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 }
635