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/Constants.h"
17 #include "llvm/DerivedTypes.h"
18 #include "llvm/Function.h"
19 #include "llvm/GlobalVariable.h"
20 #include "llvm/Module.h"
21 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
22 #include "llvm/MC/MCContext.h"
23 #include "llvm/MC/MCExpr.h"
24 #include "llvm/MC/MCSectionMachO.h"
25 #include "llvm/MC/MCSectionELF.h"
26 #include "llvm/MC/MCSectionCOFF.h"
27 #include "llvm/MC/MCStreamer.h"
28 #include "llvm/MC/MCSymbol.h"
29 #include "llvm/Target/Mangler.h"
30 #include "llvm/Target/TargetData.h"
31 #include "llvm/Target/TargetMachine.h"
32 #include "llvm/Target/TargetOptions.h"
33 #include "llvm/Support/Dwarf.h"
34 #include "llvm/Support/ELF.h"
35 #include "llvm/Support/ErrorHandling.h"
36 #include "llvm/Support/raw_ostream.h"
37 #include "llvm/ADT/SmallString.h"
38 #include "llvm/ADT/StringExtras.h"
39 #include "llvm/ADT/Triple.h"
40 using namespace llvm;
41 using namespace dwarf;
42 
43 //===----------------------------------------------------------------------===//
44 //                                  ELF
45 //===----------------------------------------------------------------------===//
46 
47 MCSymbol *
48 TargetLoweringObjectFileELF::getCFIPersonalitySymbol(const GlobalValue *GV,
49                                                      Mangler *Mang,
50                                                 MachineModuleInfo *MMI) const {
51   unsigned Encoding = getPersonalityEncoding();
52   switch (Encoding & 0x70) {
53   default:
54     report_fatal_error("We do not support this DWARF encoding yet!");
55   case dwarf::DW_EH_PE_absptr:
56     return  Mang->getSymbol(GV);
57   case dwarf::DW_EH_PE_pcrel: {
58     return getContext().GetOrCreateSymbol(StringRef("DW.ref.") +
59                                           Mang->getSymbol(GV)->getName());
60   }
61   }
62 }
63 
64 void TargetLoweringObjectFileELF::emitPersonalityValue(MCStreamer &Streamer,
65                                                        const TargetMachine &TM,
66                                                        const MCSymbol *Sym) const {
67   SmallString<64> NameData("DW.ref.");
68   NameData += Sym->getName();
69   MCSymbol *Label = getContext().GetOrCreateSymbol(NameData);
70   Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
71   Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
72   StringRef Prefix = ".data.";
73   NameData.insert(NameData.begin(), Prefix.begin(), Prefix.end());
74   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
75   const MCSection *Sec = getContext().getELFSection(NameData,
76                                                     ELF::SHT_PROGBITS,
77                                                     Flags,
78                                                     SectionKind::getDataRel(),
79                                                     0, Label->getName());
80   Streamer.SwitchSection(Sec);
81   Streamer.EmitValueToAlignment(8);
82   Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
83   const MCExpr *E = MCConstantExpr::Create(8, getContext());
84   Streamer.EmitELFSize(Label, E);
85   Streamer.EmitLabel(Label);
86 
87   unsigned Size = TM.getTargetData()->getPointerSize();
88   Streamer.EmitSymbolValue(Sym, Size);
89 }
90 
91 static SectionKind
92 getELFKindForNamedSection(StringRef Name, SectionKind K) {
93   // N.B.: The defaults used in here are no the same ones used in MC.
94   // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
95   // both gas and MC will produce a section with no flags. Given
96   // section(".eh_frame") gcc will produce
97   // .section	.eh_frame,"a",@progbits
98   if (Name.empty() || Name[0] != '.') return K;
99 
100   // Some lame default implementation based on some magic section names.
101   if (Name == ".bss" ||
102       Name.startswith(".bss.") ||
103       Name.startswith(".gnu.linkonce.b.") ||
104       Name.startswith(".llvm.linkonce.b.") ||
105       Name == ".sbss" ||
106       Name.startswith(".sbss.") ||
107       Name.startswith(".gnu.linkonce.sb.") ||
108       Name.startswith(".llvm.linkonce.sb."))
109     return SectionKind::getBSS();
110 
111   if (Name == ".tdata" ||
112       Name.startswith(".tdata.") ||
113       Name.startswith(".gnu.linkonce.td.") ||
114       Name.startswith(".llvm.linkonce.td."))
115     return SectionKind::getThreadData();
116 
117   if (Name == ".tbss" ||
118       Name.startswith(".tbss.") ||
119       Name.startswith(".gnu.linkonce.tb.") ||
120       Name.startswith(".llvm.linkonce.tb."))
121     return SectionKind::getThreadBSS();
122 
123   return K;
124 }
125 
126 
127 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
128 
129   if (Name == ".init_array")
130     return ELF::SHT_INIT_ARRAY;
131 
132   if (Name == ".fini_array")
133     return ELF::SHT_FINI_ARRAY;
134 
135   if (Name == ".preinit_array")
136     return ELF::SHT_PREINIT_ARRAY;
137 
138   if (K.isBSS() || K.isThreadBSS())
139     return ELF::SHT_NOBITS;
140 
141   return ELF::SHT_PROGBITS;
142 }
143 
144 
145 static unsigned
146 getELFSectionFlags(SectionKind K) {
147   unsigned Flags = 0;
148 
149   if (!K.isMetadata())
150     Flags |= ELF::SHF_ALLOC;
151 
152   if (K.isText())
153     Flags |= ELF::SHF_EXECINSTR;
154 
155   if (K.isWriteable())
156     Flags |= ELF::SHF_WRITE;
157 
158   if (K.isThreadLocal())
159     Flags |= ELF::SHF_TLS;
160 
161   // K.isMergeableConst() is left out to honour PR4650
162   if (K.isMergeableCString() || K.isMergeableConst4() ||
163       K.isMergeableConst8() || K.isMergeableConst16())
164     Flags |= ELF::SHF_MERGE;
165 
166   if (K.isMergeableCString())
167     Flags |= ELF::SHF_STRINGS;
168 
169   return Flags;
170 }
171 
172 
173 const MCSection *TargetLoweringObjectFileELF::
174 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
175                          Mangler *Mang, const TargetMachine &TM) const {
176   StringRef SectionName = GV->getSection();
177 
178   // Infer section flags from the section name if we can.
179   Kind = getELFKindForNamedSection(SectionName, Kind);
180 
181   return getContext().getELFSection(SectionName,
182                                     getELFSectionType(SectionName, Kind),
183                                     getELFSectionFlags(Kind), Kind);
184 }
185 
186 /// getSectionPrefixForGlobal - Return the section prefix name used by options
187 /// FunctionsSections and DataSections.
188 static const char *getSectionPrefixForGlobal(SectionKind Kind) {
189   if (Kind.isText())                 return ".text.";
190   if (Kind.isReadOnly())             return ".rodata.";
191 
192   if (Kind.isThreadData())           return ".tdata.";
193   if (Kind.isThreadBSS())            return ".tbss.";
194 
195   if (Kind.isDataNoRel())            return ".data.";
196   if (Kind.isDataRelLocal())         return ".data.rel.local.";
197   if (Kind.isDataRel())              return ".data.rel.";
198   if (Kind.isReadOnlyWithRelLocal()) return ".data.rel.ro.local.";
199 
200   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
201   return ".data.rel.ro.";
202 }
203 
204 
205 const MCSection *TargetLoweringObjectFileELF::
206 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
207                        Mangler *Mang, const TargetMachine &TM) const {
208   // If we have -ffunction-section or -fdata-section then we should emit the
209   // global value to a uniqued section specifically for it.
210   bool EmitUniquedSection;
211   if (Kind.isText())
212     EmitUniquedSection = TM.getFunctionSections();
213   else
214     EmitUniquedSection = TM.getDataSections();
215 
216   // If this global is linkonce/weak and the target handles this by emitting it
217   // into a 'uniqued' section name, create and return the section now.
218   if ((GV->isWeakForLinker() || EmitUniquedSection) &&
219       !Kind.isCommon() && !Kind.isBSS()) {
220     const char *Prefix;
221     Prefix = getSectionPrefixForGlobal(Kind);
222 
223     SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
224     MCSymbol *Sym = Mang->getSymbol(GV);
225     Name.append(Sym->getName().begin(), Sym->getName().end());
226     StringRef Group = "";
227     unsigned Flags = getELFSectionFlags(Kind);
228     if (GV->isWeakForLinker()) {
229       Group = Sym->getName();
230       Flags |= ELF::SHF_GROUP;
231     }
232 
233     return getContext().getELFSection(Name.str(),
234                                       getELFSectionType(Name.str(), Kind),
235                                       Flags, Kind, 0, Group);
236   }
237 
238   if (Kind.isText()) return TextSection;
239 
240   if (Kind.isMergeable1ByteCString() ||
241       Kind.isMergeable2ByteCString() ||
242       Kind.isMergeable4ByteCString()) {
243 
244     // We also need alignment here.
245     // FIXME: this is getting the alignment of the character, not the
246     // alignment of the global!
247     unsigned Align =
248       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV));
249 
250     const char *SizeSpec = ".rodata.str1.";
251     if (Kind.isMergeable2ByteCString())
252       SizeSpec = ".rodata.str2.";
253     else if (Kind.isMergeable4ByteCString())
254       SizeSpec = ".rodata.str4.";
255     else
256       assert(Kind.isMergeable1ByteCString() && "unknown string width");
257 
258 
259     std::string Name = SizeSpec + utostr(Align);
260     return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
261                                       ELF::SHF_ALLOC |
262                                       ELF::SHF_MERGE |
263                                       ELF::SHF_STRINGS,
264                                       Kind);
265   }
266 
267   if (Kind.isMergeableConst()) {
268     if (Kind.isMergeableConst4() && MergeableConst4Section)
269       return MergeableConst4Section;
270     if (Kind.isMergeableConst8() && MergeableConst8Section)
271       return MergeableConst8Section;
272     if (Kind.isMergeableConst16() && MergeableConst16Section)
273       return MergeableConst16Section;
274     return ReadOnlySection;  // .const
275   }
276 
277   if (Kind.isReadOnly())             return ReadOnlySection;
278 
279   if (Kind.isThreadData())           return TLSDataSection;
280   if (Kind.isThreadBSS())            return TLSBSSSection;
281 
282   // Note: we claim that common symbols are put in BSSSection, but they are
283   // really emitted with the magic .comm directive, which creates a symbol table
284   // entry but not a section.
285   if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
286 
287   if (Kind.isDataNoRel())            return DataSection;
288   if (Kind.isDataRelLocal())         return DataRelLocalSection;
289   if (Kind.isDataRel())              return DataRelSection;
290   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
291 
292   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
293   return DataRelROSection;
294 }
295 
296 /// getSectionForConstant - Given a mergeable constant with the
297 /// specified size and relocation information, return a section that it
298 /// should be placed in.
299 const MCSection *TargetLoweringObjectFileELF::
300 getSectionForConstant(SectionKind Kind) const {
301   if (Kind.isMergeableConst4() && MergeableConst4Section)
302     return MergeableConst4Section;
303   if (Kind.isMergeableConst8() && MergeableConst8Section)
304     return MergeableConst8Section;
305   if (Kind.isMergeableConst16() && MergeableConst16Section)
306     return MergeableConst16Section;
307   if (Kind.isReadOnly())
308     return ReadOnlySection;
309 
310   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
311   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
312   return DataRelROSection;
313 }
314 
315 const MCExpr *TargetLoweringObjectFileELF::
316 getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
317                                MachineModuleInfo *MMI,
318                                unsigned Encoding, MCStreamer &Streamer) const {
319 
320   if (Encoding & dwarf::DW_EH_PE_indirect) {
321     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
322 
323     SmallString<128> Name;
324     Mang->getNameWithPrefix(Name, GV, true);
325     Name += ".DW.stub";
326 
327     // Add information about the stub reference to ELFMMI so that the stub
328     // gets emitted by the asmprinter.
329     MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
330     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
331     if (StubSym.getPointer() == 0) {
332       MCSymbol *Sym = Mang->getSymbol(GV);
333       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
334     }
335 
336     return TargetLoweringObjectFile::
337       getExprForDwarfReference(SSym, Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
338   }
339 
340   return TargetLoweringObjectFile::
341     getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, Streamer);
342 }
343 
344 const MCSection *
345 TargetLoweringObjectFileELF::getStaticCtorSection(unsigned Priority) const {
346   // The default scheme is .ctor / .dtor, so we have to invert the priority
347   // numbering.
348   if (Priority == 65535)
349     return StaticCtorSection;
350 
351   std::string Name = std::string(".ctors.") + utostr(65535 - Priority);
352   return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
353                                     ELF::SHF_ALLOC |ELF::SHF_WRITE,
354                                     SectionKind::getDataRel());
355 }
356 
357 const MCSection *
358 TargetLoweringObjectFileELF::getStaticDtorSection(unsigned Priority) const {
359   // The default scheme is .ctor / .dtor, so we have to invert the priority
360   // numbering.
361   if (Priority == 65535)
362     return StaticDtorSection;
363 
364   std::string Name = std::string(".dtors.") + utostr(65535 - Priority);
365   return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
366                                     ELF::SHF_ALLOC |ELF::SHF_WRITE,
367                                     SectionKind::getDataRel());
368 }
369 
370 //===----------------------------------------------------------------------===//
371 //                                 MachO
372 //===----------------------------------------------------------------------===//
373 
374 /// emitModuleFlags - Emit the module flags that specify the garbage collection
375 /// information.
376 void TargetLoweringObjectFileMachO::
377 emitModuleFlags(MCStreamer &Streamer,
378                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
379                 Mangler *Mang, const TargetMachine &TM) const {
380   unsigned VersionVal = 0;
381   unsigned GCFlags = 0;
382   StringRef SectionVal;
383 
384   for (ArrayRef<Module::ModuleFlagEntry>::iterator
385          i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
386     const Module::ModuleFlagEntry &MFE = *i;
387 
388     // Ignore flags with 'Require' behavior.
389     if (MFE.Behavior == Module::Require)
390       continue;
391 
392     StringRef Key = MFE.Key->getString();
393     Value *Val = MFE.Val;
394 
395     if (Key == "Objective-C Image Info Version")
396       VersionVal = cast<ConstantInt>(Val)->getZExtValue();
397     else if (Key == "Objective-C Garbage Collection" ||
398              Key == "Objective-C GC Only")
399       GCFlags |= cast<ConstantInt>(Val)->getZExtValue();
400     else if (Key == "Objective-C Image Info Section")
401       SectionVal = cast<MDString>(Val)->getString();
402   }
403 
404   // The section is mandatory. If we don't have it, then we don't have GC info.
405   if (SectionVal.empty()) return;
406 
407   StringRef Segment, Section;
408   unsigned TAA = 0, StubSize = 0;
409   bool TAAParsed;
410   std::string ErrorCode =
411     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
412                                           TAA, TAAParsed, StubSize);
413   if (!ErrorCode.empty()) {
414     // If invalid, report the error with report_fatal_error.
415     report_fatal_error("Invalid section specifier '" +
416                        Section + "': " + ErrorCode + ".");
417   }
418 
419   // Get the section.
420   const MCSectionMachO *S =
421     getContext().getMachOSection(Segment, Section, TAA, StubSize,
422                                  SectionKind::getDataRel());
423   Streamer.SwitchSection(S);
424   Streamer.EmitLabel(getContext().
425                      GetOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
426   Streamer.EmitIntValue(VersionVal, 4);
427   Streamer.EmitIntValue(GCFlags, 4);
428   Streamer.AddBlankLine();
429 }
430 
431 const MCSection *TargetLoweringObjectFileMachO::
432 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
433                          Mangler *Mang, const TargetMachine &TM) const {
434   // Parse the section specifier and create it if valid.
435   StringRef Segment, Section;
436   unsigned TAA = 0, StubSize = 0;
437   bool TAAParsed;
438   std::string ErrorCode =
439     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
440                                           TAA, TAAParsed, StubSize);
441   if (!ErrorCode.empty()) {
442     // If invalid, report the error with report_fatal_error.
443     report_fatal_error("Global variable '" + GV->getName() +
444                        "' has an invalid section specifier '" +
445                        GV->getSection() + "': " + ErrorCode + ".");
446   }
447 
448   // Get the section.
449   const MCSectionMachO *S =
450     getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
451 
452   // If TAA wasn't set by ParseSectionSpecifier() above,
453   // use the value returned by getMachOSection() as a default.
454   if (!TAAParsed)
455     TAA = S->getTypeAndAttributes();
456 
457   // Okay, now that we got the section, verify that the TAA & StubSize agree.
458   // If the user declared multiple globals with different section flags, we need
459   // to reject it here.
460   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
461     // If invalid, report the error with report_fatal_error.
462     report_fatal_error("Global variable '" + GV->getName() +
463                        "' section type or attributes does not match previous"
464                        " section specifier");
465   }
466 
467   return S;
468 }
469 
470 const MCSection *TargetLoweringObjectFileMachO::
471 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
472                        Mangler *Mang, const TargetMachine &TM) const {
473 
474   // Handle thread local data.
475   if (Kind.isThreadBSS()) return TLSBSSSection;
476   if (Kind.isThreadData()) return TLSDataSection;
477 
478   if (Kind.isText())
479     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
480 
481   // If this is weak/linkonce, put this in a coalescable section, either in text
482   // or data depending on if it is writable.
483   if (GV->isWeakForLinker()) {
484     if (Kind.isReadOnly())
485       return ConstTextCoalSection;
486     return DataCoalSection;
487   }
488 
489   // FIXME: Alignment check should be handled by section classifier.
490   if (Kind.isMergeable1ByteCString() &&
491       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
492     return CStringSection;
493 
494   // Do not put 16-bit arrays in the UString section if they have an
495   // externally visible label, this runs into issues with certain linker
496   // versions.
497   if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
498       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
499     return UStringSection;
500 
501   if (Kind.isMergeableConst()) {
502     if (Kind.isMergeableConst4())
503       return FourByteConstantSection;
504     if (Kind.isMergeableConst8())
505       return EightByteConstantSection;
506     if (Kind.isMergeableConst16() && SixteenByteConstantSection)
507       return SixteenByteConstantSection;
508   }
509 
510   // Otherwise, if it is readonly, but not something we can specially optimize,
511   // just drop it in .const.
512   if (Kind.isReadOnly())
513     return ReadOnlySection;
514 
515   // If this is marked const, put it into a const section.  But if the dynamic
516   // linker needs to write to it, put it in the data segment.
517   if (Kind.isReadOnlyWithRel())
518     return ConstDataSection;
519 
520   // Put zero initialized globals with strong external linkage in the
521   // DATA, __common section with the .zerofill directive.
522   if (Kind.isBSSExtern())
523     return DataCommonSection;
524 
525   // Put zero initialized globals with local linkage in __DATA,__bss directive
526   // with the .zerofill directive (aka .lcomm).
527   if (Kind.isBSSLocal())
528     return DataBSSSection;
529 
530   // Otherwise, just drop the variable in the normal data section.
531   return DataSection;
532 }
533 
534 const MCSection *
535 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
536   // If this constant requires a relocation, we have to put it in the data
537   // segment, not in the text segment.
538   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
539     return ConstDataSection;
540 
541   if (Kind.isMergeableConst4())
542     return FourByteConstantSection;
543   if (Kind.isMergeableConst8())
544     return EightByteConstantSection;
545   if (Kind.isMergeableConst16() && SixteenByteConstantSection)
546     return SixteenByteConstantSection;
547   return ReadOnlySection;  // .const
548 }
549 
550 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
551 /// not to emit the UsedDirective for some symbols in llvm.used.
552 // FIXME: REMOVE this (rdar://7071300)
553 bool TargetLoweringObjectFileMachO::
554 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
555   /// On Darwin, internally linked data beginning with "L" or "l" does not have
556   /// the directive emitted (this occurs in ObjC metadata).
557   if (!GV) return false;
558 
559   // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
560   if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
561     // FIXME: ObjC metadata is currently emitted as internal symbols that have
562     // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
563     // this horrible hack can go away.
564     MCSymbol *Sym = Mang->getSymbol(GV);
565     if (Sym->getName()[0] == 'L' || Sym->getName()[0] == 'l')
566       return false;
567   }
568 
569   return true;
570 }
571 
572 const MCExpr *TargetLoweringObjectFileMachO::
573 getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
574                                MachineModuleInfo *MMI, unsigned Encoding,
575                                MCStreamer &Streamer) const {
576   // The mach-o version of this method defaults to returning a stub reference.
577 
578   if (Encoding & DW_EH_PE_indirect) {
579     MachineModuleInfoMachO &MachOMMI =
580       MMI->getObjFileInfo<MachineModuleInfoMachO>();
581 
582     SmallString<128> Name;
583     Mang->getNameWithPrefix(Name, GV, true);
584     Name += "$non_lazy_ptr";
585 
586     // Add information about the stub reference to MachOMMI so that the stub
587     // gets emitted by the asmprinter.
588     MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
589     MachineModuleInfoImpl::StubValueTy &StubSym =
590       GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
591                                   MachOMMI.getGVStubEntry(SSym);
592     if (StubSym.getPointer() == 0) {
593       MCSymbol *Sym = Mang->getSymbol(GV);
594       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
595     }
596 
597     return TargetLoweringObjectFile::
598       getExprForDwarfReference(SSym, Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
599   }
600 
601   return TargetLoweringObjectFile::
602     getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, Streamer);
603 }
604 
605 MCSymbol *TargetLoweringObjectFileMachO::
606 getCFIPersonalitySymbol(const GlobalValue *GV, Mangler *Mang,
607                         MachineModuleInfo *MMI) const {
608   // The mach-o version of this method defaults to returning a stub reference.
609   MachineModuleInfoMachO &MachOMMI =
610     MMI->getObjFileInfo<MachineModuleInfoMachO>();
611 
612   SmallString<128> Name;
613   Mang->getNameWithPrefix(Name, GV, true);
614   Name += "$non_lazy_ptr";
615 
616   // Add information about the stub reference to MachOMMI so that the stub
617   // gets emitted by the asmprinter.
618   MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
619   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
620   if (StubSym.getPointer() == 0) {
621     MCSymbol *Sym = Mang->getSymbol(GV);
622     StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
623   }
624 
625   return SSym;
626 }
627 
628 //===----------------------------------------------------------------------===//
629 //                                  COFF
630 //===----------------------------------------------------------------------===//
631 
632 static unsigned
633 getCOFFSectionFlags(SectionKind K) {
634   unsigned Flags = 0;
635 
636   if (K.isMetadata())
637     Flags |=
638       COFF::IMAGE_SCN_MEM_DISCARDABLE;
639   else if (K.isText())
640     Flags |=
641       COFF::IMAGE_SCN_MEM_EXECUTE |
642       COFF::IMAGE_SCN_MEM_READ |
643       COFF::IMAGE_SCN_CNT_CODE;
644   else if (K.isBSS ())
645     Flags |=
646       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
647       COFF::IMAGE_SCN_MEM_READ |
648       COFF::IMAGE_SCN_MEM_WRITE;
649   else if (K.isThreadLocal())
650     Flags |=
651       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
652       COFF::IMAGE_SCN_MEM_READ |
653       COFF::IMAGE_SCN_MEM_WRITE;
654   else if (K.isReadOnly())
655     Flags |=
656       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
657       COFF::IMAGE_SCN_MEM_READ;
658   else if (K.isWriteable())
659     Flags |=
660       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
661       COFF::IMAGE_SCN_MEM_READ |
662       COFF::IMAGE_SCN_MEM_WRITE;
663 
664   return Flags;
665 }
666 
667 const MCSection *TargetLoweringObjectFileCOFF::
668 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
669                          Mangler *Mang, const TargetMachine &TM) const {
670   return getContext().getCOFFSection(GV->getSection(),
671                                      getCOFFSectionFlags(Kind),
672                                      Kind);
673 }
674 
675 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
676   if (Kind.isText())
677     return ".text$";
678   if (Kind.isBSS ())
679     return ".bss$";
680   if (Kind.isThreadLocal())
681     return ".tls$";
682   if (Kind.isWriteable())
683     return ".data$";
684   return ".rdata$";
685 }
686 
687 
688 const MCSection *TargetLoweringObjectFileCOFF::
689 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
690                        Mangler *Mang, const TargetMachine &TM) const {
691 
692   // If this global is linkonce/weak and the target handles this by emitting it
693   // into a 'uniqued' section name, create and return the section now.
694   if (GV->isWeakForLinker()) {
695     const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
696     SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
697     MCSymbol *Sym = Mang->getSymbol(GV);
698     Name.append(Sym->getName().begin() + 1, Sym->getName().end());
699 
700     unsigned Characteristics = getCOFFSectionFlags(Kind);
701 
702     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
703 
704     return getContext().getCOFFSection(Name.str(), Characteristics,
705                           COFF::IMAGE_COMDAT_SELECT_ANY, Kind);
706   }
707 
708   if (Kind.isText())
709     return getTextSection();
710 
711   if (Kind.isThreadLocal())
712     return getTLSDataSection();
713 
714   return getDataSection();
715 }
716 
717