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/CodeGen/MachineModuleInfoImpls.h"
21 #include "llvm/MC/MCContext.h"
22 #include "llvm/MC/MCExpr.h"
23 #include "llvm/MC/MCSectionMachO.h"
24 #include "llvm/MC/MCSectionELF.h"
25 #include "llvm/MC/MCSymbol.h"
26 #include "llvm/Target/Mangler.h"
27 #include "llvm/Target/TargetData.h"
28 #include "llvm/Target/TargetMachine.h"
29 #include "llvm/Target/TargetOptions.h"
30 #include "llvm/Support/Dwarf.h"
31 #include "llvm/Support/ErrorHandling.h"
32 #include "llvm/Support/raw_ostream.h"
33 #include "llvm/ADT/SmallString.h"
34 #include "llvm/ADT/StringExtras.h"
35 using namespace llvm;
36 using namespace dwarf;
37 
38 //===----------------------------------------------------------------------===//
39 //                                  ELF
40 //===----------------------------------------------------------------------===//
41 typedef StringMap<const MCSectionELF*> ELFUniqueMapTy;
42 
43 TargetLoweringObjectFileELF::~TargetLoweringObjectFileELF() {
44   // If we have the section uniquing map, free it.
45   delete (ELFUniqueMapTy*)UniquingMap;
46 }
47 
48 const MCSection *TargetLoweringObjectFileELF::
49 getELFSection(StringRef Section, unsigned Type, unsigned Flags,
50               SectionKind Kind, bool IsExplicit) const {
51   if (UniquingMap == 0)
52     UniquingMap = new ELFUniqueMapTy();
53   ELFUniqueMapTy &Map = *(ELFUniqueMapTy*)UniquingMap;
54 
55   // Do the lookup, if we have a hit, return it.
56   const MCSectionELF *&Entry = Map[Section];
57   if (Entry) return Entry;
58 
59   return Entry = MCSectionELF::Create(Section, Type, Flags, Kind, IsExplicit,
60                                       getContext());
61 }
62 
63 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
64                                              const TargetMachine &TM) {
65   if (UniquingMap != 0)
66     ((ELFUniqueMapTy*)UniquingMap)->clear();
67   TargetLoweringObjectFile::Initialize(Ctx, TM);
68 
69   BSSSection =
70     getELFSection(".bss", MCSectionELF::SHT_NOBITS,
71                   MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
72                   SectionKind::getBSS());
73 
74   TextSection =
75     getELFSection(".text", MCSectionELF::SHT_PROGBITS,
76                   MCSectionELF::SHF_EXECINSTR | MCSectionELF::SHF_ALLOC,
77                   SectionKind::getText());
78 
79   DataSection =
80     getELFSection(".data", MCSectionELF::SHT_PROGBITS,
81                   MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
82                   SectionKind::getDataRel());
83 
84   ReadOnlySection =
85     getELFSection(".rodata", MCSectionELF::SHT_PROGBITS,
86                   MCSectionELF::SHF_ALLOC,
87                   SectionKind::getReadOnly());
88 
89   TLSDataSection =
90     getELFSection(".tdata", MCSectionELF::SHT_PROGBITS,
91                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
92                   MCSectionELF::SHF_WRITE, SectionKind::getThreadData());
93 
94   TLSBSSSection =
95     getELFSection(".tbss", MCSectionELF::SHT_NOBITS,
96                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
97                   MCSectionELF::SHF_WRITE, SectionKind::getThreadBSS());
98 
99   DataRelSection =
100     getELFSection(".data.rel", MCSectionELF::SHT_PROGBITS,
101                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
102                   SectionKind::getDataRel());
103 
104   DataRelLocalSection =
105     getELFSection(".data.rel.local", MCSectionELF::SHT_PROGBITS,
106                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
107                   SectionKind::getDataRelLocal());
108 
109   DataRelROSection =
110     getELFSection(".data.rel.ro", MCSectionELF::SHT_PROGBITS,
111                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
112                   SectionKind::getReadOnlyWithRel());
113 
114   DataRelROLocalSection =
115     getELFSection(".data.rel.ro.local", MCSectionELF::SHT_PROGBITS,
116                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
117                   SectionKind::getReadOnlyWithRelLocal());
118 
119   MergeableConst4Section =
120     getELFSection(".rodata.cst4", MCSectionELF::SHT_PROGBITS,
121                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
122                   SectionKind::getMergeableConst4());
123 
124   MergeableConst8Section =
125     getELFSection(".rodata.cst8", MCSectionELF::SHT_PROGBITS,
126                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
127                   SectionKind::getMergeableConst8());
128 
129   MergeableConst16Section =
130     getELFSection(".rodata.cst16", MCSectionELF::SHT_PROGBITS,
131                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
132                   SectionKind::getMergeableConst16());
133 
134   StaticCtorSection =
135     getELFSection(".ctors", MCSectionELF::SHT_PROGBITS,
136                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
137                   SectionKind::getDataRel());
138 
139   StaticDtorSection =
140     getELFSection(".dtors", MCSectionELF::SHT_PROGBITS,
141                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
142                   SectionKind::getDataRel());
143 
144   // Exception Handling Sections.
145 
146   // FIXME: We're emitting LSDA info into a readonly section on ELF, even though
147   // it contains relocatable pointers.  In PIC mode, this is probably a big
148   // runtime hit for C++ apps.  Either the contents of the LSDA need to be
149   // adjusted or this should be a data section.
150   LSDASection =
151     getELFSection(".gcc_except_table", MCSectionELF::SHT_PROGBITS,
152                   MCSectionELF::SHF_ALLOC, SectionKind::getReadOnly());
153   EHFrameSection =
154     getELFSection(".eh_frame", MCSectionELF::SHT_PROGBITS,
155                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
156                   SectionKind::getDataRel());
157 
158   // Debug Info Sections.
159   DwarfAbbrevSection =
160     getELFSection(".debug_abbrev", MCSectionELF::SHT_PROGBITS, 0,
161                   SectionKind::getMetadata());
162   DwarfInfoSection =
163     getELFSection(".debug_info", MCSectionELF::SHT_PROGBITS, 0,
164                   SectionKind::getMetadata());
165   DwarfLineSection =
166     getELFSection(".debug_line", MCSectionELF::SHT_PROGBITS, 0,
167                   SectionKind::getMetadata());
168   DwarfFrameSection =
169     getELFSection(".debug_frame", MCSectionELF::SHT_PROGBITS, 0,
170                   SectionKind::getMetadata());
171   DwarfPubNamesSection =
172     getELFSection(".debug_pubnames", MCSectionELF::SHT_PROGBITS, 0,
173                   SectionKind::getMetadata());
174   DwarfPubTypesSection =
175     getELFSection(".debug_pubtypes", MCSectionELF::SHT_PROGBITS, 0,
176                   SectionKind::getMetadata());
177   DwarfStrSection =
178     getELFSection(".debug_str", MCSectionELF::SHT_PROGBITS, 0,
179                   SectionKind::getMetadata());
180   DwarfLocSection =
181     getELFSection(".debug_loc", MCSectionELF::SHT_PROGBITS, 0,
182                   SectionKind::getMetadata());
183   DwarfARangesSection =
184     getELFSection(".debug_aranges", MCSectionELF::SHT_PROGBITS, 0,
185                   SectionKind::getMetadata());
186   DwarfRangesSection =
187     getELFSection(".debug_ranges", MCSectionELF::SHT_PROGBITS, 0,
188                   SectionKind::getMetadata());
189   DwarfMacroInfoSection =
190     getELFSection(".debug_macinfo", MCSectionELF::SHT_PROGBITS, 0,
191                   SectionKind::getMetadata());
192 }
193 
194 
195 static SectionKind
196 getELFKindForNamedSection(StringRef Name, SectionKind K) {
197   if (Name.empty() || Name[0] != '.') return K;
198 
199   // Some lame default implementation based on some magic section names.
200   if (Name == ".bss" ||
201       Name.startswith(".bss.") ||
202       Name.startswith(".gnu.linkonce.b.") ||
203       Name.startswith(".llvm.linkonce.b.") ||
204       Name == ".sbss" ||
205       Name.startswith(".sbss.") ||
206       Name.startswith(".gnu.linkonce.sb.") ||
207       Name.startswith(".llvm.linkonce.sb."))
208     return SectionKind::getBSS();
209 
210   if (Name == ".tdata" ||
211       Name.startswith(".tdata.") ||
212       Name.startswith(".gnu.linkonce.td.") ||
213       Name.startswith(".llvm.linkonce.td."))
214     return SectionKind::getThreadData();
215 
216   if (Name == ".tbss" ||
217       Name.startswith(".tbss.") ||
218       Name.startswith(".gnu.linkonce.tb.") ||
219       Name.startswith(".llvm.linkonce.tb."))
220     return SectionKind::getThreadBSS();
221 
222   return K;
223 }
224 
225 
226 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
227 
228   if (Name == ".init_array")
229     return MCSectionELF::SHT_INIT_ARRAY;
230 
231   if (Name == ".fini_array")
232     return MCSectionELF::SHT_FINI_ARRAY;
233 
234   if (Name == ".preinit_array")
235     return MCSectionELF::SHT_PREINIT_ARRAY;
236 
237   if (K.isBSS() || K.isThreadBSS())
238     return MCSectionELF::SHT_NOBITS;
239 
240   return MCSectionELF::SHT_PROGBITS;
241 }
242 
243 
244 static unsigned
245 getELFSectionFlags(SectionKind K) {
246   unsigned Flags = 0;
247 
248   if (!K.isMetadata())
249     Flags |= MCSectionELF::SHF_ALLOC;
250 
251   if (K.isText())
252     Flags |= MCSectionELF::SHF_EXECINSTR;
253 
254   if (K.isWriteable())
255     Flags |= MCSectionELF::SHF_WRITE;
256 
257   if (K.isThreadLocal())
258     Flags |= MCSectionELF::SHF_TLS;
259 
260   // K.isMergeableConst() is left out to honour PR4650
261   if (K.isMergeableCString() || K.isMergeableConst4() ||
262       K.isMergeableConst8() || K.isMergeableConst16())
263     Flags |= MCSectionELF::SHF_MERGE;
264 
265   if (K.isMergeableCString())
266     Flags |= MCSectionELF::SHF_STRINGS;
267 
268   return Flags;
269 }
270 
271 
272 const MCSection *TargetLoweringObjectFileELF::
273 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
274                          Mangler *Mang, const TargetMachine &TM) const {
275   StringRef SectionName = GV->getSection();
276 
277   // Infer section flags from the section name if we can.
278   Kind = getELFKindForNamedSection(SectionName, Kind);
279 
280   return getELFSection(SectionName,
281                        getELFSectionType(SectionName, Kind),
282                        getELFSectionFlags(Kind), Kind, true);
283 }
284 
285 static const char *getSectionPrefixForUniqueGlobal(SectionKind Kind) {
286   if (Kind.isText())                 return ".gnu.linkonce.t.";
287   if (Kind.isReadOnly())             return ".gnu.linkonce.r.";
288 
289   if (Kind.isThreadData())           return ".gnu.linkonce.td.";
290   if (Kind.isThreadBSS())            return ".gnu.linkonce.tb.";
291 
292   if (Kind.isDataNoRel())            return ".gnu.linkonce.d.";
293   if (Kind.isDataRelLocal())         return ".gnu.linkonce.d.rel.local.";
294   if (Kind.isDataRel())              return ".gnu.linkonce.d.rel.";
295   if (Kind.isReadOnlyWithRelLocal()) return ".gnu.linkonce.d.rel.ro.local.";
296 
297   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
298   return ".gnu.linkonce.d.rel.ro.";
299 }
300 
301 const MCSection *TargetLoweringObjectFileELF::
302 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
303                        Mangler *Mang, const TargetMachine &TM) const {
304 
305   // If this global is linkonce/weak and the target handles this by emitting it
306   // into a 'uniqued' section name, create and return the section now.
307   if (GV->isWeakForLinker() && !Kind.isCommon() && !Kind.isBSS()) {
308     const char *Prefix = getSectionPrefixForUniqueGlobal(Kind);
309     SmallString<128> Name;
310     Name.append(Prefix, Prefix+strlen(Prefix));
311     Mang->getNameWithPrefix(Name, GV, false);
312     return getELFSection(Name.str(), getELFSectionType(Name.str(), Kind),
313                          getELFSectionFlags(Kind), Kind);
314   }
315 
316   if (Kind.isText()) return TextSection;
317 
318   if (Kind.isMergeable1ByteCString() ||
319       Kind.isMergeable2ByteCString() ||
320       Kind.isMergeable4ByteCString()) {
321 
322     // We also need alignment here.
323     // FIXME: this is getting the alignment of the character, not the
324     // alignment of the global!
325     unsigned Align =
326       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV));
327 
328     const char *SizeSpec = ".rodata.str1.";
329     if (Kind.isMergeable2ByteCString())
330       SizeSpec = ".rodata.str2.";
331     else if (Kind.isMergeable4ByteCString())
332       SizeSpec = ".rodata.str4.";
333     else
334       assert(Kind.isMergeable1ByteCString() && "unknown string width");
335 
336 
337     std::string Name = SizeSpec + utostr(Align);
338     return getELFSection(Name, MCSectionELF::SHT_PROGBITS,
339                          MCSectionELF::SHF_ALLOC |
340                          MCSectionELF::SHF_MERGE |
341                          MCSectionELF::SHF_STRINGS,
342                          Kind);
343   }
344 
345   if (Kind.isMergeableConst()) {
346     if (Kind.isMergeableConst4() && MergeableConst4Section)
347       return MergeableConst4Section;
348     if (Kind.isMergeableConst8() && MergeableConst8Section)
349       return MergeableConst8Section;
350     if (Kind.isMergeableConst16() && MergeableConst16Section)
351       return MergeableConst16Section;
352     return ReadOnlySection;  // .const
353   }
354 
355   if (Kind.isReadOnly())             return ReadOnlySection;
356 
357   if (Kind.isThreadData())           return TLSDataSection;
358   if (Kind.isThreadBSS())            return TLSBSSSection;
359 
360   // Note: we claim that common symbols are put in BSSSection, but they are
361   // really emitted with the magic .comm directive, which creates a symbol table
362   // entry but not a section.
363   if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
364 
365   if (Kind.isDataNoRel())            return DataSection;
366   if (Kind.isDataRelLocal())         return DataRelLocalSection;
367   if (Kind.isDataRel())              return DataRelSection;
368   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
369 
370   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
371   return DataRelROSection;
372 }
373 
374 /// getSectionForConstant - Given a mergeable constant with the
375 /// specified size and relocation information, return a section that it
376 /// should be placed in.
377 const MCSection *TargetLoweringObjectFileELF::
378 getSectionForConstant(SectionKind Kind) const {
379   if (Kind.isMergeableConst4() && MergeableConst4Section)
380     return MergeableConst4Section;
381   if (Kind.isMergeableConst8() && MergeableConst8Section)
382     return MergeableConst8Section;
383   if (Kind.isMergeableConst16() && MergeableConst16Section)
384     return MergeableConst16Section;
385   if (Kind.isReadOnly())
386     return ReadOnlySection;
387 
388   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
389   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
390   return DataRelROSection;
391 }
392 
393 const MCExpr *TargetLoweringObjectFileELF::
394 getSymbolForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
395                              MachineModuleInfo *MMI, unsigned Encoding) const {
396 
397   if (Encoding & dwarf::DW_EH_PE_indirect) {
398     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
399 
400     SmallString<128> Name;
401     Mang->getNameWithPrefix(Name, GV, true);
402     Name += ".DW.stub";
403 
404     // Add information about the stub reference to ELFMMI so that the stub
405     // gets emitted by the asmprinter.
406     MCSymbol *Sym = getContext().GetOrCreateTemporarySymbol(Name.str());
407     MCSymbol *&StubSym = ELFMMI.getGVStubEntry(Sym);
408     if (StubSym == 0) {
409       Name.clear();
410       Mang->getNameWithPrefix(Name, GV, false);
411       if (GV->hasPrivateLinkage())
412         StubSym = getContext().GetOrCreateTemporarySymbol(Name.str());
413       else
414         StubSym = getContext().GetOrCreateSymbol(Name.str());
415     }
416 
417     return TargetLoweringObjectFile::
418       getSymbolForDwarfReference(Sym, MMI,
419                                  Encoding & ~dwarf::DW_EH_PE_indirect);
420   }
421 
422   return TargetLoweringObjectFile::
423     getSymbolForDwarfGlobalReference(GV, Mang, MMI, Encoding);
424 }
425 
426 //===----------------------------------------------------------------------===//
427 //                                 MachO
428 //===----------------------------------------------------------------------===//
429 
430 typedef StringMap<const MCSectionMachO*> MachOUniqueMapTy;
431 
432 TargetLoweringObjectFileMachO::~TargetLoweringObjectFileMachO() {
433   // If we have the MachO uniquing map, free it.
434   delete (MachOUniqueMapTy*)UniquingMap;
435 }
436 
437 
438 const MCSectionMachO *TargetLoweringObjectFileMachO::
439 getMachOSection(StringRef Segment, StringRef Section,
440                 unsigned TypeAndAttributes,
441                 unsigned Reserved2, SectionKind Kind) const {
442   // We unique sections by their segment/section pair.  The returned section
443   // may not have the same flags as the requested section, if so this should be
444   // diagnosed by the client as an error.
445 
446   // Create the map if it doesn't already exist.
447   if (UniquingMap == 0)
448     UniquingMap = new MachOUniqueMapTy();
449   MachOUniqueMapTy &Map = *(MachOUniqueMapTy*)UniquingMap;
450 
451   // Form the name to look up.
452   SmallString<64> Name;
453   Name += Segment;
454   Name.push_back(',');
455   Name += Section;
456 
457   // Do the lookup, if we have a hit, return it.
458   const MCSectionMachO *&Entry = Map[Name.str()];
459   if (Entry) return Entry;
460 
461   // Otherwise, return a new section.
462   return Entry = MCSectionMachO::Create(Segment, Section, TypeAndAttributes,
463                                         Reserved2, Kind, getContext());
464 }
465 
466 
467 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
468                                                const TargetMachine &TM) {
469   // _foo.eh symbols are currently always exported so that the linker knows
470   // about them.  This is not necessary on 10.6 and later, but it
471   // doesn't hurt anything.
472   // FIXME: I need to get this from Triple.
473   IsFunctionEHSymbolGlobal = true;
474   IsFunctionEHFrameSymbolPrivate = false;
475   SupportsWeakOmittedEHFrame = false;
476 
477   if (UniquingMap != 0)
478     ((MachOUniqueMapTy*)UniquingMap)->clear();
479   TargetLoweringObjectFile::Initialize(Ctx, TM);
480 
481   TextSection // .text
482     = getMachOSection("__TEXT", "__text",
483                       MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
484                       SectionKind::getText());
485   DataSection // .data
486     = getMachOSection("__DATA", "__data", 0, SectionKind::getDataRel());
487 
488   CStringSection // .cstring
489     = getMachOSection("__TEXT", "__cstring", MCSectionMachO::S_CSTRING_LITERALS,
490                       SectionKind::getMergeable1ByteCString());
491   UStringSection
492     = getMachOSection("__TEXT","__ustring", 0,
493                       SectionKind::getMergeable2ByteCString());
494   FourByteConstantSection // .literal4
495     = getMachOSection("__TEXT", "__literal4", MCSectionMachO::S_4BYTE_LITERALS,
496                       SectionKind::getMergeableConst4());
497   EightByteConstantSection // .literal8
498     = getMachOSection("__TEXT", "__literal8", MCSectionMachO::S_8BYTE_LITERALS,
499                       SectionKind::getMergeableConst8());
500 
501   // ld_classic doesn't support .literal16 in 32-bit mode, and ld64 falls back
502   // to using it in -static mode.
503   SixteenByteConstantSection = 0;
504   if (TM.getRelocationModel() != Reloc::Static &&
505       TM.getTargetData()->getPointerSize() == 32)
506     SixteenByteConstantSection =   // .literal16
507       getMachOSection("__TEXT", "__literal16",MCSectionMachO::S_16BYTE_LITERALS,
508                       SectionKind::getMergeableConst16());
509 
510   ReadOnlySection  // .const
511     = getMachOSection("__TEXT", "__const", 0, SectionKind::getReadOnly());
512 
513   TextCoalSection
514     = getMachOSection("__TEXT", "__textcoal_nt",
515                       MCSectionMachO::S_COALESCED |
516                       MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
517                       SectionKind::getText());
518   ConstTextCoalSection
519     = getMachOSection("__TEXT", "__const_coal", MCSectionMachO::S_COALESCED,
520                       SectionKind::getText());
521   ConstDataCoalSection
522     = getMachOSection("__DATA","__const_coal", MCSectionMachO::S_COALESCED,
523                       SectionKind::getText());
524   ConstDataSection  // .const_data
525     = getMachOSection("__DATA", "__const", 0,
526                       SectionKind::getReadOnlyWithRel());
527   DataCoalSection
528     = getMachOSection("__DATA","__datacoal_nt", MCSectionMachO::S_COALESCED,
529                       SectionKind::getDataRel());
530   DataCommonSection
531     = getMachOSection("__DATA","__common", MCSectionMachO::S_ZEROFILL,
532                       SectionKind::getBSS());
533   DataBSSSection
534     = getMachOSection("__DATA","__bss", MCSectionMachO::S_ZEROFILL,
535                     SectionKind::getBSS());
536 
537 
538   LazySymbolPointerSection
539     = getMachOSection("__DATA", "__la_symbol_ptr",
540                       MCSectionMachO::S_LAZY_SYMBOL_POINTERS,
541                       SectionKind::getMetadata());
542   NonLazySymbolPointerSection
543     = getMachOSection("__DATA", "__nl_symbol_ptr",
544                       MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS,
545                       SectionKind::getMetadata());
546 
547   if (TM.getRelocationModel() == Reloc::Static) {
548     StaticCtorSection
549       = getMachOSection("__TEXT", "__constructor", 0,SectionKind::getDataRel());
550     StaticDtorSection
551       = getMachOSection("__TEXT", "__destructor", 0, SectionKind::getDataRel());
552   } else {
553     StaticCtorSection
554       = getMachOSection("__DATA", "__mod_init_func",
555                         MCSectionMachO::S_MOD_INIT_FUNC_POINTERS,
556                         SectionKind::getDataRel());
557     StaticDtorSection
558       = getMachOSection("__DATA", "__mod_term_func",
559                         MCSectionMachO::S_MOD_TERM_FUNC_POINTERS,
560                         SectionKind::getDataRel());
561   }
562 
563   // Exception Handling.
564   LSDASection = getMachOSection("__DATA", "__gcc_except_tab", 0,
565                                 SectionKind::getDataRel());
566   EHFrameSection =
567     getMachOSection("__TEXT", "__eh_frame",
568                     MCSectionMachO::S_COALESCED |
569                     MCSectionMachO::S_ATTR_NO_TOC |
570                     MCSectionMachO::S_ATTR_STRIP_STATIC_SYMS |
571                     MCSectionMachO::S_ATTR_LIVE_SUPPORT,
572                     SectionKind::getReadOnly());
573 
574   // Debug Information.
575   DwarfAbbrevSection =
576     getMachOSection("__DWARF", "__debug_abbrev", MCSectionMachO::S_ATTR_DEBUG,
577                     SectionKind::getMetadata());
578   DwarfInfoSection =
579     getMachOSection("__DWARF", "__debug_info", MCSectionMachO::S_ATTR_DEBUG,
580                     SectionKind::getMetadata());
581   DwarfLineSection =
582     getMachOSection("__DWARF", "__debug_line", MCSectionMachO::S_ATTR_DEBUG,
583                     SectionKind::getMetadata());
584   DwarfFrameSection =
585     getMachOSection("__DWARF", "__debug_frame", MCSectionMachO::S_ATTR_DEBUG,
586                     SectionKind::getMetadata());
587   DwarfPubNamesSection =
588     getMachOSection("__DWARF", "__debug_pubnames", MCSectionMachO::S_ATTR_DEBUG,
589                     SectionKind::getMetadata());
590   DwarfPubTypesSection =
591     getMachOSection("__DWARF", "__debug_pubtypes", MCSectionMachO::S_ATTR_DEBUG,
592                     SectionKind::getMetadata());
593   DwarfStrSection =
594     getMachOSection("__DWARF", "__debug_str", MCSectionMachO::S_ATTR_DEBUG,
595                     SectionKind::getMetadata());
596   DwarfLocSection =
597     getMachOSection("__DWARF", "__debug_loc", MCSectionMachO::S_ATTR_DEBUG,
598                     SectionKind::getMetadata());
599   DwarfARangesSection =
600     getMachOSection("__DWARF", "__debug_aranges", MCSectionMachO::S_ATTR_DEBUG,
601                     SectionKind::getMetadata());
602   DwarfRangesSection =
603     getMachOSection("__DWARF", "__debug_ranges", MCSectionMachO::S_ATTR_DEBUG,
604                     SectionKind::getMetadata());
605   DwarfMacroInfoSection =
606     getMachOSection("__DWARF", "__debug_macinfo", MCSectionMachO::S_ATTR_DEBUG,
607                     SectionKind::getMetadata());
608   DwarfDebugInlineSection =
609     getMachOSection("__DWARF", "__debug_inlined", MCSectionMachO::S_ATTR_DEBUG,
610                     SectionKind::getMetadata());
611 }
612 
613 const MCSection *TargetLoweringObjectFileMachO::
614 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
615                          Mangler *Mang, const TargetMachine &TM) const {
616   // Parse the section specifier and create it if valid.
617   StringRef Segment, Section;
618   unsigned TAA, StubSize;
619   std::string ErrorCode =
620     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
621                                           TAA, StubSize);
622   if (!ErrorCode.empty()) {
623     // If invalid, report the error with llvm_report_error.
624     llvm_report_error("Global variable '" + GV->getNameStr() +
625                       "' has an invalid section specifier '" + GV->getSection()+
626                       "': " + ErrorCode + ".");
627     // Fall back to dropping it into the data section.
628     return DataSection;
629   }
630 
631   // Get the section.
632   const MCSectionMachO *S =
633     getMachOSection(Segment, Section, TAA, StubSize, Kind);
634 
635   // Okay, now that we got the section, verify that the TAA & StubSize agree.
636   // If the user declared multiple globals with different section flags, we need
637   // to reject it here.
638   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
639     // If invalid, report the error with llvm_report_error.
640     llvm_report_error("Global variable '" + GV->getNameStr() +
641                       "' section type or attributes does not match previous"
642                       " section specifier");
643   }
644 
645   return S;
646 }
647 
648 const MCSection *TargetLoweringObjectFileMachO::
649 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
650                        Mangler *Mang, const TargetMachine &TM) const {
651   assert(!Kind.isThreadLocal() && "Darwin doesn't support TLS");
652 
653   if (Kind.isText())
654     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
655 
656   // If this is weak/linkonce, put this in a coalescable section, either in text
657   // or data depending on if it is writable.
658   if (GV->isWeakForLinker()) {
659     if (Kind.isReadOnly())
660       return ConstTextCoalSection;
661     return DataCoalSection;
662   }
663 
664   // FIXME: Alignment check should be handled by section classifier.
665   if (Kind.isMergeable1ByteCString() &&
666       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
667     return CStringSection;
668 
669   // Do not put 16-bit arrays in the UString section if they have an
670   // externally visible label, this runs into issues with certain linker
671   // versions.
672   if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
673       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
674     return UStringSection;
675 
676   if (Kind.isMergeableConst()) {
677     if (Kind.isMergeableConst4())
678       return FourByteConstantSection;
679     if (Kind.isMergeableConst8())
680       return EightByteConstantSection;
681     if (Kind.isMergeableConst16() && SixteenByteConstantSection)
682       return SixteenByteConstantSection;
683   }
684 
685   // Otherwise, if it is readonly, but not something we can specially optimize,
686   // just drop it in .const.
687   if (Kind.isReadOnly())
688     return ReadOnlySection;
689 
690   // If this is marked const, put it into a const section.  But if the dynamic
691   // linker needs to write to it, put it in the data segment.
692   if (Kind.isReadOnlyWithRel())
693     return ConstDataSection;
694 
695   // Put zero initialized globals with strong external linkage in the
696   // DATA, __common section with the .zerofill directive.
697   if (Kind.isBSSExtern())
698     return DataCommonSection;
699 
700   // Put zero initialized globals with local linkage in __DATA,__bss directive
701   // with the .zerofill directive (aka .lcomm).
702   if (Kind.isBSSLocal())
703     return DataBSSSection;
704 
705   // Otherwise, just drop the variable in the normal data section.
706   return DataSection;
707 }
708 
709 const MCSection *
710 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
711   // If this constant requires a relocation, we have to put it in the data
712   // segment, not in the text segment.
713   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
714     return ConstDataSection;
715 
716   if (Kind.isMergeableConst4())
717     return FourByteConstantSection;
718   if (Kind.isMergeableConst8())
719     return EightByteConstantSection;
720   if (Kind.isMergeableConst16() && SixteenByteConstantSection)
721     return SixteenByteConstantSection;
722   return ReadOnlySection;  // .const
723 }
724 
725 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
726 /// not to emit the UsedDirective for some symbols in llvm.used.
727 // FIXME: REMOVE this (rdar://7071300)
728 bool TargetLoweringObjectFileMachO::
729 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
730   /// On Darwin, internally linked data beginning with "L" or "l" does not have
731   /// the directive emitted (this occurs in ObjC metadata).
732   if (!GV) return false;
733 
734   // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
735   if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
736     // FIXME: ObjC metadata is currently emitted as internal symbols that have
737     // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
738     // this horrible hack can go away.
739     SmallString<64> Name;
740     Mang->getNameWithPrefix(Name, GV, false);
741     if (Name[0] == 'L' || Name[0] == 'l')
742       return false;
743   }
744 
745   return true;
746 }
747 
748 const MCExpr *TargetLoweringObjectFileMachO::
749 getSymbolForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
750                              MachineModuleInfo *MMI, unsigned Encoding) const {
751   // The mach-o version of this method defaults to returning a stub reference.
752 
753   if (Encoding & DW_EH_PE_indirect) {
754     MachineModuleInfoMachO &MachOMMI =
755       MMI->getObjFileInfo<MachineModuleInfoMachO>();
756 
757     SmallString<128> Name;
758     Mang->getNameWithPrefix(Name, GV, true);
759     Name += "$non_lazy_ptr";
760 
761     // Add information about the stub reference to MachOMMI so that the stub
762     // gets emitted by the asmprinter.
763     MCSymbol *Sym = getContext().GetOrCreateTemporarySymbol(Name.str());
764     MCSymbol *&StubSym = MachOMMI.getGVStubEntry(Sym);
765     if (StubSym == 0) {
766       Name.clear();
767       Mang->getNameWithPrefix(Name, GV, false);
768       if (GV->hasPrivateLinkage())
769         StubSym = getContext().GetOrCreateTemporarySymbol(Name.str());
770       else
771         StubSym = getContext().GetOrCreateSymbol(Name.str());
772     }
773 
774     return TargetLoweringObjectFile::
775       getSymbolForDwarfReference(Sym, MMI,
776                                  Encoding & ~dwarf::DW_EH_PE_indirect);
777   }
778 
779   return TargetLoweringObjectFile::
780     getSymbolForDwarfGlobalReference(GV, Mang, MMI, Encoding);
781 }
782 
783 unsigned TargetLoweringObjectFileMachO::getPersonalityEncoding() const {
784   return DW_EH_PE_indirect | DW_EH_PE_pcrel | DW_EH_PE_sdata4;
785 }
786 
787 unsigned TargetLoweringObjectFileMachO::getLSDAEncoding() const {
788   return DW_EH_PE_pcrel;
789 }
790 
791 unsigned TargetLoweringObjectFileMachO::getFDEEncoding() const {
792   return DW_EH_PE_pcrel;
793 }
794 
795 unsigned TargetLoweringObjectFileMachO::getTTypeEncoding() const {
796   return DW_EH_PE_absptr;
797 }
798 
799 //===----------------------------------------------------------------------===//
800 //                                  COFF
801 //===----------------------------------------------------------------------===//
802 
803 typedef StringMap<const MCSectionCOFF*> COFFUniqueMapTy;
804 
805 TargetLoweringObjectFileCOFF::~TargetLoweringObjectFileCOFF() {
806   delete (COFFUniqueMapTy*)UniquingMap;
807 }
808 
809 
810 const MCSection *TargetLoweringObjectFileCOFF::
811 getCOFFSection(StringRef Name, bool isDirective, SectionKind Kind) const {
812   // Create the map if it doesn't already exist.
813   if (UniquingMap == 0)
814     UniquingMap = new MachOUniqueMapTy();
815   COFFUniqueMapTy &Map = *(COFFUniqueMapTy*)UniquingMap;
816 
817   // Do the lookup, if we have a hit, return it.
818   const MCSectionCOFF *&Entry = Map[Name];
819   if (Entry) return Entry;
820 
821   return Entry = MCSectionCOFF::Create(Name, isDirective, Kind, getContext());
822 }
823 
824 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
825                                               const TargetMachine &TM) {
826   if (UniquingMap != 0)
827     ((COFFUniqueMapTy*)UniquingMap)->clear();
828   TargetLoweringObjectFile::Initialize(Ctx, TM);
829   TextSection = getCOFFSection("\t.text", true, SectionKind::getText());
830   DataSection = getCOFFSection("\t.data", true, SectionKind::getDataRel());
831   StaticCtorSection =
832     getCOFFSection(".ctors", false, SectionKind::getDataRel());
833   StaticDtorSection =
834     getCOFFSection(".dtors", false, SectionKind::getDataRel());
835 
836   // FIXME: We're emitting LSDA info into a readonly section on COFF, even
837   // though it contains relocatable pointers.  In PIC mode, this is probably a
838   // big runtime hit for C++ apps.  Either the contents of the LSDA need to be
839   // adjusted or this should be a data section.
840   LSDASection =
841     getCOFFSection(".gcc_except_table", false, SectionKind::getReadOnly());
842   EHFrameSection =
843     getCOFFSection(".eh_frame", false, SectionKind::getDataRel());
844 
845   // Debug info.
846   // FIXME: Don't use 'directive' mode here.
847   DwarfAbbrevSection =
848     getCOFFSection("\t.section\t.debug_abbrev,\"dr\"",
849                    true, SectionKind::getMetadata());
850   DwarfInfoSection =
851     getCOFFSection("\t.section\t.debug_info,\"dr\"",
852                    true, SectionKind::getMetadata());
853   DwarfLineSection =
854     getCOFFSection("\t.section\t.debug_line,\"dr\"",
855                    true, SectionKind::getMetadata());
856   DwarfFrameSection =
857     getCOFFSection("\t.section\t.debug_frame,\"dr\"",
858                    true, SectionKind::getMetadata());
859   DwarfPubNamesSection =
860     getCOFFSection("\t.section\t.debug_pubnames,\"dr\"",
861                    true, SectionKind::getMetadata());
862   DwarfPubTypesSection =
863     getCOFFSection("\t.section\t.debug_pubtypes,\"dr\"",
864                    true, SectionKind::getMetadata());
865   DwarfStrSection =
866     getCOFFSection("\t.section\t.debug_str,\"dr\"",
867                    true, SectionKind::getMetadata());
868   DwarfLocSection =
869     getCOFFSection("\t.section\t.debug_loc,\"dr\"",
870                    true, SectionKind::getMetadata());
871   DwarfARangesSection =
872     getCOFFSection("\t.section\t.debug_aranges,\"dr\"",
873                    true, SectionKind::getMetadata());
874   DwarfRangesSection =
875     getCOFFSection("\t.section\t.debug_ranges,\"dr\"",
876                    true, SectionKind::getMetadata());
877   DwarfMacroInfoSection =
878     getCOFFSection("\t.section\t.debug_macinfo,\"dr\"",
879                    true, SectionKind::getMetadata());
880 }
881 
882 const MCSection *TargetLoweringObjectFileCOFF::
883 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
884                          Mangler *Mang, const TargetMachine &TM) const {
885   return getCOFFSection(GV->getSection(), false, Kind);
886 }
887 
888 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
889   if (Kind.isText())
890     return ".text$linkonce";
891   if (Kind.isWriteable())
892     return ".data$linkonce";
893   return ".rdata$linkonce";
894 }
895 
896 
897 const MCSection *TargetLoweringObjectFileCOFF::
898 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
899                        Mangler *Mang, const TargetMachine &TM) const {
900   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
901 
902   // If this global is linkonce/weak and the target handles this by emitting it
903   // into a 'uniqued' section name, create and return the section now.
904   if (GV->isWeakForLinker()) {
905     const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
906     SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
907     Mang->getNameWithPrefix(Name, GV, false);
908     return getCOFFSection(Name.str(), false, Kind);
909   }
910 
911   if (Kind.isText())
912     return getTextSection();
913 
914   return getDataSection();
915 }
916 
917