xref: /llvm-project/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (revision aef3659e1888753ffe03510c513e1a2d9101a795) 
1 //===-- llvm/CodeGen/TargetLoweringObjectFileImpl.cpp - Object File Info --===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements classes used to handle lowerings specific to common
11 // object file formats.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
16 #include "llvm/ADT/SmallString.h"
17 #include "llvm/ADT/StringExtras.h"
18 #include "llvm/ADT/Triple.h"
19 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
20 #include "llvm/IR/Constants.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/IR/DerivedTypes.h"
23 #include "llvm/IR/Function.h"
24 #include "llvm/IR/GlobalVariable.h"
25 #include "llvm/IR/Mangler.h"
26 #include "llvm/IR/Module.h"
27 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/MCExpr.h"
29 #include "llvm/MC/MCSectionCOFF.h"
30 #include "llvm/MC/MCSectionELF.h"
31 #include "llvm/MC/MCSectionMachO.h"
32 #include "llvm/MC/MCStreamer.h"
33 #include "llvm/MC/MCSymbolELF.h"
34 #include "llvm/MC/MCValue.h"
35 #include "llvm/Support/Dwarf.h"
36 #include "llvm/Support/ELF.h"
37 #include "llvm/Support/ErrorHandling.h"
38 #include "llvm/Support/raw_ostream.h"
39 #include "llvm/Target/TargetLowering.h"
40 #include "llvm/Target/TargetMachine.h"
41 #include "llvm/Target/TargetSubtargetInfo.h"
42 using namespace llvm;
43 using namespace dwarf;
44 
45 //===----------------------------------------------------------------------===//
46 //                                  ELF
47 //===----------------------------------------------------------------------===//
48 
49 MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
50     const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
51     MachineModuleInfo *MMI) const {
52   unsigned Encoding = getPersonalityEncoding();
53   if ((Encoding & 0x80) == dwarf::DW_EH_PE_indirect)
54     return getContext().getOrCreateSymbol(StringRef("DW.ref.") +
55                                           TM.getSymbol(GV, Mang)->getName());
56   if ((Encoding & 0x70) == dwarf::DW_EH_PE_absptr)
57     return TM.getSymbol(GV, Mang);
58   report_fatal_error("We do not support this DWARF encoding yet!");
59 }
60 
61 void TargetLoweringObjectFileELF::emitPersonalityValue(MCStreamer &Streamer,
62                                                        const TargetMachine &TM,
63                                                        const MCSymbol *Sym) const {
64   SmallString<64> NameData("DW.ref.");
65   NameData += Sym->getName();
66   MCSymbolELF *Label =
67       cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
68   Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
69   Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
70   StringRef Prefix = ".data.";
71   NameData.insert(NameData.begin(), Prefix.begin(), Prefix.end());
72   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
73   MCSection *Sec = getContext().getELFSection(NameData, ELF::SHT_PROGBITS,
74                                               Flags, 0, Label->getName());
75   unsigned Size = TM.getDataLayout()->getPointerSize();
76   Streamer.SwitchSection(Sec);
77   Streamer.EmitValueToAlignment(TM.getDataLayout()->getPointerABIAlignment());
78   Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
79   const MCExpr *E = MCConstantExpr::create(Size, getContext());
80   Streamer.emitELFSize(Label, E);
81   Streamer.EmitLabel(Label);
82 
83   Streamer.EmitSymbolValue(Sym, Size);
84 }
85 
86 const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
87     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
88     const TargetMachine &TM, MachineModuleInfo *MMI,
89     MCStreamer &Streamer) const {
90 
91   if (Encoding & dwarf::DW_EH_PE_indirect) {
92     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
93 
94     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", Mang, TM);
95 
96     // Add information about the stub reference to ELFMMI so that the stub
97     // gets emitted by the asmprinter.
98     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
99     if (!StubSym.getPointer()) {
100       MCSymbol *Sym = TM.getSymbol(GV, Mang);
101       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
102     }
103 
104     return TargetLoweringObjectFile::
105       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
106                         Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
107   }
108 
109   return TargetLoweringObjectFile::
110     getTTypeGlobalReference(GV, Encoding, Mang, TM, MMI, Streamer);
111 }
112 
113 static SectionKind
114 getELFKindForNamedSection(StringRef Name, SectionKind K) {
115   // N.B.: The defaults used in here are no the same ones used in MC.
116   // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
117   // both gas and MC will produce a section with no flags. Given
118   // section(".eh_frame") gcc will produce:
119   //
120   //   .section   .eh_frame,"a",@progbits
121   if (Name.empty() || Name[0] != '.') return K;
122 
123   // Some lame default implementation based on some magic section names.
124   if (Name == ".bss" ||
125       Name.startswith(".bss.") ||
126       Name.startswith(".gnu.linkonce.b.") ||
127       Name.startswith(".llvm.linkonce.b.") ||
128       Name == ".sbss" ||
129       Name.startswith(".sbss.") ||
130       Name.startswith(".gnu.linkonce.sb.") ||
131       Name.startswith(".llvm.linkonce.sb."))
132     return SectionKind::getBSS();
133 
134   if (Name == ".tdata" ||
135       Name.startswith(".tdata.") ||
136       Name.startswith(".gnu.linkonce.td.") ||
137       Name.startswith(".llvm.linkonce.td."))
138     return SectionKind::getThreadData();
139 
140   if (Name == ".tbss" ||
141       Name.startswith(".tbss.") ||
142       Name.startswith(".gnu.linkonce.tb.") ||
143       Name.startswith(".llvm.linkonce.tb."))
144     return SectionKind::getThreadBSS();
145 
146   return K;
147 }
148 
149 
150 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
151 
152   if (Name == ".init_array")
153     return ELF::SHT_INIT_ARRAY;
154 
155   if (Name == ".fini_array")
156     return ELF::SHT_FINI_ARRAY;
157 
158   if (Name == ".preinit_array")
159     return ELF::SHT_PREINIT_ARRAY;
160 
161   if (K.isBSS() || K.isThreadBSS())
162     return ELF::SHT_NOBITS;
163 
164   return ELF::SHT_PROGBITS;
165 }
166 
167 static unsigned getELFSectionFlags(SectionKind K) {
168   unsigned Flags = 0;
169 
170   if (!K.isMetadata())
171     Flags |= ELF::SHF_ALLOC;
172 
173   if (K.isText())
174     Flags |= ELF::SHF_EXECINSTR;
175 
176   if (K.isWriteable())
177     Flags |= ELF::SHF_WRITE;
178 
179   if (K.isThreadLocal())
180     Flags |= ELF::SHF_TLS;
181 
182   if (K.isMergeableCString() || K.isMergeableConst())
183     Flags |= ELF::SHF_MERGE;
184 
185   if (K.isMergeableCString())
186     Flags |= ELF::SHF_STRINGS;
187 
188   return Flags;
189 }
190 
191 static const Comdat *getELFComdat(const GlobalValue *GV) {
192   const Comdat *C = GV->getComdat();
193   if (!C)
194     return nullptr;
195 
196   if (C->getSelectionKind() != Comdat::Any)
197     report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
198                        C->getName() + "' cannot be lowered.");
199 
200   return C;
201 }
202 
203 MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
204     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
205     const TargetMachine &TM) const {
206   StringRef SectionName = GV->getSection();
207 
208   // Infer section flags from the section name if we can.
209   Kind = getELFKindForNamedSection(SectionName, Kind);
210 
211   StringRef Group = "";
212   unsigned Flags = getELFSectionFlags(Kind);
213   if (const Comdat *C = getELFComdat(GV)) {
214     Group = C->getName();
215     Flags |= ELF::SHF_GROUP;
216   }
217   return getContext().getELFSection(SectionName,
218                                     getELFSectionType(SectionName, Kind), Flags,
219                                     /*EntrySize=*/0, Group);
220 }
221 
222 /// Return the section prefix name used by options FunctionsSections and
223 /// DataSections.
224 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
225   if (Kind.isText())
226     return ".text";
227   if (Kind.isReadOnly())
228     return ".rodata";
229   if (Kind.isBSS())
230     return ".bss";
231   if (Kind.isThreadData())
232     return ".tdata";
233   if (Kind.isThreadBSS())
234     return ".tbss";
235   if (Kind.isDataNoRel())
236     return ".data";
237   if (Kind.isDataRelLocal())
238     return ".data.rel.local";
239   if (Kind.isDataRel())
240     return ".data.rel";
241   if (Kind.isReadOnlyWithRelLocal())
242     return ".data.rel.ro.local";
243   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
244   return ".data.rel.ro";
245 }
246 
247 static MCSectionELF *
248 selectELFSectionForGlobal(MCContext &Ctx, const GlobalValue *GV,
249                           SectionKind Kind, Mangler &Mang,
250                           const TargetMachine &TM, bool EmitUniqueSection,
251                           unsigned Flags, unsigned *NextUniqueID) {
252   unsigned EntrySize = 0;
253   if (Kind.isMergeableCString()) {
254     if (Kind.isMergeable2ByteCString()) {
255       EntrySize = 2;
256     } else if (Kind.isMergeable4ByteCString()) {
257       EntrySize = 4;
258     } else {
259       EntrySize = 1;
260       assert(Kind.isMergeable1ByteCString() && "unknown string width");
261     }
262   } else if (Kind.isMergeableConst()) {
263     if (Kind.isMergeableConst4()) {
264       EntrySize = 4;
265     } else if (Kind.isMergeableConst8()) {
266       EntrySize = 8;
267     } else {
268       assert(Kind.isMergeableConst16() && "unknown data width");
269       EntrySize = 16;
270     }
271   }
272 
273   StringRef Group = "";
274   if (const Comdat *C = getELFComdat(GV)) {
275     Flags |= ELF::SHF_GROUP;
276     Group = C->getName();
277   }
278 
279   bool UniqueSectionNames = TM.getUniqueSectionNames();
280   SmallString<128> Name;
281   if (Kind.isMergeableCString()) {
282     // We also need alignment here.
283     // FIXME: this is getting the alignment of the character, not the
284     // alignment of the global!
285     unsigned Align =
286         TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV));
287 
288     std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
289     Name = SizeSpec + utostr(Align);
290   } else if (Kind.isMergeableConst()) {
291     Name = ".rodata.cst";
292     Name += utostr(EntrySize);
293   } else {
294     Name = getSectionPrefixForGlobal(Kind);
295   }
296 
297   if (EmitUniqueSection && UniqueSectionNames) {
298     Name.push_back('.');
299     TM.getNameWithPrefix(Name, GV, Mang, true);
300   }
301   unsigned UniqueID = ~0;
302   if (EmitUniqueSection && !UniqueSectionNames) {
303     UniqueID = *NextUniqueID;
304     (*NextUniqueID)++;
305   }
306   return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags,
307                            EntrySize, Group, UniqueID);
308 }
309 
310 MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
311     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
312     const TargetMachine &TM) const {
313   unsigned Flags = getELFSectionFlags(Kind);
314 
315   // If we have -ffunction-section or -fdata-section then we should emit the
316   // global value to a uniqued section specifically for it.
317   bool EmitUniqueSection = false;
318   if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
319     if (Kind.isText())
320       EmitUniqueSection = TM.getFunctionSections();
321     else
322       EmitUniqueSection = TM.getDataSections();
323   }
324   EmitUniqueSection |= GV->hasComdat();
325 
326   return selectELFSectionForGlobal(getContext(), GV, Kind, Mang, TM,
327                                    EmitUniqueSection, Flags, &NextUniqueID);
328 }
329 
330 MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
331     const Function &F, Mangler &Mang, const TargetMachine &TM) const {
332   // If the function can be removed, produce a unique section so that
333   // the table doesn't prevent the removal.
334   const Comdat *C = F.getComdat();
335   bool EmitUniqueSection = TM.getFunctionSections() || C;
336   if (!EmitUniqueSection)
337     return ReadOnlySection;
338 
339   return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
340                                    Mang, TM, EmitUniqueSection, ELF::SHF_ALLOC,
341                                    &NextUniqueID);
342 }
343 
344 bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
345     bool UsesLabelDifference, const Function &F) const {
346   // We can always create relative relocations, so use another section
347   // that can be marked non-executable.
348   return false;
349 }
350 
351 /// Given a mergeable constant with the specified size and relocation
352 /// information, return a section that it should be placed in.
353 MCSection *
354 TargetLoweringObjectFileELF::getSectionForConstant(SectionKind Kind,
355                                                    const Constant *C) const {
356   if (Kind.isMergeableConst4() && MergeableConst4Section)
357     return MergeableConst4Section;
358   if (Kind.isMergeableConst8() && MergeableConst8Section)
359     return MergeableConst8Section;
360   if (Kind.isMergeableConst16() && MergeableConst16Section)
361     return MergeableConst16Section;
362   if (Kind.isReadOnly())
363     return ReadOnlySection;
364 
365   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
366   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
367   return DataRelROSection;
368 }
369 
370 static MCSectionELF *getStaticStructorSection(MCContext &Ctx, bool UseInitArray,
371                                               bool IsCtor, unsigned Priority,
372                                               const MCSymbol *KeySym) {
373   std::string Name;
374   unsigned Type;
375   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
376   StringRef COMDAT = KeySym ? KeySym->getName() : "";
377 
378   if (KeySym)
379     Flags |= ELF::SHF_GROUP;
380 
381   if (UseInitArray) {
382     if (IsCtor) {
383       Type = ELF::SHT_INIT_ARRAY;
384       Name = ".init_array";
385     } else {
386       Type = ELF::SHT_FINI_ARRAY;
387       Name = ".fini_array";
388     }
389     if (Priority != 65535) {
390       Name += '.';
391       Name += utostr(Priority);
392     }
393   } else {
394     // The default scheme is .ctor / .dtor, so we have to invert the priority
395     // numbering.
396     if (IsCtor)
397       Name = ".ctors";
398     else
399       Name = ".dtors";
400     if (Priority != 65535) {
401       Name += '.';
402       Name += utostr(65535 - Priority);
403     }
404     Type = ELF::SHT_PROGBITS;
405   }
406 
407   return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
408 }
409 
410 MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
411     unsigned Priority, const MCSymbol *KeySym) const {
412   return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
413                                   KeySym);
414 }
415 
416 MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
417     unsigned Priority, const MCSymbol *KeySym) const {
418   return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
419                                   KeySym);
420 }
421 
422 void
423 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
424   UseInitArray = UseInitArray_;
425   if (!UseInitArray)
426     return;
427 
428   StaticCtorSection = getContext().getELFSection(
429       ".init_array", ELF::SHT_INIT_ARRAY, ELF::SHF_WRITE | ELF::SHF_ALLOC);
430   StaticDtorSection = getContext().getELFSection(
431       ".fini_array", ELF::SHT_FINI_ARRAY, ELF::SHF_WRITE | ELF::SHF_ALLOC);
432 }
433 
434 //===----------------------------------------------------------------------===//
435 //                                 MachO
436 //===----------------------------------------------------------------------===//
437 
438 TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
439   : TargetLoweringObjectFile() {
440   SupportIndirectSymViaGOTPCRel = true;
441 }
442 
443 /// emitModuleFlags - Perform code emission for module flags.
444 void TargetLoweringObjectFileMachO::
445 emitModuleFlags(MCStreamer &Streamer,
446                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
447                 Mangler &Mang, const TargetMachine &TM) const {
448   unsigned VersionVal = 0;
449   unsigned ImageInfoFlags = 0;
450   MDNode *LinkerOptions = nullptr;
451   StringRef SectionVal;
452 
453   for (ArrayRef<Module::ModuleFlagEntry>::iterator
454          i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
455     const Module::ModuleFlagEntry &MFE = *i;
456 
457     // Ignore flags with 'Require' behavior.
458     if (MFE.Behavior == Module::Require)
459       continue;
460 
461     StringRef Key = MFE.Key->getString();
462     Metadata *Val = MFE.Val;
463 
464     if (Key == "Objective-C Image Info Version") {
465       VersionVal = mdconst::extract<ConstantInt>(Val)->getZExtValue();
466     } else if (Key == "Objective-C Garbage Collection" ||
467                Key == "Objective-C GC Only" ||
468                Key == "Objective-C Is Simulated" ||
469                Key == "Objective-C Image Swift Version") {
470       ImageInfoFlags |= mdconst::extract<ConstantInt>(Val)->getZExtValue();
471     } else if (Key == "Objective-C Image Info Section") {
472       SectionVal = cast<MDString>(Val)->getString();
473     } else if (Key == "Linker Options") {
474       LinkerOptions = cast<MDNode>(Val);
475     }
476   }
477 
478   // Emit the linker options if present.
479   if (LinkerOptions) {
480     for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
481       MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
482       SmallVector<std::string, 4> StrOptions;
483 
484       // Convert to strings.
485       for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
486         MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
487         StrOptions.push_back(MDOption->getString());
488       }
489 
490       Streamer.EmitLinkerOptions(StrOptions);
491     }
492   }
493 
494   // The section is mandatory. If we don't have it, then we don't have GC info.
495   if (SectionVal.empty()) return;
496 
497   StringRef Segment, Section;
498   unsigned TAA = 0, StubSize = 0;
499   bool TAAParsed;
500   std::string ErrorCode =
501     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
502                                           TAA, TAAParsed, StubSize);
503   if (!ErrorCode.empty())
504     // If invalid, report the error with report_fatal_error.
505     report_fatal_error("Invalid section specifier '" + Section + "': " +
506                        ErrorCode + ".");
507 
508   // Get the section.
509   MCSectionMachO *S = getContext().getMachOSection(
510       Segment, Section, TAA, StubSize, SectionKind::getDataNoRel());
511   Streamer.SwitchSection(S);
512   Streamer.EmitLabel(getContext().
513                      getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
514   Streamer.EmitIntValue(VersionVal, 4);
515   Streamer.EmitIntValue(ImageInfoFlags, 4);
516   Streamer.AddBlankLine();
517 }
518 
519 static void checkMachOComdat(const GlobalValue *GV) {
520   const Comdat *C = GV->getComdat();
521   if (!C)
522     return;
523 
524   report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
525                      "' cannot be lowered.");
526 }
527 
528 MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
529     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
530     const TargetMachine &TM) const {
531   // Parse the section specifier and create it if valid.
532   StringRef Segment, Section;
533   unsigned TAA = 0, StubSize = 0;
534   bool TAAParsed;
535 
536   checkMachOComdat(GV);
537 
538   std::string ErrorCode =
539     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
540                                           TAA, TAAParsed, StubSize);
541   if (!ErrorCode.empty()) {
542     // If invalid, report the error with report_fatal_error.
543     report_fatal_error("Global variable '" + GV->getName() +
544                        "' has an invalid section specifier '" +
545                        GV->getSection() + "': " + ErrorCode + ".");
546   }
547 
548   // Get the section.
549   MCSectionMachO *S =
550       getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
551 
552   // If TAA wasn't set by ParseSectionSpecifier() above,
553   // use the value returned by getMachOSection() as a default.
554   if (!TAAParsed)
555     TAA = S->getTypeAndAttributes();
556 
557   // Okay, now that we got the section, verify that the TAA & StubSize agree.
558   // If the user declared multiple globals with different section flags, we need
559   // to reject it here.
560   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
561     // If invalid, report the error with report_fatal_error.
562     report_fatal_error("Global variable '" + GV->getName() +
563                        "' section type or attributes does not match previous"
564                        " section specifier");
565   }
566 
567   return S;
568 }
569 
570 MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
571     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
572     const TargetMachine &TM) const {
573   checkMachOComdat(GV);
574 
575   // Handle thread local data.
576   if (Kind.isThreadBSS()) return TLSBSSSection;
577   if (Kind.isThreadData()) return TLSDataSection;
578 
579   if (Kind.isText())
580     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
581 
582   // If this is weak/linkonce, put this in a coalescable section, either in text
583   // or data depending on if it is writable.
584   if (GV->isWeakForLinker()) {
585     if (Kind.isReadOnly())
586       return ConstTextCoalSection;
587     return DataCoalSection;
588   }
589 
590   // FIXME: Alignment check should be handled by section classifier.
591   if (Kind.isMergeable1ByteCString() &&
592       TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
593     return CStringSection;
594 
595   // Do not put 16-bit arrays in the UString section if they have an
596   // externally visible label, this runs into issues with certain linker
597   // versions.
598   if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
599       TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
600     return UStringSection;
601 
602   // With MachO only variables whose corresponding symbol starts with 'l' or
603   // 'L' can be merged, so we only try merging GVs with private linkage.
604   if (GV->hasPrivateLinkage() && Kind.isMergeableConst()) {
605     if (Kind.isMergeableConst4())
606       return FourByteConstantSection;
607     if (Kind.isMergeableConst8())
608       return EightByteConstantSection;
609     if (Kind.isMergeableConst16())
610       return SixteenByteConstantSection;
611   }
612 
613   // Otherwise, if it is readonly, but not something we can specially optimize,
614   // just drop it in .const.
615   if (Kind.isReadOnly())
616     return ReadOnlySection;
617 
618   // If this is marked const, put it into a const section.  But if the dynamic
619   // linker needs to write to it, put it in the data segment.
620   if (Kind.isReadOnlyWithRel())
621     return ConstDataSection;
622 
623   // Put zero initialized globals with strong external linkage in the
624   // DATA, __common section with the .zerofill directive.
625   if (Kind.isBSSExtern())
626     return DataCommonSection;
627 
628   // Put zero initialized globals with local linkage in __DATA,__bss directive
629   // with the .zerofill directive (aka .lcomm).
630   if (Kind.isBSSLocal())
631     return DataBSSSection;
632 
633   // Otherwise, just drop the variable in the normal data section.
634   return DataSection;
635 }
636 
637 MCSection *
638 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind,
639                                                      const Constant *C) const {
640   // If this constant requires a relocation, we have to put it in the data
641   // segment, not in the text segment.
642   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
643     return ConstDataSection;
644 
645   if (Kind.isMergeableConst4())
646     return FourByteConstantSection;
647   if (Kind.isMergeableConst8())
648     return EightByteConstantSection;
649   if (Kind.isMergeableConst16())
650     return SixteenByteConstantSection;
651   return ReadOnlySection;  // .const
652 }
653 
654 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
655     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
656     const TargetMachine &TM, MachineModuleInfo *MMI,
657     MCStreamer &Streamer) const {
658   // The mach-o version of this method defaults to returning a stub reference.
659 
660   if (Encoding & DW_EH_PE_indirect) {
661     MachineModuleInfoMachO &MachOMMI =
662       MMI->getObjFileInfo<MachineModuleInfoMachO>();
663 
664     MCSymbol *SSym =
665         getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
666 
667     // Add information about the stub reference to MachOMMI so that the stub
668     // gets emitted by the asmprinter.
669     MachineModuleInfoImpl::StubValueTy &StubSym =
670       GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
671                                   MachOMMI.getGVStubEntry(SSym);
672     if (!StubSym.getPointer()) {
673       MCSymbol *Sym = TM.getSymbol(GV, Mang);
674       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
675     }
676 
677     return TargetLoweringObjectFile::
678       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
679                         Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
680   }
681 
682   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
683                                                            TM, MMI, Streamer);
684 }
685 
686 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
687     const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
688     MachineModuleInfo *MMI) const {
689   // The mach-o version of this method defaults to returning a stub reference.
690   MachineModuleInfoMachO &MachOMMI =
691     MMI->getObjFileInfo<MachineModuleInfoMachO>();
692 
693   MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
694 
695   // Add information about the stub reference to MachOMMI so that the stub
696   // gets emitted by the asmprinter.
697   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
698   if (!StubSym.getPointer()) {
699     MCSymbol *Sym = TM.getSymbol(GV, Mang);
700     StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
701   }
702 
703   return SSym;
704 }
705 
706 const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
707     const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
708     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
709   // Although MachO 32-bit targets do not explictly have a GOTPCREL relocation
710   // as 64-bit do, we replace the GOT equivalent by accessing the final symbol
711   // through a non_lazy_ptr stub instead. One advantage is that it allows the
712   // computation of deltas to final external symbols. Example:
713   //
714   //    _extgotequiv:
715   //       .long   _extfoo
716   //
717   //    _delta:
718   //       .long   _extgotequiv-_delta
719   //
720   // is transformed to:
721   //
722   //    _delta:
723   //       .long   L_extfoo$non_lazy_ptr-(_delta+0)
724   //
725   //       .section        __IMPORT,__pointers,non_lazy_symbol_pointers
726   //    L_extfoo$non_lazy_ptr:
727   //       .indirect_symbol        _extfoo
728   //       .long   0
729   //
730   MachineModuleInfoMachO &MachOMMI =
731     MMI->getObjFileInfo<MachineModuleInfoMachO>();
732   MCContext &Ctx = getContext();
733 
734   // The offset must consider the original displacement from the base symbol
735   // since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
736   Offset = -MV.getConstant();
737   const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
738 
739   // Access the final symbol via sym$non_lazy_ptr and generate the appropriated
740   // non_lazy_ptr stubs.
741   SmallString<128> Name;
742   StringRef Suffix = "$non_lazy_ptr";
743   Name += DL->getPrivateGlobalPrefix();
744   Name += Sym->getName();
745   Name += Suffix;
746   MCSymbol *Stub = Ctx.getOrCreateSymbol(Name);
747 
748   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
749   if (!StubSym.getPointer())
750     StubSym = MachineModuleInfoImpl::
751       StubValueTy(const_cast<MCSymbol *>(Sym), true /* access indirectly */);
752 
753   const MCExpr *BSymExpr =
754     MCSymbolRefExpr::create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
755   const MCExpr *LHS =
756     MCSymbolRefExpr::create(Stub, MCSymbolRefExpr::VK_None, Ctx);
757 
758   if (!Offset)
759     return MCBinaryExpr::createSub(LHS, BSymExpr, Ctx);
760 
761   const MCExpr *RHS =
762     MCBinaryExpr::createAdd(BSymExpr, MCConstantExpr::create(Offset, Ctx), Ctx);
763   return MCBinaryExpr::createSub(LHS, RHS, Ctx);
764 }
765 
766 //===----------------------------------------------------------------------===//
767 //                                  COFF
768 //===----------------------------------------------------------------------===//
769 
770 static unsigned
771 getCOFFSectionFlags(SectionKind K) {
772   unsigned Flags = 0;
773 
774   if (K.isMetadata())
775     Flags |=
776       COFF::IMAGE_SCN_MEM_DISCARDABLE;
777   else if (K.isText())
778     Flags |=
779       COFF::IMAGE_SCN_MEM_EXECUTE |
780       COFF::IMAGE_SCN_MEM_READ |
781       COFF::IMAGE_SCN_CNT_CODE;
782   else if (K.isBSS())
783     Flags |=
784       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
785       COFF::IMAGE_SCN_MEM_READ |
786       COFF::IMAGE_SCN_MEM_WRITE;
787   else if (K.isThreadLocal())
788     Flags |=
789       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
790       COFF::IMAGE_SCN_MEM_READ |
791       COFF::IMAGE_SCN_MEM_WRITE;
792   else if (K.isReadOnly() || K.isReadOnlyWithRel())
793     Flags |=
794       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
795       COFF::IMAGE_SCN_MEM_READ;
796   else if (K.isWriteable())
797     Flags |=
798       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
799       COFF::IMAGE_SCN_MEM_READ |
800       COFF::IMAGE_SCN_MEM_WRITE;
801 
802   return Flags;
803 }
804 
805 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
806   const Comdat *C = GV->getComdat();
807   assert(C && "expected GV to have a Comdat!");
808 
809   StringRef ComdatGVName = C->getName();
810   const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
811   if (!ComdatGV)
812     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
813                        "' does not exist.");
814 
815   if (ComdatGV->getComdat() != C)
816     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
817                        "' is not a key for its COMDAT.");
818 
819   return ComdatGV;
820 }
821 
822 static int getSelectionForCOFF(const GlobalValue *GV) {
823   if (const Comdat *C = GV->getComdat()) {
824     const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
825     if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
826       ComdatKey = GA->getBaseObject();
827     if (ComdatKey == GV) {
828       switch (C->getSelectionKind()) {
829       case Comdat::Any:
830         return COFF::IMAGE_COMDAT_SELECT_ANY;
831       case Comdat::ExactMatch:
832         return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
833       case Comdat::Largest:
834         return COFF::IMAGE_COMDAT_SELECT_LARGEST;
835       case Comdat::NoDuplicates:
836         return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
837       case Comdat::SameSize:
838         return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
839       }
840     } else {
841       return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
842     }
843   } else if (GV->isWeakForLinker()) {
844     return COFF::IMAGE_COMDAT_SELECT_ANY;
845   }
846   return 0;
847 }
848 
849 MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
850     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
851     const TargetMachine &TM) const {
852   int Selection = 0;
853   unsigned Characteristics = getCOFFSectionFlags(Kind);
854   StringRef Name = GV->getSection();
855   StringRef COMDATSymName = "";
856   if (GV->hasComdat()) {
857     Selection = getSelectionForCOFF(GV);
858     const GlobalValue *ComdatGV;
859     if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
860       ComdatGV = getComdatGVForCOFF(GV);
861     else
862       ComdatGV = GV;
863 
864     if (!ComdatGV->hasPrivateLinkage()) {
865       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
866       COMDATSymName = Sym->getName();
867       Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
868     } else {
869       Selection = 0;
870     }
871   }
872   return getContext().getCOFFSection(Name,
873                                      Characteristics,
874                                      Kind,
875                                      COMDATSymName,
876                                      Selection);
877 }
878 
879 static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
880   if (Kind.isText())
881     return ".text";
882   if (Kind.isBSS())
883     return ".bss";
884   if (Kind.isThreadLocal())
885     return ".tls$";
886   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
887     return ".rdata";
888   return ".data";
889 }
890 
891 MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
892     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
893     const TargetMachine &TM) const {
894   // If we have -ffunction-sections then we should emit the global value to a
895   // uniqued section specifically for it.
896   bool EmitUniquedSection;
897   if (Kind.isText())
898     EmitUniquedSection = TM.getFunctionSections();
899   else
900     EmitUniquedSection = TM.getDataSections();
901 
902   if ((EmitUniquedSection && !Kind.isCommon()) || GV->hasComdat()) {
903     const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
904     unsigned Characteristics = getCOFFSectionFlags(Kind);
905 
906     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
907     int Selection = getSelectionForCOFF(GV);
908     if (!Selection)
909       Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
910     const GlobalValue *ComdatGV;
911     if (GV->hasComdat())
912       ComdatGV = getComdatGVForCOFF(GV);
913     else
914       ComdatGV = GV;
915 
916     if (!ComdatGV->hasPrivateLinkage()) {
917       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
918       StringRef COMDATSymName = Sym->getName();
919       return getContext().getCOFFSection(Name, Characteristics, Kind,
920                                          COMDATSymName, Selection);
921     } else {
922       SmallString<256> TmpData;
923       getNameWithPrefix(TmpData, GV, /*CannotUsePrivateLabel=*/true, Mang, TM);
924       return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
925                                          Selection);
926     }
927   }
928 
929   if (Kind.isText())
930     return TextSection;
931 
932   if (Kind.isThreadLocal())
933     return TLSDataSection;
934 
935   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
936     return ReadOnlySection;
937 
938   // Note: we claim that common symbols are put in BSSSection, but they are
939   // really emitted with the magic .comm directive, which creates a symbol table
940   // entry but not a section.
941   if (Kind.isBSS() || Kind.isCommon())
942     return BSSSection;
943 
944   return DataSection;
945 }
946 
947 void TargetLoweringObjectFileCOFF::getNameWithPrefix(
948     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
949     bool CannotUsePrivateLabel, Mangler &Mang, const TargetMachine &TM) const {
950   if (GV->hasPrivateLinkage() &&
951       ((isa<Function>(GV) && TM.getFunctionSections()) ||
952        (isa<GlobalVariable>(GV) && TM.getDataSections())))
953     CannotUsePrivateLabel = true;
954 
955   Mang.getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
956 }
957 
958 MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
959     const Function &F, Mangler &Mang, const TargetMachine &TM) const {
960   // If the function can be removed, produce a unique section so that
961   // the table doesn't prevent the removal.
962   const Comdat *C = F.getComdat();
963   bool EmitUniqueSection = TM.getFunctionSections() || C;
964   if (!EmitUniqueSection)
965     return ReadOnlySection;
966 
967   // FIXME: we should produce a symbol for F instead.
968   if (F.hasPrivateLinkage())
969     return ReadOnlySection;
970 
971   MCSymbol *Sym = TM.getSymbol(&F, Mang);
972   StringRef COMDATSymName = Sym->getName();
973 
974   SectionKind Kind = SectionKind::getReadOnly();
975   const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
976   unsigned Characteristics = getCOFFSectionFlags(Kind);
977   Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
978 
979   return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
980                                      COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
981 }
982 
983 void TargetLoweringObjectFileCOFF::
984 emitModuleFlags(MCStreamer &Streamer,
985                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
986                 Mangler &Mang, const TargetMachine &TM) const {
987   MDNode *LinkerOptions = nullptr;
988 
989   // Look for the "Linker Options" flag, since it's the only one we support.
990   for (ArrayRef<Module::ModuleFlagEntry>::iterator
991        i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
992     const Module::ModuleFlagEntry &MFE = *i;
993     StringRef Key = MFE.Key->getString();
994     Metadata *Val = MFE.Val;
995     if (Key == "Linker Options") {
996       LinkerOptions = cast<MDNode>(Val);
997       break;
998     }
999   }
1000   if (!LinkerOptions)
1001     return;
1002 
1003   // Emit the linker options to the linker .drectve section.  According to the
1004   // spec, this section is a space-separated string containing flags for linker.
1005   MCSection *Sec = getDrectveSection();
1006   Streamer.SwitchSection(Sec);
1007   for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
1008     MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
1009     for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
1010       MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
1011       // Lead with a space for consistency with our dllexport implementation.
1012       std::string Directive(" ");
1013       Directive.append(MDOption->getString());
1014       Streamer.EmitBytes(Directive);
1015     }
1016   }
1017 }
1018 
1019 MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
1020     unsigned Priority, const MCSymbol *KeySym) const {
1021   return getContext().getAssociativeCOFFSection(
1022       cast<MCSectionCOFF>(StaticCtorSection), KeySym);
1023 }
1024 
1025 MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
1026     unsigned Priority, const MCSymbol *KeySym) const {
1027   return getContext().getAssociativeCOFFSection(
1028       cast<MCSectionCOFF>(StaticDtorSection), KeySym);
1029 }
1030 
1031 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
1032     raw_ostream &OS, const GlobalValue *GV, const Mangler &Mang) const {
1033   if (!GV->hasDLLExportStorageClass() || GV->isDeclaration())
1034     return;
1035 
1036   const Triple &TT = getTargetTriple();
1037 
1038   if (TT.isKnownWindowsMSVCEnvironment())
1039     OS << " /EXPORT:";
1040   else
1041     OS << " -export:";
1042 
1043   if (TT.isWindowsGNUEnvironment() || TT.isWindowsCygwinEnvironment()) {
1044     std::string Flag;
1045     raw_string_ostream FlagOS(Flag);
1046     Mang.getNameWithPrefix(FlagOS, GV, false);
1047     FlagOS.flush();
1048     if (Flag[0] == DL->getGlobalPrefix())
1049       OS << Flag.substr(1);
1050     else
1051       OS << Flag;
1052   } else {
1053     Mang.getNameWithPrefix(OS, GV, false);
1054   }
1055 
1056   if (!GV->getValueType()->isFunctionTy()) {
1057     if (TT.isKnownWindowsMSVCEnvironment())
1058       OS << ",DATA";
1059     else
1060       OS << ",data";
1061   }
1062 }
1063