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   MCInstAllocator.DestroyAll();
94 
95   MCSubtargetAllocator.DestroyAll();
96   InlineAsmUsedLabelNames.clear();
97   UsedNames.clear();
98   Symbols.clear();
99   Allocator.Reset();
100   Instances.clear();
101   CompilationDir.clear();
102   MainFileName.clear();
103   MCDwarfLineTablesCUMap.clear();
104   SectionsForRanges.clear();
105   MCGenDwarfLabelEntries.clear();
106   DwarfDebugFlags = StringRef();
107   DwarfCompileUnitID = 0;
108   CurrentDwarfLoc = MCDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0);
109 
110   CVContext.reset();
111 
112   MachOUniquingMap.clear();
113   ELFUniquingMap.clear();
114   COFFUniquingMap.clear();
115   WasmUniquingMap.clear();
116   XCOFFUniquingMap.clear();
117 
118   ELFEntrySizeMap.clear();
119   ELFSeenGenericMergeableSections.clear();
120 
121   NextID.clear();
122   AllowTemporaryLabels = true;
123   DwarfLocSeen = false;
124   GenDwarfForAssembly = false;
125   GenDwarfFileNumber = 0;
126 
127   HadError = false;
128 }
129 
130 //===----------------------------------------------------------------------===//
131 // MCInst Management
132 //===----------------------------------------------------------------------===//
133 
134 MCInst *MCContext::createMCInst() {
135   return new (MCInstAllocator.Allocate()) MCInst;
136 }
137 
138 //===----------------------------------------------------------------------===//
139 // Symbol Manipulation
140 //===----------------------------------------------------------------------===//
141 
142 MCSymbol *MCContext::getOrCreateSymbol(const Twine &Name) {
143   SmallString<128> NameSV;
144   StringRef NameRef = Name.toStringRef(NameSV);
145 
146   assert(!NameRef.empty() && "Normal symbols cannot be unnamed!");
147 
148   MCSymbol *&Sym = Symbols[NameRef];
149   if (!Sym)
150     Sym = createSymbol(NameRef, false, false);
151 
152   return Sym;
153 }
154 
155 MCSymbol *MCContext::getOrCreateFrameAllocSymbol(StringRef FuncName,
156                                                  unsigned Idx) {
157   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
158                            "$frame_escape_" + Twine(Idx));
159 }
160 
161 MCSymbol *MCContext::getOrCreateParentFrameOffsetSymbol(StringRef FuncName) {
162   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
163                            "$parent_frame_offset");
164 }
165 
166 MCSymbol *MCContext::getOrCreateLSDASymbol(StringRef FuncName) {
167   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + "__ehtable$" +
168                            FuncName);
169 }
170 
171 MCSymbol *MCContext::createSymbolImpl(const StringMapEntry<bool> *Name,
172                                       bool IsTemporary) {
173   static_assert(std::is_trivially_destructible<MCSymbolCOFF>(),
174                 "MCSymbol classes must be trivially destructible");
175   static_assert(std::is_trivially_destructible<MCSymbolELF>(),
176                 "MCSymbol classes must be trivially destructible");
177   static_assert(std::is_trivially_destructible<MCSymbolMachO>(),
178                 "MCSymbol classes must be trivially destructible");
179   static_assert(std::is_trivially_destructible<MCSymbolWasm>(),
180                 "MCSymbol classes must be trivially destructible");
181   static_assert(std::is_trivially_destructible<MCSymbolXCOFF>(),
182                 "MCSymbol classes must be trivially destructible");
183   if (MOFI) {
184     switch (MOFI->getObjectFileType()) {
185     case MCObjectFileInfo::IsCOFF:
186       return new (Name, *this) MCSymbolCOFF(Name, IsTemporary);
187     case MCObjectFileInfo::IsELF:
188       return new (Name, *this) MCSymbolELF(Name, IsTemporary);
189     case MCObjectFileInfo::IsMachO:
190       return new (Name, *this) MCSymbolMachO(Name, IsTemporary);
191     case MCObjectFileInfo::IsWasm:
192       return new (Name, *this) MCSymbolWasm(Name, IsTemporary);
193     case MCObjectFileInfo::IsXCOFF:
194       return createXCOFFSymbolImpl(Name, IsTemporary);
195     }
196   }
197   return new (Name, *this) MCSymbol(MCSymbol::SymbolKindUnset, Name,
198                                     IsTemporary);
199 }
200 
201 MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
202                                   bool CanBeUnnamed) {
203   if (CanBeUnnamed && !UseNamesOnTempLabels)
204     return createSymbolImpl(nullptr, true);
205 
206   // Determine whether this is a user written assembler temporary or normal
207   // label, if used.
208   bool IsTemporary = CanBeUnnamed;
209   if (AllowTemporaryLabels && !IsTemporary)
210     IsTemporary = Name.startswith(MAI->getPrivateGlobalPrefix());
211 
212   SmallString<128> NewName = Name;
213   bool AddSuffix = AlwaysAddSuffix;
214   unsigned &NextUniqueID = NextID[Name];
215   while (true) {
216     if (AddSuffix) {
217       NewName.resize(Name.size());
218       raw_svector_ostream(NewName) << NextUniqueID++;
219     }
220     auto NameEntry = UsedNames.insert(std::make_pair(NewName, true));
221     if (NameEntry.second || !NameEntry.first->second) {
222       // Ok, we found a name.
223       // Mark it as used for a non-section symbol.
224       NameEntry.first->second = true;
225       // Have the MCSymbol object itself refer to the copy of the string that is
226       // embedded in the UsedNames entry.
227       return createSymbolImpl(&*NameEntry.first, IsTemporary);
228     }
229     assert(IsTemporary && "Cannot rename non-temporary symbols");
230     AddSuffix = true;
231   }
232   llvm_unreachable("Infinite loop");
233 }
234 
235 MCSymbol *MCContext::createTempSymbol(const Twine &Name, bool AlwaysAddSuffix,
236                                       bool CanBeUnnamed) {
237   SmallString<128> NameSV;
238   raw_svector_ostream(NameSV) << MAI->getPrivateGlobalPrefix() << Name;
239   return createSymbol(NameSV, AlwaysAddSuffix, CanBeUnnamed);
240 }
241 
242 MCSymbol *MCContext::createLinkerPrivateTempSymbol() {
243   SmallString<128> NameSV;
244   raw_svector_ostream(NameSV) << MAI->getLinkerPrivateGlobalPrefix() << "tmp";
245   return createSymbol(NameSV, true, false);
246 }
247 
248 MCSymbol *MCContext::createTempSymbol(bool CanBeUnnamed) {
249   return createTempSymbol("tmp", true, CanBeUnnamed);
250 }
251 
252 unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
253   MCLabel *&Label = Instances[LocalLabelVal];
254   if (!Label)
255     Label = new (*this) MCLabel(0);
256   return Label->incInstance();
257 }
258 
259 unsigned MCContext::GetInstance(unsigned LocalLabelVal) {
260   MCLabel *&Label = Instances[LocalLabelVal];
261   if (!Label)
262     Label = new (*this) MCLabel(0);
263   return Label->getInstance();
264 }
265 
266 MCSymbol *MCContext::getOrCreateDirectionalLocalSymbol(unsigned LocalLabelVal,
267                                                        unsigned Instance) {
268   MCSymbol *&Sym = LocalSymbols[std::make_pair(LocalLabelVal, Instance)];
269   if (!Sym)
270     Sym = createTempSymbol(false);
271   return Sym;
272 }
273 
274 MCSymbol *MCContext::createDirectionalLocalSymbol(unsigned LocalLabelVal) {
275   unsigned Instance = NextInstance(LocalLabelVal);
276   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
277 }
278 
279 MCSymbol *MCContext::getDirectionalLocalSymbol(unsigned LocalLabelVal,
280                                                bool Before) {
281   unsigned Instance = GetInstance(LocalLabelVal);
282   if (!Before)
283     ++Instance;
284   return getOrCreateDirectionalLocalSymbol(LocalLabelVal, Instance);
285 }
286 
287 MCSymbol *MCContext::lookupSymbol(const Twine &Name) const {
288   SmallString<128> NameSV;
289   StringRef NameRef = Name.toStringRef(NameSV);
290   return Symbols.lookup(NameRef);
291 }
292 
293 void MCContext::setSymbolValue(MCStreamer &Streamer,
294                               StringRef Sym,
295                               uint64_t Val) {
296   auto Symbol = getOrCreateSymbol(Sym);
297   Streamer.emitAssignment(Symbol, MCConstantExpr::create(Val, *this));
298 }
299 
300 void MCContext::registerInlineAsmLabel(MCSymbol *Sym) {
301   InlineAsmUsedLabelNames[Sym->getName()] = Sym;
302 }
303 
304 MCSymbolXCOFF *
305 MCContext::createXCOFFSymbolImpl(const StringMapEntry<bool> *Name,
306                                  bool IsTemporary) {
307   if (!Name)
308     return new (nullptr, *this) MCSymbolXCOFF(nullptr, IsTemporary);
309 
310   StringRef OriginalName = Name->first();
311   if (OriginalName.startswith("._Renamed..") ||
312       OriginalName.startswith("_Renamed.."))
313     reportError(SMLoc(), "invalid symbol name from source");
314 
315   if (MAI->isValidUnquotedName(OriginalName))
316     return new (Name, *this) MCSymbolXCOFF(Name, IsTemporary);
317 
318   // Now we have a name that contains invalid character(s) for XCOFF symbol.
319   // Let's replace with something valid, but save the original name so that
320   // we could still use the original name in the symbol table.
321   SmallString<128> InvalidName(OriginalName);
322 
323   // If it's an entry point symbol, we will keep the '.'
324   // in front for the convention purpose. Otherwise, add "_Renamed.."
325   // as prefix to signal this is an renamed symbol.
326   const bool IsEntryPoint = !InvalidName.empty() && InvalidName[0] == '.';
327   SmallString<128> ValidName =
328       StringRef(IsEntryPoint ? "._Renamed.." : "_Renamed..");
329 
330   // Append the hex values of '_' and invalid characters with "_Renamed..";
331   // at the same time replace invalid characters with '_'.
332   for (size_t I = 0; I < InvalidName.size(); ++I) {
333     if (!MAI->isAcceptableChar(InvalidName[I]) || InvalidName[I] == '_') {
334       raw_svector_ostream(ValidName).write_hex(InvalidName[I]);
335       InvalidName[I] = '_';
336     }
337   }
338 
339   // Skip entry point symbol's '.' as we already have a '.' in front of
340   // "_Renamed".
341   if (IsEntryPoint)
342     ValidName.append(InvalidName.substr(1, InvalidName.size() - 1));
343   else
344     ValidName.append(InvalidName);
345 
346   auto NameEntry = UsedNames.insert(std::make_pair(ValidName, true));
347   assert((NameEntry.second || !NameEntry.first->second) &&
348          "This name is used somewhere else.");
349   // Mark the name as used for a non-section symbol.
350   NameEntry.first->second = true;
351   // Have the MCSymbol object itself refer to the copy of the string
352   // that is embedded in the UsedNames entry.
353   MCSymbolXCOFF *XSym = new (&*NameEntry.first, *this)
354       MCSymbolXCOFF(&*NameEntry.first, IsTemporary);
355   XSym->setSymbolTableName(MCSymbolXCOFF::getUnqualifiedName(OriginalName));
356   return XSym;
357 }
358 
359 //===----------------------------------------------------------------------===//
360 // Section Management
361 //===----------------------------------------------------------------------===//
362 
363 MCSectionMachO *MCContext::getMachOSection(StringRef Segment, StringRef Section,
364                                            unsigned TypeAndAttributes,
365                                            unsigned Reserved2, SectionKind Kind,
366                                            const char *BeginSymName) {
367   // We unique sections by their segment/section pair.  The returned section
368   // may not have the same flags as the requested section, if so this should be
369   // diagnosed by the client as an error.
370 
371   // Form the name to look up.
372   assert(Section.size() <= 16 && "section name is too long");
373   assert(!memchr(Section.data(), '\0', Section.size()) &&
374          "section name cannot contain NUL");
375 
376   // Do the lookup, if we have a hit, return it.
377   auto R = MachOUniquingMap.try_emplace((Segment + Twine(',') + Section).str());
378   if (!R.second)
379     return R.first->second;
380 
381   MCSymbol *Begin = nullptr;
382   if (BeginSymName)
383     Begin = createTempSymbol(BeginSymName, false);
384 
385   // Otherwise, return a new section.
386   StringRef Name = R.first->first();
387   R.first->second = new (MachOAllocator.Allocate())
388       MCSectionMachO(Segment, Name.substr(Name.size() - Section.size()),
389                      TypeAndAttributes, Reserved2, Kind, Begin);
390   return R.first->second;
391 }
392 
393 void MCContext::renameELFSection(MCSectionELF *Section, StringRef Name) {
394   StringRef GroupName;
395   if (const MCSymbol *Group = Section->getGroup())
396     GroupName = Group->getName();
397 
398   // This function is only used by .debug*, which should not have the
399   // SHF_LINK_ORDER flag.
400   unsigned UniqueID = Section->getUniqueID();
401   ELFUniquingMap.erase(
402       ELFSectionKey{Section->getName(), GroupName, "", UniqueID});
403   auto I = ELFUniquingMap
404                .insert(std::make_pair(
405                    ELFSectionKey{Name, GroupName, "", UniqueID}, Section))
406                .first;
407   StringRef CachedName = I->first.SectionName;
408   const_cast<MCSectionELF *>(Section)->setSectionName(CachedName);
409 }
410 
411 MCSectionELF *MCContext::createELFSectionImpl(StringRef Section, unsigned Type,
412                                               unsigned Flags, SectionKind K,
413                                               unsigned EntrySize,
414                                               const MCSymbolELF *Group,
415                                               unsigned UniqueID,
416                                               const MCSymbolELF *LinkedToSym) {
417   MCSymbolELF *R;
418   MCSymbol *&Sym = Symbols[Section];
419   // A section symbol can not redefine regular symbols. There may be multiple
420   // sections with the same name, in which case the first such section wins.
421   if (Sym && Sym->isDefined() &&
422       (!Sym->isInSection() || Sym->getSection().getBeginSymbol() != Sym))
423     reportError(SMLoc(), "invalid symbol redefinition");
424   if (Sym && Sym->isUndefined()) {
425     R = cast<MCSymbolELF>(Sym);
426   } else {
427     auto NameIter = UsedNames.insert(std::make_pair(Section, false)).first;
428     R = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
429     if (!Sym)
430       Sym = R;
431   }
432   R->setBinding(ELF::STB_LOCAL);
433   R->setType(ELF::STT_SECTION);
434 
435   auto *Ret = new (ELFAllocator.Allocate()) MCSectionELF(
436       Section, Type, Flags, K, EntrySize, Group, UniqueID, R, LinkedToSym);
437 
438   auto *F = new MCDataFragment();
439   Ret->getFragmentList().insert(Ret->begin(), F);
440   F->setParent(Ret);
441   R->setFragment(F);
442 
443   return Ret;
444 }
445 
446 MCSectionELF *MCContext::createELFRelSection(const Twine &Name, unsigned Type,
447                                              unsigned Flags, unsigned EntrySize,
448                                              const MCSymbolELF *Group,
449                                              const MCSectionELF *RelInfoSection) {
450   StringMap<bool>::iterator I;
451   bool Inserted;
452   std::tie(I, Inserted) =
453       RelSecNames.insert(std::make_pair(Name.str(), true));
454 
455   return createELFSectionImpl(
456       I->getKey(), Type, Flags, SectionKind::getReadOnly(), EntrySize, Group,
457       true, cast<MCSymbolELF>(RelInfoSection->getBeginSymbol()));
458 }
459 
460 MCSectionELF *MCContext::getELFNamedSection(const Twine &Prefix,
461                                             const Twine &Suffix, unsigned Type,
462                                             unsigned Flags,
463                                             unsigned EntrySize) {
464   return getELFSection(Prefix + "." + Suffix, Type, Flags, EntrySize, Suffix);
465 }
466 
467 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
468                                        unsigned Flags, unsigned EntrySize,
469                                        const Twine &Group, unsigned UniqueID,
470                                        const MCSymbolELF *LinkedToSym) {
471   MCSymbolELF *GroupSym = nullptr;
472   if (!Group.isTriviallyEmpty() && !Group.str().empty())
473     GroupSym = cast<MCSymbolELF>(getOrCreateSymbol(Group));
474 
475   return getELFSection(Section, Type, Flags, EntrySize, GroupSym, UniqueID,
476                        LinkedToSym);
477 }
478 
479 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
480                                        unsigned Flags, unsigned EntrySize,
481                                        const MCSymbolELF *GroupSym,
482                                        unsigned UniqueID,
483                                        const MCSymbolELF *LinkedToSym) {
484   StringRef Group = "";
485   if (GroupSym)
486     Group = GroupSym->getName();
487   assert(!(LinkedToSym && LinkedToSym->getName().empty()));
488   // Do the lookup, if we have a hit, return it.
489   auto IterBool = ELFUniquingMap.insert(std::make_pair(
490       ELFSectionKey{Section.str(), Group,
491                     LinkedToSym ? LinkedToSym->getName() : "", UniqueID},
492       nullptr));
493   auto &Entry = *IterBool.first;
494   if (!IterBool.second)
495     return Entry.second;
496 
497   StringRef CachedName = Entry.first.SectionName;
498 
499   SectionKind Kind;
500   if (Flags & ELF::SHF_ARM_PURECODE)
501     Kind = SectionKind::getExecuteOnly();
502   else if (Flags & ELF::SHF_EXECINSTR)
503     Kind = SectionKind::getText();
504   else
505     Kind = SectionKind::getReadOnly();
506 
507   MCSectionELF *Result =
508       createELFSectionImpl(CachedName, Type, Flags, Kind, EntrySize, GroupSym,
509                            UniqueID, LinkedToSym);
510   Entry.second = Result;
511 
512   recordELFMergeableSectionInfo(Result->getName(), Result->getFlags(),
513                                 Result->getUniqueID(), Result->getEntrySize());
514 
515   return Result;
516 }
517 
518 MCSectionELF *MCContext::createELFGroupSection(const MCSymbolELF *Group) {
519   return createELFSectionImpl(".group", ELF::SHT_GROUP, 0,
520                               SectionKind::getReadOnly(), 4, Group,
521                               MCSection::NonUniqueID, nullptr);
522 }
523 
524 void MCContext::recordELFMergeableSectionInfo(StringRef SectionName,
525                                               unsigned Flags, unsigned UniqueID,
526                                               unsigned EntrySize) {
527   bool IsMergeable = Flags & ELF::SHF_MERGE;
528   if (IsMergeable && (UniqueID == GenericSectionID))
529     ELFSeenGenericMergeableSections.insert(SectionName);
530 
531   // For mergeable sections or non-mergeable sections with a generic mergeable
532   // section name we enter their Unique ID into the ELFEntrySizeMap so that
533   // compatible globals can be assigned to the same section.
534   if (IsMergeable || isELFGenericMergeableSection(SectionName)) {
535     ELFEntrySizeMap.insert(std::make_pair(
536         ELFEntrySizeKey{SectionName, Flags, EntrySize}, UniqueID));
537   }
538 }
539 
540 bool MCContext::isELFImplicitMergeableSectionNamePrefix(StringRef SectionName) {
541   return SectionName.startswith(".rodata.str") ||
542          SectionName.startswith(".rodata.cst");
543 }
544 
545 bool MCContext::isELFGenericMergeableSection(StringRef SectionName) {
546   return isELFImplicitMergeableSectionNamePrefix(SectionName) ||
547          ELFSeenGenericMergeableSections.count(SectionName);
548 }
549 
550 Optional<unsigned> MCContext::getELFUniqueIDForEntsize(StringRef SectionName,
551                                                        unsigned Flags,
552                                                        unsigned EntrySize) {
553   auto I = ELFEntrySizeMap.find(
554       MCContext::ELFEntrySizeKey{SectionName, Flags, EntrySize});
555   return (I != ELFEntrySizeMap.end()) ? Optional<unsigned>(I->second) : None;
556 }
557 
558 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
559                                          unsigned Characteristics,
560                                          SectionKind Kind,
561                                          StringRef COMDATSymName, int Selection,
562                                          unsigned UniqueID,
563                                          const char *BeginSymName) {
564   MCSymbol *COMDATSymbol = nullptr;
565   if (!COMDATSymName.empty()) {
566     COMDATSymbol = getOrCreateSymbol(COMDATSymName);
567     COMDATSymName = COMDATSymbol->getName();
568   }
569 
570 
571   // Do the lookup, if we have a hit, return it.
572   COFFSectionKey T{Section, COMDATSymName, Selection, UniqueID};
573   auto IterBool = COFFUniquingMap.insert(std::make_pair(T, nullptr));
574   auto Iter = IterBool.first;
575   if (!IterBool.second)
576     return Iter->second;
577 
578   MCSymbol *Begin = nullptr;
579   if (BeginSymName)
580     Begin = createTempSymbol(BeginSymName, false);
581 
582   StringRef CachedName = Iter->first.SectionName;
583   MCSectionCOFF *Result = new (COFFAllocator.Allocate()) MCSectionCOFF(
584       CachedName, Characteristics, COMDATSymbol, Selection, Kind, Begin);
585 
586   Iter->second = Result;
587   return Result;
588 }
589 
590 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
591                                          unsigned Characteristics,
592                                          SectionKind Kind,
593                                          const char *BeginSymName) {
594   return getCOFFSection(Section, Characteristics, Kind, "", 0, GenericSectionID,
595                         BeginSymName);
596 }
597 
598 MCSectionCOFF *MCContext::getAssociativeCOFFSection(MCSectionCOFF *Sec,
599                                                     const MCSymbol *KeySym,
600                                                     unsigned UniqueID) {
601   // Return the normal section if we don't have to be associative or unique.
602   if (!KeySym && UniqueID == GenericSectionID)
603     return Sec;
604 
605   // If we have a key symbol, make an associative section with the same name and
606   // kind as the normal section.
607   unsigned Characteristics = Sec->getCharacteristics();
608   if (KeySym) {
609     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
610     return getCOFFSection(Sec->getName(), Characteristics, Sec->getKind(),
611                           KeySym->getName(),
612                           COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
613   }
614 
615   return getCOFFSection(Sec->getName(), Characteristics, Sec->getKind(), "", 0,
616                         UniqueID);
617 }
618 
619 MCSectionWasm *MCContext::getWasmSection(const Twine &Section, SectionKind K,
620                                          const Twine &Group, unsigned UniqueID,
621                                          const char *BeginSymName) {
622   MCSymbolWasm *GroupSym = nullptr;
623   if (!Group.isTriviallyEmpty() && !Group.str().empty()) {
624     GroupSym = cast<MCSymbolWasm>(getOrCreateSymbol(Group));
625     GroupSym->setComdat(true);
626   }
627 
628   return getWasmSection(Section, K, GroupSym, UniqueID, BeginSymName);
629 }
630 
631 MCSectionWasm *MCContext::getWasmSection(const Twine &Section, SectionKind Kind,
632                                          const MCSymbolWasm *GroupSym,
633                                          unsigned UniqueID,
634                                          const char *BeginSymName) {
635   StringRef Group = "";
636   if (GroupSym)
637     Group = GroupSym->getName();
638   // Do the lookup, if we have a hit, return it.
639   auto IterBool = WasmUniquingMap.insert(
640       std::make_pair(WasmSectionKey{Section.str(), Group, UniqueID}, nullptr));
641   auto &Entry = *IterBool.first;
642   if (!IterBool.second)
643     return Entry.second;
644 
645   StringRef CachedName = Entry.first.SectionName;
646 
647   MCSymbol *Begin = createSymbol(CachedName, false, false);
648   cast<MCSymbolWasm>(Begin)->setType(wasm::WASM_SYMBOL_TYPE_SECTION);
649 
650   MCSectionWasm *Result = new (WasmAllocator.Allocate())
651       MCSectionWasm(CachedName, Kind, GroupSym, UniqueID, Begin);
652   Entry.second = Result;
653 
654   auto *F = new MCDataFragment();
655   Result->getFragmentList().insert(Result->begin(), F);
656   F->setParent(Result);
657   Begin->setFragment(F);
658 
659   return Result;
660 }
661 
662 MCSectionXCOFF *MCContext::getXCOFFSection(StringRef Section,
663                                            XCOFF::StorageMappingClass SMC,
664                                            XCOFF::SymbolType Type,
665                                            SectionKind Kind,
666                                            const char *BeginSymName) {
667   // Do the lookup. If we have a hit, return it.
668   auto IterBool = XCOFFUniquingMap.insert(
669       std::make_pair(XCOFFSectionKey{Section.str(), SMC}, nullptr));
670   auto &Entry = *IterBool.first;
671   if (!IterBool.second)
672     return Entry.second;
673 
674   // Otherwise, return a new section.
675   StringRef CachedName = Entry.first.SectionName;
676   MCSymbolXCOFF *QualName = cast<MCSymbolXCOFF>(getOrCreateSymbol(
677       CachedName + "[" + XCOFF::getMappingClassString(SMC) + "]"));
678 
679   MCSymbol *Begin = nullptr;
680   if (BeginSymName)
681     Begin = createTempSymbol(BeginSymName, false);
682 
683   // QualName->getUnqualifiedName() and CachedName are the same except when
684   // CachedName contains invalid character(s) such as '$' for an XCOFF symbol.
685   MCSectionXCOFF *Result = new (XCOFFAllocator.Allocate())
686       MCSectionXCOFF(QualName->getUnqualifiedName(), SMC, Type, Kind, QualName,
687                      Begin, CachedName);
688   Entry.second = Result;
689 
690   auto *F = new MCDataFragment();
691   Result->getFragmentList().insert(Result->begin(), F);
692   F->setParent(Result);
693 
694   if (Begin)
695     Begin->setFragment(F);
696 
697   return Result;
698 }
699 
700 MCSubtargetInfo &MCContext::getSubtargetCopy(const MCSubtargetInfo &STI) {
701   return *new (MCSubtargetAllocator.Allocate()) MCSubtargetInfo(STI);
702 }
703 
704 void MCContext::addDebugPrefixMapEntry(const std::string &From,
705                                        const std::string &To) {
706   DebugPrefixMap.insert(std::make_pair(From, To));
707 }
708 
709 void MCContext::RemapDebugPaths() {
710   const auto &DebugPrefixMap = this->DebugPrefixMap;
711   if (DebugPrefixMap.empty())
712     return;
713 
714   const auto RemapDebugPath = [&DebugPrefixMap](std::string &Path) {
715     SmallString<256> P(Path);
716     for (const auto &Entry : DebugPrefixMap) {
717       if (llvm::sys::path::replace_path_prefix(P, Entry.first, Entry.second)) {
718         Path = P.str().str();
719         break;
720       }
721     }
722   };
723 
724   // Remap compilation directory.
725   std::string CompDir = std::string(CompilationDir.str());
726   RemapDebugPath(CompDir);
727   CompilationDir = CompDir;
728 
729   // Remap MCDwarfDirs in all compilation units.
730   for (auto &CUIDTablePair : MCDwarfLineTablesCUMap)
731     for (auto &Dir : CUIDTablePair.second.getMCDwarfDirs())
732       RemapDebugPath(Dir);
733 }
734 
735 //===----------------------------------------------------------------------===//
736 // Dwarf Management
737 //===----------------------------------------------------------------------===//
738 
739 void MCContext::setGenDwarfRootFile(StringRef InputFileName, StringRef Buffer) {
740   // MCDwarf needs the root file as well as the compilation directory.
741   // If we find a '.file 0' directive that will supersede these values.
742   Optional<MD5::MD5Result> Cksum;
743   if (getDwarfVersion() >= 5) {
744     MD5 Hash;
745     MD5::MD5Result Sum;
746     Hash.update(Buffer);
747     Hash.final(Sum);
748     Cksum = Sum;
749   }
750   // Canonicalize the root filename. It cannot be empty, and should not
751   // repeat the compilation dir.
752   // The MCContext ctor initializes MainFileName to the name associated with
753   // the SrcMgr's main file ID, which might be the same as InputFileName (and
754   // possibly include directory components).
755   // Or, MainFileName might have been overridden by a -main-file-name option,
756   // which is supposed to be just a base filename with no directory component.
757   // So, if the InputFileName and MainFileName are not equal, assume
758   // MainFileName is a substitute basename and replace the last component.
759   SmallString<1024> FileNameBuf = InputFileName;
760   if (FileNameBuf.empty() || FileNameBuf == "-")
761     FileNameBuf = "<stdin>";
762   if (!getMainFileName().empty() && FileNameBuf != getMainFileName()) {
763     llvm::sys::path::remove_filename(FileNameBuf);
764     llvm::sys::path::append(FileNameBuf, getMainFileName());
765   }
766   StringRef FileName = FileNameBuf;
767   if (FileName.consume_front(getCompilationDir()))
768     if (llvm::sys::path::is_separator(FileName.front()))
769       FileName = FileName.drop_front();
770   assert(!FileName.empty());
771   setMCLineTableRootFile(
772       /*CUID=*/0, getCompilationDir(), FileName, Cksum, None);
773 }
774 
775 /// getDwarfFile - takes a file name and number to place in the dwarf file and
776 /// directory tables.  If the file number has already been allocated it is an
777 /// error and zero is returned and the client reports the error, else the
778 /// allocated file number is returned.  The file numbers may be in any order.
779 Expected<unsigned> MCContext::getDwarfFile(StringRef Directory,
780                                            StringRef FileName,
781                                            unsigned FileNumber,
782                                            Optional<MD5::MD5Result> Checksum,
783                                            Optional<StringRef> Source,
784                                            unsigned CUID) {
785   MCDwarfLineTable &Table = MCDwarfLineTablesCUMap[CUID];
786   return Table.tryGetFile(Directory, FileName, Checksum, Source, DwarfVersion,
787                           FileNumber);
788 }
789 
790 /// isValidDwarfFileNumber - takes a dwarf file number and returns true if it
791 /// currently is assigned and false otherwise.
792 bool MCContext::isValidDwarfFileNumber(unsigned FileNumber, unsigned CUID) {
793   const MCDwarfLineTable &LineTable = getMCDwarfLineTable(CUID);
794   if (FileNumber == 0)
795     return getDwarfVersion() >= 5;
796   if (FileNumber >= LineTable.getMCDwarfFiles().size())
797     return false;
798 
799   return !LineTable.getMCDwarfFiles()[FileNumber].Name.empty();
800 }
801 
802 /// Remove empty sections from SectionsForRanges, to avoid generating
803 /// useless debug info for them.
804 void MCContext::finalizeDwarfSections(MCStreamer &MCOS) {
805   SectionsForRanges.remove_if(
806       [&](MCSection *Sec) { return !MCOS.mayHaveInstructions(*Sec); });
807 }
808 
809 CodeViewContext &MCContext::getCVContext() {
810   if (!CVContext.get())
811     CVContext.reset(new CodeViewContext);
812   return *CVContext.get();
813 }
814 
815 //===----------------------------------------------------------------------===//
816 // Error Reporting
817 //===----------------------------------------------------------------------===//
818 
819 void MCContext::reportError(SMLoc Loc, const Twine &Msg) {
820   HadError = true;
821 
822   // If we have a source manager use it. Otherwise, try using the inline source
823   // manager.
824   // If that fails, use the generic report_fatal_error().
825   if (SrcMgr)
826     SrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
827   else if (InlineSrcMgr)
828     InlineSrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
829   else
830     report_fatal_error(Msg, false);
831 }
832 
833 void MCContext::reportWarning(SMLoc Loc, const Twine &Msg) {
834   if (TargetOptions && TargetOptions->MCNoWarn)
835     return;
836   if (TargetOptions && TargetOptions->MCFatalWarnings)
837     reportError(Loc, Msg);
838   else {
839     // If we have a source manager use it. Otherwise, try using the inline
840     // source manager.
841     if (SrcMgr)
842       SrcMgr->PrintMessage(Loc, SourceMgr::DK_Warning, Msg);
843     else if (InlineSrcMgr)
844       InlineSrcMgr->PrintMessage(Loc, SourceMgr::DK_Warning, Msg);
845   }
846 }
847 
848 void MCContext::reportFatalError(SMLoc Loc, const Twine &Msg) {
849   reportError(Loc, Msg);
850 
851   // If we reached here, we are failing ungracefully. Run the interrupt handlers
852   // to make sure any special cleanups get done, in particular that we remove
853   // files registered with RemoveFileOnSignal.
854   sys::RunInterruptHandlers();
855   exit(1);
856 }
857