xref: /llvm-project/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (revision 8bce66b09392b03ef73e0db8419dfd42aaf73c82) 
1 //===-- llvm/CodeGen/TargetLoweringObjectFileImpl.cpp - Object File Info --===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements classes used to handle lowerings specific to common
11 // object file formats.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
16 #include "llvm/ADT/SmallString.h"
17 #include "llvm/ADT/StringExtras.h"
18 #include "llvm/ADT/Triple.h"
19 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
20 #include "llvm/IR/Constants.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/IR/DerivedTypes.h"
23 #include "llvm/IR/Function.h"
24 #include "llvm/IR/GlobalVariable.h"
25 #include "llvm/IR/Mangler.h"
26 #include "llvm/IR/Module.h"
27 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/MCExpr.h"
29 #include "llvm/MC/MCSectionCOFF.h"
30 #include "llvm/MC/MCSectionELF.h"
31 #include "llvm/MC/MCSectionMachO.h"
32 #include "llvm/MC/MCStreamer.h"
33 #include "llvm/MC/MCSymbol.h"
34 #include "llvm/Support/Dwarf.h"
35 #include "llvm/Support/ELF.h"
36 #include "llvm/Support/ErrorHandling.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include "llvm/Target/TargetLowering.h"
39 #include "llvm/Target/TargetMachine.h"
40 using namespace llvm;
41 using namespace dwarf;
42 
43 //===----------------------------------------------------------------------===//
44 //                                  ELF
45 //===----------------------------------------------------------------------===//
46 
47 MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
48     const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
49     MachineModuleInfo *MMI) const {
50   unsigned Encoding = getPersonalityEncoding();
51   if ((Encoding & 0x80) == dwarf::DW_EH_PE_indirect)
52     return getContext().GetOrCreateSymbol(StringRef("DW.ref.") +
53                                           TM.getSymbol(GV, Mang)->getName());
54   if ((Encoding & 0x70) == dwarf::DW_EH_PE_absptr)
55     return TM.getSymbol(GV, Mang);
56   report_fatal_error("We do not support this DWARF encoding yet!");
57 }
58 
59 void TargetLoweringObjectFileELF::emitPersonalityValue(MCStreamer &Streamer,
60                                                        const TargetMachine &TM,
61                                                        const MCSymbol *Sym) const {
62   SmallString<64> NameData("DW.ref.");
63   NameData += Sym->getName();
64   MCSymbol *Label = getContext().GetOrCreateSymbol(NameData);
65   Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
66   Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
67   StringRef Prefix = ".data.";
68   NameData.insert(NameData.begin(), Prefix.begin(), Prefix.end());
69   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
70   const MCSection *Sec = getContext().getELFSection(NameData,
71                                                     ELF::SHT_PROGBITS,
72                                                     Flags,
73                                                     SectionKind::getDataRel(),
74                                                     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 
168 static unsigned
169 getELFSectionFlags(SectionKind K) {
170   unsigned Flags = 0;
171 
172   if (!K.isMetadata())
173     Flags |= ELF::SHF_ALLOC;
174 
175   if (K.isText())
176     Flags |= ELF::SHF_EXECINSTR;
177 
178   if (K.isWriteable())
179     Flags |= ELF::SHF_WRITE;
180 
181   if (K.isThreadLocal())
182     Flags |= ELF::SHF_TLS;
183 
184   // K.isMergeableConst() is left out to honour PR4650
185   if (K.isMergeableCString() || K.isMergeableConst4() ||
186       K.isMergeableConst8() || K.isMergeableConst16())
187     Flags |= ELF::SHF_MERGE;
188 
189   if (K.isMergeableCString())
190     Flags |= ELF::SHF_STRINGS;
191 
192   return Flags;
193 }
194 
195 static const Comdat *getELFComdat(const GlobalValue *GV) {
196   const Comdat *C = GV->getComdat();
197   if (!C)
198     return nullptr;
199 
200   if (C->getSelectionKind() != Comdat::Any)
201     report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
202                        C->getName() + "' cannot be lowered.");
203 
204   return C;
205 }
206 
207 const MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
208     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
209     const TargetMachine &TM) const {
210   StringRef SectionName = GV->getSection();
211 
212   // Infer section flags from the section name if we can.
213   Kind = getELFKindForNamedSection(SectionName, Kind);
214 
215   StringRef Group = "";
216   unsigned Flags = getELFSectionFlags(Kind);
217   if (const Comdat *C = getELFComdat(GV)) {
218     Group = C->getName();
219     Flags |= ELF::SHF_GROUP;
220   }
221   return getContext().getELFSection(SectionName,
222                                     getELFSectionType(SectionName, Kind), Flags,
223                                     Kind, /*EntrySize=*/0, Group);
224 }
225 
226 /// getSectionPrefixForGlobal - Return the section prefix name used by options
227 /// FunctionsSections and DataSections.
228 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
229   if (Kind.isText())                 return ".text.";
230   if (Kind.isReadOnly())             return ".rodata.";
231   if (Kind.isBSS())                  return ".bss.";
232 
233   if (Kind.isThreadData())           return ".tdata.";
234   if (Kind.isThreadBSS())            return ".tbss.";
235 
236   if (Kind.isDataNoRel())            return ".data.";
237   if (Kind.isDataRelLocal())         return ".data.rel.local.";
238   if (Kind.isDataRel())              return ".data.rel.";
239   if (Kind.isReadOnlyWithRelLocal()) return ".data.rel.ro.local.";
240 
241   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
242   return ".data.rel.ro.";
243 }
244 
245 const MCSection *TargetLoweringObjectFileELF::
246 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
247                        Mangler &Mang, const TargetMachine &TM) const {
248   // If we have -ffunction-section or -fdata-section then we should emit the
249   // global value to a uniqued section specifically for it.
250   bool EmitUniquedSection;
251   if (Kind.isText())
252     EmitUniquedSection = TM.getFunctionSections();
253   else
254     EmitUniquedSection = TM.getDataSections();
255 
256   // If this global is linkonce/weak and the target handles this by emitting it
257   // into a 'uniqued' section name, create and return the section now.
258   if ((GV->isWeakForLinker() || EmitUniquedSection || GV->hasComdat()) &&
259       !Kind.isCommon()) {
260     StringRef Prefix = getSectionPrefixForGlobal(Kind);
261 
262     SmallString<128> Name(Prefix);
263     TM.getNameWithPrefix(Name, GV, Mang, true);
264 
265     StringRef Group = "";
266     unsigned Flags = getELFSectionFlags(Kind);
267     if (GV->isWeakForLinker() || GV->hasComdat()) {
268       if (const Comdat *C = getELFComdat(GV))
269         Group = C->getName();
270       else
271         Group = Name.substr(Prefix.size());
272       Flags |= ELF::SHF_GROUP;
273     }
274 
275     return getContext().getELFSection(Name.str(),
276                                       getELFSectionType(Name.str(), Kind),
277                                       Flags, Kind, 0, Group);
278   }
279 
280   if (Kind.isText()) return TextSection;
281 
282   if (Kind.isMergeable1ByteCString() ||
283       Kind.isMergeable2ByteCString() ||
284       Kind.isMergeable4ByteCString()) {
285 
286     // We also need alignment here.
287     // FIXME: this is getting the alignment of the character, not the
288     // alignment of the global!
289     unsigned Align =
290       TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV));
291 
292     const char *SizeSpec = ".rodata.str1.";
293     if (Kind.isMergeable2ByteCString())
294       SizeSpec = ".rodata.str2.";
295     else if (Kind.isMergeable4ByteCString())
296       SizeSpec = ".rodata.str4.";
297     else
298       assert(Kind.isMergeable1ByteCString() && "unknown string width");
299 
300 
301     std::string Name = SizeSpec + utostr(Align);
302     return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
303                                       ELF::SHF_ALLOC |
304                                       ELF::SHF_MERGE |
305                                       ELF::SHF_STRINGS,
306                                       Kind);
307   }
308 
309   if (Kind.isMergeableConst()) {
310     if (Kind.isMergeableConst4() && MergeableConst4Section)
311       return MergeableConst4Section;
312     if (Kind.isMergeableConst8() && MergeableConst8Section)
313       return MergeableConst8Section;
314     if (Kind.isMergeableConst16() && MergeableConst16Section)
315       return MergeableConst16Section;
316     return ReadOnlySection;  // .const
317   }
318 
319   if (Kind.isReadOnly())             return ReadOnlySection;
320 
321   if (Kind.isThreadData())           return TLSDataSection;
322   if (Kind.isThreadBSS())            return TLSBSSSection;
323 
324   // Note: we claim that common symbols are put in BSSSection, but they are
325   // really emitted with the magic .comm directive, which creates a symbol table
326   // entry but not a section.
327   if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
328 
329   if (Kind.isDataNoRel())            return DataSection;
330   if (Kind.isDataRelLocal())         return DataRelLocalSection;
331   if (Kind.isDataRel())              return DataRelSection;
332   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
333 
334   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
335   return DataRelROSection;
336 }
337 
338 /// getSectionForConstant - Given a mergeable constant with the
339 /// specified size and relocation information, return a section that it
340 /// should be placed in.
341 const MCSection *
342 TargetLoweringObjectFileELF::getSectionForConstant(SectionKind Kind,
343                                                    const Constant *C) const {
344   if (Kind.isMergeableConst4() && MergeableConst4Section)
345     return MergeableConst4Section;
346   if (Kind.isMergeableConst8() && MergeableConst8Section)
347     return MergeableConst8Section;
348   if (Kind.isMergeableConst16() && MergeableConst16Section)
349     return MergeableConst16Section;
350   if (Kind.isReadOnly())
351     return ReadOnlySection;
352 
353   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
354   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
355   return DataRelROSection;
356 }
357 
358 const MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
359     unsigned Priority, const MCSymbol *KeySym) const {
360   // The default scheme is .ctor / .dtor, so we have to invert the priority
361   // numbering.
362   if (Priority == 65535)
363     return StaticCtorSection;
364 
365   if (UseInitArray) {
366     std::string Name = std::string(".init_array.") + utostr(Priority);
367     return getContext().getELFSection(Name, ELF::SHT_INIT_ARRAY,
368                                       ELF::SHF_ALLOC | ELF::SHF_WRITE,
369                                       SectionKind::getDataRel());
370   } else {
371     std::string Name = std::string(".ctors.") + utostr(65535 - Priority);
372     return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
373                                       ELF::SHF_ALLOC |ELF::SHF_WRITE,
374                                       SectionKind::getDataRel());
375   }
376 }
377 
378 const MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
379     unsigned Priority, const MCSymbol *KeySym) const {
380   // The default scheme is .ctor / .dtor, so we have to invert the priority
381   // numbering.
382   if (Priority == 65535)
383     return StaticDtorSection;
384 
385   if (UseInitArray) {
386     std::string Name = std::string(".fini_array.") + utostr(Priority);
387     return getContext().getELFSection(Name, ELF::SHT_FINI_ARRAY,
388                                       ELF::SHF_ALLOC | ELF::SHF_WRITE,
389                                       SectionKind::getDataRel());
390   } else {
391     std::string Name = std::string(".dtors.") + utostr(65535 - Priority);
392     return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
393                                       ELF::SHF_ALLOC |ELF::SHF_WRITE,
394                                       SectionKind::getDataRel());
395   }
396 }
397 
398 void
399 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
400   UseInitArray = UseInitArray_;
401   if (!UseInitArray)
402     return;
403 
404   StaticCtorSection =
405     getContext().getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
406                                ELF::SHF_WRITE |
407                                ELF::SHF_ALLOC,
408                                SectionKind::getDataRel());
409   StaticDtorSection =
410     getContext().getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
411                                ELF::SHF_WRITE |
412                                ELF::SHF_ALLOC,
413                                SectionKind::getDataRel());
414 }
415 
416 //===----------------------------------------------------------------------===//
417 //                                 MachO
418 //===----------------------------------------------------------------------===//
419 
420 /// getDepLibFromLinkerOpt - Extract the dependent library name from a linker
421 /// option string. Returns StringRef() if the option does not specify a library.
422 StringRef TargetLoweringObjectFileMachO::
423 getDepLibFromLinkerOpt(StringRef LinkerOption) const {
424   const char *LibCmd = "-l";
425   if (LinkerOption.startswith(LibCmd))
426     return LinkerOption.substr(strlen(LibCmd));
427   return StringRef();
428 }
429 
430 /// emitModuleFlags - Perform code emission for module flags.
431 void TargetLoweringObjectFileMachO::
432 emitModuleFlags(MCStreamer &Streamer,
433                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
434                 Mangler &Mang, const TargetMachine &TM) const {
435   unsigned VersionVal = 0;
436   unsigned ImageInfoFlags = 0;
437   MDNode *LinkerOptions = nullptr;
438   StringRef SectionVal;
439 
440   for (ArrayRef<Module::ModuleFlagEntry>::iterator
441          i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
442     const Module::ModuleFlagEntry &MFE = *i;
443 
444     // Ignore flags with 'Require' behavior.
445     if (MFE.Behavior == Module::Require)
446       continue;
447 
448     StringRef Key = MFE.Key->getString();
449     Value *Val = MFE.Val;
450 
451     if (Key == "Objective-C Image Info Version") {
452       VersionVal = cast<ConstantInt>(Val)->getZExtValue();
453     } else if (Key == "Objective-C Garbage Collection" ||
454                Key == "Objective-C GC Only" ||
455                Key == "Objective-C Is Simulated") {
456       ImageInfoFlags |= cast<ConstantInt>(Val)->getZExtValue();
457     } else if (Key == "Objective-C Image Info Section") {
458       SectionVal = cast<MDString>(Val)->getString();
459     } else if (Key == "Linker Options") {
460       LinkerOptions = cast<MDNode>(Val);
461     }
462   }
463 
464   // Emit the linker options if present.
465   if (LinkerOptions) {
466     for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
467       MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
468       SmallVector<std::string, 4> StrOptions;
469 
470       // Convert to strings.
471       for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
472         MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
473         StrOptions.push_back(MDOption->getString());
474       }
475 
476       Streamer.EmitLinkerOptions(StrOptions);
477     }
478   }
479 
480   // The section is mandatory. If we don't have it, then we don't have GC info.
481   if (SectionVal.empty()) return;
482 
483   StringRef Segment, Section;
484   unsigned TAA = 0, StubSize = 0;
485   bool TAAParsed;
486   std::string ErrorCode =
487     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
488                                           TAA, TAAParsed, StubSize);
489   if (!ErrorCode.empty())
490     // If invalid, report the error with report_fatal_error.
491     report_fatal_error("Invalid section specifier '" + Section + "': " +
492                        ErrorCode + ".");
493 
494   // Get the section.
495   const MCSectionMachO *S =
496     getContext().getMachOSection(Segment, Section, TAA, StubSize,
497                                  SectionKind::getDataNoRel());
498   Streamer.SwitchSection(S);
499   Streamer.EmitLabel(getContext().
500                      GetOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
501   Streamer.EmitIntValue(VersionVal, 4);
502   Streamer.EmitIntValue(ImageInfoFlags, 4);
503   Streamer.AddBlankLine();
504 }
505 
506 static void checkMachOComdat(const GlobalValue *GV) {
507   const Comdat *C = GV->getComdat();
508   if (!C)
509     return;
510 
511   report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
512                      "' cannot be lowered.");
513 }
514 
515 const MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
516     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
517     const TargetMachine &TM) const {
518   // Parse the section specifier and create it if valid.
519   StringRef Segment, Section;
520   unsigned TAA = 0, StubSize = 0;
521   bool TAAParsed;
522 
523   checkMachOComdat(GV);
524 
525   std::string ErrorCode =
526     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
527                                           TAA, TAAParsed, StubSize);
528   if (!ErrorCode.empty()) {
529     // If invalid, report the error with report_fatal_error.
530     report_fatal_error("Global variable '" + GV->getName() +
531                        "' has an invalid section specifier '" +
532                        GV->getSection() + "': " + ErrorCode + ".");
533   }
534 
535   // Get the section.
536   const MCSectionMachO *S =
537     getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
538 
539   // If TAA wasn't set by ParseSectionSpecifier() above,
540   // use the value returned by getMachOSection() as a default.
541   if (!TAAParsed)
542     TAA = S->getTypeAndAttributes();
543 
544   // Okay, now that we got the section, verify that the TAA & StubSize agree.
545   // If the user declared multiple globals with different section flags, we need
546   // to reject it here.
547   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
548     // If invalid, report the error with report_fatal_error.
549     report_fatal_error("Global variable '" + GV->getName() +
550                        "' section type or attributes does not match previous"
551                        " section specifier");
552   }
553 
554   return S;
555 }
556 
557 bool TargetLoweringObjectFileMachO::isSectionAtomizableBySymbols(
558     const MCSection &Section) const {
559     const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
560 
561     // Sections holding 1 byte strings are atomized based on the data
562     // they contain.
563     // Sections holding 2 byte strings require symbols in order to be
564     // atomized.
565     // There is no dedicated section for 4 byte strings.
566     if (SMO.getKind().isMergeable1ByteCString())
567       return false;
568 
569     if (SMO.getSegmentName() == "__DATA" &&
570         SMO.getSectionName() == "__cfstring")
571       return false;
572 
573     switch (SMO.getType()) {
574     default:
575       return true;
576 
577       // These sections are atomized at the element boundaries without using
578       // symbols.
579     case MachO::S_4BYTE_LITERALS:
580     case MachO::S_8BYTE_LITERALS:
581     case MachO::S_16BYTE_LITERALS:
582     case MachO::S_LITERAL_POINTERS:
583     case MachO::S_NON_LAZY_SYMBOL_POINTERS:
584     case MachO::S_LAZY_SYMBOL_POINTERS:
585     case MachO::S_MOD_INIT_FUNC_POINTERS:
586     case MachO::S_MOD_TERM_FUNC_POINTERS:
587     case MachO::S_INTERPOSING:
588       return false;
589     }
590 }
591 
592 const MCSection *TargetLoweringObjectFileMachO::
593 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
594                        Mangler &Mang, const TargetMachine &TM) const {
595   checkMachOComdat(GV);
596 
597   // Handle thread local data.
598   if (Kind.isThreadBSS()) return TLSBSSSection;
599   if (Kind.isThreadData()) return TLSDataSection;
600 
601   if (Kind.isText())
602     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
603 
604   // If this is weak/linkonce, put this in a coalescable section, either in text
605   // or data depending on if it is writable.
606   if (GV->isWeakForLinker()) {
607     if (Kind.isReadOnly())
608       return ConstTextCoalSection;
609     return DataCoalSection;
610   }
611 
612   // FIXME: Alignment check should be handled by section classifier.
613   if (Kind.isMergeable1ByteCString() &&
614       TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
615     return CStringSection;
616 
617   // Do not put 16-bit arrays in the UString section if they have an
618   // externally visible label, this runs into issues with certain linker
619   // versions.
620   if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
621       TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
622     return UStringSection;
623 
624   if (Kind.isMergeableConst()) {
625     if (Kind.isMergeableConst4())
626       return FourByteConstantSection;
627     if (Kind.isMergeableConst8())
628       return EightByteConstantSection;
629     if (Kind.isMergeableConst16())
630       return SixteenByteConstantSection;
631   }
632 
633   // Otherwise, if it is readonly, but not something we can specially optimize,
634   // just drop it in .const.
635   if (Kind.isReadOnly())
636     return ReadOnlySection;
637 
638   // If this is marked const, put it into a const section.  But if the dynamic
639   // linker needs to write to it, put it in the data segment.
640   if (Kind.isReadOnlyWithRel())
641     return ConstDataSection;
642 
643   // Put zero initialized globals with strong external linkage in the
644   // DATA, __common section with the .zerofill directive.
645   if (Kind.isBSSExtern())
646     return DataCommonSection;
647 
648   // Put zero initialized globals with local linkage in __DATA,__bss directive
649   // with the .zerofill directive (aka .lcomm).
650   if (Kind.isBSSLocal())
651     return DataBSSSection;
652 
653   // Otherwise, just drop the variable in the normal data section.
654   return DataSection;
655 }
656 
657 const MCSection *
658 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind,
659                                                      const Constant *C) const {
660   // If this constant requires a relocation, we have to put it in the data
661   // segment, not in the text segment.
662   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
663     return ConstDataSection;
664 
665   if (Kind.isMergeableConst4())
666     return FourByteConstantSection;
667   if (Kind.isMergeableConst8())
668     return EightByteConstantSection;
669   if (Kind.isMergeableConst16())
670     return SixteenByteConstantSection;
671   return ReadOnlySection;  // .const
672 }
673 
674 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
675     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
676     const TargetMachine &TM, MachineModuleInfo *MMI,
677     MCStreamer &Streamer) const {
678   // The mach-o version of this method defaults to returning a stub reference.
679 
680   if (Encoding & DW_EH_PE_indirect) {
681     MachineModuleInfoMachO &MachOMMI =
682       MMI->getObjFileInfo<MachineModuleInfoMachO>();
683 
684     MCSymbol *SSym =
685         getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
686 
687     // Add information about the stub reference to MachOMMI so that the stub
688     // gets emitted by the asmprinter.
689     MachineModuleInfoImpl::StubValueTy &StubSym =
690       GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
691                                   MachOMMI.getGVStubEntry(SSym);
692     if (!StubSym.getPointer()) {
693       MCSymbol *Sym = TM.getSymbol(GV, Mang);
694       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
695     }
696 
697     return TargetLoweringObjectFile::
698       getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
699                         Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
700   }
701 
702   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
703                                                            TM, MMI, Streamer);
704 }
705 
706 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
707     const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
708     MachineModuleInfo *MMI) const {
709   // The mach-o version of this method defaults to returning a stub reference.
710   MachineModuleInfoMachO &MachOMMI =
711     MMI->getObjFileInfo<MachineModuleInfoMachO>();
712 
713   MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
714 
715   // Add information about the stub reference to MachOMMI so that the stub
716   // gets emitted by the asmprinter.
717   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
718   if (!StubSym.getPointer()) {
719     MCSymbol *Sym = TM.getSymbol(GV, Mang);
720     StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
721   }
722 
723   return SSym;
724 }
725 
726 //===----------------------------------------------------------------------===//
727 //                                  COFF
728 //===----------------------------------------------------------------------===//
729 
730 static unsigned
731 getCOFFSectionFlags(SectionKind K) {
732   unsigned Flags = 0;
733 
734   if (K.isMetadata())
735     Flags |=
736       COFF::IMAGE_SCN_MEM_DISCARDABLE;
737   else if (K.isText())
738     Flags |=
739       COFF::IMAGE_SCN_MEM_EXECUTE |
740       COFF::IMAGE_SCN_MEM_READ |
741       COFF::IMAGE_SCN_CNT_CODE;
742   else if (K.isBSS ())
743     Flags |=
744       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
745       COFF::IMAGE_SCN_MEM_READ |
746       COFF::IMAGE_SCN_MEM_WRITE;
747   else if (K.isThreadLocal())
748     Flags |=
749       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
750       COFF::IMAGE_SCN_MEM_READ |
751       COFF::IMAGE_SCN_MEM_WRITE;
752   else if (K.isReadOnly())
753     Flags |=
754       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
755       COFF::IMAGE_SCN_MEM_READ;
756   else if (K.isWriteable())
757     Flags |=
758       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
759       COFF::IMAGE_SCN_MEM_READ |
760       COFF::IMAGE_SCN_MEM_WRITE;
761 
762   return Flags;
763 }
764 
765 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
766   const Comdat *C = GV->getComdat();
767   assert(C && "expected GV to have a Comdat!");
768 
769   StringRef ComdatGVName = C->getName();
770   const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
771   if (!ComdatGV)
772     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
773                        "' does not exist.");
774 
775   if (ComdatGV->getComdat() != C)
776     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
777                        "' is not a key for it's COMDAT.");
778 
779   return ComdatGV;
780 }
781 
782 static int getSelectionForCOFF(const GlobalValue *GV) {
783   if (const Comdat *C = GV->getComdat()) {
784     const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
785     if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
786       ComdatKey = GA->getBaseObject();
787     if (ComdatKey == GV) {
788       switch (C->getSelectionKind()) {
789       case Comdat::Any:
790         return COFF::IMAGE_COMDAT_SELECT_ANY;
791       case Comdat::ExactMatch:
792         return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
793       case Comdat::Largest:
794         return COFF::IMAGE_COMDAT_SELECT_LARGEST;
795       case Comdat::NoDuplicates:
796         return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
797       case Comdat::SameSize:
798         return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
799       }
800     } else {
801       return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
802     }
803   } else if (GV->isWeakForLinker()) {
804     return COFF::IMAGE_COMDAT_SELECT_ANY;
805   }
806   return 0;
807 }
808 
809 const MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
810     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
811     const TargetMachine &TM) const {
812   int Selection = 0;
813   unsigned Characteristics = getCOFFSectionFlags(Kind);
814   StringRef Name = GV->getSection();
815   StringRef COMDATSymName = "";
816   if ((GV->isWeakForLinker() || GV->hasComdat()) && !Kind.isCommon()) {
817     Selection = getSelectionForCOFF(GV);
818     const GlobalValue *ComdatGV;
819     if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
820       ComdatGV = getComdatGVForCOFF(GV);
821     else
822       ComdatGV = GV;
823 
824     if (!ComdatGV->hasPrivateLinkage()) {
825       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
826       COMDATSymName = Sym->getName();
827       Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
828     } else {
829       Selection = 0;
830     }
831   }
832   return getContext().getCOFFSection(Name,
833                                      Characteristics,
834                                      Kind,
835                                      COMDATSymName,
836                                      Selection);
837 }
838 
839 static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
840   if (Kind.isText())
841     return ".text";
842   if (Kind.isBSS())
843     return ".bss";
844   if (Kind.isThreadLocal())
845     return ".tls$";
846   if (Kind.isWriteable())
847     return ".data";
848   return ".rdata";
849 }
850 
851 
852 const MCSection *TargetLoweringObjectFileCOFF::
853 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
854                        Mangler &Mang, const TargetMachine &TM) const {
855   // If we have -ffunction-sections then we should emit the global value to a
856   // uniqued section specifically for it.
857   bool EmitUniquedSection;
858   if (Kind.isText())
859     EmitUniquedSection = TM.getFunctionSections();
860   else
861     EmitUniquedSection = TM.getDataSections();
862 
863   // If this global is linkonce/weak and the target handles this by emitting it
864   // into a 'uniqued' section name, create and return the section now.
865   // Section names depend on the name of the symbol which is not feasible if the
866   // symbol has private linkage.
867   if ((GV->isWeakForLinker() || EmitUniquedSection || GV->hasComdat()) &&
868       !Kind.isCommon()) {
869     const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
870     unsigned Characteristics = getCOFFSectionFlags(Kind);
871 
872     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
873     int Selection = getSelectionForCOFF(GV);
874     if (!Selection)
875       Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
876     const GlobalValue *ComdatGV;
877     if (GV->hasComdat())
878       ComdatGV = getComdatGVForCOFF(GV);
879     else
880       ComdatGV = GV;
881 
882     if (!ComdatGV->hasPrivateLinkage()) {
883       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
884       StringRef COMDATSymName = Sym->getName();
885       return getContext().getCOFFSection(Name, Characteristics, Kind,
886                                          COMDATSymName, Selection);
887     }
888   }
889 
890   if (Kind.isText())
891     return TextSection;
892 
893   if (Kind.isThreadLocal())
894     return TLSDataSection;
895 
896   if (Kind.isReadOnly())
897     return ReadOnlySection;
898 
899   // Note: we claim that common symbols are put in BSSSection, but they are
900   // really emitted with the magic .comm directive, which creates a symbol table
901   // entry but not a section.
902   if (Kind.isBSS() || Kind.isCommon())
903     return BSSSection;
904 
905   return DataSection;
906 }
907 
908 StringRef TargetLoweringObjectFileCOFF::
909 getDepLibFromLinkerOpt(StringRef LinkerOption) const {
910   const char *LibCmd = "/DEFAULTLIB:";
911   if (LinkerOption.startswith(LibCmd))
912     return LinkerOption.substr(strlen(LibCmd));
913   return StringRef();
914 }
915 
916 void TargetLoweringObjectFileCOFF::
917 emitModuleFlags(MCStreamer &Streamer,
918                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
919                 Mangler &Mang, const TargetMachine &TM) const {
920   MDNode *LinkerOptions = nullptr;
921 
922   // Look for the "Linker Options" flag, since it's the only one we support.
923   for (ArrayRef<Module::ModuleFlagEntry>::iterator
924        i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
925     const Module::ModuleFlagEntry &MFE = *i;
926     StringRef Key = MFE.Key->getString();
927     Value *Val = MFE.Val;
928     if (Key == "Linker Options") {
929       LinkerOptions = cast<MDNode>(Val);
930       break;
931     }
932   }
933   if (!LinkerOptions)
934     return;
935 
936   // Emit the linker options to the linker .drectve section.  According to the
937   // spec, this section is a space-separated string containing flags for linker.
938   const MCSection *Sec = getDrectveSection();
939   Streamer.SwitchSection(Sec);
940   for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
941     MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
942     for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
943       MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
944       StringRef Op = MDOption->getString();
945       // Lead with a space for consistency with our dllexport implementation.
946       std::string Escaped(" ");
947       if (Op.find(" ") != StringRef::npos) {
948         // The PE-COFF spec says args with spaces must be quoted.  It doesn't say
949         // how to escape quotes, but it probably uses this algorithm:
950         // http://msdn.microsoft.com/en-us/library/17w5ykft(v=vs.85).aspx
951         // FIXME: Reuse escaping code from Support/Windows/Program.inc
952         Escaped.push_back('\"');
953         Escaped.append(Op);
954         Escaped.push_back('\"');
955       } else {
956         Escaped.append(Op);
957       }
958       Streamer.EmitBytes(Escaped);
959     }
960   }
961 }
962 
963 static const MCSection *getAssociativeCOFFSection(MCContext &Ctx,
964                                                   const MCSection *Sec,
965                                                   const MCSymbol *KeySym) {
966   // Return the normal section if we don't have to be associative.
967   if (!KeySym)
968     return Sec;
969 
970   // Make an associative section with the same name and kind as the normal
971   // section.
972   const MCSectionCOFF *SecCOFF = cast<MCSectionCOFF>(Sec);
973   unsigned Characteristics =
974       SecCOFF->getCharacteristics() | COFF::IMAGE_SCN_LNK_COMDAT;
975   return Ctx.getCOFFSection(SecCOFF->getSectionName(), Characteristics,
976                             SecCOFF->getKind(), KeySym->getName(),
977                             COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
978 }
979 
980 const MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
981     unsigned Priority, const MCSymbol *KeySym) const {
982   return getAssociativeCOFFSection(getContext(), StaticCtorSection, KeySym);
983 }
984 
985 const MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
986     unsigned Priority, const MCSymbol *KeySym) const {
987   return getAssociativeCOFFSection(getContext(), StaticDtorSection, KeySym);
988 }
989