TargetLoweringObjectFileImpl.cpp revision d4a19b6a72d19a6f90b676aac37118664b7b7a84 
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/MCStreamer.h"
27#include "llvm/MC/MCSymbol.h"
28#include "llvm/Target/Mangler.h"
29#include "llvm/Target/TargetData.h"
30#include "llvm/Target/TargetMachine.h"
31#include "llvm/Target/TargetOptions.h"
32#include "llvm/Support/Dwarf.h"
33#include "llvm/Support/ELF.h"
34#include "llvm/Support/ErrorHandling.h"
35#include "llvm/Support/raw_ostream.h"
36#include "llvm/ADT/SmallString.h"
37#include "llvm/ADT/StringExtras.h"
38#include "llvm/ADT/Triple.h"
39using namespace llvm;
40using namespace dwarf;
41
42//===----------------------------------------------------------------------===//
43//                                  ELF
44//===----------------------------------------------------------------------===//
45
46MCSymbol *
47TargetLoweringObjectFileELF::getCFIPersonalitySymbol(const GlobalValue *GV,
48                                                     Mangler *Mang,
49                                                MachineModuleInfo *MMI) const {
50  unsigned Encoding = getPersonalityEncoding();
51  switch (Encoding & 0x70) {
52  default:
53    report_fatal_error("We do not support this DWARF encoding yet!");
54  case dwarf::DW_EH_PE_absptr:
55    return  Mang->getSymbol(GV);
56  case dwarf::DW_EH_PE_pcrel: {
57    return getContext().GetOrCreateSymbol(StringRef("DW.ref.") +
58                                          Mang->getSymbol(GV)->getName());
59  }
60  }
61}
62
63void TargetLoweringObjectFileELF::emitPersonalityValue(MCStreamer &Streamer,
64                                                       const TargetMachine &TM,
65                                                       const MCSymbol *Sym) const {
66  SmallString<64> NameData("DW.ref.");
67  NameData += Sym->getName();
68  MCSymbol *Label = getContext().GetOrCreateSymbol(NameData);
69  Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
70  Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
71  StringRef Prefix = ".data.";
72  NameData.insert(NameData.begin(), Prefix.begin(), Prefix.end());
73  unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
74  const MCSection *Sec = getContext().getELFSection(NameData,
75                                                    ELF::SHT_PROGBITS,
76                                                    Flags,
77                                                    SectionKind::getDataRel(),
78                                                    0, Label->getName());
79  Streamer.SwitchSection(Sec);
80  Streamer.EmitValueToAlignment(8);
81  Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
82  const MCExpr *E = MCConstantExpr::Create(8, getContext());
83  Streamer.EmitELFSize(Label, E);
84  Streamer.EmitLabel(Label);
85
86  unsigned Size = TM.getTargetData()->getPointerSize();
87  Streamer.EmitSymbolValue(Sym, Size);
88}
89
90static SectionKind
91getELFKindForNamedSection(StringRef Name, SectionKind K) {
92  // N.B.: The defaults used in here are no the same ones used in MC.
93  // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
94  // both gas and MC will produce a section with no flags. Given
95  // section(".eh_frame") gcc will produce
96  // .section	.eh_frame,"a",@progbits
97  if (Name.empty() || Name[0] != '.') return K;
98
99  // Some lame default implementation based on some magic section names.
100  if (Name == ".bss" ||
101      Name.startswith(".bss.") ||
102      Name.startswith(".gnu.linkonce.b.") ||
103      Name.startswith(".llvm.linkonce.b.") ||
104      Name == ".sbss" ||
105      Name.startswith(".sbss.") ||
106      Name.startswith(".gnu.linkonce.sb.") ||
107      Name.startswith(".llvm.linkonce.sb."))
108    return SectionKind::getBSS();
109
110  if (Name == ".tdata" ||
111      Name.startswith(".tdata.") ||
112      Name.startswith(".gnu.linkonce.td.") ||
113      Name.startswith(".llvm.linkonce.td."))
114    return SectionKind::getThreadData();
115
116  if (Name == ".tbss" ||
117      Name.startswith(".tbss.") ||
118      Name.startswith(".gnu.linkonce.tb.") ||
119      Name.startswith(".llvm.linkonce.tb."))
120    return SectionKind::getThreadBSS();
121
122  return K;
123}
124
125
126static unsigned getELFSectionType(StringRef Name, SectionKind K) {
127
128  if (Name == ".init_array")
129    return ELF::SHT_INIT_ARRAY;
130
131  if (Name == ".fini_array")
132    return ELF::SHT_FINI_ARRAY;
133
134  if (Name == ".preinit_array")
135    return ELF::SHT_PREINIT_ARRAY;
136
137  if (K.isBSS() || K.isThreadBSS())
138    return ELF::SHT_NOBITS;
139
140  return ELF::SHT_PROGBITS;
141}
142
143
144static unsigned
145getELFSectionFlags(SectionKind K) {
146  unsigned Flags = 0;
147
148  if (!K.isMetadata())
149    Flags |= ELF::SHF_ALLOC;
150
151  if (K.isText())
152    Flags |= ELF::SHF_EXECINSTR;
153
154  if (K.isWriteable())
155    Flags |= ELF::SHF_WRITE;
156
157  if (K.isThreadLocal())
158    Flags |= ELF::SHF_TLS;
159
160  // K.isMergeableConst() is left out to honour PR4650
161  if (K.isMergeableCString() || K.isMergeableConst4() ||
162      K.isMergeableConst8() || K.isMergeableConst16())
163    Flags |= ELF::SHF_MERGE;
164
165  if (K.isMergeableCString())
166    Flags |= ELF::SHF_STRINGS;
167
168  return Flags;
169}
170
171
172const MCSection *TargetLoweringObjectFileELF::
173getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
174                         Mangler *Mang, const TargetMachine &TM) const {
175  StringRef SectionName = GV->getSection();
176
177  // Infer section flags from the section name if we can.
178  Kind = getELFKindForNamedSection(SectionName, Kind);
179
180  return getContext().getELFSection(SectionName,
181                                    getELFSectionType(SectionName, Kind),
182                                    getELFSectionFlags(Kind), Kind);
183}
184
185/// getSectionPrefixForGlobal - Return the section prefix name used by options
186/// FunctionsSections and DataSections.
187static const char *getSectionPrefixForGlobal(SectionKind Kind) {
188  if (Kind.isText())                 return ".text.";
189  if (Kind.isReadOnly())             return ".rodata.";
190
191  if (Kind.isThreadData())           return ".tdata.";
192  if (Kind.isThreadBSS())            return ".tbss.";
193
194  if (Kind.isDataNoRel())            return ".data.";
195  if (Kind.isDataRelLocal())         return ".data.rel.local.";
196  if (Kind.isDataRel())              return ".data.rel.";
197  if (Kind.isReadOnlyWithRelLocal()) return ".data.rel.ro.local.";
198
199  assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
200  return ".data.rel.ro.";
201}
202
203
204const MCSection *TargetLoweringObjectFileELF::
205SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
206                       Mangler *Mang, const TargetMachine &TM) const {
207  // If we have -ffunction-section or -fdata-section then we should emit the
208  // global value to a uniqued section specifically for it.
209  bool EmitUniquedSection;
210  if (Kind.isText())
211    EmitUniquedSection = TM.getFunctionSections();
212  else
213    EmitUniquedSection = TM.getDataSections();
214
215  // If this global is linkonce/weak and the target handles this by emitting it
216  // into a 'uniqued' section name, create and return the section now.
217  if ((GV->isWeakForLinker() || EmitUniquedSection) &&
218      !Kind.isCommon() && !Kind.isBSS()) {
219    const char *Prefix;
220    Prefix = getSectionPrefixForGlobal(Kind);
221
222    SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
223    MCSymbol *Sym = Mang->getSymbol(GV);
224    Name.append(Sym->getName().begin(), Sym->getName().end());
225    StringRef Group = "";
226    unsigned Flags = getELFSectionFlags(Kind);
227    if (GV->isWeakForLinker()) {
228      Group = Sym->getName();
229      Flags |= ELF::SHF_GROUP;
230    }
231
232    return getContext().getELFSection(Name.str(),
233                                      getELFSectionType(Name.str(), Kind),
234                                      Flags, Kind, 0, Group);
235  }
236
237  if (Kind.isText()) return TextSection;
238
239  if (Kind.isMergeable1ByteCString() ||
240      Kind.isMergeable2ByteCString() ||
241      Kind.isMergeable4ByteCString()) {
242
243    // We also need alignment here.
244    // FIXME: this is getting the alignment of the character, not the
245    // alignment of the global!
246    unsigned Align =
247      TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV));
248
249    const char *SizeSpec = ".rodata.str1.";
250    if (Kind.isMergeable2ByteCString())
251      SizeSpec = ".rodata.str2.";
252    else if (Kind.isMergeable4ByteCString())
253      SizeSpec = ".rodata.str4.";
254    else
255      assert(Kind.isMergeable1ByteCString() && "unknown string width");
256
257
258    std::string Name = SizeSpec + utostr(Align);
259    return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
260                                      ELF::SHF_ALLOC |
261                                      ELF::SHF_MERGE |
262                                      ELF::SHF_STRINGS,
263                                      Kind);
264  }
265
266  if (Kind.isMergeableConst()) {
267    if (Kind.isMergeableConst4() && MergeableConst4Section)
268      return MergeableConst4Section;
269    if (Kind.isMergeableConst8() && MergeableConst8Section)
270      return MergeableConst8Section;
271    if (Kind.isMergeableConst16() && MergeableConst16Section)
272      return MergeableConst16Section;
273    return ReadOnlySection;  // .const
274  }
275
276  if (Kind.isReadOnly())             return ReadOnlySection;
277
278  if (Kind.isThreadData())           return TLSDataSection;
279  if (Kind.isThreadBSS())            return TLSBSSSection;
280
281  // Note: we claim that common symbols are put in BSSSection, but they are
282  // really emitted with the magic .comm directive, which creates a symbol table
283  // entry but not a section.
284  if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
285
286  if (Kind.isDataNoRel())            return DataSection;
287  if (Kind.isDataRelLocal())         return DataRelLocalSection;
288  if (Kind.isDataRel())              return DataRelSection;
289  if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
290
291  assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
292  return DataRelROSection;
293}
294
295/// getSectionForConstant - Given a mergeable constant with the
296/// specified size and relocation information, return a section that it
297/// should be placed in.
298const MCSection *TargetLoweringObjectFileELF::
299getSectionForConstant(SectionKind Kind) const {
300  if (Kind.isMergeableConst4() && MergeableConst4Section)
301    return MergeableConst4Section;
302  if (Kind.isMergeableConst8() && MergeableConst8Section)
303    return MergeableConst8Section;
304  if (Kind.isMergeableConst16() && MergeableConst16Section)
305    return MergeableConst16Section;
306  if (Kind.isReadOnly())
307    return ReadOnlySection;
308
309  if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
310  assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
311  return DataRelROSection;
312}
313
314const MCExpr *TargetLoweringObjectFileELF::
315getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
316                               MachineModuleInfo *MMI,
317                               unsigned Encoding, MCStreamer &Streamer) const {
318
319  if (Encoding & dwarf::DW_EH_PE_indirect) {
320    MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
321
322    SmallString<128> Name;
323    Mang->getNameWithPrefix(Name, GV, true);
324    Name += ".DW.stub";
325
326    // Add information about the stub reference to ELFMMI so that the stub
327    // gets emitted by the asmprinter.
328    MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
329    MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
330    if (StubSym.getPointer() == 0) {
331      MCSymbol *Sym = Mang->getSymbol(GV);
332      StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
333    }
334
335    return TargetLoweringObjectFile::
336      getExprForDwarfReference(SSym, Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
337  }
338
339  return TargetLoweringObjectFile::
340    getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, Streamer);
341}
342
343const MCSection *
344TargetLoweringObjectFileELF::getStaticCtorSection(unsigned Priority) const {
345  // The default scheme is .ctor / .dtor, so we have to invert the priority
346  // numbering.
347  if (Priority == 65535)
348    return StaticCtorSection;
349
350  std::string Name = std::string(".ctors.") + utostr(65535 - Priority);
351  return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
352                                    ELF::SHF_ALLOC |ELF::SHF_WRITE,
353                                    SectionKind::getDataRel());
354}
355
356const MCSection *
357TargetLoweringObjectFileELF::getStaticDtorSection(unsigned Priority) const {
358  // The default scheme is .ctor / .dtor, so we have to invert the priority
359  // numbering.
360  if (Priority == 65535)
361    return StaticDtorSection;
362
363  std::string Name = std::string(".dtors.") + utostr(65535 - Priority);
364  return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
365                                    ELF::SHF_ALLOC |ELF::SHF_WRITE,
366                                    SectionKind::getDataRel());
367}
368
369//===----------------------------------------------------------------------===//
370//                                 MachO
371//===----------------------------------------------------------------------===//
372
373const MCSection *TargetLoweringObjectFileMachO::
374getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
375                         Mangler *Mang, const TargetMachine &TM) const {
376  // Parse the section specifier and create it if valid.
377  StringRef Segment, Section;
378  unsigned TAA = 0, StubSize = 0;
379  bool TAAParsed;
380  std::string ErrorCode =
381    MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
382                                          TAA, TAAParsed, StubSize);
383  if (!ErrorCode.empty()) {
384    // If invalid, report the error with report_fatal_error.
385    report_fatal_error("Global variable '" + GV->getName() +
386                       "' has an invalid section specifier '" +
387                       GV->getSection() + "': " + ErrorCode + ".");
388  }
389
390  // Get the section.
391  const MCSectionMachO *S =
392    getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
393
394  // If TAA wasn't set by ParseSectionSpecifier() above,
395  // use the value returned by getMachOSection() as a default.
396  if (!TAAParsed)
397    TAA = S->getTypeAndAttributes();
398
399  // Okay, now that we got the section, verify that the TAA & StubSize agree.
400  // If the user declared multiple globals with different section flags, we need
401  // to reject it here.
402  if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
403    // If invalid, report the error with report_fatal_error.
404    report_fatal_error("Global variable '" + GV->getName() +
405                       "' section type or attributes does not match previous"
406                       " section specifier");
407  }
408
409  return S;
410}
411
412const MCSection *TargetLoweringObjectFileMachO::
413SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
414                       Mangler *Mang, const TargetMachine &TM) const {
415
416  // Handle thread local data.
417  if (Kind.isThreadBSS()) return TLSBSSSection;
418  if (Kind.isThreadData()) return TLSDataSection;
419
420  if (Kind.isText())
421    return GV->isWeakForLinker() ? TextCoalSection : TextSection;
422
423  // If this is weak/linkonce, put this in a coalescable section, either in text
424  // or data depending on if it is writable.
425  if (GV->isWeakForLinker()) {
426    if (Kind.isReadOnly())
427      return ConstTextCoalSection;
428    return DataCoalSection;
429  }
430
431  // FIXME: Alignment check should be handled by section classifier.
432  if (Kind.isMergeable1ByteCString() &&
433      TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
434    return CStringSection;
435
436  // Do not put 16-bit arrays in the UString section if they have an
437  // externally visible label, this runs into issues with certain linker
438  // versions.
439  if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
440      TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
441    return UStringSection;
442
443  if (Kind.isMergeableConst()) {
444    if (Kind.isMergeableConst4())
445      return FourByteConstantSection;
446    if (Kind.isMergeableConst8())
447      return EightByteConstantSection;
448    if (Kind.isMergeableConst16() && SixteenByteConstantSection)
449      return SixteenByteConstantSection;
450  }
451
452  // Otherwise, if it is readonly, but not something we can specially optimize,
453  // just drop it in .const.
454  if (Kind.isReadOnly())
455    return ReadOnlySection;
456
457  // If this is marked const, put it into a const section.  But if the dynamic
458  // linker needs to write to it, put it in the data segment.
459  if (Kind.isReadOnlyWithRel())
460    return ConstDataSection;
461
462  // Put zero initialized globals with strong external linkage in the
463  // DATA, __common section with the .zerofill directive.
464  if (Kind.isBSSExtern())
465    return DataCommonSection;
466
467  // Put zero initialized globals with local linkage in __DATA,__bss directive
468  // with the .zerofill directive (aka .lcomm).
469  if (Kind.isBSSLocal())
470    return DataBSSSection;
471
472  // Otherwise, just drop the variable in the normal data section.
473  return DataSection;
474}
475
476const MCSection *
477TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
478  // If this constant requires a relocation, we have to put it in the data
479  // segment, not in the text segment.
480  if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
481    return ConstDataSection;
482
483  if (Kind.isMergeableConst4())
484    return FourByteConstantSection;
485  if (Kind.isMergeableConst8())
486    return EightByteConstantSection;
487  if (Kind.isMergeableConst16() && SixteenByteConstantSection)
488    return SixteenByteConstantSection;
489  return ReadOnlySection;  // .const
490}
491
492/// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
493/// not to emit the UsedDirective for some symbols in llvm.used.
494// FIXME: REMOVE this (rdar://7071300)
495bool TargetLoweringObjectFileMachO::
496shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
497  /// On Darwin, internally linked data beginning with "L" or "l" does not have
498  /// the directive emitted (this occurs in ObjC metadata).
499  if (!GV) return false;
500
501  // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
502  if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
503    // FIXME: ObjC metadata is currently emitted as internal symbols that have
504    // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
505    // this horrible hack can go away.
506    MCSymbol *Sym = Mang->getSymbol(GV);
507    if (Sym->getName()[0] == 'L' || Sym->getName()[0] == 'l')
508      return false;
509  }
510
511  return true;
512}
513
514const MCExpr *TargetLoweringObjectFileMachO::
515getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
516                               MachineModuleInfo *MMI, unsigned Encoding,
517                               MCStreamer &Streamer) const {
518  // The mach-o version of this method defaults to returning a stub reference.
519
520  if (Encoding & DW_EH_PE_indirect) {
521    MachineModuleInfoMachO &MachOMMI =
522      MMI->getObjFileInfo<MachineModuleInfoMachO>();
523
524    SmallString<128> Name;
525    Mang->getNameWithPrefix(Name, GV, true);
526    Name += "$non_lazy_ptr";
527
528    // Add information about the stub reference to MachOMMI so that the stub
529    // gets emitted by the asmprinter.
530    MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
531    MachineModuleInfoImpl::StubValueTy &StubSym =
532      GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
533                                  MachOMMI.getGVStubEntry(SSym);
534    if (StubSym.getPointer() == 0) {
535      MCSymbol *Sym = Mang->getSymbol(GV);
536      StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
537    }
538
539    return TargetLoweringObjectFile::
540      getExprForDwarfReference(SSym, Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
541  }
542
543  return TargetLoweringObjectFile::
544    getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, Streamer);
545}
546
547MCSymbol *TargetLoweringObjectFileMachO::
548getCFIPersonalitySymbol(const GlobalValue *GV, Mangler *Mang,
549                        MachineModuleInfo *MMI) const {
550  // The mach-o version of this method defaults to returning a stub reference.
551  MachineModuleInfoMachO &MachOMMI =
552    MMI->getObjFileInfo<MachineModuleInfoMachO>();
553
554  SmallString<128> Name;
555  Mang->getNameWithPrefix(Name, GV, true);
556  Name += "$non_lazy_ptr";
557
558  // Add information about the stub reference to MachOMMI so that the stub
559  // gets emitted by the asmprinter.
560  MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
561  MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
562  if (StubSym.getPointer() == 0) {
563    MCSymbol *Sym = Mang->getSymbol(GV);
564    StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
565  }
566
567  return SSym;
568}
569
570//===----------------------------------------------------------------------===//
571//                                  COFF
572//===----------------------------------------------------------------------===//
573
574static unsigned
575getCOFFSectionFlags(SectionKind K) {
576  unsigned Flags = 0;
577
578  if (K.isMetadata())
579    Flags |=
580      COFF::IMAGE_SCN_MEM_DISCARDABLE;
581  else if (K.isText())
582    Flags |=
583      COFF::IMAGE_SCN_MEM_EXECUTE |
584      COFF::IMAGE_SCN_MEM_READ |
585      COFF::IMAGE_SCN_CNT_CODE;
586  else if (K.isBSS ())
587    Flags |=
588      COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
589      COFF::IMAGE_SCN_MEM_READ |
590      COFF::IMAGE_SCN_MEM_WRITE;
591  else if (K.isThreadLocal())
592    Flags |=
593      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
594      COFF::IMAGE_SCN_MEM_READ |
595      COFF::IMAGE_SCN_MEM_WRITE;
596  else if (K.isReadOnly())
597    Flags |=
598      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
599      COFF::IMAGE_SCN_MEM_READ;
600  else if (K.isWriteable())
601    Flags |=
602      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
603      COFF::IMAGE_SCN_MEM_READ |
604      COFF::IMAGE_SCN_MEM_WRITE;
605
606  return Flags;
607}
608
609const MCSection *TargetLoweringObjectFileCOFF::
610getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
611                         Mangler *Mang, const TargetMachine &TM) const {
612  return getContext().getCOFFSection(GV->getSection(),
613                                     getCOFFSectionFlags(Kind),
614                                     Kind);
615}
616
617static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
618  if (Kind.isText())
619    return ".text$";
620  if (Kind.isBSS ())
621    return ".bss$";
622  if (Kind.isThreadLocal())
623    return ".tls$";
624  if (Kind.isWriteable())
625    return ".data$";
626  return ".rdata$";
627}
628
629
630const MCSection *TargetLoweringObjectFileCOFF::
631SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
632                       Mangler *Mang, const TargetMachine &TM) const {
633
634  // If this global is linkonce/weak and the target handles this by emitting it
635  // into a 'uniqued' section name, create and return the section now.
636  if (GV->isWeakForLinker()) {
637    const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
638    SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
639    MCSymbol *Sym = Mang->getSymbol(GV);
640    Name.append(Sym->getName().begin() + 1, Sym->getName().end());
641
642    unsigned Characteristics = getCOFFSectionFlags(Kind);
643
644    Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
645
646    return getContext().getCOFFSection(Name.str(), Characteristics,
647                          COFF::IMAGE_COMDAT_SELECT_ANY, Kind);
648  }
649
650  if (Kind.isText())
651    return getTextSection();
652
653  if (Kind.isThreadLocal())
654    return getTLSDataSection();
655
656  return getDataSection();
657}
658
659