xref: /llvm-project/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp (revision 5c0fa58e91cffdc0b7a1024890533942876d5691) 
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(
62     MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
63   SmallString<64> NameData("DW.ref.");
64   NameData += Sym->getName();
65   MCSymbolELF *Label =
66       cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
67   Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
68   Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
69   StringRef Prefix = ".data.";
70   NameData.insert(NameData.begin(), Prefix.begin(), Prefix.end());
71   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
72   MCSection *Sec = getContext().getELFSection(NameData, ELF::SHT_PROGBITS,
73                                               Flags, 0, Label->getName());
74   unsigned Size = DL.getPointerSize();
75   Streamer.SwitchSection(Sec);
76   Streamer.EmitValueToAlignment(DL.getPointerABIAlignment());
77   Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
78   const MCExpr *E = MCConstantExpr::create(Size, getContext());
79   Streamer.emitELFSize(Label, E);
80   Streamer.EmitLabel(Label);
81 
82   Streamer.EmitSymbolValue(Sym, Size);
83 }
84 
85 const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
86     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
87     const TargetMachine &TM, MachineModuleInfo *MMI,
88     MCStreamer &Streamer) const {
89 
90   if (Encoding & dwarf::DW_EH_PE_indirect) {
91     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
92 
93     MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", Mang, TM);
94 
95     // Add information about the stub reference to ELFMMI so that the stub
96     // gets emitted by the asmprinter.
97     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
98     if (!StubSym.getPointer()) {
99       MCSymbol *Sym = TM.getSymbol(GV, Mang);
100       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
101     }
102 
103     return TargetLoweringObjectFile::
104       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
105                         Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
106   }
107 
108   return TargetLoweringObjectFile::
109     getTTypeGlobalReference(GV, Encoding, Mang, TM, MMI, Streamer);
110 }
111 
112 static SectionKind
113 getELFKindForNamedSection(StringRef Name, SectionKind K) {
114   // N.B.: The defaults used in here are no the same ones used in MC.
115   // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
116   // both gas and MC will produce a section with no flags. Given
117   // section(".eh_frame") gcc will produce:
118   //
119   //   .section   .eh_frame,"a",@progbits
120   if (Name.empty() || Name[0] != '.') return K;
121 
122   // Some lame default implementation based on some magic section names.
123   if (Name == ".bss" ||
124       Name.startswith(".bss.") ||
125       Name.startswith(".gnu.linkonce.b.") ||
126       Name.startswith(".llvm.linkonce.b.") ||
127       Name == ".sbss" ||
128       Name.startswith(".sbss.") ||
129       Name.startswith(".gnu.linkonce.sb.") ||
130       Name.startswith(".llvm.linkonce.sb."))
131     return SectionKind::getBSS();
132 
133   if (Name == ".tdata" ||
134       Name.startswith(".tdata.") ||
135       Name.startswith(".gnu.linkonce.td.") ||
136       Name.startswith(".llvm.linkonce.td."))
137     return SectionKind::getThreadData();
138 
139   if (Name == ".tbss" ||
140       Name.startswith(".tbss.") ||
141       Name.startswith(".gnu.linkonce.tb.") ||
142       Name.startswith(".llvm.linkonce.tb."))
143     return SectionKind::getThreadBSS();
144 
145   return K;
146 }
147 
148 
149 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
150 
151   if (Name == ".init_array")
152     return ELF::SHT_INIT_ARRAY;
153 
154   if (Name == ".fini_array")
155     return ELF::SHT_FINI_ARRAY;
156 
157   if (Name == ".preinit_array")
158     return ELF::SHT_PREINIT_ARRAY;
159 
160   if (K.isBSS() || K.isThreadBSS())
161     return ELF::SHT_NOBITS;
162 
163   return ELF::SHT_PROGBITS;
164 }
165 
166 static unsigned getELFSectionFlags(SectionKind K) {
167   unsigned Flags = 0;
168 
169   if (!K.isMetadata())
170     Flags |= ELF::SHF_ALLOC;
171 
172   if (K.isText())
173     Flags |= ELF::SHF_EXECINSTR;
174 
175   if (K.isWriteable())
176     Flags |= ELF::SHF_WRITE;
177 
178   if (K.isThreadLocal())
179     Flags |= ELF::SHF_TLS;
180 
181   if (K.isMergeableCString() || K.isMergeableConst())
182     Flags |= ELF::SHF_MERGE;
183 
184   if (K.isMergeableCString())
185     Flags |= ELF::SHF_STRINGS;
186 
187   return Flags;
188 }
189 
190 static const Comdat *getELFComdat(const GlobalValue *GV) {
191   const Comdat *C = GV->getComdat();
192   if (!C)
193     return nullptr;
194 
195   if (C->getSelectionKind() != Comdat::Any)
196     report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
197                        C->getName() + "' cannot be lowered.");
198 
199   return C;
200 }
201 
202 MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
203     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
204     const TargetMachine &TM) const {
205   StringRef SectionName = GV->getSection();
206 
207   // Infer section flags from the section name if we can.
208   Kind = getELFKindForNamedSection(SectionName, Kind);
209 
210   StringRef Group = "";
211   unsigned Flags = getELFSectionFlags(Kind);
212   if (const Comdat *C = getELFComdat(GV)) {
213     Group = C->getName();
214     Flags |= ELF::SHF_GROUP;
215   }
216   return getContext().getELFSection(SectionName,
217                                     getELFSectionType(SectionName, Kind), Flags,
218                                     /*EntrySize=*/0, Group);
219 }
220 
221 /// Return the section prefix name used by options FunctionsSections and
222 /// DataSections.
223 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
224   if (Kind.isText())
225     return ".text";
226   if (Kind.isReadOnly())
227     return ".rodata";
228   if (Kind.isBSS())
229     return ".bss";
230   if (Kind.isThreadData())
231     return ".tdata";
232   if (Kind.isThreadBSS())
233     return ".tbss";
234   if (Kind.isDataNoRel())
235     return ".data";
236   if (Kind.isDataRelLocal())
237     return ".data.rel.local";
238   if (Kind.isDataRel())
239     return ".data.rel";
240   if (Kind.isReadOnlyWithRelLocal())
241     return ".data.rel.ro.local";
242   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
243   return ".data.rel.ro";
244 }
245 
246 static MCSectionELF *
247 selectELFSectionForGlobal(MCContext &Ctx, const GlobalValue *GV,
248                           SectionKind Kind, Mangler &Mang,
249                           const TargetMachine &TM, bool EmitUniqueSection,
250                           unsigned Flags, unsigned *NextUniqueID) {
251   unsigned EntrySize = 0;
252   if (Kind.isMergeableCString()) {
253     if (Kind.isMergeable2ByteCString()) {
254       EntrySize = 2;
255     } else if (Kind.isMergeable4ByteCString()) {
256       EntrySize = 4;
257     } else {
258       EntrySize = 1;
259       assert(Kind.isMergeable1ByteCString() && "unknown string width");
260     }
261   } else if (Kind.isMergeableConst()) {
262     if (Kind.isMergeableConst4()) {
263       EntrySize = 4;
264     } else if (Kind.isMergeableConst8()) {
265       EntrySize = 8;
266     } else {
267       assert(Kind.isMergeableConst16() && "unknown data width");
268       EntrySize = 16;
269     }
270   }
271 
272   StringRef Group = "";
273   if (const Comdat *C = getELFComdat(GV)) {
274     Flags |= ELF::SHF_GROUP;
275     Group = C->getName();
276   }
277 
278   bool UniqueSectionNames = TM.getUniqueSectionNames();
279   SmallString<128> Name;
280   if (Kind.isMergeableCString()) {
281     // We also need alignment here.
282     // FIXME: this is getting the alignment of the character, not the
283     // alignment of the global!
284     unsigned Align = GV->getParent()->getDataLayout().getPreferredAlignment(
285         cast<GlobalVariable>(GV));
286 
287     std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
288     Name = SizeSpec + utostr(Align);
289   } else if (Kind.isMergeableConst()) {
290     Name = ".rodata.cst";
291     Name += utostr(EntrySize);
292   } else {
293     Name = getSectionPrefixForGlobal(Kind);
294   }
295 
296   if (EmitUniqueSection && UniqueSectionNames) {
297     Name.push_back('.');
298     TM.getNameWithPrefix(Name, GV, Mang, true);
299   }
300   unsigned UniqueID = ~0;
301   if (EmitUniqueSection && !UniqueSectionNames) {
302     UniqueID = *NextUniqueID;
303     (*NextUniqueID)++;
304   }
305   return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags,
306                            EntrySize, Group, UniqueID);
307 }
308 
309 MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
310     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
311     const TargetMachine &TM) const {
312   unsigned Flags = getELFSectionFlags(Kind);
313 
314   // If we have -ffunction-section or -fdata-section then we should emit the
315   // global value to a uniqued section specifically for it.
316   bool EmitUniqueSection = false;
317   if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
318     if (Kind.isText())
319       EmitUniqueSection = TM.getFunctionSections();
320     else
321       EmitUniqueSection = TM.getDataSections();
322   }
323   EmitUniqueSection |= GV->hasComdat();
324 
325   return selectELFSectionForGlobal(getContext(), GV, Kind, Mang, TM,
326                                    EmitUniqueSection, Flags, &NextUniqueID);
327 }
328 
329 MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
330     const Function &F, Mangler &Mang, const TargetMachine &TM) const {
331   // If the function can be removed, produce a unique section so that
332   // the table doesn't prevent the removal.
333   const Comdat *C = F.getComdat();
334   bool EmitUniqueSection = TM.getFunctionSections() || C;
335   if (!EmitUniqueSection)
336     return ReadOnlySection;
337 
338   return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
339                                    Mang, TM, EmitUniqueSection, ELF::SHF_ALLOC,
340                                    &NextUniqueID);
341 }
342 
343 bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
344     bool UsesLabelDifference, const Function &F) const {
345   // We can always create relative relocations, so use another section
346   // that can be marked non-executable.
347   return false;
348 }
349 
350 /// Given a mergeable constant with the specified size and relocation
351 /// information, return a section that it should be placed in.
352 MCSection *TargetLoweringObjectFileELF::getSectionForConstant(
353     const DataLayout &DL, SectionKind Kind, const Constant *C) const {
354   if (Kind.isMergeableConst4() && MergeableConst4Section)
355     return MergeableConst4Section;
356   if (Kind.isMergeableConst8() && MergeableConst8Section)
357     return MergeableConst8Section;
358   if (Kind.isMergeableConst16() && MergeableConst16Section)
359     return MergeableConst16Section;
360   if (Kind.isReadOnly())
361     return ReadOnlySection;
362 
363   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
364   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
365   return DataRelROSection;
366 }
367 
368 static MCSectionELF *getStaticStructorSection(MCContext &Ctx, bool UseInitArray,
369                                               bool IsCtor, unsigned Priority,
370                                               const MCSymbol *KeySym) {
371   std::string Name;
372   unsigned Type;
373   unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
374   StringRef COMDAT = KeySym ? KeySym->getName() : "";
375 
376   if (KeySym)
377     Flags |= ELF::SHF_GROUP;
378 
379   if (UseInitArray) {
380     if (IsCtor) {
381       Type = ELF::SHT_INIT_ARRAY;
382       Name = ".init_array";
383     } else {
384       Type = ELF::SHT_FINI_ARRAY;
385       Name = ".fini_array";
386     }
387     if (Priority != 65535) {
388       Name += '.';
389       Name += utostr(Priority);
390     }
391   } else {
392     // The default scheme is .ctor / .dtor, so we have to invert the priority
393     // numbering.
394     if (IsCtor)
395       Name = ".ctors";
396     else
397       Name = ".dtors";
398     if (Priority != 65535) {
399       Name += '.';
400       Name += utostr(65535 - Priority);
401     }
402     Type = ELF::SHT_PROGBITS;
403   }
404 
405   return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
406 }
407 
408 MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
409     unsigned Priority, const MCSymbol *KeySym) const {
410   return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
411                                   KeySym);
412 }
413 
414 MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
415     unsigned Priority, const MCSymbol *KeySym) const {
416   return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
417                                   KeySym);
418 }
419 
420 void
421 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
422   UseInitArray = UseInitArray_;
423   if (!UseInitArray)
424     return;
425 
426   StaticCtorSection = getContext().getELFSection(
427       ".init_array", ELF::SHT_INIT_ARRAY, ELF::SHF_WRITE | ELF::SHF_ALLOC);
428   StaticDtorSection = getContext().getELFSection(
429       ".fini_array", ELF::SHT_FINI_ARRAY, ELF::SHF_WRITE | ELF::SHF_ALLOC);
430 }
431 
432 //===----------------------------------------------------------------------===//
433 //                                 MachO
434 //===----------------------------------------------------------------------===//
435 
436 TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
437   : TargetLoweringObjectFile() {
438   SupportIndirectSymViaGOTPCRel = true;
439 }
440 
441 /// emitModuleFlags - Perform code emission for module flags.
442 void TargetLoweringObjectFileMachO::
443 emitModuleFlags(MCStreamer &Streamer,
444                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
445                 Mangler &Mang, const TargetMachine &TM) const {
446   unsigned VersionVal = 0;
447   unsigned ImageInfoFlags = 0;
448   MDNode *LinkerOptions = nullptr;
449   StringRef SectionVal;
450 
451   for (ArrayRef<Module::ModuleFlagEntry>::iterator
452          i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
453     const Module::ModuleFlagEntry &MFE = *i;
454 
455     // Ignore flags with 'Require' behavior.
456     if (MFE.Behavior == Module::Require)
457       continue;
458 
459     StringRef Key = MFE.Key->getString();
460     Metadata *Val = MFE.Val;
461 
462     if (Key == "Objective-C Image Info Version") {
463       VersionVal = mdconst::extract<ConstantInt>(Val)->getZExtValue();
464     } else if (Key == "Objective-C Garbage Collection" ||
465                Key == "Objective-C GC Only" ||
466                Key == "Objective-C Is Simulated" ||
467                Key == "Objective-C Image Swift Version") {
468       ImageInfoFlags |= mdconst::extract<ConstantInt>(Val)->getZExtValue();
469     } else if (Key == "Objective-C Image Info Section") {
470       SectionVal = cast<MDString>(Val)->getString();
471     } else if (Key == "Linker Options") {
472       LinkerOptions = cast<MDNode>(Val);
473     }
474   }
475 
476   // Emit the linker options if present.
477   if (LinkerOptions) {
478     for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
479       MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
480       SmallVector<std::string, 4> StrOptions;
481 
482       // Convert to strings.
483       for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
484         MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
485         StrOptions.push_back(MDOption->getString());
486       }
487 
488       Streamer.EmitLinkerOptions(StrOptions);
489     }
490   }
491 
492   // The section is mandatory. If we don't have it, then we don't have GC info.
493   if (SectionVal.empty()) return;
494 
495   StringRef Segment, Section;
496   unsigned TAA = 0, StubSize = 0;
497   bool TAAParsed;
498   std::string ErrorCode =
499     MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
500                                           TAA, TAAParsed, StubSize);
501   if (!ErrorCode.empty())
502     // If invalid, report the error with report_fatal_error.
503     report_fatal_error("Invalid section specifier '" + Section + "': " +
504                        ErrorCode + ".");
505 
506   // Get the section.
507   MCSectionMachO *S = getContext().getMachOSection(
508       Segment, Section, TAA, StubSize, SectionKind::getDataNoRel());
509   Streamer.SwitchSection(S);
510   Streamer.EmitLabel(getContext().
511                      getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
512   Streamer.EmitIntValue(VersionVal, 4);
513   Streamer.EmitIntValue(ImageInfoFlags, 4);
514   Streamer.AddBlankLine();
515 }
516 
517 static void checkMachOComdat(const GlobalValue *GV) {
518   const Comdat *C = GV->getComdat();
519   if (!C)
520     return;
521 
522   report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
523                      "' cannot be lowered.");
524 }
525 
526 MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
527     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
528     const TargetMachine &TM) const {
529   // Parse the section specifier and create it if valid.
530   StringRef Segment, Section;
531   unsigned TAA = 0, StubSize = 0;
532   bool TAAParsed;
533 
534   checkMachOComdat(GV);
535 
536   std::string ErrorCode =
537     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
538                                           TAA, TAAParsed, StubSize);
539   if (!ErrorCode.empty()) {
540     // If invalid, report the error with report_fatal_error.
541     report_fatal_error("Global variable '" + GV->getName() +
542                        "' has an invalid section specifier '" +
543                        GV->getSection() + "': " + ErrorCode + ".");
544   }
545 
546   // Get the section.
547   MCSectionMachO *S =
548       getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
549 
550   // If TAA wasn't set by ParseSectionSpecifier() above,
551   // use the value returned by getMachOSection() as a default.
552   if (!TAAParsed)
553     TAA = S->getTypeAndAttributes();
554 
555   // Okay, now that we got the section, verify that the TAA & StubSize agree.
556   // If the user declared multiple globals with different section flags, we need
557   // to reject it here.
558   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
559     // If invalid, report the error with report_fatal_error.
560     report_fatal_error("Global variable '" + GV->getName() +
561                        "' section type or attributes does not match previous"
562                        " section specifier");
563   }
564 
565   return S;
566 }
567 
568 MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
569     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
570     const TargetMachine &TM) const {
571   checkMachOComdat(GV);
572 
573   // Handle thread local data.
574   if (Kind.isThreadBSS()) return TLSBSSSection;
575   if (Kind.isThreadData()) return TLSDataSection;
576 
577   if (Kind.isText())
578     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
579 
580   // If this is weak/linkonce, put this in a coalescable section, either in text
581   // or data depending on if it is writable.
582   if (GV->isWeakForLinker()) {
583     if (Kind.isReadOnly())
584       return ConstTextCoalSection;
585     return DataCoalSection;
586   }
587 
588   // FIXME: Alignment check should be handled by section classifier.
589   if (Kind.isMergeable1ByteCString() &&
590       GV->getParent()->getDataLayout().getPreferredAlignment(
591           cast<GlobalVariable>(GV)) < 32)
592     return CStringSection;
593 
594   // Do not put 16-bit arrays in the UString section if they have an
595   // externally visible label, this runs into issues with certain linker
596   // versions.
597   if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
598       GV->getParent()->getDataLayout().getPreferredAlignment(
599           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 *TargetLoweringObjectFileMachO::getSectionForConstant(
638     const DataLayout &DL, SectionKind Kind, const Constant *C) const {
639   // If this constant requires a relocation, we have to put it in the data
640   // segment, not in the text segment.
641   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
642     return ConstDataSection;
643 
644   if (Kind.isMergeableConst4())
645     return FourByteConstantSection;
646   if (Kind.isMergeableConst8())
647     return EightByteConstantSection;
648   if (Kind.isMergeableConst16())
649     return SixteenByteConstantSection;
650   return ReadOnlySection;  // .const
651 }
652 
653 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
654     const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
655     const TargetMachine &TM, MachineModuleInfo *MMI,
656     MCStreamer &Streamer) const {
657   // The mach-o version of this method defaults to returning a stub reference.
658 
659   if (Encoding & DW_EH_PE_indirect) {
660     MachineModuleInfoMachO &MachOMMI =
661       MMI->getObjFileInfo<MachineModuleInfoMachO>();
662 
663     MCSymbol *SSym =
664         getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
665 
666     // Add information about the stub reference to MachOMMI so that the stub
667     // gets emitted by the asmprinter.
668     MachineModuleInfoImpl::StubValueTy &StubSym =
669       GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
670                                   MachOMMI.getGVStubEntry(SSym);
671     if (!StubSym.getPointer()) {
672       MCSymbol *Sym = TM.getSymbol(GV, Mang);
673       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
674     }
675 
676     return TargetLoweringObjectFile::
677       getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
678                         Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
679   }
680 
681   return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
682                                                            TM, MMI, Streamer);
683 }
684 
685 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
686     const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
687     MachineModuleInfo *MMI) const {
688   // The mach-o version of this method defaults to returning a stub reference.
689   MachineModuleInfoMachO &MachOMMI =
690     MMI->getObjFileInfo<MachineModuleInfoMachO>();
691 
692   MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
693 
694   // Add information about the stub reference to MachOMMI so that the stub
695   // gets emitted by the asmprinter.
696   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
697   if (!StubSym.getPointer()) {
698     MCSymbol *Sym = TM.getSymbol(GV, Mang);
699     StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
700   }
701 
702   return SSym;
703 }
704 
705 const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
706     const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
707     MachineModuleInfo *MMI, MCStreamer &Streamer) const {
708   // Although MachO 32-bit targets do not explictly have a GOTPCREL relocation
709   // as 64-bit do, we replace the GOT equivalent by accessing the final symbol
710   // through a non_lazy_ptr stub instead. One advantage is that it allows the
711   // computation of deltas to final external symbols. Example:
712   //
713   //    _extgotequiv:
714   //       .long   _extfoo
715   //
716   //    _delta:
717   //       .long   _extgotequiv-_delta
718   //
719   // is transformed to:
720   //
721   //    _delta:
722   //       .long   L_extfoo$non_lazy_ptr-(_delta+0)
723   //
724   //       .section        __IMPORT,__pointers,non_lazy_symbol_pointers
725   //    L_extfoo$non_lazy_ptr:
726   //       .indirect_symbol        _extfoo
727   //       .long   0
728   //
729   MachineModuleInfoMachO &MachOMMI =
730     MMI->getObjFileInfo<MachineModuleInfoMachO>();
731   MCContext &Ctx = getContext();
732 
733   // The offset must consider the original displacement from the base symbol
734   // since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
735   Offset = -MV.getConstant();
736   const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
737 
738   // Access the final symbol via sym$non_lazy_ptr and generate the appropriated
739   // non_lazy_ptr stubs.
740   SmallString<128> Name;
741   StringRef Suffix = "$non_lazy_ptr";
742   Name += MMI->getModule()->getDataLayout().getPrivateGlobalPrefix();
743   Name += Sym->getName();
744   Name += Suffix;
745   MCSymbol *Stub = Ctx.getOrCreateSymbol(Name);
746 
747   MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
748   if (!StubSym.getPointer())
749     StubSym = MachineModuleInfoImpl::
750       StubValueTy(const_cast<MCSymbol *>(Sym), true /* access indirectly */);
751 
752   const MCExpr *BSymExpr =
753     MCSymbolRefExpr::create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
754   const MCExpr *LHS =
755     MCSymbolRefExpr::create(Stub, MCSymbolRefExpr::VK_None, Ctx);
756 
757   if (!Offset)
758     return MCBinaryExpr::createSub(LHS, BSymExpr, Ctx);
759 
760   const MCExpr *RHS =
761     MCBinaryExpr::createAdd(BSymExpr, MCConstantExpr::create(Offset, Ctx), Ctx);
762   return MCBinaryExpr::createSub(LHS, RHS, Ctx);
763 }
764 
765 //===----------------------------------------------------------------------===//
766 //                                  COFF
767 //===----------------------------------------------------------------------===//
768 
769 static unsigned
770 getCOFFSectionFlags(SectionKind K) {
771   unsigned Flags = 0;
772 
773   if (K.isMetadata())
774     Flags |=
775       COFF::IMAGE_SCN_MEM_DISCARDABLE;
776   else if (K.isText())
777     Flags |=
778       COFF::IMAGE_SCN_MEM_EXECUTE |
779       COFF::IMAGE_SCN_MEM_READ |
780       COFF::IMAGE_SCN_CNT_CODE;
781   else if (K.isBSS())
782     Flags |=
783       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
784       COFF::IMAGE_SCN_MEM_READ |
785       COFF::IMAGE_SCN_MEM_WRITE;
786   else if (K.isThreadLocal())
787     Flags |=
788       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
789       COFF::IMAGE_SCN_MEM_READ |
790       COFF::IMAGE_SCN_MEM_WRITE;
791   else if (K.isReadOnly() || K.isReadOnlyWithRel())
792     Flags |=
793       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
794       COFF::IMAGE_SCN_MEM_READ;
795   else if (K.isWriteable())
796     Flags |=
797       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
798       COFF::IMAGE_SCN_MEM_READ |
799       COFF::IMAGE_SCN_MEM_WRITE;
800 
801   return Flags;
802 }
803 
804 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
805   const Comdat *C = GV->getComdat();
806   assert(C && "expected GV to have a Comdat!");
807 
808   StringRef ComdatGVName = C->getName();
809   const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
810   if (!ComdatGV)
811     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
812                        "' does not exist.");
813 
814   if (ComdatGV->getComdat() != C)
815     report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
816                        "' is not a key for its COMDAT.");
817 
818   return ComdatGV;
819 }
820 
821 static int getSelectionForCOFF(const GlobalValue *GV) {
822   if (const Comdat *C = GV->getComdat()) {
823     const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
824     if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
825       ComdatKey = GA->getBaseObject();
826     if (ComdatKey == GV) {
827       switch (C->getSelectionKind()) {
828       case Comdat::Any:
829         return COFF::IMAGE_COMDAT_SELECT_ANY;
830       case Comdat::ExactMatch:
831         return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
832       case Comdat::Largest:
833         return COFF::IMAGE_COMDAT_SELECT_LARGEST;
834       case Comdat::NoDuplicates:
835         return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
836       case Comdat::SameSize:
837         return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
838       }
839     } else {
840       return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
841     }
842   }
843   return 0;
844 }
845 
846 MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
847     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
848     const TargetMachine &TM) const {
849   int Selection = 0;
850   unsigned Characteristics = getCOFFSectionFlags(Kind);
851   StringRef Name = GV->getSection();
852   StringRef COMDATSymName = "";
853   if (GV->hasComdat()) {
854     Selection = getSelectionForCOFF(GV);
855     const GlobalValue *ComdatGV;
856     if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
857       ComdatGV = getComdatGVForCOFF(GV);
858     else
859       ComdatGV = GV;
860 
861     if (!ComdatGV->hasPrivateLinkage()) {
862       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
863       COMDATSymName = Sym->getName();
864       Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
865     } else {
866       Selection = 0;
867     }
868   }
869   return getContext().getCOFFSection(Name,
870                                      Characteristics,
871                                      Kind,
872                                      COMDATSymName,
873                                      Selection);
874 }
875 
876 static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
877   if (Kind.isText())
878     return ".text";
879   if (Kind.isBSS())
880     return ".bss";
881   if (Kind.isThreadLocal())
882     return ".tls$";
883   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
884     return ".rdata";
885   return ".data";
886 }
887 
888 MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
889     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
890     const TargetMachine &TM) const {
891   // If we have -ffunction-sections then we should emit the global value to a
892   // uniqued section specifically for it.
893   bool EmitUniquedSection;
894   if (Kind.isText())
895     EmitUniquedSection = TM.getFunctionSections();
896   else
897     EmitUniquedSection = TM.getDataSections();
898 
899   if ((EmitUniquedSection && !Kind.isCommon()) || GV->hasComdat()) {
900     const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
901     unsigned Characteristics = getCOFFSectionFlags(Kind);
902 
903     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
904     int Selection = getSelectionForCOFF(GV);
905     if (!Selection)
906       Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
907     const GlobalValue *ComdatGV;
908     if (GV->hasComdat())
909       ComdatGV = getComdatGVForCOFF(GV);
910     else
911       ComdatGV = GV;
912 
913     if (!ComdatGV->hasPrivateLinkage()) {
914       MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
915       StringRef COMDATSymName = Sym->getName();
916       return getContext().getCOFFSection(Name, Characteristics, Kind,
917                                          COMDATSymName, Selection);
918     } else {
919       SmallString<256> TmpData;
920       getNameWithPrefix(TmpData, GV, /*CannotUsePrivateLabel=*/true, Mang, TM);
921       return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
922                                          Selection);
923     }
924   }
925 
926   if (Kind.isText())
927     return TextSection;
928 
929   if (Kind.isThreadLocal())
930     return TLSDataSection;
931 
932   if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
933     return ReadOnlySection;
934 
935   // Note: we claim that common symbols are put in BSSSection, but they are
936   // really emitted with the magic .comm directive, which creates a symbol table
937   // entry but not a section.
938   if (Kind.isBSS() || Kind.isCommon())
939     return BSSSection;
940 
941   return DataSection;
942 }
943 
944 void TargetLoweringObjectFileCOFF::getNameWithPrefix(
945     SmallVectorImpl<char> &OutName, const GlobalValue *GV,
946     bool CannotUsePrivateLabel, Mangler &Mang, const TargetMachine &TM) const {
947   if (GV->hasPrivateLinkage() &&
948       ((isa<Function>(GV) && TM.getFunctionSections()) ||
949        (isa<GlobalVariable>(GV) && TM.getDataSections())))
950     CannotUsePrivateLabel = true;
951 
952   Mang.getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
953 }
954 
955 MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
956     const Function &F, Mangler &Mang, const TargetMachine &TM) const {
957   // If the function can be removed, produce a unique section so that
958   // the table doesn't prevent the removal.
959   const Comdat *C = F.getComdat();
960   bool EmitUniqueSection = TM.getFunctionSections() || C;
961   if (!EmitUniqueSection)
962     return ReadOnlySection;
963 
964   // FIXME: we should produce a symbol for F instead.
965   if (F.hasPrivateLinkage())
966     return ReadOnlySection;
967 
968   MCSymbol *Sym = TM.getSymbol(&F, Mang);
969   StringRef COMDATSymName = Sym->getName();
970 
971   SectionKind Kind = SectionKind::getReadOnly();
972   const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
973   unsigned Characteristics = getCOFFSectionFlags(Kind);
974   Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
975 
976   return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
977                                      COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
978 }
979 
980 void TargetLoweringObjectFileCOFF::
981 emitModuleFlags(MCStreamer &Streamer,
982                 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
983                 Mangler &Mang, const TargetMachine &TM) const {
984   MDNode *LinkerOptions = nullptr;
985 
986   // Look for the "Linker Options" flag, since it's the only one we support.
987   for (ArrayRef<Module::ModuleFlagEntry>::iterator
988        i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
989     const Module::ModuleFlagEntry &MFE = *i;
990     StringRef Key = MFE.Key->getString();
991     Metadata *Val = MFE.Val;
992     if (Key == "Linker Options") {
993       LinkerOptions = cast<MDNode>(Val);
994       break;
995     }
996   }
997   if (!LinkerOptions)
998     return;
999 
1000   // Emit the linker options to the linker .drectve section.  According to the
1001   // spec, this section is a space-separated string containing flags for linker.
1002   MCSection *Sec = getDrectveSection();
1003   Streamer.SwitchSection(Sec);
1004   for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
1005     MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
1006     for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
1007       MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
1008       // Lead with a space for consistency with our dllexport implementation.
1009       std::string Directive(" ");
1010       Directive.append(MDOption->getString());
1011       Streamer.EmitBytes(Directive);
1012     }
1013   }
1014 }
1015 
1016 MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
1017     unsigned Priority, const MCSymbol *KeySym) const {
1018   return getContext().getAssociativeCOFFSection(
1019       cast<MCSectionCOFF>(StaticCtorSection), KeySym);
1020 }
1021 
1022 MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
1023     unsigned Priority, const MCSymbol *KeySym) const {
1024   return getContext().getAssociativeCOFFSection(
1025       cast<MCSectionCOFF>(StaticDtorSection), KeySym);
1026 }
1027 
1028 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
1029     raw_ostream &OS, const GlobalValue *GV, const Mangler &Mang) const {
1030   if (!GV->hasDLLExportStorageClass() || GV->isDeclaration())
1031     return;
1032 
1033   const Triple &TT = getTargetTriple();
1034 
1035   if (TT.isKnownWindowsMSVCEnvironment())
1036     OS << " /EXPORT:";
1037   else
1038     OS << " -export:";
1039 
1040   if (TT.isWindowsGNUEnvironment() || TT.isWindowsCygwinEnvironment()) {
1041     std::string Flag;
1042     raw_string_ostream FlagOS(Flag);
1043     Mang.getNameWithPrefix(FlagOS, GV, false);
1044     FlagOS.flush();
1045     if (Flag[0] == GV->getParent()->getDataLayout().getGlobalPrefix())
1046       OS << Flag.substr(1);
1047     else
1048       OS << Flag;
1049   } else {
1050     Mang.getNameWithPrefix(OS, GV, false);
1051   }
1052 
1053   if (!GV->getValueType()->isFunctionTy()) {
1054     if (TT.isKnownWindowsMSVCEnvironment())
1055       OS << ",DATA";
1056     else
1057       OS << ",data";
1058   }
1059 }
1060