xref: /llvm-project/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (revision b16d146838b8f4b34e072f34a5f194d9a4df4cc5) 
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/ADT/SmallString.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include "llvm/ADT/StringExtras.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/ADT/Triple.h"
20 #include "llvm/CodeGen/MachineModuleInfo.h"
21 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
22 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
23 #include "llvm/IR/Comdat.h"
24 #include "llvm/IR/Constants.h"
25 #include "llvm/IR/DataLayout.h"
26 #include "llvm/IR/DerivedTypes.h"
27 #include "llvm/IR/Function.h"
28 #include "llvm/IR/GlobalAlias.h"
29 #include "llvm/IR/GlobalObject.h"
30 #include "llvm/IR/GlobalValue.h"
31 #include "llvm/IR/GlobalVariable.h"
32 #include "llvm/IR/Mangler.h"
33 #include "llvm/IR/Metadata.h"
34 #include "llvm/IR/Module.h"
35 #include "llvm/IR/Type.h"
36 #include "llvm/MC/MCAsmInfo.h"
37 #include "llvm/MC/MCContext.h"
38 #include "llvm/MC/MCExpr.h"
39 #include "llvm/MC/MCSectionCOFF.h"
40 #include "llvm/MC/MCSectionELF.h"
41 #include "llvm/MC/MCSectionMachO.h"
42 #include "llvm/MC/MCSectionWasm.h"
43 #include "llvm/MC/MCStreamer.h"
44 #include "llvm/MC/MCSymbol.h"
45 #include "llvm/MC/MCSymbolELF.h"
46 #include "llvm/MC/MCValue.h"
47 #include "llvm/MC/SectionKind.h"
48 #include "llvm/ProfileData/InstrProf.h"
49 #include "llvm/Support/Casting.h"
50 #include "llvm/Support/CodeGen.h"
51 #include "llvm/Support/COFF.h"
52 #include "llvm/Support/Dwarf.h"
53 #include "llvm/Support/ELF.h"
54 #include "llvm/Support/ErrorHandling.h"
55 #include "llvm/Support/MachO.h"
56 #include "llvm/Support/raw_ostream.h"
57 #include "llvm/Target/TargetMachine.h"
58 #include <cassert>
59 #include <string>
60 
61 using namespace llvm;
62 using namespace dwarf;
63 
64 //===----------------------------------------------------------------------===//
65 //                                  ELF
66 //===----------------------------------------------------------------------===//
67 
68 MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
69     const GlobalValue *GV, const TargetMachine &TM,
70     MachineModuleInfo *MMI) const {
71   unsigned Encoding = getPersonalityEncoding();
72   if ((Encoding & 0x80) == DW_EH_PE_indirect)
73     return getContext().getOrCreateSymbol(StringRef("DW.ref.") +
74                                           TM.getSymbol(GV)->getName());
75   if ((Encoding & 0x70) == DW_EH_PE_absptr)
76     return TM.getSymbol(GV);
77   report_fatal_error("We do not support this DWARF encoding yet!");
78 }
79 
80 void TargetLoweringObjectFileELF::emitPersonalityValue(
81     MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
82   SmallString<64> NameData("DW.ref.");
83   NameData += Sym->getName();
84   MCSymbolELF *Label =
85       cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
86   Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
87   Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
88   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
89   MCSection *Sec = getContext().getELFNamedSection(".data", Label->getName(),
90                                                    ELF::SHT_PROGBITS, Flags, 0);
91   unsigned Size = DL.getPointerSize();
92   Streamer.SwitchSection(Sec);
93   Streamer.EmitValueToAlignment(DL.getPointerABIAlignment());
94   Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
95   const MCExpr *E = MCConstantExpr::create(Size, getContext());
96   Streamer.emitELFSize(Label, E);
97   Streamer.EmitLabel(Label);
98 
99   Streamer.EmitSymbolValue(Sym, Size);
100 }
101 
102 const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
103     const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
104     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
105   if (Encoding & DW_EH_PE_indirect) {
106     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
107 
108     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", TM);
109 
110     // Add information about the stub reference to ELFMMI so that the stub
111     // gets emitted by the asmprinter.
112     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
113     if (!StubSym.getPointer()) {
114       MCSymbol *Sym = TM.getSymbol(GV);
115       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
116     }
117 
118     return TargetLoweringObjectFile::
119       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
120                         Encoding & ~DW_EH_PE_indirect, Streamer);
121   }
122 
123   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
124                                                            MMI, Streamer);
125 }
126 
127 static SectionKind
128 getELFKindForNamedSection(StringRef Name, SectionKind K) {
129   // N.B.: The defaults used in here are no the same ones used in MC.
130   // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
131   // both gas and MC will produce a section with no flags. Given
132   // section(".eh_frame") gcc will produce:
133   //
134   //   .section   .eh_frame,"a",@progbits
135 
136   if (Name == getInstrProfSectionName(IPSK_covmap, Triple::ELF,
137                                       /*AddSegmentInfo=*/false))
138     return SectionKind::getMetadata();
139 
140   if (Name.empty() || Name[0] != '.') return K;
141 
142   // Some lame default implementation based on some magic section names.
143   if (Name == ".bss" ||
144       Name.startswith(".bss.") ||
145       Name.startswith(".gnu.linkonce.b.") ||
146       Name.startswith(".llvm.linkonce.b.") ||
147       Name == ".sbss" ||
148       Name.startswith(".sbss.") ||
149       Name.startswith(".gnu.linkonce.sb.") ||
150       Name.startswith(".llvm.linkonce.sb."))
151     return SectionKind::getBSS();
152 
153   if (Name == ".tdata" ||
154       Name.startswith(".tdata.") ||
155       Name.startswith(".gnu.linkonce.td.") ||
156       Name.startswith(".llvm.linkonce.td."))
157     return SectionKind::getThreadData();
158 
159   if (Name == ".tbss" ||
160       Name.startswith(".tbss.") ||
161       Name.startswith(".gnu.linkonce.tb.") ||
162       Name.startswith(".llvm.linkonce.tb."))
163     return SectionKind::getThreadBSS();
164 
165   return K;
166 }
167 
168 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
169   // Use SHT_NOTE for section whose name starts with ".note" to allow
170   // emitting ELF notes from C variable declaration.
171   // See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77609
172   if (Name.startswith(".note"))
173     return ELF::SHT_NOTE;
174 
175   if (Name == ".init_array")
176     return ELF::SHT_INIT_ARRAY;
177 
178   if (Name == ".fini_array")
179     return ELF::SHT_FINI_ARRAY;
180 
181   if (Name == ".preinit_array")
182     return ELF::SHT_PREINIT_ARRAY;
183 
184   if (K.isBSS() || K.isThreadBSS())
185     return ELF::SHT_NOBITS;
186 
187   return ELF::SHT_PROGBITS;
188 }
189 
190 static unsigned getELFSectionFlags(SectionKind K) {
191   unsigned Flags = 0;
192 
193   if (!K.isMetadata())
194     Flags |= ELF::SHF_ALLOC;
195 
196   if (K.isText())
197     Flags |= ELF::SHF_EXECINSTR;
198 
199   if (K.isExecuteOnly())
200     Flags |= ELF::SHF_ARM_PURECODE;
201 
202   if (K.isWriteable())
203     Flags |= ELF::SHF_WRITE;
204 
205   if (K.isThreadLocal())
206     Flags |= ELF::SHF_TLS;
207 
208   if (K.isMergeableCString() || K.isMergeableConst())
209     Flags |= ELF::SHF_MERGE;
210 
211   if (K.isMergeableCString())
212     Flags |= ELF::SHF_STRINGS;
213 
214   return Flags;
215 }
216 
217 static const Comdat *getELFComdat(const GlobalValue *GV) {
218   const Comdat *C = GV->getComdat();
219   if (!C)
220     return nullptr;
221 
222   if (C->getSelectionKind() != Comdat::Any)
223     report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
224                        C->getName() + "' cannot be lowered.");
225 
226   return C;
227 }
228 
229 static const MCSymbolELF *getAssociatedSymbol(const GlobalObject *GO,
230                                               const TargetMachine &TM) {
231   MDNode *MD = GO->getMetadata(LLVMContext::MD_associated);
232   if (!MD)
233     return nullptr;
234 
235   const MDOperand &Op = MD->getOperand(0);
236   if (!Op.get())
237     return nullptr;
238 
239   auto *VM = dyn_cast<ValueAsMetadata>(Op);
240   if (!VM)
241     report_fatal_error("MD_associated operand is not ValueAsMetadata");
242 
243   GlobalObject *OtherGO = dyn_cast<GlobalObject>(VM->getValue());
244   return OtherGO ? dyn_cast<MCSymbolELF>(TM.getSymbol(OtherGO)) : nullptr;
245 }
246 
247 MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
248     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
249   StringRef SectionName = GO->getSection();
250 
251   // Check if '#pragma clang section' name is applicable.
252   // Note that pragma directive overrides -ffunction-section, -fdata-section
253   // and so section name is exactly as user specified and not uniqued.
254   const GlobalVariable *GV = dyn_cast<GlobalVariable>(GO);
255   if (GV && GV->hasImplicitSection()) {
256     auto Attrs = GV->getAttributes();
257     if (Attrs.hasAttribute("bss-section") && Kind.isBSS()) {
258       SectionName = Attrs.getAttribute("bss-section").getValueAsString();
259     } else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()) {
260       SectionName = Attrs.getAttribute("rodata-section").getValueAsString();
261     } else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
262       SectionName = Attrs.getAttribute("data-section").getValueAsString();
263     }
264   }
265   const Function *F = dyn_cast<Function>(GO);
266   if (F && F->hasFnAttribute("implicit-section-name")) {
267     SectionName = F->getFnAttribute("implicit-section-name").getValueAsString();
268   }
269 
270   // Infer section flags from the section name if we can.
271   Kind = getELFKindForNamedSection(SectionName, Kind);
272 
273   StringRef Group = "";
274   unsigned Flags = getELFSectionFlags(Kind);
275   if (const Comdat *C = getELFComdat(GO)) {
276     Group = C->getName();
277     Flags |= ELF::SHF_GROUP;
278   }
279 
280   // A section can have at most one associated section. Put each global with
281   // MD_associated in a unique section.
282   unsigned UniqueID = MCContext::GenericSectionID;
283   const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
284   if (AssociatedSymbol) {
285     UniqueID = NextUniqueID++;
286     Flags |= ELF::SHF_LINK_ORDER;
287   }
288 
289   MCSectionELF *Section = getContext().getELFSection(
290       SectionName, getELFSectionType(SectionName, Kind), Flags,
291       /*EntrySize=*/0, Group, UniqueID, AssociatedSymbol);
292   // Make sure that we did not get some other section with incompatible sh_link.
293   // This should not be possible due to UniqueID code above.
294   assert(Section->getAssociatedSymbol() == AssociatedSymbol);
295   return Section;
296 }
297 
298 /// Return the section prefix name used by options FunctionsSections and
299 /// DataSections.
300 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
301   if (Kind.isText())
302     return ".text";
303   if (Kind.isReadOnly())
304     return ".rodata";
305   if (Kind.isBSS())
306     return ".bss";
307   if (Kind.isThreadData())
308     return ".tdata";
309   if (Kind.isThreadBSS())
310     return ".tbss";
311   if (Kind.isData())
312     return ".data";
313   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
314   return ".data.rel.ro";
315 }
316 
317 static MCSectionELF *selectELFSectionForGlobal(
318     MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
319     const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
320     unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol) {
321   unsigned EntrySize = 0;
322   if (Kind.isMergeableCString()) {
323     if (Kind.isMergeable2ByteCString()) {
324       EntrySize = 2;
325     } else if (Kind.isMergeable4ByteCString()) {
326       EntrySize = 4;
327     } else {
328       EntrySize = 1;
329       assert(Kind.isMergeable1ByteCString() && "unknown string width");
330     }
331   } else if (Kind.isMergeableConst()) {
332     if (Kind.isMergeableConst4()) {
333       EntrySize = 4;
334     } else if (Kind.isMergeableConst8()) {
335       EntrySize = 8;
336     } else if (Kind.isMergeableConst16()) {
337       EntrySize = 16;
338     } else {
339       assert(Kind.isMergeableConst32() && "unknown data width");
340       EntrySize = 32;
341     }
342   }
343 
344   StringRef Group = "";
345   if (const Comdat *C = getELFComdat(GO)) {
346     Flags |= ELF::SHF_GROUP;
347     Group = C->getName();
348   }
349 
350   bool UniqueSectionNames = TM.getUniqueSectionNames();
351   SmallString<128> Name;
352   if (Kind.isMergeableCString()) {
353     // We also need alignment here.
354     // FIXME: this is getting the alignment of the character, not the
355     // alignment of the global!
356     unsigned Align = GO->getParent()->getDataLayout().getPreferredAlignment(
357         cast<GlobalVariable>(GO));
358 
359     std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
360     Name = SizeSpec + utostr(Align);
361   } else if (Kind.isMergeableConst()) {
362     Name = ".rodata.cst";
363     Name += utostr(EntrySize);
364   } else {
365     Name = getSectionPrefixForGlobal(Kind);
366   }
367 
368   if (const auto *F = dyn_cast<Function>(GO)) {
369     const auto &OptionalPrefix = F->getSectionPrefix();
370     if (OptionalPrefix)
371       Name += *OptionalPrefix;
372   }
373 
374   if (EmitUniqueSection && UniqueSectionNames) {
375     Name.push_back('.');
376     TM.getNameWithPrefix(Name, GO, Mang, true);
377   }
378   unsigned UniqueID = MCContext::GenericSectionID;
379   if (EmitUniqueSection && !UniqueSectionNames) {
380     UniqueID = *NextUniqueID;
381     (*NextUniqueID)++;
382   }
383   // Use 0 as the unique ID for execute-only text
384   if (Kind.isExecuteOnly())
385     UniqueID = 0;
386   return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags,
387                            EntrySize, Group, UniqueID, AssociatedSymbol);
388 }
389 
390 MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
391     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
392   unsigned Flags = getELFSectionFlags(Kind);
393 
394   // If we have -ffunction-section or -fdata-section then we should emit the
395   // global value to a uniqued section specifically for it.
396   bool EmitUniqueSection = false;
397   if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
398     if (Kind.isText())
399       EmitUniqueSection = TM.getFunctionSections();
400     else
401       EmitUniqueSection = TM.getDataSections();
402   }
403   EmitUniqueSection |= GO->hasComdat();
404 
405   const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
406   if (AssociatedSymbol) {
407     EmitUniqueSection = true;
408     Flags |= ELF::SHF_LINK_ORDER;
409   }
410 
411   MCSectionELF *Section = selectELFSectionForGlobal(
412       getContext(), GO, Kind, getMangler(), TM, EmitUniqueSection, Flags,
413       &NextUniqueID, AssociatedSymbol);
414   assert(Section->getAssociatedSymbol() == AssociatedSymbol);
415   return Section;
416 }
417 
418 MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
419     const Function &F, const TargetMachine &TM) const {
420   // If the function can be removed, produce a unique section so that
421   // the table doesn't prevent the removal.
422   const Comdat *C = F.getComdat();
423   bool EmitUniqueSection = TM.getFunctionSections() || C;
424   if (!EmitUniqueSection)
425     return ReadOnlySection;
426 
427   return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
428                                    getMangler(), TM, EmitUniqueSection,
429                                    ELF::SHF_ALLOC, &NextUniqueID,
430                                    /* AssociatedSymbol */ nullptr);
431 }
432 
433 bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
434     bool UsesLabelDifference, const Function &F) const {
435   // We can always create relative relocations, so use another section
436   // that can be marked non-executable.
437   return false;
438 }
439 
440 /// Given a mergeable constant with the specified size and relocation
441 /// information, return a section that it should be placed in.
442 MCSection *TargetLoweringObjectFileELF::getSectionForConstant(
443     const DataLayout &DL, SectionKind Kind, const Constant *C,
444     unsigned &Align) const {
445   if (Kind.isMergeableConst4() && MergeableConst4Section)
446     return MergeableConst4Section;
447   if (Kind.isMergeableConst8() && MergeableConst8Section)
448     return MergeableConst8Section;
449   if (Kind.isMergeableConst16() && MergeableConst16Section)
450     return MergeableConst16Section;
451   if (Kind.isMergeableConst32() && MergeableConst32Section)
452     return MergeableConst32Section;
453   if (Kind.isReadOnly())
454     return ReadOnlySection;
455 
456   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
457   return DataRelROSection;
458 }
459 
460 static MCSectionELF *getStaticStructorSection(MCContext &Ctx, bool UseInitArray,
461                                               bool IsCtor, unsigned Priority,
462                                               const MCSymbol *KeySym) {
463   std::string Name;
464   unsigned Type;
465   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
466   StringRef COMDAT = KeySym ? KeySym->getName() : "";
467 
468   if (KeySym)
469     Flags |= ELF::SHF_GROUP;
470 
471   if (UseInitArray) {
472     if (IsCtor) {
473       Type = ELF::SHT_INIT_ARRAY;
474       Name = ".init_array";
475     } else {
476       Type = ELF::SHT_FINI_ARRAY;
477       Name = ".fini_array";
478     }
479     if (Priority != 65535) {
480       Name += '.';
481       Name += utostr(Priority);
482     }
483   } else {
484     // The default scheme is .ctor / .dtor, so we have to invert the priority
485     // numbering.
486     if (IsCtor)
487       Name = ".ctors";
488     else
489       Name = ".dtors";
490     if (Priority != 65535) {
491       Name += '.';
492       Name += utostr(65535 - Priority);
493     }
494     Type = ELF::SHT_PROGBITS;
495   }
496 
497   return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
498 }
499 
500 MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
501     unsigned Priority, const MCSymbol *KeySym) const {
502   return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
503                                   KeySym);
504 }
505 
506 MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
507     unsigned Priority, const MCSymbol *KeySym) const {
508   return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
509                                   KeySym);
510 }
511 
512 const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
513     const GlobalValue *LHS, const GlobalValue *RHS,
514     const TargetMachine &TM) const {
515   // We may only use a PLT-relative relocation to refer to unnamed_addr
516   // functions.
517   if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
518     return nullptr;
519 
520   // Basic sanity checks.
521   if (LHS->getType()->getPointerAddressSpace() != 0 ||
522       RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
523       RHS->isThreadLocal())
524     return nullptr;
525 
526   return MCBinaryExpr::createSub(
527       MCSymbolRefExpr::create(TM.getSymbol(LHS), PLTRelativeVariantKind,
528                               getContext()),
529       MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
530 }
531 
532 void
533 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
534   UseInitArray = UseInitArray_;
535   MCContext &Ctx = getContext();
536   if (!UseInitArray) {
537     StaticCtorSection = Ctx.getELFSection(".ctors", ELF::SHT_PROGBITS,
538                                           ELF::SHF_ALLOC | ELF::SHF_WRITE);
539 
540     StaticDtorSection = Ctx.getELFSection(".dtors", ELF::SHT_PROGBITS,
541                                           ELF::SHF_ALLOC | ELF::SHF_WRITE);
542     return;
543   }
544 
545   StaticCtorSection = Ctx.getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
546                                         ELF::SHF_WRITE | ELF::SHF_ALLOC);
547   StaticDtorSection = Ctx.getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
548                                         ELF::SHF_WRITE | ELF::SHF_ALLOC);
549 }
550 
551 //===----------------------------------------------------------------------===//
552 //                                 MachO
553 //===----------------------------------------------------------------------===//
554 
555 TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
556   : TargetLoweringObjectFile() {
557   SupportIndirectSymViaGOTPCRel = true;
558 }
559 
560 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
561                                                const TargetMachine &TM) {
562   TargetLoweringObjectFile::Initialize(Ctx, TM);
563   if (TM.getRelocationModel() == Reloc::Static) {
564     StaticCtorSection = Ctx.getMachOSection("__TEXT", "__constructor", 0,
565                                             SectionKind::getData());
566     StaticDtorSection = Ctx.getMachOSection("__TEXT", "__destructor", 0,
567                                             SectionKind::getData());
568   } else {
569     StaticCtorSection = Ctx.getMachOSection("__DATA", "__mod_init_func",
570                                             MachO::S_MOD_INIT_FUNC_POINTERS,
571                                             SectionKind::getData());
572     StaticDtorSection = Ctx.getMachOSection("__DATA", "__mod_term_func",
573                                             MachO::S_MOD_TERM_FUNC_POINTERS,
574                                             SectionKind::getData());
575   }
576 }
577 
578 /// emitModuleFlags - Perform code emission for module flags.
579 void TargetLoweringObjectFileMachO::emitModuleFlags(
580     MCStreamer &Streamer, ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
581     const TargetMachine &TM) const {
582   unsigned VersionVal = 0;
583   unsigned ImageInfoFlags = 0;
584   MDNode *LinkerOptions = nullptr;
585   StringRef SectionVal;
586 
587   for (const auto &MFE : ModuleFlags) {
588     // Ignore flags with 'Require' behavior.
589     if (MFE.Behavior == Module::Require)
590       continue;
591 
592     StringRef Key = MFE.Key->getString();
593     Metadata *Val = MFE.Val;
594 
595     if (Key == "Objective-C Image Info Version") {
596       VersionVal = mdconst::extract<ConstantInt>(Val)->getZExtValue();
597     } else if (Key == "Objective-C Garbage Collection" ||
598                Key == "Objective-C GC Only" ||
599                Key == "Objective-C Is Simulated" ||
600                Key == "Objective-C Class Properties" ||
601                Key == "Objective-C Image Swift Version") {
602       ImageInfoFlags |= mdconst::extract<ConstantInt>(Val)->getZExtValue();
603     } else if (Key == "Objective-C Image Info Section") {
604       SectionVal = cast<MDString>(Val)->getString();
605     } else if (Key == "Linker Options") {
606       LinkerOptions = cast<MDNode>(Val);
607     }
608   }
609 
610   // Emit the linker options if present.
611   if (LinkerOptions) {
612     for (const auto &Option : LinkerOptions->operands()) {
613       SmallVector<std::string, 4> StrOptions;
614       for (const auto &Piece : cast<MDNode>(Option)->operands())
615         StrOptions.push_back(cast<MDString>(Piece)->getString());
616       Streamer.EmitLinkerOptions(StrOptions);
617     }
618   }
619 
620   // The section is mandatory. If we don't have it, then we don't have GC info.
621   if (SectionVal.empty()) return;
622 
623   StringRef Segment, Section;
624   unsigned TAA = 0, StubSize = 0;
625   bool TAAParsed;
626   std::string ErrorCode =
627     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
628                                           TAA, TAAParsed, StubSize);
629   if (!ErrorCode.empty())
630     // If invalid, report the error with report_fatal_error.
631     report_fatal_error("Invalid section specifier '" + Section + "': " +
632                        ErrorCode + ".");
633 
634   // Get the section.
635   MCSectionMachO *S = getContext().getMachOSection(
636       Segment, Section, TAA, StubSize, SectionKind::getData());
637   Streamer.SwitchSection(S);
638   Streamer.EmitLabel(getContext().
639                      getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
640   Streamer.EmitIntValue(VersionVal, 4);
641   Streamer.EmitIntValue(ImageInfoFlags, 4);
642   Streamer.AddBlankLine();
643 }
644 
645 static void checkMachOComdat(const GlobalValue *GV) {
646   const Comdat *C = GV->getComdat();
647   if (!C)
648     return;
649 
650   report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
651                      "' cannot be lowered.");
652 }
653 
654 MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
655     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
656   // Parse the section specifier and create it if valid.
657   StringRef Segment, Section;
658   unsigned TAA = 0, StubSize = 0;
659   bool TAAParsed;
660 
661   checkMachOComdat(GO);
662 
663   std::string ErrorCode =
664     MCSectionMachO::ParseSectionSpecifier(GO->getSection(), Segment, Section,
665                                           TAA, TAAParsed, StubSize);
666   if (!ErrorCode.empty()) {
667     // If invalid, report the error with report_fatal_error.
668     report_fatal_error("Global variable '" + GO->getName() +
669                        "' has an invalid section specifier '" +
670                        GO->getSection() + "': " + ErrorCode + ".");
671   }
672 
673   // Get the section.
674   MCSectionMachO *S =
675       getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
676 
677   // If TAA wasn't set by ParseSectionSpecifier() above,
678   // use the value returned by getMachOSection() as a default.
679   if (!TAAParsed)
680     TAA = S->getTypeAndAttributes();
681 
682   // Okay, now that we got the section, verify that the TAA & StubSize agree.
683   // If the user declared multiple globals with different section flags, we need
684   // to reject it here.
685   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
686     // If invalid, report the error with report_fatal_error.
687     report_fatal_error("Global variable '" + GO->getName() +
688                        "' section type or attributes does not match previous"
689                        " section specifier");
690   }
691 
692   return S;
693 }
694 
695 MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
696     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
697   checkMachOComdat(GO);
698 
699   // Handle thread local data.
700   if (Kind.isThreadBSS()) return TLSBSSSection;
701   if (Kind.isThreadData()) return TLSDataSection;
702 
703   if (Kind.isText())
704     return GO->isWeakForLinker() ? TextCoalSection : TextSection;
705 
706   // If this is weak/linkonce, put this in a coalescable section, either in text
707   // or data depending on if it is writable.
708   if (GO->isWeakForLinker()) {
709     if (Kind.isReadOnly())
710       return ConstTextCoalSection;
711     return DataCoalSection;
712   }
713 
714   // FIXME: Alignment check should be handled by section classifier.
715   if (Kind.isMergeable1ByteCString() &&
716       GO->getParent()->getDataLayout().getPreferredAlignment(
717           cast<GlobalVariable>(GO)) < 32)
718     return CStringSection;
719 
720   // Do not put 16-bit arrays in the UString section if they have an
721   // externally visible label, this runs into issues with certain linker
722   // versions.
723   if (Kind.isMergeable2ByteCString() && !GO->hasExternalLinkage() &&
724       GO->getParent()->getDataLayout().getPreferredAlignment(
725           cast<GlobalVariable>(GO)) < 32)
726     return UStringSection;
727 
728   // With MachO only variables whose corresponding symbol starts with 'l' or
729   // 'L' can be merged, so we only try merging GVs with private linkage.
730   if (GO->hasPrivateLinkage() && Kind.isMergeableConst()) {
731     if (Kind.isMergeableConst4())
732       return FourByteConstantSection;
733     if (Kind.isMergeableConst8())
734       return EightByteConstantSection;
735     if (Kind.isMergeableConst16())
736       return SixteenByteConstantSection;
737   }
738 
739   // Otherwise, if it is readonly, but not something we can specially optimize,
740   // just drop it in .const.
741   if (Kind.isReadOnly())
742     return ReadOnlySection;
743 
744   // If this is marked const, put it into a const section.  But if the dynamic
745   // linker needs to write to it, put it in the data segment.
746   if (Kind.isReadOnlyWithRel())
747     return ConstDataSection;
748 
749   // Put zero initialized globals with strong external linkage in the
750   // DATA, __common section with the .zerofill directive.
751   if (Kind.isBSSExtern())
752     return DataCommonSection;
753 
754   // Put zero initialized globals with local linkage in __DATA,__bss directive
755   // with the .zerofill directive (aka .lcomm).
756   if (Kind.isBSSLocal())
757     return DataBSSSection;
758 
759   // Otherwise, just drop the variable in the normal data section.
760   return DataSection;
761 }
762 
763 MCSection *TargetLoweringObjectFileMachO::getSectionForConstant(
764     const DataLayout &DL, SectionKind Kind, const Constant *C,
765     unsigned &Align) const {
766   // If this constant requires a relocation, we have to put it in the data
767   // segment, not in the text segment.
768   if (Kind.isData() || Kind.isReadOnlyWithRel())
769     return ConstDataSection;
770 
771   if (Kind.isMergeableConst4())
772     return FourByteConstantSection;
773   if (Kind.isMergeableConst8())
774     return EightByteConstantSection;
775   if (Kind.isMergeableConst16())
776     return SixteenByteConstantSection;
777   return ReadOnlySection;  // .const
778 }
779 
780 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
781     const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
782     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
783   // The mach-o version of this method defaults to returning a stub reference.
784 
785   if (Encoding & DW_EH_PE_indirect) {
786     MachineModuleInfoMachO &MachOMMI =
787       MMI->getObjFileInfo<MachineModuleInfoMachO>();
788 
789     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
790 
791     // Add information about the stub reference to MachOMMI so that the stub
792     // gets emitted by the asmprinter.
793     MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
794     if (!StubSym.getPointer()) {
795       MCSymbol *Sym = TM.getSymbol(GV);
796       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
797     }
798 
799     return TargetLoweringObjectFile::
800       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
801                         Encoding & ~DW_EH_PE_indirect, Streamer);
802   }
803 
804   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
805                                                            MMI, Streamer);
806 }
807 
808 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
809     const GlobalValue *GV, const TargetMachine &TM,
810     MachineModuleInfo *MMI) const {
811   // The mach-o version of this method defaults to returning a stub reference.
812   MachineModuleInfoMachO &MachOMMI =
813     MMI->getObjFileInfo<MachineModuleInfoMachO>();
814 
815   MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
816 
817   // Add information about the stub reference to MachOMMI so that the stub
818   // gets emitted by the asmprinter.
819   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
820   if (!StubSym.getPointer()) {
821     MCSymbol *Sym = TM.getSymbol(GV);
822     StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
823   }
824 
825   return SSym;
826 }
827 
828 const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
829     const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
830     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
831   // Although MachO 32-bit targets do not explicitly have a GOTPCREL relocation
832   // as 64-bit do, we replace the GOT equivalent by accessing the final symbol
833   // through a non_lazy_ptr stub instead. One advantage is that it allows the
834   // computation of deltas to final external symbols. Example:
835   //
836   //    _extgotequiv:
837   //       .long   _extfoo
838   //
839   //    _delta:
840   //       .long   _extgotequiv-_delta
841   //
842   // is transformed to:
843   //
844   //    _delta:
845   //       .long   L_extfoo$non_lazy_ptr-(_delta+0)
846   //
847   //       .section        __IMPORT,__pointers,non_lazy_symbol_pointers
848   //    L_extfoo$non_lazy_ptr:
849   //       .indirect_symbol        _extfoo
850   //       .long   0
851   //
852   MachineModuleInfoMachO &MachOMMI =
853     MMI->getObjFileInfo<MachineModuleInfoMachO>();
854   MCContext &Ctx = getContext();
855 
856   // The offset must consider the original displacement from the base symbol
857   // since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
858   Offset = -MV.getConstant();
859   const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
860 
861   // Access the final symbol via sym$non_lazy_ptr and generate the appropriated
862   // non_lazy_ptr stubs.
863   SmallString<128> Name;
864   StringRef Suffix = "$non_lazy_ptr";
865   Name += MMI->getModule()->getDataLayout().getPrivateGlobalPrefix();
866   Name += Sym->getName();
867   Name += Suffix;
868   MCSymbol *Stub = Ctx.getOrCreateSymbol(Name);
869 
870   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
871   if (!StubSym.getPointer())
872     StubSym = MachineModuleInfoImpl::
873       StubValueTy(const_cast<MCSymbol *>(Sym), true /* access indirectly */);
874 
875   const MCExpr *BSymExpr =
876     MCSymbolRefExpr::create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
877   const MCExpr *LHS =
878     MCSymbolRefExpr::create(Stub, MCSymbolRefExpr::VK_None, Ctx);
879 
880   if (!Offset)
881     return MCBinaryExpr::createSub(LHS, BSymExpr, Ctx);
882 
883   const MCExpr *RHS =
884     MCBinaryExpr::createAdd(BSymExpr, MCConstantExpr::create(Offset, Ctx), Ctx);
885   return MCBinaryExpr::createSub(LHS, RHS, Ctx);
886 }
887 
888 static bool canUsePrivateLabel(const MCAsmInfo &AsmInfo,
889                                const MCSection &Section) {
890   if (!AsmInfo.isSectionAtomizableBySymbols(Section))
891     return true;
892 
893   // If it is not dead stripped, it is safe to use private labels.
894   const MCSectionMachO &SMO = cast<MCSectionMachO>(Section);
895   if (SMO.hasAttribute(MachO::S_ATTR_NO_DEAD_STRIP))
896     return true;
897 
898   return false;
899 }
900 
901 void TargetLoweringObjectFileMachO::getNameWithPrefix(
902     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
903     const TargetMachine &TM) const {
904   bool CannotUsePrivateLabel = true;
905   if (auto *GO = GV->getBaseObject()) {
906     SectionKind GOKind = TargetLoweringObjectFile::getKindForGlobal(GO, TM);
907     const MCSection *TheSection = SectionForGlobal(GO, GOKind, TM);
908     CannotUsePrivateLabel =
909         !canUsePrivateLabel(*TM.getMCAsmInfo(), *TheSection);
910   }
911   getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
912 }
913 
914 //===----------------------------------------------------------------------===//
915 //                                  COFF
916 //===----------------------------------------------------------------------===//
917 
918 static unsigned
919 getCOFFSectionFlags(SectionKind K, const TargetMachine &TM) {
920   unsigned Flags = 0;
921   bool isThumb = TM.getTargetTriple().getArch() == Triple::thumb;
922 
923   if (K.isMetadata())
924     Flags |=
925       COFF::IMAGE_SCN_MEM_DISCARDABLE;
926   else if (K.isText())
927     Flags |=
928       COFF::IMAGE_SCN_MEM_EXECUTE |
929       COFF::IMAGE_SCN_MEM_READ |
930       COFF::IMAGE_SCN_CNT_CODE |
931       (isThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0);
932   else if (K.isBSS())
933     Flags |=
934       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
935       COFF::IMAGE_SCN_MEM_READ |
936       COFF::IMAGE_SCN_MEM_WRITE;
937   else if (K.isThreadLocal())
938     Flags |=
939       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
940       COFF::IMAGE_SCN_MEM_READ |
941       COFF::IMAGE_SCN_MEM_WRITE;
942   else if (K.isReadOnly() || K.isReadOnlyWithRel())
943     Flags |=
944       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
945       COFF::IMAGE_SCN_MEM_READ;
946   else if (K.isWriteable())
947     Flags |=
948       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
949       COFF::IMAGE_SCN_MEM_READ |
950       COFF::IMAGE_SCN_MEM_WRITE;
951 
952   return Flags;
953 }
954 
955 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
956   const Comdat *C = GV->getComdat();
957   assert(C && "expected GV to have a Comdat!");
958 
959   StringRef ComdatGVName = C->getName();
960   const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
961   if (!ComdatGV)
962     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
963                        "' does not exist.");
964 
965   if (ComdatGV->getComdat() != C)
966     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
967                        "' is not a key for its COMDAT.");
968 
969   return ComdatGV;
970 }
971 
972 static int getSelectionForCOFF(const GlobalValue *GV) {
973   if (const Comdat *C = GV->getComdat()) {
974     const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
975     if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
976       ComdatKey = GA->getBaseObject();
977     if (ComdatKey == GV) {
978       switch (C->getSelectionKind()) {
979       case Comdat::Any:
980         return COFF::IMAGE_COMDAT_SELECT_ANY;
981       case Comdat::ExactMatch:
982         return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
983       case Comdat::Largest:
984         return COFF::IMAGE_COMDAT_SELECT_LARGEST;
985       case Comdat::NoDuplicates:
986         return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
987       case Comdat::SameSize:
988         return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
989       }
990     } else {
991       return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
992     }
993   }
994   return 0;
995 }
996 
997 MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
998     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
999   int Selection = 0;
1000   unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1001   StringRef Name = GO->getSection();
1002   StringRef COMDATSymName = "";
1003   if (GO->hasComdat()) {
1004     Selection = getSelectionForCOFF(GO);
1005     const GlobalValue *ComdatGV;
1006     if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
1007       ComdatGV = getComdatGVForCOFF(GO);
1008     else
1009       ComdatGV = GO;
1010 
1011     if (!ComdatGV->hasPrivateLinkage()) {
1012       MCSymbol *Sym = TM.getSymbol(ComdatGV);
1013       COMDATSymName = Sym->getName();
1014       Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1015     } else {
1016       Selection = 0;
1017     }
1018   }
1019 
1020   return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
1021                                      Selection);
1022 }
1023 
1024 static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
1025   if (Kind.isText())
1026     return ".text";
1027   if (Kind.isBSS())
1028     return ".bss";
1029   if (Kind.isThreadLocal())
1030     return ".tls$";
1031   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1032     return ".rdata";
1033   return ".data";
1034 }
1035 
1036 MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
1037     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1038   // If we have -ffunction-sections then we should emit the global value to a
1039   // uniqued section specifically for it.
1040   bool EmitUniquedSection;
1041   if (Kind.isText())
1042     EmitUniquedSection = TM.getFunctionSections();
1043   else
1044     EmitUniquedSection = TM.getDataSections();
1045 
1046   if ((EmitUniquedSection && !Kind.isCommon()) || GO->hasComdat()) {
1047     const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
1048     unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1049 
1050     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1051     int Selection = getSelectionForCOFF(GO);
1052     if (!Selection)
1053       Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1054     const GlobalValue *ComdatGV;
1055     if (GO->hasComdat())
1056       ComdatGV = getComdatGVForCOFF(GO);
1057     else
1058       ComdatGV = GO;
1059 
1060     unsigned UniqueID = MCContext::GenericSectionID;
1061     if (EmitUniquedSection)
1062       UniqueID = NextUniqueID++;
1063 
1064     if (!ComdatGV->hasPrivateLinkage()) {
1065       MCSymbol *Sym = TM.getSymbol(ComdatGV);
1066       StringRef COMDATSymName = Sym->getName();
1067       return getContext().getCOFFSection(Name, Characteristics, Kind,
1068                                          COMDATSymName, Selection, UniqueID);
1069     } else {
1070       SmallString<256> TmpData;
1071       getMangler().getNameWithPrefix(TmpData, GO, /*CannotUsePrivateLabel=*/true);
1072       return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
1073                                          Selection, UniqueID);
1074     }
1075   }
1076 
1077   if (Kind.isText())
1078     return TextSection;
1079 
1080   if (Kind.isThreadLocal())
1081     return TLSDataSection;
1082 
1083   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1084     return ReadOnlySection;
1085 
1086   // Note: we claim that common symbols are put in BSSSection, but they are
1087   // really emitted with the magic .comm directive, which creates a symbol table
1088   // entry but not a section.
1089   if (Kind.isBSS() || Kind.isCommon())
1090     return BSSSection;
1091 
1092   return DataSection;
1093 }
1094 
1095 void TargetLoweringObjectFileCOFF::getNameWithPrefix(
1096     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
1097     const TargetMachine &TM) const {
1098   bool CannotUsePrivateLabel = false;
1099   if (GV->hasPrivateLinkage() &&
1100       ((isa<Function>(GV) && TM.getFunctionSections()) ||
1101        (isa<GlobalVariable>(GV) && TM.getDataSections())))
1102     CannotUsePrivateLabel = true;
1103 
1104   getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1105 }
1106 
1107 MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
1108     const Function &F, const TargetMachine &TM) const {
1109   // If the function can be removed, produce a unique section so that
1110   // the table doesn't prevent the removal.
1111   const Comdat *C = F.getComdat();
1112   bool EmitUniqueSection = TM.getFunctionSections() || C;
1113   if (!EmitUniqueSection)
1114     return ReadOnlySection;
1115 
1116   // FIXME: we should produce a symbol for F instead.
1117   if (F.hasPrivateLinkage())
1118     return ReadOnlySection;
1119 
1120   MCSymbol *Sym = TM.getSymbol(&F);
1121   StringRef COMDATSymName = Sym->getName();
1122 
1123   SectionKind Kind = SectionKind::getReadOnly();
1124   const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
1125   unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1126   Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1127   unsigned UniqueID = NextUniqueID++;
1128 
1129   return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
1130                                      COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
1131 }
1132 
1133 void TargetLoweringObjectFileCOFF::emitModuleFlags(
1134     MCStreamer &Streamer, ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
1135     const TargetMachine &TM) const {
1136   MDNode *LinkerOptions = nullptr;
1137 
1138   for (const auto &MFE : ModuleFlags) {
1139     StringRef Key = MFE.Key->getString();
1140     if (Key == "Linker Options")
1141       LinkerOptions = cast<MDNode>(MFE.Val);
1142   }
1143 
1144   if (LinkerOptions) {
1145     // Emit the linker options to the linker .drectve section.  According to the
1146     // spec, this section is a space-separated string containing flags for
1147     // linker.
1148     MCSection *Sec = getDrectveSection();
1149     Streamer.SwitchSection(Sec);
1150     for (const auto &Option : LinkerOptions->operands()) {
1151       for (const auto &Piece : cast<MDNode>(Option)->operands()) {
1152         // Lead with a space for consistency with our dllexport implementation.
1153         std::string Directive(" ");
1154         Directive.append(cast<MDString>(Piece)->getString());
1155         Streamer.EmitBytes(Directive);
1156       }
1157     }
1158   }
1159 }
1160 
1161 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
1162                                               const TargetMachine &TM) {
1163   TargetLoweringObjectFile::Initialize(Ctx, TM);
1164   const Triple &T = TM.getTargetTriple();
1165   if (T.isKnownWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
1166     StaticCtorSection =
1167         Ctx.getCOFFSection(".CRT$XCU", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1168                                            COFF::IMAGE_SCN_MEM_READ,
1169                            SectionKind::getReadOnly());
1170     StaticDtorSection =
1171         Ctx.getCOFFSection(".CRT$XTX", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1172                                            COFF::IMAGE_SCN_MEM_READ,
1173                            SectionKind::getReadOnly());
1174   } else {
1175     StaticCtorSection = Ctx.getCOFFSection(
1176         ".ctors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1177                       COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1178         SectionKind::getData());
1179     StaticDtorSection = Ctx.getCOFFSection(
1180         ".dtors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1181                       COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1182         SectionKind::getData());
1183   }
1184 }
1185 
1186 MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
1187     unsigned Priority, const MCSymbol *KeySym) const {
1188   return getContext().getAssociativeCOFFSection(
1189       cast<MCSectionCOFF>(StaticCtorSection), KeySym, 0);
1190 }
1191 
1192 MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
1193     unsigned Priority, const MCSymbol *KeySym) const {
1194   return getContext().getAssociativeCOFFSection(
1195       cast<MCSectionCOFF>(StaticDtorSection), KeySym, 0);
1196 }
1197 
1198 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
1199     raw_ostream &OS, const GlobalValue *GV) const {
1200   emitLinkerFlagsForGlobalCOFF(OS, GV, getTargetTriple(), getMangler());
1201 }
1202 
1203 //===----------------------------------------------------------------------===//
1204 //                                  Wasm
1205 //===----------------------------------------------------------------------===//
1206 
1207 static const Comdat *getWasmComdat(const GlobalValue *GV) {
1208   const Comdat *C = GV->getComdat();
1209   if (!C)
1210     return nullptr;
1211 
1212   if (C->getSelectionKind() != Comdat::Any)
1213     report_fatal_error("Wasm COMDATs only support SelectionKind::Any, '" +
1214                        C->getName() + "' cannot be lowered.");
1215 
1216   return C;
1217 }
1218 
1219 MCSection *TargetLoweringObjectFileWasm::getExplicitSectionGlobal(
1220     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1221   llvm_unreachable("getExplicitSectionGlobal not yet implemented");
1222   return nullptr;
1223 }
1224 
1225 static MCSectionWasm *
1226 selectWasmSectionForGlobal(MCContext &Ctx, const GlobalObject *GO,
1227                            SectionKind Kind, Mangler &Mang,
1228                            const TargetMachine &TM, bool EmitUniqueSection,
1229                            unsigned Flags, unsigned *NextUniqueID) {
1230   StringRef Group = "";
1231   if (getWasmComdat(GO))
1232     llvm_unreachable("comdat not yet supported for wasm");
1233 
1234   bool UniqueSectionNames = TM.getUniqueSectionNames();
1235   SmallString<128> Name = getSectionPrefixForGlobal(Kind);
1236 
1237   if (const auto *F = dyn_cast<Function>(GO)) {
1238     const auto &OptionalPrefix = F->getSectionPrefix();
1239     if (OptionalPrefix)
1240       Name += *OptionalPrefix;
1241   }
1242 
1243   if (EmitUniqueSection && UniqueSectionNames) {
1244     Name.push_back('.');
1245     TM.getNameWithPrefix(Name, GO, Mang, true);
1246   }
1247   unsigned UniqueID = MCContext::GenericSectionID;
1248   if (EmitUniqueSection && !UniqueSectionNames) {
1249     UniqueID = *NextUniqueID;
1250     (*NextUniqueID)++;
1251   }
1252   return Ctx.getWasmSection(Name, /*Type=*/0, Flags,
1253                             Group, UniqueID);
1254 }
1255 
1256 MCSection *TargetLoweringObjectFileWasm::SelectSectionForGlobal(
1257     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1258 
1259   if (Kind.isCommon())
1260     report_fatal_error("mergable sections not supported yet on wasm");
1261 
1262   // If we have -ffunction-section or -fdata-section then we should emit the
1263   // global value to a uniqued section specifically for it.
1264   bool EmitUniqueSection = false;
1265   if (Kind.isText())
1266     EmitUniqueSection = TM.getFunctionSections();
1267   else
1268     EmitUniqueSection = TM.getDataSections();
1269   EmitUniqueSection |= GO->hasComdat();
1270 
1271   return selectWasmSectionForGlobal(getContext(), GO, Kind, getMangler(), TM,
1272                                     EmitUniqueSection, /*Flags=*/0,
1273                                     &NextUniqueID);
1274 }
1275 
1276 bool TargetLoweringObjectFileWasm::shouldPutJumpTableInFunctionSection(
1277     bool UsesLabelDifference, const Function &F) const {
1278   // We can always create relative relocations, so use another section
1279   // that can be marked non-executable.
1280   return false;
1281 }
1282 
1283 const MCExpr *TargetLoweringObjectFileWasm::lowerRelativeReference(
1284     const GlobalValue *LHS, const GlobalValue *RHS,
1285     const TargetMachine &TM) const {
1286   // We may only use a PLT-relative relocation to refer to unnamed_addr
1287   // functions.
1288   if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
1289     return nullptr;
1290 
1291   // Basic sanity checks.
1292   if (LHS->getType()->getPointerAddressSpace() != 0 ||
1293       RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
1294       RHS->isThreadLocal())
1295     return nullptr;
1296 
1297   return MCBinaryExpr::createSub(
1298       MCSymbolRefExpr::create(TM.getSymbol(LHS), MCSymbolRefExpr::VK_None,
1299                               getContext()),
1300       MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
1301 }
1302 
1303 void
1304 TargetLoweringObjectFileWasm::InitializeWasm() {
1305   // TODO: Initialize StaticCtorSection and StaticDtorSection.
1306 }
1307