xref: /llvm-project/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (revision fad1639a12a60735545a4d59a35c82841131a51a) 
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.getSubtargetImpl()->getDataLayout()->getPointerSize();
77   Streamer.SwitchSection(Sec);
78   Streamer.EmitValueToAlignment(
79       TM.getSubtargetImpl()->getDataLayout()->getPointerABIAlignment());
80   Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
81   const MCExpr *E = MCConstantExpr::Create(Size, getContext());
82   Streamer.EmitELFSize(Label, E);
83   Streamer.EmitLabel(Label);
84 
85   Streamer.EmitSymbolValue(Sym, Size);
86 }
87 
88 const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
89     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
90     const TargetMachine &TM, MachineModuleInfo *MMI,
91     MCStreamer &Streamer) const {
92 
93   if (Encoding & dwarf::DW_EH_PE_indirect) {
94     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
95 
96     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", Mang, TM);
97 
98     // Add information about the stub reference to ELFMMI so that the stub
99     // gets emitted by the asmprinter.
100     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
101     if (!StubSym.getPointer()) {
102       MCSymbol *Sym = TM.getSymbol(GV, Mang);
103       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
104     }
105 
106     return TargetLoweringObjectFile::
107       getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
108                         Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
109   }
110 
111   return TargetLoweringObjectFile::
112     getTTypeGlobalReference(GV, Encoding, Mang, TM, MMI, Streamer);
113 }
114 
115 static SectionKind
116 getELFKindForNamedSection(StringRef Name, SectionKind K) {
117   // N.B.: The defaults used in here are no the same ones used in MC.
118   // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
119   // both gas and MC will produce a section with no flags. Given
120   // section(".eh_frame") gcc will produce:
121   //
122   //   .section   .eh_frame,"a",@progbits
123   if (Name.empty() || Name[0] != '.') return K;
124 
125   // Some lame default implementation based on some magic section names.
126   if (Name == ".bss" ||
127       Name.startswith(".bss.") ||
128       Name.startswith(".gnu.linkonce.b.") ||
129       Name.startswith(".llvm.linkonce.b.") ||
130       Name == ".sbss" ||
131       Name.startswith(".sbss.") ||
132       Name.startswith(".gnu.linkonce.sb.") ||
133       Name.startswith(".llvm.linkonce.sb."))
134     return SectionKind::getBSS();
135 
136   if (Name == ".tdata" ||
137       Name.startswith(".tdata.") ||
138       Name.startswith(".gnu.linkonce.td.") ||
139       Name.startswith(".llvm.linkonce.td."))
140     return SectionKind::getThreadData();
141 
142   if (Name == ".tbss" ||
143       Name.startswith(".tbss.") ||
144       Name.startswith(".gnu.linkonce.tb.") ||
145       Name.startswith(".llvm.linkonce.tb."))
146     return SectionKind::getThreadBSS();
147 
148   return K;
149 }
150 
151 
152 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
153 
154   if (Name == ".init_array")
155     return ELF::SHT_INIT_ARRAY;
156 
157   if (Name == ".fini_array")
158     return ELF::SHT_FINI_ARRAY;
159 
160   if (Name == ".preinit_array")
161     return ELF::SHT_PREINIT_ARRAY;
162 
163   if (K.isBSS() || K.isThreadBSS())
164     return ELF::SHT_NOBITS;
165 
166   return ELF::SHT_PROGBITS;
167 }
168 
169 
170 static unsigned
171 getELFSectionFlags(SectionKind K) {
172   unsigned Flags = 0;
173 
174   if (!K.isMetadata())
175     Flags |= ELF::SHF_ALLOC;
176 
177   if (K.isText())
178     Flags |= ELF::SHF_EXECINSTR;
179 
180   if (K.isWriteable())
181     Flags |= ELF::SHF_WRITE;
182 
183   if (K.isThreadLocal())
184     Flags |= ELF::SHF_TLS;
185 
186   // K.isMergeableConst() is left out to honour PR4650
187   if (K.isMergeableCString() || K.isMergeableConst4() ||
188       K.isMergeableConst8() || K.isMergeableConst16())
189     Flags |= ELF::SHF_MERGE;
190 
191   if (K.isMergeableCString())
192     Flags |= ELF::SHF_STRINGS;
193 
194   return Flags;
195 }
196 
197 static const Comdat *getELFComdat(const GlobalValue *GV) {
198   const Comdat *C = GV->getComdat();
199   if (!C)
200     return nullptr;
201 
202   if (C->getSelectionKind() != Comdat::Any)
203     report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
204                        C->getName() + "' cannot be lowered.");
205 
206   return C;
207 }
208 
209 const MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
210     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
211     const TargetMachine &TM) const {
212   StringRef SectionName = GV->getSection();
213 
214   // Infer section flags from the section name if we can.
215   Kind = getELFKindForNamedSection(SectionName, Kind);
216 
217   StringRef Group = "";
218   unsigned Flags = getELFSectionFlags(Kind);
219   if (const Comdat *C = getELFComdat(GV)) {
220     Group = C->getName();
221     Flags |= ELF::SHF_GROUP;
222   }
223   return getContext().getELFSection(SectionName,
224                                     getELFSectionType(SectionName, Kind), Flags,
225                                     Kind, /*EntrySize=*/0, Group);
226 }
227 
228 /// getSectionPrefixForGlobal - Return the section prefix name used by options
229 /// FunctionsSections and DataSections.
230 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
231   if (Kind.isText())                 return ".text.";
232   if (Kind.isReadOnly())             return ".rodata.";
233   if (Kind.isBSS())                  return ".bss.";
234 
235   if (Kind.isThreadData())           return ".tdata.";
236   if (Kind.isThreadBSS())            return ".tbss.";
237 
238   if (Kind.isDataNoRel())            return ".data.";
239   if (Kind.isDataRelLocal())         return ".data.rel.local.";
240   if (Kind.isDataRel())              return ".data.rel.";
241   if (Kind.isReadOnlyWithRelLocal()) return ".data.rel.ro.local.";
242 
243   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
244   return ".data.rel.ro.";
245 }
246 
247 const MCSection *TargetLoweringObjectFileELF::
248 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
249                        Mangler &Mang, const TargetMachine &TM) const {
250   // If we have -ffunction-section or -fdata-section then we should emit the
251   // global value to a uniqued section specifically for it.
252   bool EmitUniquedSection;
253   if (Kind.isText())
254     EmitUniquedSection = TM.getFunctionSections();
255   else
256     EmitUniquedSection = TM.getDataSections();
257 
258   // If this global is linkonce/weak and the target handles this by emitting it
259   // into a 'uniqued' section name, create and return the section now.
260   if ((EmitUniquedSection && !Kind.isCommon()) || GV->hasComdat()) {
261     StringRef Prefix = getSectionPrefixForGlobal(Kind);
262 
263     SmallString<128> Name(Prefix);
264     TM.getNameWithPrefix(Name, GV, Mang, true);
265 
266     StringRef Group = "";
267     unsigned Flags = getELFSectionFlags(Kind);
268     if (const Comdat *C = getELFComdat(GV)) {
269       Flags |= ELF::SHF_GROUP;
270       Group = C->getName();
271     }
272 
273     return getContext().getELFSection(Name.str(),
274                                       getELFSectionType(Name.str(), Kind),
275                                       Flags, Kind, 0, Group);
276   }
277 
278   if (Kind.isText()) return TextSection;
279 
280   if (Kind.isMergeable1ByteCString() ||
281       Kind.isMergeable2ByteCString() ||
282       Kind.isMergeable4ByteCString()) {
283 
284     // We also need alignment here.
285     // FIXME: this is getting the alignment of the character, not the
286     // alignment of the global!
287     unsigned Align =
288         TM.getSubtargetImpl()->getDataLayout()->getPreferredAlignment(
289             cast<GlobalVariable>(GV));
290 
291     const char *SizeSpec = ".rodata.str1.";
292     if (Kind.isMergeable2ByteCString())
293       SizeSpec = ".rodata.str2.";
294     else if (Kind.isMergeable4ByteCString())
295       SizeSpec = ".rodata.str4.";
296     else
297       assert(Kind.isMergeable1ByteCString() && "unknown string width");
298 
299 
300     std::string Name = SizeSpec + utostr(Align);
301     return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
302                                       ELF::SHF_ALLOC |
303                                       ELF::SHF_MERGE |
304                                       ELF::SHF_STRINGS,
305                                       Kind);
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 /// getSectionForConstant - Given a mergeable constant with the
338 /// specified size and relocation information, return a section that it
339 /// should be placed in.
340 const MCSection *
341 TargetLoweringObjectFileELF::getSectionForConstant(SectionKind Kind,
342                                                    const Constant *C) const {
343   if (Kind.isMergeableConst4() && MergeableConst4Section)
344     return MergeableConst4Section;
345   if (Kind.isMergeableConst8() && MergeableConst8Section)
346     return MergeableConst8Section;
347   if (Kind.isMergeableConst16() && MergeableConst16Section)
348     return MergeableConst16Section;
349   if (Kind.isReadOnly())
350     return ReadOnlySection;
351 
352   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
353   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
354   return DataRelROSection;
355 }
356 
357 static const MCSectionELF *getStaticStructorSection(MCContext &Ctx,
358                                                     bool UseInitArray,
359                                                     bool IsCtor,
360                                                     unsigned Priority,
361                                                     const MCSymbol *KeySym) {
362   std::string Name;
363   unsigned Type;
364   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
365   SectionKind Kind = SectionKind::getDataRel();
366   StringRef COMDAT = KeySym ? KeySym->getName() : "";
367 
368   if (KeySym)
369     Flags |= ELF::SHF_GROUP;
370 
371   if (UseInitArray) {
372     if (IsCtor) {
373       Type = ELF::SHT_INIT_ARRAY;
374       Name = ".init_array";
375     } else {
376       Type = ELF::SHT_FINI_ARRAY;
377       Name = ".fini_array";
378     }
379     if (Priority != 65535) {
380       Name += '.';
381       Name += utostr(Priority);
382     }
383   } else {
384     // The default scheme is .ctor / .dtor, so we have to invert the priority
385     // numbering.
386     if (IsCtor)
387       Name = ".ctors";
388     else
389       Name = ".dtors";
390     if (Priority != 65535) {
391       Name += '.';
392       Name += utostr(65535 - Priority);
393     }
394     Type = ELF::SHT_PROGBITS;
395   }
396 
397   return Ctx.getELFSection(Name, Type, Flags, Kind, 0, COMDAT);
398 }
399 
400 const MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
401     unsigned Priority, const MCSymbol *KeySym) const {
402   return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
403                                   KeySym);
404 }
405 
406 const MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
407     unsigned Priority, const MCSymbol *KeySym) const {
408   return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
409                                   KeySym);
410 }
411 
412 void
413 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
414   UseInitArray = UseInitArray_;
415   if (!UseInitArray)
416     return;
417 
418   StaticCtorSection =
419     getContext().getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
420                                ELF::SHF_WRITE |
421                                ELF::SHF_ALLOC,
422                                SectionKind::getDataRel());
423   StaticDtorSection =
424     getContext().getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
425                                ELF::SHF_WRITE |
426                                ELF::SHF_ALLOC,
427                                SectionKind::getDataRel());
428 }
429 
430 //===----------------------------------------------------------------------===//
431 //                                 MachO
432 //===----------------------------------------------------------------------===//
433 
434 /// getDepLibFromLinkerOpt - Extract the dependent library name from a linker
435 /// option string. Returns StringRef() if the option does not specify a library.
436 StringRef TargetLoweringObjectFileMachO::
437 getDepLibFromLinkerOpt(StringRef LinkerOption) const {
438   const char *LibCmd = "-l";
439   if (LinkerOption.startswith(LibCmd))
440     return LinkerOption.substr(strlen(LibCmd));
441   return StringRef();
442 }
443 
444 /// emitModuleFlags - Perform code emission for module flags.
445 void TargetLoweringObjectFileMachO::
446 emitModuleFlags(MCStreamer &Streamer,
447                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
448                 Mangler &Mang, const TargetMachine &TM) const {
449   unsigned VersionVal = 0;
450   unsigned ImageInfoFlags = 0;
451   MDNode *LinkerOptions = nullptr;
452   StringRef SectionVal;
453 
454   for (ArrayRef<Module::ModuleFlagEntry>::iterator
455          i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
456     const Module::ModuleFlagEntry &MFE = *i;
457 
458     // Ignore flags with 'Require' behavior.
459     if (MFE.Behavior == Module::Require)
460       continue;
461 
462     StringRef Key = MFE.Key->getString();
463     Metadata *Val = MFE.Val;
464 
465     if (Key == "Objective-C Image Info Version") {
466       VersionVal = mdconst::extract<ConstantInt>(Val)->getZExtValue();
467     } else if (Key == "Objective-C Garbage Collection" ||
468                Key == "Objective-C GC Only" ||
469                Key == "Objective-C Is Simulated" ||
470                Key == "Objective-C Image Swift Version") {
471       ImageInfoFlags |= mdconst::extract<ConstantInt>(Val)->getZExtValue();
472     } else if (Key == "Objective-C Image Info Section") {
473       SectionVal = cast<MDString>(Val)->getString();
474     } else if (Key == "Linker Options") {
475       LinkerOptions = cast<MDNode>(Val);
476     }
477   }
478 
479   // Emit the linker options if present.
480   if (LinkerOptions) {
481     for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
482       MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
483       SmallVector<std::string, 4> StrOptions;
484 
485       // Convert to strings.
486       for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
487         MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
488         StrOptions.push_back(MDOption->getString());
489       }
490 
491       Streamer.EmitLinkerOptions(StrOptions);
492     }
493   }
494 
495   // The section is mandatory. If we don't have it, then we don't have GC info.
496   if (SectionVal.empty()) return;
497 
498   StringRef Segment, Section;
499   unsigned TAA = 0, StubSize = 0;
500   bool TAAParsed;
501   std::string ErrorCode =
502     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
503                                           TAA, TAAParsed, StubSize);
504   if (!ErrorCode.empty())
505     // If invalid, report the error with report_fatal_error.
506     report_fatal_error("Invalid section specifier '" + Section + "': " +
507                        ErrorCode + ".");
508 
509   // Get the section.
510   const MCSectionMachO *S =
511     getContext().getMachOSection(Segment, Section, TAA, StubSize,
512                                  SectionKind::getDataNoRel());
513   Streamer.SwitchSection(S);
514   Streamer.EmitLabel(getContext().
515                      GetOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
516   Streamer.EmitIntValue(VersionVal, 4);
517   Streamer.EmitIntValue(ImageInfoFlags, 4);
518   Streamer.AddBlankLine();
519 }
520 
521 static void checkMachOComdat(const GlobalValue *GV) {
522   const Comdat *C = GV->getComdat();
523   if (!C)
524     return;
525 
526   report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
527                      "' cannot be lowered.");
528 }
529 
530 const MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
531     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
532     const TargetMachine &TM) const {
533   // Parse the section specifier and create it if valid.
534   StringRef Segment, Section;
535   unsigned TAA = 0, StubSize = 0;
536   bool TAAParsed;
537 
538   checkMachOComdat(GV);
539 
540   std::string ErrorCode =
541     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
542                                           TAA, TAAParsed, StubSize);
543   if (!ErrorCode.empty()) {
544     // If invalid, report the error with report_fatal_error.
545     report_fatal_error("Global variable '" + GV->getName() +
546                        "' has an invalid section specifier '" +
547                        GV->getSection() + "': " + ErrorCode + ".");
548   }
549 
550   // Get the section.
551   const MCSectionMachO *S =
552     getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
553 
554   // If TAA wasn't set by ParseSectionSpecifier() above,
555   // use the value returned by getMachOSection() as a default.
556   if (!TAAParsed)
557     TAA = S->getTypeAndAttributes();
558 
559   // Okay, now that we got the section, verify that the TAA & StubSize agree.
560   // If the user declared multiple globals with different section flags, we need
561   // to reject it here.
562   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
563     // If invalid, report the error with report_fatal_error.
564     report_fatal_error("Global variable '" + GV->getName() +
565                        "' section type or attributes does not match previous"
566                        " section specifier");
567   }
568 
569   return S;
570 }
571 
572 const MCSection *TargetLoweringObjectFileMachO::
573 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
574                        Mangler &Mang, const TargetMachine &TM) const {
575   checkMachOComdat(GV);
576 
577   // Handle thread local data.
578   if (Kind.isThreadBSS()) return TLSBSSSection;
579   if (Kind.isThreadData()) return TLSDataSection;
580 
581   if (Kind.isText())
582     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
583 
584   // If this is weak/linkonce, put this in a coalescable section, either in text
585   // or data depending on if it is writable.
586   if (GV->isWeakForLinker()) {
587     if (Kind.isReadOnly())
588       return ConstTextCoalSection;
589     return DataCoalSection;
590   }
591 
592   // FIXME: Alignment check should be handled by section classifier.
593   if (Kind.isMergeable1ByteCString() &&
594       TM.getSubtargetImpl()->getDataLayout()->getPreferredAlignment(
595           cast<GlobalVariable>(GV)) < 32)
596     return CStringSection;
597 
598   // Do not put 16-bit arrays in the UString section if they have an
599   // externally visible label, this runs into issues with certain linker
600   // versions.
601   if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
602       TM.getSubtargetImpl()->getDataLayout()->getPreferredAlignment(
603           cast<GlobalVariable>(GV)) < 32)
604     return UStringSection;
605 
606   // With MachO only variables whose corresponding symbol starts with 'l' or
607   // 'L' can be merged, so we only try merging GVs with private linkage.
608   if (GV->hasPrivateLinkage() && Kind.isMergeableConst()) {
609     if (Kind.isMergeableConst4())
610       return FourByteConstantSection;
611     if (Kind.isMergeableConst8())
612       return EightByteConstantSection;
613     if (Kind.isMergeableConst16())
614       return SixteenByteConstantSection;
615   }
616 
617   // Otherwise, if it is readonly, but not something we can specially optimize,
618   // just drop it in .const.
619   if (Kind.isReadOnly())
620     return ReadOnlySection;
621 
622   // If this is marked const, put it into a const section.  But if the dynamic
623   // linker needs to write to it, put it in the data segment.
624   if (Kind.isReadOnlyWithRel())
625     return ConstDataSection;
626 
627   // Put zero initialized globals with strong external linkage in the
628   // DATA, __common section with the .zerofill directive.
629   if (Kind.isBSSExtern())
630     return DataCommonSection;
631 
632   // Put zero initialized globals with local linkage in __DATA,__bss directive
633   // with the .zerofill directive (aka .lcomm).
634   if (Kind.isBSSLocal())
635     return DataBSSSection;
636 
637   // Otherwise, just drop the variable in the normal data section.
638   return DataSection;
639 }
640 
641 const MCSection *
642 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind,
643                                                      const Constant *C) const {
644   // If this constant requires a relocation, we have to put it in the data
645   // segment, not in the text segment.
646   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
647     return ConstDataSection;
648 
649   if (Kind.isMergeableConst4())
650     return FourByteConstantSection;
651   if (Kind.isMergeableConst8())
652     return EightByteConstantSection;
653   if (Kind.isMergeableConst16())
654     return SixteenByteConstantSection;
655   return ReadOnlySection;  // .const
656 }
657 
658 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
659     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
660     const TargetMachine &TM, MachineModuleInfo *MMI,
661     MCStreamer &Streamer) const {
662   // The mach-o version of this method defaults to returning a stub reference.
663 
664   if (Encoding & DW_EH_PE_indirect) {
665     MachineModuleInfoMachO &MachOMMI =
666       MMI->getObjFileInfo<MachineModuleInfoMachO>();
667 
668     MCSymbol *SSym =
669         getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
670 
671     // Add information about the stub reference to MachOMMI so that the stub
672     // gets emitted by the asmprinter.
673     MachineModuleInfoImpl::StubValueTy &StubSym =
674       GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
675                                   MachOMMI.getGVStubEntry(SSym);
676     if (!StubSym.getPointer()) {
677       MCSymbol *Sym = TM.getSymbol(GV, Mang);
678       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
679     }
680 
681     return TargetLoweringObjectFile::
682       getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
683                         Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
684   }
685 
686   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
687                                                            TM, MMI, Streamer);
688 }
689 
690 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
691     const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
692     MachineModuleInfo *MMI) const {
693   // The mach-o version of this method defaults to returning a stub reference.
694   MachineModuleInfoMachO &MachOMMI =
695     MMI->getObjFileInfo<MachineModuleInfoMachO>();
696 
697   MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
698 
699   // Add information about the stub reference to MachOMMI so that the stub
700   // gets emitted by the asmprinter.
701   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
702   if (!StubSym.getPointer()) {
703     MCSymbol *Sym = TM.getSymbol(GV, Mang);
704     StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
705   }
706 
707   return SSym;
708 }
709 
710 //===----------------------------------------------------------------------===//
711 //                                  COFF
712 //===----------------------------------------------------------------------===//
713 
714 static unsigned
715 getCOFFSectionFlags(SectionKind K) {
716   unsigned Flags = 0;
717 
718   if (K.isMetadata())
719     Flags |=
720       COFF::IMAGE_SCN_MEM_DISCARDABLE;
721   else if (K.isText())
722     Flags |=
723       COFF::IMAGE_SCN_MEM_EXECUTE |
724       COFF::IMAGE_SCN_MEM_READ |
725       COFF::IMAGE_SCN_CNT_CODE;
726   else if (K.isBSS())
727     Flags |=
728       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
729       COFF::IMAGE_SCN_MEM_READ |
730       COFF::IMAGE_SCN_MEM_WRITE;
731   else if (K.isThreadLocal())
732     Flags |=
733       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
734       COFF::IMAGE_SCN_MEM_READ |
735       COFF::IMAGE_SCN_MEM_WRITE;
736   else if (K.isReadOnly() || K.isReadOnlyWithRel())
737     Flags |=
738       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
739       COFF::IMAGE_SCN_MEM_READ;
740   else if (K.isWriteable())
741     Flags |=
742       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
743       COFF::IMAGE_SCN_MEM_READ |
744       COFF::IMAGE_SCN_MEM_WRITE;
745 
746   return Flags;
747 }
748 
749 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
750   const Comdat *C = GV->getComdat();
751   assert(C && "expected GV to have a Comdat!");
752 
753   StringRef ComdatGVName = C->getName();
754   const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
755   if (!ComdatGV)
756     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
757                        "' does not exist.");
758 
759   if (ComdatGV->getComdat() != C)
760     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
761                        "' is not a key for its COMDAT.");
762 
763   return ComdatGV;
764 }
765 
766 static int getSelectionForCOFF(const GlobalValue *GV) {
767   if (const Comdat *C = GV->getComdat()) {
768     const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
769     if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
770       ComdatKey = GA->getBaseObject();
771     if (ComdatKey == GV) {
772       switch (C->getSelectionKind()) {
773       case Comdat::Any:
774         return COFF::IMAGE_COMDAT_SELECT_ANY;
775       case Comdat::ExactMatch:
776         return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
777       case Comdat::Largest:
778         return COFF::IMAGE_COMDAT_SELECT_LARGEST;
779       case Comdat::NoDuplicates:
780         return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
781       case Comdat::SameSize:
782         return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
783       }
784     } else {
785       return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
786     }
787   } else if (GV->isWeakForLinker()) {
788     return COFF::IMAGE_COMDAT_SELECT_ANY;
789   }
790   return 0;
791 }
792 
793 const MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
794     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
795     const TargetMachine &TM) const {
796   int Selection = 0;
797   unsigned Characteristics = getCOFFSectionFlags(Kind);
798   StringRef Name = GV->getSection();
799   StringRef COMDATSymName = "";
800   if (GV->hasComdat()) {
801     Selection = getSelectionForCOFF(GV);
802     const GlobalValue *ComdatGV;
803     if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
804       ComdatGV = getComdatGVForCOFF(GV);
805     else
806       ComdatGV = GV;
807 
808     if (!ComdatGV->hasPrivateLinkage()) {
809       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
810       COMDATSymName = Sym->getName();
811       Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
812     } else {
813       Selection = 0;
814     }
815   }
816   return getContext().getCOFFSection(Name,
817                                      Characteristics,
818                                      Kind,
819                                      COMDATSymName,
820                                      Selection);
821 }
822 
823 static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
824   if (Kind.isText())
825     return ".text";
826   if (Kind.isBSS())
827     return ".bss";
828   if (Kind.isThreadLocal())
829     return ".tls$";
830   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
831     return ".rdata";
832   return ".data";
833 }
834 
835 
836 const MCSection *TargetLoweringObjectFileCOFF::
837 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
838                        Mangler &Mang, const TargetMachine &TM) const {
839   // If we have -ffunction-sections then we should emit the global value to a
840   // uniqued section specifically for it.
841   bool EmitUniquedSection;
842   if (Kind.isText())
843     EmitUniquedSection = TM.getFunctionSections();
844   else
845     EmitUniquedSection = TM.getDataSections();
846 
847   if ((EmitUniquedSection && !Kind.isCommon()) || GV->hasComdat()) {
848     const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
849     unsigned Characteristics = getCOFFSectionFlags(Kind);
850 
851     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
852     int Selection = getSelectionForCOFF(GV);
853     if (!Selection)
854       Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
855     const GlobalValue *ComdatGV;
856     if (GV->hasComdat())
857       ComdatGV = getComdatGVForCOFF(GV);
858     else
859       ComdatGV = GV;
860 
861     if (!ComdatGV->hasPrivateLinkage()) {
862       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
863       StringRef COMDATSymName = Sym->getName();
864       return getContext().getCOFFSection(Name, Characteristics, Kind,
865                                          COMDATSymName, Selection);
866     }
867   }
868 
869   if (Kind.isText())
870     return TextSection;
871 
872   if (Kind.isThreadLocal())
873     return TLSDataSection;
874 
875   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
876     return ReadOnlySection;
877 
878   // Note: we claim that common symbols are put in BSSSection, but they are
879   // really emitted with the magic .comm directive, which creates a symbol table
880   // entry but not a section.
881   if (Kind.isBSS() || Kind.isCommon())
882     return BSSSection;
883 
884   return DataSection;
885 }
886 
887 StringRef TargetLoweringObjectFileCOFF::
888 getDepLibFromLinkerOpt(StringRef LinkerOption) const {
889   const char *LibCmd = "/DEFAULTLIB:";
890   if (LinkerOption.startswith(LibCmd))
891     return LinkerOption.substr(strlen(LibCmd));
892   return StringRef();
893 }
894 
895 void TargetLoweringObjectFileCOFF::
896 emitModuleFlags(MCStreamer &Streamer,
897                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
898                 Mangler &Mang, const TargetMachine &TM) const {
899   MDNode *LinkerOptions = nullptr;
900 
901   // Look for the "Linker Options" flag, since it's the only one we support.
902   for (ArrayRef<Module::ModuleFlagEntry>::iterator
903        i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
904     const Module::ModuleFlagEntry &MFE = *i;
905     StringRef Key = MFE.Key->getString();
906     Metadata *Val = MFE.Val;
907     if (Key == "Linker Options") {
908       LinkerOptions = cast<MDNode>(Val);
909       break;
910     }
911   }
912   if (!LinkerOptions)
913     return;
914 
915   // Emit the linker options to the linker .drectve section.  According to the
916   // spec, this section is a space-separated string containing flags for linker.
917   const MCSection *Sec = getDrectveSection();
918   Streamer.SwitchSection(Sec);
919   for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
920     MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
921     for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
922       MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
923       StringRef Op = MDOption->getString();
924       // Lead with a space for consistency with our dllexport implementation.
925       std::string Escaped(" ");
926       if (!Op.startswith("\"") && (Op.find(" ") != StringRef::npos)) {
927         // The PE-COFF spec says args with spaces must be quoted.  It doesn't say
928         // how to escape quotes, but it probably uses this algorithm:
929         // http://msdn.microsoft.com/en-us/library/17w5ykft(v=vs.85).aspx
930         // FIXME: Reuse escaping code from Support/Windows/Program.inc
931         Escaped.push_back('\"');
932         Escaped.append(Op);
933         Escaped.push_back('\"');
934       } else {
935         Escaped.append(Op);
936       }
937       Streamer.EmitBytes(Escaped);
938     }
939   }
940 }
941 
942 const MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
943     unsigned Priority, const MCSymbol *KeySym) const {
944   return getContext().getAssociativeCOFFSection(
945       cast<MCSectionCOFF>(StaticCtorSection), KeySym);
946 }
947 
948 const MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
949     unsigned Priority, const MCSymbol *KeySym) const {
950   return getContext().getAssociativeCOFFSection(
951       cast<MCSectionCOFF>(StaticDtorSection), KeySym);
952 }
953