xref: /llvm-project/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (revision fc3e62675219aa78fe084c265f7bcea6f2834033) 
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/StringExtras.h"
18 #include "llvm/ADT/Triple.h"
19 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
20 #include "llvm/IR/Constants.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/IR/DerivedTypes.h"
23 #include "llvm/IR/Function.h"
24 #include "llvm/IR/GlobalVariable.h"
25 #include "llvm/IR/Mangler.h"
26 #include "llvm/IR/Module.h"
27 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/MCExpr.h"
29 #include "llvm/MC/MCSectionCOFF.h"
30 #include "llvm/MC/MCSectionELF.h"
31 #include "llvm/MC/MCSectionMachO.h"
32 #include "llvm/MC/MCStreamer.h"
33 #include "llvm/MC/MCSymbol.h"
34 #include "llvm/Support/Dwarf.h"
35 #include "llvm/Support/ELF.h"
36 #include "llvm/Support/ErrorHandling.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include "llvm/Target/TargetLowering.h"
39 #include "llvm/Target/TargetMachine.h"
40 #include "llvm/Target/TargetSubtargetInfo.h"
41 using namespace llvm;
42 using namespace dwarf;
43 
44 //===----------------------------------------------------------------------===//
45 //                                  ELF
46 //===----------------------------------------------------------------------===//
47 
48 MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
49     const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
50     MachineModuleInfo *MMI) const {
51   unsigned Encoding = getPersonalityEncoding();
52   if ((Encoding & 0x80) == dwarf::DW_EH_PE_indirect)
53     return getContext().GetOrCreateSymbol(StringRef("DW.ref.") +
54                                           TM.getSymbol(GV, Mang)->getName());
55   if ((Encoding & 0x70) == dwarf::DW_EH_PE_absptr)
56     return TM.getSymbol(GV, Mang);
57   report_fatal_error("We do not support this DWARF encoding yet!");
58 }
59 
60 void TargetLoweringObjectFileELF::emitPersonalityValue(MCStreamer &Streamer,
61                                                        const TargetMachine &TM,
62                                                        const MCSymbol *Sym) const {
63   SmallString<64> NameData("DW.ref.");
64   NameData += Sym->getName();
65   MCSymbol *Label = getContext().GetOrCreateSymbol(NameData);
66   Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
67   Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
68   StringRef Prefix = ".data.";
69   NameData.insert(NameData.begin(), Prefix.begin(), Prefix.end());
70   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
71   const MCSection *Sec = getContext().getELFSection(NameData,
72                                                     ELF::SHT_PROGBITS,
73                                                     Flags,
74                                                     0, Label->getName());
75   unsigned Size = TM.getDataLayout()->getPointerSize();
76   Streamer.SwitchSection(Sec);
77   Streamer.EmitValueToAlignment(TM.getDataLayout()->getPointerABIAlignment());
78   Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
79   const MCExpr *E = MCConstantExpr::Create(Size, getContext());
80   Streamer.EmitELFSize(Label, E);
81   Streamer.EmitLabel(Label);
82 
83   Streamer.EmitSymbolValue(Sym, Size);
84 }
85 
86 const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
87     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
88     const TargetMachine &TM, MachineModuleInfo *MMI,
89     MCStreamer &Streamer) const {
90 
91   if (Encoding & dwarf::DW_EH_PE_indirect) {
92     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
93 
94     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", Mang, TM);
95 
96     // Add information about the stub reference to ELFMMI so that the stub
97     // gets emitted by the asmprinter.
98     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
99     if (!StubSym.getPointer()) {
100       MCSymbol *Sym = TM.getSymbol(GV, Mang);
101       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
102     }
103 
104     return TargetLoweringObjectFile::
105       getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
106                         Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
107   }
108 
109   return TargetLoweringObjectFile::
110     getTTypeGlobalReference(GV, Encoding, Mang, TM, MMI, Streamer);
111 }
112 
113 static SectionKind
114 getELFKindForNamedSection(StringRef Name, SectionKind K) {
115   // N.B.: The defaults used in here are no the same ones used in MC.
116   // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
117   // both gas and MC will produce a section with no flags. Given
118   // section(".eh_frame") gcc will produce:
119   //
120   //   .section   .eh_frame,"a",@progbits
121   if (Name.empty() || Name[0] != '.') return K;
122 
123   // Some lame default implementation based on some magic section names.
124   if (Name == ".bss" ||
125       Name.startswith(".bss.") ||
126       Name.startswith(".gnu.linkonce.b.") ||
127       Name.startswith(".llvm.linkonce.b.") ||
128       Name == ".sbss" ||
129       Name.startswith(".sbss.") ||
130       Name.startswith(".gnu.linkonce.sb.") ||
131       Name.startswith(".llvm.linkonce.sb."))
132     return SectionKind::getBSS();
133 
134   if (Name == ".tdata" ||
135       Name.startswith(".tdata.") ||
136       Name.startswith(".gnu.linkonce.td.") ||
137       Name.startswith(".llvm.linkonce.td."))
138     return SectionKind::getThreadData();
139 
140   if (Name == ".tbss" ||
141       Name.startswith(".tbss.") ||
142       Name.startswith(".gnu.linkonce.tb.") ||
143       Name.startswith(".llvm.linkonce.tb."))
144     return SectionKind::getThreadBSS();
145 
146   return K;
147 }
148 
149 
150 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
151 
152   if (Name == ".init_array")
153     return ELF::SHT_INIT_ARRAY;
154 
155   if (Name == ".fini_array")
156     return ELF::SHT_FINI_ARRAY;
157 
158   if (Name == ".preinit_array")
159     return ELF::SHT_PREINIT_ARRAY;
160 
161   if (K.isBSS() || K.isThreadBSS())
162     return ELF::SHT_NOBITS;
163 
164   return ELF::SHT_PROGBITS;
165 }
166 
167 
168 static unsigned
169 getELFSectionFlags(SectionKind K, bool InCOMDAT) {
170   unsigned Flags = 0;
171 
172   if (!K.isMetadata())
173     Flags |= ELF::SHF_ALLOC;
174 
175   if (K.isText())
176     Flags |= ELF::SHF_EXECINSTR;
177 
178   if (K.isWriteable())
179     Flags |= ELF::SHF_WRITE;
180 
181   if (K.isThreadLocal())
182     Flags |= ELF::SHF_TLS;
183 
184   // FIXME: There is nothing in ELF preventing an SHF_MERGE from being
185   // in a comdat. We just avoid it for now because we don't print
186   // those .sections correctly.
187   if (!InCOMDAT && (K.isMergeableCString() || K.isMergeableConst()))
188     Flags |= ELF::SHF_MERGE;
189 
190   if (K.isMergeableCString())
191     Flags |= ELF::SHF_STRINGS;
192 
193   return Flags;
194 }
195 
196 static const Comdat *getELFComdat(const GlobalValue *GV) {
197   const Comdat *C = GV->getComdat();
198   if (!C)
199     return nullptr;
200 
201   if (C->getSelectionKind() != Comdat::Any)
202     report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
203                        C->getName() + "' cannot be lowered.");
204 
205   return C;
206 }
207 
208 const MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
209     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
210     const TargetMachine &TM) const {
211   StringRef SectionName = GV->getSection();
212 
213   // Infer section flags from the section name if we can.
214   Kind = getELFKindForNamedSection(SectionName, Kind);
215 
216   StringRef Group = "";
217   unsigned Flags = getELFSectionFlags(Kind, GV->hasComdat());
218   if (const Comdat *C = getELFComdat(GV)) {
219     Group = C->getName();
220     Flags |= ELF::SHF_GROUP;
221   }
222   return getContext().getELFSection(SectionName,
223                                     getELFSectionType(SectionName, Kind), Flags,
224                                     /*EntrySize=*/0, Group);
225 }
226 
227 /// Return the section prefix name used by options FunctionsSections and
228 /// DataSections.
229 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
230   if (Kind.isText())
231     return ".text.";
232   if (Kind.isReadOnly())
233     return ".rodata.";
234   if (Kind.isBSS())
235     return ".bss.";
236   if (Kind.isThreadData())
237     return ".tdata.";
238   if (Kind.isThreadBSS())
239     return ".tbss.";
240   if (Kind.isDataNoRel())
241     return ".data.";
242   if (Kind.isDataRelLocal())
243     return ".data.rel.local.";
244   if (Kind.isDataRel())
245     return ".data.rel.";
246   if (Kind.isReadOnlyWithRelLocal())
247     return ".data.rel.ro.local.";
248   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
249   return ".data.rel.ro.";
250 }
251 
252 const MCSection *TargetLoweringObjectFileELF::
253 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
254                        Mangler &Mang, const TargetMachine &TM) const {
255   unsigned Flags = getELFSectionFlags(Kind, GV->hasComdat());
256 
257   // If we have -ffunction-section or -fdata-section then we should emit the
258   // global value to a uniqued section specifically for it.
259   bool EmitUniquedSection = false;
260   if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
261     if (Kind.isText())
262       EmitUniquedSection = TM.getFunctionSections();
263     else
264       EmitUniquedSection = TM.getDataSections();
265   }
266 
267   if (EmitUniquedSection || GV->hasComdat()) {
268     StringRef Prefix = getSectionPrefixForGlobal(Kind);
269 
270     SmallString<128> Name(Prefix);
271     TM.getNameWithPrefix(Name, GV, Mang, true);
272 
273     StringRef Group = "";
274     if (const Comdat *C = getELFComdat(GV)) {
275       Flags |= ELF::SHF_GROUP;
276       Group = C->getName();
277     }
278 
279     return getContext().getELFSection(
280         Name.str(), getELFSectionType(Name.str(), Kind), Flags, 0, Group);
281   }
282 
283   if (Kind.isText()) return TextSection;
284 
285   if (Kind.isMergeableCString()) {
286 
287     // We also need alignment here.
288     // FIXME: this is getting the alignment of the character, not the
289     // alignment of the global!
290     unsigned Align =
291         TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV));
292 
293     unsigned EntrySize = 1;
294     if (Kind.isMergeable2ByteCString())
295       EntrySize = 2;
296     else if (Kind.isMergeable4ByteCString())
297       EntrySize = 4;
298     else
299       assert(Kind.isMergeable1ByteCString() && "unknown string width");
300 
301     std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
302     std::string Name = SizeSpec + utostr(Align);
303     return getContext().getELFSection(
304         Name, ELF::SHT_PROGBITS,
305         ELF::SHF_ALLOC | ELF::SHF_MERGE | ELF::SHF_STRINGS, EntrySize, "");
306   }
307 
308   if (Kind.isMergeableConst()) {
309     if (Kind.isMergeableConst4() && MergeableConst4Section)
310       return MergeableConst4Section;
311     if (Kind.isMergeableConst8() && MergeableConst8Section)
312       return MergeableConst8Section;
313     if (Kind.isMergeableConst16() && MergeableConst16Section)
314       return MergeableConst16Section;
315     return ReadOnlySection;  // .const
316   }
317 
318   if (Kind.isReadOnly())             return ReadOnlySection;
319 
320   if (Kind.isThreadData())           return TLSDataSection;
321   if (Kind.isThreadBSS())            return TLSBSSSection;
322 
323   // Note: we claim that common symbols are put in BSSSection, but they are
324   // really emitted with the magic .comm directive, which creates a symbol table
325   // entry but not a section.
326   if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
327 
328   if (Kind.isDataNoRel())            return DataSection;
329   if (Kind.isDataRelLocal())         return DataRelLocalSection;
330   if (Kind.isDataRel())              return DataRelSection;
331   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
332 
333   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
334   return DataRelROSection;
335 }
336 
337 const MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
338     const Function &F, Mangler &Mang, const TargetMachine &TM) const {
339   // If the function can be removed, produce a unique section so that
340   // the table doesn't prevent the removal.
341   const Comdat *C = F.getComdat();
342   bool EmitUniqueSection = TM.getFunctionSections() || C;
343   if (!EmitUniqueSection)
344     return ReadOnlySection;
345 
346   SmallString<128> Name(".rodata.");
347   TM.getNameWithPrefix(Name, &F, Mang, true);
348 
349   unsigned Flags = ELF::SHF_ALLOC;
350   StringRef Group = "";
351   if (C) {
352     Flags |= ELF::SHF_GROUP;
353     Group = C->getName();
354   }
355 
356   return getContext().getELFSection(Name, ELF::SHT_PROGBITS, Flags, 0, Group);
357 }
358 
359 /// getSectionForConstant - Given a mergeable constant with the
360 /// specified size and relocation information, return a section that it
361 /// should be placed in.
362 const MCSection *
363 TargetLoweringObjectFileELF::getSectionForConstant(SectionKind Kind,
364                                                    const Constant *C) const {
365   if (Kind.isMergeableConst4() && MergeableConst4Section)
366     return MergeableConst4Section;
367   if (Kind.isMergeableConst8() && MergeableConst8Section)
368     return MergeableConst8Section;
369   if (Kind.isMergeableConst16() && MergeableConst16Section)
370     return MergeableConst16Section;
371   if (Kind.isReadOnly())
372     return ReadOnlySection;
373 
374   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
375   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
376   return DataRelROSection;
377 }
378 
379 static const MCSectionELF *getStaticStructorSection(MCContext &Ctx,
380                                                     bool UseInitArray,
381                                                     bool IsCtor,
382                                                     unsigned Priority,
383                                                     const MCSymbol *KeySym) {
384   std::string Name;
385   unsigned Type;
386   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
387   StringRef COMDAT = KeySym ? KeySym->getName() : "";
388 
389   if (KeySym)
390     Flags |= ELF::SHF_GROUP;
391 
392   if (UseInitArray) {
393     if (IsCtor) {
394       Type = ELF::SHT_INIT_ARRAY;
395       Name = ".init_array";
396     } else {
397       Type = ELF::SHT_FINI_ARRAY;
398       Name = ".fini_array";
399     }
400     if (Priority != 65535) {
401       Name += '.';
402       Name += utostr(Priority);
403     }
404   } else {
405     // The default scheme is .ctor / .dtor, so we have to invert the priority
406     // numbering.
407     if (IsCtor)
408       Name = ".ctors";
409     else
410       Name = ".dtors";
411     if (Priority != 65535) {
412       Name += '.';
413       Name += utostr(65535 - Priority);
414     }
415     Type = ELF::SHT_PROGBITS;
416   }
417 
418   return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
419 }
420 
421 const MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
422     unsigned Priority, const MCSymbol *KeySym) const {
423   return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
424                                   KeySym);
425 }
426 
427 const MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
428     unsigned Priority, const MCSymbol *KeySym) const {
429   return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
430                                   KeySym);
431 }
432 
433 void
434 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
435   UseInitArray = UseInitArray_;
436   if (!UseInitArray)
437     return;
438 
439   StaticCtorSection = getContext().getELFSection(
440       ".init_array", ELF::SHT_INIT_ARRAY, ELF::SHF_WRITE | ELF::SHF_ALLOC);
441   StaticDtorSection = getContext().getELFSection(
442       ".fini_array", ELF::SHT_FINI_ARRAY, ELF::SHF_WRITE | ELF::SHF_ALLOC);
443 }
444 
445 //===----------------------------------------------------------------------===//
446 //                                 MachO
447 //===----------------------------------------------------------------------===//
448 
449 /// getDepLibFromLinkerOpt - Extract the dependent library name from a linker
450 /// option string. Returns StringRef() if the option does not specify a library.
451 StringRef TargetLoweringObjectFileMachO::
452 getDepLibFromLinkerOpt(StringRef LinkerOption) const {
453   const char *LibCmd = "-l";
454   if (LinkerOption.startswith(LibCmd))
455     return LinkerOption.substr(strlen(LibCmd));
456   return StringRef();
457 }
458 
459 /// emitModuleFlags - Perform code emission for module flags.
460 void TargetLoweringObjectFileMachO::
461 emitModuleFlags(MCStreamer &Streamer,
462                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
463                 Mangler &Mang, const TargetMachine &TM) const {
464   unsigned VersionVal = 0;
465   unsigned ImageInfoFlags = 0;
466   MDNode *LinkerOptions = nullptr;
467   StringRef SectionVal;
468 
469   for (ArrayRef<Module::ModuleFlagEntry>::iterator
470          i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
471     const Module::ModuleFlagEntry &MFE = *i;
472 
473     // Ignore flags with 'Require' behavior.
474     if (MFE.Behavior == Module::Require)
475       continue;
476 
477     StringRef Key = MFE.Key->getString();
478     Metadata *Val = MFE.Val;
479 
480     if (Key == "Objective-C Image Info Version") {
481       VersionVal = mdconst::extract<ConstantInt>(Val)->getZExtValue();
482     } else if (Key == "Objective-C Garbage Collection" ||
483                Key == "Objective-C GC Only" ||
484                Key == "Objective-C Is Simulated" ||
485                Key == "Objective-C Image Swift Version") {
486       ImageInfoFlags |= mdconst::extract<ConstantInt>(Val)->getZExtValue();
487     } else if (Key == "Objective-C Image Info Section") {
488       SectionVal = cast<MDString>(Val)->getString();
489     } else if (Key == "Linker Options") {
490       LinkerOptions = cast<MDNode>(Val);
491     }
492   }
493 
494   // Emit the linker options if present.
495   if (LinkerOptions) {
496     for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
497       MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
498       SmallVector<std::string, 4> StrOptions;
499 
500       // Convert to strings.
501       for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
502         MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
503         StrOptions.push_back(MDOption->getString());
504       }
505 
506       Streamer.EmitLinkerOptions(StrOptions);
507     }
508   }
509 
510   // The section is mandatory. If we don't have it, then we don't have GC info.
511   if (SectionVal.empty()) return;
512 
513   StringRef Segment, Section;
514   unsigned TAA = 0, StubSize = 0;
515   bool TAAParsed;
516   std::string ErrorCode =
517     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
518                                           TAA, TAAParsed, StubSize);
519   if (!ErrorCode.empty())
520     // If invalid, report the error with report_fatal_error.
521     report_fatal_error("Invalid section specifier '" + Section + "': " +
522                        ErrorCode + ".");
523 
524   // Get the section.
525   const MCSectionMachO *S =
526     getContext().getMachOSection(Segment, Section, TAA, StubSize,
527                                  SectionKind::getDataNoRel());
528   Streamer.SwitchSection(S);
529   Streamer.EmitLabel(getContext().
530                      GetOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
531   Streamer.EmitIntValue(VersionVal, 4);
532   Streamer.EmitIntValue(ImageInfoFlags, 4);
533   Streamer.AddBlankLine();
534 }
535 
536 static void checkMachOComdat(const GlobalValue *GV) {
537   const Comdat *C = GV->getComdat();
538   if (!C)
539     return;
540 
541   report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
542                      "' cannot be lowered.");
543 }
544 
545 const MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
546     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
547     const TargetMachine &TM) const {
548   // Parse the section specifier and create it if valid.
549   StringRef Segment, Section;
550   unsigned TAA = 0, StubSize = 0;
551   bool TAAParsed;
552 
553   checkMachOComdat(GV);
554 
555   std::string ErrorCode =
556     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
557                                           TAA, TAAParsed, StubSize);
558   if (!ErrorCode.empty()) {
559     // If invalid, report the error with report_fatal_error.
560     report_fatal_error("Global variable '" + GV->getName() +
561                        "' has an invalid section specifier '" +
562                        GV->getSection() + "': " + ErrorCode + ".");
563   }
564 
565   // Get the section.
566   const MCSectionMachO *S =
567     getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
568 
569   // If TAA wasn't set by ParseSectionSpecifier() above,
570   // use the value returned by getMachOSection() as a default.
571   if (!TAAParsed)
572     TAA = S->getTypeAndAttributes();
573 
574   // Okay, now that we got the section, verify that the TAA & StubSize agree.
575   // If the user declared multiple globals with different section flags, we need
576   // to reject it here.
577   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
578     // If invalid, report the error with report_fatal_error.
579     report_fatal_error("Global variable '" + GV->getName() +
580                        "' section type or attributes does not match previous"
581                        " section specifier");
582   }
583 
584   return S;
585 }
586 
587 const MCSection *TargetLoweringObjectFileMachO::
588 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
589                        Mangler &Mang, const TargetMachine &TM) const {
590   checkMachOComdat(GV);
591 
592   // Handle thread local data.
593   if (Kind.isThreadBSS()) return TLSBSSSection;
594   if (Kind.isThreadData()) return TLSDataSection;
595 
596   if (Kind.isText())
597     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
598 
599   // If this is weak/linkonce, put this in a coalescable section, either in text
600   // or data depending on if it is writable.
601   if (GV->isWeakForLinker()) {
602     if (Kind.isReadOnly())
603       return ConstTextCoalSection;
604     return DataCoalSection;
605   }
606 
607   // FIXME: Alignment check should be handled by section classifier.
608   if (Kind.isMergeable1ByteCString() &&
609       TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
610     return CStringSection;
611 
612   // Do not put 16-bit arrays in the UString section if they have an
613   // externally visible label, this runs into issues with certain linker
614   // versions.
615   if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
616       TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
617     return UStringSection;
618 
619   // With MachO only variables whose corresponding symbol starts with 'l' or
620   // 'L' can be merged, so we only try merging GVs with private linkage.
621   if (GV->hasPrivateLinkage() && Kind.isMergeableConst()) {
622     if (Kind.isMergeableConst4())
623       return FourByteConstantSection;
624     if (Kind.isMergeableConst8())
625       return EightByteConstantSection;
626     if (Kind.isMergeableConst16())
627       return SixteenByteConstantSection;
628   }
629 
630   // Otherwise, if it is readonly, but not something we can specially optimize,
631   // just drop it in .const.
632   if (Kind.isReadOnly())
633     return ReadOnlySection;
634 
635   // If this is marked const, put it into a const section.  But if the dynamic
636   // linker needs to write to it, put it in the data segment.
637   if (Kind.isReadOnlyWithRel())
638     return ConstDataSection;
639 
640   // Put zero initialized globals with strong external linkage in the
641   // DATA, __common section with the .zerofill directive.
642   if (Kind.isBSSExtern())
643     return DataCommonSection;
644 
645   // Put zero initialized globals with local linkage in __DATA,__bss directive
646   // with the .zerofill directive (aka .lcomm).
647   if (Kind.isBSSLocal())
648     return DataBSSSection;
649 
650   // Otherwise, just drop the variable in the normal data section.
651   return DataSection;
652 }
653 
654 const MCSection *
655 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind,
656                                                      const Constant *C) const {
657   // If this constant requires a relocation, we have to put it in the data
658   // segment, not in the text segment.
659   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
660     return ConstDataSection;
661 
662   if (Kind.isMergeableConst4())
663     return FourByteConstantSection;
664   if (Kind.isMergeableConst8())
665     return EightByteConstantSection;
666   if (Kind.isMergeableConst16())
667     return SixteenByteConstantSection;
668   return ReadOnlySection;  // .const
669 }
670 
671 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
672     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
673     const TargetMachine &TM, MachineModuleInfo *MMI,
674     MCStreamer &Streamer) const {
675   // The mach-o version of this method defaults to returning a stub reference.
676 
677   if (Encoding & DW_EH_PE_indirect) {
678     MachineModuleInfoMachO &MachOMMI =
679       MMI->getObjFileInfo<MachineModuleInfoMachO>();
680 
681     MCSymbol *SSym =
682         getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
683 
684     // Add information about the stub reference to MachOMMI so that the stub
685     // gets emitted by the asmprinter.
686     MachineModuleInfoImpl::StubValueTy &StubSym =
687       GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
688                                   MachOMMI.getGVStubEntry(SSym);
689     if (!StubSym.getPointer()) {
690       MCSymbol *Sym = TM.getSymbol(GV, Mang);
691       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
692     }
693 
694     return TargetLoweringObjectFile::
695       getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
696                         Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
697   }
698 
699   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
700                                                            TM, MMI, Streamer);
701 }
702 
703 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
704     const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
705     MachineModuleInfo *MMI) const {
706   // The mach-o version of this method defaults to returning a stub reference.
707   MachineModuleInfoMachO &MachOMMI =
708     MMI->getObjFileInfo<MachineModuleInfoMachO>();
709 
710   MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
711 
712   // Add information about the stub reference to MachOMMI so that the stub
713   // gets emitted by the asmprinter.
714   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
715   if (!StubSym.getPointer()) {
716     MCSymbol *Sym = TM.getSymbol(GV, Mang);
717     StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
718   }
719 
720   return SSym;
721 }
722 
723 //===----------------------------------------------------------------------===//
724 //                                  COFF
725 //===----------------------------------------------------------------------===//
726 
727 static unsigned
728 getCOFFSectionFlags(SectionKind K) {
729   unsigned Flags = 0;
730 
731   if (K.isMetadata())
732     Flags |=
733       COFF::IMAGE_SCN_MEM_DISCARDABLE;
734   else if (K.isText())
735     Flags |=
736       COFF::IMAGE_SCN_MEM_EXECUTE |
737       COFF::IMAGE_SCN_MEM_READ |
738       COFF::IMAGE_SCN_CNT_CODE;
739   else if (K.isBSS())
740     Flags |=
741       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
742       COFF::IMAGE_SCN_MEM_READ |
743       COFF::IMAGE_SCN_MEM_WRITE;
744   else if (K.isThreadLocal())
745     Flags |=
746       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
747       COFF::IMAGE_SCN_MEM_READ |
748       COFF::IMAGE_SCN_MEM_WRITE;
749   else if (K.isReadOnly() || K.isReadOnlyWithRel())
750     Flags |=
751       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
752       COFF::IMAGE_SCN_MEM_READ;
753   else if (K.isWriteable())
754     Flags |=
755       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
756       COFF::IMAGE_SCN_MEM_READ |
757       COFF::IMAGE_SCN_MEM_WRITE;
758 
759   return Flags;
760 }
761 
762 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
763   const Comdat *C = GV->getComdat();
764   assert(C && "expected GV to have a Comdat!");
765 
766   StringRef ComdatGVName = C->getName();
767   const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
768   if (!ComdatGV)
769     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
770                        "' does not exist.");
771 
772   if (ComdatGV->getComdat() != C)
773     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
774                        "' is not a key for its COMDAT.");
775 
776   return ComdatGV;
777 }
778 
779 static int getSelectionForCOFF(const GlobalValue *GV) {
780   if (const Comdat *C = GV->getComdat()) {
781     const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
782     if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
783       ComdatKey = GA->getBaseObject();
784     if (ComdatKey == GV) {
785       switch (C->getSelectionKind()) {
786       case Comdat::Any:
787         return COFF::IMAGE_COMDAT_SELECT_ANY;
788       case Comdat::ExactMatch:
789         return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
790       case Comdat::Largest:
791         return COFF::IMAGE_COMDAT_SELECT_LARGEST;
792       case Comdat::NoDuplicates:
793         return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
794       case Comdat::SameSize:
795         return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
796       }
797     } else {
798       return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
799     }
800   } else if (GV->isWeakForLinker()) {
801     return COFF::IMAGE_COMDAT_SELECT_ANY;
802   }
803   return 0;
804 }
805 
806 const MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
807     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
808     const TargetMachine &TM) const {
809   int Selection = 0;
810   unsigned Characteristics = getCOFFSectionFlags(Kind);
811   StringRef Name = GV->getSection();
812   StringRef COMDATSymName = "";
813   if (GV->hasComdat()) {
814     Selection = getSelectionForCOFF(GV);
815     const GlobalValue *ComdatGV;
816     if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
817       ComdatGV = getComdatGVForCOFF(GV);
818     else
819       ComdatGV = GV;
820 
821     if (!ComdatGV->hasPrivateLinkage()) {
822       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
823       COMDATSymName = Sym->getName();
824       Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
825     } else {
826       Selection = 0;
827     }
828   }
829   return getContext().getCOFFSection(Name,
830                                      Characteristics,
831                                      Kind,
832                                      COMDATSymName,
833                                      Selection);
834 }
835 
836 static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
837   if (Kind.isText())
838     return ".text";
839   if (Kind.isBSS())
840     return ".bss";
841   if (Kind.isThreadLocal())
842     return ".tls$";
843   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
844     return ".rdata";
845   return ".data";
846 }
847 
848 
849 const MCSection *TargetLoweringObjectFileCOFF::
850 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
851                        Mangler &Mang, const TargetMachine &TM) const {
852   // If we have -ffunction-sections then we should emit the global value to a
853   // uniqued section specifically for it.
854   bool EmitUniquedSection;
855   if (Kind.isText())
856     EmitUniquedSection = TM.getFunctionSections();
857   else
858     EmitUniquedSection = TM.getDataSections();
859 
860   if ((EmitUniquedSection && !Kind.isCommon()) || GV->hasComdat()) {
861     const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
862     unsigned Characteristics = getCOFFSectionFlags(Kind);
863 
864     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
865     int Selection = getSelectionForCOFF(GV);
866     if (!Selection)
867       Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
868     const GlobalValue *ComdatGV;
869     if (GV->hasComdat())
870       ComdatGV = getComdatGVForCOFF(GV);
871     else
872       ComdatGV = GV;
873 
874     if (!ComdatGV->hasPrivateLinkage()) {
875       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
876       StringRef COMDATSymName = Sym->getName();
877       return getContext().getCOFFSection(Name, Characteristics, Kind,
878                                          COMDATSymName, Selection);
879     }
880   }
881 
882   if (Kind.isText())
883     return TextSection;
884 
885   if (Kind.isThreadLocal())
886     return TLSDataSection;
887 
888   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
889     return ReadOnlySection;
890 
891   // Note: we claim that common symbols are put in BSSSection, but they are
892   // really emitted with the magic .comm directive, which creates a symbol table
893   // entry but not a section.
894   if (Kind.isBSS() || Kind.isCommon())
895     return BSSSection;
896 
897   return DataSection;
898 }
899 
900 StringRef TargetLoweringObjectFileCOFF::
901 getDepLibFromLinkerOpt(StringRef LinkerOption) const {
902   const char *LibCmd = "/DEFAULTLIB:";
903   if (LinkerOption.startswith(LibCmd))
904     return LinkerOption.substr(strlen(LibCmd));
905   return StringRef();
906 }
907 
908 void TargetLoweringObjectFileCOFF::
909 emitModuleFlags(MCStreamer &Streamer,
910                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
911                 Mangler &Mang, const TargetMachine &TM) const {
912   MDNode *LinkerOptions = nullptr;
913 
914   // Look for the "Linker Options" flag, since it's the only one we support.
915   for (ArrayRef<Module::ModuleFlagEntry>::iterator
916        i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
917     const Module::ModuleFlagEntry &MFE = *i;
918     StringRef Key = MFE.Key->getString();
919     Metadata *Val = MFE.Val;
920     if (Key == "Linker Options") {
921       LinkerOptions = cast<MDNode>(Val);
922       break;
923     }
924   }
925   if (!LinkerOptions)
926     return;
927 
928   // Emit the linker options to the linker .drectve section.  According to the
929   // spec, this section is a space-separated string containing flags for linker.
930   const MCSection *Sec = getDrectveSection();
931   Streamer.SwitchSection(Sec);
932   for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
933     MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
934     for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
935       MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
936       // Lead with a space for consistency with our dllexport implementation.
937       std::string Directive(" ");
938       Directive.append(MDOption->getString());
939       Streamer.EmitBytes(Directive);
940     }
941   }
942 }
943 
944 const MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
945     unsigned Priority, const MCSymbol *KeySym) const {
946   return getContext().getAssociativeCOFFSection(
947       cast<MCSectionCOFF>(StaticCtorSection), KeySym);
948 }
949 
950 const MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
951     unsigned Priority, const MCSymbol *KeySym) const {
952   return getContext().getAssociativeCOFFSection(
953       cast<MCSectionCOFF>(StaticDtorSection), KeySym);
954 }
955