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/BinaryFormat/XCOFF.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/MCSectionXCOFF.h"
31 #include "llvm/MC/MCStreamer.h"
32 #include "llvm/MC/MCSymbol.h"
33 #include "llvm/MC/MCSymbolCOFF.h"
34 #include "llvm/MC/MCSymbolELF.h"
35 #include "llvm/MC/MCSymbolMachO.h"
36 #include "llvm/MC/MCSymbolWasm.h"
37 #include "llvm/MC/MCSymbolXCOFF.h"
38 #include "llvm/MC/SectionKind.h"
39 #include "llvm/Support/Casting.h"
40 #include "llvm/Support/CommandLine.h"
41 #include "llvm/Support/ErrorHandling.h"
42 #include "llvm/Support/MemoryBuffer.h"
43 #include "llvm/Support/Path.h"
44 #include "llvm/Support/Signals.h"
45 #include "llvm/Support/SourceMgr.h"
46 #include "llvm/Support/raw_ostream.h"
47 #include <cassert>
48 #include <cstdlib>
49 #include <tuple>
50 #include <utility>
51 
52 using namespace llvm;
53 
54 static cl::opt<char*>
55 AsSecureLogFileName("as-secure-log-file-name",
56         cl::desc("As secure log file name (initialized from "
57                  "AS_SECURE_LOG_FILE env variable)"),
58         cl::init(getenv("AS_SECURE_LOG_FILE")), cl::Hidden);
59 
60 MCContext::MCContext(const MCAsmInfo *mai, const MCRegisterInfo *mri,
61                      const MCObjectFileInfo *mofi, const SourceMgr *mgr,
62                      MCTargetOptions const *TargetOpts, bool DoAutoReset)
63     : SrcMgr(mgr), InlineSrcMgr(nullptr), MAI(mai), MRI(mri), MOFI(mofi),
64       Symbols(Allocator), UsedNames(Allocator),
65       InlineAsmUsedLabelNames(Allocator),
66       CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0),
67       AutoReset(DoAutoReset), TargetOptions(TargetOpts) {
68   SecureLogFile = AsSecureLogFileName;
69 
70   if (SrcMgr && SrcMgr->getNumBuffers())
71     MainFileName = std::string(SrcMgr->getMemoryBuffer(SrcMgr->getMainFileID())
72                                    ->getBufferIdentifier());
73 }
74 
75 MCContext::~MCContext() {
76   if (AutoReset)
77     reset();
78 
79   // NOTE: The symbols are all allocated out of a bump pointer allocator,
80   // we don't need to free them here.
81 }
82 
83 //===----------------------------------------------------------------------===//
84 // Module Lifetime Management
85 //===----------------------------------------------------------------------===//
86 
87 void MCContext::reset() {
88   // Call the destructors so the fragments are freed
89   COFFAllocator.DestroyAll();
90   ELFAllocator.DestroyAll();
91   MachOAllocator.DestroyAll();
92   XCOFFAllocator.DestroyAll();
93 
94   MCSubtargetAllocator.DestroyAll();
95   InlineAsmUsedLabelNames.clear();
96   UsedNames.clear();
97   Symbols.clear();
98   Allocator.Reset();
99   Instances.clear();
100   CompilationDir.clear();
101   MainFileName.clear();
102   MCDwarfLineTablesCUMap.clear();
103   SectionsForRanges.clear();
104   MCGenDwarfLabelEntries.clear();
105   DwarfDebugFlags = StringRef();
106   DwarfCompileUnitID = 0;
107   CurrentDwarfLoc = MCDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0);
108 
109   CVContext.reset();
110 
111   MachOUniquingMap.clear();
112   ELFUniquingMap.clear();
113   COFFUniquingMap.clear();
114   WasmUniquingMap.clear();
115   XCOFFUniquingMap.clear();
116 
117   ELFEntrySizeMap.clear();
118   ELFSeenGenericMergeableSections.clear();
119 
120   NextID.clear();
121   AllowTemporaryLabels = true;
122   DwarfLocSeen = false;
123   GenDwarfForAssembly = false;
124   GenDwarfFileNumber = 0;
125 
126   HadError = false;
127 }
128 
129 //===----------------------------------------------------------------------===//
130 // Symbol Manipulation
131 //===----------------------------------------------------------------------===//
132 
133 MCSymbol *MCContext::getOrCreateSymbol(const Twine &Name) {
134   SmallString<128> NameSV;
135   StringRef NameRef = Name.toStringRef(NameSV);
136 
137   assert(!NameRef.empty() && "Normal symbols cannot be unnamed!");
138 
139   MCSymbol *&Sym = Symbols[NameRef];
140   if (!Sym)
141     Sym = createSymbol(NameRef, false, false);
142 
143   return Sym;
144 }
145 
146 MCSymbol *MCContext::getOrCreateFrameAllocSymbol(StringRef FuncName,
147                                                  unsigned Idx) {
148   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
149                            "$frame_escape_" + Twine(Idx));
150 }
151 
152 MCSymbol *MCContext::getOrCreateParentFrameOffsetSymbol(StringRef FuncName) {
153   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
154                            "$parent_frame_offset");
155 }
156 
157 MCSymbol *MCContext::getOrCreateLSDASymbol(StringRef FuncName) {
158   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + "__ehtable$" +
159                            FuncName);
160 }
161 
162 MCSymbol *MCContext::createSymbolImpl(const StringMapEntry<bool> *Name,
163                                       bool IsTemporary) {
164   static_assert(std::is_trivially_destructible<MCSymbolCOFF>(),
165                 "MCSymbol classes must be trivially destructible");
166   static_assert(std::is_trivially_destructible<MCSymbolELF>(),
167                 "MCSymbol classes must be trivially destructible");
168   static_assert(std::is_trivially_destructible<MCSymbolMachO>(),
169                 "MCSymbol classes must be trivially destructible");
170   static_assert(std::is_trivially_destructible<MCSymbolWasm>(),
171                 "MCSymbol classes must be trivially destructible");
172   static_assert(std::is_trivially_destructible<MCSymbolXCOFF>(),
173                 "MCSymbol classes must be trivially destructible");
174   if (MOFI) {
175     switch (MOFI->getObjectFileType()) {
176     case MCObjectFileInfo::IsCOFF:
177       return new (Name, *this) MCSymbolCOFF(Name, IsTemporary);
178     case MCObjectFileInfo::IsELF:
179       return new (Name, *this) MCSymbolELF(Name, IsTemporary);
180     case MCObjectFileInfo::IsMachO:
181       return new (Name, *this) MCSymbolMachO(Name, IsTemporary);
182     case MCObjectFileInfo::IsWasm:
183       return new (Name, *this) MCSymbolWasm(Name, IsTemporary);
184     case MCObjectFileInfo::IsXCOFF:
185       return createXCOFFSymbolImpl(Name, IsTemporary);
186     }
187   }
188   return new (Name, *this) MCSymbol(MCSymbol::SymbolKindUnset, Name,
189                                     IsTemporary);
190 }
191 
192 MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
193                                   bool CanBeUnnamed) {
194   if (CanBeUnnamed && !UseNamesOnTempLabels)
195     return createSymbolImpl(nullptr, true);
196 
197   // Determine whether this is a user written assembler temporary or normal
198   // label, if used.
199   bool IsTemporary = CanBeUnnamed;
200   if (AllowTemporaryLabels && !IsTemporary)
201     IsTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
202 
203   SmallString<128> NewName = Name;
204   bool AddSuffix = AlwaysAddSuffix;
205   unsigned &NextUniqueID = NextID[Name];
206   while (true) {
207     if (AddSuffix) {
208       NewName.resize(Name.size());
209       raw_svector_ostream(NewName) << NextUniqueID++;
210     }
211     auto NameEntry = UsedNames.insert(std::make_pair(NewName, true));
212     if (NameEntry.second || !NameEntry.first->second) {
213       // Ok, we found a name.
214       // Mark it as used for a non-section symbol.
215       NameEntry.first->second = true;
216       // Have the MCSymbol object itself refer to the copy of the string that is
217       // embedded in the UsedNames entry.
218       return createSymbolImpl(&*NameEntry.first, IsTemporary);
219     }
220     assert(IsTemporary && "Cannot rename non-temporary symbols");
221     AddSuffix = true;
222   }
223   llvm_unreachable("Infinite loop");
224 }
225 
226 MCSymbol *MCContext::createTempSymbol(const Twine &Name, bool AlwaysAddSuffix,
227                                       bool CanBeUnnamed) {
228   SmallString<128> NameSV;
229   raw_svector_ostream(NameSV) << MAI->getPrivateGlobalPrefix() << Name;
230   return createSymbol(NameSV, AlwaysAddSuffix, CanBeUnnamed);
231 }
232 
233 MCSymbol *MCContext::createLinkerPrivateTempSymbol() {
234   SmallString<128> NameSV;
235   raw_svector_ostream(NameSV) << MAI->getLinkerPrivateGlobalPrefix() << "tmp";
236   return createSymbol(NameSV, true, false);
237 }
238 
239 MCSymbol *MCContext::createTempSymbol(bool CanBeUnnamed) {
240   return createTempSymbol("tmp", true, CanBeUnnamed);
241 }
242 
243 unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
244   MCLabel *&Label = Instances[LocalLabelVal];
245   if (!Label)
246     Label = new (*this) MCLabel(0);
247   return Label->incInstance();
248 }
249 
250 unsigned MCContext::GetInstance(unsigned LocalLabelVal) {
251   MCLabel *&Label = Instances[LocalLabelVal];
252   if (!Label)
253     Label = new (*this) MCLabel(0);
254   return Label->getInstance();
255 }
256 
257 MCSymbol *MCContext::getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
258                                                        unsigned Instance) {
259   MCSymbol *&Sym = LocalSymbols[std::make_pair(LocalLabelVal, Instance)];
260   if (!Sym)
261     Sym = createTempSymbol(false);
262   return Sym;
263 }
264 
265 MCSymbol *MCContext::createDirectionalLocalSymbol(unsigned LocalLabelVal) {
266   unsigned Instance = NextInstance(LocalLabelVal);
267   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
268 }
269 
270 MCSymbol *MCContext::getDirectionalLocalSymbol(unsigned LocalLabelVal,
271                                                bool Before) {
272   unsigned Instance = GetInstance(LocalLabelVal);
273   if (!Before)
274     ++Instance;
275   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
276 }
277 
278 MCSymbol *MCContext::lookupSymbol(const Twine &Name) const {
279   SmallString<128> NameSV;
280   StringRef NameRef = Name.toStringRef(NameSV);
281   return Symbols.lookup(NameRef);
282 }
283 
284 void MCContext::setSymbolValue(MCStreamer &Streamer,
285                               StringRef Sym,
286                               uint64_t Val) {
287   auto Symbol = getOrCreateSymbol(Sym);
288   Streamer.emitAssignment(Symbol, MCConstantExpr::create(Val, *this));
289 }
290 
291 void MCContext::registerInlineAsmLabel(MCSymbol *Sym) {
292   InlineAsmUsedLabelNames[Sym->getName()] = Sym;
293 }
294 
295 MCSymbolXCOFF *
296 MCContext::createXCOFFSymbolImpl(const StringMapEntry<bool> *Name,
297                                  bool IsTemporary) {
298   if (!Name)
299     return new (nullptr, *this) MCSymbolXCOFF(nullptr, IsTemporary);
300 
301   StringRef OriginalName = Name->first();
302   if (OriginalName.startswith("._Renamed..") ||
303       OriginalName.startswith("_Renamed.."))
304     reportError(SMLoc(), "invalid symbol name from source");
305 
306   if (MAI->isValidUnquotedName(OriginalName))
307     return new (Name, *this) MCSymbolXCOFF(Name, IsTemporary);
308 
309   // Now we have a name that contains invalid character(s) for XCOFF symbol.
310   // Let's replace with something valid, but save the original name so that
311   // we could still use the original name in the symbol table.
312   SmallString<128> InvalidName(OriginalName);
313 
314   // If it's an entry point symbol, we will keep the '.'
315   // in front for the convention purpose. Otherwise, add "_Renamed.."
316   // as prefix to signal this is an renamed symbol.
317   const bool IsEntryPoint = !InvalidName.empty() && InvalidName[0] == '.';
318   SmallString<128> ValidName =
319       StringRef(IsEntryPoint ? "._Renamed.." : "_Renamed..");
320 
321   // Append the hex values of '_' and invalid characters with "_Renamed..";
322   // at the same time replace invalid characters with '_'.
323   for (size_t I = 0; I < InvalidName.size(); ++I) {
324     if (!MAI->isAcceptableChar(InvalidName[I]) || InvalidName[I] == '_') {
325       raw_svector_ostream(ValidName).write_hex(InvalidName[I]);
326       InvalidName[I] = '_';
327     }
328   }
329 
330   // Skip entry point symbol's '.' as we already have a '.' in front of
331   // "_Renamed".
332   if (IsEntryPoint)
333     ValidName.append(InvalidName.substr(1, InvalidName.size() - 1));
334   else
335     ValidName.append(InvalidName);
336 
337   auto NameEntry = UsedNames.insert(std::make_pair(ValidName, true));
338   assert((NameEntry.second || !NameEntry.first->second) &&
339          "This name is used somewhere else.");
340   // Mark the name as used for a non-section symbol.
341   NameEntry.first->second = true;
342   // Have the MCSymbol object itself refer to the copy of the string
343   // that is embedded in the UsedNames entry.
344   MCSymbolXCOFF *XSym = new (&*NameEntry.first, *this)
345       MCSymbolXCOFF(&*NameEntry.first, IsTemporary);
346   XSym->setSymbolTableName(MCSymbolXCOFF::getUnqualifiedName(OriginalName));
347   return XSym;
348 }
349 
350 //===----------------------------------------------------------------------===//
351 // Section Management
352 //===----------------------------------------------------------------------===//
353 
354 MCSectionMachO *MCContext::getMachOSection(StringRef Segment, StringRef Section,
355                                            unsigned TypeAndAttributes,
356                                            unsigned Reserved2, SectionKind Kind,
357                                            const char *BeginSymName) {
358   // We unique sections by their segment/section pair.  The returned section
359   // may not have the same flags as the requested section, if so this should be
360   // diagnosed by the client as an error.
361 
362   // Form the name to look up.
363   assert(Section.size() <= 16 && "section name is too long");
364   assert(!memchr(Section.data(), '\0', Section.size()) &&
365          "section name cannot contain NUL");
366 
367   // Do the lookup, if we have a hit, return it.
368   auto R = MachOUniquingMap.try_emplace((Segment + Twine(',') + Section).str());
369   if (!R.second)
370     return R.first->second;
371 
372   MCSymbol *Begin = nullptr;
373   if (BeginSymName)
374     Begin = createTempSymbol(BeginSymName, false);
375 
376   // Otherwise, return a new section.
377   StringRef Name = R.first->first();
378   R.first->second = new (MachOAllocator.Allocate())
379       MCSectionMachO(Segment, Name.substr(Name.size() - Section.size()),
380                      TypeAndAttributes, Reserved2, Kind, Begin);
381   return R.first->second;
382 }
383 
384 void MCContext::renameELFSection(MCSectionELF *Section, StringRef Name) {
385   StringRef GroupName;
386   if (const MCSymbol *Group = Section->getGroup())
387     GroupName = Group->getName();
388 
389   // This function is only used by .debug*, which should not have the
390   // SHF_LINK_ORDER flag.
391   unsigned UniqueID = Section->getUniqueID();
392   ELFUniquingMap.erase(
393       ELFSectionKey{Section->getName(), GroupName, "", UniqueID});
394   auto I = ELFUniquingMap
395                .insert(std::make_pair(
396                    ELFSectionKey{Name, GroupName, "", UniqueID}, Section))
397                .first;
398   StringRef CachedName = I->first.SectionName;
399   const_cast<MCSectionELF *>(Section)->setSectionName(CachedName);
400 }
401 
402 MCSectionELF *MCContext::createELFSectionImpl(StringRef Section, unsigned Type,
403                                               unsigned Flags, SectionKind K,
404                                               unsigned EntrySize,
405                                               const MCSymbolELF *Group,
406                                               unsigned UniqueID,
407                                               const MCSymbolELF *LinkedToSym) {
408   MCSymbolELF *R;
409   MCSymbol *&Sym = Symbols[Section];
410   // A section symbol can not redefine regular symbols. There may be multiple
411   // sections with the same name, in which case the first such section wins.
412   if (Sym && Sym->isDefined() &&
413       (!Sym->isInSection() || Sym->getSection().getBeginSymbol() != Sym))
414     reportError(SMLoc(), "invalid symbol redefinition");
415   if (Sym && Sym->isUndefined()) {
416     R = cast<MCSymbolELF>(Sym);
417   } else {
418     auto NameIter = UsedNames.insert(std::make_pair(Section, false)).first;
419     R = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
420     if (!Sym)
421       Sym = R;
422   }
423   R->setBinding(ELF::STB_LOCAL);
424   R->setType(ELF::STT_SECTION);
425 
426   auto *Ret = new (ELFAllocator.Allocate()) MCSectionELF(
427       Section, Type, Flags, K, EntrySize, Group, UniqueID, R, LinkedToSym);
428 
429   auto *F = new MCDataFragment();
430   Ret->getFragmentList().insert(Ret->begin(), F);
431   F->setParent(Ret);
432   R->setFragment(F);
433 
434   return Ret;
435 }
436 
437 MCSectionELF *MCContext::createELFRelSection(const Twine &Name, unsigned Type,
438                                              unsigned Flags, unsigned EntrySize,
439                                              const MCSymbolELF *Group,
440                                              const MCSectionELF *RelInfoSection) {
441   StringMap<bool>::iterator I;
442   bool Inserted;
443   std::tie(I, Inserted) =
444       RelSecNames.insert(std::make_pair(Name.str(), true));
445 
446   return createELFSectionImpl(
447       I->getKey(), Type, Flags, SectionKind::getReadOnly(), EntrySize, Group,
448       true, cast<MCSymbolELF>(RelInfoSection->getBeginSymbol()));
449 }
450 
451 MCSectionELF *MCContext::getELFNamedSection(const Twine &Prefix,
452                                             const Twine &Suffix, unsigned Type,
453                                             unsigned Flags,
454                                             unsigned EntrySize) {
455   return getELFSection(Prefix + "." + Suffix, Type, Flags, EntrySize, Suffix);
456 }
457 
458 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
459                                        unsigned Flags, unsigned EntrySize,
460                                        const Twine &Group, unsigned UniqueID,
461                                        const MCSymbolELF *LinkedToSym) {
462   MCSymbolELF *GroupSym = nullptr;
463   if (!Group.isTriviallyEmpty() && !Group.str().empty())
464     GroupSym = cast<MCSymbolELF>(getOrCreateSymbol(Group));
465 
466   return getELFSection(Section, Type, Flags, EntrySize, GroupSym, UniqueID,
467                        LinkedToSym);
468 }
469 
470 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
471                                        unsigned Flags, unsigned EntrySize,
472                                        const MCSymbolELF *GroupSym,
473                                        unsigned UniqueID,
474                                        const MCSymbolELF *LinkedToSym) {
475   StringRef Group = "";
476   if (GroupSym)
477     Group = GroupSym->getName();
478   assert(!(LinkedToSym && LinkedToSym->getName().empty()));
479   // Do the lookup, if we have a hit, return it.
480   auto IterBool = ELFUniquingMap.insert(std::make_pair(
481       ELFSectionKey{Section.str(), Group,
482                     LinkedToSym ? LinkedToSym->getName() : "", UniqueID},
483       nullptr));
484   auto &Entry = *IterBool.first;
485   if (!IterBool.second)
486     return Entry.second;
487 
488   StringRef CachedName = Entry.first.SectionName;
489 
490   SectionKind Kind;
491   if (Flags & ELF::SHF_ARM_PURECODE)
492     Kind = SectionKind::getExecuteOnly();
493   else if (Flags & ELF::SHF_EXECINSTR)
494     Kind = SectionKind::getText();
495   else
496     Kind = SectionKind::getReadOnly();
497 
498   MCSectionELF *Result =
499       createELFSectionImpl(CachedName, Type, Flags, Kind, EntrySize, GroupSym,
500                            UniqueID, LinkedToSym);
501   Entry.second = Result;
502 
503   recordELFMergeableSectionInfo(Result->getName(), Result->getFlags(),
504                                 Result->getUniqueID(), Result->getEntrySize());
505 
506   return Result;
507 }
508 
509 MCSectionELF *MCContext::createELFGroupSection(const MCSymbolELF *Group) {
510   return createELFSectionImpl(".group", ELF::SHT_GROUP, 0,
511                               SectionKind::getReadOnly(), 4, Group,
512                               MCSection::NonUniqueID, nullptr);
513 }
514 
515 void MCContext::recordELFMergeableSectionInfo(StringRef SectionName,
516                                               unsigned Flags, unsigned UniqueID,
517                                               unsigned EntrySize) {
518   bool IsMergeable = Flags & ELF::SHF_MERGE;
519   if (IsMergeable && (UniqueID == GenericSectionID))
520     ELFSeenGenericMergeableSections.insert(SectionName);
521 
522   // For mergeable sections or non-mergeable sections with a generic mergeable
523   // section name we enter their Unique ID into the ELFEntrySizeMap so that
524   // compatible globals can be assigned to the same section.
525   if (IsMergeable || isELFGenericMergeableSection(SectionName)) {
526     ELFEntrySizeMap.insert(std::make_pair(
527         ELFEntrySizeKey{SectionName, Flags, EntrySize}, UniqueID));
528   }
529 }
530 
531 bool MCContext::isELFImplicitMergeableSectionNamePrefix(StringRef SectionName) {
532   return SectionName.startswith(".rodata.str") ||
533          SectionName.startswith(".rodata.cst");
534 }
535 
536 bool MCContext::isELFGenericMergeableSection(StringRef SectionName) {
537   return isELFImplicitMergeableSectionNamePrefix(SectionName) ||
538          ELFSeenGenericMergeableSections.count(SectionName);
539 }
540 
541 Optional<unsigned> MCContext::getELFUniqueIDForEntsize(StringRef SectionName,
542                                                        unsigned Flags,
543                                                        unsigned EntrySize) {
544   auto I = ELFEntrySizeMap.find(
545       MCContext::ELFEntrySizeKey{SectionName, Flags, EntrySize});
546   return (I != ELFEntrySizeMap.end()) ? Optional<unsigned>(I->second) : None;
547 }
548 
549 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
550                                          unsigned Characteristics,
551                                          SectionKind Kind,
552                                          StringRef COMDATSymName, int Selection,
553                                          unsigned UniqueID,
554                                          const char *BeginSymName) {
555   MCSymbol *COMDATSymbol = nullptr;
556   if (!COMDATSymName.empty()) {
557     COMDATSymbol = getOrCreateSymbol(COMDATSymName);
558     COMDATSymName = COMDATSymbol->getName();
559   }
560 
561 
562   // Do the lookup, if we have a hit, return it.
563   COFFSectionKey T{Section, COMDATSymName, Selection, UniqueID};
564   auto IterBool = COFFUniquingMap.insert(std::make_pair(T, nullptr));
565   auto Iter = IterBool.first;
566   if (!IterBool.second)
567     return Iter->second;
568 
569   MCSymbol *Begin = nullptr;
570   if (BeginSymName)
571     Begin = createTempSymbol(BeginSymName, false);
572 
573   StringRef CachedName = Iter->first.SectionName;
574   MCSectionCOFF *Result = new (COFFAllocator.Allocate()) MCSectionCOFF(
575       CachedName, Characteristics, COMDATSymbol, Selection, Kind, Begin);
576 
577   Iter->second = Result;
578   return Result;
579 }
580 
581 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
582                                          unsigned Characteristics,
583                                          SectionKind Kind,
584                                          const char *BeginSymName) {
585   return getCOFFSection(Section, Characteristics, Kind, "", 0, GenericSectionID,
586                         BeginSymName);
587 }
588 
589 MCSectionCOFF *MCContext::getAssociativeCOFFSection(MCSectionCOFF *Sec,
590                                                     const MCSymbol *KeySym,
591                                                     unsigned UniqueID) {
592   // Return the normal section if we don't have to be associative or unique.
593   if (!KeySym && UniqueID == GenericSectionID)
594     return Sec;
595 
596   // If we have a key symbol, make an associative section with the same name and
597   // kind as the normal section.
598   unsigned Characteristics = Sec->getCharacteristics();
599   if (KeySym) {
600     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
601     return getCOFFSection(Sec->getName(), Characteristics, Sec->getKind(),
602                           KeySym->getName(),
603                           COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
604   }
605 
606   return getCOFFSection(Sec->getName(), Characteristics, Sec->getKind(), "", 0,
607                         UniqueID);
608 }
609 
610 MCSectionWasm *MCContext::getWasmSection(const Twine &Section, SectionKind K,
611                                          const Twine &Group, unsigned UniqueID,
612                                          const char *BeginSymName) {
613   MCSymbolWasm *GroupSym = nullptr;
614   if (!Group.isTriviallyEmpty() && !Group.str().empty()) {
615     GroupSym = cast<MCSymbolWasm>(getOrCreateSymbol(Group));
616     GroupSym->setComdat(true);
617   }
618 
619   return getWasmSection(Section, K, GroupSym, UniqueID, BeginSymName);
620 }
621 
622 MCSectionWasm *MCContext::getWasmSection(const Twine &Section, SectionKind Kind,
623                                          const MCSymbolWasm *GroupSym,
624                                          unsigned UniqueID,
625                                          const char *BeginSymName) {
626   StringRef Group = "";
627   if (GroupSym)
628     Group = GroupSym->getName();
629   // Do the lookup, if we have a hit, return it.
630   auto IterBool = WasmUniquingMap.insert(
631       std::make_pair(WasmSectionKey{Section.str(), Group, UniqueID}, nullptr));
632   auto &Entry = *IterBool.first;
633   if (!IterBool.second)
634     return Entry.second;
635 
636   StringRef CachedName = Entry.first.SectionName;
637 
638   MCSymbol *Begin = createSymbol(CachedName, false, false);
639   cast<MCSymbolWasm>(Begin)->setType(wasm::WASM_SYMBOL_TYPE_SECTION);
640 
641   MCSectionWasm *Result = new (WasmAllocator.Allocate())
642       MCSectionWasm(CachedName, Kind, GroupSym, UniqueID, Begin);
643   Entry.second = Result;
644 
645   auto *F = new MCDataFragment();
646   Result->getFragmentList().insert(Result->begin(), F);
647   F->setParent(Result);
648   Begin->setFragment(F);
649 
650   return Result;
651 }
652 
653 MCSectionXCOFF *MCContext::getXCOFFSection(StringRef Section,
654                                            XCOFF::StorageMappingClass SMC,
655                                            XCOFF::SymbolType Type,
656                                            XCOFF::StorageClass SC,
657                                            SectionKind Kind,
658                                            const char *BeginSymName) {
659   // Do the lookup. If we have a hit, return it.
660   auto IterBool = XCOFFUniquingMap.insert(
661       std::make_pair(XCOFFSectionKey{Section.str(), SMC}, nullptr));
662   auto &Entry = *IterBool.first;
663   if (!IterBool.second)
664     return Entry.second;
665 
666   // Otherwise, return a new section.
667   StringRef CachedName = Entry.first.SectionName;
668   MCSymbolXCOFF *QualName = cast<MCSymbolXCOFF>(getOrCreateSymbol(
669       CachedName + "[" + XCOFF::getMappingClassString(SMC) + "]"));
670 
671   MCSymbol *Begin = nullptr;
672   if (BeginSymName)
673     Begin = createTempSymbol(BeginSymName, false);
674 
675   // QualName->getUnqualifiedName() and CachedName are the same except when
676   // CachedName contains invalid character(s) such as '$' for an XCOFF symbol.
677   MCSectionXCOFF *Result = new (XCOFFAllocator.Allocate())
678       MCSectionXCOFF(QualName->getUnqualifiedName(), SMC, Type, SC, Kind,
679                      QualName, Begin, CachedName);
680   Entry.second = Result;
681 
682   auto *F = new MCDataFragment();
683   Result->getFragmentList().insert(Result->begin(), F);
684   F->setParent(Result);
685 
686   if (Begin)
687     Begin->setFragment(F);
688 
689   return Result;
690 }
691 
692 MCSubtargetInfo &MCContext::getSubtargetCopy(const MCSubtargetInfo &STI) {
693   return *new (MCSubtargetAllocator.Allocate()) MCSubtargetInfo(STI);
694 }
695 
696 void MCContext::addDebugPrefixMapEntry(const std::string &From,
697                                        const std::string &To) {
698   DebugPrefixMap.insert(std::make_pair(From, To));
699 }
700 
701 void MCContext::RemapDebugPaths() {
702   const auto &DebugPrefixMap = this->DebugPrefixMap;
703   if (DebugPrefixMap.empty())
704     return;
705 
706   const auto RemapDebugPath = [&DebugPrefixMap](std::string &Path) {
707     SmallString<256> P(Path);
708     for (const auto &Entry : DebugPrefixMap) {
709       if (llvm::sys::path::replace_path_prefix(P, Entry.first, Entry.second)) {
710         Path = P.str().str();
711         break;
712       }
713     }
714   };
715 
716   // Remap compilation directory.
717   std::string CompDir = std::string(CompilationDir.str());
718   RemapDebugPath(CompDir);
719   CompilationDir = CompDir;
720 
721   // Remap MCDwarfDirs in all compilation units.
722   for (auto &CUIDTablePair : MCDwarfLineTablesCUMap)
723     for (auto &Dir : CUIDTablePair.second.getMCDwarfDirs())
724       RemapDebugPath(Dir);
725 }
726 
727 //===----------------------------------------------------------------------===//
728 // Dwarf Management
729 //===----------------------------------------------------------------------===//
730 
731 void MCContext::setGenDwarfRootFile(StringRef InputFileName, StringRef Buffer) {
732   // MCDwarf needs the root file as well as the compilation directory.
733   // If we find a '.file 0' directive that will supersede these values.
734   Optional<MD5::MD5Result> Cksum;
735   if (getDwarfVersion() >= 5) {
736     MD5 Hash;
737     MD5::MD5Result Sum;
738     Hash.update(Buffer);
739     Hash.final(Sum);
740     Cksum = Sum;
741   }
742   // Canonicalize the root filename. It cannot be empty, and should not
743   // repeat the compilation dir.
744   // The MCContext ctor initializes MainFileName to the name associated with
745   // the SrcMgr's main file ID, which might be the same as InputFileName (and
746   // possibly include directory components).
747   // Or, MainFileName might have been overridden by a -main-file-name option,
748   // which is supposed to be just a base filename with no directory component.
749   // So, if the InputFileName and MainFileName are not equal, assume
750   // MainFileName is a substitute basename and replace the last component.
751   SmallString<1024> FileNameBuf = InputFileName;
752   if (FileNameBuf.empty() || FileNameBuf == "-")
753     FileNameBuf = "<stdin>";
754   if (!getMainFileName().empty() && FileNameBuf != getMainFileName()) {
755     llvm::sys::path::remove_filename(FileNameBuf);
756     llvm::sys::path::append(FileNameBuf, getMainFileName());
757   }
758   StringRef FileName = FileNameBuf;
759   if (FileName.consume_front(getCompilationDir()))
760     if (llvm::sys::path::is_separator(FileName.front()))
761       FileName = FileName.drop_front();
762   assert(!FileName.empty());
763   setMCLineTableRootFile(
764       /*CUID=*/0, getCompilationDir(), FileName, Cksum, None);
765 }
766 
767 /// getDwarfFile - takes a file name and number to place in the dwarf file and
768 /// directory tables.  If the file number has already been allocated it is an
769 /// error and zero is returned and the client reports the error, else the
770 /// allocated file number is returned.  The file numbers may be in any order.
771 Expected<unsigned> MCContext::getDwarfFile(StringRef Directory,
772                                            StringRef FileName,
773                                            unsigned FileNumber,
774                                            Optional<MD5::MD5Result> Checksum,
775                                            Optional<StringRef> Source,
776                                            unsigned CUID) {
777   MCDwarfLineTable &Table = MCDwarfLineTablesCUMap[CUID];
778   return Table.tryGetFile(Directory, FileName, Checksum, Source, DwarfVersion,
779                           FileNumber);
780 }
781 
782 /// isValidDwarfFileNumber - takes a dwarf file number and returns true if it
783 /// currently is assigned and false otherwise.
784 bool MCContext::isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID) {
785   const MCDwarfLineTable &LineTable = getMCDwarfLineTable(CUID);
786   if (FileNumber == 0)
787     return getDwarfVersion() >= 5;
788   if (FileNumber >= LineTable.getMCDwarfFiles().size())
789     return false;
790 
791   return !LineTable.getMCDwarfFiles()[FileNumber].Name.empty();
792 }
793 
794 /// Remove empty sections from SectionsForRanges, to avoid generating
795 /// useless debug info for them.
796 void MCContext::finalizeDwarfSections(MCStreamer &MCOS) {
797   SectionsForRanges.remove_if(
798       [&](MCSection *Sec) { return !MCOS.mayHaveInstructions(*Sec); });
799 }
800 
801 CodeViewContext &MCContext::getCVContext() {
802   if (!CVContext.get())
803     CVContext.reset(new CodeViewContext);
804   return *CVContext.get();
805 }
806 
807 //===----------------------------------------------------------------------===//
808 // Error Reporting
809 //===----------------------------------------------------------------------===//
810 
811 void MCContext::reportError(SMLoc Loc, const Twine &Msg) {
812   HadError = true;
813 
814   // If we have a source manager use it. Otherwise, try using the inline source
815   // manager.
816   // If that fails, use the generic report_fatal_error().
817   if (SrcMgr)
818     SrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
819   else if (InlineSrcMgr)
820     InlineSrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
821   else
822     report_fatal_error(Msg, false);
823 }
824 
825 void MCContext::reportWarning(SMLoc Loc, const Twine &Msg) {
826   if (TargetOptions && TargetOptions->MCNoWarn)
827     return;
828   if (TargetOptions && TargetOptions->MCFatalWarnings)
829     reportError(Loc, Msg);
830   else {
831     // If we have a source manager use it. Otherwise, try using the inline
832     // source manager.
833     if (SrcMgr)
834       SrcMgr->PrintMessage(Loc, SourceMgr::DK_Warning, Msg);
835     else if (InlineSrcMgr)
836       InlineSrcMgr->PrintMessage(Loc, SourceMgr::DK_Warning, Msg);
837   }
838 }
839 
840 void MCContext::reportFatalError(SMLoc Loc, const Twine &Msg) {
841   reportError(Loc, Msg);
842 
843   // If we reached here, we are failing ungracefully. Run the interrupt handlers
844   // to make sure any special cleanups get done, in particular that we remove
845   // files registered with RemoveFileOnSignal.
846   sys::RunInterruptHandlers();
847   exit(1);
848 }
849