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
getCFIPersonalitySymbol(const GlobalValue * GV,Mangler & Mang,const TargetMachine & TM,MachineModuleInfo * MMI) const47 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
emitPersonalityValue(MCStreamer & Streamer,const TargetMachine & TM,const MCSymbol * Sym) const59 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
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,Mangler & Mang,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const86 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
getELFKindForNamedSection(StringRef Name,SectionKind K)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
getELFSectionType(StringRef Name,SectionKind K)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
getELFSectionFlags(SectionKind K)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
getELFComdat(const GlobalValue * GV)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
getExplicitSectionGlobal(const GlobalValue * GV,SectionKind Kind,Mangler & Mang,const TargetMachine & TM) const207 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.
getSectionPrefixForGlobal(SectionKind Kind)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::
SelectSectionForGlobal(const GlobalValue * GV,SectionKind Kind,Mangler & Mang,const TargetMachine & TM) const246 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 *TargetLoweringObjectFileELF::
getSectionForConstant(SectionKind Kind) const342 getSectionForConstant(SectionKind Kind) const {
343 if (Kind.isMergeableConst4() && MergeableConst4Section)
344 return MergeableConst4Section;
345 if (Kind.isMergeableConst8() && MergeableConst8Section)
346 return MergeableConst8Section;
347 if (Kind.isMergeableConst16() && MergeableConst16Section)
348 return MergeableConst16Section;
349 if (Kind.isReadOnly())
350 return ReadOnlySection;
351
352 if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
353 assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
354 return DataRelROSection;
355 }
356
getStaticCtorSection(unsigned Priority,const MCSymbol * KeySym) const357 const MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
358 unsigned Priority, const MCSymbol *KeySym) const {
359 // The default scheme is .ctor / .dtor, so we have to invert the priority
360 // numbering.
361 if (Priority == 65535)
362 return StaticCtorSection;
363
364 if (UseInitArray) {
365 std::string Name = std::string(".init_array.") + utostr(Priority);
366 return getContext().getELFSection(Name, ELF::SHT_INIT_ARRAY,
367 ELF::SHF_ALLOC | ELF::SHF_WRITE,
368 SectionKind::getDataRel());
369 } else {
370 std::string Name = std::string(".ctors.") + utostr(65535 - Priority);
371 return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
372 ELF::SHF_ALLOC |ELF::SHF_WRITE,
373 SectionKind::getDataRel());
374 }
375 }
376
getStaticDtorSection(unsigned Priority,const MCSymbol * KeySym) const377 const MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
378 unsigned Priority, const MCSymbol *KeySym) const {
379 // The default scheme is .ctor / .dtor, so we have to invert the priority
380 // numbering.
381 if (Priority == 65535)
382 return StaticDtorSection;
383
384 if (UseInitArray) {
385 std::string Name = std::string(".fini_array.") + utostr(Priority);
386 return getContext().getELFSection(Name, ELF::SHT_FINI_ARRAY,
387 ELF::SHF_ALLOC | ELF::SHF_WRITE,
388 SectionKind::getDataRel());
389 } else {
390 std::string Name = std::string(".dtors.") + utostr(65535 - Priority);
391 return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
392 ELF::SHF_ALLOC |ELF::SHF_WRITE,
393 SectionKind::getDataRel());
394 }
395 }
396
397 void
InitializeELF(bool UseInitArray_)398 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
399 UseInitArray = UseInitArray_;
400 if (!UseInitArray)
401 return;
402
403 StaticCtorSection =
404 getContext().getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
405 ELF::SHF_WRITE |
406 ELF::SHF_ALLOC,
407 SectionKind::getDataRel());
408 StaticDtorSection =
409 getContext().getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
410 ELF::SHF_WRITE |
411 ELF::SHF_ALLOC,
412 SectionKind::getDataRel());
413 }
414
415 //===----------------------------------------------------------------------===//
416 // MachO
417 //===----------------------------------------------------------------------===//
418
419 /// getDepLibFromLinkerOpt - Extract the dependent library name from a linker
420 /// option string. Returns StringRef() if the option does not specify a library.
421 StringRef TargetLoweringObjectFileMachO::
getDepLibFromLinkerOpt(StringRef LinkerOption) const422 getDepLibFromLinkerOpt(StringRef LinkerOption) const {
423 const char *LibCmd = "-l";
424 if (LinkerOption.startswith(LibCmd))
425 return LinkerOption.substr(strlen(LibCmd));
426 return StringRef();
427 }
428
429 /// emitModuleFlags - Perform code emission for module flags.
430 void TargetLoweringObjectFileMachO::
emitModuleFlags(MCStreamer & Streamer,ArrayRef<Module::ModuleFlagEntry> ModuleFlags,Mangler & Mang,const TargetMachine & TM) const431 emitModuleFlags(MCStreamer &Streamer,
432 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
433 Mangler &Mang, const TargetMachine &TM) const {
434 unsigned VersionVal = 0;
435 unsigned ImageInfoFlags = 0;
436 MDNode *LinkerOptions = nullptr;
437 StringRef SectionVal;
438
439 for (ArrayRef<Module::ModuleFlagEntry>::iterator
440 i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
441 const Module::ModuleFlagEntry &MFE = *i;
442
443 // Ignore flags with 'Require' behavior.
444 if (MFE.Behavior == Module::Require)
445 continue;
446
447 StringRef Key = MFE.Key->getString();
448 Value *Val = MFE.Val;
449
450 if (Key == "Objective-C Image Info Version") {
451 VersionVal = cast<ConstantInt>(Val)->getZExtValue();
452 } else if (Key == "Objective-C Garbage Collection" ||
453 Key == "Objective-C GC Only" ||
454 Key == "Objective-C Is Simulated") {
455 ImageInfoFlags |= cast<ConstantInt>(Val)->getZExtValue();
456 } else if (Key == "Objective-C Image Info Section") {
457 SectionVal = cast<MDString>(Val)->getString();
458 } else if (Key == "Linker Options") {
459 LinkerOptions = cast<MDNode>(Val);
460 }
461 }
462
463 // Emit the linker options if present.
464 if (LinkerOptions) {
465 for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
466 MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
467 SmallVector<std::string, 4> StrOptions;
468
469 // Convert to strings.
470 for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
471 MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
472 StrOptions.push_back(MDOption->getString());
473 }
474
475 Streamer.EmitLinkerOptions(StrOptions);
476 }
477 }
478
479 // The section is mandatory. If we don't have it, then we don't have GC info.
480 if (SectionVal.empty()) return;
481
482 StringRef Segment, Section;
483 unsigned TAA = 0, StubSize = 0;
484 bool TAAParsed;
485 std::string ErrorCode =
486 MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
487 TAA, TAAParsed, StubSize);
488 if (!ErrorCode.empty())
489 // If invalid, report the error with report_fatal_error.
490 report_fatal_error("Invalid section specifier '" + Section + "': " +
491 ErrorCode + ".");
492
493 // Get the section.
494 const MCSectionMachO *S =
495 getContext().getMachOSection(Segment, Section, TAA, StubSize,
496 SectionKind::getDataNoRel());
497 Streamer.SwitchSection(S);
498 Streamer.EmitLabel(getContext().
499 GetOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
500 Streamer.EmitIntValue(VersionVal, 4);
501 Streamer.EmitIntValue(ImageInfoFlags, 4);
502 Streamer.AddBlankLine();
503 }
504
checkMachOComdat(const GlobalValue * GV)505 static void checkMachOComdat(const GlobalValue *GV) {
506 const Comdat *C = GV->getComdat();
507 if (!C)
508 return;
509
510 report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
511 "' cannot be lowered.");
512 }
513
getExplicitSectionGlobal(const GlobalValue * GV,SectionKind Kind,Mangler & Mang,const TargetMachine & TM) const514 const MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
515 const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
516 const TargetMachine &TM) const {
517 // Parse the section specifier and create it if valid.
518 StringRef Segment, Section;
519 unsigned TAA = 0, StubSize = 0;
520 bool TAAParsed;
521
522 checkMachOComdat(GV);
523
524 std::string ErrorCode =
525 MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
526 TAA, TAAParsed, StubSize);
527 if (!ErrorCode.empty()) {
528 // If invalid, report the error with report_fatal_error.
529 report_fatal_error("Global variable '" + GV->getName() +
530 "' has an invalid section specifier '" +
531 GV->getSection() + "': " + ErrorCode + ".");
532 }
533
534 // Get the section.
535 const MCSectionMachO *S =
536 getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
537
538 // If TAA wasn't set by ParseSectionSpecifier() above,
539 // use the value returned by getMachOSection() as a default.
540 if (!TAAParsed)
541 TAA = S->getTypeAndAttributes();
542
543 // Okay, now that we got the section, verify that the TAA & StubSize agree.
544 // If the user declared multiple globals with different section flags, we need
545 // to reject it here.
546 if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
547 // If invalid, report the error with report_fatal_error.
548 report_fatal_error("Global variable '" + GV->getName() +
549 "' section type or attributes does not match previous"
550 " section specifier");
551 }
552
553 return S;
554 }
555
isSectionAtomizableBySymbols(const MCSection & Section) const556 bool TargetLoweringObjectFileMachO::isSectionAtomizableBySymbols(
557 const MCSection &Section) const {
558 const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
559
560 // Sections holding 1 byte strings are atomized based on the data
561 // they contain.
562 // Sections holding 2 byte strings require symbols in order to be
563 // atomized.
564 // There is no dedicated section for 4 byte strings.
565 if (SMO.getKind().isMergeable1ByteCString())
566 return false;
567
568 if (SMO.getSegmentName() == "__DATA" &&
569 SMO.getSectionName() == "__cfstring")
570 return false;
571
572 switch (SMO.getType()) {
573 default:
574 return true;
575
576 // These sections are atomized at the element boundaries without using
577 // symbols.
578 case MachO::S_4BYTE_LITERALS:
579 case MachO::S_8BYTE_LITERALS:
580 case MachO::S_16BYTE_LITERALS:
581 case MachO::S_LITERAL_POINTERS:
582 case MachO::S_NON_LAZY_SYMBOL_POINTERS:
583 case MachO::S_LAZY_SYMBOL_POINTERS:
584 case MachO::S_MOD_INIT_FUNC_POINTERS:
585 case MachO::S_MOD_TERM_FUNC_POINTERS:
586 case MachO::S_INTERPOSING:
587 return false;
588 }
589 }
590
591 const MCSection *TargetLoweringObjectFileMachO::
SelectSectionForGlobal(const GlobalValue * GV,SectionKind Kind,Mangler & Mang,const TargetMachine & TM) const592 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
593 Mangler &Mang, const TargetMachine &TM) const {
594 checkMachOComdat(GV);
595
596 // Handle thread local data.
597 if (Kind.isThreadBSS()) return TLSBSSSection;
598 if (Kind.isThreadData()) return TLSDataSection;
599
600 if (Kind.isText())
601 return GV->isWeakForLinker() ? TextCoalSection : TextSection;
602
603 // If this is weak/linkonce, put this in a coalescable section, either in text
604 // or data depending on if it is writable.
605 if (GV->isWeakForLinker()) {
606 if (Kind.isReadOnly())
607 return ConstTextCoalSection;
608 return DataCoalSection;
609 }
610
611 // FIXME: Alignment check should be handled by section classifier.
612 if (Kind.isMergeable1ByteCString() &&
613 TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
614 return CStringSection;
615
616 // Do not put 16-bit arrays in the UString section if they have an
617 // externally visible label, this runs into issues with certain linker
618 // versions.
619 if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
620 TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
621 return UStringSection;
622
623 if (Kind.isMergeableConst()) {
624 if (Kind.isMergeableConst4())
625 return FourByteConstantSection;
626 if (Kind.isMergeableConst8())
627 return EightByteConstantSection;
628 if (Kind.isMergeableConst16())
629 return SixteenByteConstantSection;
630 }
631
632 // Otherwise, if it is readonly, but not something we can specially optimize,
633 // just drop it in .const.
634 if (Kind.isReadOnly())
635 return ReadOnlySection;
636
637 // If this is marked const, put it into a const section. But if the dynamic
638 // linker needs to write to it, put it in the data segment.
639 if (Kind.isReadOnlyWithRel())
640 return ConstDataSection;
641
642 // Put zero initialized globals with strong external linkage in the
643 // DATA, __common section with the .zerofill directive.
644 if (Kind.isBSSExtern())
645 return DataCommonSection;
646
647 // Put zero initialized globals with local linkage in __DATA,__bss directive
648 // with the .zerofill directive (aka .lcomm).
649 if (Kind.isBSSLocal())
650 return DataBSSSection;
651
652 // Otherwise, just drop the variable in the normal data section.
653 return DataSection;
654 }
655
656 const MCSection *
getSectionForConstant(SectionKind Kind) const657 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
658 // If this constant requires a relocation, we have to put it in the data
659 // segment, not in the text segment.
660 if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
661 return ConstDataSection;
662
663 if (Kind.isMergeableConst4())
664 return FourByteConstantSection;
665 if (Kind.isMergeableConst8())
666 return EightByteConstantSection;
667 if (Kind.isMergeableConst16())
668 return SixteenByteConstantSection;
669 return ReadOnlySection; // .const
670 }
671
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,Mangler & Mang,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const672 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
673 const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
674 const TargetMachine &TM, MachineModuleInfo *MMI,
675 MCStreamer &Streamer) const {
676 // The mach-o version of this method defaults to returning a stub reference.
677
678 if (Encoding & DW_EH_PE_indirect) {
679 MachineModuleInfoMachO &MachOMMI =
680 MMI->getObjFileInfo<MachineModuleInfoMachO>();
681
682 MCSymbol *SSym =
683 getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
684
685 // Add information about the stub reference to MachOMMI so that the stub
686 // gets emitted by the asmprinter.
687 MachineModuleInfoImpl::StubValueTy &StubSym =
688 GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
689 MachOMMI.getGVStubEntry(SSym);
690 if (!StubSym.getPointer()) {
691 MCSymbol *Sym = TM.getSymbol(GV, Mang);
692 StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
693 }
694
695 return TargetLoweringObjectFile::
696 getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
697 Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
698 }
699
700 return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
701 TM, MMI, Streamer);
702 }
703
getCFIPersonalitySymbol(const GlobalValue * GV,Mangler & Mang,const TargetMachine & TM,MachineModuleInfo * MMI) const704 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
705 const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
706 MachineModuleInfo *MMI) const {
707 // The mach-o version of this method defaults to returning a stub reference.
708 MachineModuleInfoMachO &MachOMMI =
709 MMI->getObjFileInfo<MachineModuleInfoMachO>();
710
711 MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, TM);
712
713 // Add information about the stub reference to MachOMMI so that the stub
714 // gets emitted by the asmprinter.
715 MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
716 if (!StubSym.getPointer()) {
717 MCSymbol *Sym = TM.getSymbol(GV, Mang);
718 StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
719 }
720
721 return SSym;
722 }
723
724 //===----------------------------------------------------------------------===//
725 // COFF
726 //===----------------------------------------------------------------------===//
727
728 static unsigned
getCOFFSectionFlags(SectionKind K)729 getCOFFSectionFlags(SectionKind K) {
730 unsigned Flags = 0;
731
732 if (K.isMetadata())
733 Flags |=
734 COFF::IMAGE_SCN_MEM_DISCARDABLE;
735 else if (K.isText())
736 Flags |=
737 COFF::IMAGE_SCN_MEM_EXECUTE |
738 COFF::IMAGE_SCN_MEM_READ |
739 COFF::IMAGE_SCN_CNT_CODE;
740 else if (K.isBSS ())
741 Flags |=
742 COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
743 COFF::IMAGE_SCN_MEM_READ |
744 COFF::IMAGE_SCN_MEM_WRITE;
745 else if (K.isThreadLocal())
746 Flags |=
747 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
748 COFF::IMAGE_SCN_MEM_READ |
749 COFF::IMAGE_SCN_MEM_WRITE;
750 else if (K.isReadOnly())
751 Flags |=
752 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
753 COFF::IMAGE_SCN_MEM_READ;
754 else if (K.isWriteable())
755 Flags |=
756 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
757 COFF::IMAGE_SCN_MEM_READ |
758 COFF::IMAGE_SCN_MEM_WRITE;
759
760 return Flags;
761 }
762
getComdatGVForCOFF(const GlobalValue * GV)763 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
764 const Comdat *C = GV->getComdat();
765 assert(C && "expected GV to have a Comdat!");
766
767 StringRef ComdatGVName = C->getName();
768 const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
769 if (!ComdatGV)
770 report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
771 "' does not exist.");
772
773 if (ComdatGV->getComdat() != C)
774 report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
775 "' is not a key for it's COMDAT.");
776
777 return ComdatGV;
778 }
779
getSelectionForCOFF(const GlobalValue * GV)780 static int getSelectionForCOFF(const GlobalValue *GV) {
781 if (const Comdat *C = GV->getComdat()) {
782 const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
783 if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
784 ComdatKey = GA->getBaseObject();
785 if (ComdatKey == GV) {
786 switch (C->getSelectionKind()) {
787 case Comdat::Any:
788 return COFF::IMAGE_COMDAT_SELECT_ANY;
789 case Comdat::ExactMatch:
790 return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
791 case Comdat::Largest:
792 return COFF::IMAGE_COMDAT_SELECT_LARGEST;
793 case Comdat::NoDuplicates:
794 return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
795 case Comdat::SameSize:
796 return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
797 }
798 } else {
799 return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
800 }
801 } else if (GV->isWeakForLinker()) {
802 return COFF::IMAGE_COMDAT_SELECT_ANY;
803 }
804 return 0;
805 }
806
getExplicitSectionGlobal(const GlobalValue * GV,SectionKind Kind,Mangler & Mang,const TargetMachine & TM) const807 const MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
808 const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
809 const TargetMachine &TM) const {
810 int Selection = 0;
811 unsigned Characteristics = getCOFFSectionFlags(Kind);
812 StringRef Name = GV->getSection();
813 StringRef COMDATSymName = "";
814 if ((GV->isWeakForLinker() || GV->hasComdat()) && !Kind.isCommon()) {
815 Selection = getSelectionForCOFF(GV);
816 const GlobalValue *ComdatGV;
817 if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
818 ComdatGV = getComdatGVForCOFF(GV);
819 else
820 ComdatGV = GV;
821
822 if (!ComdatGV->hasPrivateLinkage()) {
823 MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
824 COMDATSymName = Sym->getName();
825 Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
826 } else {
827 Selection = 0;
828 }
829 }
830 return getContext().getCOFFSection(Name,
831 Characteristics,
832 Kind,
833 COMDATSymName,
834 Selection);
835 }
836
getCOFFSectionNameForUniqueGlobal(SectionKind Kind)837 static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
838 if (Kind.isText())
839 return ".text";
840 if (Kind.isBSS())
841 return ".bss";
842 if (Kind.isThreadLocal())
843 return ".tls$";
844 if (Kind.isWriteable())
845 return ".data";
846 return ".rdata";
847 }
848
849
850 const MCSection *TargetLoweringObjectFileCOFF::
SelectSectionForGlobal(const GlobalValue * GV,SectionKind Kind,Mangler & Mang,const TargetMachine & TM) const851 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
852 Mangler &Mang, const TargetMachine &TM) const {
853 // If we have -ffunction-sections then we should emit the global value to a
854 // uniqued section specifically for it.
855 bool EmitUniquedSection;
856 if (Kind.isText())
857 EmitUniquedSection = TM.getFunctionSections();
858 else
859 EmitUniquedSection = TM.getDataSections();
860
861 // If this global is linkonce/weak and the target handles this by emitting it
862 // into a 'uniqued' section name, create and return the section now.
863 // Section names depend on the name of the symbol which is not feasible if the
864 // symbol has private linkage.
865 if ((GV->isWeakForLinker() || EmitUniquedSection || GV->hasComdat()) &&
866 !Kind.isCommon()) {
867 const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
868 unsigned Characteristics = getCOFFSectionFlags(Kind);
869
870 Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
871 int Selection = getSelectionForCOFF(GV);
872 if (!Selection)
873 Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
874 const GlobalValue *ComdatGV;
875 if (GV->hasComdat())
876 ComdatGV = getComdatGVForCOFF(GV);
877 else
878 ComdatGV = GV;
879
880 if (!ComdatGV->hasPrivateLinkage()) {
881 MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
882 StringRef COMDATSymName = Sym->getName();
883 return getContext().getCOFFSection(Name, Characteristics, Kind,
884 COMDATSymName, Selection);
885 }
886 }
887
888 if (Kind.isText())
889 return TextSection;
890
891 if (Kind.isThreadLocal())
892 return TLSDataSection;
893
894 if (Kind.isReadOnly())
895 return ReadOnlySection;
896
897 // Note: we claim that common symbols are put in BSSSection, but they are
898 // really emitted with the magic .comm directive, which creates a symbol table
899 // entry but not a section.
900 if (Kind.isBSS() || Kind.isCommon())
901 return BSSSection;
902
903 return DataSection;
904 }
905
906 StringRef TargetLoweringObjectFileCOFF::
getDepLibFromLinkerOpt(StringRef LinkerOption) const907 getDepLibFromLinkerOpt(StringRef LinkerOption) const {
908 const char *LibCmd = "/DEFAULTLIB:";
909 if (LinkerOption.startswith(LibCmd))
910 return LinkerOption.substr(strlen(LibCmd));
911 return StringRef();
912 }
913
914 void TargetLoweringObjectFileCOFF::
emitModuleFlags(MCStreamer & Streamer,ArrayRef<Module::ModuleFlagEntry> ModuleFlags,Mangler & Mang,const TargetMachine & TM) const915 emitModuleFlags(MCStreamer &Streamer,
916 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
917 Mangler &Mang, const TargetMachine &TM) const {
918 MDNode *LinkerOptions = nullptr;
919
920 // Look for the "Linker Options" flag, since it's the only one we support.
921 for (ArrayRef<Module::ModuleFlagEntry>::iterator
922 i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
923 const Module::ModuleFlagEntry &MFE = *i;
924 StringRef Key = MFE.Key->getString();
925 Value *Val = MFE.Val;
926 if (Key == "Linker Options") {
927 LinkerOptions = cast<MDNode>(Val);
928 break;
929 }
930 }
931 if (!LinkerOptions)
932 return;
933
934 // Emit the linker options to the linker .drectve section. According to the
935 // spec, this section is a space-separated string containing flags for linker.
936 const MCSection *Sec = getDrectveSection();
937 Streamer.SwitchSection(Sec);
938 for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
939 MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
940 for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
941 MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
942 StringRef Op = MDOption->getString();
943 // Lead with a space for consistency with our dllexport implementation.
944 std::string Escaped(" ");
945 if (Op.find(" ") != StringRef::npos) {
946 // The PE-COFF spec says args with spaces must be quoted. It doesn't say
947 // how to escape quotes, but it probably uses this algorithm:
948 // http://msdn.microsoft.com/en-us/library/17w5ykft(v=vs.85).aspx
949 // FIXME: Reuse escaping code from Support/Windows/Program.inc
950 Escaped.push_back('\"');
951 Escaped.append(Op);
952 Escaped.push_back('\"');
953 } else {
954 Escaped.append(Op);
955 }
956 Streamer.EmitBytes(Escaped);
957 }
958 }
959 }
960
getAssociativeCOFFSection(MCContext & Ctx,const MCSection * Sec,const MCSymbol * KeySym)961 static const MCSection *getAssociativeCOFFSection(MCContext &Ctx,
962 const MCSection *Sec,
963 const MCSymbol *KeySym) {
964 // Return the normal section if we don't have to be associative.
965 if (!KeySym)
966 return Sec;
967
968 // Make an associative section with the same name and kind as the normal
969 // section.
970 const MCSectionCOFF *SecCOFF = cast<MCSectionCOFF>(Sec);
971 unsigned Characteristics =
972 SecCOFF->getCharacteristics() | COFF::IMAGE_SCN_LNK_COMDAT;
973 return Ctx.getCOFFSection(SecCOFF->getSectionName(), Characteristics,
974 SecCOFF->getKind(), KeySym->getName(),
975 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
976 }
977
getStaticCtorSection(unsigned Priority,const MCSymbol * KeySym) const978 const MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
979 unsigned Priority, const MCSymbol *KeySym) const {
980 return getAssociativeCOFFSection(getContext(), StaticCtorSection, KeySym);
981 }
982
getStaticDtorSection(unsigned Priority,const MCSymbol * KeySym) const983 const MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
984 unsigned Priority, const MCSymbol *KeySym) const {
985 return getAssociativeCOFFSection(getContext(), StaticDtorSection, KeySym);
986 }
987