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                                                     SectionKind::getDataRel(),
75                                                     0, Label->getName());
76   unsigned Size = TM.getDataLayout()->getPointerSize();
77   Streamer.SwitchSection(Sec);
78   Streamer.EmitValueToAlignment(TM.getDataLayout()->getPointerABIAlignment());
79   Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
80   const MCExpr *E = MCConstantExpr::Create(Size, getContext());
81   Streamer.EmitELFSize(Label, E);
82   Streamer.EmitLabel(Label);
83 
84   Streamer.EmitSymbolValue(Sym, Size);
85 }
86 
87 const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
88     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
89     const TargetMachine &TM, MachineModuleInfo *MMI,
90     MCStreamer &Streamer) const {
91 
92   if (Encoding & dwarf::DW_EH_PE_indirect) {
93     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
94 
95     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", Mang, TM);
96 
97     // Add information about the stub reference to ELFMMI so that the stub
98     // gets emitted by the asmprinter.
99     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
100     if (!StubSym.getPointer()) {
101       MCSymbol *Sym = TM.getSymbol(GV, Mang);
102       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
103     }
104 
105     return TargetLoweringObjectFile::
106       getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
107                         Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
108   }
109 
110   return TargetLoweringObjectFile::
111     getTTypeGlobalReference(GV, Encoding, Mang, TM, MMI, Streamer);
112 }
113 
114 static SectionKind
115 getELFKindForNamedSection(StringRef Name, SectionKind K) {
116   // N.B.: The defaults used in here are no the same ones used in MC.
117   // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
118   // both gas and MC will produce a section with no flags. Given
119   // section(".eh_frame") gcc will produce:
120   //
121   //   .section   .eh_frame,"a",@progbits
122   if (Name.empty() || Name[0] != '.') return K;
123 
124   // Some lame default implementation based on some magic section names.
125   if (Name == ".bss" ||
126       Name.startswith(".bss.") ||
127       Name.startswith(".gnu.linkonce.b.") ||
128       Name.startswith(".llvm.linkonce.b.") ||
129       Name == ".sbss" ||
130       Name.startswith(".sbss.") ||
131       Name.startswith(".gnu.linkonce.sb.") ||
132       Name.startswith(".llvm.linkonce.sb."))
133     return SectionKind::getBSS();
134 
135   if (Name == ".tdata" ||
136       Name.startswith(".tdata.") ||
137       Name.startswith(".gnu.linkonce.td.") ||
138       Name.startswith(".llvm.linkonce.td."))
139     return SectionKind::getThreadData();
140 
141   if (Name == ".tbss" ||
142       Name.startswith(".tbss.") ||
143       Name.startswith(".gnu.linkonce.tb.") ||
144       Name.startswith(".llvm.linkonce.tb."))
145     return SectionKind::getThreadBSS();
146 
147   return K;
148 }
149 
150 
151 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
152 
153   if (Name == ".init_array")
154     return ELF::SHT_INIT_ARRAY;
155 
156   if (Name == ".fini_array")
157     return ELF::SHT_FINI_ARRAY;
158 
159   if (Name == ".preinit_array")
160     return ELF::SHT_PREINIT_ARRAY;
161 
162   if (K.isBSS() || K.isThreadBSS())
163     return ELF::SHT_NOBITS;
164 
165   return ELF::SHT_PROGBITS;
166 }
167 
168 
169 static unsigned
170 getELFSectionFlags(SectionKind K) {
171   unsigned Flags = 0;
172 
173   if (!K.isMetadata())
174     Flags |= ELF::SHF_ALLOC;
175 
176   if (K.isText())
177     Flags |= ELF::SHF_EXECINSTR;
178 
179   if (K.isWriteable())
180     Flags |= ELF::SHF_WRITE;
181 
182   if (K.isThreadLocal())
183     Flags |= ELF::SHF_TLS;
184 
185   // K.isMergeableConst() is left out to honour PR4650
186   if (K.isMergeableCString() || K.isMergeableConst4() ||
187       K.isMergeableConst8() || K.isMergeableConst16())
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);
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                                     Kind, /*EntrySize=*/0, Group);
225 }
226 
227 /// getSectionPrefixForGlobal - Return the section prefix name used by options
228 /// FunctionsSections and DataSections.
229 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
230   if (Kind.isText())                 return ".text.";
231   if (Kind.isReadOnly())             return ".rodata.";
232   if (Kind.isBSS())                  return ".bss.";
233 
234   if (Kind.isThreadData())           return ".tdata.";
235   if (Kind.isThreadBSS())            return ".tbss.";
236 
237   if (Kind.isDataNoRel())            return ".data.";
238   if (Kind.isDataRelLocal())         return ".data.rel.local.";
239   if (Kind.isDataRel())              return ".data.rel.";
240   if (Kind.isReadOnlyWithRelLocal()) return ".data.rel.ro.local.";
241 
242   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
243   return ".data.rel.ro.";
244 }
245 
246 const MCSection *TargetLoweringObjectFileELF::
247 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
248                        Mangler &Mang, const TargetMachine &TM) const {
249   // If we have -ffunction-section or -fdata-section then we should emit the
250   // global value to a uniqued section specifically for it.
251   bool EmitUniquedSection;
252   if (Kind.isText())
253     EmitUniquedSection = TM.getFunctionSections();
254   else
255     EmitUniquedSection = TM.getDataSections();
256 
257   // If this global is linkonce/weak and the target handles this by emitting it
258   // into a 'uniqued' section name, create and return the section now.
259   if ((EmitUniquedSection && !Kind.isCommon()) || GV->hasComdat()) {
260     StringRef Prefix = getSectionPrefixForGlobal(Kind);
261 
262     SmallString<128> Name(Prefix);
263     TM.getNameWithPrefix(Name, GV, Mang, true);
264 
265     StringRef Group = "";
266     unsigned Flags = getELFSectionFlags(Kind);
267     if (const Comdat *C = getELFComdat(GV)) {
268       Flags |= ELF::SHF_GROUP;
269       Group = C->getName();
270     }
271 
272     return getContext().getELFSection(Name.str(),
273                                       getELFSectionType(Name.str(), Kind),
274                                       Flags, Kind, 0, Group);
275   }
276 
277   if (Kind.isText()) return TextSection;
278 
279   if (Kind.isMergeable1ByteCString() ||
280       Kind.isMergeable2ByteCString() ||
281       Kind.isMergeable4ByteCString()) {
282 
283     // We also need alignment here.
284     // FIXME: this is getting the alignment of the character, not the
285     // alignment of the global!
286     unsigned Align =
287         TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV));
288 
289     const char *SizeSpec = ".rodata.str1.";
290     if (Kind.isMergeable2ByteCString())
291       SizeSpec = ".rodata.str2.";
292     else if (Kind.isMergeable4ByteCString())
293       SizeSpec = ".rodata.str4.";
294     else
295       assert(Kind.isMergeable1ByteCString() && "unknown string width");
296 
297 
298     std::string Name = SizeSpec + utostr(Align);
299     return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
300                                       ELF::SHF_ALLOC |
301                                       ELF::SHF_MERGE |
302                                       ELF::SHF_STRINGS,
303                                       Kind);
304   }
305 
306   if (Kind.isMergeableConst()) {
307     if (Kind.isMergeableConst4() && MergeableConst4Section)
308       return MergeableConst4Section;
309     if (Kind.isMergeableConst8() && MergeableConst8Section)
310       return MergeableConst8Section;
311     if (Kind.isMergeableConst16() && MergeableConst16Section)
312       return MergeableConst16Section;
313     return ReadOnlySection;  // .const
314   }
315 
316   if (Kind.isReadOnly())             return ReadOnlySection;
317 
318   if (Kind.isThreadData())           return TLSDataSection;
319   if (Kind.isThreadBSS())            return TLSBSSSection;
320 
321   // Note: we claim that common symbols are put in BSSSection, but they are
322   // really emitted with the magic .comm directive, which creates a symbol table
323   // entry but not a section.
324   if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
325 
326   if (Kind.isDataNoRel())            return DataSection;
327   if (Kind.isDataRelLocal())         return DataRelLocalSection;
328   if (Kind.isDataRel())              return DataRelSection;
329   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
330 
331   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
332   return DataRelROSection;
333 }
334 
335 /// getSectionForConstant - Given a mergeable constant with the
336 /// specified size and relocation information, return a section that it
337 /// should be placed in.
338 const MCSection *
339 TargetLoweringObjectFileELF::getSectionForConstant(SectionKind Kind,
340                                                    const Constant *C) const {
341   if (Kind.isMergeableConst4() && MergeableConst4Section)
342     return MergeableConst4Section;
343   if (Kind.isMergeableConst8() && MergeableConst8Section)
344     return MergeableConst8Section;
345   if (Kind.isMergeableConst16() && MergeableConst16Section)
346     return MergeableConst16Section;
347   if (Kind.isReadOnly())
348     return ReadOnlySection;
349 
350   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
351   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
352   return DataRelROSection;
353 }
354 
355 static const MCSectionELF *getStaticStructorSection(MCContext &Ctx,
356                                                     bool UseInitArray,
357                                                     bool IsCtor,
358                                                     unsigned Priority,
359                                                     const MCSymbol *KeySym) {
360   std::string Name;
361   unsigned Type;
362   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
363   SectionKind Kind = SectionKind::getDataRel();
364   StringRef COMDAT = KeySym ? KeySym->getName() : "";
365 
366   if (KeySym)
367     Flags |= ELF::SHF_GROUP;
368 
369   if (UseInitArray) {
370     if (IsCtor) {
371       Type = ELF::SHT_INIT_ARRAY;
372       Name = ".init_array";
373     } else {
374       Type = ELF::SHT_FINI_ARRAY;
375       Name = ".fini_array";
376     }
377     if (Priority != 65535) {
378       Name += '.';
379       Name += utostr(Priority);
380     }
381   } else {
382     // The default scheme is .ctor / .dtor, so we have to invert the priority
383     // numbering.
384     if (IsCtor)
385       Name = ".ctors";
386     else
387       Name = ".dtors";
388     if (Priority != 65535) {
389       Name += '.';
390       Name += utostr(65535 - Priority);
391     }
392     Type = ELF::SHT_PROGBITS;
393   }
394 
395   return Ctx.getELFSection(Name, Type, Flags, Kind, 0, COMDAT);
396 }
397 
398 const MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
399     unsigned Priority, const MCSymbol *KeySym) const {
400   return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
401                                   KeySym);
402 }
403 
404 const MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
405     unsigned Priority, const MCSymbol *KeySym) const {
406   return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
407                                   KeySym);
408 }
409 
410 void
411 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
412   UseInitArray = UseInitArray_;
413   if (!UseInitArray)
414     return;
415 
416   StaticCtorSection =
417     getContext().getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
418                                ELF::SHF_WRITE |
419                                ELF::SHF_ALLOC,
420                                SectionKind::getDataRel());
421   StaticDtorSection =
422     getContext().getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
423                                ELF::SHF_WRITE |
424                                ELF::SHF_ALLOC,
425                                SectionKind::getDataRel());
426 }
427 
428 //===----------------------------------------------------------------------===//
429 //                                 MachO
430 //===----------------------------------------------------------------------===//
431 
432 /// getDepLibFromLinkerOpt - Extract the dependent library name from a linker
433 /// option string. Returns StringRef() if the option does not specify a library.
434 StringRef TargetLoweringObjectFileMachO::
435 getDepLibFromLinkerOpt(StringRef LinkerOption) const {
436   const char *LibCmd = "-l";
437   if (LinkerOption.startswith(LibCmd))
438     return LinkerOption.substr(strlen(LibCmd));
439   return StringRef();
440 }
441 
442 /// emitModuleFlags - Perform code emission for module flags.
443 void TargetLoweringObjectFileMachO::
444 emitModuleFlags(MCStreamer &Streamer,
445                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
446                 Mangler &Mang, const TargetMachine &TM) const {
447   unsigned VersionVal = 0;
448   unsigned ImageInfoFlags = 0;
449   MDNode *LinkerOptions = nullptr;
450   StringRef SectionVal;
451 
452   for (ArrayRef<Module::ModuleFlagEntry>::iterator
453          i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
454     const Module::ModuleFlagEntry &MFE = *i;
455 
456     // Ignore flags with 'Require' behavior.
457     if (MFE.Behavior == Module::Require)
458       continue;
459 
460     StringRef Key = MFE.Key->getString();
461     Metadata *Val = MFE.Val;
462 
463     if (Key == "Objective-C Image Info Version") {
464       VersionVal = mdconst::extract<ConstantInt>(Val)->getZExtValue();
465     } else if (Key == "Objective-C Garbage Collection" ||
466                Key == "Objective-C GC Only" ||
467                Key == "Objective-C Is Simulated" ||
468                Key == "Objective-C Image Swift Version") {
469       ImageInfoFlags |= mdconst::extract<ConstantInt>(Val)->getZExtValue();
470     } else if (Key == "Objective-C Image Info Section") {
471       SectionVal = cast<MDString>(Val)->getString();
472     } else if (Key == "Linker Options") {
473       LinkerOptions = cast<MDNode>(Val);
474     }
475   }
476 
477   // Emit the linker options if present.
478   if (LinkerOptions) {
479     for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
480       MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
481       SmallVector<std::string, 4> StrOptions;
482 
483       // Convert to strings.
484       for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
485         MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
486         StrOptions.push_back(MDOption->getString());
487       }
488 
489       Streamer.EmitLinkerOptions(StrOptions);
490     }
491   }
492 
493   // The section is mandatory. If we don't have it, then we don't have GC info.
494   if (SectionVal.empty()) return;
495 
496   StringRef Segment, Section;
497   unsigned TAA = 0, StubSize = 0;
498   bool TAAParsed;
499   std::string ErrorCode =
500     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
501                                           TAA, TAAParsed, StubSize);
502   if (!ErrorCode.empty())
503     // If invalid, report the error with report_fatal_error.
504     report_fatal_error("Invalid section specifier '" + Section + "': " +
505                        ErrorCode + ".");
506 
507   // Get the section.
508   const MCSectionMachO *S =
509     getContext().getMachOSection(Segment, Section, TAA, StubSize,
510                                  SectionKind::getDataNoRel());
511   Streamer.SwitchSection(S);
512   Streamer.EmitLabel(getContext().
513                      GetOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
514   Streamer.EmitIntValue(VersionVal, 4);
515   Streamer.EmitIntValue(ImageInfoFlags, 4);
516   Streamer.AddBlankLine();
517 }
518 
519 static void checkMachOComdat(const GlobalValue *GV) {
520   const Comdat *C = GV->getComdat();
521   if (!C)
522     return;
523 
524   report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
525                      "' cannot be lowered.");
526 }
527 
528 const MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
529     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
530     const TargetMachine &TM) const {
531   // Parse the section specifier and create it if valid.
532   StringRef Segment, Section;
533   unsigned TAA = 0, StubSize = 0;
534   bool TAAParsed;
535 
536   checkMachOComdat(GV);
537 
538   std::string ErrorCode =
539     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
540                                           TAA, TAAParsed, StubSize);
541   if (!ErrorCode.empty()) {
542     // If invalid, report the error with report_fatal_error.
543     report_fatal_error("Global variable '" + GV->getName() +
544                        "' has an invalid section specifier '" +
545                        GV->getSection() + "': " + ErrorCode + ".");
546   }
547 
548   // Get the section.
549   const MCSectionMachO *S =
550     getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
551 
552   // If TAA wasn't set by ParseSectionSpecifier() above,
553   // use the value returned by getMachOSection() as a default.
554   if (!TAAParsed)
555     TAA = S->getTypeAndAttributes();
556 
557   // Okay, now that we got the section, verify that the TAA & StubSize agree.
558   // If the user declared multiple globals with different section flags, we need
559   // to reject it here.
560   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
561     // If invalid, report the error with report_fatal_error.
562     report_fatal_error("Global variable '" + GV->getName() +
563                        "' section type or attributes does not match previous"
564                        " section specifier");
565   }
566 
567   return S;
568 }
569 
570 const MCSection *TargetLoweringObjectFileMachO::
571 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
572                        Mangler &Mang, const TargetMachine &TM) const {
573   checkMachOComdat(GV);
574 
575   // Handle thread local data.
576   if (Kind.isThreadBSS()) return TLSBSSSection;
577   if (Kind.isThreadData()) return TLSDataSection;
578 
579   if (Kind.isText())
580     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
581 
582   // If this is weak/linkonce, put this in a coalescable section, either in text
583   // or data depending on if it is writable.
584   if (GV->isWeakForLinker()) {
585     if (Kind.isReadOnly())
586       return ConstTextCoalSection;
587     return DataCoalSection;
588   }
589 
590   // FIXME: Alignment check should be handled by section classifier.
591   if (Kind.isMergeable1ByteCString() &&
592       TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
593     return CStringSection;
594 
595   // Do not put 16-bit arrays in the UString section if they have an
596   // externally visible label, this runs into issues with certain linker
597   // versions.
598   if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
599       TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
600     return UStringSection;
601 
602   // With MachO only variables whose corresponding symbol starts with 'l' or
603   // 'L' can be merged, so we only try merging GVs with private linkage.
604   if (GV->hasPrivateLinkage() && Kind.isMergeableConst()) {
605     if (Kind.isMergeableConst4())
606       return FourByteConstantSection;
607     if (Kind.isMergeableConst8())
608       return EightByteConstantSection;
609     if (Kind.isMergeableConst16())
610       return SixteenByteConstantSection;
611   }
612 
613   // Otherwise, if it is readonly, but not something we can specially optimize,
614   // just drop it in .const.
615   if (Kind.isReadOnly())
616     return ReadOnlySection;
617 
618   // If this is marked const, put it into a const section.  But if the dynamic
619   // linker needs to write to it, put it in the data segment.
620   if (Kind.isReadOnlyWithRel())
621     return ConstDataSection;
622 
623   // Put zero initialized globals with strong external linkage in the
624   // DATA, __common section with the .zerofill directive.
625   if (Kind.isBSSExtern())
626     return DataCommonSection;
627 
628   // Put zero initialized globals with local linkage in __DATA,__bss directive
629   // with the .zerofill directive (aka .lcomm).
630   if (Kind.isBSSLocal())
631     return DataBSSSection;
632 
633   // Otherwise, just drop the variable in the normal data section.
634   return DataSection;
635 }
636 
637 const MCSection *
638 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind,
639                                                      const Constant *C) const {
640   // If this constant requires a relocation, we have to put it in the data
641   // segment, not in the text segment.
642   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
643     return ConstDataSection;
644 
645   if (Kind.isMergeableConst4())
646     return FourByteConstantSection;
647   if (Kind.isMergeableConst8())
648     return EightByteConstantSection;
649   if (Kind.isMergeableConst16())
650     return SixteenByteConstantSection;
651   return ReadOnlySection;  // .const
652 }
653 
654 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
655     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
656     const TargetMachine &TM, MachineModuleInfo *MMI,
657     MCStreamer &Streamer) const {
658   // The mach-o version of this method defaults to returning a stub reference.
659 
660   if (Encoding & DW_EH_PE_indirect) {
661     MachineModuleInfoMachO &MachOMMI =
662       MMI->getObjFileInfo<MachineModuleInfoMachO>();
663 
664     MCSymbol *SSym =
665         getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
666 
667     // Add information about the stub reference to MachOMMI so that the stub
668     // gets emitted by the asmprinter.
669     MachineModuleInfoImpl::StubValueTy &StubSym =
670       GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
671                                   MachOMMI.getGVStubEntry(SSym);
672     if (!StubSym.getPointer()) {
673       MCSymbol *Sym = TM.getSymbol(GV, Mang);
674       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
675     }
676 
677     return TargetLoweringObjectFile::
678       getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
679                         Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
680   }
681 
682   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
683                                                            TM, MMI, Streamer);
684 }
685 
686 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
687     const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
688     MachineModuleInfo *MMI) const {
689   // The mach-o version of this method defaults to returning a stub reference.
690   MachineModuleInfoMachO &MachOMMI =
691     MMI->getObjFileInfo<MachineModuleInfoMachO>();
692 
693   MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
694 
695   // Add information about the stub reference to MachOMMI so that the stub
696   // gets emitted by the asmprinter.
697   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
698   if (!StubSym.getPointer()) {
699     MCSymbol *Sym = TM.getSymbol(GV, Mang);
700     StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
701   }
702 
703   return SSym;
704 }
705 
706 //===----------------------------------------------------------------------===//
707 //                                  COFF
708 //===----------------------------------------------------------------------===//
709 
710 static unsigned
711 getCOFFSectionFlags(SectionKind K) {
712   unsigned Flags = 0;
713 
714   if (K.isMetadata())
715     Flags |=
716       COFF::IMAGE_SCN_MEM_DISCARDABLE;
717   else if (K.isText())
718     Flags |=
719       COFF::IMAGE_SCN_MEM_EXECUTE |
720       COFF::IMAGE_SCN_MEM_READ |
721       COFF::IMAGE_SCN_CNT_CODE;
722   else if (K.isBSS())
723     Flags |=
724       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
725       COFF::IMAGE_SCN_MEM_READ |
726       COFF::IMAGE_SCN_MEM_WRITE;
727   else if (K.isThreadLocal())
728     Flags |=
729       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
730       COFF::IMAGE_SCN_MEM_READ |
731       COFF::IMAGE_SCN_MEM_WRITE;
732   else if (K.isReadOnly() || K.isReadOnlyWithRel())
733     Flags |=
734       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
735       COFF::IMAGE_SCN_MEM_READ;
736   else if (K.isWriteable())
737     Flags |=
738       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
739       COFF::IMAGE_SCN_MEM_READ |
740       COFF::IMAGE_SCN_MEM_WRITE;
741 
742   return Flags;
743 }
744 
745 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
746   const Comdat *C = GV->getComdat();
747   assert(C && "expected GV to have a Comdat!");
748 
749   StringRef ComdatGVName = C->getName();
750   const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
751   if (!ComdatGV)
752     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
753                        "' does not exist.");
754 
755   if (ComdatGV->getComdat() != C)
756     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
757                        "' is not a key for its COMDAT.");
758 
759   return ComdatGV;
760 }
761 
762 static int getSelectionForCOFF(const GlobalValue *GV) {
763   if (const Comdat *C = GV->getComdat()) {
764     const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
765     if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
766       ComdatKey = GA->getBaseObject();
767     if (ComdatKey == GV) {
768       switch (C->getSelectionKind()) {
769       case Comdat::Any:
770         return COFF::IMAGE_COMDAT_SELECT_ANY;
771       case Comdat::ExactMatch:
772         return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
773       case Comdat::Largest:
774         return COFF::IMAGE_COMDAT_SELECT_LARGEST;
775       case Comdat::NoDuplicates:
776         return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
777       case Comdat::SameSize:
778         return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
779       }
780     } else {
781       return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
782     }
783   } else if (GV->isWeakForLinker()) {
784     return COFF::IMAGE_COMDAT_SELECT_ANY;
785   }
786   return 0;
787 }
788 
789 const MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
790     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
791     const TargetMachine &TM) const {
792   int Selection = 0;
793   unsigned Characteristics = getCOFFSectionFlags(Kind);
794   StringRef Name = GV->getSection();
795   StringRef COMDATSymName = "";
796   if (GV->hasComdat()) {
797     Selection = getSelectionForCOFF(GV);
798     const GlobalValue *ComdatGV;
799     if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
800       ComdatGV = getComdatGVForCOFF(GV);
801     else
802       ComdatGV = GV;
803 
804     if (!ComdatGV->hasPrivateLinkage()) {
805       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
806       COMDATSymName = Sym->getName();
807       Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
808     } else {
809       Selection = 0;
810     }
811   }
812   return getContext().getCOFFSection(Name,
813                                      Characteristics,
814                                      Kind,
815                                      COMDATSymName,
816                                      Selection);
817 }
818 
819 static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
820   if (Kind.isText())
821     return ".text";
822   if (Kind.isBSS())
823     return ".bss";
824   if (Kind.isThreadLocal())
825     return ".tls$";
826   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
827     return ".rdata";
828   return ".data";
829 }
830 
831 
832 const MCSection *TargetLoweringObjectFileCOFF::
833 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
834                        Mangler &Mang, const TargetMachine &TM) const {
835   // If we have -ffunction-sections then we should emit the global value to a
836   // uniqued section specifically for it.
837   bool EmitUniquedSection;
838   if (Kind.isText())
839     EmitUniquedSection = TM.getFunctionSections();
840   else
841     EmitUniquedSection = TM.getDataSections();
842 
843   if ((EmitUniquedSection && !Kind.isCommon()) || GV->hasComdat()) {
844     const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
845     unsigned Characteristics = getCOFFSectionFlags(Kind);
846 
847     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
848     int Selection = getSelectionForCOFF(GV);
849     if (!Selection)
850       Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
851     const GlobalValue *ComdatGV;
852     if (GV->hasComdat())
853       ComdatGV = getComdatGVForCOFF(GV);
854     else
855       ComdatGV = GV;
856 
857     if (!ComdatGV->hasPrivateLinkage()) {
858       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
859       StringRef COMDATSymName = Sym->getName();
860       return getContext().getCOFFSection(Name, Characteristics, Kind,
861                                          COMDATSymName, Selection);
862     }
863   }
864 
865   if (Kind.isText())
866     return TextSection;
867 
868   if (Kind.isThreadLocal())
869     return TLSDataSection;
870 
871   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
872     return ReadOnlySection;
873 
874   // Note: we claim that common symbols are put in BSSSection, but they are
875   // really emitted with the magic .comm directive, which creates a symbol table
876   // entry but not a section.
877   if (Kind.isBSS() || Kind.isCommon())
878     return BSSSection;
879 
880   return DataSection;
881 }
882 
883 StringRef TargetLoweringObjectFileCOFF::
884 getDepLibFromLinkerOpt(StringRef LinkerOption) const {
885   const char *LibCmd = "/DEFAULTLIB:";
886   if (LinkerOption.startswith(LibCmd))
887     return LinkerOption.substr(strlen(LibCmd));
888   return StringRef();
889 }
890 
891 void TargetLoweringObjectFileCOFF::
892 emitModuleFlags(MCStreamer &Streamer,
893                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
894                 Mangler &Mang, const TargetMachine &TM) const {
895   MDNode *LinkerOptions = nullptr;
896 
897   // Look for the "Linker Options" flag, since it's the only one we support.
898   for (ArrayRef<Module::ModuleFlagEntry>::iterator
899        i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
900     const Module::ModuleFlagEntry &MFE = *i;
901     StringRef Key = MFE.Key->getString();
902     Metadata *Val = MFE.Val;
903     if (Key == "Linker Options") {
904       LinkerOptions = cast<MDNode>(Val);
905       break;
906     }
907   }
908   if (!LinkerOptions)
909     return;
910 
911   // Emit the linker options to the linker .drectve section.  According to the
912   // spec, this section is a space-separated string containing flags for linker.
913   const MCSection *Sec = getDrectveSection();
914   Streamer.SwitchSection(Sec);
915   for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
916     MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
917     for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
918       MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
919       StringRef Op = MDOption->getString();
920       // Lead with a space for consistency with our dllexport implementation.
921       std::string Escaped(" ");
922       if (!Op.startswith("\"") && (Op.find(" ") != StringRef::npos)) {
923         // The PE-COFF spec says args with spaces must be quoted.  It doesn't say
924         // how to escape quotes, but it probably uses this algorithm:
925         // http://msdn.microsoft.com/en-us/library/17w5ykft(v=vs.85).aspx
926         // FIXME: Reuse escaping code from Support/Windows/Program.inc
927         Escaped.push_back('\"');
928         Escaped.append(Op);
929         Escaped.push_back('\"');
930       } else {
931         Escaped.append(Op);
932       }
933       Streamer.EmitBytes(Escaped);
934     }
935   }
936 }
937 
938 const MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
939     unsigned Priority, const MCSymbol *KeySym) const {
940   return getContext().getAssociativeCOFFSection(
941       cast<MCSectionCOFF>(StaticCtorSection), KeySym);
942 }
943 
944 const MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
945     unsigned Priority, const MCSymbol *KeySym) const {
946   return getContext().getAssociativeCOFFSection(
947       cast<MCSectionCOFF>(StaticDtorSection), KeySym);
948 }
949