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/SmallVector.h"
18 #include "llvm/ADT/StringExtras.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/ADT/Triple.h"
21 #include "llvm/BinaryFormat/COFF.h"
22 #include "llvm/BinaryFormat/Dwarf.h"
23 #include "llvm/BinaryFormat/ELF.h"
24 #include "llvm/BinaryFormat/MachO.h"
25 #include "llvm/CodeGen/MachineModuleInfo.h"
26 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
27 #include "llvm/IR/Comdat.h"
28 #include "llvm/IR/Constants.h"
29 #include "llvm/IR/DataLayout.h"
30 #include "llvm/IR/DerivedTypes.h"
31 #include "llvm/IR/Function.h"
32 #include "llvm/IR/GlobalAlias.h"
33 #include "llvm/IR/GlobalObject.h"
34 #include "llvm/IR/GlobalValue.h"
35 #include "llvm/IR/GlobalVariable.h"
36 #include "llvm/IR/Mangler.h"
37 #include "llvm/IR/Metadata.h"
38 #include "llvm/IR/Module.h"
39 #include "llvm/IR/Type.h"
40 #include "llvm/MC/MCAsmInfo.h"
41 #include "llvm/MC/MCContext.h"
42 #include "llvm/MC/MCExpr.h"
43 #include "llvm/MC/MCSectionCOFF.h"
44 #include "llvm/MC/MCSectionELF.h"
45 #include "llvm/MC/MCSectionMachO.h"
46 #include "llvm/MC/MCSectionWasm.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 
62 using namespace llvm;
63 using namespace dwarf;
64 
GetObjCImageInfo(Module & M,unsigned & Version,unsigned & Flags,StringRef & Section)65 static 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 
Initialize(MCContext & Ctx,const TargetMachine & TgtM)94 void 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     // The small model guarantees static code/data size < 4GB, but not where it
159     // will be in memory. Most of these could end up >2GB away so even a signed
160     // pc-relative 32-bit address is insufficient, theoretically.
161     if (isPositionIndependent()) {
162       PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
163         dwarf::DW_EH_PE_sdata8;
164       LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8;
165       TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
166         dwarf::DW_EH_PE_sdata8;
167     } else {
168       PersonalityEncoding = dwarf::DW_EH_PE_absptr;
169       LSDAEncoding = dwarf::DW_EH_PE_absptr;
170       TTypeEncoding = dwarf::DW_EH_PE_absptr;
171     }
172     break;
173   case Triple::lanai:
174     LSDAEncoding = dwarf::DW_EH_PE_absptr;
175     PersonalityEncoding = dwarf::DW_EH_PE_absptr;
176     TTypeEncoding = dwarf::DW_EH_PE_absptr;
177     break;
178   case Triple::mips:
179   case Triple::mipsel:
180   case Triple::mips64:
181   case Triple::mips64el:
182     // MIPS uses indirect pointer to refer personality functions and types, so
183     // that the eh_frame section can be read-only. DW.ref.personality will be
184     // generated for relocation.
185     PersonalityEncoding = dwarf::DW_EH_PE_indirect;
186     // FIXME: The N64 ABI probably ought to use DW_EH_PE_sdata8 but we can't
187     //        identify N64 from just a triple.
188     TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
189                     dwarf::DW_EH_PE_sdata4;
190     // We don't support PC-relative LSDA references in GAS so we use the default
191     // DW_EH_PE_absptr for those.
192 
193     // FreeBSD must be explicit about the data size and using pcrel since it's
194     // assembler/linker won't do the automatic conversion that the Linux tools
195     // do.
196     if (TgtM.getTargetTriple().isOSFreeBSD()) {
197       PersonalityEncoding |= dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
198       LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
199     }
200     break;
201   case Triple::ppc64:
202   case Triple::ppc64le:
203     PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
204       dwarf::DW_EH_PE_udata8;
205     LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8;
206     TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
207       dwarf::DW_EH_PE_udata8;
208     break;
209   case Triple::sparcel:
210   case Triple::sparc:
211     if (isPositionIndependent()) {
212       LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
213       PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
214         dwarf::DW_EH_PE_sdata4;
215       TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
216         dwarf::DW_EH_PE_sdata4;
217     } else {
218       LSDAEncoding = dwarf::DW_EH_PE_absptr;
219       PersonalityEncoding = dwarf::DW_EH_PE_absptr;
220       TTypeEncoding = dwarf::DW_EH_PE_absptr;
221     }
222     break;
223   case Triple::sparcv9:
224     LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
225     if (isPositionIndependent()) {
226       PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
227         dwarf::DW_EH_PE_sdata4;
228       TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
229         dwarf::DW_EH_PE_sdata4;
230     } else {
231       PersonalityEncoding = dwarf::DW_EH_PE_absptr;
232       TTypeEncoding = dwarf::DW_EH_PE_absptr;
233     }
234     break;
235   case Triple::systemz:
236     // All currently-defined code models guarantee that 4-byte PC-relative
237     // values will be in range.
238     if (isPositionIndependent()) {
239       PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
240         dwarf::DW_EH_PE_sdata4;
241       LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
242       TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
243         dwarf::DW_EH_PE_sdata4;
244     } else {
245       PersonalityEncoding = dwarf::DW_EH_PE_absptr;
246       LSDAEncoding = dwarf::DW_EH_PE_absptr;
247       TTypeEncoding = dwarf::DW_EH_PE_absptr;
248     }
249     break;
250   default:
251     break;
252   }
253 }
254 
emitModuleMetadata(MCStreamer & Streamer,Module & M) const255 void TargetLoweringObjectFileELF::emitModuleMetadata(MCStreamer &Streamer,
256                                                      Module &M) const {
257   auto &C = getContext();
258 
259   if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
260     auto *S = C.getELFSection(".linker-options", ELF::SHT_LLVM_LINKER_OPTIONS,
261                               ELF::SHF_EXCLUDE);
262 
263     Streamer.SwitchSection(S);
264 
265     for (const auto &Operand : LinkerOptions->operands()) {
266       if (cast<MDNode>(Operand)->getNumOperands() != 2)
267         report_fatal_error("invalid llvm.linker.options");
268       for (const auto &Option : cast<MDNode>(Operand)->operands()) {
269         Streamer.EmitBytes(cast<MDString>(Option)->getString());
270         Streamer.EmitIntValue(0, 1);
271       }
272     }
273   }
274 
275   unsigned Version = 0;
276   unsigned Flags = 0;
277   StringRef Section;
278 
279   GetObjCImageInfo(M, Version, Flags, Section);
280   if (!Section.empty()) {
281     auto *S = C.getELFSection(Section, ELF::SHT_PROGBITS, ELF::SHF_ALLOC);
282     Streamer.SwitchSection(S);
283     Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
284     Streamer.EmitIntValue(Version, 4);
285     Streamer.EmitIntValue(Flags, 4);
286     Streamer.AddBlankLine();
287   }
288 
289   SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
290   M.getModuleFlagsMetadata(ModuleFlags);
291 
292   MDNode *CFGProfile = nullptr;
293 
294   for (const auto &MFE : ModuleFlags) {
295     StringRef Key = MFE.Key->getString();
296     if (Key == "CG Profile") {
297       CFGProfile = cast<MDNode>(MFE.Val);
298       break;
299     }
300   }
301 
302   if (!CFGProfile)
303     return;
304 
305   auto GetSym = [this](const MDOperand &MDO) -> MCSymbol * {
306     if (!MDO)
307       return nullptr;
308     auto V = cast<ValueAsMetadata>(MDO);
309     const Function *F = cast<Function>(V->getValue());
310     return TM->getSymbol(F);
311   };
312 
313   for (const auto &Edge : CFGProfile->operands()) {
314     MDNode *E = cast<MDNode>(Edge);
315     const MCSymbol *From = GetSym(E->getOperand(0));
316     const MCSymbol *To = GetSym(E->getOperand(1));
317     // Skip null functions. This can happen if functions are dead stripped after
318     // the CGProfile pass has been run.
319     if (!From || !To)
320       continue;
321     uint64_t Count = cast<ConstantAsMetadata>(E->getOperand(2))
322                          ->getValue()
323                          ->getUniqueInteger()
324                          .getZExtValue();
325     Streamer.emitCGProfileEntry(
326         MCSymbolRefExpr::create(From, MCSymbolRefExpr::VK_None, C),
327         MCSymbolRefExpr::create(To, MCSymbolRefExpr::VK_None, C), Count);
328   }
329 }
330 
getCFIPersonalitySymbol(const GlobalValue * GV,const TargetMachine & TM,MachineModuleInfo * MMI) const331 MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
332     const GlobalValue *GV, const TargetMachine &TM,
333     MachineModuleInfo *MMI) const {
334   unsigned Encoding = getPersonalityEncoding();
335   if ((Encoding & 0x80) == DW_EH_PE_indirect)
336     return getContext().getOrCreateSymbol(StringRef("DW.ref.") +
337                                           TM.getSymbol(GV)->getName());
338   if ((Encoding & 0x70) == DW_EH_PE_absptr)
339     return TM.getSymbol(GV);
340   report_fatal_error("We do not support this DWARF encoding yet!");
341 }
342 
emitPersonalityValue(MCStreamer & Streamer,const DataLayout & DL,const MCSymbol * Sym) const343 void TargetLoweringObjectFileELF::emitPersonalityValue(
344     MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
345   SmallString<64> NameData("DW.ref.");
346   NameData += Sym->getName();
347   MCSymbolELF *Label =
348       cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
349   Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
350   Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
351   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
352   MCSection *Sec = getContext().getELFNamedSection(".data", Label->getName(),
353                                                    ELF::SHT_PROGBITS, Flags, 0);
354   unsigned Size = DL.getPointerSize();
355   Streamer.SwitchSection(Sec);
356   Streamer.EmitValueToAlignment(DL.getPointerABIAlignment(0));
357   Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
358   const MCExpr *E = MCConstantExpr::create(Size, getContext());
359   Streamer.emitELFSize(Label, E);
360   Streamer.EmitLabel(Label);
361 
362   Streamer.EmitSymbolValue(Sym, Size);
363 }
364 
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const365 const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
366     const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
367     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
368   if (Encoding & DW_EH_PE_indirect) {
369     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
370 
371     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", TM);
372 
373     // Add information about the stub reference to ELFMMI so that the stub
374     // gets emitted by the asmprinter.
375     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
376     if (!StubSym.getPointer()) {
377       MCSymbol *Sym = TM.getSymbol(GV);
378       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
379     }
380 
381     return TargetLoweringObjectFile::
382       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
383                         Encoding & ~DW_EH_PE_indirect, Streamer);
384   }
385 
386   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
387                                                            MMI, Streamer);
388 }
389 
getELFKindForNamedSection(StringRef Name,SectionKind K)390 static SectionKind getELFKindForNamedSection(StringRef Name, SectionKind K) {
391   // N.B.: The defaults used in here are not the same ones used in MC.
392   // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
393   // both gas and MC will produce a section with no flags. Given
394   // section(".eh_frame") gcc will produce:
395   //
396   //   .section   .eh_frame,"a",@progbits
397 
398   if (Name == getInstrProfSectionName(IPSK_covmap, Triple::ELF,
399                                       /*AddSegmentInfo=*/false))
400     return SectionKind::getMetadata();
401 
402   if (Name.empty() || Name[0] != '.') return K;
403 
404   // Default implementation based on some magic section names.
405   if (Name == ".bss" ||
406       Name.startswith(".bss.") ||
407       Name.startswith(".gnu.linkonce.b.") ||
408       Name.startswith(".llvm.linkonce.b.") ||
409       Name == ".sbss" ||
410       Name.startswith(".sbss.") ||
411       Name.startswith(".gnu.linkonce.sb.") ||
412       Name.startswith(".llvm.linkonce.sb."))
413     return SectionKind::getBSS();
414 
415   if (Name == ".tdata" ||
416       Name.startswith(".tdata.") ||
417       Name.startswith(".gnu.linkonce.td.") ||
418       Name.startswith(".llvm.linkonce.td."))
419     return SectionKind::getThreadData();
420 
421   if (Name == ".tbss" ||
422       Name.startswith(".tbss.") ||
423       Name.startswith(".gnu.linkonce.tb.") ||
424       Name.startswith(".llvm.linkonce.tb."))
425     return SectionKind::getThreadBSS();
426 
427   return K;
428 }
429 
getELFSectionType(StringRef Name,SectionKind K)430 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
431   // Use SHT_NOTE for section whose name starts with ".note" to allow
432   // emitting ELF notes from C variable declaration.
433   // See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77609
434   if (Name.startswith(".note"))
435     return ELF::SHT_NOTE;
436 
437   if (Name == ".init_array")
438     return ELF::SHT_INIT_ARRAY;
439 
440   if (Name == ".fini_array")
441     return ELF::SHT_FINI_ARRAY;
442 
443   if (Name == ".preinit_array")
444     return ELF::SHT_PREINIT_ARRAY;
445 
446   if (K.isBSS() || K.isThreadBSS())
447     return ELF::SHT_NOBITS;
448 
449   return ELF::SHT_PROGBITS;
450 }
451 
getELFSectionFlags(SectionKind K)452 static unsigned getELFSectionFlags(SectionKind K) {
453   unsigned Flags = 0;
454 
455   if (!K.isMetadata())
456     Flags |= ELF::SHF_ALLOC;
457 
458   if (K.isText())
459     Flags |= ELF::SHF_EXECINSTR;
460 
461   if (K.isExecuteOnly())
462     Flags |= ELF::SHF_ARM_PURECODE;
463 
464   if (K.isWriteable())
465     Flags |= ELF::SHF_WRITE;
466 
467   if (K.isThreadLocal())
468     Flags |= ELF::SHF_TLS;
469 
470   if (K.isMergeableCString() || K.isMergeableConst())
471     Flags |= ELF::SHF_MERGE;
472 
473   if (K.isMergeableCString())
474     Flags |= ELF::SHF_STRINGS;
475 
476   return Flags;
477 }
478 
getELFComdat(const GlobalValue * GV)479 static const Comdat *getELFComdat(const GlobalValue *GV) {
480   const Comdat *C = GV->getComdat();
481   if (!C)
482     return nullptr;
483 
484   if (C->getSelectionKind() != Comdat::Any)
485     report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
486                        C->getName() + "' cannot be lowered.");
487 
488   return C;
489 }
490 
getAssociatedSymbol(const GlobalObject * GO,const TargetMachine & TM)491 static const MCSymbolELF *getAssociatedSymbol(const GlobalObject *GO,
492                                               const TargetMachine &TM) {
493   MDNode *MD = GO->getMetadata(LLVMContext::MD_associated);
494   if (!MD)
495     return nullptr;
496 
497   const MDOperand &Op = MD->getOperand(0);
498   if (!Op.get())
499     return nullptr;
500 
501   auto *VM = dyn_cast<ValueAsMetadata>(Op);
502   if (!VM)
503     report_fatal_error("MD_associated operand is not ValueAsMetadata");
504 
505   GlobalObject *OtherGO = dyn_cast<GlobalObject>(VM->getValue());
506   return OtherGO ? dyn_cast<MCSymbolELF>(TM.getSymbol(OtherGO)) : nullptr;
507 }
508 
getEntrySizeForKind(SectionKind Kind)509 static unsigned getEntrySizeForKind(SectionKind Kind) {
510   if (Kind.isMergeable1ByteCString())
511     return 1;
512   else if (Kind.isMergeable2ByteCString())
513     return 2;
514   else if (Kind.isMergeable4ByteCString())
515     return 4;
516   else if (Kind.isMergeableConst4())
517     return 4;
518   else if (Kind.isMergeableConst8())
519     return 8;
520   else if (Kind.isMergeableConst16())
521     return 16;
522   else if (Kind.isMergeableConst32())
523     return 32;
524   else {
525     // We shouldn't have mergeable C strings or mergeable constants that we
526     // didn't handle above.
527     assert(!Kind.isMergeableCString() && "unknown string width");
528     assert(!Kind.isMergeableConst() && "unknown data width");
529     return 0;
530   }
531 }
532 
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const533 MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
534     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
535   StringRef SectionName = GO->getSection();
536 
537   // Check if '#pragma clang section' name is applicable.
538   // Note that pragma directive overrides -ffunction-section, -fdata-section
539   // and so section name is exactly as user specified and not uniqued.
540   const GlobalVariable *GV = dyn_cast<GlobalVariable>(GO);
541   if (GV && GV->hasImplicitSection()) {
542     auto Attrs = GV->getAttributes();
543     if (Attrs.hasAttribute("bss-section") && Kind.isBSS()) {
544       SectionName = Attrs.getAttribute("bss-section").getValueAsString();
545     } else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()) {
546       SectionName = Attrs.getAttribute("rodata-section").getValueAsString();
547     } else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
548       SectionName = Attrs.getAttribute("data-section").getValueAsString();
549     }
550   }
551   const Function *F = dyn_cast<Function>(GO);
552   if (F && F->hasFnAttribute("implicit-section-name")) {
553     SectionName = F->getFnAttribute("implicit-section-name").getValueAsString();
554   }
555 
556   // Infer section flags from the section name if we can.
557   Kind = getELFKindForNamedSection(SectionName, Kind);
558 
559   StringRef Group = "";
560   unsigned Flags = getELFSectionFlags(Kind);
561   if (const Comdat *C = getELFComdat(GO)) {
562     Group = C->getName();
563     Flags |= ELF::SHF_GROUP;
564   }
565 
566   // A section can have at most one associated section. Put each global with
567   // MD_associated in a unique section.
568   unsigned UniqueID = MCContext::GenericSectionID;
569   const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
570   if (AssociatedSymbol) {
571     UniqueID = NextUniqueID++;
572     Flags |= ELF::SHF_LINK_ORDER;
573   }
574 
575   MCSectionELF *Section = getContext().getELFSection(
576       SectionName, getELFSectionType(SectionName, Kind), Flags,
577       getEntrySizeForKind(Kind), Group, UniqueID, AssociatedSymbol);
578   // Make sure that we did not get some other section with incompatible sh_link.
579   // This should not be possible due to UniqueID code above.
580   assert(Section->getAssociatedSymbol() == AssociatedSymbol &&
581          "Associated symbol mismatch between sections");
582   return Section;
583 }
584 
585 /// Return the section prefix name used by options FunctionsSections and
586 /// DataSections.
getSectionPrefixForGlobal(SectionKind Kind)587 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
588   if (Kind.isText())
589     return ".text";
590   if (Kind.isReadOnly())
591     return ".rodata";
592   if (Kind.isBSS())
593     return ".bss";
594   if (Kind.isThreadData())
595     return ".tdata";
596   if (Kind.isThreadBSS())
597     return ".tbss";
598   if (Kind.isData())
599     return ".data";
600   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
601   return ".data.rel.ro";
602 }
603 
selectELFSectionForGlobal(MCContext & Ctx,const GlobalObject * GO,SectionKind Kind,Mangler & Mang,const TargetMachine & TM,bool EmitUniqueSection,unsigned Flags,unsigned * NextUniqueID,const MCSymbolELF * AssociatedSymbol)604 static MCSectionELF *selectELFSectionForGlobal(
605     MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
606     const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
607     unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol) {
608 
609   StringRef Group = "";
610   if (const Comdat *C = getELFComdat(GO)) {
611     Flags |= ELF::SHF_GROUP;
612     Group = C->getName();
613   }
614 
615   // Get the section entry size based on the kind.
616   unsigned EntrySize = getEntrySizeForKind(Kind);
617 
618   SmallString<128> Name;
619   if (Kind.isMergeableCString()) {
620     // We also need alignment here.
621     // FIXME: this is getting the alignment of the character, not the
622     // alignment of the global!
623     unsigned Align = GO->getParent()->getDataLayout().getPreferredAlignment(
624         cast<GlobalVariable>(GO));
625 
626     std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
627     Name = SizeSpec + utostr(Align);
628   } else if (Kind.isMergeableConst()) {
629     Name = ".rodata.cst";
630     Name += utostr(EntrySize);
631   } else {
632     Name = getSectionPrefixForGlobal(Kind);
633   }
634 
635   if (const auto *F = dyn_cast<Function>(GO)) {
636     const auto &OptionalPrefix = F->getSectionPrefix();
637     if (OptionalPrefix)
638       Name += *OptionalPrefix;
639   }
640 
641   unsigned UniqueID = MCContext::GenericSectionID;
642   if (EmitUniqueSection) {
643     if (TM.getUniqueSectionNames()) {
644       Name.push_back('.');
645       TM.getNameWithPrefix(Name, GO, Mang, true /*MayAlwaysUsePrivate*/);
646     } else {
647       UniqueID = *NextUniqueID;
648       (*NextUniqueID)++;
649     }
650   }
651   // Use 0 as the unique ID for execute-only text.
652   if (Kind.isExecuteOnly())
653     UniqueID = 0;
654   return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags,
655                            EntrySize, Group, UniqueID, AssociatedSymbol);
656 }
657 
SelectSectionForGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const658 MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
659     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
660   unsigned Flags = getELFSectionFlags(Kind);
661 
662   // If we have -ffunction-section or -fdata-section then we should emit the
663   // global value to a uniqued section specifically for it.
664   bool EmitUniqueSection = false;
665   if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
666     if (Kind.isText())
667       EmitUniqueSection = TM.getFunctionSections();
668     else
669       EmitUniqueSection = TM.getDataSections();
670   }
671   EmitUniqueSection |= GO->hasComdat();
672 
673   const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
674   if (AssociatedSymbol) {
675     EmitUniqueSection = true;
676     Flags |= ELF::SHF_LINK_ORDER;
677   }
678 
679   MCSectionELF *Section = selectELFSectionForGlobal(
680       getContext(), GO, Kind, getMangler(), TM, EmitUniqueSection, Flags,
681       &NextUniqueID, AssociatedSymbol);
682   assert(Section->getAssociatedSymbol() == AssociatedSymbol);
683   return Section;
684 }
685 
getSectionForJumpTable(const Function & F,const TargetMachine & TM) const686 MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
687     const Function &F, const TargetMachine &TM) const {
688   // If the function can be removed, produce a unique section so that
689   // the table doesn't prevent the removal.
690   const Comdat *C = F.getComdat();
691   bool EmitUniqueSection = TM.getFunctionSections() || C;
692   if (!EmitUniqueSection)
693     return ReadOnlySection;
694 
695   return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
696                                    getMangler(), TM, EmitUniqueSection,
697                                    ELF::SHF_ALLOC, &NextUniqueID,
698                                    /* AssociatedSymbol */ nullptr);
699 }
700 
shouldPutJumpTableInFunctionSection(bool UsesLabelDifference,const Function & F) const701 bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
702     bool UsesLabelDifference, const Function &F) const {
703   // We can always create relative relocations, so use another section
704   // that can be marked non-executable.
705   return false;
706 }
707 
708 /// Given a mergeable constant with the specified size and relocation
709 /// information, return a section that it should be placed in.
getSectionForConstant(const DataLayout & DL,SectionKind Kind,const Constant * C,unsigned & Align) const710 MCSection *TargetLoweringObjectFileELF::getSectionForConstant(
711     const DataLayout &DL, SectionKind Kind, const Constant *C,
712     unsigned &Align) const {
713   if (Kind.isMergeableConst4() && MergeableConst4Section)
714     return MergeableConst4Section;
715   if (Kind.isMergeableConst8() && MergeableConst8Section)
716     return MergeableConst8Section;
717   if (Kind.isMergeableConst16() && MergeableConst16Section)
718     return MergeableConst16Section;
719   if (Kind.isMergeableConst32() && MergeableConst32Section)
720     return MergeableConst32Section;
721   if (Kind.isReadOnly())
722     return ReadOnlySection;
723 
724   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
725   return DataRelROSection;
726 }
727 
getStaticStructorSection(MCContext & Ctx,bool UseInitArray,bool IsCtor,unsigned Priority,const MCSymbol * KeySym)728 static MCSectionELF *getStaticStructorSection(MCContext &Ctx, bool UseInitArray,
729                                               bool IsCtor, unsigned Priority,
730                                               const MCSymbol *KeySym) {
731   std::string Name;
732   unsigned Type;
733   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
734   StringRef COMDAT = KeySym ? KeySym->getName() : "";
735 
736   if (KeySym)
737     Flags |= ELF::SHF_GROUP;
738 
739   if (UseInitArray) {
740     if (IsCtor) {
741       Type = ELF::SHT_INIT_ARRAY;
742       Name = ".init_array";
743     } else {
744       Type = ELF::SHT_FINI_ARRAY;
745       Name = ".fini_array";
746     }
747     if (Priority != 65535) {
748       Name += '.';
749       Name += utostr(Priority);
750     }
751   } else {
752     // The default scheme is .ctor / .dtor, so we have to invert the priority
753     // numbering.
754     if (IsCtor)
755       Name = ".ctors";
756     else
757       Name = ".dtors";
758     if (Priority != 65535)
759       raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
760     Type = ELF::SHT_PROGBITS;
761   }
762 
763   return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
764 }
765 
getStaticCtorSection(unsigned Priority,const MCSymbol * KeySym) const766 MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
767     unsigned Priority, const MCSymbol *KeySym) const {
768   return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
769                                   KeySym);
770 }
771 
getStaticDtorSection(unsigned Priority,const MCSymbol * KeySym) const772 MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
773     unsigned Priority, const MCSymbol *KeySym) const {
774   return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
775                                   KeySym);
776 }
777 
lowerRelativeReference(const GlobalValue * LHS,const GlobalValue * RHS,const TargetMachine & TM) const778 const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
779     const GlobalValue *LHS, const GlobalValue *RHS,
780     const TargetMachine &TM) const {
781   // We may only use a PLT-relative relocation to refer to unnamed_addr
782   // functions.
783   if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
784     return nullptr;
785 
786   // Basic sanity checks.
787   if (LHS->getType()->getPointerAddressSpace() != 0 ||
788       RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
789       RHS->isThreadLocal())
790     return nullptr;
791 
792   return MCBinaryExpr::createSub(
793       MCSymbolRefExpr::create(TM.getSymbol(LHS), PLTRelativeVariantKind,
794                               getContext()),
795       MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
796 }
797 
getSectionForCommandLines() const798 MCSection *TargetLoweringObjectFileELF::getSectionForCommandLines() const {
799   // Use ".GCC.command.line" since this feature is to support clang's
800   // -frecord-gcc-switches which in turn attempts to mimic GCC's switch of the
801   // same name.
802   return getContext().getELFSection(".GCC.command.line", ELF::SHT_PROGBITS,
803                                     ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
804 }
805 
806 void
InitializeELF(bool UseInitArray_)807 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
808   UseInitArray = UseInitArray_;
809   MCContext &Ctx = getContext();
810   if (!UseInitArray) {
811     StaticCtorSection = Ctx.getELFSection(".ctors", ELF::SHT_PROGBITS,
812                                           ELF::SHF_ALLOC | ELF::SHF_WRITE);
813 
814     StaticDtorSection = Ctx.getELFSection(".dtors", ELF::SHT_PROGBITS,
815                                           ELF::SHF_ALLOC | ELF::SHF_WRITE);
816     return;
817   }
818 
819   StaticCtorSection = Ctx.getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
820                                         ELF::SHF_WRITE | ELF::SHF_ALLOC);
821   StaticDtorSection = Ctx.getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
822                                         ELF::SHF_WRITE | ELF::SHF_ALLOC);
823 }
824 
825 //===----------------------------------------------------------------------===//
826 //                                 MachO
827 //===----------------------------------------------------------------------===//
828 
TargetLoweringObjectFileMachO()829 TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
830   : TargetLoweringObjectFile() {
831   SupportIndirectSymViaGOTPCRel = true;
832 }
833 
Initialize(MCContext & Ctx,const TargetMachine & TM)834 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
835                                                const TargetMachine &TM) {
836   TargetLoweringObjectFile::Initialize(Ctx, TM);
837   if (TM.getRelocationModel() == Reloc::Static) {
838     StaticCtorSection = Ctx.getMachOSection("__TEXT", "__constructor", 0,
839                                             SectionKind::getData());
840     StaticDtorSection = Ctx.getMachOSection("__TEXT", "__destructor", 0,
841                                             SectionKind::getData());
842   } else {
843     StaticCtorSection = Ctx.getMachOSection("__DATA", "__mod_init_func",
844                                             MachO::S_MOD_INIT_FUNC_POINTERS,
845                                             SectionKind::getData());
846     StaticDtorSection = Ctx.getMachOSection("__DATA", "__mod_term_func",
847                                             MachO::S_MOD_TERM_FUNC_POINTERS,
848                                             SectionKind::getData());
849   }
850 
851   PersonalityEncoding =
852       dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
853   LSDAEncoding = dwarf::DW_EH_PE_pcrel;
854   TTypeEncoding =
855       dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
856 }
857 
emitModuleMetadata(MCStreamer & Streamer,Module & M) const858 void TargetLoweringObjectFileMachO::emitModuleMetadata(MCStreamer &Streamer,
859                                                        Module &M) const {
860   // Emit the linker options if present.
861   if (auto *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
862     for (const auto &Option : LinkerOptions->operands()) {
863       SmallVector<std::string, 4> StrOptions;
864       for (const auto &Piece : cast<MDNode>(Option)->operands())
865         StrOptions.push_back(cast<MDString>(Piece)->getString());
866       Streamer.EmitLinkerOptions(StrOptions);
867     }
868   }
869 
870   unsigned VersionVal = 0;
871   unsigned ImageInfoFlags = 0;
872   StringRef SectionVal;
873 
874   GetObjCImageInfo(M, VersionVal, ImageInfoFlags, SectionVal);
875 
876   // The section is mandatory. If we don't have it, then we don't have GC info.
877   if (SectionVal.empty())
878     return;
879 
880   StringRef Segment, Section;
881   unsigned TAA = 0, StubSize = 0;
882   bool TAAParsed;
883   std::string ErrorCode =
884     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
885                                           TAA, TAAParsed, StubSize);
886   if (!ErrorCode.empty())
887     // If invalid, report the error with report_fatal_error.
888     report_fatal_error("Invalid section specifier '" + Section + "': " +
889                        ErrorCode + ".");
890 
891   // Get the section.
892   MCSectionMachO *S = getContext().getMachOSection(
893       Segment, Section, TAA, StubSize, SectionKind::getData());
894   Streamer.SwitchSection(S);
895   Streamer.EmitLabel(getContext().
896                      getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
897   Streamer.EmitIntValue(VersionVal, 4);
898   Streamer.EmitIntValue(ImageInfoFlags, 4);
899   Streamer.AddBlankLine();
900 }
901 
checkMachOComdat(const GlobalValue * GV)902 static void checkMachOComdat(const GlobalValue *GV) {
903   const Comdat *C = GV->getComdat();
904   if (!C)
905     return;
906 
907   report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
908                      "' cannot be lowered.");
909 }
910 
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const911 MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
912     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
913   // Parse the section specifier and create it if valid.
914   StringRef Segment, Section;
915   unsigned TAA = 0, StubSize = 0;
916   bool TAAParsed;
917 
918   checkMachOComdat(GO);
919 
920   std::string ErrorCode =
921     MCSectionMachO::ParseSectionSpecifier(GO->getSection(), Segment, Section,
922                                           TAA, TAAParsed, StubSize);
923   if (!ErrorCode.empty()) {
924     // If invalid, report the error with report_fatal_error.
925     report_fatal_error("Global variable '" + GO->getName() +
926                        "' has an invalid section specifier '" +
927                        GO->getSection() + "': " + ErrorCode + ".");
928   }
929 
930   // Get the section.
931   MCSectionMachO *S =
932       getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
933 
934   // If TAA wasn't set by ParseSectionSpecifier() above,
935   // use the value returned by getMachOSection() as a default.
936   if (!TAAParsed)
937     TAA = S->getTypeAndAttributes();
938 
939   // Okay, now that we got the section, verify that the TAA & StubSize agree.
940   // If the user declared multiple globals with different section flags, we need
941   // to reject it here.
942   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
943     // If invalid, report the error with report_fatal_error.
944     report_fatal_error("Global variable '" + GO->getName() +
945                        "' section type or attributes does not match previous"
946                        " section specifier");
947   }
948 
949   return S;
950 }
951 
SelectSectionForGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const952 MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
953     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
954   checkMachOComdat(GO);
955 
956   // Handle thread local data.
957   if (Kind.isThreadBSS()) return TLSBSSSection;
958   if (Kind.isThreadData()) return TLSDataSection;
959 
960   if (Kind.isText())
961     return GO->isWeakForLinker() ? TextCoalSection : TextSection;
962 
963   // If this is weak/linkonce, put this in a coalescable section, either in text
964   // or data depending on if it is writable.
965   if (GO->isWeakForLinker()) {
966     if (Kind.isReadOnly())
967       return ConstTextCoalSection;
968     if (Kind.isReadOnlyWithRel())
969       return ConstDataCoalSection;
970     return DataCoalSection;
971   }
972 
973   // FIXME: Alignment check should be handled by section classifier.
974   if (Kind.isMergeable1ByteCString() &&
975       GO->getParent()->getDataLayout().getPreferredAlignment(
976           cast<GlobalVariable>(GO)) < 32)
977     return CStringSection;
978 
979   // Do not put 16-bit arrays in the UString section if they have an
980   // externally visible label, this runs into issues with certain linker
981   // versions.
982   if (Kind.isMergeable2ByteCString() && !GO->hasExternalLinkage() &&
983       GO->getParent()->getDataLayout().getPreferredAlignment(
984           cast<GlobalVariable>(GO)) < 32)
985     return UStringSection;
986 
987   // With MachO only variables whose corresponding symbol starts with 'l' or
988   // 'L' can be merged, so we only try merging GVs with private linkage.
989   if (GO->hasPrivateLinkage() && Kind.isMergeableConst()) {
990     if (Kind.isMergeableConst4())
991       return FourByteConstantSection;
992     if (Kind.isMergeableConst8())
993       return EightByteConstantSection;
994     if (Kind.isMergeableConst16())
995       return SixteenByteConstantSection;
996   }
997 
998   // Otherwise, if it is readonly, but not something we can specially optimize,
999   // just drop it in .const.
1000   if (Kind.isReadOnly())
1001     return ReadOnlySection;
1002 
1003   // If this is marked const, put it into a const section.  But if the dynamic
1004   // linker needs to write to it, put it in the data segment.
1005   if (Kind.isReadOnlyWithRel())
1006     return ConstDataSection;
1007 
1008   // Put zero initialized globals with strong external linkage in the
1009   // DATA, __common section with the .zerofill directive.
1010   if (Kind.isBSSExtern())
1011     return DataCommonSection;
1012 
1013   // Put zero initialized globals with local linkage in __DATA,__bss directive
1014   // with the .zerofill directive (aka .lcomm).
1015   if (Kind.isBSSLocal())
1016     return DataBSSSection;
1017 
1018   // Otherwise, just drop the variable in the normal data section.
1019   return DataSection;
1020 }
1021 
getSectionForConstant(const DataLayout & DL,SectionKind Kind,const Constant * C,unsigned & Align) const1022 MCSection *TargetLoweringObjectFileMachO::getSectionForConstant(
1023     const DataLayout &DL, SectionKind Kind, const Constant *C,
1024     unsigned &Align) const {
1025   // If this constant requires a relocation, we have to put it in the data
1026   // segment, not in the text segment.
1027   if (Kind.isData() || Kind.isReadOnlyWithRel())
1028     return ConstDataSection;
1029 
1030   if (Kind.isMergeableConst4())
1031     return FourByteConstantSection;
1032   if (Kind.isMergeableConst8())
1033     return EightByteConstantSection;
1034   if (Kind.isMergeableConst16())
1035     return SixteenByteConstantSection;
1036   return ReadOnlySection;  // .const
1037 }
1038 
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const1039 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
1040     const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
1041     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
1042   // The mach-o version of this method defaults to returning a stub reference.
1043 
1044   if (Encoding & DW_EH_PE_indirect) {
1045     MachineModuleInfoMachO &MachOMMI =
1046       MMI->getObjFileInfo<MachineModuleInfoMachO>();
1047 
1048     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
1049 
1050     // Add information about the stub reference to MachOMMI so that the stub
1051     // gets emitted by the asmprinter.
1052     MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
1053     if (!StubSym.getPointer()) {
1054       MCSymbol *Sym = TM.getSymbol(GV);
1055       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
1056     }
1057 
1058     return TargetLoweringObjectFile::
1059       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
1060                         Encoding & ~DW_EH_PE_indirect, Streamer);
1061   }
1062 
1063   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
1064                                                            MMI, Streamer);
1065 }
1066 
getCFIPersonalitySymbol(const GlobalValue * GV,const TargetMachine & TM,MachineModuleInfo * MMI) const1067 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
1068     const GlobalValue *GV, const TargetMachine &TM,
1069     MachineModuleInfo *MMI) const {
1070   // The mach-o version of this method defaults to returning a stub reference.
1071   MachineModuleInfoMachO &MachOMMI =
1072     MMI->getObjFileInfo<MachineModuleInfoMachO>();
1073 
1074   MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$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 SSym;
1085 }
1086 
getIndirectSymViaGOTPCRel(const MCSymbol * Sym,const MCValue & MV,int64_t Offset,MachineModuleInfo * MMI,MCStreamer & Streamer) const1087 const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
1088     const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
1089     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
1090   // Although MachO 32-bit targets do not explicitly have a GOTPCREL relocation
1091   // as 64-bit do, we replace the GOT equivalent by accessing the final symbol
1092   // through a non_lazy_ptr stub instead. One advantage is that it allows the
1093   // computation of deltas to final external symbols. Example:
1094   //
1095   //    _extgotequiv:
1096   //       .long   _extfoo
1097   //
1098   //    _delta:
1099   //       .long   _extgotequiv-_delta
1100   //
1101   // is transformed to:
1102   //
1103   //    _delta:
1104   //       .long   L_extfoo$non_lazy_ptr-(_delta+0)
1105   //
1106   //       .section        __IMPORT,__pointers,non_lazy_symbol_pointers
1107   //    L_extfoo$non_lazy_ptr:
1108   //       .indirect_symbol        _extfoo
1109   //       .long   0
1110   //
1111   // The indirect symbol table (and sections of non_lazy_symbol_pointers type)
1112   // may point to both local (same translation unit) and global (other
1113   // translation units) symbols. Example:
1114   //
1115   // .section __DATA,__pointers,non_lazy_symbol_pointers
1116   // L1:
1117   //    .indirect_symbol _myGlobal
1118   //    .long 0
1119   // L2:
1120   //    .indirect_symbol _myLocal
1121   //    .long _myLocal
1122   //
1123   // If the symbol is local, instead of the symbol's index, the assembler
1124   // places the constant INDIRECT_SYMBOL_LOCAL into the indirect symbol table.
1125   // Then the linker will notice the constant in the table and will look at the
1126   // content of the symbol.
1127   MachineModuleInfoMachO &MachOMMI =
1128     MMI->getObjFileInfo<MachineModuleInfoMachO>();
1129   MCContext &Ctx = getContext();
1130 
1131   // The offset must consider the original displacement from the base symbol
1132   // since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
1133   Offset = -MV.getConstant();
1134   const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
1135 
1136   // Access the final symbol via sym$non_lazy_ptr and generate the appropriated
1137   // non_lazy_ptr stubs.
1138   SmallString<128> Name;
1139   StringRef Suffix = "$non_lazy_ptr";
1140   Name += MMI->getModule()->getDataLayout().getPrivateGlobalPrefix();
1141   Name += Sym->getName();
1142   Name += Suffix;
1143   MCSymbol *Stub = Ctx.getOrCreateSymbol(Name);
1144 
1145   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
1146   if (!StubSym.getPointer()) {
1147     bool IsIndirectLocal = Sym->isDefined() && !Sym->isExternal();
1148     // With the assumption that IsIndirectLocal == GV->hasLocalLinkage().
1149     StubSym = MachineModuleInfoImpl::StubValueTy(const_cast<MCSymbol *>(Sym),
1150                                                  !IsIndirectLocal);
1151   }
1152 
1153   const MCExpr *BSymExpr =
1154     MCSymbolRefExpr::create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
1155   const MCExpr *LHS =
1156     MCSymbolRefExpr::create(Stub, MCSymbolRefExpr::VK_None, Ctx);
1157 
1158   if (!Offset)
1159     return MCBinaryExpr::createSub(LHS, BSymExpr, Ctx);
1160 
1161   const MCExpr *RHS =
1162     MCBinaryExpr::createAdd(BSymExpr, MCConstantExpr::create(Offset, Ctx), Ctx);
1163   return MCBinaryExpr::createSub(LHS, RHS, Ctx);
1164 }
1165 
canUsePrivateLabel(const MCAsmInfo & AsmInfo,const MCSection & Section)1166 static bool canUsePrivateLabel(const MCAsmInfo &AsmInfo,
1167                                const MCSection &Section) {
1168   if (!AsmInfo.isSectionAtomizableBySymbols(Section))
1169     return true;
1170 
1171   // If it is not dead stripped, it is safe to use private labels.
1172   const MCSectionMachO &SMO = cast<MCSectionMachO>(Section);
1173   if (SMO.hasAttribute(MachO::S_ATTR_NO_DEAD_STRIP))
1174     return true;
1175 
1176   return false;
1177 }
1178 
getNameWithPrefix(SmallVectorImpl<char> & OutName,const GlobalValue * GV,const TargetMachine & TM) const1179 void TargetLoweringObjectFileMachO::getNameWithPrefix(
1180     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
1181     const TargetMachine &TM) const {
1182   bool CannotUsePrivateLabel = true;
1183   if (auto *GO = GV->getBaseObject()) {
1184     SectionKind GOKind = TargetLoweringObjectFile::getKindForGlobal(GO, TM);
1185     const MCSection *TheSection = SectionForGlobal(GO, GOKind, TM);
1186     CannotUsePrivateLabel =
1187         !canUsePrivateLabel(*TM.getMCAsmInfo(), *TheSection);
1188   }
1189   getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1190 }
1191 
1192 //===----------------------------------------------------------------------===//
1193 //                                  COFF
1194 //===----------------------------------------------------------------------===//
1195 
1196 static unsigned
getCOFFSectionFlags(SectionKind K,const TargetMachine & TM)1197 getCOFFSectionFlags(SectionKind K, const TargetMachine &TM) {
1198   unsigned Flags = 0;
1199   bool isThumb = TM.getTargetTriple().getArch() == Triple::thumb;
1200 
1201   if (K.isMetadata())
1202     Flags |=
1203       COFF::IMAGE_SCN_MEM_DISCARDABLE;
1204   else if (K.isText())
1205     Flags |=
1206       COFF::IMAGE_SCN_MEM_EXECUTE |
1207       COFF::IMAGE_SCN_MEM_READ |
1208       COFF::IMAGE_SCN_CNT_CODE |
1209       (isThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0);
1210   else if (K.isBSS())
1211     Flags |=
1212       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
1213       COFF::IMAGE_SCN_MEM_READ |
1214       COFF::IMAGE_SCN_MEM_WRITE;
1215   else if (K.isThreadLocal())
1216     Flags |=
1217       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1218       COFF::IMAGE_SCN_MEM_READ |
1219       COFF::IMAGE_SCN_MEM_WRITE;
1220   else if (K.isReadOnly() || K.isReadOnlyWithRel())
1221     Flags |=
1222       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1223       COFF::IMAGE_SCN_MEM_READ;
1224   else if (K.isWriteable())
1225     Flags |=
1226       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1227       COFF::IMAGE_SCN_MEM_READ |
1228       COFF::IMAGE_SCN_MEM_WRITE;
1229 
1230   return Flags;
1231 }
1232 
getComdatGVForCOFF(const GlobalValue * GV)1233 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
1234   const Comdat *C = GV->getComdat();
1235   assert(C && "expected GV to have a Comdat!");
1236 
1237   StringRef ComdatGVName = C->getName();
1238   const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
1239   if (!ComdatGV)
1240     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
1241                        "' does not exist.");
1242 
1243   if (ComdatGV->getComdat() != C)
1244     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
1245                        "' is not a key for its COMDAT.");
1246 
1247   return ComdatGV;
1248 }
1249 
getSelectionForCOFF(const GlobalValue * GV)1250 static int getSelectionForCOFF(const GlobalValue *GV) {
1251   if (const Comdat *C = GV->getComdat()) {
1252     const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
1253     if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
1254       ComdatKey = GA->getBaseObject();
1255     if (ComdatKey == GV) {
1256       switch (C->getSelectionKind()) {
1257       case Comdat::Any:
1258         return COFF::IMAGE_COMDAT_SELECT_ANY;
1259       case Comdat::ExactMatch:
1260         return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
1261       case Comdat::Largest:
1262         return COFF::IMAGE_COMDAT_SELECT_LARGEST;
1263       case Comdat::NoDuplicates:
1264         return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1265       case Comdat::SameSize:
1266         return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
1267       }
1268     } else {
1269       return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
1270     }
1271   }
1272   return 0;
1273 }
1274 
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const1275 MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
1276     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1277   int Selection = 0;
1278   unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1279   StringRef Name = GO->getSection();
1280   StringRef COMDATSymName = "";
1281   if (GO->hasComdat()) {
1282     Selection = getSelectionForCOFF(GO);
1283     const GlobalValue *ComdatGV;
1284     if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
1285       ComdatGV = getComdatGVForCOFF(GO);
1286     else
1287       ComdatGV = GO;
1288 
1289     if (!ComdatGV->hasPrivateLinkage()) {
1290       MCSymbol *Sym = TM.getSymbol(ComdatGV);
1291       COMDATSymName = Sym->getName();
1292       Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1293     } else {
1294       Selection = 0;
1295     }
1296   }
1297 
1298   return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
1299                                      Selection);
1300 }
1301 
getCOFFSectionNameForUniqueGlobal(SectionKind Kind)1302 static StringRef getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
1303   if (Kind.isText())
1304     return ".text";
1305   if (Kind.isBSS())
1306     return ".bss";
1307   if (Kind.isThreadLocal())
1308     return ".tls$";
1309   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1310     return ".rdata";
1311   return ".data";
1312 }
1313 
SelectSectionForGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const1314 MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
1315     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1316   // If we have -ffunction-sections then we should emit the global value to a
1317   // uniqued section specifically for it.
1318   bool EmitUniquedSection;
1319   if (Kind.isText())
1320     EmitUniquedSection = TM.getFunctionSections();
1321   else
1322     EmitUniquedSection = TM.getDataSections();
1323 
1324   if ((EmitUniquedSection && !Kind.isCommon()) || GO->hasComdat()) {
1325     SmallString<256> Name = getCOFFSectionNameForUniqueGlobal(Kind);
1326 
1327     unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1328 
1329     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1330     int Selection = getSelectionForCOFF(GO);
1331     if (!Selection)
1332       Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1333     const GlobalValue *ComdatGV;
1334     if (GO->hasComdat())
1335       ComdatGV = getComdatGVForCOFF(GO);
1336     else
1337       ComdatGV = GO;
1338 
1339     unsigned UniqueID = MCContext::GenericSectionID;
1340     if (EmitUniquedSection)
1341       UniqueID = NextUniqueID++;
1342 
1343     if (!ComdatGV->hasPrivateLinkage()) {
1344       MCSymbol *Sym = TM.getSymbol(ComdatGV);
1345       StringRef COMDATSymName = Sym->getName();
1346 
1347       // Append "$symbol" to the section name *before* IR-level mangling is
1348       // applied when targetting mingw. This is what GCC does, and the ld.bfd
1349       // COFF linker will not properly handle comdats otherwise.
1350       if (getTargetTriple().isWindowsGNUEnvironment())
1351         raw_svector_ostream(Name) << '$' << ComdatGV->getName();
1352 
1353       return getContext().getCOFFSection(Name, Characteristics, Kind,
1354                                          COMDATSymName, Selection, UniqueID);
1355     } else {
1356       SmallString<256> TmpData;
1357       getMangler().getNameWithPrefix(TmpData, GO, /*CannotUsePrivateLabel=*/true);
1358       return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
1359                                          Selection, UniqueID);
1360     }
1361   }
1362 
1363   if (Kind.isText())
1364     return TextSection;
1365 
1366   if (Kind.isThreadLocal())
1367     return TLSDataSection;
1368 
1369   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1370     return ReadOnlySection;
1371 
1372   // Note: we claim that common symbols are put in BSSSection, but they are
1373   // really emitted with the magic .comm directive, which creates a symbol table
1374   // entry but not a section.
1375   if (Kind.isBSS() || Kind.isCommon())
1376     return BSSSection;
1377 
1378   return DataSection;
1379 }
1380 
getNameWithPrefix(SmallVectorImpl<char> & OutName,const GlobalValue * GV,const TargetMachine & TM) const1381 void TargetLoweringObjectFileCOFF::getNameWithPrefix(
1382     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
1383     const TargetMachine &TM) const {
1384   bool CannotUsePrivateLabel = false;
1385   if (GV->hasPrivateLinkage() &&
1386       ((isa<Function>(GV) && TM.getFunctionSections()) ||
1387        (isa<GlobalVariable>(GV) && TM.getDataSections())))
1388     CannotUsePrivateLabel = true;
1389 
1390   getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1391 }
1392 
getSectionForJumpTable(const Function & F,const TargetMachine & TM) const1393 MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
1394     const Function &F, const TargetMachine &TM) const {
1395   // If the function can be removed, produce a unique section so that
1396   // the table doesn't prevent the removal.
1397   const Comdat *C = F.getComdat();
1398   bool EmitUniqueSection = TM.getFunctionSections() || C;
1399   if (!EmitUniqueSection)
1400     return ReadOnlySection;
1401 
1402   // FIXME: we should produce a symbol for F instead.
1403   if (F.hasPrivateLinkage())
1404     return ReadOnlySection;
1405 
1406   MCSymbol *Sym = TM.getSymbol(&F);
1407   StringRef COMDATSymName = Sym->getName();
1408 
1409   SectionKind Kind = SectionKind::getReadOnly();
1410   StringRef SecName = getCOFFSectionNameForUniqueGlobal(Kind);
1411   unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1412   Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1413   unsigned UniqueID = NextUniqueID++;
1414 
1415   return getContext().getCOFFSection(
1416       SecName, Characteristics, Kind, COMDATSymName,
1417       COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
1418 }
1419 
emitModuleMetadata(MCStreamer & Streamer,Module & M) const1420 void TargetLoweringObjectFileCOFF::emitModuleMetadata(MCStreamer &Streamer,
1421                                                       Module &M) const {
1422   if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
1423     // Emit the linker options to the linker .drectve section.  According to the
1424     // spec, this section is a space-separated string containing flags for
1425     // linker.
1426     MCSection *Sec = getDrectveSection();
1427     Streamer.SwitchSection(Sec);
1428     for (const auto &Option : LinkerOptions->operands()) {
1429       for (const auto &Piece : cast<MDNode>(Option)->operands()) {
1430         // Lead with a space for consistency with our dllexport implementation.
1431         std::string Directive(" ");
1432         Directive.append(cast<MDString>(Piece)->getString());
1433         Streamer.EmitBytes(Directive);
1434       }
1435     }
1436   }
1437 
1438   unsigned Version = 0;
1439   unsigned Flags = 0;
1440   StringRef Section;
1441 
1442   GetObjCImageInfo(M, Version, Flags, Section);
1443   if (Section.empty())
1444     return;
1445 
1446   auto &C = getContext();
1447   auto *S = C.getCOFFSection(
1448       Section, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
1449       SectionKind::getReadOnly());
1450   Streamer.SwitchSection(S);
1451   Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
1452   Streamer.EmitIntValue(Version, 4);
1453   Streamer.EmitIntValue(Flags, 4);
1454   Streamer.AddBlankLine();
1455 }
1456 
Initialize(MCContext & Ctx,const TargetMachine & TM)1457 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
1458                                               const TargetMachine &TM) {
1459   TargetLoweringObjectFile::Initialize(Ctx, TM);
1460   const Triple &T = TM.getTargetTriple();
1461   if (T.isKnownWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
1462     StaticCtorSection =
1463         Ctx.getCOFFSection(".CRT$XCU", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1464                                            COFF::IMAGE_SCN_MEM_READ,
1465                            SectionKind::getReadOnly());
1466     StaticDtorSection =
1467         Ctx.getCOFFSection(".CRT$XTX", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1468                                            COFF::IMAGE_SCN_MEM_READ,
1469                            SectionKind::getReadOnly());
1470   } else {
1471     StaticCtorSection = Ctx.getCOFFSection(
1472         ".ctors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1473                       COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1474         SectionKind::getData());
1475     StaticDtorSection = Ctx.getCOFFSection(
1476         ".dtors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1477                       COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1478         SectionKind::getData());
1479   }
1480 }
1481 
getCOFFStaticStructorSection(MCContext & Ctx,const Triple & T,bool IsCtor,unsigned Priority,const MCSymbol * KeySym,MCSectionCOFF * Default)1482 static MCSectionCOFF *getCOFFStaticStructorSection(MCContext &Ctx,
1483                                                    const Triple &T, bool IsCtor,
1484                                                    unsigned Priority,
1485                                                    const MCSymbol *KeySym,
1486                                                    MCSectionCOFF *Default) {
1487   if (T.isKnownWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
1488     // If the priority is the default, use .CRT$XCU, possibly associative.
1489     if (Priority == 65535)
1490       return Ctx.getAssociativeCOFFSection(Default, KeySym, 0);
1491 
1492     // Otherwise, we need to compute a new section name. Low priorities should
1493     // run earlier. The linker will sort sections ASCII-betically, and we need a
1494     // string that sorts between .CRT$XCA and .CRT$XCU. In the general case, we
1495     // make a name like ".CRT$XCT12345", since that runs before .CRT$XCU. Really
1496     // low priorities need to sort before 'L', since the CRT uses that
1497     // internally, so we use ".CRT$XCA00001" for them.
1498     SmallString<24> Name;
1499     raw_svector_ostream OS(Name);
1500     OS << ".CRT$XC" << (Priority < 200 ? 'A' : 'T') << format("%05u", Priority);
1501     MCSectionCOFF *Sec = Ctx.getCOFFSection(
1502         Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
1503         SectionKind::getReadOnly());
1504     return Ctx.getAssociativeCOFFSection(Sec, KeySym, 0);
1505   }
1506 
1507   std::string Name = IsCtor ? ".ctors" : ".dtors";
1508   if (Priority != 65535)
1509     raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
1510 
1511   return Ctx.getAssociativeCOFFSection(
1512       Ctx.getCOFFSection(Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1513                                    COFF::IMAGE_SCN_MEM_READ |
1514                                    COFF::IMAGE_SCN_MEM_WRITE,
1515                          SectionKind::getData()),
1516       KeySym, 0);
1517 }
1518 
getStaticCtorSection(unsigned Priority,const MCSymbol * KeySym) const1519 MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
1520     unsigned Priority, const MCSymbol *KeySym) const {
1521   return getCOFFStaticStructorSection(getContext(), getTargetTriple(), true,
1522                                       Priority, KeySym,
1523                                       cast<MCSectionCOFF>(StaticCtorSection));
1524 }
1525 
getStaticDtorSection(unsigned Priority,const MCSymbol * KeySym) const1526 MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
1527     unsigned Priority, const MCSymbol *KeySym) const {
1528   return getCOFFStaticStructorSection(getContext(), getTargetTriple(), false,
1529                                       Priority, KeySym,
1530                                       cast<MCSectionCOFF>(StaticDtorSection));
1531 }
1532 
emitLinkerFlagsForGlobal(raw_ostream & OS,const GlobalValue * GV) const1533 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
1534     raw_ostream &OS, const GlobalValue *GV) const {
1535   emitLinkerFlagsForGlobalCOFF(OS, GV, getTargetTriple(), getMangler());
1536 }
1537 
emitLinkerFlagsForUsed(raw_ostream & OS,const GlobalValue * GV) const1538 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForUsed(
1539     raw_ostream &OS, const GlobalValue *GV) const {
1540   emitLinkerFlagsForUsedCOFF(OS, GV, getTargetTriple(), getMangler());
1541 }
1542 
lowerRelativeReference(const GlobalValue * LHS,const GlobalValue * RHS,const TargetMachine & TM) const1543 const MCExpr *TargetLoweringObjectFileCOFF::lowerRelativeReference(
1544     const GlobalValue *LHS, const GlobalValue *RHS,
1545     const TargetMachine &TM) const {
1546   const Triple &T = TM.getTargetTriple();
1547   if (!T.isKnownWindowsMSVCEnvironment() &&
1548       !T.isWindowsItaniumEnvironment() &&
1549       !T.isWindowsCoreCLREnvironment())
1550     return nullptr;
1551 
1552   // Our symbols should exist in address space zero, cowardly no-op if
1553   // otherwise.
1554   if (LHS->getType()->getPointerAddressSpace() != 0 ||
1555       RHS->getType()->getPointerAddressSpace() != 0)
1556     return nullptr;
1557 
1558   // Both ptrtoint instructions must wrap global objects:
1559   // - Only global variables are eligible for image relative relocations.
1560   // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
1561   // We expect __ImageBase to be a global variable without a section, externally
1562   // defined.
1563   //
1564   // It should look something like this: @__ImageBase = external constant i8
1565   if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) ||
1566       LHS->isThreadLocal() || RHS->isThreadLocal() ||
1567       RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() ||
1568       cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection())
1569     return nullptr;
1570 
1571   return MCSymbolRefExpr::create(TM.getSymbol(LHS),
1572                                  MCSymbolRefExpr::VK_COFF_IMGREL32,
1573                                  getContext());
1574 }
1575 
APIntToHexString(const APInt & AI)1576 static std::string APIntToHexString(const APInt &AI) {
1577   unsigned Width = (AI.getBitWidth() / 8) * 2;
1578   std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true);
1579   unsigned Size = HexString.size();
1580   assert(Width >= Size && "hex string is too large!");
1581   HexString.insert(HexString.begin(), Width - Size, '0');
1582 
1583   return HexString;
1584 }
1585 
scalarConstantToHexString(const Constant * C)1586 static std::string scalarConstantToHexString(const Constant *C) {
1587   Type *Ty = C->getType();
1588   if (isa<UndefValue>(C)) {
1589     return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits()));
1590   } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) {
1591     return APIntToHexString(CFP->getValueAPF().bitcastToAPInt());
1592   } else if (const auto *CI = dyn_cast<ConstantInt>(C)) {
1593     return APIntToHexString(CI->getValue());
1594   } else {
1595     unsigned NumElements;
1596     if (isa<VectorType>(Ty))
1597       NumElements = Ty->getVectorNumElements();
1598     else
1599       NumElements = Ty->getArrayNumElements();
1600     std::string HexString;
1601     for (int I = NumElements - 1, E = -1; I != E; --I)
1602       HexString += scalarConstantToHexString(C->getAggregateElement(I));
1603     return HexString;
1604   }
1605 }
1606 
getSectionForConstant(const DataLayout & DL,SectionKind Kind,const Constant * C,unsigned & Align) const1607 MCSection *TargetLoweringObjectFileCOFF::getSectionForConstant(
1608     const DataLayout &DL, SectionKind Kind, const Constant *C,
1609     unsigned &Align) const {
1610   if (Kind.isMergeableConst() && C &&
1611       getContext().getAsmInfo()->hasCOFFComdatConstants()) {
1612     // This creates comdat sections with the given symbol name, but unless
1613     // AsmPrinter::GetCPISymbol actually makes the symbol global, the symbol
1614     // will be created with a null storage class, which makes GNU binutils
1615     // error out.
1616     const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1617                                      COFF::IMAGE_SCN_MEM_READ |
1618                                      COFF::IMAGE_SCN_LNK_COMDAT;
1619     std::string COMDATSymName;
1620     if (Kind.isMergeableConst4()) {
1621       if (Align <= 4) {
1622         COMDATSymName = "__real@" + scalarConstantToHexString(C);
1623         Align = 4;
1624       }
1625     } else if (Kind.isMergeableConst8()) {
1626       if (Align <= 8) {
1627         COMDATSymName = "__real@" + scalarConstantToHexString(C);
1628         Align = 8;
1629       }
1630     } else if (Kind.isMergeableConst16()) {
1631       // FIXME: These may not be appropriate for non-x86 architectures.
1632       if (Align <= 16) {
1633         COMDATSymName = "__xmm@" + scalarConstantToHexString(C);
1634         Align = 16;
1635       }
1636     } else if (Kind.isMergeableConst32()) {
1637       if (Align <= 32) {
1638         COMDATSymName = "__ymm@" + scalarConstantToHexString(C);
1639         Align = 32;
1640       }
1641     }
1642 
1643     if (!COMDATSymName.empty())
1644       return getContext().getCOFFSection(".rdata", Characteristics, Kind,
1645                                          COMDATSymName,
1646                                          COFF::IMAGE_COMDAT_SELECT_ANY);
1647   }
1648 
1649   return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C, Align);
1650 }
1651 
1652 
1653 //===----------------------------------------------------------------------===//
1654 //                                  Wasm
1655 //===----------------------------------------------------------------------===//
1656 
getWasmComdat(const GlobalValue * GV)1657 static const Comdat *getWasmComdat(const GlobalValue *GV) {
1658   const Comdat *C = GV->getComdat();
1659   if (!C)
1660     return nullptr;
1661 
1662   if (C->getSelectionKind() != Comdat::Any)
1663     report_fatal_error("WebAssembly COMDATs only support "
1664                        "SelectionKind::Any, '" + C->getName() + "' cannot be "
1665                        "lowered.");
1666 
1667   return C;
1668 }
1669 
getWasmKindForNamedSection(StringRef Name,SectionKind K)1670 static SectionKind getWasmKindForNamedSection(StringRef Name, SectionKind K) {
1671   // If we're told we have function data, then use that.
1672   if (K.isText())
1673     return SectionKind::getText();
1674 
1675   // Otherwise, ignore whatever section type the generic impl detected and use
1676   // a plain data section.
1677   return SectionKind::getData();
1678 }
1679 
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const1680 MCSection *TargetLoweringObjectFileWasm::getExplicitSectionGlobal(
1681     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1682   // We don't support explict section names for functions in the wasm object
1683   // format.  Each function has to be in its own unique section.
1684   if (isa<Function>(GO)) {
1685     return SelectSectionForGlobal(GO, Kind, TM);
1686   }
1687 
1688   StringRef Name = GO->getSection();
1689 
1690   Kind = getWasmKindForNamedSection(Name, Kind);
1691 
1692   StringRef Group = "";
1693   if (const Comdat *C = getWasmComdat(GO)) {
1694     Group = C->getName();
1695   }
1696 
1697   return getContext().getWasmSection(Name, Kind, Group,
1698                                      MCContext::GenericSectionID);
1699 }
1700 
selectWasmSectionForGlobal(MCContext & Ctx,const GlobalObject * GO,SectionKind Kind,Mangler & Mang,const TargetMachine & TM,bool EmitUniqueSection,unsigned * NextUniqueID)1701 static MCSectionWasm *selectWasmSectionForGlobal(
1702     MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
1703     const TargetMachine &TM, bool EmitUniqueSection, unsigned *NextUniqueID) {
1704   StringRef Group = "";
1705   if (const Comdat *C = getWasmComdat(GO)) {
1706     Group = C->getName();
1707   }
1708 
1709   bool UniqueSectionNames = TM.getUniqueSectionNames();
1710   SmallString<128> Name = getSectionPrefixForGlobal(Kind);
1711 
1712   if (const auto *F = dyn_cast<Function>(GO)) {
1713     const auto &OptionalPrefix = F->getSectionPrefix();
1714     if (OptionalPrefix)
1715       Name += *OptionalPrefix;
1716   }
1717 
1718   if (EmitUniqueSection && UniqueSectionNames) {
1719     Name.push_back('.');
1720     TM.getNameWithPrefix(Name, GO, Mang, true);
1721   }
1722   unsigned UniqueID = MCContext::GenericSectionID;
1723   if (EmitUniqueSection && !UniqueSectionNames) {
1724     UniqueID = *NextUniqueID;
1725     (*NextUniqueID)++;
1726   }
1727   return Ctx.getWasmSection(Name, Kind, Group, UniqueID);
1728 }
1729 
SelectSectionForGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const1730 MCSection *TargetLoweringObjectFileWasm::SelectSectionForGlobal(
1731     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1732 
1733   if (Kind.isCommon())
1734     report_fatal_error("mergable sections not supported yet on wasm");
1735 
1736   // If we have -ffunction-section or -fdata-section then we should emit the
1737   // global value to a uniqued section specifically for it.
1738   bool EmitUniqueSection = false;
1739   if (Kind.isText())
1740     EmitUniqueSection = TM.getFunctionSections();
1741   else
1742     EmitUniqueSection = TM.getDataSections();
1743   EmitUniqueSection |= GO->hasComdat();
1744 
1745   return selectWasmSectionForGlobal(getContext(), GO, Kind, getMangler(), TM,
1746                                     EmitUniqueSection, &NextUniqueID);
1747 }
1748 
shouldPutJumpTableInFunctionSection(bool UsesLabelDifference,const Function & F) const1749 bool TargetLoweringObjectFileWasm::shouldPutJumpTableInFunctionSection(
1750     bool UsesLabelDifference, const Function &F) const {
1751   // We can always create relative relocations, so use another section
1752   // that can be marked non-executable.
1753   return false;
1754 }
1755 
lowerRelativeReference(const GlobalValue * LHS,const GlobalValue * RHS,const TargetMachine & TM) const1756 const MCExpr *TargetLoweringObjectFileWasm::lowerRelativeReference(
1757     const GlobalValue *LHS, const GlobalValue *RHS,
1758     const TargetMachine &TM) const {
1759   // We may only use a PLT-relative relocation to refer to unnamed_addr
1760   // functions.
1761   if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
1762     return nullptr;
1763 
1764   // Basic sanity checks.
1765   if (LHS->getType()->getPointerAddressSpace() != 0 ||
1766       RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
1767       RHS->isThreadLocal())
1768     return nullptr;
1769 
1770   return MCBinaryExpr::createSub(
1771       MCSymbolRefExpr::create(TM.getSymbol(LHS), MCSymbolRefExpr::VK_None,
1772                               getContext()),
1773       MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
1774 }
1775 
InitializeWasm()1776 void TargetLoweringObjectFileWasm::InitializeWasm() {
1777   StaticCtorSection =
1778       getContext().getWasmSection(".init_array", SectionKind::getData());
1779 
1780   // We don't use PersonalityEncoding and LSDAEncoding because we don't emit
1781   // .cfi directives. We use TTypeEncoding to encode typeinfo global variables.
1782   TTypeEncoding = dwarf::DW_EH_PE_absptr;
1783 }
1784 
getStaticCtorSection(unsigned Priority,const MCSymbol * KeySym) const1785 MCSection *TargetLoweringObjectFileWasm::getStaticCtorSection(
1786     unsigned Priority, const MCSymbol *KeySym) const {
1787   return Priority == UINT16_MAX ?
1788          StaticCtorSection :
1789          getContext().getWasmSection(".init_array." + utostr(Priority),
1790                                      SectionKind::getData());
1791 }
1792 
getStaticDtorSection(unsigned Priority,const MCSymbol * KeySym) const1793 MCSection *TargetLoweringObjectFileWasm::getStaticDtorSection(
1794     unsigned Priority, const MCSymbol *KeySym) const {
1795   llvm_unreachable("@llvm.global_dtors should have been lowered already");
1796   return nullptr;
1797 }
1798