1//===- llvm/CodeGen/TargetLoweringObjectFileImpl.cpp - Object File Info ---===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements classes used to handle lowerings specific to common
10// object file formats.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
15#include "llvm/ADT/SmallString.h"
16#include "llvm/ADT/SmallVector.h"
17#include "llvm/ADT/StringExtras.h"
18#include "llvm/ADT/StringRef.h"
19#include "llvm/ADT/Triple.h"
20#include "llvm/BinaryFormat/COFF.h"
21#include "llvm/BinaryFormat/Dwarf.h"
22#include "llvm/BinaryFormat/ELF.h"
23#include "llvm/BinaryFormat/MachO.h"
24#include "llvm/CodeGen/MachineModuleInfo.h"
25#include "llvm/CodeGen/MachineModuleInfoImpls.h"
26#include "llvm/IR/Comdat.h"
27#include "llvm/IR/Constants.h"
28#include "llvm/IR/DataLayout.h"
29#include "llvm/IR/DerivedTypes.h"
30#include "llvm/IR/Function.h"
31#include "llvm/IR/GlobalAlias.h"
32#include "llvm/IR/GlobalObject.h"
33#include "llvm/IR/GlobalValue.h"
34#include "llvm/IR/GlobalVariable.h"
35#include "llvm/IR/Mangler.h"
36#include "llvm/IR/Metadata.h"
37#include "llvm/IR/Module.h"
38#include "llvm/IR/Type.h"
39#include "llvm/MC/MCAsmInfo.h"
40#include "llvm/MC/MCContext.h"
41#include "llvm/MC/MCExpr.h"
42#include "llvm/MC/MCSectionCOFF.h"
43#include "llvm/MC/MCSectionELF.h"
44#include "llvm/MC/MCSectionMachO.h"
45#include "llvm/MC/MCSectionWasm.h"
46#include "llvm/MC/MCSectionXCOFF.h"
47#include "llvm/MC/MCStreamer.h"
48#include "llvm/MC/MCSymbol.h"
49#include "llvm/MC/MCSymbolELF.h"
50#include "llvm/MC/MCValue.h"
51#include "llvm/MC/SectionKind.h"
52#include "llvm/ProfileData/InstrProf.h"
53#include "llvm/Support/Casting.h"
54#include "llvm/Support/CodeGen.h"
55#include "llvm/Support/Format.h"
56#include "llvm/Support/ErrorHandling.h"
57#include "llvm/Support/raw_ostream.h"
58#include "llvm/Target/TargetMachine.h"
59#include <cassert>
60#include <string>
61
62using namespace llvm;
63using namespace dwarf;
64
65static void GetObjCImageInfo(Module &M, unsigned &Version, unsigned &Flags,
66                             StringRef &Section) {
67  SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
68  M.getModuleFlagsMetadata(ModuleFlags);
69
70  for (const auto &MFE: ModuleFlags) {
71    // Ignore flags with 'Require' behaviour.
72    if (MFE.Behavior == Module::Require)
73      continue;
74
75    StringRef Key = MFE.Key->getString();
76    if (Key == "Objective-C Image Info Version") {
77      Version = mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
78    } else if (Key == "Objective-C Garbage Collection" ||
79               Key == "Objective-C GC Only" ||
80               Key == "Objective-C Is Simulated" ||
81               Key == "Objective-C Class Properties" ||
82               Key == "Objective-C Image Swift Version") {
83      Flags |= mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
84    } else if (Key == "Objective-C Image Info Section") {
85      Section = cast<MDString>(MFE.Val)->getString();
86    }
87  }
88}
89
90//===----------------------------------------------------------------------===//
91//                                  ELF
92//===----------------------------------------------------------------------===//
93
94void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
95                                             const TargetMachine &TgtM) {
96  TargetLoweringObjectFile::Initialize(Ctx, TgtM);
97  TM = &TgtM;
98
99  CodeModel::Model CM = TgtM.getCodeModel();
100
101  switch (TgtM.getTargetTriple().getArch()) {
102  case Triple::arm:
103  case Triple::armeb:
104  case Triple::thumb:
105  case Triple::thumbeb:
106    if (Ctx.getAsmInfo()->getExceptionHandlingType() == ExceptionHandling::ARM)
107      break;
108    // Fallthrough if not using EHABI
109    LLVM_FALLTHROUGH;
110  case Triple::ppc:
111  case Triple::x86:
112    PersonalityEncoding = isPositionIndependent()
113                              ? dwarf::DW_EH_PE_indirect |
114                                    dwarf::DW_EH_PE_pcrel |
115                                    dwarf::DW_EH_PE_sdata4
116                              : dwarf::DW_EH_PE_absptr;
117    LSDAEncoding = isPositionIndependent()
118                       ? dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
119                       : dwarf::DW_EH_PE_absptr;
120    TTypeEncoding = isPositionIndependent()
121                        ? dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
122                              dwarf::DW_EH_PE_sdata4
123                        : dwarf::DW_EH_PE_absptr;
124    break;
125  case Triple::x86_64:
126    if (isPositionIndependent()) {
127      PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
128        ((CM == CodeModel::Small || CM == CodeModel::Medium)
129         ? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
130      LSDAEncoding = dwarf::DW_EH_PE_pcrel |
131        (CM == CodeModel::Small
132         ? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
133      TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
134        ((CM == CodeModel::Small || CM == CodeModel::Medium)
135         ? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
136    } else {
137      PersonalityEncoding =
138        (CM == CodeModel::Small || CM == CodeModel::Medium)
139        ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
140      LSDAEncoding = (CM == CodeModel::Small)
141        ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
142      TTypeEncoding = (CM == CodeModel::Small)
143        ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
144    }
145    break;
146  case Triple::hexagon:
147    PersonalityEncoding = dwarf::DW_EH_PE_absptr;
148    LSDAEncoding = dwarf::DW_EH_PE_absptr;
149    TTypeEncoding = dwarf::DW_EH_PE_absptr;
150    if (isPositionIndependent()) {
151      PersonalityEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
152      LSDAEncoding |= dwarf::DW_EH_PE_pcrel;
153      TTypeEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
154    }
155    break;
156  case Triple::aarch64:
157  case Triple::aarch64_be:
158  case Triple::aarch64_32:
159    // The small model guarantees static code/data size < 4GB, but not where it
160    // will be in memory. Most of these could end up >2GB away so even a signed
161    // pc-relative 32-bit address is insufficient, theoretically.
162    if (isPositionIndependent()) {
163      PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
164        dwarf::DW_EH_PE_sdata8;
165      LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8;
166      TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
167        dwarf::DW_EH_PE_sdata8;
168    } else {
169      PersonalityEncoding = dwarf::DW_EH_PE_absptr;
170      LSDAEncoding = dwarf::DW_EH_PE_absptr;
171      TTypeEncoding = dwarf::DW_EH_PE_absptr;
172    }
173    break;
174  case Triple::lanai:
175    LSDAEncoding = dwarf::DW_EH_PE_absptr;
176    PersonalityEncoding = dwarf::DW_EH_PE_absptr;
177    TTypeEncoding = dwarf::DW_EH_PE_absptr;
178    break;
179  case Triple::mips:
180  case Triple::mipsel:
181  case Triple::mips64:
182  case Triple::mips64el:
183    // MIPS uses indirect pointer to refer personality functions and types, so
184    // that the eh_frame section can be read-only. DW.ref.personality will be
185    // generated for relocation.
186    PersonalityEncoding = dwarf::DW_EH_PE_indirect;
187    // FIXME: The N64 ABI probably ought to use DW_EH_PE_sdata8 but we can't
188    //        identify N64 from just a triple.
189    TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
190                    dwarf::DW_EH_PE_sdata4;
191    // We don't support PC-relative LSDA references in GAS so we use the default
192    // DW_EH_PE_absptr for those.
193
194    // FreeBSD must be explicit about the data size and using pcrel since it's
195    // assembler/linker won't do the automatic conversion that the Linux tools
196    // do.
197    if (TgtM.getTargetTriple().isOSFreeBSD()) {
198      PersonalityEncoding |= dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
199      LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
200    }
201    break;
202  case Triple::ppc64:
203  case Triple::ppc64le:
204    PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
205      dwarf::DW_EH_PE_udata8;
206    LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8;
207    TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
208      dwarf::DW_EH_PE_udata8;
209    break;
210  case Triple::sparcel:
211  case Triple::sparc:
212    if (isPositionIndependent()) {
213      LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
214      PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
215        dwarf::DW_EH_PE_sdata4;
216      TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
217        dwarf::DW_EH_PE_sdata4;
218    } else {
219      LSDAEncoding = dwarf::DW_EH_PE_absptr;
220      PersonalityEncoding = dwarf::DW_EH_PE_absptr;
221      TTypeEncoding = dwarf::DW_EH_PE_absptr;
222    }
223    CallSiteEncoding = dwarf::DW_EH_PE_udata4;
224    break;
225  case Triple::riscv32:
226  case Triple::riscv64:
227    LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
228    PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
229                          dwarf::DW_EH_PE_sdata4;
230    TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
231                    dwarf::DW_EH_PE_sdata4;
232    CallSiteEncoding = dwarf::DW_EH_PE_udata4;
233    break;
234  case Triple::sparcv9:
235    LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
236    if (isPositionIndependent()) {
237      PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
238        dwarf::DW_EH_PE_sdata4;
239      TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
240        dwarf::DW_EH_PE_sdata4;
241    } else {
242      PersonalityEncoding = dwarf::DW_EH_PE_absptr;
243      TTypeEncoding = dwarf::DW_EH_PE_absptr;
244    }
245    break;
246  case Triple::systemz:
247    // All currently-defined code models guarantee that 4-byte PC-relative
248    // values will be in range.
249    if (isPositionIndependent()) {
250      PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
251        dwarf::DW_EH_PE_sdata4;
252      LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
253      TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
254        dwarf::DW_EH_PE_sdata4;
255    } else {
256      PersonalityEncoding = dwarf::DW_EH_PE_absptr;
257      LSDAEncoding = dwarf::DW_EH_PE_absptr;
258      TTypeEncoding = dwarf::DW_EH_PE_absptr;
259    }
260    break;
261  default:
262    break;
263  }
264}
265
266void TargetLoweringObjectFileELF::emitModuleMetadata(MCStreamer &Streamer,
267                                                     Module &M) const {
268  auto &C = getContext();
269
270  if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
271    auto *S = C.getELFSection(".linker-options", ELF::SHT_LLVM_LINKER_OPTIONS,
272                              ELF::SHF_EXCLUDE);
273
274    Streamer.SwitchSection(S);
275
276    for (const auto *Operand : LinkerOptions->operands()) {
277      if (cast<MDNode>(Operand)->getNumOperands() != 2)
278        report_fatal_error("invalid llvm.linker.options");
279      for (const auto &Option : cast<MDNode>(Operand)->operands()) {
280        Streamer.EmitBytes(cast<MDString>(Option)->getString());
281        Streamer.EmitIntValue(0, 1);
282      }
283    }
284  }
285
286  if (NamedMDNode *DependentLibraries = M.getNamedMetadata("llvm.dependent-libraries")) {
287    auto *S = C.getELFSection(".deplibs", ELF::SHT_LLVM_DEPENDENT_LIBRARIES,
288                              ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
289
290    Streamer.SwitchSection(S);
291
292    for (const auto *Operand : DependentLibraries->operands()) {
293      Streamer.EmitBytes(
294          cast<MDString>(cast<MDNode>(Operand)->getOperand(0))->getString());
295      Streamer.EmitIntValue(0, 1);
296    }
297  }
298
299  unsigned Version = 0;
300  unsigned Flags = 0;
301  StringRef Section;
302
303  GetObjCImageInfo(M, Version, Flags, Section);
304  if (!Section.empty()) {
305    auto *S = C.getELFSection(Section, ELF::SHT_PROGBITS, ELF::SHF_ALLOC);
306    Streamer.SwitchSection(S);
307    Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
308    Streamer.EmitIntValue(Version, 4);
309    Streamer.EmitIntValue(Flags, 4);
310    Streamer.AddBlankLine();
311  }
312
313  SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
314  M.getModuleFlagsMetadata(ModuleFlags);
315
316  MDNode *CFGProfile = nullptr;
317
318  for (const auto &MFE : ModuleFlags) {
319    StringRef Key = MFE.Key->getString();
320    if (Key == "CG Profile") {
321      CFGProfile = cast<MDNode>(MFE.Val);
322      break;
323    }
324  }
325
326  if (!CFGProfile)
327    return;
328
329  auto GetSym = [this](const MDOperand &MDO) -> MCSymbol * {
330    if (!MDO)
331      return nullptr;
332    auto V = cast<ValueAsMetadata>(MDO);
333    const Function *F = cast<Function>(V->getValue());
334    return TM->getSymbol(F);
335  };
336
337  for (const auto &Edge : CFGProfile->operands()) {
338    MDNode *E = cast<MDNode>(Edge);
339    const MCSymbol *From = GetSym(E->getOperand(0));
340    const MCSymbol *To = GetSym(E->getOperand(1));
341    // Skip null functions. This can happen if functions are dead stripped after
342    // the CGProfile pass has been run.
343    if (!From || !To)
344      continue;
345    uint64_t Count = cast<ConstantAsMetadata>(E->getOperand(2))
346                         ->getValue()
347                         ->getUniqueInteger()
348                         .getZExtValue();
349    Streamer.emitCGProfileEntry(
350        MCSymbolRefExpr::create(From, MCSymbolRefExpr::VK_None, C),
351        MCSymbolRefExpr::create(To, MCSymbolRefExpr::VK_None, C), Count);
352  }
353}
354
355MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
356    const GlobalValue *GV, const TargetMachine &TM,
357    MachineModuleInfo *MMI) const {
358  unsigned Encoding = getPersonalityEncoding();
359  if ((Encoding & 0x80) == DW_EH_PE_indirect)
360    return getContext().getOrCreateSymbol(StringRef("DW.ref.") +
361                                          TM.getSymbol(GV)->getName());
362  if ((Encoding & 0x70) == DW_EH_PE_absptr)
363    return TM.getSymbol(GV);
364  report_fatal_error("We do not support this DWARF encoding yet!");
365}
366
367void TargetLoweringObjectFileELF::emitPersonalityValue(
368    MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
369  SmallString<64> NameData("DW.ref.");
370  NameData += Sym->getName();
371  MCSymbolELF *Label =
372      cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
373  Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
374  Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
375  unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
376  MCSection *Sec = getContext().getELFNamedSection(".data", Label->getName(),
377                                                   ELF::SHT_PROGBITS, Flags, 0);
378  unsigned Size = DL.getPointerSize();
379  Streamer.SwitchSection(Sec);
380  Streamer.EmitValueToAlignment(DL.getPointerABIAlignment(0).value());
381  Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
382  const MCExpr *E = MCConstantExpr::create(Size, getContext());
383  Streamer.emitELFSize(Label, E);
384  Streamer.EmitLabel(Label);
385
386  Streamer.EmitSymbolValue(Sym, Size);
387}
388
389const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
390    const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
391    MachineModuleInfo *MMI, MCStreamer &Streamer) const {
392  if (Encoding & DW_EH_PE_indirect) {
393    MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
394
395    MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", TM);
396
397    // Add information about the stub reference to ELFMMI so that the stub
398    // gets emitted by the asmprinter.
399    MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
400    if (!StubSym.getPointer()) {
401      MCSymbol *Sym = TM.getSymbol(GV);
402      StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
403    }
404
405    return TargetLoweringObjectFile::
406      getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
407                        Encoding & ~DW_EH_PE_indirect, Streamer);
408  }
409
410  return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
411                                                           MMI, Streamer);
412}
413
414static SectionKind getELFKindForNamedSection(StringRef Name, SectionKind K) {
415  // N.B.: The defaults used in here are not the same ones used in MC.
416  // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
417  // both gas and MC will produce a section with no flags. Given
418  // section(".eh_frame") gcc will produce:
419  //
420  //   .section   .eh_frame,"a",@progbits
421
422  if (Name == getInstrProfSectionName(IPSK_covmap, Triple::ELF,
423                                      /*AddSegmentInfo=*/false))
424    return SectionKind::getMetadata();
425
426  if (Name.empty() || Name[0] != '.') return K;
427
428  // Default implementation based on some magic section names.
429  if (Name == ".bss" ||
430      Name.startswith(".bss.") ||
431      Name.startswith(".gnu.linkonce.b.") ||
432      Name.startswith(".llvm.linkonce.b.") ||
433      Name == ".sbss" ||
434      Name.startswith(".sbss.") ||
435      Name.startswith(".gnu.linkonce.sb.") ||
436      Name.startswith(".llvm.linkonce.sb."))
437    return SectionKind::getBSS();
438
439  if (Name == ".tdata" ||
440      Name.startswith(".tdata.") ||
441      Name.startswith(".gnu.linkonce.td.") ||
442      Name.startswith(".llvm.linkonce.td."))
443    return SectionKind::getThreadData();
444
445  if (Name == ".tbss" ||
446      Name.startswith(".tbss.") ||
447      Name.startswith(".gnu.linkonce.tb.") ||
448      Name.startswith(".llvm.linkonce.tb."))
449    return SectionKind::getThreadBSS();
450
451  return K;
452}
453
454static unsigned getELFSectionType(StringRef Name, SectionKind K) {
455  // Use SHT_NOTE for section whose name starts with ".note" to allow
456  // emitting ELF notes from C variable declaration.
457  // See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77609
458  if (Name.startswith(".note"))
459    return ELF::SHT_NOTE;
460
461  if (Name == ".init_array")
462    return ELF::SHT_INIT_ARRAY;
463
464  if (Name == ".fini_array")
465    return ELF::SHT_FINI_ARRAY;
466
467  if (Name == ".preinit_array")
468    return ELF::SHT_PREINIT_ARRAY;
469
470  if (K.isBSS() || K.isThreadBSS())
471    return ELF::SHT_NOBITS;
472
473  return ELF::SHT_PROGBITS;
474}
475
476static unsigned getELFSectionFlags(SectionKind K) {
477  unsigned Flags = 0;
478
479  if (!K.isMetadata())
480    Flags |= ELF::SHF_ALLOC;
481
482  if (K.isText())
483    Flags |= ELF::SHF_EXECINSTR;
484
485  if (K.isExecuteOnly())
486    Flags |= ELF::SHF_ARM_PURECODE;
487
488  if (K.isWriteable())
489    Flags |= ELF::SHF_WRITE;
490
491  if (K.isThreadLocal())
492    Flags |= ELF::SHF_TLS;
493
494  if (K.isMergeableCString() || K.isMergeableConst())
495    Flags |= ELF::SHF_MERGE;
496
497  if (K.isMergeableCString())
498    Flags |= ELF::SHF_STRINGS;
499
500  return Flags;
501}
502
503static const Comdat *getELFComdat(const GlobalValue *GV) {
504  const Comdat *C = GV->getComdat();
505  if (!C)
506    return nullptr;
507
508  if (C->getSelectionKind() != Comdat::Any)
509    report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
510                       C->getName() + "' cannot be lowered.");
511
512  return C;
513}
514
515static const MCSymbolELF *getAssociatedSymbol(const GlobalObject *GO,
516                                              const TargetMachine &TM) {
517  MDNode *MD = GO->getMetadata(LLVMContext::MD_associated);
518  if (!MD)
519    return nullptr;
520
521  const MDOperand &Op = MD->getOperand(0);
522  if (!Op.get())
523    return nullptr;
524
525  auto *VM = dyn_cast<ValueAsMetadata>(Op);
526  if (!VM)
527    report_fatal_error("MD_associated operand is not ValueAsMetadata");
528
529  auto *OtherGV = dyn_cast<GlobalValue>(VM->getValue());
530  return OtherGV ? dyn_cast<MCSymbolELF>(TM.getSymbol(OtherGV)) : nullptr;
531}
532
533static unsigned getEntrySizeForKind(SectionKind Kind) {
534  if (Kind.isMergeable1ByteCString())
535    return 1;
536  else if (Kind.isMergeable2ByteCString())
537    return 2;
538  else if (Kind.isMergeable4ByteCString())
539    return 4;
540  else if (Kind.isMergeableConst4())
541    return 4;
542  else if (Kind.isMergeableConst8())
543    return 8;
544  else if (Kind.isMergeableConst16())
545    return 16;
546  else if (Kind.isMergeableConst32())
547    return 32;
548  else {
549    // We shouldn't have mergeable C strings or mergeable constants that we
550    // didn't handle above.
551    assert(!Kind.isMergeableCString() && "unknown string width");
552    assert(!Kind.isMergeableConst() && "unknown data width");
553    return 0;
554  }
555}
556
557MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
558    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
559  StringRef SectionName = GO->getSection();
560
561  // Check if '#pragma clang section' name is applicable.
562  // Note that pragma directive overrides -ffunction-section, -fdata-section
563  // and so section name is exactly as user specified and not uniqued.
564  const GlobalVariable *GV = dyn_cast<GlobalVariable>(GO);
565  if (GV && GV->hasImplicitSection()) {
566    auto Attrs = GV->getAttributes();
567    if (Attrs.hasAttribute("bss-section") && Kind.isBSS()) {
568      SectionName = Attrs.getAttribute("bss-section").getValueAsString();
569    } else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()) {
570      SectionName = Attrs.getAttribute("rodata-section").getValueAsString();
571    } else if (Attrs.hasAttribute("relro-section") && Kind.isReadOnlyWithRel()) {
572      SectionName = Attrs.getAttribute("relro-section").getValueAsString();
573    } else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
574      SectionName = Attrs.getAttribute("data-section").getValueAsString();
575    }
576  }
577  const Function *F = dyn_cast<Function>(GO);
578  if (F && F->hasFnAttribute("implicit-section-name")) {
579    SectionName = F->getFnAttribute("implicit-section-name").getValueAsString();
580  }
581
582  // Infer section flags from the section name if we can.
583  Kind = getELFKindForNamedSection(SectionName, Kind);
584
585  StringRef Group = "";
586  unsigned Flags = getELFSectionFlags(Kind);
587  if (const Comdat *C = getELFComdat(GO)) {
588    Group = C->getName();
589    Flags |= ELF::SHF_GROUP;
590  }
591
592  // A section can have at most one associated section. Put each global with
593  // MD_associated in a unique section.
594  unsigned UniqueID = MCContext::GenericSectionID;
595  const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
596  if (AssociatedSymbol) {
597    UniqueID = NextUniqueID++;
598    Flags |= ELF::SHF_LINK_ORDER;
599  }
600
601  MCSectionELF *Section = getContext().getELFSection(
602      SectionName, getELFSectionType(SectionName, Kind), Flags,
603      getEntrySizeForKind(Kind), Group, UniqueID, AssociatedSymbol);
604  // Make sure that we did not get some other section with incompatible sh_link.
605  // This should not be possible due to UniqueID code above.
606  assert(Section->getAssociatedSymbol() == AssociatedSymbol &&
607         "Associated symbol mismatch between sections");
608  return Section;
609}
610
611/// Return the section prefix name used by options FunctionsSections and
612/// DataSections.
613static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
614  if (Kind.isText())
615    return ".text";
616  if (Kind.isReadOnly())
617    return ".rodata";
618  if (Kind.isBSS())
619    return ".bss";
620  if (Kind.isThreadData())
621    return ".tdata";
622  if (Kind.isThreadBSS())
623    return ".tbss";
624  if (Kind.isData())
625    return ".data";
626  assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
627  return ".data.rel.ro";
628}
629
630static MCSectionELF *selectELFSectionForGlobal(
631    MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
632    const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
633    unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol) {
634
635  StringRef Group = "";
636  if (const Comdat *C = getELFComdat(GO)) {
637    Flags |= ELF::SHF_GROUP;
638    Group = C->getName();
639  }
640
641  // Get the section entry size based on the kind.
642  unsigned EntrySize = getEntrySizeForKind(Kind);
643
644  SmallString<128> Name;
645  if (Kind.isMergeableCString()) {
646    // We also need alignment here.
647    // FIXME: this is getting the alignment of the character, not the
648    // alignment of the global!
649    unsigned Align = GO->getParent()->getDataLayout().getPreferredAlignment(
650        cast<GlobalVariable>(GO));
651
652    std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
653    Name = SizeSpec + utostr(Align);
654  } else if (Kind.isMergeableConst()) {
655    Name = ".rodata.cst";
656    Name += utostr(EntrySize);
657  } else {
658    Name = getSectionPrefixForGlobal(Kind);
659  }
660
661  if (const auto *F = dyn_cast<Function>(GO)) {
662    const auto &OptionalPrefix = F->getSectionPrefix();
663    if (OptionalPrefix)
664      Name += *OptionalPrefix;
665  }
666
667  unsigned UniqueID = MCContext::GenericSectionID;
668  if (EmitUniqueSection) {
669    if (TM.getUniqueSectionNames()) {
670      Name.push_back('.');
671      TM.getNameWithPrefix(Name, GO, Mang, true /*MayAlwaysUsePrivate*/);
672    } else {
673      UniqueID = *NextUniqueID;
674      (*NextUniqueID)++;
675    }
676  }
677  // Use 0 as the unique ID for execute-only text.
678  if (Kind.isExecuteOnly())
679    UniqueID = 0;
680  return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags,
681                           EntrySize, Group, UniqueID, AssociatedSymbol);
682}
683
684MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
685    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
686  unsigned Flags = getELFSectionFlags(Kind);
687
688  // If we have -ffunction-section or -fdata-section then we should emit the
689  // global value to a uniqued section specifically for it.
690  bool EmitUniqueSection = false;
691  if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
692    if (Kind.isText())
693      EmitUniqueSection = TM.getFunctionSections();
694    else
695      EmitUniqueSection = TM.getDataSections();
696  }
697  EmitUniqueSection |= GO->hasComdat();
698
699  const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
700  if (AssociatedSymbol) {
701    EmitUniqueSection = true;
702    Flags |= ELF::SHF_LINK_ORDER;
703  }
704
705  MCSectionELF *Section = selectELFSectionForGlobal(
706      getContext(), GO, Kind, getMangler(), TM, EmitUniqueSection, Flags,
707      &NextUniqueID, AssociatedSymbol);
708  assert(Section->getAssociatedSymbol() == AssociatedSymbol);
709  return Section;
710}
711
712MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
713    const Function &F, const TargetMachine &TM) const {
714  // If the function can be removed, produce a unique section so that
715  // the table doesn't prevent the removal.
716  const Comdat *C = F.getComdat();
717  bool EmitUniqueSection = TM.getFunctionSections() || C;
718  if (!EmitUniqueSection)
719    return ReadOnlySection;
720
721  return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
722                                   getMangler(), TM, EmitUniqueSection,
723                                   ELF::SHF_ALLOC, &NextUniqueID,
724                                   /* AssociatedSymbol */ nullptr);
725}
726
727bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
728    bool UsesLabelDifference, const Function &F) const {
729  // We can always create relative relocations, so use another section
730  // that can be marked non-executable.
731  return false;
732}
733
734/// Given a mergeable constant with the specified size and relocation
735/// information, return a section that it should be placed in.
736MCSection *TargetLoweringObjectFileELF::getSectionForConstant(
737    const DataLayout &DL, SectionKind Kind, const Constant *C,
738    unsigned &Align) const {
739  if (Kind.isMergeableConst4() && MergeableConst4Section)
740    return MergeableConst4Section;
741  if (Kind.isMergeableConst8() && MergeableConst8Section)
742    return MergeableConst8Section;
743  if (Kind.isMergeableConst16() && MergeableConst16Section)
744    return MergeableConst16Section;
745  if (Kind.isMergeableConst32() && MergeableConst32Section)
746    return MergeableConst32Section;
747  if (Kind.isReadOnly())
748    return ReadOnlySection;
749
750  assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
751  return DataRelROSection;
752}
753
754static MCSectionELF *getStaticStructorSection(MCContext &Ctx, bool UseInitArray,
755                                              bool IsCtor, unsigned Priority,
756                                              const MCSymbol *KeySym) {
757  std::string Name;
758  unsigned Type;
759  unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
760  StringRef COMDAT = KeySym ? KeySym->getName() : "";
761
762  if (KeySym)
763    Flags |= ELF::SHF_GROUP;
764
765  if (UseInitArray) {
766    if (IsCtor) {
767      Type = ELF::SHT_INIT_ARRAY;
768      Name = ".init_array";
769    } else {
770      Type = ELF::SHT_FINI_ARRAY;
771      Name = ".fini_array";
772    }
773    if (Priority != 65535) {
774      Name += '.';
775      Name += utostr(Priority);
776    }
777  } else {
778    // The default scheme is .ctor / .dtor, so we have to invert the priority
779    // numbering.
780    if (IsCtor)
781      Name = ".ctors";
782    else
783      Name = ".dtors";
784    if (Priority != 65535)
785      raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
786    Type = ELF::SHT_PROGBITS;
787  }
788
789  return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
790}
791
792MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
793    unsigned Priority, const MCSymbol *KeySym) const {
794  return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
795                                  KeySym);
796}
797
798MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
799    unsigned Priority, const MCSymbol *KeySym) const {
800  return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
801                                  KeySym);
802}
803
804const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
805    const GlobalValue *LHS, const GlobalValue *RHS,
806    const TargetMachine &TM) const {
807  // We may only use a PLT-relative relocation to refer to unnamed_addr
808  // functions.
809  if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
810    return nullptr;
811
812  // Basic sanity checks.
813  if (LHS->getType()->getPointerAddressSpace() != 0 ||
814      RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
815      RHS->isThreadLocal())
816    return nullptr;
817
818  return MCBinaryExpr::createSub(
819      MCSymbolRefExpr::create(TM.getSymbol(LHS), PLTRelativeVariantKind,
820                              getContext()),
821      MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
822}
823
824MCSection *TargetLoweringObjectFileELF::getSectionForCommandLines() const {
825  // Use ".GCC.command.line" since this feature is to support clang's
826  // -frecord-gcc-switches which in turn attempts to mimic GCC's switch of the
827  // same name.
828  return getContext().getELFSection(".GCC.command.line", ELF::SHT_PROGBITS,
829                                    ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
830}
831
832void
833TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
834  UseInitArray = UseInitArray_;
835  MCContext &Ctx = getContext();
836  if (!UseInitArray) {
837    StaticCtorSection = Ctx.getELFSection(".ctors", ELF::SHT_PROGBITS,
838                                          ELF::SHF_ALLOC | ELF::SHF_WRITE);
839
840    StaticDtorSection = Ctx.getELFSection(".dtors", ELF::SHT_PROGBITS,
841                                          ELF::SHF_ALLOC | ELF::SHF_WRITE);
842    return;
843  }
844
845  StaticCtorSection = Ctx.getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
846                                        ELF::SHF_WRITE | ELF::SHF_ALLOC);
847  StaticDtorSection = Ctx.getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
848                                        ELF::SHF_WRITE | ELF::SHF_ALLOC);
849}
850
851//===----------------------------------------------------------------------===//
852//                                 MachO
853//===----------------------------------------------------------------------===//
854
855TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
856  : TargetLoweringObjectFile() {
857  SupportIndirectSymViaGOTPCRel = true;
858}
859
860void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
861                                               const TargetMachine &TM) {
862  TargetLoweringObjectFile::Initialize(Ctx, TM);
863  if (TM.getRelocationModel() == Reloc::Static) {
864    StaticCtorSection = Ctx.getMachOSection("__TEXT", "__constructor", 0,
865                                            SectionKind::getData());
866    StaticDtorSection = Ctx.getMachOSection("__TEXT", "__destructor", 0,
867                                            SectionKind::getData());
868  } else {
869    StaticCtorSection = Ctx.getMachOSection("__DATA", "__mod_init_func",
870                                            MachO::S_MOD_INIT_FUNC_POINTERS,
871                                            SectionKind::getData());
872    StaticDtorSection = Ctx.getMachOSection("__DATA", "__mod_term_func",
873                                            MachO::S_MOD_TERM_FUNC_POINTERS,
874                                            SectionKind::getData());
875  }
876
877  PersonalityEncoding =
878      dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
879  LSDAEncoding = dwarf::DW_EH_PE_pcrel;
880  TTypeEncoding =
881      dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
882}
883
884void TargetLoweringObjectFileMachO::emitModuleMetadata(MCStreamer &Streamer,
885                                                       Module &M) const {
886  // Emit the linker options if present.
887  if (auto *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
888    for (const auto *Option : LinkerOptions->operands()) {
889      SmallVector<std::string, 4> StrOptions;
890      for (const auto &Piece : cast<MDNode>(Option)->operands())
891        StrOptions.push_back(cast<MDString>(Piece)->getString());
892      Streamer.EmitLinkerOptions(StrOptions);
893    }
894  }
895
896  unsigned VersionVal = 0;
897  unsigned ImageInfoFlags = 0;
898  StringRef SectionVal;
899
900  GetObjCImageInfo(M, VersionVal, ImageInfoFlags, SectionVal);
901
902  // The section is mandatory. If we don't have it, then we don't have GC info.
903  if (SectionVal.empty())
904    return;
905
906  StringRef Segment, Section;
907  unsigned TAA = 0, StubSize = 0;
908  bool TAAParsed;
909  std::string ErrorCode =
910    MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
911                                          TAA, TAAParsed, StubSize);
912  if (!ErrorCode.empty())
913    // If invalid, report the error with report_fatal_error.
914    report_fatal_error("Invalid section specifier '" + Section + "': " +
915                       ErrorCode + ".");
916
917  // Get the section.
918  MCSectionMachO *S = getContext().getMachOSection(
919      Segment, Section, TAA, StubSize, SectionKind::getData());
920  Streamer.SwitchSection(S);
921  Streamer.EmitLabel(getContext().
922                     getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
923  Streamer.EmitIntValue(VersionVal, 4);
924  Streamer.EmitIntValue(ImageInfoFlags, 4);
925  Streamer.AddBlankLine();
926}
927
928static void checkMachOComdat(const GlobalValue *GV) {
929  const Comdat *C = GV->getComdat();
930  if (!C)
931    return;
932
933  report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
934                     "' cannot be lowered.");
935}
936
937MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
938    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
939  // Parse the section specifier and create it if valid.
940  StringRef Segment, Section;
941  unsigned TAA = 0, StubSize = 0;
942  bool TAAParsed;
943
944  checkMachOComdat(GO);
945
946  std::string ErrorCode =
947    MCSectionMachO::ParseSectionSpecifier(GO->getSection(), Segment, Section,
948                                          TAA, TAAParsed, StubSize);
949  if (!ErrorCode.empty()) {
950    // If invalid, report the error with report_fatal_error.
951    report_fatal_error("Global variable '" + GO->getName() +
952                       "' has an invalid section specifier '" +
953                       GO->getSection() + "': " + ErrorCode + ".");
954  }
955
956  // Get the section.
957  MCSectionMachO *S =
958      getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
959
960  // If TAA wasn't set by ParseSectionSpecifier() above,
961  // use the value returned by getMachOSection() as a default.
962  if (!TAAParsed)
963    TAA = S->getTypeAndAttributes();
964
965  // Okay, now that we got the section, verify that the TAA & StubSize agree.
966  // If the user declared multiple globals with different section flags, we need
967  // to reject it here.
968  if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
969    // If invalid, report the error with report_fatal_error.
970    report_fatal_error("Global variable '" + GO->getName() +
971                       "' section type or attributes does not match previous"
972                       " section specifier");
973  }
974
975  return S;
976}
977
978MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
979    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
980  checkMachOComdat(GO);
981
982  // Handle thread local data.
983  if (Kind.isThreadBSS()) return TLSBSSSection;
984  if (Kind.isThreadData()) return TLSDataSection;
985
986  if (Kind.isText())
987    return GO->isWeakForLinker() ? TextCoalSection : TextSection;
988
989  // If this is weak/linkonce, put this in a coalescable section, either in text
990  // or data depending on if it is writable.
991  if (GO->isWeakForLinker()) {
992    if (Kind.isReadOnly())
993      return ConstTextCoalSection;
994    if (Kind.isReadOnlyWithRel())
995      return ConstDataCoalSection;
996    return DataCoalSection;
997  }
998
999  // FIXME: Alignment check should be handled by section classifier.
1000  if (Kind.isMergeable1ByteCString() &&
1001      GO->getParent()->getDataLayout().getPreferredAlignment(
1002          cast<GlobalVariable>(GO)) < 32)
1003    return CStringSection;
1004
1005  // Do not put 16-bit arrays in the UString section if they have an
1006  // externally visible label, this runs into issues with certain linker
1007  // versions.
1008  if (Kind.isMergeable2ByteCString() && !GO->hasExternalLinkage() &&
1009      GO->getParent()->getDataLayout().getPreferredAlignment(
1010          cast<GlobalVariable>(GO)) < 32)
1011    return UStringSection;
1012
1013  // With MachO only variables whose corresponding symbol starts with 'l' or
1014  // 'L' can be merged, so we only try merging GVs with private linkage.
1015  if (GO->hasPrivateLinkage() && Kind.isMergeableConst()) {
1016    if (Kind.isMergeableConst4())
1017      return FourByteConstantSection;
1018    if (Kind.isMergeableConst8())
1019      return EightByteConstantSection;
1020    if (Kind.isMergeableConst16())
1021      return SixteenByteConstantSection;
1022  }
1023
1024  // Otherwise, if it is readonly, but not something we can specially optimize,
1025  // just drop it in .const.
1026  if (Kind.isReadOnly())
1027    return ReadOnlySection;
1028
1029  // If this is marked const, put it into a const section.  But if the dynamic
1030  // linker needs to write to it, put it in the data segment.
1031  if (Kind.isReadOnlyWithRel())
1032    return ConstDataSection;
1033
1034  // Put zero initialized globals with strong external linkage in the
1035  // DATA, __common section with the .zerofill directive.
1036  if (Kind.isBSSExtern())
1037    return DataCommonSection;
1038
1039  // Put zero initialized globals with local linkage in __DATA,__bss directive
1040  // with the .zerofill directive (aka .lcomm).
1041  if (Kind.isBSSLocal())
1042    return DataBSSSection;
1043
1044  // Otherwise, just drop the variable in the normal data section.
1045  return DataSection;
1046}
1047
1048MCSection *TargetLoweringObjectFileMachO::getSectionForConstant(
1049    const DataLayout &DL, SectionKind Kind, const Constant *C,
1050    unsigned &Align) const {
1051  // If this constant requires a relocation, we have to put it in the data
1052  // segment, not in the text segment.
1053  if (Kind.isData() || Kind.isReadOnlyWithRel())
1054    return ConstDataSection;
1055
1056  if (Kind.isMergeableConst4())
1057    return FourByteConstantSection;
1058  if (Kind.isMergeableConst8())
1059    return EightByteConstantSection;
1060  if (Kind.isMergeableConst16())
1061    return SixteenByteConstantSection;
1062  return ReadOnlySection;  // .const
1063}
1064
1065const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
1066    const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
1067    MachineModuleInfo *MMI, MCStreamer &Streamer) const {
1068  // The mach-o version of this method defaults to returning a stub reference.
1069
1070  if (Encoding & DW_EH_PE_indirect) {
1071    MachineModuleInfoMachO &MachOMMI =
1072      MMI->getObjFileInfo<MachineModuleInfoMachO>();
1073
1074    MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
1075
1076    // Add information about the stub reference to MachOMMI so that the stub
1077    // gets emitted by the asmprinter.
1078    MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
1079    if (!StubSym.getPointer()) {
1080      MCSymbol *Sym = TM.getSymbol(GV);
1081      StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
1082    }
1083
1084    return TargetLoweringObjectFile::
1085      getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
1086                        Encoding & ~DW_EH_PE_indirect, Streamer);
1087  }
1088
1089  return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
1090                                                           MMI, Streamer);
1091}
1092
1093MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
1094    const GlobalValue *GV, const TargetMachine &TM,
1095    MachineModuleInfo *MMI) const {
1096  // The mach-o version of this method defaults to returning a stub reference.
1097  MachineModuleInfoMachO &MachOMMI =
1098    MMI->getObjFileInfo<MachineModuleInfoMachO>();
1099
1100  MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
1101
1102  // Add information about the stub reference to MachOMMI so that the stub
1103  // gets emitted by the asmprinter.
1104  MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
1105  if (!StubSym.getPointer()) {
1106    MCSymbol *Sym = TM.getSymbol(GV);
1107    StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
1108  }
1109
1110  return SSym;
1111}
1112
1113const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
1114    const GlobalValue *GV, const MCSymbol *Sym, const MCValue &MV,
1115    int64_t Offset, MachineModuleInfo *MMI, MCStreamer &Streamer) const {
1116  // Although MachO 32-bit targets do not explicitly have a GOTPCREL relocation
1117  // as 64-bit do, we replace the GOT equivalent by accessing the final symbol
1118  // through a non_lazy_ptr stub instead. One advantage is that it allows the
1119  // computation of deltas to final external symbols. Example:
1120  //
1121  //    _extgotequiv:
1122  //       .long   _extfoo
1123  //
1124  //    _delta:
1125  //       .long   _extgotequiv-_delta
1126  //
1127  // is transformed to:
1128  //
1129  //    _delta:
1130  //       .long   L_extfoo$non_lazy_ptr-(_delta+0)
1131  //
1132  //       .section        __IMPORT,__pointers,non_lazy_symbol_pointers
1133  //    L_extfoo$non_lazy_ptr:
1134  //       .indirect_symbol        _extfoo
1135  //       .long   0
1136  //
1137  // The indirect symbol table (and sections of non_lazy_symbol_pointers type)
1138  // may point to both local (same translation unit) and global (other
1139  // translation units) symbols. Example:
1140  //
1141  // .section __DATA,__pointers,non_lazy_symbol_pointers
1142  // L1:
1143  //    .indirect_symbol _myGlobal
1144  //    .long 0
1145  // L2:
1146  //    .indirect_symbol _myLocal
1147  //    .long _myLocal
1148  //
1149  // If the symbol is local, instead of the symbol's index, the assembler
1150  // places the constant INDIRECT_SYMBOL_LOCAL into the indirect symbol table.
1151  // Then the linker will notice the constant in the table and will look at the
1152  // content of the symbol.
1153  MachineModuleInfoMachO &MachOMMI =
1154    MMI->getObjFileInfo<MachineModuleInfoMachO>();
1155  MCContext &Ctx = getContext();
1156
1157  // The offset must consider the original displacement from the base symbol
1158  // since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
1159  Offset = -MV.getConstant();
1160  const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
1161
1162  // Access the final symbol via sym$non_lazy_ptr and generate the appropriated
1163  // non_lazy_ptr stubs.
1164  SmallString<128> Name;
1165  StringRef Suffix = "$non_lazy_ptr";
1166  Name += MMI->getModule()->getDataLayout().getPrivateGlobalPrefix();
1167  Name += Sym->getName();
1168  Name += Suffix;
1169  MCSymbol *Stub = Ctx.getOrCreateSymbol(Name);
1170
1171  MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
1172
1173  if (!StubSym.getPointer())
1174    StubSym = MachineModuleInfoImpl::StubValueTy(const_cast<MCSymbol *>(Sym),
1175                                                 !GV->hasLocalLinkage());
1176
1177  const MCExpr *BSymExpr =
1178    MCSymbolRefExpr::create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
1179  const MCExpr *LHS =
1180    MCSymbolRefExpr::create(Stub, MCSymbolRefExpr::VK_None, Ctx);
1181
1182  if (!Offset)
1183    return MCBinaryExpr::createSub(LHS, BSymExpr, Ctx);
1184
1185  const MCExpr *RHS =
1186    MCBinaryExpr::createAdd(BSymExpr, MCConstantExpr::create(Offset, Ctx), Ctx);
1187  return MCBinaryExpr::createSub(LHS, RHS, Ctx);
1188}
1189
1190static bool canUsePrivateLabel(const MCAsmInfo &AsmInfo,
1191                               const MCSection &Section) {
1192  if (!AsmInfo.isSectionAtomizableBySymbols(Section))
1193    return true;
1194
1195  // If it is not dead stripped, it is safe to use private labels.
1196  const MCSectionMachO &SMO = cast<MCSectionMachO>(Section);
1197  if (SMO.hasAttribute(MachO::S_ATTR_NO_DEAD_STRIP))
1198    return true;
1199
1200  return false;
1201}
1202
1203void TargetLoweringObjectFileMachO::getNameWithPrefix(
1204    SmallVectorImpl<char> &OutName, const GlobalValue *GV,
1205    const TargetMachine &TM) const {
1206  bool CannotUsePrivateLabel = true;
1207  if (auto *GO = GV->getBaseObject()) {
1208    SectionKind GOKind = TargetLoweringObjectFile::getKindForGlobal(GO, TM);
1209    const MCSection *TheSection = SectionForGlobal(GO, GOKind, TM);
1210    CannotUsePrivateLabel =
1211        !canUsePrivateLabel(*TM.getMCAsmInfo(), *TheSection);
1212  }
1213  getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1214}
1215
1216//===----------------------------------------------------------------------===//
1217//                                  COFF
1218//===----------------------------------------------------------------------===//
1219
1220static unsigned
1221getCOFFSectionFlags(SectionKind K, const TargetMachine &TM) {
1222  unsigned Flags = 0;
1223  bool isThumb = TM.getTargetTriple().getArch() == Triple::thumb;
1224
1225  if (K.isMetadata())
1226    Flags |=
1227      COFF::IMAGE_SCN_MEM_DISCARDABLE;
1228  else if (K.isText())
1229    Flags |=
1230      COFF::IMAGE_SCN_MEM_EXECUTE |
1231      COFF::IMAGE_SCN_MEM_READ |
1232      COFF::IMAGE_SCN_CNT_CODE |
1233      (isThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0);
1234  else if (K.isBSS())
1235    Flags |=
1236      COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
1237      COFF::IMAGE_SCN_MEM_READ |
1238      COFF::IMAGE_SCN_MEM_WRITE;
1239  else if (K.isThreadLocal())
1240    Flags |=
1241      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1242      COFF::IMAGE_SCN_MEM_READ |
1243      COFF::IMAGE_SCN_MEM_WRITE;
1244  else if (K.isReadOnly() || K.isReadOnlyWithRel())
1245    Flags |=
1246      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1247      COFF::IMAGE_SCN_MEM_READ;
1248  else if (K.isWriteable())
1249    Flags |=
1250      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1251      COFF::IMAGE_SCN_MEM_READ |
1252      COFF::IMAGE_SCN_MEM_WRITE;
1253
1254  return Flags;
1255}
1256
1257static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
1258  const Comdat *C = GV->getComdat();
1259  assert(C && "expected GV to have a Comdat!");
1260
1261  StringRef ComdatGVName = C->getName();
1262  const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
1263  if (!ComdatGV)
1264    report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
1265                       "' does not exist.");
1266
1267  if (ComdatGV->getComdat() != C)
1268    report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
1269                       "' is not a key for its COMDAT.");
1270
1271  return ComdatGV;
1272}
1273
1274static int getSelectionForCOFF(const GlobalValue *GV) {
1275  if (const Comdat *C = GV->getComdat()) {
1276    const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
1277    if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
1278      ComdatKey = GA->getBaseObject();
1279    if (ComdatKey == GV) {
1280      switch (C->getSelectionKind()) {
1281      case Comdat::Any:
1282        return COFF::IMAGE_COMDAT_SELECT_ANY;
1283      case Comdat::ExactMatch:
1284        return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
1285      case Comdat::Largest:
1286        return COFF::IMAGE_COMDAT_SELECT_LARGEST;
1287      case Comdat::NoDuplicates:
1288        return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1289      case Comdat::SameSize:
1290        return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
1291      }
1292    } else {
1293      return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
1294    }
1295  }
1296  return 0;
1297}
1298
1299MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
1300    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1301  int Selection = 0;
1302  unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1303  StringRef Name = GO->getSection();
1304  StringRef COMDATSymName = "";
1305  if (GO->hasComdat()) {
1306    Selection = getSelectionForCOFF(GO);
1307    const GlobalValue *ComdatGV;
1308    if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
1309      ComdatGV = getComdatGVForCOFF(GO);
1310    else
1311      ComdatGV = GO;
1312
1313    if (!ComdatGV->hasPrivateLinkage()) {
1314      MCSymbol *Sym = TM.getSymbol(ComdatGV);
1315      COMDATSymName = Sym->getName();
1316      Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1317    } else {
1318      Selection = 0;
1319    }
1320  }
1321
1322  return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
1323                                     Selection);
1324}
1325
1326static StringRef getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
1327  if (Kind.isText())
1328    return ".text";
1329  if (Kind.isBSS())
1330    return ".bss";
1331  if (Kind.isThreadLocal())
1332    return ".tls$";
1333  if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1334    return ".rdata";
1335  return ".data";
1336}
1337
1338MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
1339    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1340  // If we have -ffunction-sections then we should emit the global value to a
1341  // uniqued section specifically for it.
1342  bool EmitUniquedSection;
1343  if (Kind.isText())
1344    EmitUniquedSection = TM.getFunctionSections();
1345  else
1346    EmitUniquedSection = TM.getDataSections();
1347
1348  if ((EmitUniquedSection && !Kind.isCommon()) || GO->hasComdat()) {
1349    SmallString<256> Name = getCOFFSectionNameForUniqueGlobal(Kind);
1350
1351    unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1352
1353    Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1354    int Selection = getSelectionForCOFF(GO);
1355    if (!Selection)
1356      Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1357    const GlobalValue *ComdatGV;
1358    if (GO->hasComdat())
1359      ComdatGV = getComdatGVForCOFF(GO);
1360    else
1361      ComdatGV = GO;
1362
1363    unsigned UniqueID = MCContext::GenericSectionID;
1364    if (EmitUniquedSection)
1365      UniqueID = NextUniqueID++;
1366
1367    if (!ComdatGV->hasPrivateLinkage()) {
1368      MCSymbol *Sym = TM.getSymbol(ComdatGV);
1369      StringRef COMDATSymName = Sym->getName();
1370
1371      // Append "$symbol" to the section name *before* IR-level mangling is
1372      // applied when targetting mingw. This is what GCC does, and the ld.bfd
1373      // COFF linker will not properly handle comdats otherwise.
1374      if (getTargetTriple().isWindowsGNUEnvironment())
1375        raw_svector_ostream(Name) << '$' << ComdatGV->getName();
1376
1377      return getContext().getCOFFSection(Name, Characteristics, Kind,
1378                                         COMDATSymName, Selection, UniqueID);
1379    } else {
1380      SmallString<256> TmpData;
1381      getMangler().getNameWithPrefix(TmpData, GO, /*CannotUsePrivateLabel=*/true);
1382      return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
1383                                         Selection, UniqueID);
1384    }
1385  }
1386
1387  if (Kind.isText())
1388    return TextSection;
1389
1390  if (Kind.isThreadLocal())
1391    return TLSDataSection;
1392
1393  if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1394    return ReadOnlySection;
1395
1396  // Note: we claim that common symbols are put in BSSSection, but they are
1397  // really emitted with the magic .comm directive, which creates a symbol table
1398  // entry but not a section.
1399  if (Kind.isBSS() || Kind.isCommon())
1400    return BSSSection;
1401
1402  return DataSection;
1403}
1404
1405void TargetLoweringObjectFileCOFF::getNameWithPrefix(
1406    SmallVectorImpl<char> &OutName, const GlobalValue *GV,
1407    const TargetMachine &TM) const {
1408  bool CannotUsePrivateLabel = false;
1409  if (GV->hasPrivateLinkage() &&
1410      ((isa<Function>(GV) && TM.getFunctionSections()) ||
1411       (isa<GlobalVariable>(GV) && TM.getDataSections())))
1412    CannotUsePrivateLabel = true;
1413
1414  getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1415}
1416
1417MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
1418    const Function &F, const TargetMachine &TM) const {
1419  // If the function can be removed, produce a unique section so that
1420  // the table doesn't prevent the removal.
1421  const Comdat *C = F.getComdat();
1422  bool EmitUniqueSection = TM.getFunctionSections() || C;
1423  if (!EmitUniqueSection)
1424    return ReadOnlySection;
1425
1426  // FIXME: we should produce a symbol for F instead.
1427  if (F.hasPrivateLinkage())
1428    return ReadOnlySection;
1429
1430  MCSymbol *Sym = TM.getSymbol(&F);
1431  StringRef COMDATSymName = Sym->getName();
1432
1433  SectionKind Kind = SectionKind::getReadOnly();
1434  StringRef SecName = getCOFFSectionNameForUniqueGlobal(Kind);
1435  unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1436  Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1437  unsigned UniqueID = NextUniqueID++;
1438
1439  return getContext().getCOFFSection(
1440      SecName, Characteristics, Kind, COMDATSymName,
1441      COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
1442}
1443
1444void TargetLoweringObjectFileCOFF::emitModuleMetadata(MCStreamer &Streamer,
1445                                                      Module &M) const {
1446  if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
1447    // Emit the linker options to the linker .drectve section.  According to the
1448    // spec, this section is a space-separated string containing flags for
1449    // linker.
1450    MCSection *Sec = getDrectveSection();
1451    Streamer.SwitchSection(Sec);
1452    for (const auto *Option : LinkerOptions->operands()) {
1453      for (const auto &Piece : cast<MDNode>(Option)->operands()) {
1454        // Lead with a space for consistency with our dllexport implementation.
1455        std::string Directive(" ");
1456        Directive.append(cast<MDString>(Piece)->getString());
1457        Streamer.EmitBytes(Directive);
1458      }
1459    }
1460  }
1461
1462  unsigned Version = 0;
1463  unsigned Flags = 0;
1464  StringRef Section;
1465
1466  GetObjCImageInfo(M, Version, Flags, Section);
1467  if (Section.empty())
1468    return;
1469
1470  auto &C = getContext();
1471  auto *S = C.getCOFFSection(
1472      Section, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
1473      SectionKind::getReadOnly());
1474  Streamer.SwitchSection(S);
1475  Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
1476  Streamer.EmitIntValue(Version, 4);
1477  Streamer.EmitIntValue(Flags, 4);
1478  Streamer.AddBlankLine();
1479}
1480
1481void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
1482                                              const TargetMachine &TM) {
1483  TargetLoweringObjectFile::Initialize(Ctx, TM);
1484  const Triple &T = TM.getTargetTriple();
1485  if (T.isWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
1486    StaticCtorSection =
1487        Ctx.getCOFFSection(".CRT$XCU", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1488                                           COFF::IMAGE_SCN_MEM_READ,
1489                           SectionKind::getReadOnly());
1490    StaticDtorSection =
1491        Ctx.getCOFFSection(".CRT$XTX", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1492                                           COFF::IMAGE_SCN_MEM_READ,
1493                           SectionKind::getReadOnly());
1494  } else {
1495    StaticCtorSection = Ctx.getCOFFSection(
1496        ".ctors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1497                      COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1498        SectionKind::getData());
1499    StaticDtorSection = Ctx.getCOFFSection(
1500        ".dtors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1501                      COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1502        SectionKind::getData());
1503  }
1504}
1505
1506static MCSectionCOFF *getCOFFStaticStructorSection(MCContext &Ctx,
1507                                                   const Triple &T, bool IsCtor,
1508                                                   unsigned Priority,
1509                                                   const MCSymbol *KeySym,
1510                                                   MCSectionCOFF *Default) {
1511  if (T.isWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
1512    // If the priority is the default, use .CRT$XCU, possibly associative.
1513    if (Priority == 65535)
1514      return Ctx.getAssociativeCOFFSection(Default, KeySym, 0);
1515
1516    // Otherwise, we need to compute a new section name. Low priorities should
1517    // run earlier. The linker will sort sections ASCII-betically, and we need a
1518    // string that sorts between .CRT$XCA and .CRT$XCU. In the general case, we
1519    // make a name like ".CRT$XCT12345", since that runs before .CRT$XCU. Really
1520    // low priorities need to sort before 'L', since the CRT uses that
1521    // internally, so we use ".CRT$XCA00001" for them.
1522    SmallString<24> Name;
1523    raw_svector_ostream OS(Name);
1524    OS << ".CRT$X" << (IsCtor ? "C" : "T") <<
1525        (Priority < 200 ? 'A' : 'T') << format("%05u", Priority);
1526    MCSectionCOFF *Sec = Ctx.getCOFFSection(
1527        Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
1528        SectionKind::getReadOnly());
1529    return Ctx.getAssociativeCOFFSection(Sec, KeySym, 0);
1530  }
1531
1532  std::string Name = IsCtor ? ".ctors" : ".dtors";
1533  if (Priority != 65535)
1534    raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
1535
1536  return Ctx.getAssociativeCOFFSection(
1537      Ctx.getCOFFSection(Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1538                                   COFF::IMAGE_SCN_MEM_READ |
1539                                   COFF::IMAGE_SCN_MEM_WRITE,
1540                         SectionKind::getData()),
1541      KeySym, 0);
1542}
1543
1544MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
1545    unsigned Priority, const MCSymbol *KeySym) const {
1546  return getCOFFStaticStructorSection(getContext(), getTargetTriple(), true,
1547                                      Priority, KeySym,
1548                                      cast<MCSectionCOFF>(StaticCtorSection));
1549}
1550
1551MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
1552    unsigned Priority, const MCSymbol *KeySym) const {
1553  return getCOFFStaticStructorSection(getContext(), getTargetTriple(), false,
1554                                      Priority, KeySym,
1555                                      cast<MCSectionCOFF>(StaticDtorSection));
1556}
1557
1558void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
1559    raw_ostream &OS, const GlobalValue *GV) const {
1560  emitLinkerFlagsForGlobalCOFF(OS, GV, getTargetTriple(), getMangler());
1561}
1562
1563void TargetLoweringObjectFileCOFF::emitLinkerFlagsForUsed(
1564    raw_ostream &OS, const GlobalValue *GV) const {
1565  emitLinkerFlagsForUsedCOFF(OS, GV, getTargetTriple(), getMangler());
1566}
1567
1568const MCExpr *TargetLoweringObjectFileCOFF::lowerRelativeReference(
1569    const GlobalValue *LHS, const GlobalValue *RHS,
1570    const TargetMachine &TM) const {
1571  const Triple &T = TM.getTargetTriple();
1572  if (T.isOSCygMing())
1573    return nullptr;
1574
1575  // Our symbols should exist in address space zero, cowardly no-op if
1576  // otherwise.
1577  if (LHS->getType()->getPointerAddressSpace() != 0 ||
1578      RHS->getType()->getPointerAddressSpace() != 0)
1579    return nullptr;
1580
1581  // Both ptrtoint instructions must wrap global objects:
1582  // - Only global variables are eligible for image relative relocations.
1583  // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
1584  // We expect __ImageBase to be a global variable without a section, externally
1585  // defined.
1586  //
1587  // It should look something like this: @__ImageBase = external constant i8
1588  if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) ||
1589      LHS->isThreadLocal() || RHS->isThreadLocal() ||
1590      RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() ||
1591      cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection())
1592    return nullptr;
1593
1594  return MCSymbolRefExpr::create(TM.getSymbol(LHS),
1595                                 MCSymbolRefExpr::VK_COFF_IMGREL32,
1596                                 getContext());
1597}
1598
1599static std::string APIntToHexString(const APInt &AI) {
1600  unsigned Width = (AI.getBitWidth() / 8) * 2;
1601  std::string HexString = AI.toString(16, /*Signed=*/false);
1602  transform(HexString.begin(), HexString.end(), HexString.begin(), tolower);
1603  unsigned Size = HexString.size();
1604  assert(Width >= Size && "hex string is too large!");
1605  HexString.insert(HexString.begin(), Width - Size, '0');
1606
1607  return HexString;
1608}
1609
1610static std::string scalarConstantToHexString(const Constant *C) {
1611  Type *Ty = C->getType();
1612  if (isa<UndefValue>(C)) {
1613    return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits()));
1614  } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) {
1615    return APIntToHexString(CFP->getValueAPF().bitcastToAPInt());
1616  } else if (const auto *CI = dyn_cast<ConstantInt>(C)) {
1617    return APIntToHexString(CI->getValue());
1618  } else {
1619    unsigned NumElements;
1620    if (isa<VectorType>(Ty))
1621      NumElements = Ty->getVectorNumElements();
1622    else
1623      NumElements = Ty->getArrayNumElements();
1624    std::string HexString;
1625    for (int I = NumElements - 1, E = -1; I != E; --I)
1626      HexString += scalarConstantToHexString(C->getAggregateElement(I));
1627    return HexString;
1628  }
1629}
1630
1631MCSection *TargetLoweringObjectFileCOFF::getSectionForConstant(
1632    const DataLayout &DL, SectionKind Kind, const Constant *C,
1633    unsigned &Align) const {
1634  if (Kind.isMergeableConst() && C &&
1635      getContext().getAsmInfo()->hasCOFFComdatConstants()) {
1636    // This creates comdat sections with the given symbol name, but unless
1637    // AsmPrinter::GetCPISymbol actually makes the symbol global, the symbol
1638    // will be created with a null storage class, which makes GNU binutils
1639    // error out.
1640    const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1641                                     COFF::IMAGE_SCN_MEM_READ |
1642                                     COFF::IMAGE_SCN_LNK_COMDAT;
1643    std::string COMDATSymName;
1644    if (Kind.isMergeableConst4()) {
1645      if (Align <= 4) {
1646        COMDATSymName = "__real@" + scalarConstantToHexString(C);
1647        Align = 4;
1648      }
1649    } else if (Kind.isMergeableConst8()) {
1650      if (Align <= 8) {
1651        COMDATSymName = "__real@" + scalarConstantToHexString(C);
1652        Align = 8;
1653      }
1654    } else if (Kind.isMergeableConst16()) {
1655      // FIXME: These may not be appropriate for non-x86 architectures.
1656      if (Align <= 16) {
1657        COMDATSymName = "__xmm@" + scalarConstantToHexString(C);
1658        Align = 16;
1659      }
1660    } else if (Kind.isMergeableConst32()) {
1661      if (Align <= 32) {
1662        COMDATSymName = "__ymm@" + scalarConstantToHexString(C);
1663        Align = 32;
1664      }
1665    }
1666
1667    if (!COMDATSymName.empty())
1668      return getContext().getCOFFSection(".rdata", Characteristics, Kind,
1669                                         COMDATSymName,
1670                                         COFF::IMAGE_COMDAT_SELECT_ANY);
1671  }
1672
1673  return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C, Align);
1674}
1675
1676
1677//===----------------------------------------------------------------------===//
1678//                                  Wasm
1679//===----------------------------------------------------------------------===//
1680
1681static const Comdat *getWasmComdat(const GlobalValue *GV) {
1682  const Comdat *C = GV->getComdat();
1683  if (!C)
1684    return nullptr;
1685
1686  if (C->getSelectionKind() != Comdat::Any)
1687    report_fatal_error("WebAssembly COMDATs only support "
1688                       "SelectionKind::Any, '" + C->getName() + "' cannot be "
1689                       "lowered.");
1690
1691  return C;
1692}
1693
1694static SectionKind getWasmKindForNamedSection(StringRef Name, SectionKind K) {
1695  // If we're told we have function data, then use that.
1696  if (K.isText())
1697    return SectionKind::getText();
1698
1699  // Otherwise, ignore whatever section type the generic impl detected and use
1700  // a plain data section.
1701  return SectionKind::getData();
1702}
1703
1704MCSection *TargetLoweringObjectFileWasm::getExplicitSectionGlobal(
1705    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1706  // We don't support explict section names for functions in the wasm object
1707  // format.  Each function has to be in its own unique section.
1708  if (isa<Function>(GO)) {
1709    return SelectSectionForGlobal(GO, Kind, TM);
1710  }
1711
1712  StringRef Name = GO->getSection();
1713
1714  Kind = getWasmKindForNamedSection(Name, Kind);
1715
1716  StringRef Group = "";
1717  if (const Comdat *C = getWasmComdat(GO)) {
1718    Group = C->getName();
1719  }
1720
1721  MCSectionWasm* Section =
1722      getContext().getWasmSection(Name, Kind, Group,
1723                                  MCContext::GenericSectionID);
1724
1725  return Section;
1726}
1727
1728static MCSectionWasm *selectWasmSectionForGlobal(
1729    MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
1730    const TargetMachine &TM, bool EmitUniqueSection, unsigned *NextUniqueID) {
1731  StringRef Group = "";
1732  if (const Comdat *C = getWasmComdat(GO)) {
1733    Group = C->getName();
1734  }
1735
1736  bool UniqueSectionNames = TM.getUniqueSectionNames();
1737  SmallString<128> Name = getSectionPrefixForGlobal(Kind);
1738
1739  if (const auto *F = dyn_cast<Function>(GO)) {
1740    const auto &OptionalPrefix = F->getSectionPrefix();
1741    if (OptionalPrefix)
1742      Name += *OptionalPrefix;
1743  }
1744
1745  if (EmitUniqueSection && UniqueSectionNames) {
1746    Name.push_back('.');
1747    TM.getNameWithPrefix(Name, GO, Mang, true);
1748  }
1749  unsigned UniqueID = MCContext::GenericSectionID;
1750  if (EmitUniqueSection && !UniqueSectionNames) {
1751    UniqueID = *NextUniqueID;
1752    (*NextUniqueID)++;
1753  }
1754
1755  return Ctx.getWasmSection(Name, Kind, Group, UniqueID);
1756}
1757
1758MCSection *TargetLoweringObjectFileWasm::SelectSectionForGlobal(
1759    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1760
1761  if (Kind.isCommon())
1762    report_fatal_error("mergable sections not supported yet on wasm");
1763
1764  // If we have -ffunction-section or -fdata-section then we should emit the
1765  // global value to a uniqued section specifically for it.
1766  bool EmitUniqueSection = false;
1767  if (Kind.isText())
1768    EmitUniqueSection = TM.getFunctionSections();
1769  else
1770    EmitUniqueSection = TM.getDataSections();
1771  EmitUniqueSection |= GO->hasComdat();
1772
1773  return selectWasmSectionForGlobal(getContext(), GO, Kind, getMangler(), TM,
1774                                    EmitUniqueSection, &NextUniqueID);
1775}
1776
1777bool TargetLoweringObjectFileWasm::shouldPutJumpTableInFunctionSection(
1778    bool UsesLabelDifference, const Function &F) const {
1779  // We can always create relative relocations, so use another section
1780  // that can be marked non-executable.
1781  return false;
1782}
1783
1784const MCExpr *TargetLoweringObjectFileWasm::lowerRelativeReference(
1785    const GlobalValue *LHS, const GlobalValue *RHS,
1786    const TargetMachine &TM) const {
1787  // We may only use a PLT-relative relocation to refer to unnamed_addr
1788  // functions.
1789  if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
1790    return nullptr;
1791
1792  // Basic sanity checks.
1793  if (LHS->getType()->getPointerAddressSpace() != 0 ||
1794      RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
1795      RHS->isThreadLocal())
1796    return nullptr;
1797
1798  return MCBinaryExpr::createSub(
1799      MCSymbolRefExpr::create(TM.getSymbol(LHS), MCSymbolRefExpr::VK_None,
1800                              getContext()),
1801      MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
1802}
1803
1804void TargetLoweringObjectFileWasm::InitializeWasm() {
1805  StaticCtorSection =
1806      getContext().getWasmSection(".init_array", SectionKind::getData());
1807
1808  // We don't use PersonalityEncoding and LSDAEncoding because we don't emit
1809  // .cfi directives. We use TTypeEncoding to encode typeinfo global variables.
1810  TTypeEncoding = dwarf::DW_EH_PE_absptr;
1811}
1812
1813MCSection *TargetLoweringObjectFileWasm::getStaticCtorSection(
1814    unsigned Priority, const MCSymbol *KeySym) const {
1815  return Priority == UINT16_MAX ?
1816         StaticCtorSection :
1817         getContext().getWasmSection(".init_array." + utostr(Priority),
1818                                     SectionKind::getData());
1819}
1820
1821MCSection *TargetLoweringObjectFileWasm::getStaticDtorSection(
1822    unsigned Priority, const MCSymbol *KeySym) const {
1823  llvm_unreachable("@llvm.global_dtors should have been lowered already");
1824  return nullptr;
1825}
1826
1827//===----------------------------------------------------------------------===//
1828//                                  XCOFF
1829//===----------------------------------------------------------------------===//
1830MCSection *TargetLoweringObjectFileXCOFF::getExplicitSectionGlobal(
1831    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1832  report_fatal_error("XCOFF explicit sections not yet implemented.");
1833}
1834
1835MCSection *TargetLoweringObjectFileXCOFF::SelectSectionForGlobal(
1836    const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1837  assert(!TM.getFunctionSections() && !TM.getDataSections() &&
1838         "XCOFF unique sections not yet implemented.");
1839
1840  // Common symbols go into a csect with matching name which will get mapped
1841  // into the .bss section.
1842  if (Kind.isBSSLocal() || Kind.isCommon()) {
1843    SmallString<128> Name;
1844    getNameWithPrefix(Name, GO, TM);
1845    XCOFF::StorageClass SC =
1846        TargetLoweringObjectFileXCOFF::getStorageClassForGlobal(GO);
1847    return getContext().getXCOFFSection(
1848        Name, Kind.isBSSLocal() ? XCOFF::XMC_BS : XCOFF::XMC_RW, XCOFF::XTY_CM,
1849        SC, Kind, /* BeginSymbolName */ nullptr);
1850  }
1851
1852  if (Kind.isMergeableCString()) {
1853    if (!Kind.isMergeable1ByteCString())
1854      report_fatal_error("Unhandled multi-byte mergeable string kind.");
1855
1856    unsigned Align = GO->getParent()->getDataLayout().getPreferredAlignment(
1857        cast<GlobalVariable>(GO));
1858
1859    unsigned EntrySize = getEntrySizeForKind(Kind);
1860    std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
1861    SmallString<128> Name;
1862    Name = SizeSpec + utostr(Align);
1863
1864    return getContext().getXCOFFSection(
1865        Name, XCOFF::XMC_RO, XCOFF::XTY_SD,
1866        TargetLoweringObjectFileXCOFF::getStorageClassForGlobal(GO),
1867        Kind, /* BeginSymbolName */ nullptr);
1868  }
1869
1870  if (Kind.isText())
1871    return TextSection;
1872
1873  if (Kind.isData() || Kind.isReadOnlyWithRel())
1874    // TODO: We may put this under option control, because user may want to
1875    // have read-only data with relocations placed into a read-only section by
1876    // the compiler.
1877    return DataSection;
1878
1879  // Zero initialized data must be emitted to the .data section because external
1880  // linkage control sections that get mapped to the .bss section will be linked
1881  // as tentative defintions, which is only appropriate for SectionKind::Common.
1882  if (Kind.isBSS())
1883    return DataSection;
1884
1885  if (Kind.isReadOnly())
1886    return ReadOnlySection;
1887
1888  report_fatal_error("XCOFF other section types not yet implemented.");
1889}
1890
1891MCSection *TargetLoweringObjectFileXCOFF::getSectionForJumpTable(
1892    const Function &F, const TargetMachine &TM) const {
1893  assert (!TM.getFunctionSections() && "Unique sections not supported on XCOFF"
1894          " yet.");
1895  assert (!F.getComdat() && "Comdat not supported on XCOFF.");
1896  //TODO: Enable emiting jump table to unique sections when we support it.
1897  return ReadOnlySection;
1898}
1899
1900bool TargetLoweringObjectFileXCOFF::shouldPutJumpTableInFunctionSection(
1901    bool UsesLabelDifference, const Function &F) const {
1902  return false;
1903}
1904
1905/// Given a mergeable constant with the specified size and relocation
1906/// information, return a section that it should be placed in.
1907MCSection *TargetLoweringObjectFileXCOFF::getSectionForConstant(
1908    const DataLayout &DL, SectionKind Kind, const Constant *C,
1909    unsigned &Align) const {
1910  //TODO: Enable emiting constant pool to unique sections when we support it.
1911  return ReadOnlySection;
1912}
1913
1914void TargetLoweringObjectFileXCOFF::Initialize(MCContext &Ctx,
1915                                               const TargetMachine &TgtM) {
1916  TargetLoweringObjectFile::Initialize(Ctx, TgtM);
1917  TTypeEncoding = 0;
1918  PersonalityEncoding = 0;
1919  LSDAEncoding = 0;
1920}
1921
1922MCSection *TargetLoweringObjectFileXCOFF::getStaticCtorSection(
1923    unsigned Priority, const MCSymbol *KeySym) const {
1924  report_fatal_error("XCOFF ctor section not yet implemented.");
1925}
1926
1927MCSection *TargetLoweringObjectFileXCOFF::getStaticDtorSection(
1928    unsigned Priority, const MCSymbol *KeySym) const {
1929  report_fatal_error("XCOFF dtor section not yet implemented.");
1930}
1931
1932const MCExpr *TargetLoweringObjectFileXCOFF::lowerRelativeReference(
1933    const GlobalValue *LHS, const GlobalValue *RHS,
1934    const TargetMachine &TM) const {
1935  report_fatal_error("XCOFF not yet implemented.");
1936}
1937
1938XCOFF::StorageClass TargetLoweringObjectFileXCOFF::getStorageClassForGlobal(
1939    const GlobalObject *GO) {
1940  switch (GO->getLinkage()) {
1941  case GlobalValue::InternalLinkage:
1942  case GlobalValue::PrivateLinkage:
1943    return XCOFF::C_HIDEXT;
1944  case GlobalValue::ExternalLinkage:
1945  case GlobalValue::CommonLinkage:
1946    return XCOFF::C_EXT;
1947  case GlobalValue::ExternalWeakLinkage:
1948    return XCOFF::C_WEAKEXT;
1949  default:
1950    report_fatal_error(
1951        "Unhandled linkage when mapping linkage to StorageClass.");
1952  }
1953}
1954