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 
479   TLSThreadInitSection
480     = getContext().getMachOSection("__DATA", "__thread_init",
481                           MCSectionMachO::S_THREAD_LOCAL_INIT_FUNCTION_POINTERS,
482                           SectionKind::getDataRel());
483 
484   CStringSection // .cstring
485     = getContext().getMachOSection("__TEXT", "__cstring",
486                                    MCSectionMachO::S_CSTRING_LITERALS,
487                                    SectionKind::getMergeable1ByteCString());
488   UStringSection
489     = getContext().getMachOSection("__TEXT","__ustring", 0,
490                                    SectionKind::getMergeable2ByteCString());
491   FourByteConstantSection // .literal4
492     = getContext().getMachOSection("__TEXT", "__literal4",
493                                    MCSectionMachO::S_4BYTE_LITERALS,
494                                    SectionKind::getMergeableConst4());
495   EightByteConstantSection // .literal8
496     = getContext().getMachOSection("__TEXT", "__literal8",
497                                    MCSectionMachO::S_8BYTE_LITERALS,
498                                    SectionKind::getMergeableConst8());
499 
500   // ld_classic doesn't support .literal16 in 32-bit mode, and ld64 falls back
501   // to using it in -static mode.
502   SixteenByteConstantSection = 0;
503   if (TM.getRelocationModel() != Reloc::Static &&
504       TM.getTargetData()->getPointerSize() == 32)
505     SixteenByteConstantSection =   // .literal16
506       getContext().getMachOSection("__TEXT", "__literal16",
507                                    MCSectionMachO::S_16BYTE_LITERALS,
508                                    SectionKind::getMergeableConst16());
509 
510   ReadOnlySection  // .const
511     = getContext().getMachOSection("__TEXT", "__const", 0,
512                                    SectionKind::getReadOnly());
513 
514   TextCoalSection
515     = getContext().getMachOSection("__TEXT", "__textcoal_nt",
516                                    MCSectionMachO::S_COALESCED |
517                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
518                                    SectionKind::getText());
519   ConstTextCoalSection
520     = getContext().getMachOSection("__TEXT", "__const_coal",
521                                    MCSectionMachO::S_COALESCED,
522                                    SectionKind::getReadOnly());
523   ConstDataSection  // .const_data
524     = getContext().getMachOSection("__DATA", "__const", 0,
525                                    SectionKind::getReadOnlyWithRel());
526   DataCoalSection
527     = getContext().getMachOSection("__DATA","__datacoal_nt",
528                                    MCSectionMachO::S_COALESCED,
529                                    SectionKind::getDataRel());
530   DataCommonSection
531     = getContext().getMachOSection("__DATA","__common",
532                                    MCSectionMachO::S_ZEROFILL,
533                                    SectionKind::getBSS());
534   DataBSSSection
535     = getContext().getMachOSection("__DATA","__bss", MCSectionMachO::S_ZEROFILL,
536                                    SectionKind::getBSS());
537 
538 
539   LazySymbolPointerSection
540     = getContext().getMachOSection("__DATA", "__la_symbol_ptr",
541                                    MCSectionMachO::S_LAZY_SYMBOL_POINTERS,
542                                    SectionKind::getMetadata());
543   NonLazySymbolPointerSection
544     = getContext().getMachOSection("__DATA", "__nl_symbol_ptr",
545                                    MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS,
546                                    SectionKind::getMetadata());
547 
548   if (TM.getRelocationModel() == Reloc::Static) {
549     StaticCtorSection
550       = getContext().getMachOSection("__TEXT", "__constructor", 0,
551                                      SectionKind::getDataRel());
552     StaticDtorSection
553       = getContext().getMachOSection("__TEXT", "__destructor", 0,
554                                      SectionKind::getDataRel());
555   } else {
556     StaticCtorSection
557       = getContext().getMachOSection("__DATA", "__mod_init_func",
558                                      MCSectionMachO::S_MOD_INIT_FUNC_POINTERS,
559                                      SectionKind::getDataRel());
560     StaticDtorSection
561       = getContext().getMachOSection("__DATA", "__mod_term_func",
562                                      MCSectionMachO::S_MOD_TERM_FUNC_POINTERS,
563                                      SectionKind::getDataRel());
564   }
565 
566   // Exception Handling.
567   LSDASection = getContext().getMachOSection("__TEXT", "__gcc_except_tab", 0,
568                                              SectionKind::getReadOnlyWithRel());
569   EHFrameSection =
570     getContext().getMachOSection("__TEXT", "__eh_frame",
571                                  MCSectionMachO::S_COALESCED |
572                                  MCSectionMachO::S_ATTR_NO_TOC |
573                                  MCSectionMachO::S_ATTR_STRIP_STATIC_SYMS |
574                                  MCSectionMachO::S_ATTR_LIVE_SUPPORT,
575                                  SectionKind::getReadOnly());
576 
577   // Debug Information.
578   DwarfAbbrevSection =
579     getContext().getMachOSection("__DWARF", "__debug_abbrev",
580                                  MCSectionMachO::S_ATTR_DEBUG,
581                                  SectionKind::getMetadata());
582   DwarfInfoSection =
583     getContext().getMachOSection("__DWARF", "__debug_info",
584                                  MCSectionMachO::S_ATTR_DEBUG,
585                                  SectionKind::getMetadata());
586   DwarfLineSection =
587     getContext().getMachOSection("__DWARF", "__debug_line",
588                                  MCSectionMachO::S_ATTR_DEBUG,
589                                  SectionKind::getMetadata());
590   DwarfFrameSection =
591     getContext().getMachOSection("__DWARF", "__debug_frame",
592                                  MCSectionMachO::S_ATTR_DEBUG,
593                                  SectionKind::getMetadata());
594   DwarfPubNamesSection =
595     getContext().getMachOSection("__DWARF", "__debug_pubnames",
596                                  MCSectionMachO::S_ATTR_DEBUG,
597                                  SectionKind::getMetadata());
598   DwarfPubTypesSection =
599     getContext().getMachOSection("__DWARF", "__debug_pubtypes",
600                                  MCSectionMachO::S_ATTR_DEBUG,
601                                  SectionKind::getMetadata());
602   DwarfStrSection =
603     getContext().getMachOSection("__DWARF", "__debug_str",
604                                  MCSectionMachO::S_ATTR_DEBUG,
605                                  SectionKind::getMetadata());
606   DwarfLocSection =
607     getContext().getMachOSection("__DWARF", "__debug_loc",
608                                  MCSectionMachO::S_ATTR_DEBUG,
609                                  SectionKind::getMetadata());
610   DwarfARangesSection =
611     getContext().getMachOSection("__DWARF", "__debug_aranges",
612                                  MCSectionMachO::S_ATTR_DEBUG,
613                                  SectionKind::getMetadata());
614   DwarfRangesSection =
615     getContext().getMachOSection("__DWARF", "__debug_ranges",
616                                  MCSectionMachO::S_ATTR_DEBUG,
617                                  SectionKind::getMetadata());
618   DwarfMacroInfoSection =
619     getContext().getMachOSection("__DWARF", "__debug_macinfo",
620                                  MCSectionMachO::S_ATTR_DEBUG,
621                                  SectionKind::getMetadata());
622   DwarfDebugInlineSection =
623     getContext().getMachOSection("__DWARF", "__debug_inlined",
624                                  MCSectionMachO::S_ATTR_DEBUG,
625                                  SectionKind::getMetadata());
626 
627   TLSExtraDataSection = TLSTLVSection;
628 }
629 
630 const MCSection *TargetLoweringObjectFileMachO::
631 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
632                          Mangler *Mang, const TargetMachine &TM) const {
633   // Parse the section specifier and create it if valid.
634   StringRef Segment, Section;
635   unsigned TAA, StubSize;
636   std::string ErrorCode =
637     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
638                                           TAA, StubSize);
639   if (!ErrorCode.empty()) {
640     // If invalid, report the error with report_fatal_error.
641     report_fatal_error("Global variable '" + GV->getNameStr() +
642                       "' has an invalid section specifier '" + GV->getSection()+
643                       "': " + ErrorCode + ".");
644     // Fall back to dropping it into the data section.
645     return DataSection;
646   }
647 
648   // Get the section.
649   const MCSectionMachO *S =
650     getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
651 
652   // Okay, now that we got the section, verify that the TAA & StubSize agree.
653   // If the user declared multiple globals with different section flags, we need
654   // to reject it here.
655   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
656     // If invalid, report the error with report_fatal_error.
657     report_fatal_error("Global variable '" + GV->getNameStr() +
658                       "' section type or attributes does not match previous"
659                       " section specifier");
660   }
661 
662   return S;
663 }
664 
665 const MCSection *TargetLoweringObjectFileMachO::
666 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
667                        Mangler *Mang, const TargetMachine &TM) const {
668 
669   // Handle thread local data.
670   if (Kind.isThreadBSS()) return TLSBSSSection;
671   if (Kind.isThreadData()) return TLSDataSection;
672 
673   if (Kind.isText())
674     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
675 
676   // If this is weak/linkonce, put this in a coalescable section, either in text
677   // or data depending on if it is writable.
678   if (GV->isWeakForLinker()) {
679     if (Kind.isReadOnly())
680       return ConstTextCoalSection;
681     return DataCoalSection;
682   }
683 
684   // FIXME: Alignment check should be handled by section classifier.
685   if (Kind.isMergeable1ByteCString() &&
686       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
687     return CStringSection;
688 
689   // Do not put 16-bit arrays in the UString section if they have an
690   // externally visible label, this runs into issues with certain linker
691   // versions.
692   if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
693       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
694     return UStringSection;
695 
696   if (Kind.isMergeableConst()) {
697     if (Kind.isMergeableConst4())
698       return FourByteConstantSection;
699     if (Kind.isMergeableConst8())
700       return EightByteConstantSection;
701     if (Kind.isMergeableConst16() && SixteenByteConstantSection)
702       return SixteenByteConstantSection;
703   }
704 
705   // Otherwise, if it is readonly, but not something we can specially optimize,
706   // just drop it in .const.
707   if (Kind.isReadOnly())
708     return ReadOnlySection;
709 
710   // If this is marked const, put it into a const section.  But if the dynamic
711   // linker needs to write to it, put it in the data segment.
712   if (Kind.isReadOnlyWithRel())
713     return ConstDataSection;
714 
715   // Put zero initialized globals with strong external linkage in the
716   // DATA, __common section with the .zerofill directive.
717   if (Kind.isBSSExtern())
718     return DataCommonSection;
719 
720   // Put zero initialized globals with local linkage in __DATA,__bss directive
721   // with the .zerofill directive (aka .lcomm).
722   if (Kind.isBSSLocal())
723     return DataBSSSection;
724 
725   // Otherwise, just drop the variable in the normal data section.
726   return DataSection;
727 }
728 
729 const MCSection *
730 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
731   // If this constant requires a relocation, we have to put it in the data
732   // segment, not in the text segment.
733   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
734     return ConstDataSection;
735 
736   if (Kind.isMergeableConst4())
737     return FourByteConstantSection;
738   if (Kind.isMergeableConst8())
739     return EightByteConstantSection;
740   if (Kind.isMergeableConst16() && SixteenByteConstantSection)
741     return SixteenByteConstantSection;
742   return ReadOnlySection;  // .const
743 }
744 
745 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
746 /// not to emit the UsedDirective for some symbols in llvm.used.
747 // FIXME: REMOVE this (rdar://7071300)
748 bool TargetLoweringObjectFileMachO::
749 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
750   /// On Darwin, internally linked data beginning with "L" or "l" does not have
751   /// the directive emitted (this occurs in ObjC metadata).
752   if (!GV) return false;
753 
754   // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
755   if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
756     // FIXME: ObjC metadata is currently emitted as internal symbols that have
757     // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
758     // this horrible hack can go away.
759     MCSymbol *Sym = Mang->getSymbol(GV);
760     if (Sym->getName()[0] == 'L' || Sym->getName()[0] == 'l')
761       return false;
762   }
763 
764   return true;
765 }
766 
767 const MCExpr *TargetLoweringObjectFileMachO::
768 getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
769                                MachineModuleInfo *MMI, unsigned Encoding,
770                                MCStreamer &Streamer) const {
771   // The mach-o version of this method defaults to returning a stub reference.
772 
773   if (Encoding & DW_EH_PE_indirect) {
774     MachineModuleInfoMachO &MachOMMI =
775       MMI->getObjFileInfo<MachineModuleInfoMachO>();
776 
777     SmallString<128> Name;
778     Mang->getNameWithPrefix(Name, GV, true);
779     Name += "$non_lazy_ptr";
780 
781     // Add information about the stub reference to MachOMMI so that the stub
782     // gets emitted by the asmprinter.
783     MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
784     MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
785     if (StubSym.getPointer() == 0) {
786       MCSymbol *Sym = Mang->getSymbol(GV);
787       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
788     }
789 
790     return TargetLoweringObjectFile::
791       getExprForDwarfReference(SSym, Mang, MMI,
792                                Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
793   }
794 
795   return TargetLoweringObjectFile::
796     getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, Streamer);
797 }
798 
799 unsigned TargetLoweringObjectFileMachO::getPersonalityEncoding() const {
800   return DW_EH_PE_indirect | DW_EH_PE_pcrel | DW_EH_PE_sdata4;
801 }
802 
803 unsigned TargetLoweringObjectFileMachO::getLSDAEncoding() const {
804   return DW_EH_PE_pcrel;
805 }
806 
807 unsigned TargetLoweringObjectFileMachO::getFDEEncoding() const {
808   return DW_EH_PE_pcrel;
809 }
810 
811 unsigned TargetLoweringObjectFileMachO::getTTypeEncoding() const {
812   return DW_EH_PE_indirect | DW_EH_PE_pcrel | DW_EH_PE_sdata4;
813 }
814 
815 //===----------------------------------------------------------------------===//
816 //                                  COFF
817 //===----------------------------------------------------------------------===//
818 
819 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
820                                               const TargetMachine &TM) {
821   TargetLoweringObjectFile::Initialize(Ctx, TM);
822   TextSection =
823     getContext().getCOFFSection(".text",
824                                 COFF::IMAGE_SCN_CNT_CODE |
825                                 COFF::IMAGE_SCN_MEM_EXECUTE |
826                                 COFF::IMAGE_SCN_MEM_READ,
827                                 SectionKind::getText());
828   DataSection =
829     getContext().getCOFFSection(".data",
830                                 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
831                                 COFF::IMAGE_SCN_MEM_READ |
832                                 COFF::IMAGE_SCN_MEM_WRITE,
833                                 SectionKind::getDataRel());
834   ReadOnlySection =
835     getContext().getCOFFSection(".rdata",
836                                 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
837                                 COFF::IMAGE_SCN_MEM_READ,
838                                 SectionKind::getReadOnly());
839   StaticCtorSection =
840     getContext().getCOFFSection(".ctors",
841                                 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
842                                 COFF::IMAGE_SCN_MEM_READ |
843                                 COFF::IMAGE_SCN_MEM_WRITE,
844                                 SectionKind::getDataRel());
845   StaticDtorSection =
846     getContext().getCOFFSection(".dtors",
847                                 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
848                                 COFF::IMAGE_SCN_MEM_READ |
849                                 COFF::IMAGE_SCN_MEM_WRITE,
850                                 SectionKind::getDataRel());
851 
852   // FIXME: We're emitting LSDA info into a readonly section on COFF, even
853   // though it contains relocatable pointers.  In PIC mode, this is probably a
854   // big runtime hit for C++ apps.  Either the contents of the LSDA need to be
855   // adjusted or this should be a data section.
856   LSDASection =
857     getContext().getCOFFSection(".gcc_except_table",
858                                 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
859                                 COFF::IMAGE_SCN_MEM_READ,
860                                 SectionKind::getReadOnly());
861   EHFrameSection =
862     getContext().getCOFFSection(".eh_frame",
863                                 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
864                                 COFF::IMAGE_SCN_MEM_READ |
865                                 COFF::IMAGE_SCN_MEM_WRITE,
866                                 SectionKind::getDataRel());
867 
868   // Debug info.
869   DwarfAbbrevSection =
870     getContext().getCOFFSection(".debug_abbrev",
871                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
872                                 COFF::IMAGE_SCN_MEM_READ,
873                                 SectionKind::getMetadata());
874   DwarfInfoSection =
875     getContext().getCOFFSection(".debug_info",
876                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
877                                 COFF::IMAGE_SCN_MEM_READ,
878                                 SectionKind::getMetadata());
879   DwarfLineSection =
880     getContext().getCOFFSection(".debug_line",
881                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
882                                 COFF::IMAGE_SCN_MEM_READ,
883                                 SectionKind::getMetadata());
884   DwarfFrameSection =
885     getContext().getCOFFSection(".debug_frame",
886                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
887                                 COFF::IMAGE_SCN_MEM_READ,
888                                 SectionKind::getMetadata());
889   DwarfPubNamesSection =
890     getContext().getCOFFSection(".debug_pubnames",
891                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
892                                 COFF::IMAGE_SCN_MEM_READ,
893                                 SectionKind::getMetadata());
894   DwarfPubTypesSection =
895     getContext().getCOFFSection(".debug_pubtypes",
896                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
897                                 COFF::IMAGE_SCN_MEM_READ,
898                                 SectionKind::getMetadata());
899   DwarfStrSection =
900     getContext().getCOFFSection(".debug_str",
901                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
902                                 COFF::IMAGE_SCN_MEM_READ,
903                                 SectionKind::getMetadata());
904   DwarfLocSection =
905     getContext().getCOFFSection(".debug_loc",
906                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
907                                 COFF::IMAGE_SCN_MEM_READ,
908                                 SectionKind::getMetadata());
909   DwarfARangesSection =
910     getContext().getCOFFSection(".debug_aranges",
911                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
912                                 COFF::IMAGE_SCN_MEM_READ,
913                                 SectionKind::getMetadata());
914   DwarfRangesSection =
915     getContext().getCOFFSection(".debug_ranges",
916                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
917                                 COFF::IMAGE_SCN_MEM_READ,
918                                 SectionKind::getMetadata());
919   DwarfMacroInfoSection =
920     getContext().getCOFFSection(".debug_macinfo",
921                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
922                                 COFF::IMAGE_SCN_MEM_READ,
923                                 SectionKind::getMetadata());
924 
925   DrectveSection =
926     getContext().getCOFFSection(".drectve",
927                                 COFF::IMAGE_SCN_LNK_INFO,
928                                 SectionKind::getMetadata());
929 }
930 
931 static unsigned
932 getCOFFSectionFlags(SectionKind K) {
933   unsigned Flags = 0;
934 
935   if (K.isMetadata())
936     Flags |=
937       COFF::IMAGE_SCN_MEM_DISCARDABLE;
938   else if (K.isText())
939     Flags |=
940       COFF::IMAGE_SCN_MEM_EXECUTE |
941       COFF::IMAGE_SCN_CNT_CODE;
942   else if (K.isBSS ())
943     Flags |=
944       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
945       COFF::IMAGE_SCN_MEM_READ |
946       COFF::IMAGE_SCN_MEM_WRITE;
947   else if (K.isReadOnly())
948     Flags |=
949       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
950       COFF::IMAGE_SCN_MEM_READ;
951   else if (K.isWriteable())
952     Flags |=
953       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
954       COFF::IMAGE_SCN_MEM_READ |
955       COFF::IMAGE_SCN_MEM_WRITE;
956 
957   return Flags;
958 }
959 
960 const MCSection *TargetLoweringObjectFileCOFF::
961 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
962                          Mangler *Mang, const TargetMachine &TM) const {
963   return getContext().getCOFFSection(GV->getSection(),
964                                      getCOFFSectionFlags(Kind),
965                                      Kind);
966 }
967 
968 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
969   if (Kind.isText())
970     return ".text$linkonce";
971   if (Kind.isBSS ())
972     return ".bss$linkonce";
973   if (Kind.isWriteable())
974     return ".data$linkonce";
975   return ".rdata$linkonce";
976 }
977 
978 
979 const MCSection *TargetLoweringObjectFileCOFF::
980 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
981                        Mangler *Mang, const TargetMachine &TM) const {
982   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
983 
984   // If this global is linkonce/weak and the target handles this by emitting it
985   // into a 'uniqued' section name, create and return the section now.
986   if (GV->isWeakForLinker()) {
987     const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
988     SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
989     MCSymbol *Sym = Mang->getSymbol(GV);
990     Name.append(Sym->getName().begin(), Sym->getName().end());
991 
992     unsigned Characteristics = getCOFFSectionFlags(Kind);
993 
994     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
995 
996     return getContext().getCOFFSection(Name.str(), Characteristics,
997                           COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH, Kind);
998   }
999 
1000   if (Kind.isText())
1001     return getTextSection();
1002 
1003   return getDataSection();
1004 }
1005 
1006