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/MCSectionCOFF.h"
26 #include "llvm/MC/MCSymbol.h"
27 #include "llvm/Target/Mangler.h"
28 #include "llvm/Target/TargetData.h"
29 #include "llvm/Target/TargetMachine.h"
30 #include "llvm/Target/TargetOptions.h"
31 #include "llvm/Support/Dwarf.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/raw_ostream.h"
34 #include "llvm/ADT/SmallString.h"
35 #include "llvm/ADT/StringExtras.h"
36 using namespace llvm;
37 using namespace dwarf;
38 
39 //===----------------------------------------------------------------------===//
40 //                                  ELF
41 //===----------------------------------------------------------------------===//
42 
43 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
44                                              const TargetMachine &TM) {
45   TargetLoweringObjectFile::Initialize(Ctx, TM);
46 
47   BSSSection =
48     getContext().getELFSection(".bss", MCSectionELF::SHT_NOBITS,
49                                MCSectionELF::SHF_WRITE |MCSectionELF::SHF_ALLOC,
50                                SectionKind::getBSS());
51 
52   TextSection =
53     getContext().getELFSection(".text", MCSectionELF::SHT_PROGBITS,
54                                MCSectionELF::SHF_EXECINSTR |
55                                MCSectionELF::SHF_ALLOC,
56                                SectionKind::getText());
57 
58   DataSection =
59     getContext().getELFSection(".data", MCSectionELF::SHT_PROGBITS,
60                                MCSectionELF::SHF_WRITE |MCSectionELF::SHF_ALLOC,
61                                SectionKind::getDataRel());
62 
63   ReadOnlySection =
64     getContext().getELFSection(".rodata", MCSectionELF::SHT_PROGBITS,
65                                MCSectionELF::SHF_ALLOC,
66                                SectionKind::getReadOnly());
67 
68   TLSDataSection =
69     getContext().getELFSection(".tdata", MCSectionELF::SHT_PROGBITS,
70                                MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
71                                MCSectionELF::SHF_WRITE,
72                                SectionKind::getThreadData());
73 
74   TLSBSSSection =
75     getContext().getELFSection(".tbss", MCSectionELF::SHT_NOBITS,
76                                MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
77                                MCSectionELF::SHF_WRITE,
78                                SectionKind::getThreadBSS());
79 
80   DataRelSection =
81     getContext().getELFSection(".data.rel", MCSectionELF::SHT_PROGBITS,
82                                MCSectionELF::SHF_ALLOC |MCSectionELF::SHF_WRITE,
83                                SectionKind::getDataRel());
84 
85   DataRelLocalSection =
86     getContext().getELFSection(".data.rel.local", MCSectionELF::SHT_PROGBITS,
87                                MCSectionELF::SHF_ALLOC |MCSectionELF::SHF_WRITE,
88                                SectionKind::getDataRelLocal());
89 
90   DataRelROSection =
91     getContext().getELFSection(".data.rel.ro", MCSectionELF::SHT_PROGBITS,
92                                MCSectionELF::SHF_ALLOC |MCSectionELF::SHF_WRITE,
93                                SectionKind::getReadOnlyWithRel());
94 
95   DataRelROLocalSection =
96     getContext().getELFSection(".data.rel.ro.local", MCSectionELF::SHT_PROGBITS,
97                                MCSectionELF::SHF_ALLOC |MCSectionELF::SHF_WRITE,
98                                SectionKind::getReadOnlyWithRelLocal());
99 
100   MergeableConst4Section =
101     getContext().getELFSection(".rodata.cst4", MCSectionELF::SHT_PROGBITS,
102                                MCSectionELF::SHF_ALLOC |MCSectionELF::SHF_MERGE,
103                                SectionKind::getMergeableConst4());
104 
105   MergeableConst8Section =
106     getContext().getELFSection(".rodata.cst8", MCSectionELF::SHT_PROGBITS,
107                                MCSectionELF::SHF_ALLOC |MCSectionELF::SHF_MERGE,
108                                SectionKind::getMergeableConst8());
109 
110   MergeableConst16Section =
111     getContext().getELFSection(".rodata.cst16", MCSectionELF::SHT_PROGBITS,
112                                MCSectionELF::SHF_ALLOC |MCSectionELF::SHF_MERGE,
113                                SectionKind::getMergeableConst16());
114 
115   StaticCtorSection =
116     getContext().getELFSection(".ctors", MCSectionELF::SHT_PROGBITS,
117                                MCSectionELF::SHF_ALLOC |MCSectionELF::SHF_WRITE,
118                                SectionKind::getDataRel());
119 
120   StaticDtorSection =
121     getContext().getELFSection(".dtors", MCSectionELF::SHT_PROGBITS,
122                                MCSectionELF::SHF_ALLOC |MCSectionELF::SHF_WRITE,
123                                SectionKind::getDataRel());
124 
125   // Exception Handling Sections.
126 
127   // FIXME: We're emitting LSDA info into a readonly section on ELF, even though
128   // it contains relocatable pointers.  In PIC mode, this is probably a big
129   // runtime hit for C++ apps.  Either the contents of the LSDA need to be
130   // adjusted or this should be a data section.
131   LSDASection =
132     getContext().getELFSection(".gcc_except_table", MCSectionELF::SHT_PROGBITS,
133                                MCSectionELF::SHF_ALLOC,
134                                SectionKind::getReadOnly());
135   EHFrameSection =
136     getContext().getELFSection(".eh_frame", MCSectionELF::SHT_PROGBITS,
137                                MCSectionELF::SHF_ALLOC |MCSectionELF::SHF_WRITE,
138                                SectionKind::getDataRel());
139 
140   // Debug Info Sections.
141   DwarfAbbrevSection =
142     getContext().getELFSection(".debug_abbrev", MCSectionELF::SHT_PROGBITS, 0,
143                                SectionKind::getMetadata());
144   DwarfInfoSection =
145     getContext().getELFSection(".debug_info", MCSectionELF::SHT_PROGBITS, 0,
146                                SectionKind::getMetadata());
147   DwarfLineSection =
148     getContext().getELFSection(".debug_line", MCSectionELF::SHT_PROGBITS, 0,
149                                SectionKind::getMetadata());
150   DwarfFrameSection =
151     getContext().getELFSection(".debug_frame", MCSectionELF::SHT_PROGBITS, 0,
152                                SectionKind::getMetadata());
153   DwarfPubNamesSection =
154     getContext().getELFSection(".debug_pubnames", MCSectionELF::SHT_PROGBITS, 0,
155                                SectionKind::getMetadata());
156   DwarfPubTypesSection =
157     getContext().getELFSection(".debug_pubtypes", MCSectionELF::SHT_PROGBITS, 0,
158                                SectionKind::getMetadata());
159   DwarfStrSection =
160     getContext().getELFSection(".debug_str", MCSectionELF::SHT_PROGBITS, 0,
161                                SectionKind::getMetadata());
162   DwarfLocSection =
163     getContext().getELFSection(".debug_loc", MCSectionELF::SHT_PROGBITS, 0,
164                                SectionKind::getMetadata());
165   DwarfARangesSection =
166     getContext().getELFSection(".debug_aranges", MCSectionELF::SHT_PROGBITS, 0,
167                                SectionKind::getMetadata());
168   DwarfRangesSection =
169     getContext().getELFSection(".debug_ranges", MCSectionELF::SHT_PROGBITS, 0,
170                                SectionKind::getMetadata());
171   DwarfMacroInfoSection =
172     getContext().getELFSection(".debug_macinfo", MCSectionELF::SHT_PROGBITS, 0,
173                                SectionKind::getMetadata());
174 }
175 
176 
177 static SectionKind
178 getELFKindForNamedSection(StringRef Name, SectionKind K) {
179   if (Name.empty() || Name[0] != '.') return K;
180 
181   // Some lame default implementation based on some magic section names.
182   if (Name == ".bss" ||
183       Name.startswith(".bss.") ||
184       Name.startswith(".gnu.linkonce.b.") ||
185       Name.startswith(".llvm.linkonce.b.") ||
186       Name == ".sbss" ||
187       Name.startswith(".sbss.") ||
188       Name.startswith(".gnu.linkonce.sb.") ||
189       Name.startswith(".llvm.linkonce.sb."))
190     return SectionKind::getBSS();
191 
192   if (Name == ".tdata" ||
193       Name.startswith(".tdata.") ||
194       Name.startswith(".gnu.linkonce.td.") ||
195       Name.startswith(".llvm.linkonce.td."))
196     return SectionKind::getThreadData();
197 
198   if (Name == ".tbss" ||
199       Name.startswith(".tbss.") ||
200       Name.startswith(".gnu.linkonce.tb.") ||
201       Name.startswith(".llvm.linkonce.tb."))
202     return SectionKind::getThreadBSS();
203 
204   return K;
205 }
206 
207 
208 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
209 
210   if (Name == ".init_array")
211     return MCSectionELF::SHT_INIT_ARRAY;
212 
213   if (Name == ".fini_array")
214     return MCSectionELF::SHT_FINI_ARRAY;
215 
216   if (Name == ".preinit_array")
217     return MCSectionELF::SHT_PREINIT_ARRAY;
218 
219   if (K.isBSS() || K.isThreadBSS())
220     return MCSectionELF::SHT_NOBITS;
221 
222   return MCSectionELF::SHT_PROGBITS;
223 }
224 
225 
226 static unsigned
227 getELFSectionFlags(SectionKind K) {
228   unsigned Flags = 0;
229 
230   if (!K.isMetadata())
231     Flags |= MCSectionELF::SHF_ALLOC;
232 
233   if (K.isText())
234     Flags |= MCSectionELF::SHF_EXECINSTR;
235 
236   if (K.isWriteable())
237     Flags |= MCSectionELF::SHF_WRITE;
238 
239   if (K.isThreadLocal())
240     Flags |= MCSectionELF::SHF_TLS;
241 
242   // K.isMergeableConst() is left out to honour PR4650
243   if (K.isMergeableCString() || K.isMergeableConst4() ||
244       K.isMergeableConst8() || K.isMergeableConst16())
245     Flags |= MCSectionELF::SHF_MERGE;
246 
247   if (K.isMergeableCString())
248     Flags |= MCSectionELF::SHF_STRINGS;
249 
250   return Flags;
251 }
252 
253 
254 const MCSection *TargetLoweringObjectFileELF::
255 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
256                          Mangler *Mang, const TargetMachine &TM) const {
257   StringRef SectionName = GV->getSection();
258 
259   // Infer section flags from the section name if we can.
260   Kind = getELFKindForNamedSection(SectionName, Kind);
261 
262   return getContext().getELFSection(SectionName,
263                                     getELFSectionType(SectionName, Kind),
264                                     getELFSectionFlags(Kind), Kind, true);
265 }
266 
267 static const char *getSectionPrefixForUniqueGlobal(SectionKind Kind) {
268   if (Kind.isText())                 return ".gnu.linkonce.t.";
269   if (Kind.isReadOnly())             return ".gnu.linkonce.r.";
270 
271   if (Kind.isThreadData())           return ".gnu.linkonce.td.";
272   if (Kind.isThreadBSS())            return ".gnu.linkonce.tb.";
273 
274   if (Kind.isDataNoRel())            return ".gnu.linkonce.d.";
275   if (Kind.isDataRelLocal())         return ".gnu.linkonce.d.rel.local.";
276   if (Kind.isDataRel())              return ".gnu.linkonce.d.rel.";
277   if (Kind.isReadOnlyWithRelLocal()) return ".gnu.linkonce.d.rel.ro.local.";
278 
279   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
280   return ".gnu.linkonce.d.rel.ro.";
281 }
282 
283 /// getSectionPrefixForGlobal - Return the section prefix name used by options
284 /// FunctionsSections and DataSections.
285 static const char *getSectionPrefixForGlobal(SectionKind Kind) {
286   if (Kind.isText())                 return ".text.";
287   if (Kind.isReadOnly())             return ".rodata.";
288 
289   if (Kind.isThreadData())           return ".tdata.";
290   if (Kind.isThreadBSS())            return ".tbss.";
291 
292   if (Kind.isDataNoRel())            return ".data.";
293   if (Kind.isDataRelLocal())         return ".data.rel.local.";
294   if (Kind.isDataRel())              return ".data.rel.";
295   if (Kind.isReadOnlyWithRelLocal()) return ".data.rel.ro.local.";
296 
297   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
298   return ".data.rel.ro.";
299 }
300 
301 
302 const MCSection *TargetLoweringObjectFileELF::
303 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
304                        Mangler *Mang, const TargetMachine &TM) const {
305   // If we have -ffunction-section or -fdata-section then we should emit the
306   // global value to a uniqued section specifically for it.
307   bool EmitUniquedSection;
308   if (Kind.isText())
309     EmitUniquedSection = TM.getFunctionSections();
310   else
311     EmitUniquedSection = TM.getDataSections();
312 
313   // If this global is linkonce/weak and the target handles this by emitting it
314   // into a 'uniqued' section name, create and return the section now.
315   if ((GV->isWeakForLinker() || EmitUniquedSection) &&
316       !Kind.isCommon() && !Kind.isBSS()) {
317     const char *Prefix;
318     if (GV->isWeakForLinker())
319       Prefix = getSectionPrefixForUniqueGlobal(Kind);
320     else {
321       assert(EmitUniquedSection);
322       Prefix = getSectionPrefixForGlobal(Kind);
323     }
324 
325     SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
326     MCSymbol *Sym = Mang->getSymbol(GV);
327     Name.append(Sym->getName().begin(), Sym->getName().end());
328     return getContext().getELFSection(Name.str(),
329                                       getELFSectionType(Name.str(), Kind),
330                                       getELFSectionFlags(Kind), Kind);
331   }
332 
333   if (Kind.isText()) return TextSection;
334 
335   if (Kind.isMergeable1ByteCString() ||
336       Kind.isMergeable2ByteCString() ||
337       Kind.isMergeable4ByteCString()) {
338 
339     // We also need alignment here.
340     // FIXME: this is getting the alignment of the character, not the
341     // alignment of the global!
342     unsigned Align =
343       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV));
344 
345     const char *SizeSpec = ".rodata.str1.";
346     if (Kind.isMergeable2ByteCString())
347       SizeSpec = ".rodata.str2.";
348     else if (Kind.isMergeable4ByteCString())
349       SizeSpec = ".rodata.str4.";
350     else
351       assert(Kind.isMergeable1ByteCString() && "unknown string width");
352 
353 
354     std::string Name = SizeSpec + utostr(Align);
355     return getContext().getELFSection(Name, MCSectionELF::SHT_PROGBITS,
356                                       MCSectionELF::SHF_ALLOC |
357                                       MCSectionELF::SHF_MERGE |
358                                       MCSectionELF::SHF_STRINGS,
359                                       Kind);
360   }
361 
362   if (Kind.isMergeableConst()) {
363     if (Kind.isMergeableConst4() && MergeableConst4Section)
364       return MergeableConst4Section;
365     if (Kind.isMergeableConst8() && MergeableConst8Section)
366       return MergeableConst8Section;
367     if (Kind.isMergeableConst16() && MergeableConst16Section)
368       return MergeableConst16Section;
369     return ReadOnlySection;  // .const
370   }
371 
372   if (Kind.isReadOnly())             return ReadOnlySection;
373 
374   if (Kind.isThreadData())           return TLSDataSection;
375   if (Kind.isThreadBSS())            return TLSBSSSection;
376 
377   // Note: we claim that common symbols are put in BSSSection, but they are
378   // really emitted with the magic .comm directive, which creates a symbol table
379   // entry but not a section.
380   if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
381 
382   if (Kind.isDataNoRel())            return DataSection;
383   if (Kind.isDataRelLocal())         return DataRelLocalSection;
384   if (Kind.isDataRel())              return DataRelSection;
385   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
386 
387   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
388   return DataRelROSection;
389 }
390 
391 /// getSectionForConstant - Given a mergeable constant with the
392 /// specified size and relocation information, return a section that it
393 /// should be placed in.
394 const MCSection *TargetLoweringObjectFileELF::
395 getSectionForConstant(SectionKind Kind) const {
396   if (Kind.isMergeableConst4() && MergeableConst4Section)
397     return MergeableConst4Section;
398   if (Kind.isMergeableConst8() && MergeableConst8Section)
399     return MergeableConst8Section;
400   if (Kind.isMergeableConst16() && MergeableConst16Section)
401     return MergeableConst16Section;
402   if (Kind.isReadOnly())
403     return ReadOnlySection;
404 
405   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
406   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
407   return DataRelROSection;
408 }
409 
410 const MCExpr *TargetLoweringObjectFileELF::
411 getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
412                                MachineModuleInfo *MMI,
413                                unsigned Encoding, MCStreamer &Streamer) const {
414 
415   if (Encoding & dwarf::DW_EH_PE_indirect) {
416     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
417 
418     SmallString<128> Name;
419     Mang->getNameWithPrefix(Name, GV, true);
420     Name += ".DW.stub";
421 
422     // Add information about the stub reference to ELFMMI so that the stub
423     // gets emitted by the asmprinter.
424     MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
425     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
426     if (StubSym.getPointer() == 0) {
427       MCSymbol *Sym = Mang->getSymbol(GV);
428       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
429     }
430 
431     return TargetLoweringObjectFile::
432       getExprForDwarfReference(SSym, Mang, MMI,
433                                Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
434   }
435 
436   return TargetLoweringObjectFile::
437     getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, Streamer);
438 }
439 
440 //===----------------------------------------------------------------------===//
441 //                                 MachO
442 //===----------------------------------------------------------------------===//
443 
444 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
445                                                const TargetMachine &TM) {
446   // _foo.eh symbols are currently always exported so that the linker knows
447   // about them.  This is not necessary on 10.6 and later, but it
448   // doesn't hurt anything.
449   // FIXME: I need to get this from Triple.
450   IsFunctionEHSymbolGlobal = true;
451   IsFunctionEHFrameSymbolPrivate = false;
452   SupportsWeakOmittedEHFrame = false;
453 
454   TargetLoweringObjectFile::Initialize(Ctx, TM);
455 
456   TextSection // .text
457     = getContext().getMachOSection("__TEXT", "__text",
458                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
459                                    SectionKind::getText());
460   DataSection // .data
461     = getContext().getMachOSection("__DATA", "__data", 0,
462                                    SectionKind::getDataRel());
463 
464   TLSDataSection // .tdata
465     = getContext().getMachOSection("__DATA", "__thread_data",
466                                    MCSectionMachO::S_THREAD_LOCAL_REGULAR,
467                                    SectionKind::getDataRel());
468   TLSBSSSection // .tbss
469     = getContext().getMachOSection("__DATA", "__thread_bss",
470                                    MCSectionMachO::S_THREAD_LOCAL_ZEROFILL,
471                                    SectionKind::getThreadBSS());
472 
473   // TODO: Verify datarel below.
474   TLSTLVSection // .tlv
475     = getContext().getMachOSection("__DATA", "__thread_vars",
476                                    MCSectionMachO::S_THREAD_LOCAL_VARIABLES,
477                                    SectionKind::getDataRel());
478   CStringSection // .cstring
479     = getContext().getMachOSection("__TEXT", "__cstring",
480                                    MCSectionMachO::S_CSTRING_LITERALS,
481                                    SectionKind::getMergeable1ByteCString());
482   UStringSection
483     = getContext().getMachOSection("__TEXT","__ustring", 0,
484                                    SectionKind::getMergeable2ByteCString());
485   FourByteConstantSection // .literal4
486     = getContext().getMachOSection("__TEXT", "__literal4",
487                                    MCSectionMachO::S_4BYTE_LITERALS,
488                                    SectionKind::getMergeableConst4());
489   EightByteConstantSection // .literal8
490     = getContext().getMachOSection("__TEXT", "__literal8",
491                                    MCSectionMachO::S_8BYTE_LITERALS,
492                                    SectionKind::getMergeableConst8());
493 
494   // ld_classic doesn't support .literal16 in 32-bit mode, and ld64 falls back
495   // to using it in -static mode.
496   SixteenByteConstantSection = 0;
497   if (TM.getRelocationModel() != Reloc::Static &&
498       TM.getTargetData()->getPointerSize() == 32)
499     SixteenByteConstantSection =   // .literal16
500       getContext().getMachOSection("__TEXT", "__literal16",
501                                    MCSectionMachO::S_16BYTE_LITERALS,
502                                    SectionKind::getMergeableConst16());
503 
504   ReadOnlySection  // .const
505     = getContext().getMachOSection("__TEXT", "__const", 0,
506                                    SectionKind::getReadOnly());
507 
508   TextCoalSection
509     = getContext().getMachOSection("__TEXT", "__textcoal_nt",
510                                    MCSectionMachO::S_COALESCED |
511                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
512                                    SectionKind::getText());
513   ConstTextCoalSection
514     = getContext().getMachOSection("__TEXT", "__const_coal",
515                                    MCSectionMachO::S_COALESCED,
516                                    SectionKind::getText());
517   ConstDataCoalSection
518     = getContext().getMachOSection("__DATA","__const_coal",
519                                    MCSectionMachO::S_COALESCED,
520                                    SectionKind::getText());
521   ConstDataSection  // .const_data
522     = getContext().getMachOSection("__DATA", "__const", 0,
523                                    SectionKind::getReadOnlyWithRel());
524   DataCoalSection
525     = getContext().getMachOSection("__DATA","__datacoal_nt",
526                                    MCSectionMachO::S_COALESCED,
527                                    SectionKind::getDataRel());
528   DataCommonSection
529     = getContext().getMachOSection("__DATA","__common",
530                                    MCSectionMachO::S_ZEROFILL,
531                                    SectionKind::getBSS());
532   DataBSSSection
533     = getContext().getMachOSection("__DATA","__bss", MCSectionMachO::S_ZEROFILL,
534                                    SectionKind::getBSS());
535 
536 
537   LazySymbolPointerSection
538     = getContext().getMachOSection("__DATA", "__la_symbol_ptr",
539                                    MCSectionMachO::S_LAZY_SYMBOL_POINTERS,
540                                    SectionKind::getMetadata());
541   NonLazySymbolPointerSection
542     = getContext().getMachOSection("__DATA", "__nl_symbol_ptr",
543                                    MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS,
544                                    SectionKind::getMetadata());
545 
546   if (TM.getRelocationModel() == Reloc::Static) {
547     StaticCtorSection
548       = getContext().getMachOSection("__TEXT", "__constructor", 0,
549                                      SectionKind::getDataRel());
550     StaticDtorSection
551       = getContext().getMachOSection("__TEXT", "__destructor", 0,
552                                      SectionKind::getDataRel());
553   } else {
554     StaticCtorSection
555       = getContext().getMachOSection("__DATA", "__mod_init_func",
556                                      MCSectionMachO::S_MOD_INIT_FUNC_POINTERS,
557                                      SectionKind::getDataRel());
558     StaticDtorSection
559       = getContext().getMachOSection("__DATA", "__mod_term_func",
560                                      MCSectionMachO::S_MOD_TERM_FUNC_POINTERS,
561                                      SectionKind::getDataRel());
562   }
563 
564   // Exception Handling.
565   LSDASection = getContext().getMachOSection("__TEXT", "__gcc_except_tab", 0,
566                                              SectionKind::getReadOnlyWithRel());
567   EHFrameSection =
568     getContext().getMachOSection("__TEXT", "__eh_frame",
569                                  MCSectionMachO::S_COALESCED |
570                                  MCSectionMachO::S_ATTR_NO_TOC |
571                                  MCSectionMachO::S_ATTR_STRIP_STATIC_SYMS |
572                                  MCSectionMachO::S_ATTR_LIVE_SUPPORT,
573                                  SectionKind::getReadOnly());
574 
575   // Debug Information.
576   DwarfAbbrevSection =
577     getContext().getMachOSection("__DWARF", "__debug_abbrev",
578                                  MCSectionMachO::S_ATTR_DEBUG,
579                                  SectionKind::getMetadata());
580   DwarfInfoSection =
581     getContext().getMachOSection("__DWARF", "__debug_info",
582                                  MCSectionMachO::S_ATTR_DEBUG,
583                                  SectionKind::getMetadata());
584   DwarfLineSection =
585     getContext().getMachOSection("__DWARF", "__debug_line",
586                                  MCSectionMachO::S_ATTR_DEBUG,
587                                  SectionKind::getMetadata());
588   DwarfFrameSection =
589     getContext().getMachOSection("__DWARF", "__debug_frame",
590                                  MCSectionMachO::S_ATTR_DEBUG,
591                                  SectionKind::getMetadata());
592   DwarfPubNamesSection =
593     getContext().getMachOSection("__DWARF", "__debug_pubnames",
594                                  MCSectionMachO::S_ATTR_DEBUG,
595                                  SectionKind::getMetadata());
596   DwarfPubTypesSection =
597     getContext().getMachOSection("__DWARF", "__debug_pubtypes",
598                                  MCSectionMachO::S_ATTR_DEBUG,
599                                  SectionKind::getMetadata());
600   DwarfStrSection =
601     getContext().getMachOSection("__DWARF", "__debug_str",
602                                  MCSectionMachO::S_ATTR_DEBUG,
603                                  SectionKind::getMetadata());
604   DwarfLocSection =
605     getContext().getMachOSection("__DWARF", "__debug_loc",
606                                  MCSectionMachO::S_ATTR_DEBUG,
607                                  SectionKind::getMetadata());
608   DwarfARangesSection =
609     getContext().getMachOSection("__DWARF", "__debug_aranges",
610                                  MCSectionMachO::S_ATTR_DEBUG,
611                                  SectionKind::getMetadata());
612   DwarfRangesSection =
613     getContext().getMachOSection("__DWARF", "__debug_ranges",
614                                  MCSectionMachO::S_ATTR_DEBUG,
615                                  SectionKind::getMetadata());
616   DwarfMacroInfoSection =
617     getContext().getMachOSection("__DWARF", "__debug_macinfo",
618                                  MCSectionMachO::S_ATTR_DEBUG,
619                                  SectionKind::getMetadata());
620   DwarfDebugInlineSection =
621     getContext().getMachOSection("__DWARF", "__debug_inlined",
622                                  MCSectionMachO::S_ATTR_DEBUG,
623                                  SectionKind::getMetadata());
624 }
625 
626 const MCSection *TargetLoweringObjectFileMachO::
627 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
628                          Mangler *Mang, const TargetMachine &TM) const {
629   // Parse the section specifier and create it if valid.
630   StringRef Segment, Section;
631   unsigned TAA, StubSize;
632   std::string ErrorCode =
633     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
634                                           TAA, StubSize);
635   if (!ErrorCode.empty()) {
636     // If invalid, report the error with report_fatal_error.
637     report_fatal_error("Global variable '" + GV->getNameStr() +
638                       "' has an invalid section specifier '" + GV->getSection()+
639                       "': " + ErrorCode + ".");
640     // Fall back to dropping it into the data section.
641     return DataSection;
642   }
643 
644   // Get the section.
645   const MCSectionMachO *S =
646     getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
647 
648   // Okay, now that we got the section, verify that the TAA & StubSize agree.
649   // If the user declared multiple globals with different section flags, we need
650   // to reject it here.
651   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
652     // If invalid, report the error with report_fatal_error.
653     report_fatal_error("Global variable '" + GV->getNameStr() +
654                       "' section type or attributes does not match previous"
655                       " section specifier");
656   }
657 
658   return S;
659 }
660 
661 const MCSection *TargetLoweringObjectFileMachO::
662 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
663                        Mangler *Mang, const TargetMachine &TM) const {
664   assert(!Kind.isThreadLocal() && "Darwin doesn't support TLS");
665 
666   if (Kind.isText())
667     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
668 
669   // If this is weak/linkonce, put this in a coalescable section, either in text
670   // or data depending on if it is writable.
671   if (GV->isWeakForLinker()) {
672     if (Kind.isReadOnly())
673       return ConstTextCoalSection;
674     return DataCoalSection;
675   }
676 
677   // FIXME: Alignment check should be handled by section classifier.
678   if (Kind.isMergeable1ByteCString() &&
679       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
680     return CStringSection;
681 
682   // Do not put 16-bit arrays in the UString section if they have an
683   // externally visible label, this runs into issues with certain linker
684   // versions.
685   if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
686       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
687     return UStringSection;
688 
689   if (Kind.isMergeableConst()) {
690     if (Kind.isMergeableConst4())
691       return FourByteConstantSection;
692     if (Kind.isMergeableConst8())
693       return EightByteConstantSection;
694     if (Kind.isMergeableConst16() && SixteenByteConstantSection)
695       return SixteenByteConstantSection;
696   }
697 
698   // Otherwise, if it is readonly, but not something we can specially optimize,
699   // just drop it in .const.
700   if (Kind.isReadOnly())
701     return ReadOnlySection;
702 
703   // If this is marked const, put it into a const section.  But if the dynamic
704   // linker needs to write to it, put it in the data segment.
705   if (Kind.isReadOnlyWithRel())
706     return ConstDataSection;
707 
708   // Put zero initialized globals with strong external linkage in the
709   // DATA, __common section with the .zerofill directive.
710   if (Kind.isBSSExtern())
711     return DataCommonSection;
712 
713   // Put zero initialized globals with local linkage in __DATA,__bss directive
714   // with the .zerofill directive (aka .lcomm).
715   if (Kind.isBSSLocal())
716     return DataBSSSection;
717 
718   // Otherwise, just drop the variable in the normal data section.
719   return DataSection;
720 }
721 
722 const MCSection *
723 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
724   // If this constant requires a relocation, we have to put it in the data
725   // segment, not in the text segment.
726   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
727     return ConstDataSection;
728 
729   if (Kind.isMergeableConst4())
730     return FourByteConstantSection;
731   if (Kind.isMergeableConst8())
732     return EightByteConstantSection;
733   if (Kind.isMergeableConst16() && SixteenByteConstantSection)
734     return SixteenByteConstantSection;
735   return ReadOnlySection;  // .const
736 }
737 
738 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
739 /// not to emit the UsedDirective for some symbols in llvm.used.
740 // FIXME: REMOVE this (rdar://7071300)
741 bool TargetLoweringObjectFileMachO::
742 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
743   /// On Darwin, internally linked data beginning with "L" or "l" does not have
744   /// the directive emitted (this occurs in ObjC metadata).
745   if (!GV) return false;
746 
747   // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
748   if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
749     // FIXME: ObjC metadata is currently emitted as internal symbols that have
750     // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
751     // this horrible hack can go away.
752     MCSymbol *Sym = Mang->getSymbol(GV);
753     if (Sym->getName()[0] == 'L' || Sym->getName()[0] == 'l')
754       return false;
755   }
756 
757   return true;
758 }
759 
760 const MCExpr *TargetLoweringObjectFileMachO::
761 getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
762                                MachineModuleInfo *MMI, unsigned Encoding,
763                                MCStreamer &Streamer) const {
764   // The mach-o version of this method defaults to returning a stub reference.
765 
766   if (Encoding & DW_EH_PE_indirect) {
767     MachineModuleInfoMachO &MachOMMI =
768       MMI->getObjFileInfo<MachineModuleInfoMachO>();
769 
770     SmallString<128> Name;
771     Mang->getNameWithPrefix(Name, GV, true);
772     Name += "$non_lazy_ptr";
773 
774     // Add information about the stub reference to MachOMMI so that the stub
775     // gets emitted by the asmprinter.
776     MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
777     MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
778     if (StubSym.getPointer() == 0) {
779       MCSymbol *Sym = Mang->getSymbol(GV);
780       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
781     }
782 
783     return TargetLoweringObjectFile::
784       getExprForDwarfReference(SSym, Mang, MMI,
785                                Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
786   }
787 
788   return TargetLoweringObjectFile::
789     getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, Streamer);
790 }
791 
792 unsigned TargetLoweringObjectFileMachO::getPersonalityEncoding() const {
793   return DW_EH_PE_indirect | DW_EH_PE_pcrel | DW_EH_PE_sdata4;
794 }
795 
796 unsigned TargetLoweringObjectFileMachO::getLSDAEncoding() const {
797   return DW_EH_PE_pcrel;
798 }
799 
800 unsigned TargetLoweringObjectFileMachO::getFDEEncoding() const {
801   return DW_EH_PE_pcrel;
802 }
803 
804 unsigned TargetLoweringObjectFileMachO::getTTypeEncoding() const {
805   return DW_EH_PE_indirect | DW_EH_PE_pcrel | DW_EH_PE_sdata4;
806 }
807 
808 //===----------------------------------------------------------------------===//
809 //                                  COFF
810 //===----------------------------------------------------------------------===//
811 
812 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
813                                               const TargetMachine &TM) {
814   TargetLoweringObjectFile::Initialize(Ctx, TM);
815   TextSection =
816     getContext().getCOFFSection(".text",
817                                 MCSectionCOFF::IMAGE_SCN_CNT_CODE |
818                                 MCSectionCOFF::IMAGE_SCN_MEM_EXECUTE |
819                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
820                                 SectionKind::getText());
821   DataSection =
822     getContext().getCOFFSection(".data",
823                                 MCSectionCOFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
824                                 MCSectionCOFF::IMAGE_SCN_MEM_READ |
825                                 MCSectionCOFF::IMAGE_SCN_MEM_WRITE,
826                                 SectionKind::getDataRel());
827   ReadOnlySection =
828     getContext().getCOFFSection(".rdata",
829                                 MCSectionCOFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
830                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
831                                 SectionKind::getReadOnly());
832   StaticCtorSection =
833     getContext().getCOFFSection(".ctors",
834                                 MCSectionCOFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
835                                 MCSectionCOFF::IMAGE_SCN_MEM_READ |
836                                 MCSectionCOFF::IMAGE_SCN_MEM_WRITE,
837                                 SectionKind::getDataRel());
838   StaticDtorSection =
839     getContext().getCOFFSection(".dtors",
840                                 MCSectionCOFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
841                                 MCSectionCOFF::IMAGE_SCN_MEM_READ |
842                                 MCSectionCOFF::IMAGE_SCN_MEM_WRITE,
843                                 SectionKind::getDataRel());
844 
845   // FIXME: We're emitting LSDA info into a readonly section on COFF, even
846   // though it contains relocatable pointers.  In PIC mode, this is probably a
847   // big runtime hit for C++ apps.  Either the contents of the LSDA need to be
848   // adjusted or this should be a data section.
849   LSDASection =
850     getContext().getCOFFSection(".gcc_except_table",
851                                 MCSectionCOFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
852                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
853                                 SectionKind::getReadOnly());
854   EHFrameSection =
855     getContext().getCOFFSection(".eh_frame",
856                                 MCSectionCOFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
857                                 MCSectionCOFF::IMAGE_SCN_MEM_READ |
858                                 MCSectionCOFF::IMAGE_SCN_MEM_WRITE,
859                                 SectionKind::getDataRel());
860 
861   // Debug info.
862   DwarfAbbrevSection =
863     getContext().getCOFFSection(".debug_abbrev",
864                                 MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE |
865                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
866                                 SectionKind::getMetadata());
867   DwarfInfoSection =
868     getContext().getCOFFSection(".debug_info",
869                                 MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE |
870                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
871                                 SectionKind::getMetadata());
872   DwarfLineSection =
873     getContext().getCOFFSection(".debug_line",
874                                 MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE |
875                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
876                                 SectionKind::getMetadata());
877   DwarfFrameSection =
878     getContext().getCOFFSection(".debug_frame",
879                                 MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE |
880                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
881                                 SectionKind::getMetadata());
882   DwarfPubNamesSection =
883     getContext().getCOFFSection(".debug_pubnames",
884                                 MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE |
885                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
886                                 SectionKind::getMetadata());
887   DwarfPubTypesSection =
888     getContext().getCOFFSection(".debug_pubtypes",
889                                 MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE |
890                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
891                                 SectionKind::getMetadata());
892   DwarfStrSection =
893     getContext().getCOFFSection(".debug_str",
894                                 MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE |
895                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
896                                 SectionKind::getMetadata());
897   DwarfLocSection =
898     getContext().getCOFFSection(".debug_loc",
899                                 MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE |
900                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
901                                 SectionKind::getMetadata());
902   DwarfARangesSection =
903     getContext().getCOFFSection(".debug_aranges",
904                                 MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE |
905                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
906                                 SectionKind::getMetadata());
907   DwarfRangesSection =
908     getContext().getCOFFSection(".debug_ranges",
909                                 MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE |
910                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
911                                 SectionKind::getMetadata());
912   DwarfMacroInfoSection =
913     getContext().getCOFFSection(".debug_macinfo",
914                                 MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE |
915                                 MCSectionCOFF::IMAGE_SCN_MEM_READ,
916                                 SectionKind::getMetadata());
917 
918   DrectveSection =
919     getContext().getCOFFSection(".drectve",
920                                 MCSectionCOFF::IMAGE_SCN_LNK_INFO,
921                                 SectionKind::getMetadata());
922 }
923 
924 static unsigned
925 getCOFFSectionFlags(SectionKind K) {
926   unsigned Flags = 0;
927 
928   if (!K.isMetadata())
929     Flags |=
930       MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE;
931   else if (K.isText())
932     Flags |=
933       MCSectionCOFF::IMAGE_SCN_MEM_EXECUTE |
934       MCSectionCOFF::IMAGE_SCN_CNT_CODE;
935   else if (K.isBSS ())
936     Flags |=
937       MCSectionCOFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
938       MCSectionCOFF::IMAGE_SCN_MEM_READ |
939       MCSectionCOFF::IMAGE_SCN_MEM_WRITE;
940   else if (K.isReadOnly())
941     Flags |=
942       MCSectionCOFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
943       MCSectionCOFF::IMAGE_SCN_MEM_READ;
944   else if (K.isWriteable())
945     Flags |=
946       MCSectionCOFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
947       MCSectionCOFF::IMAGE_SCN_MEM_READ |
948       MCSectionCOFF::IMAGE_SCN_MEM_WRITE;
949 
950   return Flags;
951 }
952 
953 const MCSection *TargetLoweringObjectFileCOFF::
954 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
955                          Mangler *Mang, const TargetMachine &TM) const {
956   return getContext().getCOFFSection(GV->getSection(),
957                                      getCOFFSectionFlags(Kind),
958                                      Kind);
959 }
960 
961 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
962   if (Kind.isText())
963     return ".text$linkonce";
964   if (Kind.isBSS ())
965     return ".bss$linkonce";
966   if (Kind.isWriteable())
967     return ".data$linkonce";
968   return ".rdata$linkonce";
969 }
970 
971 
972 const MCSection *TargetLoweringObjectFileCOFF::
973 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
974                        Mangler *Mang, const TargetMachine &TM) const {
975   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
976 
977   // If this global is linkonce/weak and the target handles this by emitting it
978   // into a 'uniqued' section name, create and return the section now.
979   if (GV->isWeakForLinker()) {
980     const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
981     SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
982     MCSymbol *Sym = Mang->getSymbol(GV);
983     Name.append(Sym->getName().begin(), Sym->getName().end());
984 
985     unsigned Characteristics = getCOFFSectionFlags(Kind);
986 
987     Characteristics |= MCSectionCOFF::IMAGE_SCN_LNK_COMDAT;
988 
989     return getContext().getCOFFSection(Name.str(), Characteristics,
990                           MCSectionCOFF::IMAGE_COMDAT_SELECT_EXACT_MATCH, Kind);
991   }
992 
993   if (Kind.isText())
994     return getTextSection();
995 
996   return getDataSection();
997 }
998 
999