xref: /llvm-project/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (revision 99f479abcf2c9b36daad04eb91cd0aafa659bb1d) 
1 //===- llvm/CodeGen/TargetLoweringObjectFileImpl.cpp - Object File Info ---===//
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 // This file implements classes used to handle lowerings specific to common
11 // object file formats.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
16 #include "llvm/ADT/SmallString.h"
17 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/ADT/StringExtras.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/ADT/Triple.h"
21 #include "llvm/BinaryFormat/COFF.h"
22 #include "llvm/BinaryFormat/Dwarf.h"
23 #include "llvm/BinaryFormat/ELF.h"
24 #include "llvm/BinaryFormat/MachO.h"
25 #include "llvm/CodeGen/MachineModuleInfo.h"
26 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
27 #include "llvm/IR/Comdat.h"
28 #include "llvm/IR/Constants.h"
29 #include "llvm/IR/DataLayout.h"
30 #include "llvm/IR/DerivedTypes.h"
31 #include "llvm/IR/Function.h"
32 #include "llvm/IR/GlobalAlias.h"
33 #include "llvm/IR/GlobalObject.h"
34 #include "llvm/IR/GlobalValue.h"
35 #include "llvm/IR/GlobalVariable.h"
36 #include "llvm/IR/Mangler.h"
37 #include "llvm/IR/Metadata.h"
38 #include "llvm/IR/Module.h"
39 #include "llvm/IR/Type.h"
40 #include "llvm/MC/MCAsmInfo.h"
41 #include "llvm/MC/MCContext.h"
42 #include "llvm/MC/MCExpr.h"
43 #include "llvm/MC/MCSectionCOFF.h"
44 #include "llvm/MC/MCSectionELF.h"
45 #include "llvm/MC/MCSectionMachO.h"
46 #include "llvm/MC/MCSectionWasm.h"
47 #include "llvm/MC/MCStreamer.h"
48 #include "llvm/MC/MCSymbol.h"
49 #include "llvm/MC/MCSymbolELF.h"
50 #include "llvm/MC/MCValue.h"
51 #include "llvm/MC/SectionKind.h"
52 #include "llvm/ProfileData/InstrProf.h"
53 #include "llvm/Support/Casting.h"
54 #include "llvm/Support/CodeGen.h"
55 #include "llvm/Support/Format.h"
56 #include "llvm/Support/ErrorHandling.h"
57 #include "llvm/Support/raw_ostream.h"
58 #include "llvm/Target/TargetMachine.h"
59 #include <cassert>
60 #include <string>
61 
62 using namespace llvm;
63 using namespace dwarf;
64 
65 static void GetObjCImageInfo(Module &M, unsigned &Version, unsigned &Flags,
66                              StringRef &Section) {
67   SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
68   M.getModuleFlagsMetadata(ModuleFlags);
69 
70   for (const auto &MFE: ModuleFlags) {
71     // Ignore flags with 'Require' behaviour.
72     if (MFE.Behavior == Module::Require)
73       continue;
74 
75     StringRef Key = MFE.Key->getString();
76     if (Key == "Objective-C Image Info Version") {
77       Version = mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
78     } else if (Key == "Objective-C Garbage Collection" ||
79                Key == "Objective-C GC Only" ||
80                Key == "Objective-C Is Simulated" ||
81                Key == "Objective-C Class Properties" ||
82                Key == "Objective-C Image Swift Version") {
83       Flags |= mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
84     } else if (Key == "Objective-C Image Info Section") {
85       Section = cast<MDString>(MFE.Val)->getString();
86     }
87   }
88 }
89 
90 //===----------------------------------------------------------------------===//
91 //                                  ELF
92 //===----------------------------------------------------------------------===//
93 
94 void TargetLoweringObjectFileELF::emitModuleMetadata(
95     MCStreamer &Streamer, Module &M, const TargetMachine &TM) const {
96   unsigned Version = 0;
97   unsigned Flags = 0;
98   StringRef Section;
99 
100   GetObjCImageInfo(M, Version, Flags, Section);
101   if (Section.empty())
102     return;
103 
104   auto &C = getContext();
105   auto *S = C.getELFSection(Section, ELF::SHT_PROGBITS, ELF::SHF_ALLOC);
106   Streamer.SwitchSection(S);
107   Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
108   Streamer.EmitIntValue(Version, 4);
109   Streamer.EmitIntValue(Flags, 4);
110   Streamer.AddBlankLine();
111 }
112 
113 MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
114     const GlobalValue *GV, const TargetMachine &TM,
115     MachineModuleInfo *MMI) const {
116   unsigned Encoding = getPersonalityEncoding();
117   if ((Encoding & 0x80) == DW_EH_PE_indirect)
118     return getContext().getOrCreateSymbol(StringRef("DW.ref.") +
119                                           TM.getSymbol(GV)->getName());
120   if ((Encoding & 0x70) == DW_EH_PE_absptr)
121     return TM.getSymbol(GV);
122   report_fatal_error("We do not support this DWARF encoding yet!");
123 }
124 
125 void TargetLoweringObjectFileELF::emitPersonalityValue(
126     MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
127   SmallString<64> NameData("DW.ref.");
128   NameData += Sym->getName();
129   MCSymbolELF *Label =
130       cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
131   Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
132   Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
133   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
134   MCSection *Sec = getContext().getELFNamedSection(".data", Label->getName(),
135                                                    ELF::SHT_PROGBITS, Flags, 0);
136   unsigned Size = DL.getPointerSize();
137   Streamer.SwitchSection(Sec);
138   Streamer.EmitValueToAlignment(DL.getPointerABIAlignment(0));
139   Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
140   const MCExpr *E = MCConstantExpr::create(Size, getContext());
141   Streamer.emitELFSize(Label, E);
142   Streamer.EmitLabel(Label);
143 
144   Streamer.EmitSymbolValue(Sym, Size);
145 }
146 
147 const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
148     const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
149     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
150   if (Encoding & DW_EH_PE_indirect) {
151     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
152 
153     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", TM);
154 
155     // Add information about the stub reference to ELFMMI so that the stub
156     // gets emitted by the asmprinter.
157     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
158     if (!StubSym.getPointer()) {
159       MCSymbol *Sym = TM.getSymbol(GV);
160       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
161     }
162 
163     return TargetLoweringObjectFile::
164       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
165                         Encoding & ~DW_EH_PE_indirect, Streamer);
166   }
167 
168   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
169                                                            MMI, Streamer);
170 }
171 
172 static SectionKind getELFKindForNamedSection(StringRef Name, SectionKind K) {
173   // N.B.: The defaults used in here are no the same ones used in MC.
174   // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
175   // both gas and MC will produce a section with no flags. Given
176   // section(".eh_frame") gcc will produce:
177   //
178   //   .section   .eh_frame,"a",@progbits
179 
180   if (Name == getInstrProfSectionName(IPSK_covmap, Triple::ELF,
181                                       /*AddSegmentInfo=*/false))
182     return SectionKind::getMetadata();
183 
184   if (Name.empty() || Name[0] != '.') return K;
185 
186   // Some lame default implementation based on some magic section names.
187   if (Name == ".bss" ||
188       Name.startswith(".bss.") ||
189       Name.startswith(".gnu.linkonce.b.") ||
190       Name.startswith(".llvm.linkonce.b.") ||
191       Name == ".sbss" ||
192       Name.startswith(".sbss.") ||
193       Name.startswith(".gnu.linkonce.sb.") ||
194       Name.startswith(".llvm.linkonce.sb."))
195     return SectionKind::getBSS();
196 
197   if (Name == ".tdata" ||
198       Name.startswith(".tdata.") ||
199       Name.startswith(".gnu.linkonce.td.") ||
200       Name.startswith(".llvm.linkonce.td."))
201     return SectionKind::getThreadData();
202 
203   if (Name == ".tbss" ||
204       Name.startswith(".tbss.") ||
205       Name.startswith(".gnu.linkonce.tb.") ||
206       Name.startswith(".llvm.linkonce.tb."))
207     return SectionKind::getThreadBSS();
208 
209   return K;
210 }
211 
212 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
213   // Use SHT_NOTE for section whose name starts with ".note" to allow
214   // emitting ELF notes from C variable declaration.
215   // See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77609
216   if (Name.startswith(".note"))
217     return ELF::SHT_NOTE;
218 
219   if (Name == ".init_array")
220     return ELF::SHT_INIT_ARRAY;
221 
222   if (Name == ".fini_array")
223     return ELF::SHT_FINI_ARRAY;
224 
225   if (Name == ".preinit_array")
226     return ELF::SHT_PREINIT_ARRAY;
227 
228   if (K.isBSS() || K.isThreadBSS())
229     return ELF::SHT_NOBITS;
230 
231   return ELF::SHT_PROGBITS;
232 }
233 
234 static unsigned getELFSectionFlags(SectionKind K) {
235   unsigned Flags = 0;
236 
237   if (!K.isMetadata())
238     Flags |= ELF::SHF_ALLOC;
239 
240   if (K.isText())
241     Flags |= ELF::SHF_EXECINSTR;
242 
243   if (K.isExecuteOnly())
244     Flags |= ELF::SHF_ARM_PURECODE;
245 
246   if (K.isWriteable())
247     Flags |= ELF::SHF_WRITE;
248 
249   if (K.isThreadLocal())
250     Flags |= ELF::SHF_TLS;
251 
252   if (K.isMergeableCString() || K.isMergeableConst())
253     Flags |= ELF::SHF_MERGE;
254 
255   if (K.isMergeableCString())
256     Flags |= ELF::SHF_STRINGS;
257 
258   return Flags;
259 }
260 
261 static const Comdat *getELFComdat(const GlobalValue *GV) {
262   const Comdat *C = GV->getComdat();
263   if (!C)
264     return nullptr;
265 
266   if (C->getSelectionKind() != Comdat::Any)
267     report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
268                        C->getName() + "' cannot be lowered.");
269 
270   return C;
271 }
272 
273 static const MCSymbolELF *getAssociatedSymbol(const GlobalObject *GO,
274                                               const TargetMachine &TM) {
275   MDNode *MD = GO->getMetadata(LLVMContext::MD_associated);
276   if (!MD)
277     return nullptr;
278 
279   const MDOperand &Op = MD->getOperand(0);
280   if (!Op.get())
281     return nullptr;
282 
283   auto *VM = dyn_cast<ValueAsMetadata>(Op);
284   if (!VM)
285     report_fatal_error("MD_associated operand is not ValueAsMetadata");
286 
287   GlobalObject *OtherGO = dyn_cast<GlobalObject>(VM->getValue());
288   return OtherGO ? dyn_cast<MCSymbolELF>(TM.getSymbol(OtherGO)) : nullptr;
289 }
290 
291 MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
292     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
293   StringRef SectionName = GO->getSection();
294 
295   // Check if '#pragma clang section' name is applicable.
296   // Note that pragma directive overrides -ffunction-section, -fdata-section
297   // and so section name is exactly as user specified and not uniqued.
298   const GlobalVariable *GV = dyn_cast<GlobalVariable>(GO);
299   if (GV && GV->hasImplicitSection()) {
300     auto Attrs = GV->getAttributes();
301     if (Attrs.hasAttribute("bss-section") && Kind.isBSS()) {
302       SectionName = Attrs.getAttribute("bss-section").getValueAsString();
303     } else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()) {
304       SectionName = Attrs.getAttribute("rodata-section").getValueAsString();
305     } else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
306       SectionName = Attrs.getAttribute("data-section").getValueAsString();
307     }
308   }
309   const Function *F = dyn_cast<Function>(GO);
310   if (F && F->hasFnAttribute("implicit-section-name")) {
311     SectionName = F->getFnAttribute("implicit-section-name").getValueAsString();
312   }
313 
314   // Infer section flags from the section name if we can.
315   Kind = getELFKindForNamedSection(SectionName, Kind);
316 
317   StringRef Group = "";
318   unsigned Flags = getELFSectionFlags(Kind);
319   if (const Comdat *C = getELFComdat(GO)) {
320     Group = C->getName();
321     Flags |= ELF::SHF_GROUP;
322   }
323 
324   // A section can have at most one associated section. Put each global with
325   // MD_associated in a unique section.
326   unsigned UniqueID = MCContext::GenericSectionID;
327   const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
328   if (AssociatedSymbol) {
329     UniqueID = NextUniqueID++;
330     Flags |= ELF::SHF_LINK_ORDER;
331   }
332 
333   MCSectionELF *Section = getContext().getELFSection(
334       SectionName, getELFSectionType(SectionName, Kind), Flags,
335       /*EntrySize=*/0, Group, UniqueID, AssociatedSymbol);
336   // Make sure that we did not get some other section with incompatible sh_link.
337   // This should not be possible due to UniqueID code above.
338   assert(Section->getAssociatedSymbol() == AssociatedSymbol);
339   return Section;
340 }
341 
342 /// Return the section prefix name used by options FunctionsSections and
343 /// DataSections.
344 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
345   if (Kind.isText())
346     return ".text";
347   if (Kind.isReadOnly())
348     return ".rodata";
349   if (Kind.isBSS())
350     return ".bss";
351   if (Kind.isThreadData())
352     return ".tdata";
353   if (Kind.isThreadBSS())
354     return ".tbss";
355   if (Kind.isData())
356     return ".data";
357   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
358   return ".data.rel.ro";
359 }
360 
361 static MCSectionELF *selectELFSectionForGlobal(
362     MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
363     const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
364     unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol) {
365   unsigned EntrySize = 0;
366   if (Kind.isMergeableCString()) {
367     if (Kind.isMergeable2ByteCString()) {
368       EntrySize = 2;
369     } else if (Kind.isMergeable4ByteCString()) {
370       EntrySize = 4;
371     } else {
372       EntrySize = 1;
373       assert(Kind.isMergeable1ByteCString() && "unknown string width");
374     }
375   } else if (Kind.isMergeableConst()) {
376     if (Kind.isMergeableConst4()) {
377       EntrySize = 4;
378     } else if (Kind.isMergeableConst8()) {
379       EntrySize = 8;
380     } else if (Kind.isMergeableConst16()) {
381       EntrySize = 16;
382     } else {
383       assert(Kind.isMergeableConst32() && "unknown data width");
384       EntrySize = 32;
385     }
386   }
387 
388   StringRef Group = "";
389   if (const Comdat *C = getELFComdat(GO)) {
390     Flags |= ELF::SHF_GROUP;
391     Group = C->getName();
392   }
393 
394   bool UniqueSectionNames = TM.getUniqueSectionNames();
395   SmallString<128> Name;
396   if (Kind.isMergeableCString()) {
397     // We also need alignment here.
398     // FIXME: this is getting the alignment of the character, not the
399     // alignment of the global!
400     unsigned Align = GO->getParent()->getDataLayout().getPreferredAlignment(
401         cast<GlobalVariable>(GO));
402 
403     std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
404     Name = SizeSpec + utostr(Align);
405   } else if (Kind.isMergeableConst()) {
406     Name = ".rodata.cst";
407     Name += utostr(EntrySize);
408   } else {
409     Name = getSectionPrefixForGlobal(Kind);
410   }
411 
412   if (const auto *F = dyn_cast<Function>(GO)) {
413     const auto &OptionalPrefix = F->getSectionPrefix();
414     if (OptionalPrefix)
415       Name += *OptionalPrefix;
416   }
417 
418   if (EmitUniqueSection && UniqueSectionNames) {
419     Name.push_back('.');
420     TM.getNameWithPrefix(Name, GO, Mang, true);
421   }
422   unsigned UniqueID = MCContext::GenericSectionID;
423   if (EmitUniqueSection && !UniqueSectionNames) {
424     UniqueID = *NextUniqueID;
425     (*NextUniqueID)++;
426   }
427   // Use 0 as the unique ID for execute-only text
428   if (Kind.isExecuteOnly())
429     UniqueID = 0;
430   return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags,
431                            EntrySize, Group, UniqueID, AssociatedSymbol);
432 }
433 
434 MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
435     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
436   unsigned Flags = getELFSectionFlags(Kind);
437 
438   // If we have -ffunction-section or -fdata-section then we should emit the
439   // global value to a uniqued section specifically for it.
440   bool EmitUniqueSection = false;
441   if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
442     if (Kind.isText())
443       EmitUniqueSection = TM.getFunctionSections();
444     else
445       EmitUniqueSection = TM.getDataSections();
446   }
447   EmitUniqueSection |= GO->hasComdat();
448 
449   const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
450   if (AssociatedSymbol) {
451     EmitUniqueSection = true;
452     Flags |= ELF::SHF_LINK_ORDER;
453   }
454 
455   MCSectionELF *Section = selectELFSectionForGlobal(
456       getContext(), GO, Kind, getMangler(), TM, EmitUniqueSection, Flags,
457       &NextUniqueID, AssociatedSymbol);
458   assert(Section->getAssociatedSymbol() == AssociatedSymbol);
459   return Section;
460 }
461 
462 MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
463     const Function &F, const TargetMachine &TM) const {
464   // If the function can be removed, produce a unique section so that
465   // the table doesn't prevent the removal.
466   const Comdat *C = F.getComdat();
467   bool EmitUniqueSection = TM.getFunctionSections() || C;
468   if (!EmitUniqueSection)
469     return ReadOnlySection;
470 
471   return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
472                                    getMangler(), TM, EmitUniqueSection,
473                                    ELF::SHF_ALLOC, &NextUniqueID,
474                                    /* AssociatedSymbol */ nullptr);
475 }
476 
477 bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
478     bool UsesLabelDifference, const Function &F) const {
479   // We can always create relative relocations, so use another section
480   // that can be marked non-executable.
481   return false;
482 }
483 
484 /// Given a mergeable constant with the specified size and relocation
485 /// information, return a section that it should be placed in.
486 MCSection *TargetLoweringObjectFileELF::getSectionForConstant(
487     const DataLayout &DL, SectionKind Kind, const Constant *C,
488     unsigned &Align) const {
489   if (Kind.isMergeableConst4() && MergeableConst4Section)
490     return MergeableConst4Section;
491   if (Kind.isMergeableConst8() && MergeableConst8Section)
492     return MergeableConst8Section;
493   if (Kind.isMergeableConst16() && MergeableConst16Section)
494     return MergeableConst16Section;
495   if (Kind.isMergeableConst32() && MergeableConst32Section)
496     return MergeableConst32Section;
497   if (Kind.isReadOnly())
498     return ReadOnlySection;
499 
500   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
501   return DataRelROSection;
502 }
503 
504 static MCSectionELF *getStaticStructorSection(MCContext &Ctx, bool UseInitArray,
505                                               bool IsCtor, unsigned Priority,
506                                               const MCSymbol *KeySym) {
507   std::string Name;
508   unsigned Type;
509   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
510   StringRef COMDAT = KeySym ? KeySym->getName() : "";
511 
512   if (KeySym)
513     Flags |= ELF::SHF_GROUP;
514 
515   if (UseInitArray) {
516     if (IsCtor) {
517       Type = ELF::SHT_INIT_ARRAY;
518       Name = ".init_array";
519     } else {
520       Type = ELF::SHT_FINI_ARRAY;
521       Name = ".fini_array";
522     }
523     if (Priority != 65535) {
524       Name += '.';
525       Name += utostr(Priority);
526     }
527   } else {
528     // The default scheme is .ctor / .dtor, so we have to invert the priority
529     // numbering.
530     if (IsCtor)
531       Name = ".ctors";
532     else
533       Name = ".dtors";
534     if (Priority != 65535)
535       raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
536     Type = ELF::SHT_PROGBITS;
537   }
538 
539   return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
540 }
541 
542 MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
543     unsigned Priority, const MCSymbol *KeySym) const {
544   return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
545                                   KeySym);
546 }
547 
548 MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
549     unsigned Priority, const MCSymbol *KeySym) const {
550   return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
551                                   KeySym);
552 }
553 
554 const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
555     const GlobalValue *LHS, const GlobalValue *RHS,
556     const TargetMachine &TM) const {
557   // We may only use a PLT-relative relocation to refer to unnamed_addr
558   // functions.
559   if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
560     return nullptr;
561 
562   // Basic sanity checks.
563   if (LHS->getType()->getPointerAddressSpace() != 0 ||
564       RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
565       RHS->isThreadLocal())
566     return nullptr;
567 
568   return MCBinaryExpr::createSub(
569       MCSymbolRefExpr::create(TM.getSymbol(LHS), PLTRelativeVariantKind,
570                               getContext()),
571       MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
572 }
573 
574 void
575 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
576   UseInitArray = UseInitArray_;
577   MCContext &Ctx = getContext();
578   if (!UseInitArray) {
579     StaticCtorSection = Ctx.getELFSection(".ctors", ELF::SHT_PROGBITS,
580                                           ELF::SHF_ALLOC | ELF::SHF_WRITE);
581 
582     StaticDtorSection = Ctx.getELFSection(".dtors", ELF::SHT_PROGBITS,
583                                           ELF::SHF_ALLOC | ELF::SHF_WRITE);
584     return;
585   }
586 
587   StaticCtorSection = Ctx.getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
588                                         ELF::SHF_WRITE | ELF::SHF_ALLOC);
589   StaticDtorSection = Ctx.getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
590                                         ELF::SHF_WRITE | ELF::SHF_ALLOC);
591 }
592 
593 //===----------------------------------------------------------------------===//
594 //                                 MachO
595 //===----------------------------------------------------------------------===//
596 
597 TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
598   : TargetLoweringObjectFile() {
599   SupportIndirectSymViaGOTPCRel = true;
600 }
601 
602 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
603                                                const TargetMachine &TM) {
604   TargetLoweringObjectFile::Initialize(Ctx, TM);
605   if (TM.getRelocationModel() == Reloc::Static) {
606     StaticCtorSection = Ctx.getMachOSection("__TEXT", "__constructor", 0,
607                                             SectionKind::getData());
608     StaticDtorSection = Ctx.getMachOSection("__TEXT", "__destructor", 0,
609                                             SectionKind::getData());
610   } else {
611     StaticCtorSection = Ctx.getMachOSection("__DATA", "__mod_init_func",
612                                             MachO::S_MOD_INIT_FUNC_POINTERS,
613                                             SectionKind::getData());
614     StaticDtorSection = Ctx.getMachOSection("__DATA", "__mod_term_func",
615                                             MachO::S_MOD_TERM_FUNC_POINTERS,
616                                             SectionKind::getData());
617   }
618 }
619 
620 void TargetLoweringObjectFileMachO::emitModuleMetadata(
621     MCStreamer &Streamer, Module &M, const TargetMachine &TM) const {
622   // Emit the linker options if present.
623   if (auto *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
624     for (const auto &Option : LinkerOptions->operands()) {
625       SmallVector<std::string, 4> StrOptions;
626       for (const auto &Piece : cast<MDNode>(Option)->operands())
627         StrOptions.push_back(cast<MDString>(Piece)->getString());
628       Streamer.EmitLinkerOptions(StrOptions);
629     }
630   }
631 
632   unsigned VersionVal = 0;
633   unsigned ImageInfoFlags = 0;
634   StringRef SectionVal;
635 
636   GetObjCImageInfo(M, VersionVal, ImageInfoFlags, SectionVal);
637 
638   // The section is mandatory. If we don't have it, then we don't have GC info.
639   if (SectionVal.empty())
640     return;
641 
642   StringRef Segment, Section;
643   unsigned TAA = 0, StubSize = 0;
644   bool TAAParsed;
645   std::string ErrorCode =
646     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
647                                           TAA, TAAParsed, StubSize);
648   if (!ErrorCode.empty())
649     // If invalid, report the error with report_fatal_error.
650     report_fatal_error("Invalid section specifier '" + Section + "': " +
651                        ErrorCode + ".");
652 
653   // Get the section.
654   MCSectionMachO *S = getContext().getMachOSection(
655       Segment, Section, TAA, StubSize, SectionKind::getData());
656   Streamer.SwitchSection(S);
657   Streamer.EmitLabel(getContext().
658                      getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
659   Streamer.EmitIntValue(VersionVal, 4);
660   Streamer.EmitIntValue(ImageInfoFlags, 4);
661   Streamer.AddBlankLine();
662 }
663 
664 static void checkMachOComdat(const GlobalValue *GV) {
665   const Comdat *C = GV->getComdat();
666   if (!C)
667     return;
668 
669   report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
670                      "' cannot be lowered.");
671 }
672 
673 MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
674     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
675   // Parse the section specifier and create it if valid.
676   StringRef Segment, Section;
677   unsigned TAA = 0, StubSize = 0;
678   bool TAAParsed;
679 
680   checkMachOComdat(GO);
681 
682   std::string ErrorCode =
683     MCSectionMachO::ParseSectionSpecifier(GO->getSection(), Segment, Section,
684                                           TAA, TAAParsed, StubSize);
685   if (!ErrorCode.empty()) {
686     // If invalid, report the error with report_fatal_error.
687     report_fatal_error("Global variable '" + GO->getName() +
688                        "' has an invalid section specifier '" +
689                        GO->getSection() + "': " + ErrorCode + ".");
690   }
691 
692   // Get the section.
693   MCSectionMachO *S =
694       getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
695 
696   // If TAA wasn't set by ParseSectionSpecifier() above,
697   // use the value returned by getMachOSection() as a default.
698   if (!TAAParsed)
699     TAA = S->getTypeAndAttributes();
700 
701   // Okay, now that we got the section, verify that the TAA & StubSize agree.
702   // If the user declared multiple globals with different section flags, we need
703   // to reject it here.
704   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
705     // If invalid, report the error with report_fatal_error.
706     report_fatal_error("Global variable '" + GO->getName() +
707                        "' section type or attributes does not match previous"
708                        " section specifier");
709   }
710 
711   return S;
712 }
713 
714 MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
715     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
716   checkMachOComdat(GO);
717 
718   // Handle thread local data.
719   if (Kind.isThreadBSS()) return TLSBSSSection;
720   if (Kind.isThreadData()) return TLSDataSection;
721 
722   if (Kind.isText())
723     return GO->isWeakForLinker() ? TextCoalSection : TextSection;
724 
725   // If this is weak/linkonce, put this in a coalescable section, either in text
726   // or data depending on if it is writable.
727   if (GO->isWeakForLinker()) {
728     if (Kind.isReadOnly())
729       return ConstTextCoalSection;
730     return DataCoalSection;
731   }
732 
733   // FIXME: Alignment check should be handled by section classifier.
734   if (Kind.isMergeable1ByteCString() &&
735       GO->getParent()->getDataLayout().getPreferredAlignment(
736           cast<GlobalVariable>(GO)) < 32)
737     return CStringSection;
738 
739   // Do not put 16-bit arrays in the UString section if they have an
740   // externally visible label, this runs into issues with certain linker
741   // versions.
742   if (Kind.isMergeable2ByteCString() && !GO->hasExternalLinkage() &&
743       GO->getParent()->getDataLayout().getPreferredAlignment(
744           cast<GlobalVariable>(GO)) < 32)
745     return UStringSection;
746 
747   // With MachO only variables whose corresponding symbol starts with 'l' or
748   // 'L' can be merged, so we only try merging GVs with private linkage.
749   if (GO->hasPrivateLinkage() && Kind.isMergeableConst()) {
750     if (Kind.isMergeableConst4())
751       return FourByteConstantSection;
752     if (Kind.isMergeableConst8())
753       return EightByteConstantSection;
754     if (Kind.isMergeableConst16())
755       return SixteenByteConstantSection;
756   }
757 
758   // Otherwise, if it is readonly, but not something we can specially optimize,
759   // just drop it in .const.
760   if (Kind.isReadOnly())
761     return ReadOnlySection;
762 
763   // If this is marked const, put it into a const section.  But if the dynamic
764   // linker needs to write to it, put it in the data segment.
765   if (Kind.isReadOnlyWithRel())
766     return ConstDataSection;
767 
768   // Put zero initialized globals with strong external linkage in the
769   // DATA, __common section with the .zerofill directive.
770   if (Kind.isBSSExtern())
771     return DataCommonSection;
772 
773   // Put zero initialized globals with local linkage in __DATA,__bss directive
774   // with the .zerofill directive (aka .lcomm).
775   if (Kind.isBSSLocal())
776     return DataBSSSection;
777 
778   // Otherwise, just drop the variable in the normal data section.
779   return DataSection;
780 }
781 
782 MCSection *TargetLoweringObjectFileMachO::getSectionForConstant(
783     const DataLayout &DL, SectionKind Kind, const Constant *C,
784     unsigned &Align) const {
785   // If this constant requires a relocation, we have to put it in the data
786   // segment, not in the text segment.
787   if (Kind.isData() || Kind.isReadOnlyWithRel())
788     return ConstDataSection;
789 
790   if (Kind.isMergeableConst4())
791     return FourByteConstantSection;
792   if (Kind.isMergeableConst8())
793     return EightByteConstantSection;
794   if (Kind.isMergeableConst16())
795     return SixteenByteConstantSection;
796   return ReadOnlySection;  // .const
797 }
798 
799 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
800     const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
801     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
802   // The mach-o version of this method defaults to returning a stub reference.
803 
804   if (Encoding & DW_EH_PE_indirect) {
805     MachineModuleInfoMachO &MachOMMI =
806       MMI->getObjFileInfo<MachineModuleInfoMachO>();
807 
808     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
809 
810     // Add information about the stub reference to MachOMMI so that the stub
811     // gets emitted by the asmprinter.
812     MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
813     if (!StubSym.getPointer()) {
814       MCSymbol *Sym = TM.getSymbol(GV);
815       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
816     }
817 
818     return TargetLoweringObjectFile::
819       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
820                         Encoding & ~DW_EH_PE_indirect, Streamer);
821   }
822 
823   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
824                                                            MMI, Streamer);
825 }
826 
827 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
828     const GlobalValue *GV, const TargetMachine &TM,
829     MachineModuleInfo *MMI) const {
830   // The mach-o version of this method defaults to returning a stub reference.
831   MachineModuleInfoMachO &MachOMMI =
832     MMI->getObjFileInfo<MachineModuleInfoMachO>();
833 
834   MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
835 
836   // Add information about the stub reference to MachOMMI so that the stub
837   // gets emitted by the asmprinter.
838   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
839   if (!StubSym.getPointer()) {
840     MCSymbol *Sym = TM.getSymbol(GV);
841     StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
842   }
843 
844   return SSym;
845 }
846 
847 const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
848     const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
849     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
850   // Although MachO 32-bit targets do not explicitly have a GOTPCREL relocation
851   // as 64-bit do, we replace the GOT equivalent by accessing the final symbol
852   // through a non_lazy_ptr stub instead. One advantage is that it allows the
853   // computation of deltas to final external symbols. Example:
854   //
855   //    _extgotequiv:
856   //       .long   _extfoo
857   //
858   //    _delta:
859   //       .long   _extgotequiv-_delta
860   //
861   // is transformed to:
862   //
863   //    _delta:
864   //       .long   L_extfoo$non_lazy_ptr-(_delta+0)
865   //
866   //       .section        __IMPORT,__pointers,non_lazy_symbol_pointers
867   //    L_extfoo$non_lazy_ptr:
868   //       .indirect_symbol        _extfoo
869   //       .long   0
870   //
871   MachineModuleInfoMachO &MachOMMI =
872     MMI->getObjFileInfo<MachineModuleInfoMachO>();
873   MCContext &Ctx = getContext();
874 
875   // The offset must consider the original displacement from the base symbol
876   // since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
877   Offset = -MV.getConstant();
878   const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
879 
880   // Access the final symbol via sym$non_lazy_ptr and generate the appropriated
881   // non_lazy_ptr stubs.
882   SmallString<128> Name;
883   StringRef Suffix = "$non_lazy_ptr";
884   Name += MMI->getModule()->getDataLayout().getPrivateGlobalPrefix();
885   Name += Sym->getName();
886   Name += Suffix;
887   MCSymbol *Stub = Ctx.getOrCreateSymbol(Name);
888 
889   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
890   if (!StubSym.getPointer())
891     StubSym = MachineModuleInfoImpl::
892       StubValueTy(const_cast<MCSymbol *>(Sym), true /* access indirectly */);
893 
894   const MCExpr *BSymExpr =
895     MCSymbolRefExpr::create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
896   const MCExpr *LHS =
897     MCSymbolRefExpr::create(Stub, MCSymbolRefExpr::VK_None, Ctx);
898 
899   if (!Offset)
900     return MCBinaryExpr::createSub(LHS, BSymExpr, Ctx);
901 
902   const MCExpr *RHS =
903     MCBinaryExpr::createAdd(BSymExpr, MCConstantExpr::create(Offset, Ctx), Ctx);
904   return MCBinaryExpr::createSub(LHS, RHS, Ctx);
905 }
906 
907 static bool canUsePrivateLabel(const MCAsmInfo &AsmInfo,
908                                const MCSection &Section) {
909   if (!AsmInfo.isSectionAtomizableBySymbols(Section))
910     return true;
911 
912   // If it is not dead stripped, it is safe to use private labels.
913   const MCSectionMachO &SMO = cast<MCSectionMachO>(Section);
914   if (SMO.hasAttribute(MachO::S_ATTR_NO_DEAD_STRIP))
915     return true;
916 
917   return false;
918 }
919 
920 void TargetLoweringObjectFileMachO::getNameWithPrefix(
921     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
922     const TargetMachine &TM) const {
923   bool CannotUsePrivateLabel = true;
924   if (auto *GO = GV->getBaseObject()) {
925     SectionKind GOKind = TargetLoweringObjectFile::getKindForGlobal(GO, TM);
926     const MCSection *TheSection = SectionForGlobal(GO, GOKind, TM);
927     CannotUsePrivateLabel =
928         !canUsePrivateLabel(*TM.getMCAsmInfo(), *TheSection);
929   }
930   getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
931 }
932 
933 //===----------------------------------------------------------------------===//
934 //                                  COFF
935 //===----------------------------------------------------------------------===//
936 
937 static unsigned
938 getCOFFSectionFlags(SectionKind K, const TargetMachine &TM) {
939   unsigned Flags = 0;
940   bool isThumb = TM.getTargetTriple().getArch() == Triple::thumb;
941 
942   if (K.isMetadata())
943     Flags |=
944       COFF::IMAGE_SCN_MEM_DISCARDABLE;
945   else if (K.isText())
946     Flags |=
947       COFF::IMAGE_SCN_MEM_EXECUTE |
948       COFF::IMAGE_SCN_MEM_READ |
949       COFF::IMAGE_SCN_CNT_CODE |
950       (isThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0);
951   else if (K.isBSS())
952     Flags |=
953       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
954       COFF::IMAGE_SCN_MEM_READ |
955       COFF::IMAGE_SCN_MEM_WRITE;
956   else if (K.isThreadLocal())
957     Flags |=
958       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
959       COFF::IMAGE_SCN_MEM_READ |
960       COFF::IMAGE_SCN_MEM_WRITE;
961   else if (K.isReadOnly() || K.isReadOnlyWithRel())
962     Flags |=
963       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
964       COFF::IMAGE_SCN_MEM_READ;
965   else if (K.isWriteable())
966     Flags |=
967       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
968       COFF::IMAGE_SCN_MEM_READ |
969       COFF::IMAGE_SCN_MEM_WRITE;
970 
971   return Flags;
972 }
973 
974 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
975   const Comdat *C = GV->getComdat();
976   assert(C && "expected GV to have a Comdat!");
977 
978   StringRef ComdatGVName = C->getName();
979   const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
980   if (!ComdatGV)
981     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
982                        "' does not exist.");
983 
984   if (ComdatGV->getComdat() != C)
985     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
986                        "' is not a key for its COMDAT.");
987 
988   return ComdatGV;
989 }
990 
991 static int getSelectionForCOFF(const GlobalValue *GV) {
992   if (const Comdat *C = GV->getComdat()) {
993     const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
994     if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
995       ComdatKey = GA->getBaseObject();
996     if (ComdatKey == GV) {
997       switch (C->getSelectionKind()) {
998       case Comdat::Any:
999         return COFF::IMAGE_COMDAT_SELECT_ANY;
1000       case Comdat::ExactMatch:
1001         return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
1002       case Comdat::Largest:
1003         return COFF::IMAGE_COMDAT_SELECT_LARGEST;
1004       case Comdat::NoDuplicates:
1005         return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1006       case Comdat::SameSize:
1007         return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
1008       }
1009     } else {
1010       return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
1011     }
1012   }
1013   return 0;
1014 }
1015 
1016 MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
1017     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1018   int Selection = 0;
1019   unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1020   StringRef Name = GO->getSection();
1021   StringRef COMDATSymName = "";
1022   if (GO->hasComdat()) {
1023     Selection = getSelectionForCOFF(GO);
1024     const GlobalValue *ComdatGV;
1025     if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
1026       ComdatGV = getComdatGVForCOFF(GO);
1027     else
1028       ComdatGV = GO;
1029 
1030     if (!ComdatGV->hasPrivateLinkage()) {
1031       MCSymbol *Sym = TM.getSymbol(ComdatGV);
1032       COMDATSymName = Sym->getName();
1033       Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1034     } else {
1035       Selection = 0;
1036     }
1037   }
1038 
1039   return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
1040                                      Selection);
1041 }
1042 
1043 static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
1044   if (Kind.isText())
1045     return ".text";
1046   if (Kind.isBSS())
1047     return ".bss";
1048   if (Kind.isThreadLocal())
1049     return ".tls$";
1050   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1051     return ".rdata";
1052   return ".data";
1053 }
1054 
1055 MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
1056     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1057   // If we have -ffunction-sections then we should emit the global value to a
1058   // uniqued section specifically for it.
1059   bool EmitUniquedSection;
1060   if (Kind.isText())
1061     EmitUniquedSection = TM.getFunctionSections();
1062   else
1063     EmitUniquedSection = TM.getDataSections();
1064 
1065   if ((EmitUniquedSection && !Kind.isCommon()) || GO->hasComdat()) {
1066     const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
1067     unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1068 
1069     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1070     int Selection = getSelectionForCOFF(GO);
1071     if (!Selection)
1072       Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1073     const GlobalValue *ComdatGV;
1074     if (GO->hasComdat())
1075       ComdatGV = getComdatGVForCOFF(GO);
1076     else
1077       ComdatGV = GO;
1078 
1079     unsigned UniqueID = MCContext::GenericSectionID;
1080     if (EmitUniquedSection)
1081       UniqueID = NextUniqueID++;
1082 
1083     if (!ComdatGV->hasPrivateLinkage()) {
1084       MCSymbol *Sym = TM.getSymbol(ComdatGV);
1085       StringRef COMDATSymName = Sym->getName();
1086       return getContext().getCOFFSection(Name, Characteristics, Kind,
1087                                          COMDATSymName, Selection, UniqueID);
1088     } else {
1089       SmallString<256> TmpData;
1090       getMangler().getNameWithPrefix(TmpData, GO, /*CannotUsePrivateLabel=*/true);
1091       return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
1092                                          Selection, UniqueID);
1093     }
1094   }
1095 
1096   if (Kind.isText())
1097     return TextSection;
1098 
1099   if (Kind.isThreadLocal())
1100     return TLSDataSection;
1101 
1102   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1103     return ReadOnlySection;
1104 
1105   // Note: we claim that common symbols are put in BSSSection, but they are
1106   // really emitted with the magic .comm directive, which creates a symbol table
1107   // entry but not a section.
1108   if (Kind.isBSS() || Kind.isCommon())
1109     return BSSSection;
1110 
1111   return DataSection;
1112 }
1113 
1114 void TargetLoweringObjectFileCOFF::getNameWithPrefix(
1115     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
1116     const TargetMachine &TM) const {
1117   bool CannotUsePrivateLabel = false;
1118   if (GV->hasPrivateLinkage() &&
1119       ((isa<Function>(GV) && TM.getFunctionSections()) ||
1120        (isa<GlobalVariable>(GV) && TM.getDataSections())))
1121     CannotUsePrivateLabel = true;
1122 
1123   getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1124 }
1125 
1126 MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
1127     const Function &F, const TargetMachine &TM) const {
1128   // If the function can be removed, produce a unique section so that
1129   // the table doesn't prevent the removal.
1130   const Comdat *C = F.getComdat();
1131   bool EmitUniqueSection = TM.getFunctionSections() || C;
1132   if (!EmitUniqueSection)
1133     return ReadOnlySection;
1134 
1135   // FIXME: we should produce a symbol for F instead.
1136   if (F.hasPrivateLinkage())
1137     return ReadOnlySection;
1138 
1139   MCSymbol *Sym = TM.getSymbol(&F);
1140   StringRef COMDATSymName = Sym->getName();
1141 
1142   SectionKind Kind = SectionKind::getReadOnly();
1143   const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
1144   unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1145   Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1146   unsigned UniqueID = NextUniqueID++;
1147 
1148   return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
1149                                      COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
1150 }
1151 
1152 void TargetLoweringObjectFileCOFF::emitModuleMetadata(
1153     MCStreamer &Streamer, Module &M, const TargetMachine &TM) const {
1154   if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
1155     // Emit the linker options to the linker .drectve section.  According to the
1156     // spec, this section is a space-separated string containing flags for
1157     // linker.
1158     MCSection *Sec = getDrectveSection();
1159     Streamer.SwitchSection(Sec);
1160     for (const auto &Option : LinkerOptions->operands()) {
1161       for (const auto &Piece : cast<MDNode>(Option)->operands()) {
1162         // Lead with a space for consistency with our dllexport implementation.
1163         std::string Directive(" ");
1164         Directive.append(cast<MDString>(Piece)->getString());
1165         Streamer.EmitBytes(Directive);
1166       }
1167     }
1168   }
1169 
1170   unsigned Version = 0;
1171   unsigned Flags = 0;
1172   StringRef Section;
1173 
1174   GetObjCImageInfo(M, Version, Flags, Section);
1175   if (Section.empty())
1176     return;
1177 
1178   auto &C = getContext();
1179   auto *S = C.getCOFFSection(
1180       Section, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
1181       SectionKind::getReadOnly());
1182   Streamer.SwitchSection(S);
1183   Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
1184   Streamer.EmitIntValue(Version, 4);
1185   Streamer.EmitIntValue(Flags, 4);
1186   Streamer.AddBlankLine();
1187 }
1188 
1189 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
1190                                               const TargetMachine &TM) {
1191   TargetLoweringObjectFile::Initialize(Ctx, TM);
1192   const Triple &T = TM.getTargetTriple();
1193   if (T.isKnownWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
1194     StaticCtorSection =
1195         Ctx.getCOFFSection(".CRT$XCU", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1196                                            COFF::IMAGE_SCN_MEM_READ,
1197                            SectionKind::getReadOnly());
1198     StaticDtorSection =
1199         Ctx.getCOFFSection(".CRT$XTX", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1200                                            COFF::IMAGE_SCN_MEM_READ,
1201                            SectionKind::getReadOnly());
1202   } else {
1203     StaticCtorSection = Ctx.getCOFFSection(
1204         ".ctors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1205                       COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1206         SectionKind::getData());
1207     StaticDtorSection = Ctx.getCOFFSection(
1208         ".dtors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1209                       COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1210         SectionKind::getData());
1211   }
1212 }
1213 
1214 static MCSectionCOFF *getCOFFStaticStructorSection(MCContext &Ctx,
1215                                                    const Triple &T, bool IsCtor,
1216                                                    unsigned Priority,
1217                                                    const MCSymbol *KeySym,
1218                                                    MCSectionCOFF *Default) {
1219   if (T.isKnownWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment())
1220     return Ctx.getAssociativeCOFFSection(Default, KeySym, 0);
1221 
1222   std::string Name = IsCtor ? ".ctors" : ".dtors";
1223   if (Priority != 65535)
1224     raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
1225 
1226   return Ctx.getAssociativeCOFFSection(
1227       Ctx.getCOFFSection(Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1228                                    COFF::IMAGE_SCN_MEM_READ |
1229                                    COFF::IMAGE_SCN_MEM_WRITE,
1230                          SectionKind::getData()),
1231       KeySym, 0);
1232 }
1233 
1234 MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
1235     unsigned Priority, const MCSymbol *KeySym) const {
1236   return getCOFFStaticStructorSection(getContext(), getTargetTriple(), true,
1237                                       Priority, KeySym,
1238                                       cast<MCSectionCOFF>(StaticCtorSection));
1239 }
1240 
1241 MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
1242     unsigned Priority, const MCSymbol *KeySym) const {
1243   return getCOFFStaticStructorSection(getContext(), getTargetTriple(), false,
1244                                       Priority, KeySym,
1245                                       cast<MCSectionCOFF>(StaticDtorSection));
1246 }
1247 
1248 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
1249     raw_ostream &OS, const GlobalValue *GV) const {
1250   emitLinkerFlagsForGlobalCOFF(OS, GV, getTargetTriple(), getMangler());
1251 }
1252 
1253 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForUsed(
1254     raw_ostream &OS, const GlobalValue *GV) const {
1255   emitLinkerFlagsForUsedCOFF(OS, GV, getTargetTriple(), getMangler());
1256 }
1257 
1258 //===----------------------------------------------------------------------===//
1259 //                                  Wasm
1260 //===----------------------------------------------------------------------===//
1261 
1262 static const Comdat *getWasmComdat(const GlobalValue *GV) {
1263   const Comdat *C = GV->getComdat();
1264   if (!C)
1265     return nullptr;
1266 
1267   if (C->getSelectionKind() != Comdat::Any)
1268     report_fatal_error("WebAssembly COMDATs only support "
1269                        "SelectionKind::Any, '" + C->getName() + "' cannot be "
1270                        "lowered.");
1271 
1272   return C;
1273 }
1274 
1275 static SectionKind getWasmKindForNamedSection(StringRef Name, SectionKind K) {
1276   // If we're told we have function data, then use that.
1277   if (K.isText())
1278     return SectionKind::getText();
1279 
1280   // Otherwise, ignore whatever section type the generic impl detected and use
1281   // a plain data section.
1282   return SectionKind::getData();
1283 }
1284 
1285 MCSection *TargetLoweringObjectFileWasm::getExplicitSectionGlobal(
1286     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1287   StringRef Name = GO->getSection();
1288 
1289   Kind = getWasmKindForNamedSection(Name, Kind);
1290 
1291   StringRef Group = "";
1292   if (const Comdat *C = getWasmComdat(GO)) {
1293     Group = C->getName();
1294   }
1295 
1296   return getContext().getWasmSection(Name, Kind, Group,
1297                                      MCContext::GenericSectionID);
1298 }
1299 
1300 static MCSectionWasm *selectWasmSectionForGlobal(
1301     MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
1302     const TargetMachine &TM, bool EmitUniqueSection, unsigned *NextUniqueID) {
1303   StringRef Group = "";
1304   if (const Comdat *C = getWasmComdat(GO)) {
1305     Group = C->getName();
1306   }
1307 
1308   bool UniqueSectionNames = TM.getUniqueSectionNames();
1309   SmallString<128> Name = getSectionPrefixForGlobal(Kind);
1310 
1311   if (const auto *F = dyn_cast<Function>(GO)) {
1312     const auto &OptionalPrefix = F->getSectionPrefix();
1313     if (OptionalPrefix)
1314       Name += *OptionalPrefix;
1315   }
1316 
1317   if (EmitUniqueSection && UniqueSectionNames) {
1318     Name.push_back('.');
1319     TM.getNameWithPrefix(Name, GO, Mang, true);
1320   }
1321   unsigned UniqueID = MCContext::GenericSectionID;
1322   if (EmitUniqueSection && !UniqueSectionNames) {
1323     UniqueID = *NextUniqueID;
1324     (*NextUniqueID)++;
1325   }
1326   return Ctx.getWasmSection(Name, Kind, Group, UniqueID);
1327 }
1328 
1329 MCSection *TargetLoweringObjectFileWasm::SelectSectionForGlobal(
1330     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1331 
1332   if (Kind.isCommon())
1333     report_fatal_error("mergable sections not supported yet on wasm");
1334 
1335   // If we have -ffunction-section or -fdata-section then we should emit the
1336   // global value to a uniqued section specifically for it.
1337   bool EmitUniqueSection = false;
1338   if (Kind.isText())
1339     EmitUniqueSection = TM.getFunctionSections();
1340   else
1341     EmitUniqueSection = TM.getDataSections();
1342   EmitUniqueSection |= GO->hasComdat();
1343 
1344   return selectWasmSectionForGlobal(getContext(), GO, Kind, getMangler(), TM,
1345                                     EmitUniqueSection, &NextUniqueID);
1346 }
1347 
1348 bool TargetLoweringObjectFileWasm::shouldPutJumpTableInFunctionSection(
1349     bool UsesLabelDifference, const Function &F) const {
1350   // We can always create relative relocations, so use another section
1351   // that can be marked non-executable.
1352   return false;
1353 }
1354 
1355 const MCExpr *TargetLoweringObjectFileWasm::lowerRelativeReference(
1356     const GlobalValue *LHS, const GlobalValue *RHS,
1357     const TargetMachine &TM) const {
1358   // We may only use a PLT-relative relocation to refer to unnamed_addr
1359   // functions.
1360   if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
1361     return nullptr;
1362 
1363   // Basic sanity checks.
1364   if (LHS->getType()->getPointerAddressSpace() != 0 ||
1365       RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
1366       RHS->isThreadLocal())
1367     return nullptr;
1368 
1369   return MCBinaryExpr::createSub(
1370       MCSymbolRefExpr::create(TM.getSymbol(LHS), MCSymbolRefExpr::VK_None,
1371                               getContext()),
1372       MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
1373 }
1374 
1375 void TargetLoweringObjectFileWasm::InitializeWasm() {
1376   StaticCtorSection =
1377       getContext().getWasmSection(".init_array", SectionKind::getData());
1378 }
1379 
1380 MCSection *TargetLoweringObjectFileWasm::getStaticCtorSection(
1381     unsigned Priority, const MCSymbol *KeySym) const {
1382   return Priority == UINT16_MAX ?
1383          StaticCtorSection :
1384          getContext().getWasmSection(".init_array." + utostr(Priority),
1385                                      SectionKind::getData());
1386 }
1387 
1388 MCSection *TargetLoweringObjectFileWasm::getStaticDtorSection(
1389     unsigned Priority, const MCSymbol *KeySym) const {
1390   llvm_unreachable("@llvm.global_dtors should have been lowered already");
1391   return nullptr;
1392 }
1393