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/MCSectionXCOFF.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/MCSymbolXCOFF.h"
  37 #include "llvm/MC/SectionKind.h"
  38 #include "llvm/Support/Casting.h"
  39 #include "llvm/Support/CommandLine.h"
  40 #include "llvm/Support/ErrorHandling.h"
  41 #include "llvm/Support/MemoryBuffer.h"
  42 #include "llvm/Support/Path.h"
  43 #include "llvm/Support/Signals.h"
  44 #include "llvm/Support/SourceMgr.h"
  45 #include "llvm/Support/raw_ostream.h"
  46 #include <cassert>
  47 #include <cstdlib>
  48 #include <tuple>
  49 #include <utility>
  50
  51 using namespace llvm;
  52
  53 static cl::opt<char*>
  54 AsSecureLogFileName("as-secure-log-file-name",
  55         cl::desc("As secure log file name (initialized from "
  56                  "AS_SECURE_LOG_FILE env variable)"),
  57         cl::init(getenv("AS_SECURE_LOG_FILE")), cl::Hidden);
  58
  59 MCContext::MCContext(const MCAsmInfo *mai, const MCRegisterInfo *mri,
  60                      const MCObjectFileInfo *mofi, const SourceMgr *mgr,
  61                      bool DoAutoReset)
  62     : SrcMgr(mgr), InlineSrcMgr(nullptr), MAI(mai), MRI(mri), MOFI(mofi),
  63       Symbols(Allocator), UsedNames(Allocator),
  64       CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0),
  65       AutoReset(DoAutoReset) {
  66   SecureLogFile = AsSecureLogFileName;
  67
  68   if (SrcMgr && SrcMgr->getNumBuffers())
  69     MainFileName =
  70         SrcMgr->getMemoryBuffer(SrcMgr->getMainFileID())->getBufferIdentifier();
  71 }
  72
  73 MCContext::~MCContext() {
  74   if (AutoReset)
  75     reset();
  76
  77   // NOTE: The symbols are all allocated out of a bump pointer allocator,
  78   // we don't need to free them here.
  79 }
  80
  81 //===----------------------------------------------------------------------===//
  82 // Module Lifetime Management
  83 //===----------------------------------------------------------------------===//
  84
  85 void MCContext::reset() {
  86   // Call the destructors so the fragments are freed
  87   COFFAllocator.DestroyAll();
  88   ELFAllocator.DestroyAll();
  89   MachOAllocator.DestroyAll();
  90   XCOFFAllocator.DestroyAll();
  91
  92   MCSubtargetAllocator.DestroyAll();
  93   UsedNames.clear();
  94   Symbols.clear();
  95   Allocator.Reset();
  96   Instances.clear();
  97   CompilationDir.clear();
  98   MainFileName.clear();
  99   MCDwarfLineTablesCUMap.clear();
 100   SectionsForRanges.clear();
 101   MCGenDwarfLabelEntries.clear();
 102   DwarfDebugFlags = StringRef();
 103   DwarfCompileUnitID = 0;
 104   CurrentDwarfLoc = MCDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0);
 105
 106   CVContext.reset();
 107
 108   MachOUniquingMap.clear();
 109   ELFUniquingMap.clear();
 110   COFFUniquingMap.clear();
 111   WasmUniquingMap.clear();
 112   XCOFFUniquingMap.clear();
 113
 114   NextID.clear();
 115   AllowTemporaryLabels = true;
 116   DwarfLocSeen = false;
 117   GenDwarfForAssembly = false;
 118   GenDwarfFileNumber = 0;
 119
 120   HadError = false;
 121 }
 122
 123 //===----------------------------------------------------------------------===//
 124 // Symbol Manipulation
 125 //===----------------------------------------------------------------------===//
 126
 127 MCSymbol *MCContext::getOrCreateSymbol(const Twine &Name) {
 128   SmallString<128> NameSV;
 129   StringRef NameRef = Name.toStringRef(NameSV);
 130
 131   assert(!NameRef.empty() && "Normal symbols cannot be unnamed!");
 132
 133   MCSymbol *&Sym = Symbols[NameRef];
 134   if (!Sym)
 135     Sym = createSymbol(NameRef, false, false);
 136
 137   return Sym;
 138 }
 139
 140 MCSymbol *MCContext::getOrCreateFrameAllocSymbol(StringRef FuncName,
 141                                                  unsigned Idx) {
 142   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
 143                            "$frame_escape_" + Twine(Idx));
 144 }
 145
 146 MCSymbol *MCContext::getOrCreateParentFrameOffsetSymbol(StringRef FuncName) {
 147   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
 148                            "$parent_frame_offset");
 149 }
 150
 151 MCSymbol *MCContext::getOrCreateLSDASymbol(StringRef FuncName) {
 152   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + "__ehtable$" +
 153                            FuncName);
 154 }
 155
 156 MCSymbol *MCContext::createSymbolImpl(const StringMapEntry<bool> *Name,
 157                                       bool IsTemporary) {
 158   if (MOFI) {
 159     switch (MOFI->getObjectFileType()) {
 160     case MCObjectFileInfo::IsCOFF:
 161       return new (Name, *this) MCSymbolCOFF(Name, IsTemporary);
 162     case MCObjectFileInfo::IsELF:
 163       return new (Name, *this) MCSymbolELF(Name, IsTemporary);
 164     case MCObjectFileInfo::IsMachO:
 165       return new (Name, *this) MCSymbolMachO(Name, IsTemporary);
 166     case MCObjectFileInfo::IsWasm:
 167       return new (Name, *this) MCSymbolWasm(Name, IsTemporary);
 168     case MCObjectFileInfo::IsXCOFF:
 169       return new (Name, *this) MCSymbolXCOFF(Name, IsTemporary);
 170     }
 171   }
 172   return new (Name, *this) MCSymbol(MCSymbol::SymbolKindUnset, Name,
 173                                     IsTemporary);
 174 }
 175
 176 MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
 177                                   bool CanBeUnnamed) {
 178   if (CanBeUnnamed && !UseNamesOnTempLabels)
 179     return createSymbolImpl(nullptr, true);
 180
 181   // Determine whether this is a user written assembler temporary or normal
 182   // label, if used.
 183   bool IsTemporary = CanBeUnnamed;
 184   if (AllowTemporaryLabels && !IsTemporary)
 185     IsTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
 186
 187   SmallString<128> NewName = Name;
 188   bool AddSuffix = AlwaysAddSuffix;
 189   unsigned &NextUniqueID = NextID[Name];
 190   while (true) {
 191     if (AddSuffix) {
 192       NewName.resize(Name.size());
 193       raw_svector_ostream(NewName) << NextUniqueID++;
 194     }
 195     auto NameEntry = UsedNames.insert(std::make_pair(NewName, true));
 196     if (NameEntry.second || !NameEntry.first->second) {
 197       // Ok, we found a name.
 198       // Mark it as used for a non-section symbol.
 199       NameEntry.first->second = true;
 200       // Have the MCSymbol object itself refer to the copy of the string that is
 201       // embedded in the UsedNames entry.
 202       return createSymbolImpl(&*NameEntry.first, IsTemporary);
 203     }
 204     assert(IsTemporary && "Cannot rename non-temporary symbols");
 205     AddSuffix = true;
 206   }
 207   llvm_unreachable("Infinite loop");
 208 }
 209
 210 MCSymbol *MCContext::createTempSymbol(const Twine &Name, bool AlwaysAddSuffix,
 211                                       bool CanBeUnnamed) {
 212   SmallString<128> NameSV;
 213   raw_svector_ostream(NameSV) << MAI->getPrivateGlobalPrefix() << Name;
 214   return createSymbol(NameSV, AlwaysAddSuffix, CanBeUnnamed);
 215 }
 216
 217 MCSymbol *MCContext::createLinkerPrivateTempSymbol() {
 218   SmallString<128> NameSV;
 219   raw_svector_ostream(NameSV) << MAI->getLinkerPrivateGlobalPrefix() << "tmp";
 220   return createSymbol(NameSV, true, false);
 221 }
 222
 223 MCSymbol *MCContext::createTempSymbol(bool CanBeUnnamed) {
 224   return createTempSymbol("tmp", true, CanBeUnnamed);
 225 }
 226
 227 unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
 228   MCLabel *&Label = Instances[LocalLabelVal];
 229   if (!Label)
 230     Label = new (*this) MCLabel(0);
 231   return Label->incInstance();
 232 }
 233
 234 unsigned MCContext::GetInstance(unsigned LocalLabelVal) {
 235   MCLabel *&Label = Instances[LocalLabelVal];
 236   if (!Label)
 237     Label = new (*this) MCLabel(0);
 238   return Label->getInstance();
 239 }
 240
 241 MCSymbol *MCContext::getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
 242                                                        unsigned Instance) {
 243   MCSymbol *&Sym = LocalSymbols[std::make_pair(LocalLabelVal, Instance)];
 244   if (!Sym)
 245     Sym = createTempSymbol(false);
 246   return Sym;
 247 }
 248
 249 MCSymbol *MCContext::createDirectionalLocalSymbol(unsigned LocalLabelVal) {
 250   unsigned Instance = NextInstance(LocalLabelVal);
 251   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
 252 }
 253
 254 MCSymbol *MCContext::getDirectionalLocalSymbol(unsigned LocalLabelVal,
 255                                                bool Before) {
 256   unsigned Instance = GetInstance(LocalLabelVal);
 257   if (!Before)
 258     ++Instance;
 259   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
 260 }
 261
 262 MCSymbol *MCContext::lookupSymbol(const Twine &Name) const {
 263   SmallString<128> NameSV;
 264   StringRef NameRef = Name.toStringRef(NameSV);
 265   return Symbols.lookup(NameRef);
 266 }
 267
 268 void MCContext::setSymbolValue(MCStreamer &Streamer,
 269                               StringRef Sym,
 270                               uint64_t Val) {
 271   auto Symbol = getOrCreateSymbol(Sym);
 272   Streamer.EmitAssignment(Symbol, MCConstantExpr::create(Val, *this));
 273 }
 274
 275 //===----------------------------------------------------------------------===//
 276 // Section Management
 277 //===----------------------------------------------------------------------===//
 278
 279 MCSectionMachO *MCContext::getMachOSection(StringRef Segment, StringRef Section,
 280                                            unsigned TypeAndAttributes,
 281                                            unsigned Reserved2, SectionKind Kind,
 282                                            const char *BeginSymName) {
 283   // We unique sections by their segment/section pair.  The returned section
 284   // may not have the same flags as the requested section, if so this should be
 285   // diagnosed by the client as an error.
 286
 287   // Form the name to look up.
 288   SmallString<64> Name;
 289   Name += Segment;
 290   Name.push_back(',');
 291   Name += Section;
 292
 293   // Do the lookup, if we have a hit, return it.
 294   MCSectionMachO *&Entry = MachOUniquingMap[Name];
 295   if (Entry)
 296     return Entry;
 297
 298   MCSymbol *Begin = nullptr;
 299   if (BeginSymName)
 300     Begin = createTempSymbol(BeginSymName, false);
 301
 302   // Otherwise, return a new section.
 303   return Entry = new (MachOAllocator.Allocate()) MCSectionMachO(
 304              Segment, Section, TypeAndAttributes, Reserved2, Kind, Begin);
 305 }
 306
 307 void MCContext::renameELFSection(MCSectionELF *Section, StringRef Name) {
 308   StringRef GroupName;
 309   if (const MCSymbol *Group = Section->getGroup())
 310     GroupName = Group->getName();
 311
 312   unsigned UniqueID = Section->getUniqueID();
 313   ELFUniquingMap.erase(
 314       ELFSectionKey{Section->getSectionName(), GroupName, UniqueID});
 315   auto I = ELFUniquingMap.insert(std::make_pair(
 316                                      ELFSectionKey{Name, GroupName, UniqueID},
 317                                      Section))
 318                .first;
 319   StringRef CachedName = I->first.SectionName;
 320   const_cast<MCSectionELF *>(Section)->setSectionName(CachedName);
 321 }
 322
 323 MCSectionELF *MCContext::createELFSectionImpl(StringRef Section, unsigned Type,
 324                                               unsigned Flags, SectionKind K,
 325                                               unsigned EntrySize,
 326                                               const MCSymbolELF *Group,
 327                                               unsigned UniqueID,
 328                                               const MCSymbolELF *Associated) {
 329   MCSymbolELF *R;
 330   MCSymbol *&Sym = Symbols[Section];
 331   // A section symbol can not redefine regular symbols. There may be multiple
 332   // sections with the same name, in which case the first such section wins.
 333   if (Sym && Sym->isDefined() &&
 334       (!Sym->isInSection() || Sym->getSection().getBeginSymbol() != Sym))
 335     reportError(SMLoc(), "invalid symbol redefinition");
 336   if (Sym && Sym->isUndefined()) {
 337     R = cast<MCSymbolELF>(Sym);
 338   } else {
 339     auto NameIter = UsedNames.insert(std::make_pair(Section, false)).first;
 340     R = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
 341     if (!Sym)
 342       Sym = R;
 343   }
 344   R->setBinding(ELF::STB_LOCAL);
 345   R->setType(ELF::STT_SECTION);
 346
 347   auto *Ret = new (ELFAllocator.Allocate()) MCSectionELF(
 348       Section, Type, Flags, K, EntrySize, Group, UniqueID, R, Associated);
 349
 350   auto *F = new MCDataFragment();
 351   Ret->getFragmentList().insert(Ret->begin(), F);
 352   F->setParent(Ret);
 353   R->setFragment(F);
 354
 355   return Ret;
 356 }
 357
 358 MCSectionELF *MCContext::createELFRelSection(const Twine &Name, unsigned Type,
 359                                              unsigned Flags, unsigned EntrySize,
 360                                              const MCSymbolELF *Group,
 361                                              const MCSectionELF *RelInfoSection) {
 362   StringMap<bool>::iterator I;
 363   bool Inserted;
 364   std::tie(I, Inserted) =
 365       RelSecNames.insert(std::make_pair(Name.str(), true));
 366
 367   return createELFSectionImpl(
 368       I->getKey(), Type, Flags, SectionKind::getReadOnly(), EntrySize, Group,
 369       true, cast<MCSymbolELF>(RelInfoSection->getBeginSymbol()));
 370 }
 371
 372 MCSectionELF *MCContext::getELFNamedSection(const Twine &Prefix,
 373                                             const Twine &Suffix, unsigned Type,
 374                                             unsigned Flags,
 375                                             unsigned EntrySize) {
 376   return getELFSection(Prefix + "." + Suffix, Type, Flags, EntrySize, Suffix);
 377 }
 378
 379 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
 380                                        unsigned Flags, unsigned EntrySize,
 381                                        const Twine &Group, unsigned UniqueID,
 382                                        const MCSymbolELF *Associated) {
 383   MCSymbolELF *GroupSym = nullptr;
 384   if (!Group.isTriviallyEmpty() && !Group.str().empty())
 385     GroupSym = cast<MCSymbolELF>(getOrCreateSymbol(Group));
 386
 387   return getELFSection(Section, Type, Flags, EntrySize, GroupSym, UniqueID,
 388                        Associated);
 389 }
 390
 391 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
 392                                        unsigned Flags, unsigned EntrySize,
 393                                        const MCSymbolELF *GroupSym,
 394                                        unsigned UniqueID,
 395                                        const MCSymbolELF *Associated) {
 396   StringRef Group = "";
 397   if (GroupSym)
 398     Group = GroupSym->getName();
 399   // Do the lookup, if we have a hit, return it.
 400   auto IterBool = ELFUniquingMap.insert(
 401       std::make_pair(ELFSectionKey{Section.str(), Group, UniqueID}, nullptr));
 402   auto &Entry = *IterBool.first;
 403   if (!IterBool.second)
 404     return Entry.second;
 405
 406   StringRef CachedName = Entry.first.SectionName;
 407
 408   SectionKind Kind;
 409   if (Flags & ELF::SHF_ARM_PURECODE)
 410     Kind = SectionKind::getExecuteOnly();
 411   else if (Flags & ELF::SHF_EXECINSTR)
 412     Kind = SectionKind::getText();
 413   else
 414     Kind = SectionKind::getReadOnly();
 415
 416   MCSectionELF *Result = createELFSectionImpl(
 417       CachedName, Type, Flags, Kind, EntrySize, GroupSym, UniqueID, Associated);
 418   Entry.second = Result;
 419   return Result;
 420 }
 421
 422 MCSectionELF *MCContext::createELFGroupSection(const MCSymbolELF *Group) {
 423   return createELFSectionImpl(".group", ELF::SHT_GROUP, 0,
 424                               SectionKind::getReadOnly(), 4, Group, ~0,
 425                               nullptr);
 426 }
 427
 428 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
 429                                          unsigned Characteristics,
 430                                          SectionKind Kind,
 431                                          StringRef COMDATSymName, int Selection,
 432                                          unsigned UniqueID,
 433                                          const char *BeginSymName) {
 434   MCSymbol *COMDATSymbol = nullptr;
 435   if (!COMDATSymName.empty()) {
 436     COMDATSymbol = getOrCreateSymbol(COMDATSymName);
 437     COMDATSymName = COMDATSymbol->getName();
 438   }
 439
 440
 441   // Do the lookup, if we have a hit, return it.
 442   COFFSectionKey T{Section, COMDATSymName, Selection, UniqueID};
 443   auto IterBool = COFFUniquingMap.insert(std::make_pair(T, nullptr));
 444   auto Iter = IterBool.first;
 445   if (!IterBool.second)
 446     return Iter->second;
 447
 448   MCSymbol *Begin = nullptr;
 449   if (BeginSymName)
 450     Begin = createTempSymbol(BeginSymName, false);
 451
 452   StringRef CachedName = Iter->first.SectionName;
 453   MCSectionCOFF *Result = new (COFFAllocator.Allocate()) MCSectionCOFF(
 454       CachedName, Characteristics, COMDATSymbol, Selection, Kind, Begin);
 455
 456   Iter->second = Result;
 457   return Result;
 458 }
 459
 460 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
 461                                          unsigned Characteristics,
 462                                          SectionKind Kind,
 463                                          const char *BeginSymName) {
 464   return getCOFFSection(Section, Characteristics, Kind, "", 0, GenericSectionID,
 465                         BeginSymName);
 466 }
 467
 468 MCSectionCOFF *MCContext::getAssociativeCOFFSection(MCSectionCOFF *Sec,
 469                                                     const MCSymbol *KeySym,
 470                                                     unsigned UniqueID) {
 471   // Return the normal section if we don't have to be associative or unique.
 472   if (!KeySym && UniqueID == GenericSectionID)
 473     return Sec;
 474
 475   // If we have a key symbol, make an associative section with the same name and
 476   // kind as the normal section.
 477   unsigned Characteristics = Sec->getCharacteristics();
 478   if (KeySym) {
 479     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
 480     return getCOFFSection(Sec->getSectionName(), Characteristics,
 481                           Sec->getKind(), KeySym->getName(),
 482                           COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
 483   }
 484
 485   return getCOFFSection(Sec->getSectionName(), Characteristics, Sec->getKind(),
 486                         "", 0, UniqueID);
 487 }
 488
 489 MCSectionWasm *MCContext::getWasmSection(const Twine &Section, SectionKind K,
 490                                          const Twine &Group, unsigned UniqueID,
 491                                          const char *BeginSymName) {
 492   MCSymbolWasm *GroupSym = nullptr;
 493   if (!Group.isTriviallyEmpty() && !Group.str().empty()) {
 494     GroupSym = cast<MCSymbolWasm>(getOrCreateSymbol(Group));
 495     GroupSym->setComdat(true);
 496   }
 497
 498   return getWasmSection(Section, K, GroupSym, UniqueID, BeginSymName);
 499 }
 500
 501 MCSectionWasm *MCContext::getWasmSection(const Twine &Section, SectionKind Kind,
 502                                          const MCSymbolWasm *GroupSym,
 503                                          unsigned UniqueID,
 504                                          const char *BeginSymName) {
 505   StringRef Group = "";
 506   if (GroupSym)
 507     Group = GroupSym->getName();
 508   // Do the lookup, if we have a hit, return it.
 509   auto IterBool = WasmUniquingMap.insert(
 510       std::make_pair(WasmSectionKey{Section.str(), Group, UniqueID}, nullptr));
 511   auto &Entry = *IterBool.first;
 512   if (!IterBool.second)
 513     return Entry.second;
 514
 515   StringRef CachedName = Entry.first.SectionName;
 516
 517   MCSymbol *Begin = createSymbol(CachedName, false, false);
 518   cast<MCSymbolWasm>(Begin)->setType(wasm::WASM_SYMBOL_TYPE_SECTION);
 519
 520   MCSectionWasm *Result = new (WasmAllocator.Allocate())
 521       MCSectionWasm(CachedName, Kind, GroupSym, UniqueID, Begin);
 522   Entry.second = Result;
 523
 524   auto *F = new MCDataFragment();
 525   Result->getFragmentList().insert(Result->begin(), F);
 526   F->setParent(Result);
 527   Begin->setFragment(F);
 528
 529   return Result;
 530 }
 531
 532 MCSectionXCOFF *MCContext::getXCOFFSection(StringRef Section,
 533                                            XCOFF::StorageMappingClass SMC,
 534                                            SectionKind Kind,
 535                                            const char *BeginSymName) {
 536   // Do the lookup. If we have a hit, return it.
 537   auto IterBool = XCOFFUniquingMap.insert(
 538       std::make_pair(XCOFFSectionKey{Section.str(), SMC}, nullptr));
 539   auto &Entry = *IterBool.first;
 540   if (!IterBool.second)
 541     return Entry.second;
 542
 543   // Otherwise, return a new section.
 544   StringRef CachedName = Entry.first.SectionName;
 545
 546   MCSymbol *Begin = nullptr;
 547   if (BeginSymName)
 548     Begin = createTempSymbol(BeginSymName, false);
 549
 550   MCSectionXCOFF *Result = new (XCOFFAllocator.Allocate())
 551       MCSectionXCOFF(CachedName, SMC, Kind, Begin);
 552   Entry.second = Result;
 553
 554   auto *F = new MCDataFragment();
 555   Result->getFragmentList().insert(Result->begin(), F);
 556   F->setParent(Result);
 557
 558   if (Begin)
 559     Begin->setFragment(F);
 560
 561   return Result;
 562 }
 563
 564 MCSubtargetInfo &MCContext::getSubtargetCopy(const MCSubtargetInfo &STI) {
 565   return *new (MCSubtargetAllocator.Allocate()) MCSubtargetInfo(STI);
 566 }
 567
 568 void MCContext::addDebugPrefixMapEntry(const std::string &From,
 569                                        const std::string &To) {
 570   DebugPrefixMap.insert(std::make_pair(From, To));
 571 }
 572
 573 void MCContext::RemapDebugPaths() {
 574   const auto &DebugPrefixMap = this->DebugPrefixMap;
 575   const auto RemapDebugPath = [&DebugPrefixMap](std::string &Path) {
 576     for (const auto &Entry : DebugPrefixMap)
 577       if (StringRef(Path).startswith(Entry.first)) {
 578         std::string RemappedPath =
 579             (Twine(Entry.second) + Path.substr(Entry.first.size())).str();
 580         Path.swap(RemappedPath);
 581       }
 582   };
 583
 584   // Remap compilation directory.
 585   std::string CompDir = CompilationDir.str();
 586   RemapDebugPath(CompDir);
 587   CompilationDir = CompDir;
 588
 589   // Remap MCDwarfDirs in all compilation units.
 590   for (auto &CUIDTablePair : MCDwarfLineTablesCUMap)
 591     for (auto &Dir : CUIDTablePair.second.getMCDwarfDirs())
 592       RemapDebugPath(Dir);
 593 }
 594
 595 //===----------------------------------------------------------------------===//
 596 // Dwarf Management
 597 //===----------------------------------------------------------------------===//
 598
 599 void MCContext::setGenDwarfRootFile(StringRef InputFileName, StringRef Buffer) {
 600   // MCDwarf needs the root file as well as the compilation directory.
 601   // If we find a '.file 0' directive that will supersede these values.
 602   Optional<MD5::MD5Result> Cksum;
 603   if (getDwarfVersion() >= 5) {
 604     MD5 Hash;
 605     MD5::MD5Result Sum;
 606     Hash.update(Buffer);
 607     Hash.final(Sum);
 608     Cksum = Sum;
 609   }
 610   // Canonicalize the root filename. It cannot be empty, and should not
 611   // repeat the compilation dir.
 612   // The MCContext ctor initializes MainFileName to the name associated with
 613   // the SrcMgr's main file ID, which might be the same as InputFileName (and
 614   // possibly include directory components).
 615   // Or, MainFileName might have been overridden by a -main-file-name option,
 616   // which is supposed to be just a base filename with no directory component.
 617   // So, if the InputFileName and MainFileName are not equal, assume
 618   // MainFileName is a substitute basename and replace the last component.
 619   SmallString<1024> FileNameBuf = InputFileName;
 620   if (FileNameBuf.empty() || FileNameBuf == "-")
 621     FileNameBuf = "<stdin>";
 622   if (!getMainFileName().empty() && FileNameBuf != getMainFileName()) {
 623     llvm::sys::path::remove_filename(FileNameBuf);
 624     llvm::sys::path::append(FileNameBuf, getMainFileName());
 625   }
 626   StringRef FileName = FileNameBuf;
 627   if (FileName.consume_front(getCompilationDir()))
 628     if (llvm::sys::path::is_separator(FileName.front()))
 629       FileName = FileName.drop_front();
 630   assert(!FileName.empty());
 631   setMCLineTableRootFile(
 632       /*CUID=*/0, getCompilationDir(), FileName, Cksum, None);
 633 }
 634
 635 /// getDwarfFile - takes a file name and number to place in the dwarf file and
 636 /// directory tables.  If the file number has already been allocated it is an
 637 /// error and zero is returned and the client reports the error, else the
 638 /// allocated file number is returned.  The file numbers may be in any order.
 639 Expected<unsigned> MCContext::getDwarfFile(StringRef Directory,
 640                                            StringRef FileName,
 641                                            unsigned FileNumber,
 642                                            Optional<MD5::MD5Result> Checksum,
 643                                            Optional<StringRef> Source,
 644                                            unsigned CUID) {
 645   MCDwarfLineTable &Table = MCDwarfLineTablesCUMap[CUID];
 646   return Table.tryGetFile(Directory, FileName, Checksum, Source, DwarfVersion,
 647                           FileNumber);
 648 }
 649
 650 /// isValidDwarfFileNumber - takes a dwarf file number and returns true if it
 651 /// currently is assigned and false otherwise.
 652 bool MCContext::isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID) {
 653   const MCDwarfLineTable &LineTable = getMCDwarfLineTable(CUID);
 654   if (FileNumber == 0)
 655     return getDwarfVersion() >= 5;
 656   if (FileNumber >= LineTable.getMCDwarfFiles().size())
 657     return false;
 658
 659   return !LineTable.getMCDwarfFiles()[FileNumber].Name.empty();
 660 }
 661
 662 /// Remove empty sections from SectionsForRanges, to avoid generating
 663 /// useless debug info for them.
 664 void MCContext::finalizeDwarfSections(MCStreamer &MCOS) {
 665   SectionsForRanges.remove_if(
 666       [&](MCSection *Sec) { return !MCOS.mayHaveInstructions(*Sec); });
 667 }
 668
 669 CodeViewContext &MCContext::getCVContext() {
 670   if (!CVContext.get())
 671     CVContext.reset(new CodeViewContext);
 672   return *CVContext.get();
 673 }
 674
 675 //===----------------------------------------------------------------------===//
 676 // Error Reporting
 677 //===----------------------------------------------------------------------===//
 678
 679 void MCContext::reportError(SMLoc Loc, const Twine &Msg) {
 680   HadError = true;
 681
 682   // If we have a source manager use it. Otherwise, try using the inline source
 683   // manager.
 684   // If that fails, use the generic report_fatal_error().
 685   if (SrcMgr)
 686     SrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
 687   else if (InlineSrcMgr)
 688     InlineSrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
 689   else
 690     report_fatal_error(Msg, false);
 691 }
 692
 693 void MCContext::reportFatalError(SMLoc Loc, const Twine &Msg) {
 694   reportError(Loc, Msg);
 695
 696   // If we reached here, we are failing ungracefully. Run the interrupt handlers
 697   // to make sure any special cleanups get done, in particular that we remove
 698   // files registered with RemoveFileOnSignal.
 699   sys::RunInterruptHandlers();
 700   exit(1);
 701 }