1 //===-- llvm/Target/TargetLoweringObjectFile.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/Target/TargetLoweringObjectFile.h" 16 #include "llvm/Constants.h" 17 #include "llvm/DerivedTypes.h" 18 #include "llvm/GlobalVariable.h" 19 #include "llvm/MC/MCContext.h" 20 #include "llvm/MC/MCSection.h" 21 #include "llvm/Target/TargetMachine.h" 22 #include "llvm/Target/TargetData.h" 23 #include "llvm/Target/TargetOptions.h" 24 #include "llvm/Support/Mangler.h" 25 #include "llvm/ADT/StringExtras.h" 26 using namespace llvm; 27 28 //===----------------------------------------------------------------------===// 29 // Generic Code 30 //===----------------------------------------------------------------------===// 31 32 TargetLoweringObjectFile::TargetLoweringObjectFile() : Ctx(0) { 33 TextSection = 0; 34 DataSection = 0; 35 BSSSection_ = 0; 36 ReadOnlySection = 0; 37 TLSDataSection = 0; 38 TLSBSSSection = 0; 39 CStringSection_ = 0; 40 } 41 42 TargetLoweringObjectFile::~TargetLoweringObjectFile() { 43 } 44 45 static bool isSuitableForBSS(const GlobalVariable *GV) { 46 Constant *C = GV->getInitializer(); 47 48 // Must have zero initializer. 49 if (!C->isNullValue()) 50 return false; 51 52 // Leave constant zeros in readonly constant sections, so they can be shared. 53 if (GV->isConstant()) 54 return false; 55 56 // If the global has an explicit section specified, don't put it in BSS. 57 if (!GV->getSection().empty()) 58 return false; 59 60 // If -nozero-initialized-in-bss is specified, don't ever use BSS. 61 if (NoZerosInBSS) 62 return false; 63 64 // Otherwise, put it in BSS! 65 return true; 66 } 67 68 static bool isConstantString(const Constant *C) { 69 // First check: is we have constant array of i8 terminated with zero 70 const ConstantArray *CVA = dyn_cast<ConstantArray>(C); 71 // Check, if initializer is a null-terminated string 72 if (CVA && CVA->isCString()) 73 return true; 74 75 // Another possibility: [1 x i8] zeroinitializer 76 if (isa<ConstantAggregateZero>(C)) 77 if (const ArrayType *Ty = dyn_cast<ArrayType>(C->getType())) 78 return (Ty->getElementType() == Type::Int8Ty && 79 Ty->getNumElements() == 1); 80 81 return false; 82 } 83 84 /// SectionKindForGlobal - This is a top-level target-independent classifier for 85 /// a global variable. Given an global variable and information from TM, it 86 /// classifies the global in a variety of ways that make various target 87 /// implementations simpler. The target implementation is free to ignore this 88 /// extra info of course. 89 static SectionKind SectionKindForGlobal(const GlobalValue *GV, 90 const TargetMachine &TM) { 91 Reloc::Model ReloModel = TM.getRelocationModel(); 92 93 // Early exit - functions should be always in text sections. 94 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV); 95 if (GVar == 0) 96 return SectionKind::get(SectionKind::Text); 97 98 99 // Handle thread-local data first. 100 if (GVar->isThreadLocal()) { 101 if (isSuitableForBSS(GVar)) 102 return SectionKind::get(SectionKind::ThreadBSS); 103 return SectionKind::get(SectionKind::ThreadData); 104 } 105 106 // Variable can be easily put to BSS section. 107 if (isSuitableForBSS(GVar)) 108 return SectionKind::get(SectionKind::BSS); 109 110 Constant *C = GVar->getInitializer(); 111 112 // If the global is marked constant, we can put it into a mergable section, 113 // a mergable string section, or general .data if it contains relocations. 114 if (GVar->isConstant()) { 115 // If the initializer for the global contains something that requires a 116 // relocation, then we may have to drop this into a wriable data section 117 // even though it is marked const. 118 switch (C->getRelocationInfo()) { 119 default: llvm_unreachable("unknown relocation info kind"); 120 case Constant::NoRelocation: 121 // If initializer is a null-terminated string, put it in a "cstring" 122 // section if the target has it. 123 if (isConstantString(C)) 124 return SectionKind::get(SectionKind::MergeableCString); 125 126 // Otherwise, just drop it into a mergable constant section. If we have 127 // a section for this size, use it, otherwise use the arbitrary sized 128 // mergable section. 129 switch (TM.getTargetData()->getTypeAllocSize(C->getType())) { 130 case 4: return SectionKind::get(SectionKind::MergeableConst4); 131 case 8: return SectionKind::get(SectionKind::MergeableConst8); 132 case 16: return SectionKind::get(SectionKind::MergeableConst16); 133 default: return SectionKind::get(SectionKind::MergeableConst); 134 } 135 136 case Constant::LocalRelocation: 137 // In static relocation model, the linker will resolve all addresses, so 138 // the relocation entries will actually be constants by the time the app 139 // starts up. However, we can't put this into a mergable section, because 140 // the linker doesn't take relocations into consideration when it tries to 141 // merge entries in the section. 142 if (ReloModel == Reloc::Static) 143 return SectionKind::get(SectionKind::ReadOnly); 144 145 // Otherwise, the dynamic linker needs to fix it up, put it in the 146 // writable data.rel.local section. 147 return SectionKind::get(SectionKind::ReadOnlyWithRelLocal); 148 149 case Constant::GlobalRelocations: 150 // In static relocation model, the linker will resolve all addresses, so 151 // the relocation entries will actually be constants by the time the app 152 // starts up. However, we can't put this into a mergable section, because 153 // the linker doesn't take relocations into consideration when it tries to 154 // merge entries in the section. 155 if (ReloModel == Reloc::Static) 156 return SectionKind::get(SectionKind::ReadOnly); 157 158 // Otherwise, the dynamic linker needs to fix it up, put it in the 159 // writable data.rel section. 160 return SectionKind::get(SectionKind::ReadOnlyWithRel); 161 } 162 } 163 164 // Okay, this isn't a constant. If the initializer for the global is going 165 // to require a runtime relocation by the dynamic linker, put it into a more 166 // specific section to improve startup time of the app. This coalesces these 167 // globals together onto fewer pages, improving the locality of the dynamic 168 // linker. 169 if (ReloModel == Reloc::Static) 170 return SectionKind::get(SectionKind::DataNoRel); 171 172 switch (C->getRelocationInfo()) { 173 default: llvm_unreachable("unknown relocation info kind"); 174 case Constant::NoRelocation: 175 return SectionKind::get(SectionKind::DataNoRel); 176 case Constant::LocalRelocation: 177 return SectionKind::get(SectionKind::DataRelLocal); 178 case Constant::GlobalRelocations: 179 return SectionKind::get(SectionKind::DataRel); 180 } 181 } 182 183 /// SectionForGlobal - This method computes the appropriate section to emit 184 /// the specified global variable or function definition. This should not 185 /// be passed external (or available externally) globals. 186 const MCSection *TargetLoweringObjectFile:: 187 SectionForGlobal(const GlobalValue *GV, Mangler *Mang, 188 const TargetMachine &TM) const { 189 assert(!GV->isDeclaration() && !GV->hasAvailableExternallyLinkage() && 190 "Can only be used for global definitions"); 191 192 SectionKind Kind = SectionKindForGlobal(GV, TM); 193 SectionInfo Info = SectionInfo::get(Kind, GV->isWeakForLinker()); 194 195 // Select section name. 196 if (GV->hasSection()) { 197 // If the target has special section hacks for specifically named globals, 198 // return them now. 199 if (const MCSection *TS = getSpecialCasedSectionGlobals(GV, Mang, Info)) 200 return TS; 201 202 // If the target has magic semantics for certain section names, make sure to 203 // pick up the flags. This allows the user to write things with attribute 204 // section and still get the appropriate section flags printed. 205 Kind = getKindForNamedSection(GV->getSection().c_str(), Kind); 206 207 return getOrCreateSection(GV->getSection().c_str(), false, Kind); 208 } 209 210 211 // Use default section depending on the 'type' of global 212 return SelectSectionForGlobal(GV, Info, Mang, TM); 213 } 214 215 // Lame default implementation. Calculate the section name for global. 216 const MCSection * 217 TargetLoweringObjectFile::SelectSectionForGlobal(const GlobalValue *GV, 218 SectionInfo Info, 219 Mangler *Mang, 220 const TargetMachine &TM) const{ 221 assert(!Info.isThreadLocal() && "Doesn't support TLS"); 222 223 if (Info.isText()) 224 return getTextSection(); 225 226 if (Info.isBSS() && BSSSection_ != 0) 227 return BSSSection_; 228 229 if (Info.isReadOnly() && ReadOnlySection != 0) 230 return ReadOnlySection; 231 232 return getDataSection(); 233 } 234 235 /// getSectionForMergableConstant - Given a mergable constant with the 236 /// specified size and relocation information, return a section that it 237 /// should be placed in. 238 const MCSection * 239 TargetLoweringObjectFile:: 240 getSectionForMergeableConstant(SectionKind Kind) const { 241 if (Kind.isReadOnly() && ReadOnlySection != 0) 242 return ReadOnlySection; 243 244 return DataSection; 245 } 246 247 248 const MCSection *TargetLoweringObjectFile:: 249 getOrCreateSection(const char *Name, bool isDirective, SectionKind Kind) const { 250 if (MCSection *S = Ctx->GetSection(Name)) 251 return S; 252 return MCSection::Create(Name, isDirective, Kind, *Ctx); 253 } 254 255 256 257 //===----------------------------------------------------------------------===// 258 // ELF 259 //===----------------------------------------------------------------------===// 260 261 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx, 262 const TargetMachine &TM) { 263 TargetLoweringObjectFile::Initialize(Ctx, TM); 264 if (!HasCrazyBSS) 265 BSSSection_ = getOrCreateSection("\t.bss", true, 266 SectionKind::get(SectionKind::BSS)); 267 else 268 // PPC/Linux doesn't support the .bss directive, it needs .section .bss. 269 // FIXME: Does .section .bss work everywhere?? 270 // FIXME2: this should just be handle by the section printer. We should get 271 // away from syntactic view of the sections and MCSection should just be a 272 // semantic view. 273 BSSSection_ = getOrCreateSection("\t.bss", false, 274 SectionKind::get(SectionKind::BSS)); 275 276 277 TextSection = getOrCreateSection("\t.text", true, 278 SectionKind::get(SectionKind::Text)); 279 DataSection = getOrCreateSection("\t.data", true, 280 SectionKind::get(SectionKind::DataRel)); 281 ReadOnlySection = 282 getOrCreateSection("\t.rodata", false, 283 SectionKind::get(SectionKind::ReadOnly)); 284 TLSDataSection = 285 getOrCreateSection("\t.tdata", false, 286 SectionKind::get(SectionKind::ThreadData)); 287 CStringSection_ = getOrCreateSection("\t.rodata.str", true, 288 SectionKind::get(SectionKind::MergeableCString)); 289 290 TLSBSSSection = getOrCreateSection("\t.tbss", false, 291 SectionKind::get(SectionKind::ThreadBSS)); 292 293 DataRelSection = getOrCreateSection("\t.data.rel", false, 294 SectionKind::get(SectionKind::DataRel)); 295 DataRelLocalSection = getOrCreateSection("\t.data.rel.local", false, 296 SectionKind::get(SectionKind::DataRelLocal)); 297 DataRelROSection = getOrCreateSection("\t.data.rel.ro", false, 298 SectionKind::get(SectionKind::ReadOnlyWithRel)); 299 DataRelROLocalSection = 300 getOrCreateSection("\t.data.rel.ro.local", false, 301 SectionKind::get(SectionKind::ReadOnlyWithRelLocal)); 302 303 MergeableConst4Section = getOrCreateSection(".rodata.cst4", false, 304 SectionKind::get(SectionKind::MergeableConst4)); 305 MergeableConst8Section = getOrCreateSection(".rodata.cst8", false, 306 SectionKind::get(SectionKind::MergeableConst8)); 307 MergeableConst16Section = getOrCreateSection(".rodata.cst16", false, 308 SectionKind::get(SectionKind::MergeableConst16)); 309 } 310 311 312 SectionKind TargetLoweringObjectFileELF:: 313 getKindForNamedSection(const char *Name, SectionKind K) const { 314 if (Name[0] != '.') return K; 315 316 // Some lame default implementation based on some magic section names. 317 if (strncmp(Name, ".gnu.linkonce.b.", 16) == 0 || 318 strncmp(Name, ".llvm.linkonce.b.", 17) == 0 || 319 strncmp(Name, ".gnu.linkonce.sb.", 17) == 0 || 320 strncmp(Name, ".llvm.linkonce.sb.", 18) == 0) 321 return SectionKind::get(SectionKind::BSS); 322 323 if (strcmp(Name, ".tdata") == 0 || 324 strncmp(Name, ".tdata.", 7) == 0 || 325 strncmp(Name, ".gnu.linkonce.td.", 17) == 0 || 326 strncmp(Name, ".llvm.linkonce.td.", 18) == 0) 327 return SectionKind::get(SectionKind::ThreadData); 328 329 if (strcmp(Name, ".tbss") == 0 || 330 strncmp(Name, ".tbss.", 6) == 0 || 331 strncmp(Name, ".gnu.linkonce.tb.", 17) == 0 || 332 strncmp(Name, ".llvm.linkonce.tb.", 18) == 0) 333 return SectionKind::get(SectionKind::ThreadBSS); 334 335 return K; 336 } 337 338 void TargetLoweringObjectFileELF:: 339 getSectionFlagsAsString(SectionKind Kind, SmallVectorImpl<char> &Str) const { 340 Str.push_back(','); 341 Str.push_back('"'); 342 343 if (!Kind.isMetadata()) 344 Str.push_back('a'); 345 if (Kind.isText()) 346 Str.push_back('x'); 347 if (Kind.isWriteable()) 348 Str.push_back('w'); 349 if (Kind.isMergeableCString() || 350 Kind.isMergeableConst4() || 351 Kind.isMergeableConst8() || 352 Kind.isMergeableConst16()) 353 Str.push_back('M'); 354 if (Kind.isMergeableCString()) 355 Str.push_back('S'); 356 if (Kind.isThreadLocal()) 357 Str.push_back('T'); 358 359 Str.push_back('"'); 360 Str.push_back(','); 361 362 // If comment string is '@', e.g. as on ARM - use '%' instead 363 if (AtIsCommentChar) 364 Str.push_back('%'); 365 else 366 Str.push_back('@'); 367 368 const char *KindStr; 369 if (Kind.isBSS() || Kind.isThreadBSS()) 370 KindStr = "nobits"; 371 else 372 KindStr = "progbits"; 373 374 Str.append(KindStr, KindStr+strlen(KindStr)); 375 376 if (Kind.isMergeableCString()) { 377 // TODO: Eventually handle multiple byte character strings. For now, all 378 // mergable C strings are single byte. 379 Str.push_back(','); 380 Str.push_back('1'); 381 } else if (Kind.isMergeableConst4()) { 382 Str.push_back(','); 383 Str.push_back('4'); 384 } else if (Kind.isMergeableConst8()) { 385 Str.push_back(','); 386 Str.push_back('8'); 387 } else if (Kind.isMergeableConst16()) { 388 Str.push_back(','); 389 Str.push_back('1'); 390 Str.push_back('6'); 391 } 392 } 393 394 395 static const char *getSectionPrefixForUniqueGlobal(SectionKind Kind) { 396 if (Kind.isText()) return ".gnu.linkonce.t."; 397 if (Kind.isReadOnly()) return ".gnu.linkonce.r."; 398 399 if (Kind.isThreadData()) return ".gnu.linkonce.td."; 400 if (Kind.isThreadBSS()) return ".gnu.linkonce.tb."; 401 402 if (Kind.isBSS()) return ".gnu.linkonce.b."; 403 if (Kind.isDataNoRel()) return ".gnu.linkonce.d."; 404 if (Kind.isDataRelLocal()) return ".gnu.linkonce.d.rel.local."; 405 if (Kind.isDataRel()) return ".gnu.linkonce.d.rel."; 406 if (Kind.isReadOnlyWithRelLocal()) return ".gnu.linkonce.d.rel.ro.local."; 407 408 assert(Kind.isReadOnlyWithRel() && "Unknown section kind"); 409 return ".gnu.linkonce.d.rel.ro."; 410 } 411 412 const MCSection *TargetLoweringObjectFileELF:: 413 SelectSectionForGlobal(const GlobalValue *GV, SectionInfo Info, 414 Mangler *Mang, const TargetMachine &TM) const { 415 416 // If this global is linkonce/weak and the target handles this by emitting it 417 // into a 'uniqued' section name, create and return the section now. 418 if (GV->isWeakForLinker()) { 419 const char *Prefix = getSectionPrefixForUniqueGlobal(Info); 420 std::string Name = Mang->makeNameProper(GV->getNameStr()); 421 return getOrCreateSection((Prefix+Name).c_str(), false, Info); 422 } 423 424 if (Info.isText()) return TextSection; 425 426 if (Info.isMergeableCString()) { 427 assert(CStringSection_ && "Should have string section prefix"); 428 429 // We also need alignment here. 430 // FIXME: this is getting the alignment of the character, not the 431 // alignment of the global! 432 unsigned Align = 433 TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)); 434 435 std::string Name = CStringSection_->getName() + "1." + utostr(Align); 436 return getOrCreateSection(Name.c_str(), false, 437 SectionKind::get(SectionKind::MergeableCString)); 438 } 439 440 if (Info.isMergeableConst()) { 441 if (Info.isMergeableConst4()) 442 return MergeableConst4Section; 443 if (Info.isMergeableConst8()) 444 return MergeableConst8Section; 445 if (Info.isMergeableConst16()) 446 return MergeableConst16Section; 447 return ReadOnlySection; // .const 448 } 449 450 if (Info.isReadOnly()) return ReadOnlySection; 451 452 if (Info.isThreadData()) return TLSDataSection; 453 if (Info.isThreadBSS()) return TLSBSSSection; 454 455 if (Info.isBSS()) return BSSSection_; 456 457 if (Info.isDataNoRel()) return DataSection; 458 if (Info.isDataRelLocal()) return DataRelLocalSection; 459 if (Info.isDataRel()) return DataRelSection; 460 if (Info.isReadOnlyWithRelLocal()) return DataRelROLocalSection; 461 462 assert(Info.isReadOnlyWithRel() && "Unknown section kind"); 463 return DataRelROSection; 464 } 465 466 /// getSectionForMergeableConstant - Given a mergeable constant with the 467 /// specified size and relocation information, return a section that it 468 /// should be placed in. 469 const MCSection *TargetLoweringObjectFileELF:: 470 getSectionForMergeableConstant(SectionKind Kind) const { 471 if (Kind.isMergeableConst4()) 472 return MergeableConst4Section; 473 if (Kind.isMergeableConst8()) 474 return MergeableConst8Section; 475 if (Kind.isMergeableConst16()) 476 return MergeableConst16Section; 477 if (Kind.isReadOnly()) 478 return ReadOnlySection; 479 480 if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection; 481 assert(Kind.isReadOnlyWithRel() && "Unknown section kind"); 482 return DataRelROSection; 483 } 484 485 //===----------------------------------------------------------------------===// 486 // MachO 487 //===----------------------------------------------------------------------===// 488 489 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx, 490 const TargetMachine &TM) { 491 TargetLoweringObjectFile::Initialize(Ctx, TM); 492 TextSection = getOrCreateSection("\t.text", true, 493 SectionKind::get(SectionKind::Text)); 494 DataSection = getOrCreateSection("\t.data", true, 495 SectionKind::get(SectionKind::DataRel)); 496 497 CStringSection_ = getOrCreateSection("\t.cstring", true, 498 SectionKind::get(SectionKind::MergeableCString)); 499 FourByteConstantSection = getOrCreateSection("\t.literal4\n", true, 500 SectionKind::get(SectionKind::MergeableConst4)); 501 EightByteConstantSection = getOrCreateSection("\t.literal8\n", true, 502 SectionKind::get(SectionKind::MergeableConst8)); 503 504 // ld_classic doesn't support .literal16 in 32-bit mode, and ld64 falls back 505 // to using it in -static mode. 506 if (TM.getRelocationModel() != Reloc::Static && 507 TM.getTargetData()->getPointerSize() == 32) 508 SixteenByteConstantSection = 509 getOrCreateSection("\t.literal16\n", true, 510 SectionKind::get(SectionKind::MergeableConst16)); 511 else 512 SixteenByteConstantSection = 0; 513 514 ReadOnlySection = getOrCreateSection("\t.const", true, 515 SectionKind::get(SectionKind::ReadOnly)); 516 517 TextCoalSection = 518 getOrCreateSection("\t__TEXT,__textcoal_nt,coalesced,pure_instructions", 519 false, SectionKind::get(SectionKind::Text)); 520 ConstTextCoalSection = getOrCreateSection("\t__TEXT,__const_coal,coalesced", 521 false, 522 SectionKind::get(SectionKind::Text)); 523 ConstDataCoalSection = getOrCreateSection("\t__DATA,__const_coal,coalesced", 524 false, 525 SectionKind::get(SectionKind::Text)); 526 ConstDataSection = getOrCreateSection("\t.const_data", true, 527 SectionKind::get(SectionKind::ReadOnlyWithRel)); 528 DataCoalSection = getOrCreateSection("\t__DATA,__datacoal_nt,coalesced", 529 false, 530 SectionKind::get(SectionKind::DataRel)); 531 } 532 533 const MCSection *TargetLoweringObjectFileMachO:: 534 SelectSectionForGlobal(const GlobalValue *GV, SectionInfo Info, 535 Mangler *Mang, const TargetMachine &TM) const { 536 assert(!Info.isThreadLocal() && "Darwin doesn't support TLS"); 537 538 if (Info.isText()) 539 return GV->isWeakForLinker() ? TextCoalSection : TextSection; 540 541 // If this is weak/linkonce, put this in a coalescable section, either in text 542 // or data depending on if it is writable. 543 if (GV->isWeakForLinker()) { 544 if (Info.isReadOnly()) 545 return ConstTextCoalSection; 546 return DataCoalSection; 547 } 548 549 // FIXME: Alignment check should be handled by section classifier. 550 if (Info.isMergeableCString()) { 551 Constant *C = cast<GlobalVariable>(GV)->getInitializer(); 552 const Type *Ty = cast<ArrayType>(C->getType())->getElementType(); 553 const TargetData &TD = *TM.getTargetData(); 554 unsigned Size = TD.getTypeAllocSize(Ty); 555 if (Size) { 556 unsigned Align = TD.getPreferredAlignment(cast<GlobalVariable>(GV)); 557 if (Align <= 32) 558 return CStringSection_; 559 } 560 561 return ReadOnlySection; 562 } 563 564 if (Info.isMergeableConst()) { 565 if (Info.isMergeableConst4()) 566 return FourByteConstantSection; 567 if (Info.isMergeableConst8()) 568 return EightByteConstantSection; 569 if (Info.isMergeableConst16() && SixteenByteConstantSection) 570 return SixteenByteConstantSection; 571 return ReadOnlySection; // .const 572 } 573 574 // FIXME: ROData -> const in -static mode that is relocatable but they happen 575 // by the static linker. Why not mergeable? 576 if (Info.isReadOnly()) 577 return ReadOnlySection; 578 579 // If this is marked const, put it into a const section. But if the dynamic 580 // linker needs to write to it, put it in the data segment. 581 if (Info.isReadOnlyWithRel()) 582 return ConstDataSection; 583 584 // Otherwise, just drop the variable in the normal data section. 585 return DataSection; 586 } 587 588 const MCSection * 589 TargetLoweringObjectFileMachO:: 590 getSectionForMergeableConstant(SectionKind Kind) const { 591 // If this constant requires a relocation, we have to put it in the data 592 // segment, not in the text segment. 593 if (Kind.isDataRel()) 594 return ConstDataSection; 595 596 if (Kind.isMergeableConst4()) 597 return FourByteConstantSection; 598 if (Kind.isMergeableConst8()) 599 return EightByteConstantSection; 600 if (Kind.isMergeableConst16() && SixteenByteConstantSection) 601 return SixteenByteConstantSection; 602 return ReadOnlySection; // .const 603 } 604 605 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide 606 /// not to emit the UsedDirective for some symbols in llvm.used. 607 // FIXME: REMOVE this (rdar://7071300) 608 bool TargetLoweringObjectFileMachO:: 609 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const { 610 /// On Darwin, internally linked data beginning with "L" or "l" does not have 611 /// the directive emitted (this occurs in ObjC metadata). 612 if (!GV) return false; 613 614 // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix. 615 if (GV->hasLocalLinkage() && !isa<Function>(GV)) { 616 // FIXME: ObjC metadata is currently emitted as internal symbols that have 617 // \1L and \0l prefixes on them. Fix them to be Private/LinkerPrivate and 618 // this horrible hack can go away. 619 const std::string &Name = Mang->getMangledName(GV); 620 if (Name[0] == 'L' || Name[0] == 'l') 621 return false; 622 } 623 624 return true; 625 } 626 627 628 //===----------------------------------------------------------------------===// 629 // COFF 630 //===----------------------------------------------------------------------===// 631 632 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx, 633 const TargetMachine &TM) { 634 TargetLoweringObjectFile::Initialize(Ctx, TM); 635 TextSection = getOrCreateSection("\t.text", true, 636 SectionKind::get(SectionKind::Text)); 637 DataSection = getOrCreateSection("\t.data", true, 638 SectionKind::get(SectionKind::DataRel)); 639 } 640 641 void TargetLoweringObjectFileCOFF:: 642 getSectionFlagsAsString(SectionKind Kind, SmallVectorImpl<char> &Str) const { 643 // FIXME: Inefficient. 644 std::string Res = ",\""; 645 if (Kind.isText()) 646 Res += 'x'; 647 if (Kind.isWriteable()) 648 Res += 'w'; 649 Res += "\""; 650 651 Str.append(Res.begin(), Res.end()); 652 } 653 654 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) { 655 if (Kind.isText()) 656 return ".text$linkonce"; 657 if (Kind.isWriteable()) 658 return ".data$linkonce"; 659 return ".rdata$linkonce"; 660 } 661 662 663 const MCSection *TargetLoweringObjectFileCOFF:: 664 SelectSectionForGlobal(const GlobalValue *GV, SectionInfo Info, 665 Mangler *Mang, const TargetMachine &TM) const { 666 assert(!Info.isThreadLocal() && "Doesn't support TLS"); 667 668 // If this global is linkonce/weak and the target handles this by emitting it 669 // into a 'uniqued' section name, create and return the section now. 670 if (GV->isWeakForLinker()) { 671 const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Info); 672 std::string Name = Mang->makeNameProper(GV->getNameStr()); 673 return getOrCreateSection((Prefix+Name).c_str(), false, Info); 674 } 675 676 if (Info.isText()) 677 return getTextSection(); 678 679 if (Info.isBSS() && BSSSection_ != 0) 680 return BSSSection_; 681 682 if (Info.isReadOnly() && ReadOnlySection != 0) 683 return ReadOnlySection; 684 685 return getDataSection(); 686 } 687 688