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/Module.h"
26 #include "llvm/MC/MCContext.h"
27 #include "llvm/MC/MCExpr.h"
28 #include "llvm/MC/MCSectionCOFF.h"
29 #include "llvm/MC/MCSectionELF.h"
30 #include "llvm/MC/MCSectionMachO.h"
31 #include "llvm/MC/MCStreamer.h"
32 #include "llvm/MC/MCSymbol.h"
33 #include "llvm/Support/Dwarf.h"
34 #include "llvm/Support/ELF.h"
35 #include "llvm/Support/ErrorHandling.h"
36 #include "llvm/Support/raw_ostream.h"
37 #include "llvm/Target/Mangler.h"
38 #include "llvm/Target/TargetMachine.h"
39 using namespace llvm;
40 using namespace dwarf;
41
42 //===----------------------------------------------------------------------===//
43 // ELF
44 //===----------------------------------------------------------------------===//
45
46 MCSymbol *
getCFIPersonalitySymbol(const GlobalValue * GV,Mangler * Mang,MachineModuleInfo * MMI) const47 TargetLoweringObjectFileELF::getCFIPersonalitySymbol(const GlobalValue *GV,
48 Mangler *Mang,
49 MachineModuleInfo *MMI) const {
50 unsigned Encoding = getPersonalityEncoding();
51 switch (Encoding & 0x70) {
52 default:
53 report_fatal_error("We do not support this DWARF encoding yet!");
54 case dwarf::DW_EH_PE_absptr:
55 return Mang->getSymbol(GV);
56 case dwarf::DW_EH_PE_pcrel: {
57 return getContext().GetOrCreateSymbol(StringRef("DW.ref.") +
58 Mang->getSymbol(GV)->getName());
59 }
60 }
61 }
62
emitPersonalityValue(MCStreamer & Streamer,const TargetMachine & TM,const MCSymbol * Sym) const63 void TargetLoweringObjectFileELF::emitPersonalityValue(MCStreamer &Streamer,
64 const TargetMachine &TM,
65 const MCSymbol *Sym) const {
66 SmallString<64> NameData("DW.ref.");
67 NameData += Sym->getName();
68 MCSymbol *Label = getContext().GetOrCreateSymbol(NameData);
69 Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
70 Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
71 StringRef Prefix = ".data.";
72 NameData.insert(NameData.begin(), Prefix.begin(), Prefix.end());
73 unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
74 const MCSection *Sec = getContext().getELFSection(NameData,
75 ELF::SHT_PROGBITS,
76 Flags,
77 SectionKind::getDataRel(),
78 0, Label->getName());
79 unsigned Size = TM.getDataLayout()->getPointerSize();
80 Streamer.SwitchSection(Sec);
81 Streamer.EmitValueToAlignment(TM.getDataLayout()->getPointerABIAlignment());
82 Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
83 const MCExpr *E = MCConstantExpr::Create(Size, getContext());
84 Streamer.EmitELFSize(Label, E);
85 Streamer.EmitLabel(Label);
86
87 Streamer.EmitSymbolValue(Sym, Size);
88 }
89
90 const MCExpr *TargetLoweringObjectFileELF::
getTTypeGlobalReference(const GlobalValue * GV,Mangler * Mang,MachineModuleInfo * MMI,unsigned Encoding,MCStreamer & Streamer) const91 getTTypeGlobalReference(const GlobalValue *GV, Mangler *Mang,
92 MachineModuleInfo *MMI, unsigned Encoding,
93 MCStreamer &Streamer) const {
94
95 if (Encoding & dwarf::DW_EH_PE_indirect) {
96 MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
97
98 SmallString<128> Name;
99 Mang->getNameWithPrefix(Name, GV, true);
100 Name += ".DW.stub";
101
102 // Add information about the stub reference to ELFMMI so that the stub
103 // gets emitted by the asmprinter.
104 MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
105 MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
106 if (StubSym.getPointer() == 0) {
107 MCSymbol *Sym = Mang->getSymbol(GV);
108 StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
109 }
110
111 return TargetLoweringObjectFile::
112 getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
113 Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
114 }
115
116 return TargetLoweringObjectFile::
117 getTTypeGlobalReference(GV, Mang, MMI, Encoding, Streamer);
118 }
119
120 static SectionKind
getELFKindForNamedSection(StringRef Name,SectionKind K)121 getELFKindForNamedSection(StringRef Name, SectionKind K) {
122 // N.B.: The defaults used in here are no the same ones used in MC.
123 // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
124 // both gas and MC will produce a section with no flags. Given
125 // section(".eh_frame") gcc will produce:
126 //
127 // .section .eh_frame,"a",@progbits
128 if (Name.empty() || Name[0] != '.') return K;
129
130 // Some lame default implementation based on some magic section names.
131 if (Name == ".bss" ||
132 Name.startswith(".bss.") ||
133 Name.startswith(".gnu.linkonce.b.") ||
134 Name.startswith(".llvm.linkonce.b.") ||
135 Name == ".sbss" ||
136 Name.startswith(".sbss.") ||
137 Name.startswith(".gnu.linkonce.sb.") ||
138 Name.startswith(".llvm.linkonce.sb."))
139 return SectionKind::getBSS();
140
141 if (Name == ".tdata" ||
142 Name.startswith(".tdata.") ||
143 Name.startswith(".gnu.linkonce.td.") ||
144 Name.startswith(".llvm.linkonce.td."))
145 return SectionKind::getThreadData();
146
147 if (Name == ".tbss" ||
148 Name.startswith(".tbss.") ||
149 Name.startswith(".gnu.linkonce.tb.") ||
150 Name.startswith(".llvm.linkonce.tb."))
151 return SectionKind::getThreadBSS();
152
153 return K;
154 }
155
156
getELFSectionType(StringRef Name,SectionKind K)157 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
158
159 if (Name == ".init_array")
160 return ELF::SHT_INIT_ARRAY;
161
162 if (Name == ".fini_array")
163 return ELF::SHT_FINI_ARRAY;
164
165 if (Name == ".preinit_array")
166 return ELF::SHT_PREINIT_ARRAY;
167
168 if (K.isBSS() || K.isThreadBSS())
169 return ELF::SHT_NOBITS;
170
171 return ELF::SHT_PROGBITS;
172 }
173
174
175 static unsigned
getELFSectionFlags(SectionKind K)176 getELFSectionFlags(SectionKind K) {
177 unsigned Flags = 0;
178
179 if (!K.isMetadata())
180 Flags |= ELF::SHF_ALLOC;
181
182 if (K.isText())
183 Flags |= ELF::SHF_EXECINSTR;
184
185 if (K.isWriteable())
186 Flags |= ELF::SHF_WRITE;
187
188 if (K.isThreadLocal())
189 Flags |= ELF::SHF_TLS;
190
191 // K.isMergeableConst() is left out to honour PR4650
192 if (K.isMergeableCString() || K.isMergeableConst4() ||
193 K.isMergeableConst8() || K.isMergeableConst16())
194 Flags |= ELF::SHF_MERGE;
195
196 if (K.isMergeableCString())
197 Flags |= ELF::SHF_STRINGS;
198
199 return Flags;
200 }
201
202
203 const MCSection *TargetLoweringObjectFileELF::
getExplicitSectionGlobal(const GlobalValue * GV,SectionKind Kind,Mangler * Mang,const TargetMachine & TM) const204 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
205 Mangler *Mang, const TargetMachine &TM) const {
206 StringRef SectionName = GV->getSection();
207
208 // Infer section flags from the section name if we can.
209 Kind = getELFKindForNamedSection(SectionName, Kind);
210
211 return getContext().getELFSection(SectionName,
212 getELFSectionType(SectionName, Kind),
213 getELFSectionFlags(Kind), Kind);
214 }
215
216 /// getSectionPrefixForGlobal - Return the section prefix name used by options
217 /// FunctionsSections and DataSections.
getSectionPrefixForGlobal(SectionKind Kind)218 static const char *getSectionPrefixForGlobal(SectionKind Kind) {
219 if (Kind.isText()) return ".text.";
220 if (Kind.isReadOnly()) return ".rodata.";
221 if (Kind.isBSS()) return ".bss.";
222
223 if (Kind.isThreadData()) return ".tdata.";
224 if (Kind.isThreadBSS()) return ".tbss.";
225
226 if (Kind.isDataNoRel()) return ".data.";
227 if (Kind.isDataRelLocal()) return ".data.rel.local.";
228 if (Kind.isDataRel()) return ".data.rel.";
229 if (Kind.isReadOnlyWithRelLocal()) return ".data.rel.ro.local.";
230
231 assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
232 return ".data.rel.ro.";
233 }
234
235
236 const MCSection *TargetLoweringObjectFileELF::
SelectSectionForGlobal(const GlobalValue * GV,SectionKind Kind,Mangler * Mang,const TargetMachine & TM) const237 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
238 Mangler *Mang, const TargetMachine &TM) const {
239 // If we have -ffunction-section or -fdata-section then we should emit the
240 // global value to a uniqued section specifically for it.
241 bool EmitUniquedSection;
242 if (Kind.isText())
243 EmitUniquedSection = TM.getFunctionSections();
244 else
245 EmitUniquedSection = TM.getDataSections();
246
247 // If this global is linkonce/weak and the target handles this by emitting it
248 // into a 'uniqued' section name, create and return the section now.
249 if ((GV->isWeakForLinker() || EmitUniquedSection) &&
250 !Kind.isCommon()) {
251 const char *Prefix;
252 Prefix = getSectionPrefixForGlobal(Kind);
253
254 SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
255 MCSymbol *Sym = Mang->getSymbol(GV);
256 Name.append(Sym->getName().begin(), Sym->getName().end());
257 StringRef Group = "";
258 unsigned Flags = getELFSectionFlags(Kind);
259 if (GV->isWeakForLinker()) {
260 Group = Sym->getName();
261 Flags |= ELF::SHF_GROUP;
262 }
263
264 return getContext().getELFSection(Name.str(),
265 getELFSectionType(Name.str(), Kind),
266 Flags, Kind, 0, Group);
267 }
268
269 if (Kind.isText()) return TextSection;
270
271 if (Kind.isMergeable1ByteCString() ||
272 Kind.isMergeable2ByteCString() ||
273 Kind.isMergeable4ByteCString()) {
274
275 // We also need alignment here.
276 // FIXME: this is getting the alignment of the character, not the
277 // alignment of the global!
278 unsigned Align =
279 TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV));
280
281 const char *SizeSpec = ".rodata.str1.";
282 if (Kind.isMergeable2ByteCString())
283 SizeSpec = ".rodata.str2.";
284 else if (Kind.isMergeable4ByteCString())
285 SizeSpec = ".rodata.str4.";
286 else
287 assert(Kind.isMergeable1ByteCString() && "unknown string width");
288
289
290 std::string Name = SizeSpec + utostr(Align);
291 return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
292 ELF::SHF_ALLOC |
293 ELF::SHF_MERGE |
294 ELF::SHF_STRINGS,
295 Kind);
296 }
297
298 if (Kind.isMergeableConst()) {
299 if (Kind.isMergeableConst4() && MergeableConst4Section)
300 return MergeableConst4Section;
301 if (Kind.isMergeableConst8() && MergeableConst8Section)
302 return MergeableConst8Section;
303 if (Kind.isMergeableConst16() && MergeableConst16Section)
304 return MergeableConst16Section;
305 return ReadOnlySection; // .const
306 }
307
308 if (Kind.isReadOnly()) return ReadOnlySection;
309
310 if (Kind.isThreadData()) return TLSDataSection;
311 if (Kind.isThreadBSS()) return TLSBSSSection;
312
313 // Note: we claim that common symbols are put in BSSSection, but they are
314 // really emitted with the magic .comm directive, which creates a symbol table
315 // entry but not a section.
316 if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
317
318 if (Kind.isDataNoRel()) return DataSection;
319 if (Kind.isDataRelLocal()) return DataRelLocalSection;
320 if (Kind.isDataRel()) return DataRelSection;
321 if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
322
323 assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
324 return DataRelROSection;
325 }
326
327 /// getSectionForConstant - Given a mergeable constant with the
328 /// specified size and relocation information, return a section that it
329 /// should be placed in.
330 const MCSection *TargetLoweringObjectFileELF::
getSectionForConstant(SectionKind Kind) const331 getSectionForConstant(SectionKind Kind) const {
332 if (Kind.isMergeableConst4() && MergeableConst4Section)
333 return MergeableConst4Section;
334 if (Kind.isMergeableConst8() && MergeableConst8Section)
335 return MergeableConst8Section;
336 if (Kind.isMergeableConst16() && MergeableConst16Section)
337 return MergeableConst16Section;
338 if (Kind.isReadOnly())
339 return ReadOnlySection;
340
341 if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
342 assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
343 return DataRelROSection;
344 }
345
346 const MCSection *
getStaticCtorSection(unsigned Priority) const347 TargetLoweringObjectFileELF::getStaticCtorSection(unsigned Priority) const {
348 // The default scheme is .ctor / .dtor, so we have to invert the priority
349 // numbering.
350 if (Priority == 65535)
351 return StaticCtorSection;
352
353 if (UseInitArray) {
354 std::string Name = std::string(".init_array.") + utostr(Priority);
355 return getContext().getELFSection(Name, ELF::SHT_INIT_ARRAY,
356 ELF::SHF_ALLOC | ELF::SHF_WRITE,
357 SectionKind::getDataRel());
358 } else {
359 std::string Name = std::string(".ctors.") + utostr(65535 - Priority);
360 return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
361 ELF::SHF_ALLOC |ELF::SHF_WRITE,
362 SectionKind::getDataRel());
363 }
364 }
365
366 const MCSection *
getStaticDtorSection(unsigned Priority) const367 TargetLoweringObjectFileELF::getStaticDtorSection(unsigned Priority) const {
368 // The default scheme is .ctor / .dtor, so we have to invert the priority
369 // numbering.
370 if (Priority == 65535)
371 return StaticDtorSection;
372
373 if (UseInitArray) {
374 std::string Name = std::string(".fini_array.") + utostr(Priority);
375 return getContext().getELFSection(Name, ELF::SHT_FINI_ARRAY,
376 ELF::SHF_ALLOC | ELF::SHF_WRITE,
377 SectionKind::getDataRel());
378 } else {
379 std::string Name = std::string(".dtors.") + utostr(65535 - Priority);
380 return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
381 ELF::SHF_ALLOC |ELF::SHF_WRITE,
382 SectionKind::getDataRel());
383 }
384 }
385
386 void
InitializeELF(bool UseInitArray_)387 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
388 UseInitArray = UseInitArray_;
389 if (!UseInitArray)
390 return;
391
392 StaticCtorSection =
393 getContext().getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
394 ELF::SHF_WRITE |
395 ELF::SHF_ALLOC,
396 SectionKind::getDataRel());
397 StaticDtorSection =
398 getContext().getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
399 ELF::SHF_WRITE |
400 ELF::SHF_ALLOC,
401 SectionKind::getDataRel());
402 }
403
404 //===----------------------------------------------------------------------===//
405 // MachO
406 //===----------------------------------------------------------------------===//
407
408 /// emitModuleFlags - Perform code emission for module flags.
409 void TargetLoweringObjectFileMachO::
emitModuleFlags(MCStreamer & Streamer,ArrayRef<Module::ModuleFlagEntry> ModuleFlags,Mangler * Mang,const TargetMachine & TM) const410 emitModuleFlags(MCStreamer &Streamer,
411 ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
412 Mangler *Mang, const TargetMachine &TM) const {
413 unsigned VersionVal = 0;
414 unsigned ImageInfoFlags = 0;
415 MDNode *LinkerOptions = 0;
416 StringRef SectionVal;
417
418 for (ArrayRef<Module::ModuleFlagEntry>::iterator
419 i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
420 const Module::ModuleFlagEntry &MFE = *i;
421
422 // Ignore flags with 'Require' behavior.
423 if (MFE.Behavior == Module::Require)
424 continue;
425
426 StringRef Key = MFE.Key->getString();
427 Value *Val = MFE.Val;
428
429 if (Key == "Objective-C Image Info Version") {
430 VersionVal = cast<ConstantInt>(Val)->getZExtValue();
431 } else if (Key == "Objective-C Garbage Collection" ||
432 Key == "Objective-C GC Only" ||
433 Key == "Objective-C Is Simulated") {
434 ImageInfoFlags |= cast<ConstantInt>(Val)->getZExtValue();
435 } else if (Key == "Objective-C Image Info Section") {
436 SectionVal = cast<MDString>(Val)->getString();
437 } else if (Key == "Linker Options") {
438 LinkerOptions = cast<MDNode>(Val);
439 }
440 }
441
442 // Emit the linker options if present.
443 if (LinkerOptions) {
444 for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
445 MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
446 SmallVector<std::string, 4> StrOptions;
447
448 // Convert to strings.
449 for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
450 MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
451 StrOptions.push_back(MDOption->getString());
452 }
453
454 Streamer.EmitLinkerOptions(StrOptions);
455 }
456 }
457
458 // The section is mandatory. If we don't have it, then we don't have GC info.
459 if (SectionVal.empty()) return;
460
461 StringRef Segment, Section;
462 unsigned TAA = 0, StubSize = 0;
463 bool TAAParsed;
464 std::string ErrorCode =
465 MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
466 TAA, TAAParsed, StubSize);
467 if (!ErrorCode.empty())
468 // If invalid, report the error with report_fatal_error.
469 report_fatal_error("Invalid section specifier '" + Section + "': " +
470 ErrorCode + ".");
471
472 // Get the section.
473 const MCSectionMachO *S =
474 getContext().getMachOSection(Segment, Section, TAA, StubSize,
475 SectionKind::getDataNoRel());
476 Streamer.SwitchSection(S);
477 Streamer.EmitLabel(getContext().
478 GetOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
479 Streamer.EmitIntValue(VersionVal, 4);
480 Streamer.EmitIntValue(ImageInfoFlags, 4);
481 Streamer.AddBlankLine();
482 }
483
484 const MCSection *TargetLoweringObjectFileMachO::
getExplicitSectionGlobal(const GlobalValue * GV,SectionKind Kind,Mangler * Mang,const TargetMachine & TM) const485 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
486 Mangler *Mang, const TargetMachine &TM) const {
487 // Parse the section specifier and create it if valid.
488 StringRef Segment, Section;
489 unsigned TAA = 0, StubSize = 0;
490 bool TAAParsed;
491 std::string ErrorCode =
492 MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
493 TAA, TAAParsed, StubSize);
494 if (!ErrorCode.empty()) {
495 // If invalid, report the error with report_fatal_error.
496 report_fatal_error("Global variable '" + GV->getName() +
497 "' has an invalid section specifier '" +
498 GV->getSection() + "': " + ErrorCode + ".");
499 }
500
501 // Get the section.
502 const MCSectionMachO *S =
503 getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
504
505 // If TAA wasn't set by ParseSectionSpecifier() above,
506 // use the value returned by getMachOSection() as a default.
507 if (!TAAParsed)
508 TAA = S->getTypeAndAttributes();
509
510 // Okay, now that we got the section, verify that the TAA & StubSize agree.
511 // If the user declared multiple globals with different section flags, we need
512 // to reject it here.
513 if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
514 // If invalid, report the error with report_fatal_error.
515 report_fatal_error("Global variable '" + GV->getName() +
516 "' section type or attributes does not match previous"
517 " section specifier");
518 }
519
520 return S;
521 }
522
523 const MCSection *TargetLoweringObjectFileMachO::
SelectSectionForGlobal(const GlobalValue * GV,SectionKind Kind,Mangler * Mang,const TargetMachine & TM) const524 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
525 Mangler *Mang, const TargetMachine &TM) const {
526
527 // Handle thread local data.
528 if (Kind.isThreadBSS()) return TLSBSSSection;
529 if (Kind.isThreadData()) return TLSDataSection;
530
531 if (Kind.isText())
532 return GV->isWeakForLinker() ? TextCoalSection : TextSection;
533
534 // If this is weak/linkonce, put this in a coalescable section, either in text
535 // or data depending on if it is writable.
536 if (GV->isWeakForLinker()) {
537 if (Kind.isReadOnly())
538 return ConstTextCoalSection;
539 return DataCoalSection;
540 }
541
542 // FIXME: Alignment check should be handled by section classifier.
543 if (Kind.isMergeable1ByteCString() &&
544 TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
545 return CStringSection;
546
547 // Do not put 16-bit arrays in the UString section if they have an
548 // externally visible label, this runs into issues with certain linker
549 // versions.
550 if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
551 TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
552 return UStringSection;
553
554 if (Kind.isMergeableConst()) {
555 if (Kind.isMergeableConst4())
556 return FourByteConstantSection;
557 if (Kind.isMergeableConst8())
558 return EightByteConstantSection;
559 if (Kind.isMergeableConst16() && SixteenByteConstantSection)
560 return SixteenByteConstantSection;
561 }
562
563 // Otherwise, if it is readonly, but not something we can specially optimize,
564 // just drop it in .const.
565 if (Kind.isReadOnly())
566 return ReadOnlySection;
567
568 // If this is marked const, put it into a const section. But if the dynamic
569 // linker needs to write to it, put it in the data segment.
570 if (Kind.isReadOnlyWithRel())
571 return ConstDataSection;
572
573 // Put zero initialized globals with strong external linkage in the
574 // DATA, __common section with the .zerofill directive.
575 if (Kind.isBSSExtern())
576 return DataCommonSection;
577
578 // Put zero initialized globals with local linkage in __DATA,__bss directive
579 // with the .zerofill directive (aka .lcomm).
580 if (Kind.isBSSLocal())
581 return DataBSSSection;
582
583 // Otherwise, just drop the variable in the normal data section.
584 return DataSection;
585 }
586
587 const MCSection *
getSectionForConstant(SectionKind Kind) const588 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
589 // If this constant requires a relocation, we have to put it in the data
590 // segment, not in the text segment.
591 if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
592 return ConstDataSection;
593
594 if (Kind.isMergeableConst4())
595 return FourByteConstantSection;
596 if (Kind.isMergeableConst8())
597 return EightByteConstantSection;
598 if (Kind.isMergeableConst16() && SixteenByteConstantSection)
599 return SixteenByteConstantSection;
600 return ReadOnlySection; // .const
601 }
602
603 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
604 /// not to emit the UsedDirective for some symbols in llvm.used.
605 // FIXME: REMOVE this (rdar://7071300)
606 bool TargetLoweringObjectFileMachO::
shouldEmitUsedDirectiveFor(const GlobalValue * GV,Mangler * Mang) const607 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
608 /// On Darwin, internally linked data beginning with "L" or "l" does not have
609 /// the directive emitted (this occurs in ObjC metadata).
610 if (!GV) return false;
611
612 // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
613 if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
614 // FIXME: ObjC metadata is currently emitted as internal symbols that have
615 // \1L and \0l prefixes on them. Fix them to be Private/LinkerPrivate and
616 // this horrible hack can go away.
617 MCSymbol *Sym = Mang->getSymbol(GV);
618 if (Sym->getName()[0] == 'L' || Sym->getName()[0] == 'l')
619 return false;
620 }
621
622 return true;
623 }
624
625 const MCExpr *TargetLoweringObjectFileMachO::
getTTypeGlobalReference(const GlobalValue * GV,Mangler * Mang,MachineModuleInfo * MMI,unsigned Encoding,MCStreamer & Streamer) const626 getTTypeGlobalReference(const GlobalValue *GV, Mangler *Mang,
627 MachineModuleInfo *MMI, unsigned Encoding,
628 MCStreamer &Streamer) const {
629 // The mach-o version of this method defaults to returning a stub reference.
630
631 if (Encoding & DW_EH_PE_indirect) {
632 MachineModuleInfoMachO &MachOMMI =
633 MMI->getObjFileInfo<MachineModuleInfoMachO>();
634
635 SmallString<128> Name;
636 Mang->getNameWithPrefix(Name, GV, true);
637 Name += "$non_lazy_ptr";
638
639 // Add information about the stub reference to MachOMMI so that the stub
640 // gets emitted by the asmprinter.
641 MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
642 MachineModuleInfoImpl::StubValueTy &StubSym =
643 GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
644 MachOMMI.getGVStubEntry(SSym);
645 if (StubSym.getPointer() == 0) {
646 MCSymbol *Sym = Mang->getSymbol(GV);
647 StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
648 }
649
650 return TargetLoweringObjectFile::
651 getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
652 Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
653 }
654
655 return TargetLoweringObjectFile::
656 getTTypeGlobalReference(GV, Mang, MMI, Encoding, Streamer);
657 }
658
659 MCSymbol *TargetLoweringObjectFileMachO::
getCFIPersonalitySymbol(const GlobalValue * GV,Mangler * Mang,MachineModuleInfo * MMI) const660 getCFIPersonalitySymbol(const GlobalValue *GV, Mangler *Mang,
661 MachineModuleInfo *MMI) const {
662 // The mach-o version of this method defaults to returning a stub reference.
663 MachineModuleInfoMachO &MachOMMI =
664 MMI->getObjFileInfo<MachineModuleInfoMachO>();
665
666 SmallString<128> Name;
667 Mang->getNameWithPrefix(Name, GV, true);
668 Name += "$non_lazy_ptr";
669
670 // Add information about the stub reference to MachOMMI so that the stub
671 // gets emitted by the asmprinter.
672 MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
673 MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
674 if (StubSym.getPointer() == 0) {
675 MCSymbol *Sym = Mang->getSymbol(GV);
676 StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
677 }
678
679 return SSym;
680 }
681
682 //===----------------------------------------------------------------------===//
683 // COFF
684 //===----------------------------------------------------------------------===//
685
686 static unsigned
getCOFFSectionFlags(SectionKind K)687 getCOFFSectionFlags(SectionKind K) {
688 unsigned Flags = 0;
689
690 if (K.isMetadata())
691 Flags |=
692 COFF::IMAGE_SCN_MEM_DISCARDABLE;
693 else if (K.isText())
694 Flags |=
695 COFF::IMAGE_SCN_MEM_EXECUTE |
696 COFF::IMAGE_SCN_MEM_READ |
697 COFF::IMAGE_SCN_CNT_CODE;
698 else if (K.isBSS ())
699 Flags |=
700 COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
701 COFF::IMAGE_SCN_MEM_READ |
702 COFF::IMAGE_SCN_MEM_WRITE;
703 else if (K.isThreadLocal())
704 Flags |=
705 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
706 COFF::IMAGE_SCN_MEM_READ |
707 COFF::IMAGE_SCN_MEM_WRITE;
708 else if (K.isReadOnly())
709 Flags |=
710 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
711 COFF::IMAGE_SCN_MEM_READ;
712 else if (K.isWriteable())
713 Flags |=
714 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
715 COFF::IMAGE_SCN_MEM_READ |
716 COFF::IMAGE_SCN_MEM_WRITE;
717
718 return Flags;
719 }
720
721 const MCSection *TargetLoweringObjectFileCOFF::
getExplicitSectionGlobal(const GlobalValue * GV,SectionKind Kind,Mangler * Mang,const TargetMachine & TM) const722 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
723 Mangler *Mang, const TargetMachine &TM) const {
724 int Selection = 0;
725 unsigned Characteristics = getCOFFSectionFlags(Kind);
726 SmallString<128> Name(GV->getSection().c_str());
727 if (GV->isWeakForLinker()) {
728 Selection = COFF::IMAGE_COMDAT_SELECT_ANY;
729 Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
730 MCSymbol *Sym = Mang->getSymbol(GV);
731 Name.append("$");
732 Name.append(Sym->getName().begin() + 1, Sym->getName().end());
733 }
734 return getContext().getCOFFSection(Name,
735 Characteristics,
736 Selection,
737 Kind);
738 }
739
getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind)740 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
741 if (Kind.isText())
742 return ".text$";
743 if (Kind.isBSS ())
744 return ".bss$";
745 if (Kind.isThreadLocal()) {
746 // 'LLVM' is just an arbitary string to ensure that the section name gets
747 // sorted in between '.tls$AAA' and '.tls$ZZZ' by the linker.
748 return ".tls$LLVM";
749 }
750 if (Kind.isWriteable())
751 return ".data$";
752 return ".rdata$";
753 }
754
755
756 const MCSection *TargetLoweringObjectFileCOFF::
SelectSectionForGlobal(const GlobalValue * GV,SectionKind Kind,Mangler * Mang,const TargetMachine & TM) const757 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
758 Mangler *Mang, const TargetMachine &TM) const {
759
760 // If this global is linkonce/weak and the target handles this by emitting it
761 // into a 'uniqued' section name, create and return the section now.
762 if (GV->isWeakForLinker()) {
763 const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
764 SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
765 MCSymbol *Sym = Mang->getSymbol(GV);
766 Name.append(Sym->getName().begin() + 1, Sym->getName().end());
767
768 unsigned Characteristics = getCOFFSectionFlags(Kind);
769
770 Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
771
772 return getContext().getCOFFSection(Name.str(), Characteristics,
773 COFF::IMAGE_COMDAT_SELECT_ANY, Kind);
774 }
775
776 if (Kind.isText())
777 return getTextSection();
778
779 if (Kind.isThreadLocal())
780 return getTLSDataSection();
781
782 return getDataSection();
783 }
784
785