TargetLoweringObjectFileImpl.cpp revision 288943 
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/MCSymbolELF.h"
34#include "llvm/MC/MCValue.h"
35#include "llvm/Support/Dwarf.h"
36#include "llvm/Support/ELF.h"
37#include "llvm/Support/ErrorHandling.h"
38#include "llvm/Support/raw_ostream.h"
39#include "llvm/Target/TargetLowering.h"
40#include "llvm/Target/TargetMachine.h"
41#include "llvm/Target/TargetSubtargetInfo.h"
42using namespace llvm;
43using namespace dwarf;
44
45//===----------------------------------------------------------------------===//
46//                                  ELF
47//===----------------------------------------------------------------------===//
48
49MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
50    const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
51    MachineModuleInfo *MMI) const {
52  unsigned Encoding = getPersonalityEncoding();
53  if ((Encoding & 0x80) == dwarf::DW_EH_PE_indirect)
54    return getContext().getOrCreateSymbol(StringRef("DW.ref.") +
55                                          TM.getSymbol(GV, Mang)->getName());
56  if ((Encoding & 0x70) == dwarf::DW_EH_PE_absptr)
57    return TM.getSymbol(GV, Mang);
58  report_fatal_error("We do not support this DWARF encoding yet!");
59}
60
61void TargetLoweringObjectFileELF::emitPersonalityValue(MCStreamer &Streamer,
62                                                       const TargetMachine &TM,
63                                                       const MCSymbol *Sym) const {
64  SmallString<64> NameData("DW.ref.");
65  NameData += Sym->getName();
66  MCSymbolELF *Label =
67      cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
68  Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
69  Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
70  StringRef Prefix = ".data.";
71  NameData.insert(NameData.begin(), Prefix.begin(), Prefix.end());
72  unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
73  MCSection *Sec = getContext().getELFSection(NameData, ELF::SHT_PROGBITS,
74                                              Flags, 0, Label->getName());
75  unsigned Size = TM.getDataLayout()->getPointerSize();
76  Streamer.SwitchSection(Sec);
77  Streamer.EmitValueToAlignment(TM.getDataLayout()->getPointerABIAlignment());
78  Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
79  const MCExpr *E = MCConstantExpr::create(Size, getContext());
80  Streamer.emitELFSize(Label, E);
81  Streamer.EmitLabel(Label);
82
83  Streamer.EmitSymbolValue(Sym, Size);
84}
85
86const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
87    const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
88    const TargetMachine &TM, MachineModuleInfo *MMI,
89    MCStreamer &Streamer) const {
90
91  if (Encoding & dwarf::DW_EH_PE_indirect) {
92    MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
93
94    MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", Mang, TM);
95
96    // Add information about the stub reference to ELFMMI so that the stub
97    // gets emitted by the asmprinter.
98    MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
99    if (!StubSym.getPointer()) {
100      MCSymbol *Sym = TM.getSymbol(GV, Mang);
101      StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
102    }
103
104    return TargetLoweringObjectFile::
105      getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
106                        Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
107  }
108
109  return TargetLoweringObjectFile::
110    getTTypeGlobalReference(GV, Encoding, Mang, TM, MMI, Streamer);
111}
112
113static SectionKind
114getELFKindForNamedSection(StringRef Name, SectionKind K) {
115  // N.B.: The defaults used in here are no the same ones used in MC.
116  // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
117  // both gas and MC will produce a section with no flags. Given
118  // section(".eh_frame") gcc will produce:
119  //
120  //   .section   .eh_frame,"a",@progbits
121  if (Name.empty() || Name[0] != '.') return K;
122
123  // Some lame default implementation based on some magic section names.
124  if (Name == ".bss" ||
125      Name.startswith(".bss.") ||
126      Name.startswith(".gnu.linkonce.b.") ||
127      Name.startswith(".llvm.linkonce.b.") ||
128      Name == ".sbss" ||
129      Name.startswith(".sbss.") ||
130      Name.startswith(".gnu.linkonce.sb.") ||
131      Name.startswith(".llvm.linkonce.sb."))
132    return SectionKind::getBSS();
133
134  if (Name == ".tdata" ||
135      Name.startswith(".tdata.") ||
136      Name.startswith(".gnu.linkonce.td.") ||
137      Name.startswith(".llvm.linkonce.td."))
138    return SectionKind::getThreadData();
139
140  if (Name == ".tbss" ||
141      Name.startswith(".tbss.") ||
142      Name.startswith(".gnu.linkonce.tb.") ||
143      Name.startswith(".llvm.linkonce.tb."))
144    return SectionKind::getThreadBSS();
145
146  return K;
147}
148
149
150static unsigned getELFSectionType(StringRef Name, SectionKind K) {
151
152  if (Name == ".init_array")
153    return ELF::SHT_INIT_ARRAY;
154
155  if (Name == ".fini_array")
156    return ELF::SHT_FINI_ARRAY;
157
158  if (Name == ".preinit_array")
159    return ELF::SHT_PREINIT_ARRAY;
160
161  if (K.isBSS() || K.isThreadBSS())
162    return ELF::SHT_NOBITS;
163
164  return ELF::SHT_PROGBITS;
165}
166
167static unsigned getELFSectionFlags(SectionKind K) {
168  unsigned Flags = 0;
169
170  if (!K.isMetadata())
171    Flags |= ELF::SHF_ALLOC;
172
173  if (K.isText())
174    Flags |= ELF::SHF_EXECINSTR;
175
176  if (K.isWriteable())
177    Flags |= ELF::SHF_WRITE;
178
179  if (K.isThreadLocal())
180    Flags |= ELF::SHF_TLS;
181
182  if (K.isMergeableCString() || K.isMergeableConst())
183    Flags |= ELF::SHF_MERGE;
184
185  if (K.isMergeableCString())
186    Flags |= ELF::SHF_STRINGS;
187
188  return Flags;
189}
190
191static const Comdat *getELFComdat(const GlobalValue *GV) {
192  const Comdat *C = GV->getComdat();
193  if (!C)
194    return nullptr;
195
196  if (C->getSelectionKind() != Comdat::Any)
197    report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
198                       C->getName() + "' cannot be lowered.");
199
200  return C;
201}
202
203MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
204    const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
205    const TargetMachine &TM) const {
206  StringRef SectionName = GV->getSection();
207
208  // Infer section flags from the section name if we can.
209  Kind = getELFKindForNamedSection(SectionName, Kind);
210
211  StringRef Group = "";
212  unsigned Flags = getELFSectionFlags(Kind);
213  if (const Comdat *C = getELFComdat(GV)) {
214    Group = C->getName();
215    Flags |= ELF::SHF_GROUP;
216  }
217  return getContext().getELFSection(SectionName,
218                                    getELFSectionType(SectionName, Kind), Flags,
219                                    /*EntrySize=*/0, Group);
220}
221
222/// Return the section prefix name used by options FunctionsSections and
223/// DataSections.
224static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
225  if (Kind.isText())
226    return ".text";
227  if (Kind.isReadOnly())
228    return ".rodata";
229  if (Kind.isBSS())
230    return ".bss";
231  if (Kind.isThreadData())
232    return ".tdata";
233  if (Kind.isThreadBSS())
234    return ".tbss";
235  if (Kind.isDataNoRel())
236    return ".data";
237  if (Kind.isDataRelLocal())
238    return ".data.rel.local";
239  if (Kind.isDataRel())
240    return ".data.rel";
241  if (Kind.isReadOnlyWithRelLocal())
242    return ".data.rel.ro.local";
243  assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
244  return ".data.rel.ro";
245}
246
247static MCSectionELF *
248selectELFSectionForGlobal(MCContext &Ctx, const GlobalValue *GV,
249                          SectionKind Kind, Mangler &Mang,
250                          const TargetMachine &TM, bool EmitUniqueSection,
251                          unsigned Flags, unsigned *NextUniqueID) {
252  unsigned EntrySize = 0;
253  if (Kind.isMergeableCString()) {
254    if (Kind.isMergeable2ByteCString()) {
255      EntrySize = 2;
256    } else if (Kind.isMergeable4ByteCString()) {
257      EntrySize = 4;
258    } else {
259      EntrySize = 1;
260      assert(Kind.isMergeable1ByteCString() && "unknown string width");
261    }
262  } else if (Kind.isMergeableConst()) {
263    if (Kind.isMergeableConst4()) {
264      EntrySize = 4;
265    } else if (Kind.isMergeableConst8()) {
266      EntrySize = 8;
267    } else {
268      assert(Kind.isMergeableConst16() && "unknown data width");
269      EntrySize = 16;
270    }
271  }
272
273  StringRef Group = "";
274  if (const Comdat *C = getELFComdat(GV)) {
275    Flags |= ELF::SHF_GROUP;
276    Group = C->getName();
277  }
278
279  bool UniqueSectionNames = TM.getUniqueSectionNames();
280  SmallString<128> Name;
281  if (Kind.isMergeableCString()) {
282    // We also need alignment here.
283    // FIXME: this is getting the alignment of the character, not the
284    // alignment of the global!
285    unsigned Align =
286        TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV));
287
288    std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
289    Name = SizeSpec + utostr(Align);
290  } else if (Kind.isMergeableConst()) {
291    Name = ".rodata.cst";
292    Name += utostr(EntrySize);
293  } else {
294    Name = getSectionPrefixForGlobal(Kind);
295  }
296
297  if (EmitUniqueSection && UniqueSectionNames) {
298    Name.push_back('.');
299    TM.getNameWithPrefix(Name, GV, Mang, true);
300  }
301  unsigned UniqueID = ~0;
302  if (EmitUniqueSection && !UniqueSectionNames) {
303    UniqueID = *NextUniqueID;
304    (*NextUniqueID)++;
305  }
306  return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags,
307                           EntrySize, Group, UniqueID);
308}
309
310MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
311    const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
312    const TargetMachine &TM) const {
313  unsigned Flags = getELFSectionFlags(Kind);
314
315  // If we have -ffunction-section or -fdata-section then we should emit the
316  // global value to a uniqued section specifically for it.
317  bool EmitUniqueSection = false;
318  if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
319    if (Kind.isText())
320      EmitUniqueSection = TM.getFunctionSections();
321    else
322      EmitUniqueSection = TM.getDataSections();
323  }
324  EmitUniqueSection |= GV->hasComdat();
325
326  return selectELFSectionForGlobal(getContext(), GV, Kind, Mang, TM,
327                                   EmitUniqueSection, Flags, &NextUniqueID);
328}
329
330MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
331    const Function &F, Mangler &Mang, const TargetMachine &TM) const {
332  // If the function can be removed, produce a unique section so that
333  // the table doesn't prevent the removal.
334  const Comdat *C = F.getComdat();
335  bool EmitUniqueSection = TM.getFunctionSections() || C;
336  if (!EmitUniqueSection)
337    return ReadOnlySection;
338
339  return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
340                                   Mang, TM, EmitUniqueSection, ELF::SHF_ALLOC,
341                                   &NextUniqueID);
342}
343
344bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
345    bool UsesLabelDifference, const Function &F) const {
346  // We can always create relative relocations, so use another section
347  // that can be marked non-executable.
348  return false;
349}
350
351/// Given a mergeable constant with the specified size and relocation
352/// information, return a section that it should be placed in.
353MCSection *
354TargetLoweringObjectFileELF::getSectionForConstant(SectionKind Kind,
355                                                   const Constant *C) const {
356  if (Kind.isMergeableConst4() && MergeableConst4Section)
357    return MergeableConst4Section;
358  if (Kind.isMergeableConst8() && MergeableConst8Section)
359    return MergeableConst8Section;
360  if (Kind.isMergeableConst16() && MergeableConst16Section)
361    return MergeableConst16Section;
362  if (Kind.isReadOnly())
363    return ReadOnlySection;
364
365  if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
366  assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
367  return DataRelROSection;
368}
369
370static MCSectionELF *getStaticStructorSection(MCContext &Ctx, bool UseInitArray,
371                                              bool IsCtor, unsigned Priority,
372                                              const MCSymbol *KeySym) {
373  std::string Name;
374  unsigned Type;
375  unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
376  StringRef COMDAT = KeySym ? KeySym->getName() : "";
377
378  if (KeySym)
379    Flags |= ELF::SHF_GROUP;
380
381  if (UseInitArray) {
382    if (IsCtor) {
383      Type = ELF::SHT_INIT_ARRAY;
384      Name = ".init_array";
385    } else {
386      Type = ELF::SHT_FINI_ARRAY;
387      Name = ".fini_array";
388    }
389    if (Priority != 65535) {
390      Name += '.';
391      Name += utostr(Priority);
392    }
393  } else {
394    // The default scheme is .ctor / .dtor, so we have to invert the priority
395    // numbering.
396    if (IsCtor)
397      Name = ".ctors";
398    else
399      Name = ".dtors";
400    if (Priority != 65535) {
401      Name += '.';
402      Name += utostr(65535 - Priority);
403    }
404    Type = ELF::SHT_PROGBITS;
405  }
406
407  return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
408}
409
410MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
411    unsigned Priority, const MCSymbol *KeySym) const {
412  return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
413                                  KeySym);
414}
415
416MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
417    unsigned Priority, const MCSymbol *KeySym) const {
418  return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
419                                  KeySym);
420}
421
422void
423TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
424  UseInitArray = UseInitArray_;
425  if (!UseInitArray)
426    return;
427
428  StaticCtorSection = getContext().getELFSection(
429      ".init_array", ELF::SHT_INIT_ARRAY, ELF::SHF_WRITE | ELF::SHF_ALLOC);
430  StaticDtorSection = getContext().getELFSection(
431      ".fini_array", ELF::SHT_FINI_ARRAY, ELF::SHF_WRITE | ELF::SHF_ALLOC);
432}
433
434//===----------------------------------------------------------------------===//
435//                                 MachO
436//===----------------------------------------------------------------------===//
437
438TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
439  : TargetLoweringObjectFile() {
440  SupportIndirectSymViaGOTPCRel = true;
441}
442
443/// emitModuleFlags - Perform code emission for module flags.
444void TargetLoweringObjectFileMachO::
445emitModuleFlags(MCStreamer &Streamer,
446                ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
447                Mangler &Mang, const TargetMachine &TM) const {
448  unsigned VersionVal = 0;
449  unsigned ImageInfoFlags = 0;
450  MDNode *LinkerOptions = nullptr;
451  StringRef SectionVal;
452
453  for (ArrayRef<Module::ModuleFlagEntry>::iterator
454         i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
455    const Module::ModuleFlagEntry &MFE = *i;
456
457    // Ignore flags with 'Require' behavior.
458    if (MFE.Behavior == Module::Require)
459      continue;
460
461    StringRef Key = MFE.Key->getString();
462    Metadata *Val = MFE.Val;
463
464    if (Key == "Objective-C Image Info Version") {
465      VersionVal = mdconst::extract<ConstantInt>(Val)->getZExtValue();
466    } else if (Key == "Objective-C Garbage Collection" ||
467               Key == "Objective-C GC Only" ||
468               Key == "Objective-C Is Simulated" ||
469               Key == "Objective-C Image Swift Version") {
470      ImageInfoFlags |= mdconst::extract<ConstantInt>(Val)->getZExtValue();
471    } else if (Key == "Objective-C Image Info Section") {
472      SectionVal = cast<MDString>(Val)->getString();
473    } else if (Key == "Linker Options") {
474      LinkerOptions = cast<MDNode>(Val);
475    }
476  }
477
478  // Emit the linker options if present.
479  if (LinkerOptions) {
480    for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
481      MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
482      SmallVector<std::string, 4> StrOptions;
483
484      // Convert to strings.
485      for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
486        MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
487        StrOptions.push_back(MDOption->getString());
488      }
489
490      Streamer.EmitLinkerOptions(StrOptions);
491    }
492  }
493
494  // The section is mandatory. If we don't have it, then we don't have GC info.
495  if (SectionVal.empty()) return;
496
497  StringRef Segment, Section;
498  unsigned TAA = 0, StubSize = 0;
499  bool TAAParsed;
500  std::string ErrorCode =
501    MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
502                                          TAA, TAAParsed, StubSize);
503  if (!ErrorCode.empty())
504    // If invalid, report the error with report_fatal_error.
505    report_fatal_error("Invalid section specifier '" + Section + "': " +
506                       ErrorCode + ".");
507
508  // Get the section.
509  MCSectionMachO *S = getContext().getMachOSection(
510      Segment, Section, TAA, StubSize, SectionKind::getDataNoRel());
511  Streamer.SwitchSection(S);
512  Streamer.EmitLabel(getContext().
513                     getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
514  Streamer.EmitIntValue(VersionVal, 4);
515  Streamer.EmitIntValue(ImageInfoFlags, 4);
516  Streamer.AddBlankLine();
517}
518
519static void checkMachOComdat(const GlobalValue *GV) {
520  const Comdat *C = GV->getComdat();
521  if (!C)
522    return;
523
524  report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
525                     "' cannot be lowered.");
526}
527
528MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
529    const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
530    const TargetMachine &TM) const {
531  // Parse the section specifier and create it if valid.
532  StringRef Segment, Section;
533  unsigned TAA = 0, StubSize = 0;
534  bool TAAParsed;
535
536  checkMachOComdat(GV);
537
538  std::string ErrorCode =
539    MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
540                                          TAA, TAAParsed, StubSize);
541  if (!ErrorCode.empty()) {
542    // If invalid, report the error with report_fatal_error.
543    report_fatal_error("Global variable '" + GV->getName() +
544                       "' has an invalid section specifier '" +
545                       GV->getSection() + "': " + ErrorCode + ".");
546  }
547
548  // Get the section.
549  MCSectionMachO *S =
550      getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
551
552  // If TAA wasn't set by ParseSectionSpecifier() above,
553  // use the value returned by getMachOSection() as a default.
554  if (!TAAParsed)
555    TAA = S->getTypeAndAttributes();
556
557  // Okay, now that we got the section, verify that the TAA & StubSize agree.
558  // If the user declared multiple globals with different section flags, we need
559  // to reject it here.
560  if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
561    // If invalid, report the error with report_fatal_error.
562    report_fatal_error("Global variable '" + GV->getName() +
563                       "' section type or attributes does not match previous"
564                       " section specifier");
565  }
566
567  return S;
568}
569
570MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
571    const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
572    const TargetMachine &TM) const {
573  checkMachOComdat(GV);
574
575  // Handle thread local data.
576  if (Kind.isThreadBSS()) return TLSBSSSection;
577  if (Kind.isThreadData()) return TLSDataSection;
578
579  if (Kind.isText())
580    return GV->isWeakForLinker() ? TextCoalSection : TextSection;
581
582  // If this is weak/linkonce, put this in a coalescable section, either in text
583  // or data depending on if it is writable.
584  if (GV->isWeakForLinker()) {
585    if (Kind.isReadOnly())
586      return ConstTextCoalSection;
587    return DataCoalSection;
588  }
589
590  // FIXME: Alignment check should be handled by section classifier.
591  if (Kind.isMergeable1ByteCString() &&
592      TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
593    return CStringSection;
594
595  // Do not put 16-bit arrays in the UString section if they have an
596  // externally visible label, this runs into issues with certain linker
597  // versions.
598  if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
599      TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
600    return UStringSection;
601
602  // With MachO only variables whose corresponding symbol starts with 'l' or
603  // 'L' can be merged, so we only try merging GVs with private linkage.
604  if (GV->hasPrivateLinkage() && Kind.isMergeableConst()) {
605    if (Kind.isMergeableConst4())
606      return FourByteConstantSection;
607    if (Kind.isMergeableConst8())
608      return EightByteConstantSection;
609    if (Kind.isMergeableConst16())
610      return SixteenByteConstantSection;
611  }
612
613  // Otherwise, if it is readonly, but not something we can specially optimize,
614  // just drop it in .const.
615  if (Kind.isReadOnly())
616    return ReadOnlySection;
617
618  // If this is marked const, put it into a const section.  But if the dynamic
619  // linker needs to write to it, put it in the data segment.
620  if (Kind.isReadOnlyWithRel())
621    return ConstDataSection;
622
623  // Put zero initialized globals with strong external linkage in the
624  // DATA, __common section with the .zerofill directive.
625  if (Kind.isBSSExtern())
626    return DataCommonSection;
627
628  // Put zero initialized globals with local linkage in __DATA,__bss directive
629  // with the .zerofill directive (aka .lcomm).
630  if (Kind.isBSSLocal())
631    return DataBSSSection;
632
633  // Otherwise, just drop the variable in the normal data section.
634  return DataSection;
635}
636
637MCSection *
638TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind,
639                                                     const Constant *C) const {
640  // If this constant requires a relocation, we have to put it in the data
641  // segment, not in the text segment.
642  if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
643    return ConstDataSection;
644
645  if (Kind.isMergeableConst4())
646    return FourByteConstantSection;
647  if (Kind.isMergeableConst8())
648    return EightByteConstantSection;
649  if (Kind.isMergeableConst16())
650    return SixteenByteConstantSection;
651  return ReadOnlySection;  // .const
652}
653
654const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
655    const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
656    const TargetMachine &TM, MachineModuleInfo *MMI,
657    MCStreamer &Streamer) const {
658  // The mach-o version of this method defaults to returning a stub reference.
659
660  if (Encoding & DW_EH_PE_indirect) {
661    MachineModuleInfoMachO &MachOMMI =
662      MMI->getObjFileInfo<MachineModuleInfoMachO>();
663
664    MCSymbol *SSym =
665        getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
666
667    // Add information about the stub reference to MachOMMI so that the stub
668    // gets emitted by the asmprinter.
669    MachineModuleInfoImpl::StubValueTy &StubSym =
670      GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
671                                  MachOMMI.getGVStubEntry(SSym);
672    if (!StubSym.getPointer()) {
673      MCSymbol *Sym = TM.getSymbol(GV, Mang);
674      StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
675    }
676
677    return TargetLoweringObjectFile::
678      getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
679                        Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
680  }
681
682  return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
683                                                           TM, MMI, Streamer);
684}
685
686MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
687    const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
688    MachineModuleInfo *MMI) const {
689  // The mach-o version of this method defaults to returning a stub reference.
690  MachineModuleInfoMachO &MachOMMI =
691    MMI->getObjFileInfo<MachineModuleInfoMachO>();
692
693  MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
694
695  // Add information about the stub reference to MachOMMI so that the stub
696  // gets emitted by the asmprinter.
697  MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
698  if (!StubSym.getPointer()) {
699    MCSymbol *Sym = TM.getSymbol(GV, Mang);
700    StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
701  }
702
703  return SSym;
704}
705
706const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
707    const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
708    MachineModuleInfo *MMI, MCStreamer &Streamer) const {
709  // Although MachO 32-bit targets do not explictly have a GOTPCREL relocation
710  // as 64-bit do, we replace the GOT equivalent by accessing the final symbol
711  // through a non_lazy_ptr stub instead. One advantage is that it allows the
712  // computation of deltas to final external symbols. Example:
713  //
714  //    _extgotequiv:
715  //       .long   _extfoo
716  //
717  //    _delta:
718  //       .long   _extgotequiv-_delta
719  //
720  // is transformed to:
721  //
722  //    _delta:
723  //       .long   L_extfoo$non_lazy_ptr-(_delta+0)
724  //
725  //       .section        __IMPORT,__pointers,non_lazy_symbol_pointers
726  //    L_extfoo$non_lazy_ptr:
727  //       .indirect_symbol        _extfoo
728  //       .long   0
729  //
730  MachineModuleInfoMachO &MachOMMI =
731    MMI->getObjFileInfo<MachineModuleInfoMachO>();
732  MCContext &Ctx = getContext();
733
734  // The offset must consider the original displacement from the base symbol
735  // since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
736  Offset = -MV.getConstant();
737  const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
738
739  // Access the final symbol via sym$non_lazy_ptr and generate the appropriated
740  // non_lazy_ptr stubs.
741  SmallString<128> Name;
742  StringRef Suffix = "$non_lazy_ptr";
743  Name += DL->getPrivateGlobalPrefix();
744  Name += Sym->getName();
745  Name += Suffix;
746  MCSymbol *Stub = Ctx.getOrCreateSymbol(Name);
747
748  MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
749  if (!StubSym.getPointer())
750    StubSym = MachineModuleInfoImpl::
751      StubValueTy(const_cast<MCSymbol *>(Sym), true /* access indirectly */);
752
753  const MCExpr *BSymExpr =
754    MCSymbolRefExpr::create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
755  const MCExpr *LHS =
756    MCSymbolRefExpr::create(Stub, MCSymbolRefExpr::VK_None, Ctx);
757
758  if (!Offset)
759    return MCBinaryExpr::createSub(LHS, BSymExpr, Ctx);
760
761  const MCExpr *RHS =
762    MCBinaryExpr::createAdd(BSymExpr, MCConstantExpr::create(Offset, Ctx), Ctx);
763  return MCBinaryExpr::createSub(LHS, RHS, Ctx);
764}
765
766//===----------------------------------------------------------------------===//
767//                                  COFF
768//===----------------------------------------------------------------------===//
769
770static unsigned
771getCOFFSectionFlags(SectionKind K) {
772  unsigned Flags = 0;
773
774  if (K.isMetadata())
775    Flags |=
776      COFF::IMAGE_SCN_MEM_DISCARDABLE;
777  else if (K.isText())
778    Flags |=
779      COFF::IMAGE_SCN_MEM_EXECUTE |
780      COFF::IMAGE_SCN_MEM_READ |
781      COFF::IMAGE_SCN_CNT_CODE;
782  else if (K.isBSS())
783    Flags |=
784      COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
785      COFF::IMAGE_SCN_MEM_READ |
786      COFF::IMAGE_SCN_MEM_WRITE;
787  else if (K.isThreadLocal())
788    Flags |=
789      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
790      COFF::IMAGE_SCN_MEM_READ |
791      COFF::IMAGE_SCN_MEM_WRITE;
792  else if (K.isReadOnly() || K.isReadOnlyWithRel())
793    Flags |=
794      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
795      COFF::IMAGE_SCN_MEM_READ;
796  else if (K.isWriteable())
797    Flags |=
798      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
799      COFF::IMAGE_SCN_MEM_READ |
800      COFF::IMAGE_SCN_MEM_WRITE;
801
802  return Flags;
803}
804
805static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
806  const Comdat *C = GV->getComdat();
807  assert(C && "expected GV to have a Comdat!");
808
809  StringRef ComdatGVName = C->getName();
810  const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
811  if (!ComdatGV)
812    report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
813                       "' does not exist.");
814
815  if (ComdatGV->getComdat() != C)
816    report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
817                       "' is not a key for its COMDAT.");
818
819  return ComdatGV;
820}
821
822static int getSelectionForCOFF(const GlobalValue *GV) {
823  if (const Comdat *C = GV->getComdat()) {
824    const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
825    if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
826      ComdatKey = GA->getBaseObject();
827    if (ComdatKey == GV) {
828      switch (C->getSelectionKind()) {
829      case Comdat::Any:
830        return COFF::IMAGE_COMDAT_SELECT_ANY;
831      case Comdat::ExactMatch:
832        return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
833      case Comdat::Largest:
834        return COFF::IMAGE_COMDAT_SELECT_LARGEST;
835      case Comdat::NoDuplicates:
836        return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
837      case Comdat::SameSize:
838        return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
839      }
840    } else {
841      return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
842    }
843  }
844  return 0;
845}
846
847MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
848    const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
849    const TargetMachine &TM) const {
850  int Selection = 0;
851  unsigned Characteristics = getCOFFSectionFlags(Kind);
852  StringRef Name = GV->getSection();
853  StringRef COMDATSymName = "";
854  if (GV->hasComdat()) {
855    Selection = getSelectionForCOFF(GV);
856    const GlobalValue *ComdatGV;
857    if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
858      ComdatGV = getComdatGVForCOFF(GV);
859    else
860      ComdatGV = GV;
861
862    if (!ComdatGV->hasPrivateLinkage()) {
863      MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
864      COMDATSymName = Sym->getName();
865      Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
866    } else {
867      Selection = 0;
868    }
869  }
870  return getContext().getCOFFSection(Name,
871                                     Characteristics,
872                                     Kind,
873                                     COMDATSymName,
874                                     Selection);
875}
876
877static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
878  if (Kind.isText())
879    return ".text";
880  if (Kind.isBSS())
881    return ".bss";
882  if (Kind.isThreadLocal())
883    return ".tls$";
884  if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
885    return ".rdata";
886  return ".data";
887}
888
889MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
890    const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
891    const TargetMachine &TM) const {
892  // If we have -ffunction-sections then we should emit the global value to a
893  // uniqued section specifically for it.
894  bool EmitUniquedSection;
895  if (Kind.isText())
896    EmitUniquedSection = TM.getFunctionSections();
897  else
898    EmitUniquedSection = TM.getDataSections();
899
900  if ((EmitUniquedSection && !Kind.isCommon()) || GV->hasComdat()) {
901    const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
902    unsigned Characteristics = getCOFFSectionFlags(Kind);
903
904    Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
905    int Selection = getSelectionForCOFF(GV);
906    if (!Selection)
907      Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
908    const GlobalValue *ComdatGV;
909    if (GV->hasComdat())
910      ComdatGV = getComdatGVForCOFF(GV);
911    else
912      ComdatGV = GV;
913
914    if (!ComdatGV->hasPrivateLinkage()) {
915      MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
916      StringRef COMDATSymName = Sym->getName();
917      return getContext().getCOFFSection(Name, Characteristics, Kind,
918                                         COMDATSymName, Selection);
919    } else {
920      SmallString<256> TmpData;
921      getNameWithPrefix(TmpData, GV, /*CannotUsePrivateLabel=*/true, Mang, TM);
922      return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
923                                         Selection);
924    }
925  }
926
927  if (Kind.isText())
928    return TextSection;
929
930  if (Kind.isThreadLocal())
931    return TLSDataSection;
932
933  if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
934    return ReadOnlySection;
935
936  // Note: we claim that common symbols are put in BSSSection, but they are
937  // really emitted with the magic .comm directive, which creates a symbol table
938  // entry but not a section.
939  if (Kind.isBSS() || Kind.isCommon())
940    return BSSSection;
941
942  return DataSection;
943}
944
945void TargetLoweringObjectFileCOFF::getNameWithPrefix(
946    SmallVectorImpl<char> &OutName, const GlobalValue *GV,
947    bool CannotUsePrivateLabel, Mangler &Mang, const TargetMachine &TM) const {
948  if (GV->hasPrivateLinkage() &&
949      ((isa<Function>(GV) && TM.getFunctionSections()) ||
950       (isa<GlobalVariable>(GV) && TM.getDataSections())))
951    CannotUsePrivateLabel = true;
952
953  Mang.getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
954}
955
956MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
957    const Function &F, Mangler &Mang, const TargetMachine &TM) const {
958  // If the function can be removed, produce a unique section so that
959  // the table doesn't prevent the removal.
960  const Comdat *C = F.getComdat();
961  bool EmitUniqueSection = TM.getFunctionSections() || C;
962  if (!EmitUniqueSection)
963    return ReadOnlySection;
964
965  // FIXME: we should produce a symbol for F instead.
966  if (F.hasPrivateLinkage())
967    return ReadOnlySection;
968
969  MCSymbol *Sym = TM.getSymbol(&F, Mang);
970  StringRef COMDATSymName = Sym->getName();
971
972  SectionKind Kind = SectionKind::getReadOnly();
973  const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
974  unsigned Characteristics = getCOFFSectionFlags(Kind);
975  Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
976
977  return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
978                                     COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
979}
980
981void TargetLoweringObjectFileCOFF::
982emitModuleFlags(MCStreamer &Streamer,
983                ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
984                Mangler &Mang, const TargetMachine &TM) const {
985  MDNode *LinkerOptions = nullptr;
986
987  // Look for the "Linker Options" flag, since it's the only one we support.
988  for (ArrayRef<Module::ModuleFlagEntry>::iterator
989       i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
990    const Module::ModuleFlagEntry &MFE = *i;
991    StringRef Key = MFE.Key->getString();
992    Metadata *Val = MFE.Val;
993    if (Key == "Linker Options") {
994      LinkerOptions = cast<MDNode>(Val);
995      break;
996    }
997  }
998  if (!LinkerOptions)
999    return;
1000
1001  // Emit the linker options to the linker .drectve section.  According to the
1002  // spec, this section is a space-separated string containing flags for linker.
1003  MCSection *Sec = getDrectveSection();
1004  Streamer.SwitchSection(Sec);
1005  for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
1006    MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
1007    for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
1008      MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
1009      // Lead with a space for consistency with our dllexport implementation.
1010      std::string Directive(" ");
1011      Directive.append(MDOption->getString());
1012      Streamer.EmitBytes(Directive);
1013    }
1014  }
1015}
1016
1017MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
1018    unsigned Priority, const MCSymbol *KeySym) const {
1019  return getContext().getAssociativeCOFFSection(
1020      cast<MCSectionCOFF>(StaticCtorSection), KeySym);
1021}
1022
1023MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
1024    unsigned Priority, const MCSymbol *KeySym) const {
1025  return getContext().getAssociativeCOFFSection(
1026      cast<MCSectionCOFF>(StaticDtorSection), KeySym);
1027}
1028
1029void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
1030    raw_ostream &OS, const GlobalValue *GV, const Mangler &Mang) const {
1031  if (!GV->hasDLLExportStorageClass() || GV->isDeclaration())
1032    return;
1033
1034  const Triple &TT = getTargetTriple();
1035
1036  if (TT.isKnownWindowsMSVCEnvironment())
1037    OS << " /EXPORT:";
1038  else
1039    OS << " -export:";
1040
1041  if (TT.isWindowsGNUEnvironment() || TT.isWindowsCygwinEnvironment()) {
1042    std::string Flag;
1043    raw_string_ostream FlagOS(Flag);
1044    Mang.getNameWithPrefix(FlagOS, GV, false);
1045    FlagOS.flush();
1046    if (Flag[0] == DL->getGlobalPrefix())
1047      OS << Flag.substr(1);
1048    else
1049      OS << Flag;
1050  } else {
1051    Mang.getNameWithPrefix(OS, GV, false);
1052  }
1053
1054  if (!GV->getValueType()->isFunctionTy()) {
1055    if (TT.isKnownWindowsMSVCEnvironment())
1056      OS << ",DATA";
1057    else
1058      OS << ",data";
1059  }
1060}
1061