createSymbol(NameSV, true, false);
 214 }
 215
 216 MCSymbol *MCContext::createTempSymbol(bool CanBeUnnamed) {
 217   return createTempSymbol("tmp", true, CanBeUnnamed);
 218 }
 219
 220 unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
 221   MCLabel *&Label = Instances[LocalLabelVal];
 222   if (!Label)
 223     Label = new (*this) MCLabel(0);
 224   return Label->incInstance();
 225 }
 226
 227 unsigned MCContext::GetInstance(unsigned LocalLabelVal) {
 228   MCLabel *&Label = Instances[LocalLabelVal];
 229   if (!Label)
 230     Label = new (*this) MCLabel(0);
 231   return Label->getInstance();
 232 }
 233
 234 MCSymbol *MCContext::getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
 235                                                        unsigned Instance) {
 236   MCSymbol *&Sym = LocalSymbols[std::make_pair(LocalLabelVal, Instance)];
 237   if (!Sym)
 238     Sym = createTempSymbol(false);
 239   return Sym;
 240 }
 241
 242 MCSymbol *MCContext::createDirectionalLocalSymbol(unsigned LocalLabelVal) {
 243   unsigned Instance = NextInstance(LocalLabelVal);
 244   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
 245 }
 246
 247 MCSymbol *MCContext::getDirectionalLocalSymbol(unsigned LocalLabelVal,
 248                                                bool Before) {
 249   unsigned Instance = GetInstance(LocalLabelVal);
 250   if (!Before)
 251     ++Instance;
 252   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
 253 }
 254
 255 MCSymbol *MCContext::lookupSymbol(const Twine &Name) const {
 256   SmallString<128> NameSV;
 257   StringRef NameRef = Name.toStringRef(NameSV);
 258   return Symbols.lookup(NameRef);
 259 }
 260
 261 void MCContext::setSymbolValue(MCStreamer &Streamer,
 262                               StringRef Sym,
 263                               uint64_t Val) {
 264   auto Symbol = getOrCreateSymbol(Sym);
 265   Streamer.EmitAssignment(Symbol, MCConstantExpr::create(Val, *this));
 266 }
 267
 268 //===----------------------------------------------------------------------===//
 269 // Section Management
 270 //===----------------------------------------------------------------------===//
 271
 272 MCSectionMachO *MCContext::getMachOSection(StringRef Segment, StringRef Section,
 273                                            unsigned TypeAndAttributes,
 274                                            unsigned Reserved2, SectionKind Kind,
 275                                            const char *BeginSymName) {
 276   // We unique sections by their segment/section pair.  The returned section
 277   // may not have the same flags as the requested section, if so this should be
 278   // diagnosed by the client as an error.
 279
 280   // Form the name to look up.
 281   SmallString<64> Name;
 282   Name += Segment;
 283   Name.push_back(',');
 284   Name += Section;
 285
 286   // Do the lookup, if we have a hit, return it.
 287   MCSectionMachO *&Entry = MachOUniquingMap[Name];
 288   if (Entry)
 289     return Entry;
 290
 291   MCSymbol *Begin = nullptr;
 292   if (BeginSymName)
 293     Begin = createTempSymbol(BeginSymName, false);
 294
 295   // Otherwise, return a new section.
 296   return Entry = new (MachOAllocator.Allocate()) MCSectionMachO(
 297              Segment, Section, TypeAndAttributes, Reserved2, Kind, Begin);
 298 }
 299
 300 void MCContext::renameELFSection(MCSectionELF *Section, StringRef Name) {
 301   StringRef GroupName;
 302   if (const MCSymbol *Group = Section->getGroup())
 303     GroupName = Group->getName();
 304
 305   unsigned UniqueID = Section->getUniqueID();
 306   ELFUniquingMap.erase(
 307       ELFSectionKey{Section->getSectionName(), GroupName, UniqueID});
 308   auto I = ELFUniquingMap.insert(std::make_pair(
 309                                      ELFSectionKey{Name, GroupName, UniqueID},
 310                                      Section))
 311                .first;
 312   StringRef CachedName = I->first.SectionName;
 313   const_cast<MCSectionELF *>(Section)->setSectionName(CachedName);
 314 }
 315
 316 MCSectionELF *MCContext::createELFSectionImpl(StringRef Section, unsigned Type,
 317                                               unsigned Flags, SectionKind K,
 318                                               unsigned EntrySize,
 319                                               const MCSymbolELF *Group,
 320                                               unsigned UniqueID,
 321                                               const MCSymbolELF *Associated) {
 322   MCSymbolELF *R;
 323   MCSymbol *&Sym = Symbols[Section];
 324   // A section symbol can not redefine regular symbols. There may be multiple
 325   // sections with the same name, in which case the first such section wins.
 326   if (Sym && Sym->isDefined() &&
 327       (!Sym->isInSection() || Sym->getSection().getBeginSymbol() != Sym))
 328     reportError(SMLoc(), "invalid symbol redefinition");
 329   if (Sym && Sym->isUndefined()) {
 330     R = cast<MCSymbolELF>(Sym);
 331   } else {
 332     auto NameIter = UsedNames.insert(std::make_pair(Section, false)).first;
 333     R = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
 334     if (!Sym)
 335       Sym = R;
 336   }
 337   R->setBinding(ELF::STB_LOCAL);
 338   R->setType(ELF::STT_SECTION);
 339
 340   auto *Ret = new (ELFAllocator.Allocate()) MCSectionELF(
 341       Section, Type, Flags, K, EntrySize, Group, UniqueID, R, Associated);
 342
 343   auto *F = new MCDataFragment();
 344   Ret->getFragmentList().insert(Ret->begin(), F);
 345   F->setParent(Ret);
 346   R->setFragment(F);
 347
 348   return Ret;
 349 }
 350
 351 MCSectionELF *MCContext::createELFRelSection(const Twine &Name, unsigned Type,
 352                                              unsigned Flags, unsigned EntrySize,
 353                                              const MCSymbolELF *Group,
 354                                              const MCSectionELF *RelInfoSection) {
 355   StringMap<bool>::iterator I;
 356   bool Inserted;
 357   std::tie(I, Inserted) =
 358       RelSecNames.insert(std::make_pair(Name.str(), true));
 359
 360   return createELFSectionImpl(
 361       I->getKey(), Type, Flags, SectionKind::getReadOnly(), EntrySize, Group,
 362       true, cast<MCSymbolELF>(RelInfoSection->getBeginSymbol()));
 363 }
 364
 365 MCSectionELF *MCContext::getELFNamedSection(const Twine &Prefix,
 366                                             const Twine &Suffix, unsigned Type,
 367                                             unsigned Flags,
 368                                             unsigned EntrySize) {
 369   return getELFSection(Prefix + "." + Suffix, Type, Flags, EntrySize, Suffix);
 370 }
 371
 372 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
 373                                        unsigned Flags, unsigned EntrySize,
 374                                        const Twine &Group, unsigned UniqueID,
 375                                        const MCSymbolELF *Associated) {
 376   MCSymbolELF *GroupSym = nullptr;
 377   if (!Group.isTriviallyEmpty() && !Group.str().empty())
 378     GroupSym = cast<MCSymbolELF>(getOrCreateSymbol(Group));
 379
 380   return getELFSection(Section, Type, Flags, EntrySize, GroupSym, UniqueID,
 381                        Associated);
 382 }
 383
 384 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
 385                                        unsigned Flags, unsigned EntrySize,
 386                                        const MCSymbolELF *GroupSym,
 387                                        unsigned UniqueID,
 388                                        const MCSymbolELF *Associated) {
 389   StringRef Group = "";
 390   if (GroupSym)
 391     Group = GroupSym->getName();
 392   // Do the lookup, if we have a hit, return it.
 393   auto IterBool = ELFUniquingMap.insert(
 394       std::make_pair(ELFSectionKey{Section.str(), Group, UniqueID}, nullptr));
 395   auto &Entry = *IterBool.first;
 396   if (!IterBool.second)
 397     return Entry.second;
 398
 399   StringRef CachedName = Entry.first.SectionName;
 400
 401   SectionKind Kind;
 402   if (Flags & ELF::SHF_ARM_PURECODE)
 403     Kind = SectionKind::getExecuteOnly();
 404   else if (Flags & ELF::SHF_EXECINSTR)
 405     Kind = SectionKind::getText();
 406   else
 407     Kind = SectionKind::getReadOnly();
 408
 409   MCSectionELF *Result = createELFSectionImpl(
 410       CachedName, Type, Flags, Kind, EntrySize, GroupSym, UniqueID, Associated);
 411   Entry.second = Result;
 412   return Result;
 413 }
 414
 415 MCSectionELF *MCContext::createELFGroupSection(const MCSymbolELF *Group) {
 416   return createELFSectionImpl(".group", ELF::SHT_GROUP, 0,
 417                               SectionKind::getReadOnly(), 4, Group, ~0,
 418                               nullptr);
 419 }
 420
 421 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
 422                                          unsigned Characteristics,
 423                                          SectionKind Kind,
 424                                          StringRef COMDATSymName, int Selection,
 425                                          unsigned UniqueID,
 426                                          const char *BeginSymName) {
 427   MCSymbol *COMDATSymbol = nullptr;
 428   if (!COMDATSymName.empty()) {
 429     COMDATSymbol = getOrCreateSymbol(COMDATSymName);
 430     COMDATSymName = COMDATSymbol->getName();
 431   }
 432
 433
 434   // Do the lookup, if we have a hit, return it.
 435   COFFSectionKey T{Section, COMDATSymName, Selection, UniqueID};
 436   auto IterBool = COFFUniquingMap.insert(std::make_pair(T, nullptr));
 437   auto Iter = IterBool.first;
 438   if (!IterBool.second)
 439     return Iter->second;
 440
 441   MCSymbol *Begin = nullptr;
 442   if (BeginSymName)
 443     Begin = createTempSymbol(BeginSymName, false);
 444
 445   StringRef CachedName = Iter->first.SectionName;
 446   MCSectionCOFF *Result = new (COFFAllocator.Allocate()) MCSectionCOFF(
 447       CachedName, Characteristics, COMDATSymbol, Selection, Kind, Begin);
 448
 449   Iter->second = Result;
 450   return Result;
 451 }
 452
 453 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
 454                                          unsigned Characteristics,
 455                                          SectionKind Kind,
 456                                          const char *BeginSymName) {
 457   return getCOFFSection(Section, Characteristics, Kind, "", 0, GenericSectionID,
 458                         BeginSymName);
 459 }
 460
 461 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section) {
 462   COFFSectionKey T{Section, "", 0, GenericSectionID};
 463   auto Iter = COFFUniquingMap.find(T);
 464   if (Iter == COFFUniquingMap.end())
 465     return nullptr;
 466   return Iter->second;
 467 }
 468
 469 MCSectionCOFF *MCContext::getAssociativeCOFFSection(MCSectionCOFF *Sec,
 470                                                     const MCSymbol *KeySym,
 471                                                     unsigned UniqueID) {
 472   // Return the normal section if we don't have to be associative or unique.
 473   if (!KeySym && UniqueID == GenericSectionID)
 474     return Sec;
 475
 476   // If we have a key symbol, make an associative section with the same name and
 477   // kind as the normal section.
 478   unsigned Characteristics = Sec->getCharacteristics();
 479   if (KeySym) {
 480     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
 481     return getCOFFSection(Sec->getSectionName(), Characteristics,
 482                           Sec->getKind(), KeySym->getName(),
 483                           COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
 484   }
 485
 486   return getCOFFSection(Sec->getSectionName(), Characteristics, Sec->getKind(),
 487                         "", 0, UniqueID);
 488 }
 489
 490 MCSectionWasm *MCContext::getWasmSection(const Twine &Section, SectionKind K,
 491                                          const Twine &Group, unsigned UniqueID,
 492                                          const char *BeginSymName) {
 493   MCSymbolWasm *GroupSym = nullptr;
 494   if (!Group.isTriviallyEmpty() && !Group.str().empty()) {
 495     GroupSym = cast<MCSymbolWasm>(getOrCreateSymbol(Group));
 496     GroupSym->setComdat(true);
 497   }
 498
 499   return getWasmSection(Section, K, GroupSym, UniqueID, BeginSymName);
 500 }
 501
 502 MCSectionWasm *MCContext::getWasmSection(const Twine &Section, SectionKind Kind,
 503                                          const MCSymbolWasm *GroupSym,
 504                                          unsigned UniqueID,
 505                                          const char *BeginSymName) {
 506   StringRef Group = "";
 507   if (GroupSym)
 508     Group = GroupSym->getName();
 509   // Do the lookup, if we have a hit, return it.
 510   auto IterBool = WasmUniquingMap.insert(
 511       std::make_pair(WasmSectionKey{Section.str(), Group, UniqueID}, nullptr));
 512   auto &Entry = *IterBool.first;
 513   if (!IterBool.second)
 514     return Entry.second;
 515
 516   StringRef CachedName = Entry.first.SectionName;
 517
 518   MCSymbol *Begin = createSymbol(CachedName, false, false);
 519   cast<MCSymbolWasm>(Begin)->setType(wasm::WASM_SYMBOL_TYPE_SECTION);
 520
 521   MCSectionWasm *Result = new (WasmAllocator.Allocate())
 522       MCSectionWasm(CachedName, Kind, GroupSym, UniqueID, Begin);
 523   Entry.second = Result;
 524
 525   auto *F = new MCDataFragment();
 526   Result->getFragmentList().insert(Result->begin(), F);
 527   F->setParent(Result);
 528   Begin->setFragment(F);
 529
 530   return Result;
 531 }
 532
 533 MCSubtargetInfo &MCContext::getSubtargetCopy(const MCSubtargetInfo &STI) {
 534   return *new (MCSubtargetAllocator.Allocate()) MCSubtargetInfo(STI);
 535 }
 536
 537 void MCContext::addDebugPrefixMapEntry(const std::string &From,
 538                                        const std::string &To) {
 539   DebugPrefixMap.insert(std::make_pair(From, To));
 540 }
 541
 542 void MCContext::RemapDebugPaths() {
 543   const auto &DebugPrefixMap = this->DebugPrefixMap;
 544   const auto RemapDebugPath = [&DebugPrefixMap](std::string &Path) {
 545     for (const auto &Entry : DebugPrefixMap)
 546       if (StringRef(Path).startswith(Entry.first)) {
 547         std::string RemappedPath =
 548             (Twine(Entry.second) + Path.substr(Entry.first.size())).str();
 549         Path.swap(RemappedPath);
 550       }
 551   };
 552
 553   // Remap compilation directory.
 554   std::string CompDir = CompilationDir.str();
 555   RemapDebugPath(CompDir);
 556   CompilationDir = CompDir;
 557
 558   // Remap MCDwarfDirs in all compilation units.
 559   for (auto &CUIDTablePair : MCDwarfLineTablesCUMap)
 560     for (auto &Dir : CUIDTablePair.second.getMCDwarfDirs())
 561       RemapDebugPath(Dir);
 562 }
 563
 564 //===----------------------------------------------------------------------===//
 565 // Dwarf Management
 566 //===----------------------------------------------------------------------===//
 567
 568 /// getDwarfFile - takes a file name and number to place in the dwarf file and
 569 /// directory tables.  If the file number has already been allocated it is an
 570 /// error and zero is returned and the client reports the error, else the
 571 /// allocated file number is returned.  The file numbers may be in any order.
 572 Expected<unsigned> MCContext::getDwarfFile(StringRef Directory,
 573                                            StringRef FileName,
 574                                            unsigned FileNumber,
 575                                            MD5::MD5Result *Checksum,
 576                                            Optional<StringRef> Source,
 577                                            unsigned CUID) {
 578   MCDwarfLineTable &Table = MCDwarfLineTablesCUMap[CUID];
 579   return Table.tryGetFile(Directory, FileName, Checksum, Source, FileNumber);
 580 }
 581
 582 /// isValidDwarfFileNumber - takes a dwarf file number and returns true if it
 583 /// currently is assigned and false otherwise.
 584 bool MCContext::isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID) {
 585   const MCDwarfLineTable &LineTable = getMCDwarfLineTable(CUID);
 586   if (FileNumber == 0)
 587     return getDwarfVersion() >= 5 && LineTable.hasRootFile();
 588   if (FileNumber >= LineTable.getMCDwarfFiles().size())
 589     return false;
 590
 591   return !LineTable.getMCDwarfFiles()[FileNumber].Name.empty();
 592 }
 593
 594 /// Remove empty sections from SectionsForRanges, to avoid generating
 595 /// useless debug info for them.
 596 void MCContext::finalizeDwarfSections(MCStreamer &MCOS) {
 597   SectionsForRanges.remove_if(
 598       [&](MCSection *Sec) { return !MCOS.mayHaveInstructions(*Sec); });
 599 }
 600
 601 CodeViewContext &MCContext::getCVContext() {
 602   if (!CVContext.get())
 603     CVContext.reset(new CodeViewContext);
 604   return *CVContext.get();
 605 }
 606
 607 //===----------------------------------------------------------------------===//
 608 // Error Reporting
 609 //===----------------------------------------------------------------------===//
 610
 611 void MCContext::reportError(SMLoc Loc, const Twine &Msg) {
 612   HadError = true;
 613
 614   // If we have a source manager use it. Otherwise, try using the inline source
 615   // manager.
 616   // If that fails, use the generic report_fatal_error().
 617   if (SrcMgr)
 618     SrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
 619   else if (InlineSrcMgr)
 620     InlineSrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
 621   else
 622     report_fatal_error(Msg, false);
 623 }
 624
 625 void MCContext::reportFatalError(SMLoc Loc, const Twine &Msg) {
 626   reportError(Loc, Msg);
 627
 628   // If we reached here, we are failing ungracefully. Run the interrupt handlers
 629   // to make sure any special cleanups get done, in particular that we remove
 630   // files registered with RemoveFileOnSignal.
 631   sys::RunInterruptHandlers();
 632   exit(1);
 633 }