TargetLoweringObjectFileImpl.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
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/ADT/SmallString.h"
17#include "llvm/ADT/StringExtras.h"
18#include "llvm/ADT/Triple.h"
19#include "llvm/CodeGen/MachineModuleInfoImpls.h"
20#include "llvm/IR/Constants.h"
21#include "llvm/IR/DataLayout.h"
22#include "llvm/IR/DerivedTypes.h"
23#include "llvm/IR/Function.h"
24#include "llvm/IR/GlobalVariable.h"
25#include "llvm/IR/Mangler.h"
26#include "llvm/IR/Module.h"
27#include "llvm/MC/MCContext.h"
28#include "llvm/MC/MCExpr.h"
29#include "llvm/MC/MCSectionCOFF.h"
30#include "llvm/MC/MCSectionELF.h"
31#include "llvm/MC/MCSectionMachO.h"
32#include "llvm/MC/MCStreamer.h"
33#include "llvm/MC/MCSymbol.h"
34#include "llvm/Support/Dwarf.h"
35#include "llvm/Support/ELF.h"
36#include "llvm/Support/ErrorHandling.h"
37#include "llvm/Support/raw_ostream.h"
38#include "llvm/Target/TargetLowering.h"
39#include "llvm/Target/TargetMachine.h"
40using namespace llvm;
41using namespace dwarf;
42
43//===----------------------------------------------------------------------===//
44//                                  ELF
45//===----------------------------------------------------------------------===//
46
47MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
48    const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
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 TM.getSymbol(GV, Mang);
56  case dwarf::DW_EH_PE_pcrel: {
57    return getContext().GetOrCreateSymbol(StringRef("DW.ref.") +
58                                          TM.getSymbol(GV, Mang)->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  unsigned Size = TM.getDataLayout()->getPointerSize();
80  Streamer.SwitchSection(Sec);
81  Streamer.EmitValueToAlignment(TM.getDataLayout()->getPointerABIAlignment());
82  Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
83  const MCExpr *E = MCConstantExpr::Create(Size, getContext());
84  Streamer.EmitELFSize(Label, E);
85  Streamer.EmitLabel(Label);
86
87  Streamer.EmitSymbolValue(Sym, Size);
88}
89
90const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
91    const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
92    const TargetMachine &TM, MachineModuleInfo *MMI,
93    MCStreamer &Streamer) const {
94
95  if (Encoding & dwarf::DW_EH_PE_indirect) {
96    MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
97
98    MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", Mang, TM);
99
100    // Add information about the stub reference to ELFMMI so that the stub
101    // gets emitted by the asmprinter.
102    MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
103    if (StubSym.getPointer() == 0) {
104      MCSymbol *Sym = TM.getSymbol(GV, Mang);
105      StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
106    }
107
108    return TargetLoweringObjectFile::
109      getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
110                        Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
111  }
112
113  return TargetLoweringObjectFile::
114    getTTypeGlobalReference(GV, Encoding, Mang, TM, MMI, Streamer);
115}
116
117static SectionKind
118getELFKindForNamedSection(StringRef Name, SectionKind K) {
119  // N.B.: The defaults used in here are no the same ones used in MC.
120  // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
121  // both gas and MC will produce a section with no flags. Given
122  // section(".eh_frame") gcc will produce:
123  //
124  //   .section   .eh_frame,"a",@progbits
125  if (Name.empty() || Name[0] != '.') return K;
126
127  // Some lame default implementation based on some magic section names.
128  if (Name == ".bss" ||
129      Name.startswith(".bss.") ||
130      Name.startswith(".gnu.linkonce.b.") ||
131      Name.startswith(".llvm.linkonce.b.") ||
132      Name == ".sbss" ||
133      Name.startswith(".sbss.") ||
134      Name.startswith(".gnu.linkonce.sb.") ||
135      Name.startswith(".llvm.linkonce.sb."))
136    return SectionKind::getBSS();
137
138  if (Name == ".tdata" ||
139      Name.startswith(".tdata.") ||
140      Name.startswith(".gnu.linkonce.td.") ||
141      Name.startswith(".llvm.linkonce.td."))
142    return SectionKind::getThreadData();
143
144  if (Name == ".tbss" ||
145      Name.startswith(".tbss.") ||
146      Name.startswith(".gnu.linkonce.tb.") ||
147      Name.startswith(".llvm.linkonce.tb."))
148    return SectionKind::getThreadBSS();
149
150  return K;
151}
152
153
154static unsigned getELFSectionType(StringRef Name, SectionKind K) {
155
156  if (Name == ".init_array")
157    return ELF::SHT_INIT_ARRAY;
158
159  if (Name == ".fini_array")
160    return ELF::SHT_FINI_ARRAY;
161
162  if (Name == ".preinit_array")
163    return ELF::SHT_PREINIT_ARRAY;
164
165  if (K.isBSS() || K.isThreadBSS())
166    return ELF::SHT_NOBITS;
167
168  return ELF::SHT_PROGBITS;
169}
170
171
172static unsigned
173getELFSectionFlags(SectionKind K) {
174  unsigned Flags = 0;
175
176  if (!K.isMetadata())
177    Flags |= ELF::SHF_ALLOC;
178
179  if (K.isText())
180    Flags |= ELF::SHF_EXECINSTR;
181
182  if (K.isWriteable())
183    Flags |= ELF::SHF_WRITE;
184
185  if (K.isThreadLocal())
186    Flags |= ELF::SHF_TLS;
187
188  // K.isMergeableConst() is left out to honour PR4650
189  if (K.isMergeableCString() || K.isMergeableConst4() ||
190      K.isMergeableConst8() || K.isMergeableConst16())
191    Flags |= ELF::SHF_MERGE;
192
193  if (K.isMergeableCString())
194    Flags |= ELF::SHF_STRINGS;
195
196  return Flags;
197}
198
199const MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
200    const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
201    const TargetMachine &TM) const {
202  StringRef SectionName = GV->getSection();
203
204  // Infer section flags from the section name if we can.
205  Kind = getELFKindForNamedSection(SectionName, Kind);
206
207  return getContext().getELFSection(SectionName,
208                                    getELFSectionType(SectionName, Kind),
209                                    getELFSectionFlags(Kind), Kind);
210}
211
212/// getSectionPrefixForGlobal - Return the section prefix name used by options
213/// FunctionsSections and DataSections.
214static const char *getSectionPrefixForGlobal(SectionKind Kind) {
215  if (Kind.isText())                 return ".text.";
216  if (Kind.isReadOnly())             return ".rodata.";
217  if (Kind.isBSS())                  return ".bss.";
218
219  if (Kind.isThreadData())           return ".tdata.";
220  if (Kind.isThreadBSS())            return ".tbss.";
221
222  if (Kind.isDataNoRel())            return ".data.";
223  if (Kind.isDataRelLocal())         return ".data.rel.local.";
224  if (Kind.isDataRel())              return ".data.rel.";
225  if (Kind.isReadOnlyWithRelLocal()) return ".data.rel.ro.local.";
226
227  assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
228  return ".data.rel.ro.";
229}
230
231
232const MCSection *TargetLoweringObjectFileELF::
233SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
234                       Mangler &Mang, const TargetMachine &TM) const {
235  // If we have -ffunction-section or -fdata-section then we should emit the
236  // global value to a uniqued section specifically for it.
237  bool EmitUniquedSection;
238  if (Kind.isText())
239    EmitUniquedSection = TM.getFunctionSections();
240  else
241    EmitUniquedSection = TM.getDataSections();
242
243  // If this global is linkonce/weak and the target handles this by emitting it
244  // into a 'uniqued' section name, create and return the section now.
245  if ((GV->isWeakForLinker() || EmitUniquedSection) &&
246      !Kind.isCommon()) {
247    const char *Prefix;
248    Prefix = getSectionPrefixForGlobal(Kind);
249
250    SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
251    TM.getNameWithPrefix(Name, GV, Mang, true);
252
253    StringRef Group = "";
254    unsigned Flags = getELFSectionFlags(Kind);
255    if (GV->isWeakForLinker()) {
256      Group = Name.substr(strlen(Prefix));
257      Flags |= ELF::SHF_GROUP;
258    }
259
260    return getContext().getELFSection(Name.str(),
261                                      getELFSectionType(Name.str(), Kind),
262                                      Flags, Kind, 0, Group);
263  }
264
265  if (Kind.isText()) return TextSection;
266
267  if (Kind.isMergeable1ByteCString() ||
268      Kind.isMergeable2ByteCString() ||
269      Kind.isMergeable4ByteCString()) {
270
271    // We also need alignment here.
272    // FIXME: this is getting the alignment of the character, not the
273    // alignment of the global!
274    unsigned Align =
275      TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV));
276
277    const char *SizeSpec = ".rodata.str1.";
278    if (Kind.isMergeable2ByteCString())
279      SizeSpec = ".rodata.str2.";
280    else if (Kind.isMergeable4ByteCString())
281      SizeSpec = ".rodata.str4.";
282    else
283      assert(Kind.isMergeable1ByteCString() && "unknown string width");
284
285
286    std::string Name = SizeSpec + utostr(Align);
287    return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
288                                      ELF::SHF_ALLOC |
289                                      ELF::SHF_MERGE |
290                                      ELF::SHF_STRINGS,
291                                      Kind);
292  }
293
294  if (Kind.isMergeableConst()) {
295    if (Kind.isMergeableConst4() && MergeableConst4Section)
296      return MergeableConst4Section;
297    if (Kind.isMergeableConst8() && MergeableConst8Section)
298      return MergeableConst8Section;
299    if (Kind.isMergeableConst16() && MergeableConst16Section)
300      return MergeableConst16Section;
301    return ReadOnlySection;  // .const
302  }
303
304  if (Kind.isReadOnly())             return ReadOnlySection;
305
306  if (Kind.isThreadData())           return TLSDataSection;
307  if (Kind.isThreadBSS())            return TLSBSSSection;
308
309  // Note: we claim that common symbols are put in BSSSection, but they are
310  // really emitted with the magic .comm directive, which creates a symbol table
311  // entry but not a section.
312  if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
313
314  if (Kind.isDataNoRel())            return DataSection;
315  if (Kind.isDataRelLocal())         return DataRelLocalSection;
316  if (Kind.isDataRel())              return DataRelSection;
317  if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
318
319  assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
320  return DataRelROSection;
321}
322
323/// getSectionForConstant - Given a mergeable constant with the
324/// specified size and relocation information, return a section that it
325/// should be placed in.
326const MCSection *TargetLoweringObjectFileELF::
327getSectionForConstant(SectionKind Kind) const {
328  if (Kind.isMergeableConst4() && MergeableConst4Section)
329    return MergeableConst4Section;
330  if (Kind.isMergeableConst8() && MergeableConst8Section)
331    return MergeableConst8Section;
332  if (Kind.isMergeableConst16() && MergeableConst16Section)
333    return MergeableConst16Section;
334  if (Kind.isReadOnly())
335    return ReadOnlySection;
336
337  if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
338  assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
339  return DataRelROSection;
340}
341
342const MCSection *
343TargetLoweringObjectFileELF::getStaticCtorSection(unsigned Priority) const {
344  // The default scheme is .ctor / .dtor, so we have to invert the priority
345  // numbering.
346  if (Priority == 65535)
347    return StaticCtorSection;
348
349  if (UseInitArray) {
350    std::string Name = std::string(".init_array.") + utostr(Priority);
351    return getContext().getELFSection(Name, ELF::SHT_INIT_ARRAY,
352                                      ELF::SHF_ALLOC | ELF::SHF_WRITE,
353                                      SectionKind::getDataRel());
354  } else {
355    std::string Name = std::string(".ctors.") + utostr(65535 - Priority);
356    return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
357                                      ELF::SHF_ALLOC |ELF::SHF_WRITE,
358                                      SectionKind::getDataRel());
359  }
360}
361
362const MCSection *
363TargetLoweringObjectFileELF::getStaticDtorSection(unsigned Priority) const {
364  // The default scheme is .ctor / .dtor, so we have to invert the priority
365  // numbering.
366  if (Priority == 65535)
367    return StaticDtorSection;
368
369  if (UseInitArray) {
370    std::string Name = std::string(".fini_array.") + utostr(Priority);
371    return getContext().getELFSection(Name, ELF::SHT_FINI_ARRAY,
372                                      ELF::SHF_ALLOC | ELF::SHF_WRITE,
373                                      SectionKind::getDataRel());
374  } else {
375    std::string Name = std::string(".dtors.") + utostr(65535 - Priority);
376    return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
377                                      ELF::SHF_ALLOC |ELF::SHF_WRITE,
378                                      SectionKind::getDataRel());
379  }
380}
381
382void
383TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
384  UseInitArray = UseInitArray_;
385  if (!UseInitArray)
386    return;
387
388  StaticCtorSection =
389    getContext().getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
390                               ELF::SHF_WRITE |
391                               ELF::SHF_ALLOC,
392                               SectionKind::getDataRel());
393  StaticDtorSection =
394    getContext().getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
395                               ELF::SHF_WRITE |
396                               ELF::SHF_ALLOC,
397                               SectionKind::getDataRel());
398}
399
400//===----------------------------------------------------------------------===//
401//                                 MachO
402//===----------------------------------------------------------------------===//
403
404/// getDepLibFromLinkerOpt - Extract the dependent library name from a linker
405/// option string. Returns StringRef() if the option does not specify a library.
406StringRef TargetLoweringObjectFileMachO::
407getDepLibFromLinkerOpt(StringRef LinkerOption) const {
408  const char *LibCmd = "-l";
409  if (LinkerOption.startswith(LibCmd))
410    return LinkerOption.substr(strlen(LibCmd));
411  return StringRef();
412}
413
414/// emitModuleFlags - Perform code emission for module flags.
415void TargetLoweringObjectFileMachO::
416emitModuleFlags(MCStreamer &Streamer,
417                ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
418                Mangler &Mang, const TargetMachine &TM) const {
419  unsigned VersionVal = 0;
420  unsigned ImageInfoFlags = 0;
421  MDNode *LinkerOptions = 0;
422  StringRef SectionVal;
423
424  for (ArrayRef<Module::ModuleFlagEntry>::iterator
425         i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
426    const Module::ModuleFlagEntry &MFE = *i;
427
428    // Ignore flags with 'Require' behavior.
429    if (MFE.Behavior == Module::Require)
430      continue;
431
432    StringRef Key = MFE.Key->getString();
433    Value *Val = MFE.Val;
434
435    if (Key == "Objective-C Image Info Version") {
436      VersionVal = cast<ConstantInt>(Val)->getZExtValue();
437    } else if (Key == "Objective-C Garbage Collection" ||
438               Key == "Objective-C GC Only" ||
439               Key == "Objective-C Is Simulated") {
440      ImageInfoFlags |= cast<ConstantInt>(Val)->getZExtValue();
441    } else if (Key == "Objective-C Image Info Section") {
442      SectionVal = cast<MDString>(Val)->getString();
443    } else if (Key == "Linker Options") {
444      LinkerOptions = cast<MDNode>(Val);
445    }
446  }
447
448  // Emit the linker options if present.
449  if (LinkerOptions) {
450    for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
451      MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
452      SmallVector<std::string, 4> StrOptions;
453
454      // Convert to strings.
455      for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
456        MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
457        StrOptions.push_back(MDOption->getString());
458      }
459
460      Streamer.EmitLinkerOptions(StrOptions);
461    }
462  }
463
464  // The section is mandatory. If we don't have it, then we don't have GC info.
465  if (SectionVal.empty()) return;
466
467  StringRef Segment, Section;
468  unsigned TAA = 0, StubSize = 0;
469  bool TAAParsed;
470  std::string ErrorCode =
471    MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
472                                          TAA, TAAParsed, StubSize);
473  if (!ErrorCode.empty())
474    // If invalid, report the error with report_fatal_error.
475    report_fatal_error("Invalid section specifier '" + Section + "': " +
476                       ErrorCode + ".");
477
478  // Get the section.
479  const MCSectionMachO *S =
480    getContext().getMachOSection(Segment, Section, TAA, StubSize,
481                                 SectionKind::getDataNoRel());
482  Streamer.SwitchSection(S);
483  Streamer.EmitLabel(getContext().
484                     GetOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
485  Streamer.EmitIntValue(VersionVal, 4);
486  Streamer.EmitIntValue(ImageInfoFlags, 4);
487  Streamer.AddBlankLine();
488}
489
490const MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
491    const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
492    const TargetMachine &TM) const {
493  // Parse the section specifier and create it if valid.
494  StringRef Segment, Section;
495  unsigned TAA = 0, StubSize = 0;
496  bool TAAParsed;
497  std::string ErrorCode =
498    MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
499                                          TAA, TAAParsed, StubSize);
500  if (!ErrorCode.empty()) {
501    // If invalid, report the error with report_fatal_error.
502    report_fatal_error("Global variable '" + GV->getName() +
503                       "' has an invalid section specifier '" +
504                       GV->getSection() + "': " + ErrorCode + ".");
505  }
506
507  // Get the section.
508  const MCSectionMachO *S =
509    getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
510
511  // If TAA wasn't set by ParseSectionSpecifier() above,
512  // use the value returned by getMachOSection() as a default.
513  if (!TAAParsed)
514    TAA = S->getTypeAndAttributes();
515
516  // Okay, now that we got the section, verify that the TAA & StubSize agree.
517  // If the user declared multiple globals with different section flags, we need
518  // to reject it here.
519  if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
520    // If invalid, report the error with report_fatal_error.
521    report_fatal_error("Global variable '" + GV->getName() +
522                       "' section type or attributes does not match previous"
523                       " section specifier");
524  }
525
526  return S;
527}
528
529bool TargetLoweringObjectFileMachO::isSectionAtomizableBySymbols(
530    const MCSection &Section) const {
531    const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
532
533    // Sections holding 1 byte strings are atomized based on the data
534    // they contain.
535    // Sections holding 2 byte strings require symbols in order to be
536    // atomized.
537    // There is no dedicated section for 4 byte strings.
538    if (SMO.getKind().isMergeable1ByteCString())
539      return false;
540
541    if (SMO.getSegmentName() == "__DATA" &&
542        SMO.getSectionName() == "__cfstring")
543      return false;
544
545    switch (SMO.getType()) {
546    default:
547      return true;
548
549      // These sections are atomized at the element boundaries without using
550      // symbols.
551    case MachO::S_4BYTE_LITERALS:
552    case MachO::S_8BYTE_LITERALS:
553    case MachO::S_16BYTE_LITERALS:
554    case MachO::S_LITERAL_POINTERS:
555    case MachO::S_NON_LAZY_SYMBOL_POINTERS:
556    case MachO::S_LAZY_SYMBOL_POINTERS:
557    case MachO::S_MOD_INIT_FUNC_POINTERS:
558    case MachO::S_MOD_TERM_FUNC_POINTERS:
559    case MachO::S_INTERPOSING:
560      return false;
561    }
562}
563
564const MCSection *TargetLoweringObjectFileMachO::
565SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
566                       Mangler &Mang, const TargetMachine &TM) const {
567
568  // Handle thread local data.
569  if (Kind.isThreadBSS()) return TLSBSSSection;
570  if (Kind.isThreadData()) return TLSDataSection;
571
572  if (Kind.isText())
573    return GV->isWeakForLinker() ? TextCoalSection : TextSection;
574
575  // If this is weak/linkonce, put this in a coalescable section, either in text
576  // or data depending on if it is writable.
577  if (GV->isWeakForLinker()) {
578    if (Kind.isReadOnly())
579      return ConstTextCoalSection;
580    return DataCoalSection;
581  }
582
583  // FIXME: Alignment check should be handled by section classifier.
584  if (Kind.isMergeable1ByteCString() &&
585      TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
586    return CStringSection;
587
588  // Do not put 16-bit arrays in the UString section if they have an
589  // externally visible label, this runs into issues with certain linker
590  // versions.
591  if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
592      TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
593    return UStringSection;
594
595  if (Kind.isMergeableConst()) {
596    if (Kind.isMergeableConst4())
597      return FourByteConstantSection;
598    if (Kind.isMergeableConst8())
599      return EightByteConstantSection;
600    if (Kind.isMergeableConst16())
601      return SixteenByteConstantSection;
602  }
603
604  // Otherwise, if it is readonly, but not something we can specially optimize,
605  // just drop it in .const.
606  if (Kind.isReadOnly())
607    return ReadOnlySection;
608
609  // If this is marked const, put it into a const section.  But if the dynamic
610  // linker needs to write to it, put it in the data segment.
611  if (Kind.isReadOnlyWithRel())
612    return ConstDataSection;
613
614  // Put zero initialized globals with strong external linkage in the
615  // DATA, __common section with the .zerofill directive.
616  if (Kind.isBSSExtern())
617    return DataCommonSection;
618
619  // Put zero initialized globals with local linkage in __DATA,__bss directive
620  // with the .zerofill directive (aka .lcomm).
621  if (Kind.isBSSLocal())
622    return DataBSSSection;
623
624  // Otherwise, just drop the variable in the normal data section.
625  return DataSection;
626}
627
628const MCSection *
629TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
630  // If this constant requires a relocation, we have to put it in the data
631  // segment, not in the text segment.
632  if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
633    return ConstDataSection;
634
635  if (Kind.isMergeableConst4())
636    return FourByteConstantSection;
637  if (Kind.isMergeableConst8())
638    return EightByteConstantSection;
639  if (Kind.isMergeableConst16())
640    return SixteenByteConstantSection;
641  return ReadOnlySection;  // .const
642}
643
644const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
645    const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
646    const TargetMachine &TM, MachineModuleInfo *MMI,
647    MCStreamer &Streamer) const {
648  // The mach-o version of this method defaults to returning a stub reference.
649
650  if (Encoding & DW_EH_PE_indirect) {
651    MachineModuleInfoMachO &MachOMMI =
652      MMI->getObjFileInfo<MachineModuleInfoMachO>();
653
654    MCSymbol *SSym =
655        getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
656
657    // Add information about the stub reference to MachOMMI so that the stub
658    // gets emitted by the asmprinter.
659    MachineModuleInfoImpl::StubValueTy &StubSym =
660      GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
661                                  MachOMMI.getGVStubEntry(SSym);
662    if (StubSym.getPointer() == 0) {
663      MCSymbol *Sym = TM.getSymbol(GV, Mang);
664      StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
665    }
666
667    return TargetLoweringObjectFile::
668      getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
669                        Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
670  }
671
672  return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
673                                                           TM, MMI, Streamer);
674}
675
676MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
677    const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
678    MachineModuleInfo *MMI) const {
679  // The mach-o version of this method defaults to returning a stub reference.
680  MachineModuleInfoMachO &MachOMMI =
681    MMI->getObjFileInfo<MachineModuleInfoMachO>();
682
683  MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
684
685  // Add information about the stub reference to MachOMMI so that the stub
686  // gets emitted by the asmprinter.
687  MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
688  if (StubSym.getPointer() == 0) {
689    MCSymbol *Sym = TM.getSymbol(GV, Mang);
690    StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
691  }
692
693  return SSym;
694}
695
696//===----------------------------------------------------------------------===//
697//                                  COFF
698//===----------------------------------------------------------------------===//
699
700static unsigned
701getCOFFSectionFlags(SectionKind K) {
702  unsigned Flags = 0;
703
704  if (K.isMetadata())
705    Flags |=
706      COFF::IMAGE_SCN_MEM_DISCARDABLE;
707  else if (K.isText())
708    Flags |=
709      COFF::IMAGE_SCN_MEM_EXECUTE |
710      COFF::IMAGE_SCN_MEM_READ |
711      COFF::IMAGE_SCN_CNT_CODE;
712  else if (K.isBSS ())
713    Flags |=
714      COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
715      COFF::IMAGE_SCN_MEM_READ |
716      COFF::IMAGE_SCN_MEM_WRITE;
717  else if (K.isThreadLocal())
718    Flags |=
719      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
720      COFF::IMAGE_SCN_MEM_READ |
721      COFF::IMAGE_SCN_MEM_WRITE;
722  else if (K.isReadOnly())
723    Flags |=
724      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
725      COFF::IMAGE_SCN_MEM_READ;
726  else if (K.isWriteable())
727    Flags |=
728      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
729      COFF::IMAGE_SCN_MEM_READ |
730      COFF::IMAGE_SCN_MEM_WRITE;
731
732  return Flags;
733}
734
735const MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
736    const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
737    const TargetMachine &TM) const {
738  int Selection = 0;
739  unsigned Characteristics = getCOFFSectionFlags(Kind);
740  StringRef Name = GV->getSection();
741  StringRef COMDATSymName = "";
742  if (GV->isWeakForLinker()) {
743    Selection = COFF::IMAGE_COMDAT_SELECT_ANY;
744    Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
745    MCSymbol *Sym = TM.getSymbol(GV, Mang);
746    COMDATSymName = Sym->getName();
747  }
748  return getContext().getCOFFSection(Name,
749                                     Characteristics,
750                                     Kind,
751                                     COMDATSymName,
752                                     Selection);
753}
754
755static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
756  if (Kind.isText())
757    return ".text";
758  if (Kind.isBSS ())
759    return ".bss";
760  if (Kind.isThreadLocal())
761    return ".tls$";
762  if (Kind.isWriteable())
763    return ".data";
764  return ".rdata";
765}
766
767
768const MCSection *TargetLoweringObjectFileCOFF::
769SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
770                       Mangler &Mang, const TargetMachine &TM) const {
771  // If we have -ffunction-sections then we should emit the global value to a
772  // uniqued section specifically for it.
773  bool EmitUniquedSection;
774  if (Kind.isText())
775    EmitUniquedSection = TM.getFunctionSections();
776  else
777    EmitUniquedSection = TM.getDataSections();
778
779  // If this global is linkonce/weak and the target handles this by emitting it
780  // into a 'uniqued' section name, create and return the section now.
781  // Section names depend on the name of the symbol which is not feasible if the
782  // symbol has private linkage.
783  if ((GV->isWeakForLinker() || EmitUniquedSection) &&
784      !GV->hasPrivateLinkage()) {
785    const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
786    unsigned Characteristics = getCOFFSectionFlags(Kind);
787
788    Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
789    MCSymbol *Sym = TM.getSymbol(GV, Mang);
790    return getContext().getCOFFSection(
791        Name, Characteristics, Kind, Sym->getName(),
792        GV->isWeakForLinker() ? COFF::IMAGE_COMDAT_SELECT_ANY
793                              : COFF::IMAGE_COMDAT_SELECT_NODUPLICATES);
794  }
795
796  if (Kind.isText())
797    return TextSection;
798
799  if (Kind.isThreadLocal())
800    return TLSDataSection;
801
802  if (Kind.isReadOnly())
803    return ReadOnlySection;
804
805  if (Kind.isBSS())
806    return BSSSection;
807
808  return DataSection;
809}
810
811StringRef TargetLoweringObjectFileCOFF::
812getDepLibFromLinkerOpt(StringRef LinkerOption) const {
813  const char *LibCmd = "/DEFAULTLIB:";
814  if (LinkerOption.startswith(LibCmd))
815    return LinkerOption.substr(strlen(LibCmd));
816  return StringRef();
817}
818
819void TargetLoweringObjectFileCOFF::
820emitModuleFlags(MCStreamer &Streamer,
821                ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
822                Mangler &Mang, const TargetMachine &TM) const {
823  MDNode *LinkerOptions = 0;
824
825  // Look for the "Linker Options" flag, since it's the only one we support.
826  for (ArrayRef<Module::ModuleFlagEntry>::iterator
827       i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
828    const Module::ModuleFlagEntry &MFE = *i;
829    StringRef Key = MFE.Key->getString();
830    Value *Val = MFE.Val;
831    if (Key == "Linker Options") {
832      LinkerOptions = cast<MDNode>(Val);
833      break;
834    }
835  }
836  if (!LinkerOptions)
837    return;
838
839  // Emit the linker options to the linker .drectve section.  According to the
840  // spec, this section is a space-separated string containing flags for linker.
841  const MCSection *Sec = getDrectveSection();
842  Streamer.SwitchSection(Sec);
843  for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
844    MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
845    for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
846      MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
847      StringRef Op = MDOption->getString();
848      // Lead with a space for consistency with our dllexport implementation.
849      std::string Escaped(" ");
850      if (Op.find(" ") != StringRef::npos) {
851        // The PE-COFF spec says args with spaces must be quoted.  It doesn't say
852        // how to escape quotes, but it probably uses this algorithm:
853        // http://msdn.microsoft.com/en-us/library/17w5ykft(v=vs.85).aspx
854        // FIXME: Reuse escaping code from Support/Windows/Program.inc
855        Escaped.push_back('\"');
856        Escaped.append(Op);
857        Escaped.push_back('\"');
858      } else {
859        Escaped.append(Op);
860      }
861      Streamer.EmitBytes(Escaped);
862    }
863  }
864}
865