xref: /llvm-project/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (revision 7a70be68650a114119f4eb8995e320520d32b6e3) 
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::Initialize(MCContext &Ctx,
95                                              const TargetMachine &TgtM) {
96   TargetLoweringObjectFile::Initialize(Ctx, TgtM);
97   TM = &TgtM;
98 }
99 
100 void TargetLoweringObjectFileELF::emitModuleMetadata(MCStreamer &Streamer,
101                                                      Module &M) const {
102   auto &C = getContext();
103 
104   if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
105     auto *S = C.getELFSection(".linker-options", ELF::SHT_LLVM_LINKER_OPTIONS,
106                               ELF::SHF_EXCLUDE);
107 
108     Streamer.SwitchSection(S);
109 
110     for (const auto &Operand : LinkerOptions->operands()) {
111       if (cast<MDNode>(Operand)->getNumOperands() != 2)
112         report_fatal_error("invalid llvm.linker.options");
113       for (const auto &Option : cast<MDNode>(Operand)->operands()) {
114         Streamer.EmitBytes(cast<MDString>(Option)->getString());
115         Streamer.EmitIntValue(0, 1);
116       }
117     }
118   }
119 
120   unsigned Version = 0;
121   unsigned Flags = 0;
122   StringRef Section;
123 
124   GetObjCImageInfo(M, Version, Flags, Section);
125   if (!Section.empty()) {
126     auto *S = C.getELFSection(Section, ELF::SHT_PROGBITS, ELF::SHF_ALLOC);
127     Streamer.SwitchSection(S);
128     Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
129     Streamer.EmitIntValue(Version, 4);
130     Streamer.EmitIntValue(Flags, 4);
131     Streamer.AddBlankLine();
132   }
133 
134   SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
135   M.getModuleFlagsMetadata(ModuleFlags);
136 
137   MDNode *CFGProfile = nullptr;
138 
139   for (const auto &MFE : ModuleFlags) {
140     StringRef Key = MFE.Key->getString();
141     if (Key == "CG Profile") {
142       CFGProfile = cast<MDNode>(MFE.Val);
143       break;
144     }
145   }
146 
147   if (!CFGProfile)
148     return;
149 
150   auto GetSym = [this](const MDOperand &MDO) -> MCSymbol * {
151     if (!MDO)
152       return nullptr;
153     auto V = cast<ValueAsMetadata>(MDO);
154     const Function *F = cast<Function>(V->getValue());
155     return TM->getSymbol(F);
156   };
157 
158   for (const auto &Edge : CFGProfile->operands()) {
159     MDNode *E = cast<MDNode>(Edge);
160     const MCSymbol *From = GetSym(E->getOperand(0));
161     const MCSymbol *To = GetSym(E->getOperand(1));
162     // Skip null functions. This can happen if functions are dead stripped after
163     // the CGProfile pass has been run.
164     if (!From || !To)
165       continue;
166     uint64_t Count = cast<ConstantAsMetadata>(E->getOperand(2))
167                          ->getValue()
168                          ->getUniqueInteger()
169                          .getZExtValue();
170     Streamer.emitCGProfileEntry(
171         MCSymbolRefExpr::create(From, MCSymbolRefExpr::VK_None, C),
172         MCSymbolRefExpr::create(To, MCSymbolRefExpr::VK_None, C), Count);
173   }
174 }
175 
176 MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
177     const GlobalValue *GV, const TargetMachine &TM,
178     MachineModuleInfo *MMI) const {
179   unsigned Encoding = getPersonalityEncoding();
180   if ((Encoding & 0x80) == DW_EH_PE_indirect)
181     return getContext().getOrCreateSymbol(StringRef("DW.ref.") +
182                                           TM.getSymbol(GV)->getName());
183   if ((Encoding & 0x70) == DW_EH_PE_absptr)
184     return TM.getSymbol(GV);
185   report_fatal_error("We do not support this DWARF encoding yet!");
186 }
187 
188 void TargetLoweringObjectFileELF::emitPersonalityValue(
189     MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
190   SmallString<64> NameData("DW.ref.");
191   NameData += Sym->getName();
192   MCSymbolELF *Label =
193       cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
194   Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
195   Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
196   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
197   MCSection *Sec = getContext().getELFNamedSection(".data", Label->getName(),
198                                                    ELF::SHT_PROGBITS, Flags, 0);
199   unsigned Size = DL.getPointerSize();
200   Streamer.SwitchSection(Sec);
201   Streamer.EmitValueToAlignment(DL.getPointerABIAlignment(0));
202   Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
203   const MCExpr *E = MCConstantExpr::create(Size, getContext());
204   Streamer.emitELFSize(Label, E);
205   Streamer.EmitLabel(Label);
206 
207   Streamer.EmitSymbolValue(Sym, Size);
208 }
209 
210 const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
211     const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
212     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
213   if (Encoding & DW_EH_PE_indirect) {
214     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
215 
216     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", TM);
217 
218     // Add information about the stub reference to ELFMMI so that the stub
219     // gets emitted by the asmprinter.
220     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
221     if (!StubSym.getPointer()) {
222       MCSymbol *Sym = TM.getSymbol(GV);
223       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
224     }
225 
226     return TargetLoweringObjectFile::
227       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
228                         Encoding & ~DW_EH_PE_indirect, Streamer);
229   }
230 
231   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
232                                                            MMI, Streamer);
233 }
234 
235 static SectionKind getELFKindForNamedSection(StringRef Name, SectionKind K) {
236   // N.B.: The defaults used in here are not the same ones used in MC.
237   // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
238   // both gas and MC will produce a section with no flags. Given
239   // section(".eh_frame") gcc will produce:
240   //
241   //   .section   .eh_frame,"a",@progbits
242 
243   if (Name == getInstrProfSectionName(IPSK_covmap, Triple::ELF,
244                                       /*AddSegmentInfo=*/false))
245     return SectionKind::getMetadata();
246 
247   if (Name.empty() || Name[0] != '.') return K;
248 
249   // Default implementation based on some magic section names.
250   if (Name == ".bss" ||
251       Name.startswith(".bss.") ||
252       Name.startswith(".gnu.linkonce.b.") ||
253       Name.startswith(".llvm.linkonce.b.") ||
254       Name == ".sbss" ||
255       Name.startswith(".sbss.") ||
256       Name.startswith(".gnu.linkonce.sb.") ||
257       Name.startswith(".llvm.linkonce.sb."))
258     return SectionKind::getBSS();
259 
260   if (Name == ".tdata" ||
261       Name.startswith(".tdata.") ||
262       Name.startswith(".gnu.linkonce.td.") ||
263       Name.startswith(".llvm.linkonce.td."))
264     return SectionKind::getThreadData();
265 
266   if (Name == ".tbss" ||
267       Name.startswith(".tbss.") ||
268       Name.startswith(".gnu.linkonce.tb.") ||
269       Name.startswith(".llvm.linkonce.tb."))
270     return SectionKind::getThreadBSS();
271 
272   return K;
273 }
274 
275 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
276   // Use SHT_NOTE for section whose name starts with ".note" to allow
277   // emitting ELF notes from C variable declaration.
278   // See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77609
279   if (Name.startswith(".note"))
280     return ELF::SHT_NOTE;
281 
282   if (Name == ".init_array")
283     return ELF::SHT_INIT_ARRAY;
284 
285   if (Name == ".fini_array")
286     return ELF::SHT_FINI_ARRAY;
287 
288   if (Name == ".preinit_array")
289     return ELF::SHT_PREINIT_ARRAY;
290 
291   if (K.isBSS() || K.isThreadBSS())
292     return ELF::SHT_NOBITS;
293 
294   return ELF::SHT_PROGBITS;
295 }
296 
297 static unsigned getELFSectionFlags(SectionKind K) {
298   unsigned Flags = 0;
299 
300   if (!K.isMetadata())
301     Flags |= ELF::SHF_ALLOC;
302 
303   if (K.isText())
304     Flags |= ELF::SHF_EXECINSTR;
305 
306   if (K.isExecuteOnly())
307     Flags |= ELF::SHF_ARM_PURECODE;
308 
309   if (K.isWriteable())
310     Flags |= ELF::SHF_WRITE;
311 
312   if (K.isThreadLocal())
313     Flags |= ELF::SHF_TLS;
314 
315   if (K.isMergeableCString() || K.isMergeableConst())
316     Flags |= ELF::SHF_MERGE;
317 
318   if (K.isMergeableCString())
319     Flags |= ELF::SHF_STRINGS;
320 
321   return Flags;
322 }
323 
324 static const Comdat *getELFComdat(const GlobalValue *GV) {
325   const Comdat *C = GV->getComdat();
326   if (!C)
327     return nullptr;
328 
329   if (C->getSelectionKind() != Comdat::Any)
330     report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
331                        C->getName() + "' cannot be lowered.");
332 
333   return C;
334 }
335 
336 static const MCSymbolELF *getAssociatedSymbol(const GlobalObject *GO,
337                                               const TargetMachine &TM) {
338   MDNode *MD = GO->getMetadata(LLVMContext::MD_associated);
339   if (!MD)
340     return nullptr;
341 
342   const MDOperand &Op = MD->getOperand(0);
343   if (!Op.get())
344     return nullptr;
345 
346   auto *VM = dyn_cast<ValueAsMetadata>(Op);
347   if (!VM)
348     report_fatal_error("MD_associated operand is not ValueAsMetadata");
349 
350   GlobalObject *OtherGO = dyn_cast<GlobalObject>(VM->getValue());
351   return OtherGO ? dyn_cast<MCSymbolELF>(TM.getSymbol(OtherGO)) : nullptr;
352 }
353 
354 MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
355     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
356   StringRef SectionName = GO->getSection();
357 
358   // Check if '#pragma clang section' name is applicable.
359   // Note that pragma directive overrides -ffunction-section, -fdata-section
360   // and so section name is exactly as user specified and not uniqued.
361   const GlobalVariable *GV = dyn_cast<GlobalVariable>(GO);
362   if (GV && GV->hasImplicitSection()) {
363     auto Attrs = GV->getAttributes();
364     if (Attrs.hasAttribute("bss-section") && Kind.isBSS()) {
365       SectionName = Attrs.getAttribute("bss-section").getValueAsString();
366     } else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()) {
367       SectionName = Attrs.getAttribute("rodata-section").getValueAsString();
368     } else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
369       SectionName = Attrs.getAttribute("data-section").getValueAsString();
370     }
371   }
372   const Function *F = dyn_cast<Function>(GO);
373   if (F && F->hasFnAttribute("implicit-section-name")) {
374     SectionName = F->getFnAttribute("implicit-section-name").getValueAsString();
375   }
376 
377   // Infer section flags from the section name if we can.
378   Kind = getELFKindForNamedSection(SectionName, Kind);
379 
380   StringRef Group = "";
381   unsigned Flags = getELFSectionFlags(Kind);
382   if (const Comdat *C = getELFComdat(GO)) {
383     Group = C->getName();
384     Flags |= ELF::SHF_GROUP;
385   }
386 
387   // A section can have at most one associated section. Put each global with
388   // MD_associated in a unique section.
389   unsigned UniqueID = MCContext::GenericSectionID;
390   const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
391   if (AssociatedSymbol) {
392     UniqueID = NextUniqueID++;
393     Flags |= ELF::SHF_LINK_ORDER;
394   }
395 
396   MCSectionELF *Section = getContext().getELFSection(
397       SectionName, getELFSectionType(SectionName, Kind), Flags,
398       /*EntrySize=*/0, Group, UniqueID, AssociatedSymbol);
399   // Make sure that we did not get some other section with incompatible sh_link.
400   // This should not be possible due to UniqueID code above.
401   assert(Section->getAssociatedSymbol() == AssociatedSymbol &&
402          "Associated symbol mismatch between sections");
403   return Section;
404 }
405 
406 /// Return the section prefix name used by options FunctionsSections and
407 /// DataSections.
408 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
409   if (Kind.isText())
410     return ".text";
411   if (Kind.isReadOnly())
412     return ".rodata";
413   if (Kind.isBSS())
414     return ".bss";
415   if (Kind.isThreadData())
416     return ".tdata";
417   if (Kind.isThreadBSS())
418     return ".tbss";
419   if (Kind.isData())
420     return ".data";
421   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
422   return ".data.rel.ro";
423 }
424 
425 static unsigned getEntrySizeForKind(SectionKind Kind) {
426   if (Kind.isMergeable1ByteCString())
427     return 1;
428   else if (Kind.isMergeable2ByteCString())
429     return 2;
430   else if (Kind.isMergeable4ByteCString())
431     return 4;
432   else if (Kind.isMergeableConst4())
433     return 4;
434   else if (Kind.isMergeableConst8())
435     return 8;
436   else if (Kind.isMergeableConst16())
437     return 16;
438   else if (Kind.isMergeableConst32())
439     return 32;
440   else {
441     // We shouldn't have mergeable C strings or mergeable constants that we
442     // didn't handle above.
443     assert(!Kind.isMergeableCString() && "unknown string width");
444     assert(!Kind.isMergeableConst() && "unknown data width");
445     return 0;
446   }
447 }
448 
449 static MCSectionELF *selectELFSectionForGlobal(
450     MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
451     const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
452     unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol) {
453 
454   StringRef Group = "";
455   if (const Comdat *C = getELFComdat(GO)) {
456     Flags |= ELF::SHF_GROUP;
457     Group = C->getName();
458   }
459 
460   // Get the section entry size based on the kind.
461   unsigned EntrySize = getEntrySizeForKind(Kind);
462 
463   SmallString<128> Name;
464   if (Kind.isMergeableCString()) {
465     // We also need alignment here.
466     // FIXME: this is getting the alignment of the character, not the
467     // alignment of the global!
468     unsigned Align = GO->getParent()->getDataLayout().getPreferredAlignment(
469         cast<GlobalVariable>(GO));
470 
471     std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
472     Name = SizeSpec + utostr(Align);
473   } else if (Kind.isMergeableConst()) {
474     Name = ".rodata.cst";
475     Name += utostr(EntrySize);
476   } else {
477     Name = getSectionPrefixForGlobal(Kind);
478   }
479 
480   if (const auto *F = dyn_cast<Function>(GO)) {
481     const auto &OptionalPrefix = F->getSectionPrefix();
482     if (OptionalPrefix)
483       Name += *OptionalPrefix;
484   }
485 
486   unsigned UniqueID = MCContext::GenericSectionID;
487   if (EmitUniqueSection) {
488     if (TM.getUniqueSectionNames()) {
489       Name.push_back('.');
490       TM.getNameWithPrefix(Name, GO, Mang, true /*MayAlwaysUsePrivate*/);
491     } else {
492       UniqueID = *NextUniqueID;
493       (*NextUniqueID)++;
494     }
495   }
496   // Use 0 as the unique ID for execute-only text.
497   if (Kind.isExecuteOnly())
498     UniqueID = 0;
499   return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags,
500                            EntrySize, Group, UniqueID, AssociatedSymbol);
501 }
502 
503 MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
504     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
505   unsigned Flags = getELFSectionFlags(Kind);
506 
507   // If we have -ffunction-section or -fdata-section then we should emit the
508   // global value to a uniqued section specifically for it.
509   bool EmitUniqueSection = false;
510   if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
511     if (Kind.isText())
512       EmitUniqueSection = TM.getFunctionSections();
513     else
514       EmitUniqueSection = TM.getDataSections();
515   }
516   EmitUniqueSection |= GO->hasComdat();
517 
518   const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
519   if (AssociatedSymbol) {
520     EmitUniqueSection = true;
521     Flags |= ELF::SHF_LINK_ORDER;
522   }
523 
524   MCSectionELF *Section = selectELFSectionForGlobal(
525       getContext(), GO, Kind, getMangler(), TM, EmitUniqueSection, Flags,
526       &NextUniqueID, AssociatedSymbol);
527   assert(Section->getAssociatedSymbol() == AssociatedSymbol);
528   return Section;
529 }
530 
531 MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
532     const Function &F, const TargetMachine &TM) const {
533   // If the function can be removed, produce a unique section so that
534   // the table doesn't prevent the removal.
535   const Comdat *C = F.getComdat();
536   bool EmitUniqueSection = TM.getFunctionSections() || C;
537   if (!EmitUniqueSection)
538     return ReadOnlySection;
539 
540   return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
541                                    getMangler(), TM, EmitUniqueSection,
542                                    ELF::SHF_ALLOC, &NextUniqueID,
543                                    /* AssociatedSymbol */ nullptr);
544 }
545 
546 bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
547     bool UsesLabelDifference, const Function &F) const {
548   // We can always create relative relocations, so use another section
549   // that can be marked non-executable.
550   return false;
551 }
552 
553 /// Given a mergeable constant with the specified size and relocation
554 /// information, return a section that it should be placed in.
555 MCSection *TargetLoweringObjectFileELF::getSectionForConstant(
556     const DataLayout &DL, SectionKind Kind, const Constant *C,
557     unsigned &Align) const {
558   if (Kind.isMergeableConst4() && MergeableConst4Section)
559     return MergeableConst4Section;
560   if (Kind.isMergeableConst8() && MergeableConst8Section)
561     return MergeableConst8Section;
562   if (Kind.isMergeableConst16() && MergeableConst16Section)
563     return MergeableConst16Section;
564   if (Kind.isMergeableConst32() && MergeableConst32Section)
565     return MergeableConst32Section;
566   if (Kind.isReadOnly())
567     return ReadOnlySection;
568 
569   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
570   return DataRelROSection;
571 }
572 
573 static MCSectionELF *getStaticStructorSection(MCContext &Ctx, bool UseInitArray,
574                                               bool IsCtor, unsigned Priority,
575                                               const MCSymbol *KeySym) {
576   std::string Name;
577   unsigned Type;
578   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
579   StringRef COMDAT = KeySym ? KeySym->getName() : "";
580 
581   if (KeySym)
582     Flags |= ELF::SHF_GROUP;
583 
584   if (UseInitArray) {
585     if (IsCtor) {
586       Type = ELF::SHT_INIT_ARRAY;
587       Name = ".init_array";
588     } else {
589       Type = ELF::SHT_FINI_ARRAY;
590       Name = ".fini_array";
591     }
592     if (Priority != 65535) {
593       Name += '.';
594       Name += utostr(Priority);
595     }
596   } else {
597     // The default scheme is .ctor / .dtor, so we have to invert the priority
598     // numbering.
599     if (IsCtor)
600       Name = ".ctors";
601     else
602       Name = ".dtors";
603     if (Priority != 65535)
604       raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
605     Type = ELF::SHT_PROGBITS;
606   }
607 
608   return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
609 }
610 
611 MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
612     unsigned Priority, const MCSymbol *KeySym) const {
613   return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
614                                   KeySym);
615 }
616 
617 MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
618     unsigned Priority, const MCSymbol *KeySym) const {
619   return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
620                                   KeySym);
621 }
622 
623 const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
624     const GlobalValue *LHS, const GlobalValue *RHS,
625     const TargetMachine &TM) const {
626   // We may only use a PLT-relative relocation to refer to unnamed_addr
627   // functions.
628   if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
629     return nullptr;
630 
631   // Basic sanity checks.
632   if (LHS->getType()->getPointerAddressSpace() != 0 ||
633       RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
634       RHS->isThreadLocal())
635     return nullptr;
636 
637   return MCBinaryExpr::createSub(
638       MCSymbolRefExpr::create(TM.getSymbol(LHS), PLTRelativeVariantKind,
639                               getContext()),
640       MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
641 }
642 
643 void
644 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
645   UseInitArray = UseInitArray_;
646   MCContext &Ctx = getContext();
647   if (!UseInitArray) {
648     StaticCtorSection = Ctx.getELFSection(".ctors", ELF::SHT_PROGBITS,
649                                           ELF::SHF_ALLOC | ELF::SHF_WRITE);
650 
651     StaticDtorSection = Ctx.getELFSection(".dtors", ELF::SHT_PROGBITS,
652                                           ELF::SHF_ALLOC | ELF::SHF_WRITE);
653     return;
654   }
655 
656   StaticCtorSection = Ctx.getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
657                                         ELF::SHF_WRITE | ELF::SHF_ALLOC);
658   StaticDtorSection = Ctx.getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
659                                         ELF::SHF_WRITE | ELF::SHF_ALLOC);
660 }
661 
662 //===----------------------------------------------------------------------===//
663 //                                 MachO
664 //===----------------------------------------------------------------------===//
665 
666 TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
667   : TargetLoweringObjectFile() {
668   SupportIndirectSymViaGOTPCRel = true;
669 }
670 
671 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
672                                                const TargetMachine &TM) {
673   TargetLoweringObjectFile::Initialize(Ctx, TM);
674   if (TM.getRelocationModel() == Reloc::Static) {
675     StaticCtorSection = Ctx.getMachOSection("__TEXT", "__constructor", 0,
676                                             SectionKind::getData());
677     StaticDtorSection = Ctx.getMachOSection("__TEXT", "__destructor", 0,
678                                             SectionKind::getData());
679   } else {
680     StaticCtorSection = Ctx.getMachOSection("__DATA", "__mod_init_func",
681                                             MachO::S_MOD_INIT_FUNC_POINTERS,
682                                             SectionKind::getData());
683     StaticDtorSection = Ctx.getMachOSection("__DATA", "__mod_term_func",
684                                             MachO::S_MOD_TERM_FUNC_POINTERS,
685                                             SectionKind::getData());
686   }
687 }
688 
689 void TargetLoweringObjectFileMachO::emitModuleMetadata(MCStreamer &Streamer,
690                                                        Module &M) const {
691   // Emit the linker options if present.
692   if (auto *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
693     for (const auto &Option : LinkerOptions->operands()) {
694       SmallVector<std::string, 4> StrOptions;
695       for (const auto &Piece : cast<MDNode>(Option)->operands())
696         StrOptions.push_back(cast<MDString>(Piece)->getString());
697       Streamer.EmitLinkerOptions(StrOptions);
698     }
699   }
700 
701   unsigned VersionVal = 0;
702   unsigned ImageInfoFlags = 0;
703   StringRef SectionVal;
704 
705   GetObjCImageInfo(M, VersionVal, ImageInfoFlags, SectionVal);
706 
707   // The section is mandatory. If we don't have it, then we don't have GC info.
708   if (SectionVal.empty())
709     return;
710 
711   StringRef Segment, Section;
712   unsigned TAA = 0, StubSize = 0;
713   bool TAAParsed;
714   std::string ErrorCode =
715     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
716                                           TAA, TAAParsed, StubSize);
717   if (!ErrorCode.empty())
718     // If invalid, report the error with report_fatal_error.
719     report_fatal_error("Invalid section specifier '" + Section + "': " +
720                        ErrorCode + ".");
721 
722   // Get the section.
723   MCSectionMachO *S = getContext().getMachOSection(
724       Segment, Section, TAA, StubSize, SectionKind::getData());
725   Streamer.SwitchSection(S);
726   Streamer.EmitLabel(getContext().
727                      getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
728   Streamer.EmitIntValue(VersionVal, 4);
729   Streamer.EmitIntValue(ImageInfoFlags, 4);
730   Streamer.AddBlankLine();
731 }
732 
733 static void checkMachOComdat(const GlobalValue *GV) {
734   const Comdat *C = GV->getComdat();
735   if (!C)
736     return;
737 
738   report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
739                      "' cannot be lowered.");
740 }
741 
742 MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
743     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
744   // Parse the section specifier and create it if valid.
745   StringRef Segment, Section;
746   unsigned TAA = 0, StubSize = 0;
747   bool TAAParsed;
748 
749   checkMachOComdat(GO);
750 
751   std::string ErrorCode =
752     MCSectionMachO::ParseSectionSpecifier(GO->getSection(), Segment, Section,
753                                           TAA, TAAParsed, StubSize);
754   if (!ErrorCode.empty()) {
755     // If invalid, report the error with report_fatal_error.
756     report_fatal_error("Global variable '" + GO->getName() +
757                        "' has an invalid section specifier '" +
758                        GO->getSection() + "': " + ErrorCode + ".");
759   }
760 
761   // Get the section.
762   MCSectionMachO *S =
763       getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
764 
765   // If TAA wasn't set by ParseSectionSpecifier() above,
766   // use the value returned by getMachOSection() as a default.
767   if (!TAAParsed)
768     TAA = S->getTypeAndAttributes();
769 
770   // Okay, now that we got the section, verify that the TAA & StubSize agree.
771   // If the user declared multiple globals with different section flags, we need
772   // to reject it here.
773   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
774     // If invalid, report the error with report_fatal_error.
775     report_fatal_error("Global variable '" + GO->getName() +
776                        "' section type or attributes does not match previous"
777                        " section specifier");
778   }
779 
780   return S;
781 }
782 
783 MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
784     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
785   checkMachOComdat(GO);
786 
787   // Handle thread local data.
788   if (Kind.isThreadBSS()) return TLSBSSSection;
789   if (Kind.isThreadData()) return TLSDataSection;
790 
791   if (Kind.isText())
792     return GO->isWeakForLinker() ? TextCoalSection : TextSection;
793 
794   // If this is weak/linkonce, put this in a coalescable section, either in text
795   // or data depending on if it is writable.
796   if (GO->isWeakForLinker()) {
797     if (Kind.isReadOnly())
798       return ConstTextCoalSection;
799     if (Kind.isReadOnlyWithRel())
800       return ConstDataCoalSection;
801     return DataCoalSection;
802   }
803 
804   // FIXME: Alignment check should be handled by section classifier.
805   if (Kind.isMergeable1ByteCString() &&
806       GO->getParent()->getDataLayout().getPreferredAlignment(
807           cast<GlobalVariable>(GO)) < 32)
808     return CStringSection;
809 
810   // Do not put 16-bit arrays in the UString section if they have an
811   // externally visible label, this runs into issues with certain linker
812   // versions.
813   if (Kind.isMergeable2ByteCString() && !GO->hasExternalLinkage() &&
814       GO->getParent()->getDataLayout().getPreferredAlignment(
815           cast<GlobalVariable>(GO)) < 32)
816     return UStringSection;
817 
818   // With MachO only variables whose corresponding symbol starts with 'l' or
819   // 'L' can be merged, so we only try merging GVs with private linkage.
820   if (GO->hasPrivateLinkage() && Kind.isMergeableConst()) {
821     if (Kind.isMergeableConst4())
822       return FourByteConstantSection;
823     if (Kind.isMergeableConst8())
824       return EightByteConstantSection;
825     if (Kind.isMergeableConst16())
826       return SixteenByteConstantSection;
827   }
828 
829   // Otherwise, if it is readonly, but not something we can specially optimize,
830   // just drop it in .const.
831   if (Kind.isReadOnly())
832     return ReadOnlySection;
833 
834   // If this is marked const, put it into a const section.  But if the dynamic
835   // linker needs to write to it, put it in the data segment.
836   if (Kind.isReadOnlyWithRel())
837     return ConstDataSection;
838 
839   // Put zero initialized globals with strong external linkage in the
840   // DATA, __common section with the .zerofill directive.
841   if (Kind.isBSSExtern())
842     return DataCommonSection;
843 
844   // Put zero initialized globals with local linkage in __DATA,__bss directive
845   // with the .zerofill directive (aka .lcomm).
846   if (Kind.isBSSLocal())
847     return DataBSSSection;
848 
849   // Otherwise, just drop the variable in the normal data section.
850   return DataSection;
851 }
852 
853 MCSection *TargetLoweringObjectFileMachO::getSectionForConstant(
854     const DataLayout &DL, SectionKind Kind, const Constant *C,
855     unsigned &Align) const {
856   // If this constant requires a relocation, we have to put it in the data
857   // segment, not in the text segment.
858   if (Kind.isData() || Kind.isReadOnlyWithRel())
859     return ConstDataSection;
860 
861   if (Kind.isMergeableConst4())
862     return FourByteConstantSection;
863   if (Kind.isMergeableConst8())
864     return EightByteConstantSection;
865   if (Kind.isMergeableConst16())
866     return SixteenByteConstantSection;
867   return ReadOnlySection;  // .const
868 }
869 
870 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
871     const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
872     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
873   // The mach-o version of this method defaults to returning a stub reference.
874 
875   if (Encoding & DW_EH_PE_indirect) {
876     MachineModuleInfoMachO &MachOMMI =
877       MMI->getObjFileInfo<MachineModuleInfoMachO>();
878 
879     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
880 
881     // Add information about the stub reference to MachOMMI so that the stub
882     // gets emitted by the asmprinter.
883     MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
884     if (!StubSym.getPointer()) {
885       MCSymbol *Sym = TM.getSymbol(GV);
886       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
887     }
888 
889     return TargetLoweringObjectFile::
890       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
891                         Encoding & ~DW_EH_PE_indirect, Streamer);
892   }
893 
894   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
895                                                            MMI, Streamer);
896 }
897 
898 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
899     const GlobalValue *GV, const TargetMachine &TM,
900     MachineModuleInfo *MMI) const {
901   // The mach-o version of this method defaults to returning a stub reference.
902   MachineModuleInfoMachO &MachOMMI =
903     MMI->getObjFileInfo<MachineModuleInfoMachO>();
904 
905   MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
906 
907   // Add information about the stub reference to MachOMMI so that the stub
908   // gets emitted by the asmprinter.
909   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
910   if (!StubSym.getPointer()) {
911     MCSymbol *Sym = TM.getSymbol(GV);
912     StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
913   }
914 
915   return SSym;
916 }
917 
918 const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
919     const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
920     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
921   // Although MachO 32-bit targets do not explicitly have a GOTPCREL relocation
922   // as 64-bit do, we replace the GOT equivalent by accessing the final symbol
923   // through a non_lazy_ptr stub instead. One advantage is that it allows the
924   // computation of deltas to final external symbols. Example:
925   //
926   //    _extgotequiv:
927   //       .long   _extfoo
928   //
929   //    _delta:
930   //       .long   _extgotequiv-_delta
931   //
932   // is transformed to:
933   //
934   //    _delta:
935   //       .long   L_extfoo$non_lazy_ptr-(_delta+0)
936   //
937   //       .section        __IMPORT,__pointers,non_lazy_symbol_pointers
938   //    L_extfoo$non_lazy_ptr:
939   //       .indirect_symbol        _extfoo
940   //       .long   0
941   //
942   MachineModuleInfoMachO &MachOMMI =
943     MMI->getObjFileInfo<MachineModuleInfoMachO>();
944   MCContext &Ctx = getContext();
945 
946   // The offset must consider the original displacement from the base symbol
947   // since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
948   Offset = -MV.getConstant();
949   const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
950 
951   // Access the final symbol via sym$non_lazy_ptr and generate the appropriated
952   // non_lazy_ptr stubs.
953   SmallString<128> Name;
954   StringRef Suffix = "$non_lazy_ptr";
955   Name += MMI->getModule()->getDataLayout().getPrivateGlobalPrefix();
956   Name += Sym->getName();
957   Name += Suffix;
958   MCSymbol *Stub = Ctx.getOrCreateSymbol(Name);
959 
960   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
961   if (!StubSym.getPointer())
962     StubSym = MachineModuleInfoImpl::
963       StubValueTy(const_cast<MCSymbol *>(Sym), true /* access indirectly */);
964 
965   const MCExpr *BSymExpr =
966     MCSymbolRefExpr::create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
967   const MCExpr *LHS =
968     MCSymbolRefExpr::create(Stub, MCSymbolRefExpr::VK_None, Ctx);
969 
970   if (!Offset)
971     return MCBinaryExpr::createSub(LHS, BSymExpr, Ctx);
972 
973   const MCExpr *RHS =
974     MCBinaryExpr::createAdd(BSymExpr, MCConstantExpr::create(Offset, Ctx), Ctx);
975   return MCBinaryExpr::createSub(LHS, RHS, Ctx);
976 }
977 
978 static bool canUsePrivateLabel(const MCAsmInfo &AsmInfo,
979                                const MCSection &Section) {
980   if (!AsmInfo.isSectionAtomizableBySymbols(Section))
981     return true;
982 
983   // If it is not dead stripped, it is safe to use private labels.
984   const MCSectionMachO &SMO = cast<MCSectionMachO>(Section);
985   if (SMO.hasAttribute(MachO::S_ATTR_NO_DEAD_STRIP))
986     return true;
987 
988   return false;
989 }
990 
991 void TargetLoweringObjectFileMachO::getNameWithPrefix(
992     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
993     const TargetMachine &TM) const {
994   bool CannotUsePrivateLabel = true;
995   if (auto *GO = GV->getBaseObject()) {
996     SectionKind GOKind = TargetLoweringObjectFile::getKindForGlobal(GO, TM);
997     const MCSection *TheSection = SectionForGlobal(GO, GOKind, TM);
998     CannotUsePrivateLabel =
999         !canUsePrivateLabel(*TM.getMCAsmInfo(), *TheSection);
1000   }
1001   getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1002 }
1003 
1004 //===----------------------------------------------------------------------===//
1005 //                                  COFF
1006 //===----------------------------------------------------------------------===//
1007 
1008 static unsigned
1009 getCOFFSectionFlags(SectionKind K, const TargetMachine &TM) {
1010   unsigned Flags = 0;
1011   bool isThumb = TM.getTargetTriple().getArch() == Triple::thumb;
1012 
1013   if (K.isMetadata())
1014     Flags |=
1015       COFF::IMAGE_SCN_MEM_DISCARDABLE;
1016   else if (K.isText())
1017     Flags |=
1018       COFF::IMAGE_SCN_MEM_EXECUTE |
1019       COFF::IMAGE_SCN_MEM_READ |
1020       COFF::IMAGE_SCN_CNT_CODE |
1021       (isThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0);
1022   else if (K.isBSS())
1023     Flags |=
1024       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
1025       COFF::IMAGE_SCN_MEM_READ |
1026       COFF::IMAGE_SCN_MEM_WRITE;
1027   else if (K.isThreadLocal())
1028     Flags |=
1029       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1030       COFF::IMAGE_SCN_MEM_READ |
1031       COFF::IMAGE_SCN_MEM_WRITE;
1032   else if (K.isReadOnly() || K.isReadOnlyWithRel())
1033     Flags |=
1034       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1035       COFF::IMAGE_SCN_MEM_READ;
1036   else if (K.isWriteable())
1037     Flags |=
1038       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1039       COFF::IMAGE_SCN_MEM_READ |
1040       COFF::IMAGE_SCN_MEM_WRITE;
1041 
1042   return Flags;
1043 }
1044 
1045 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
1046   const Comdat *C = GV->getComdat();
1047   assert(C && "expected GV to have a Comdat!");
1048 
1049   StringRef ComdatGVName = C->getName();
1050   const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
1051   if (!ComdatGV)
1052     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
1053                        "' does not exist.");
1054 
1055   if (ComdatGV->getComdat() != C)
1056     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
1057                        "' is not a key for its COMDAT.");
1058 
1059   return ComdatGV;
1060 }
1061 
1062 static int getSelectionForCOFF(const GlobalValue *GV) {
1063   if (const Comdat *C = GV->getComdat()) {
1064     const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
1065     if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
1066       ComdatKey = GA->getBaseObject();
1067     if (ComdatKey == GV) {
1068       switch (C->getSelectionKind()) {
1069       case Comdat::Any:
1070         return COFF::IMAGE_COMDAT_SELECT_ANY;
1071       case Comdat::ExactMatch:
1072         return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
1073       case Comdat::Largest:
1074         return COFF::IMAGE_COMDAT_SELECT_LARGEST;
1075       case Comdat::NoDuplicates:
1076         return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1077       case Comdat::SameSize:
1078         return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
1079       }
1080     } else {
1081       return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
1082     }
1083   }
1084   return 0;
1085 }
1086 
1087 MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
1088     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1089   int Selection = 0;
1090   unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1091   StringRef Name = GO->getSection();
1092   StringRef COMDATSymName = "";
1093   if (GO->hasComdat()) {
1094     Selection = getSelectionForCOFF(GO);
1095     const GlobalValue *ComdatGV;
1096     if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
1097       ComdatGV = getComdatGVForCOFF(GO);
1098     else
1099       ComdatGV = GO;
1100 
1101     if (!ComdatGV->hasPrivateLinkage()) {
1102       MCSymbol *Sym = TM.getSymbol(ComdatGV);
1103       COMDATSymName = Sym->getName();
1104       Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1105     } else {
1106       Selection = 0;
1107     }
1108   }
1109 
1110   return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
1111                                      Selection);
1112 }
1113 
1114 static StringRef getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
1115   if (Kind.isText())
1116     return ".text";
1117   if (Kind.isBSS())
1118     return ".bss";
1119   if (Kind.isThreadLocal())
1120     return ".tls$";
1121   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1122     return ".rdata";
1123   return ".data";
1124 }
1125 
1126 MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
1127     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1128   // If we have -ffunction-sections then we should emit the global value to a
1129   // uniqued section specifically for it.
1130   bool EmitUniquedSection;
1131   if (Kind.isText())
1132     EmitUniquedSection = TM.getFunctionSections();
1133   else
1134     EmitUniquedSection = TM.getDataSections();
1135 
1136   if ((EmitUniquedSection && !Kind.isCommon()) || GO->hasComdat()) {
1137     SmallString<256> Name = getCOFFSectionNameForUniqueGlobal(Kind);
1138 
1139     unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1140 
1141     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1142     int Selection = getSelectionForCOFF(GO);
1143     if (!Selection)
1144       Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1145     const GlobalValue *ComdatGV;
1146     if (GO->hasComdat())
1147       ComdatGV = getComdatGVForCOFF(GO);
1148     else
1149       ComdatGV = GO;
1150 
1151     unsigned UniqueID = MCContext::GenericSectionID;
1152     if (EmitUniquedSection)
1153       UniqueID = NextUniqueID++;
1154 
1155     if (!ComdatGV->hasPrivateLinkage()) {
1156       MCSymbol *Sym = TM.getSymbol(ComdatGV);
1157       StringRef COMDATSymName = Sym->getName();
1158 
1159       // Append "$symbol" to the section name when targetting mingw. The ld.bfd
1160       // COFF linker will not properly handle comdats otherwise.
1161       if (getTargetTriple().isWindowsGNUEnvironment())
1162         raw_svector_ostream(Name) << '$' << COMDATSymName;
1163 
1164       return getContext().getCOFFSection(Name, Characteristics, Kind,
1165                                          COMDATSymName, Selection, UniqueID);
1166     } else {
1167       SmallString<256> TmpData;
1168       getMangler().getNameWithPrefix(TmpData, GO, /*CannotUsePrivateLabel=*/true);
1169       return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
1170                                          Selection, UniqueID);
1171     }
1172   }
1173 
1174   if (Kind.isText())
1175     return TextSection;
1176 
1177   if (Kind.isThreadLocal())
1178     return TLSDataSection;
1179 
1180   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1181     return ReadOnlySection;
1182 
1183   // Note: we claim that common symbols are put in BSSSection, but they are
1184   // really emitted with the magic .comm directive, which creates a symbol table
1185   // entry but not a section.
1186   if (Kind.isBSS() || Kind.isCommon())
1187     return BSSSection;
1188 
1189   return DataSection;
1190 }
1191 
1192 void TargetLoweringObjectFileCOFF::getNameWithPrefix(
1193     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
1194     const TargetMachine &TM) const {
1195   bool CannotUsePrivateLabel = false;
1196   if (GV->hasPrivateLinkage() &&
1197       ((isa<Function>(GV) && TM.getFunctionSections()) ||
1198        (isa<GlobalVariable>(GV) && TM.getDataSections())))
1199     CannotUsePrivateLabel = true;
1200 
1201   getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1202 }
1203 
1204 MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
1205     const Function &F, const TargetMachine &TM) const {
1206   // If the function can be removed, produce a unique section so that
1207   // the table doesn't prevent the removal.
1208   const Comdat *C = F.getComdat();
1209   bool EmitUniqueSection = TM.getFunctionSections() || C;
1210   if (!EmitUniqueSection)
1211     return ReadOnlySection;
1212 
1213   // FIXME: we should produce a symbol for F instead.
1214   if (F.hasPrivateLinkage())
1215     return ReadOnlySection;
1216 
1217   MCSymbol *Sym = TM.getSymbol(&F);
1218   StringRef COMDATSymName = Sym->getName();
1219 
1220   SectionKind Kind = SectionKind::getReadOnly();
1221   StringRef SecName = getCOFFSectionNameForUniqueGlobal(Kind);
1222   unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1223   Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1224   unsigned UniqueID = NextUniqueID++;
1225 
1226   return getContext().getCOFFSection(
1227       SecName, Characteristics, Kind, COMDATSymName,
1228       COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
1229 }
1230 
1231 void TargetLoweringObjectFileCOFF::emitModuleMetadata(MCStreamer &Streamer,
1232                                                       Module &M) const {
1233   if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
1234     // Emit the linker options to the linker .drectve section.  According to the
1235     // spec, this section is a space-separated string containing flags for
1236     // linker.
1237     MCSection *Sec = getDrectveSection();
1238     Streamer.SwitchSection(Sec);
1239     for (const auto &Option : LinkerOptions->operands()) {
1240       for (const auto &Piece : cast<MDNode>(Option)->operands()) {
1241         // Lead with a space for consistency with our dllexport implementation.
1242         std::string Directive(" ");
1243         Directive.append(cast<MDString>(Piece)->getString());
1244         Streamer.EmitBytes(Directive);
1245       }
1246     }
1247   }
1248 
1249   unsigned Version = 0;
1250   unsigned Flags = 0;
1251   StringRef Section;
1252 
1253   GetObjCImageInfo(M, Version, Flags, Section);
1254   if (Section.empty())
1255     return;
1256 
1257   auto &C = getContext();
1258   auto *S = C.getCOFFSection(
1259       Section, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
1260       SectionKind::getReadOnly());
1261   Streamer.SwitchSection(S);
1262   Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
1263   Streamer.EmitIntValue(Version, 4);
1264   Streamer.EmitIntValue(Flags, 4);
1265   Streamer.AddBlankLine();
1266 }
1267 
1268 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
1269                                               const TargetMachine &TM) {
1270   TargetLoweringObjectFile::Initialize(Ctx, TM);
1271   const Triple &T = TM.getTargetTriple();
1272   if (T.isKnownWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
1273     StaticCtorSection =
1274         Ctx.getCOFFSection(".CRT$XCU", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1275                                            COFF::IMAGE_SCN_MEM_READ,
1276                            SectionKind::getReadOnly());
1277     StaticDtorSection =
1278         Ctx.getCOFFSection(".CRT$XTX", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1279                                            COFF::IMAGE_SCN_MEM_READ,
1280                            SectionKind::getReadOnly());
1281   } else {
1282     StaticCtorSection = Ctx.getCOFFSection(
1283         ".ctors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1284                       COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1285         SectionKind::getData());
1286     StaticDtorSection = Ctx.getCOFFSection(
1287         ".dtors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1288                       COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1289         SectionKind::getData());
1290   }
1291 }
1292 
1293 static MCSectionCOFF *getCOFFStaticStructorSection(MCContext &Ctx,
1294                                                    const Triple &T, bool IsCtor,
1295                                                    unsigned Priority,
1296                                                    const MCSymbol *KeySym,
1297                                                    MCSectionCOFF *Default) {
1298   if (T.isKnownWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment())
1299     return Ctx.getAssociativeCOFFSection(Default, KeySym, 0);
1300 
1301   std::string Name = IsCtor ? ".ctors" : ".dtors";
1302   if (Priority != 65535)
1303     raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
1304 
1305   return Ctx.getAssociativeCOFFSection(
1306       Ctx.getCOFFSection(Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1307                                    COFF::IMAGE_SCN_MEM_READ |
1308                                    COFF::IMAGE_SCN_MEM_WRITE,
1309                          SectionKind::getData()),
1310       KeySym, 0);
1311 }
1312 
1313 MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
1314     unsigned Priority, const MCSymbol *KeySym) const {
1315   return getCOFFStaticStructorSection(getContext(), getTargetTriple(), true,
1316                                       Priority, KeySym,
1317                                       cast<MCSectionCOFF>(StaticCtorSection));
1318 }
1319 
1320 MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
1321     unsigned Priority, const MCSymbol *KeySym) const {
1322   return getCOFFStaticStructorSection(getContext(), getTargetTriple(), false,
1323                                       Priority, KeySym,
1324                                       cast<MCSectionCOFF>(StaticDtorSection));
1325 }
1326 
1327 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
1328     raw_ostream &OS, const GlobalValue *GV) const {
1329   emitLinkerFlagsForGlobalCOFF(OS, GV, getTargetTriple(), getMangler());
1330 }
1331 
1332 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForUsed(
1333     raw_ostream &OS, const GlobalValue *GV) const {
1334   emitLinkerFlagsForUsedCOFF(OS, GV, getTargetTriple(), getMangler());
1335 }
1336 
1337 const MCExpr *TargetLoweringObjectFileCOFF::lowerRelativeReference(
1338     const GlobalValue *LHS, const GlobalValue *RHS,
1339     const TargetMachine &TM) const {
1340   const Triple &T = TM.getTargetTriple();
1341   if (!T.isKnownWindowsMSVCEnvironment() &&
1342       !T.isWindowsItaniumEnvironment() &&
1343       !T.isWindowsCoreCLREnvironment())
1344     return nullptr;
1345 
1346   // Our symbols should exist in address space zero, cowardly no-op if
1347   // otherwise.
1348   if (LHS->getType()->getPointerAddressSpace() != 0 ||
1349       RHS->getType()->getPointerAddressSpace() != 0)
1350     return nullptr;
1351 
1352   // Both ptrtoint instructions must wrap global objects:
1353   // - Only global variables are eligible for image relative relocations.
1354   // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
1355   // We expect __ImageBase to be a global variable without a section, externally
1356   // defined.
1357   //
1358   // It should look something like this: @__ImageBase = external constant i8
1359   if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) ||
1360       LHS->isThreadLocal() || RHS->isThreadLocal() ||
1361       RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() ||
1362       cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection())
1363     return nullptr;
1364 
1365   return MCSymbolRefExpr::create(TM.getSymbol(LHS),
1366                                  MCSymbolRefExpr::VK_COFF_IMGREL32,
1367                                  getContext());
1368 }
1369 
1370 static std::string APIntToHexString(const APInt &AI) {
1371   unsigned Width = (AI.getBitWidth() / 8) * 2;
1372   std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true);
1373   unsigned Size = HexString.size();
1374   assert(Width >= Size && "hex string is too large!");
1375   HexString.insert(HexString.begin(), Width - Size, '0');
1376 
1377   return HexString;
1378 }
1379 
1380 static std::string scalarConstantToHexString(const Constant *C) {
1381   Type *Ty = C->getType();
1382   if (isa<UndefValue>(C)) {
1383     return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits()));
1384   } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) {
1385     return APIntToHexString(CFP->getValueAPF().bitcastToAPInt());
1386   } else if (const auto *CI = dyn_cast<ConstantInt>(C)) {
1387     return APIntToHexString(CI->getValue());
1388   } else {
1389     unsigned NumElements;
1390     if (isa<VectorType>(Ty))
1391       NumElements = Ty->getVectorNumElements();
1392     else
1393       NumElements = Ty->getArrayNumElements();
1394     std::string HexString;
1395     for (int I = NumElements - 1, E = -1; I != E; --I)
1396       HexString += scalarConstantToHexString(C->getAggregateElement(I));
1397     return HexString;
1398   }
1399 }
1400 
1401 MCSection *TargetLoweringObjectFileCOFF::getSectionForConstant(
1402     const DataLayout &DL, SectionKind Kind, const Constant *C,
1403     unsigned &Align) const {
1404   if (Kind.isMergeableConst() && C &&
1405       getContext().getAsmInfo()->hasCOFFComdatConstants()) {
1406     // This creates comdat sections with the given symbol name, but unless
1407     // AsmPrinter::GetCPISymbol actually makes the symbol global, the symbol
1408     // will be created with a null storage class, which makes GNU binutils
1409     // error out.
1410     const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1411                                      COFF::IMAGE_SCN_MEM_READ |
1412                                      COFF::IMAGE_SCN_LNK_COMDAT;
1413     std::string COMDATSymName;
1414     if (Kind.isMergeableConst4()) {
1415       if (Align <= 4) {
1416         COMDATSymName = "__real@" + scalarConstantToHexString(C);
1417         Align = 4;
1418       }
1419     } else if (Kind.isMergeableConst8()) {
1420       if (Align <= 8) {
1421         COMDATSymName = "__real@" + scalarConstantToHexString(C);
1422         Align = 8;
1423       }
1424     } else if (Kind.isMergeableConst16()) {
1425       // FIXME: These may not be appropriate for non-x86 architectures.
1426       if (Align <= 16) {
1427         COMDATSymName = "__xmm@" + scalarConstantToHexString(C);
1428         Align = 16;
1429       }
1430     } else if (Kind.isMergeableConst32()) {
1431       if (Align <= 32) {
1432         COMDATSymName = "__ymm@" + scalarConstantToHexString(C);
1433         Align = 32;
1434       }
1435     }
1436 
1437     if (!COMDATSymName.empty())
1438       return getContext().getCOFFSection(".rdata", Characteristics, Kind,
1439                                          COMDATSymName,
1440                                          COFF::IMAGE_COMDAT_SELECT_ANY);
1441   }
1442 
1443   return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C, Align);
1444 }
1445 
1446 
1447 //===----------------------------------------------------------------------===//
1448 //                                  Wasm
1449 //===----------------------------------------------------------------------===//
1450 
1451 static const Comdat *getWasmComdat(const GlobalValue *GV) {
1452   const Comdat *C = GV->getComdat();
1453   if (!C)
1454     return nullptr;
1455 
1456   if (C->getSelectionKind() != Comdat::Any)
1457     report_fatal_error("WebAssembly COMDATs only support "
1458                        "SelectionKind::Any, '" + C->getName() + "' cannot be "
1459                        "lowered.");
1460 
1461   return C;
1462 }
1463 
1464 static SectionKind getWasmKindForNamedSection(StringRef Name, SectionKind K) {
1465   // If we're told we have function data, then use that.
1466   if (K.isText())
1467     return SectionKind::getText();
1468 
1469   // Otherwise, ignore whatever section type the generic impl detected and use
1470   // a plain data section.
1471   return SectionKind::getData();
1472 }
1473 
1474 MCSection *TargetLoweringObjectFileWasm::getExplicitSectionGlobal(
1475     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1476   // We don't support explict section names for functions in the wasm object
1477   // format.  Each function has to be in its own unique section.
1478   if (isa<Function>(GO)) {
1479     return SelectSectionForGlobal(GO, Kind, TM);
1480   }
1481 
1482   StringRef Name = GO->getSection();
1483 
1484   Kind = getWasmKindForNamedSection(Name, Kind);
1485 
1486   StringRef Group = "";
1487   if (const Comdat *C = getWasmComdat(GO)) {
1488     Group = C->getName();
1489   }
1490 
1491   return getContext().getWasmSection(Name, Kind, Group,
1492                                      MCContext::GenericSectionID);
1493 }
1494 
1495 static MCSectionWasm *selectWasmSectionForGlobal(
1496     MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
1497     const TargetMachine &TM, bool EmitUniqueSection, unsigned *NextUniqueID) {
1498   StringRef Group = "";
1499   if (const Comdat *C = getWasmComdat(GO)) {
1500     Group = C->getName();
1501   }
1502 
1503   bool UniqueSectionNames = TM.getUniqueSectionNames();
1504   SmallString<128> Name = getSectionPrefixForGlobal(Kind);
1505 
1506   if (const auto *F = dyn_cast<Function>(GO)) {
1507     const auto &OptionalPrefix = F->getSectionPrefix();
1508     if (OptionalPrefix)
1509       Name += *OptionalPrefix;
1510   }
1511 
1512   if (EmitUniqueSection && UniqueSectionNames) {
1513     Name.push_back('.');
1514     TM.getNameWithPrefix(Name, GO, Mang, true);
1515   }
1516   unsigned UniqueID = MCContext::GenericSectionID;
1517   if (EmitUniqueSection && !UniqueSectionNames) {
1518     UniqueID = *NextUniqueID;
1519     (*NextUniqueID)++;
1520   }
1521   return Ctx.getWasmSection(Name, Kind, Group, UniqueID);
1522 }
1523 
1524 MCSection *TargetLoweringObjectFileWasm::SelectSectionForGlobal(
1525     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1526 
1527   if (Kind.isCommon())
1528     report_fatal_error("mergable sections not supported yet on wasm");
1529 
1530   // If we have -ffunction-section or -fdata-section then we should emit the
1531   // global value to a uniqued section specifically for it.
1532   bool EmitUniqueSection = false;
1533   if (Kind.isText())
1534     EmitUniqueSection = TM.getFunctionSections();
1535   else
1536     EmitUniqueSection = TM.getDataSections();
1537   EmitUniqueSection |= GO->hasComdat();
1538 
1539   return selectWasmSectionForGlobal(getContext(), GO, Kind, getMangler(), TM,
1540                                     EmitUniqueSection, &NextUniqueID);
1541 }
1542 
1543 bool TargetLoweringObjectFileWasm::shouldPutJumpTableInFunctionSection(
1544     bool UsesLabelDifference, const Function &F) const {
1545   // We can always create relative relocations, so use another section
1546   // that can be marked non-executable.
1547   return false;
1548 }
1549 
1550 const MCExpr *TargetLoweringObjectFileWasm::lowerRelativeReference(
1551     const GlobalValue *LHS, const GlobalValue *RHS,
1552     const TargetMachine &TM) const {
1553   // We may only use a PLT-relative relocation to refer to unnamed_addr
1554   // functions.
1555   if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
1556     return nullptr;
1557 
1558   // Basic sanity checks.
1559   if (LHS->getType()->getPointerAddressSpace() != 0 ||
1560       RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
1561       RHS->isThreadLocal())
1562     return nullptr;
1563 
1564   return MCBinaryExpr::createSub(
1565       MCSymbolRefExpr::create(TM.getSymbol(LHS), MCSymbolRefExpr::VK_None,
1566                               getContext()),
1567       MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
1568 }
1569 
1570 void TargetLoweringObjectFileWasm::InitializeWasm() {
1571   StaticCtorSection =
1572       getContext().getWasmSection(".init_array", SectionKind::getData());
1573 }
1574 
1575 MCSection *TargetLoweringObjectFileWasm::getStaticCtorSection(
1576     unsigned Priority, const MCSymbol *KeySym) const {
1577   return Priority == UINT16_MAX ?
1578          StaticCtorSection :
1579          getContext().getWasmSection(".init_array." + utostr(Priority),
1580                                      SectionKind::getData());
1581 }
1582 
1583 MCSection *TargetLoweringObjectFileWasm::getStaticDtorSection(
1584     unsigned Priority, const MCSymbol *KeySym) const {
1585   llvm_unreachable("@llvm.global_dtors should have been lowered already");
1586   return nullptr;
1587 }
1588