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 StaticCtorSection = 0; 38 StaticDtorSection = 0; 39 LSDASection = 0; 40 EHFrameSection = 0; 41 42 DwarfAbbrevSection = 0; 43 DwarfInfoSection = 0; 44 DwarfLineSection = 0; 45 DwarfFrameSection = 0; 46 DwarfPubNamesSection = 0; 47 DwarfPubTypesSection = 0; 48 DwarfDebugInlineSection = 0; 49 DwarfStrSection = 0; 50 DwarfLocSection = 0; 51 DwarfARangesSection = 0; 52 DwarfRangesSection = 0; 53 DwarfMacroInfoSection = 0; 54 } 55 56 TargetLoweringObjectFile::~TargetLoweringObjectFile() { 57 } 58 59 static bool isSuitableForBSS(const GlobalVariable *GV) { 60 Constant *C = GV->getInitializer(); 61 62 // Must have zero initializer. 63 if (!C->isNullValue()) 64 return false; 65 66 // Leave constant zeros in readonly constant sections, so they can be shared. 67 if (GV->isConstant()) 68 return false; 69 70 // If the global has an explicit section specified, don't put it in BSS. 71 if (!GV->getSection().empty()) 72 return false; 73 74 // If -nozero-initialized-in-bss is specified, don't ever use BSS. 75 if (NoZerosInBSS) 76 return false; 77 78 // Otherwise, put it in BSS! 79 return true; 80 } 81 82 /// IsNullTerminatedString - Return true if the specified constant (which is 83 /// known to have a type that is an array of 1/2/4 byte elements) ends with a 84 /// nul value and contains no other nuls in it. 85 static bool IsNullTerminatedString(const Constant *C) { 86 const ArrayType *ATy = cast<ArrayType>(C->getType()); 87 88 // First check: is we have constant array of i8 terminated with zero 89 if (const ConstantArray *CVA = dyn_cast<ConstantArray>(C)) { 90 if (ATy->getNumElements() == 0) return false; 91 92 ConstantInt *Null = 93 dyn_cast<ConstantInt>(CVA->getOperand(ATy->getNumElements()-1)); 94 if (Null == 0 || Null->getZExtValue() != 0) 95 return false; // Not null terminated. 96 97 // Verify that the null doesn't occur anywhere else in the string. 98 for (unsigned i = 0, e = ATy->getNumElements()-1; i != e; ++i) 99 // Reject constantexpr elements etc. 100 if (!isa<ConstantInt>(CVA->getOperand(i)) || 101 CVA->getOperand(i) == Null) 102 return false; 103 return true; 104 } 105 106 // Another possibility: [1 x i8] zeroinitializer 107 if (isa<ConstantAggregateZero>(C)) 108 return ATy->getNumElements() == 1; 109 110 return false; 111 } 112 113 /// getKindForGlobal - This is a top-level target-independent classifier for 114 /// a global variable. Given an global variable and information from TM, it 115 /// classifies the global in a variety of ways that make various target 116 /// implementations simpler. The target implementation is free to ignore this 117 /// extra info of course. 118 SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalValue *GV, 119 const TargetMachine &TM){ 120 assert(!GV->isDeclaration() && !GV->hasAvailableExternallyLinkage() && 121 "Can only be used for global definitions"); 122 123 Reloc::Model ReloModel = TM.getRelocationModel(); 124 125 // Early exit - functions should be always in text sections. 126 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV); 127 if (GVar == 0) 128 return SectionKind::getText(); 129 130 131 // Handle thread-local data first. 132 if (GVar->isThreadLocal()) { 133 if (isSuitableForBSS(GVar)) 134 return SectionKind::getThreadBSS(); 135 return SectionKind::getThreadData(); 136 } 137 138 // Variable can be easily put to BSS section. 139 if (isSuitableForBSS(GVar)) 140 return SectionKind::getBSS(); 141 142 Constant *C = GVar->getInitializer(); 143 144 // If the global is marked constant, we can put it into a mergable section, 145 // a mergable string section, or general .data if it contains relocations. 146 if (GVar->isConstant()) { 147 // If the initializer for the global contains something that requires a 148 // relocation, then we may have to drop this into a wriable data section 149 // even though it is marked const. 150 switch (C->getRelocationInfo()) { 151 default: llvm_unreachable("unknown relocation info kind"); 152 case Constant::NoRelocation: 153 // If initializer is a null-terminated string, put it in a "cstring" 154 // section of the right width. 155 if (const ArrayType *ATy = dyn_cast<ArrayType>(C->getType())) { 156 if (const IntegerType *ITy = 157 dyn_cast<IntegerType>(ATy->getElementType())) { 158 if ((ITy->getBitWidth() == 8 || ITy->getBitWidth() == 16 || 159 ITy->getBitWidth() == 32) && 160 IsNullTerminatedString(C)) { 161 if (ITy->getBitWidth() == 8) 162 return SectionKind::getMergeable1ByteCString(); 163 if (ITy->getBitWidth() == 16) 164 return SectionKind::getMergeable2ByteCString(); 165 166 assert(ITy->getBitWidth() == 32 && "Unknown width"); 167 return SectionKind::getMergeable4ByteCString(); 168 } 169 } 170 } 171 172 // Otherwise, just drop it into a mergable constant section. If we have 173 // a section for this size, use it, otherwise use the arbitrary sized 174 // mergable section. 175 switch (TM.getTargetData()->getTypeAllocSize(C->getType())) { 176 case 4: return SectionKind::getMergeableConst4(); 177 case 8: return SectionKind::getMergeableConst8(); 178 case 16: return SectionKind::getMergeableConst16(); 179 default: return SectionKind::getMergeableConst(); 180 } 181 182 case Constant::LocalRelocation: 183 // In static relocation model, the linker will resolve all addresses, so 184 // the relocation entries will actually be constants by the time the app 185 // starts up. However, we can't put this into a mergable section, because 186 // the linker doesn't take relocations into consideration when it tries to 187 // merge entries in the section. 188 if (ReloModel == Reloc::Static) 189 return SectionKind::getReadOnly(); 190 191 // Otherwise, the dynamic linker needs to fix it up, put it in the 192 // writable data.rel.local section. 193 return SectionKind::getReadOnlyWithRelLocal(); 194 195 case Constant::GlobalRelocations: 196 // In static relocation model, the linker will resolve all addresses, so 197 // the relocation entries will actually be constants by the time the app 198 // starts up. However, we can't put this into a mergable section, because 199 // the linker doesn't take relocations into consideration when it tries to 200 // merge entries in the section. 201 if (ReloModel == Reloc::Static) 202 return SectionKind::getReadOnly(); 203 204 // Otherwise, the dynamic linker needs to fix it up, put it in the 205 // writable data.rel section. 206 return SectionKind::getReadOnlyWithRel(); 207 } 208 } 209 210 // Okay, this isn't a constant. If the initializer for the global is going 211 // to require a runtime relocation by the dynamic linker, put it into a more 212 // specific section to improve startup time of the app. This coalesces these 213 // globals together onto fewer pages, improving the locality of the dynamic 214 // linker. 215 if (ReloModel == Reloc::Static) 216 return SectionKind::getDataNoRel(); 217 218 switch (C->getRelocationInfo()) { 219 default: llvm_unreachable("unknown relocation info kind"); 220 case Constant::NoRelocation: 221 return SectionKind::getDataNoRel(); 222 case Constant::LocalRelocation: 223 return SectionKind::getDataRelLocal(); 224 case Constant::GlobalRelocations: 225 return SectionKind::getDataRel(); 226 } 227 } 228 229 /// SectionForGlobal - This method computes the appropriate section to emit 230 /// the specified global variable or function definition. This should not 231 /// be passed external (or available externally) globals. 232 const MCSection *TargetLoweringObjectFile:: 233 SectionForGlobal(const GlobalValue *GV, SectionKind Kind, Mangler *Mang, 234 const TargetMachine &TM) const { 235 // Select section name. 236 if (GV->hasSection()) 237 return getExplicitSectionGlobal(GV, Kind, Mang, TM); 238 239 240 // Use default section depending on the 'type' of global 241 return SelectSectionForGlobal(GV, Kind, Mang, TM); 242 } 243 244 245 // Lame default implementation. Calculate the section name for global. 246 const MCSection * 247 TargetLoweringObjectFile::SelectSectionForGlobal(const GlobalValue *GV, 248 SectionKind Kind, 249 Mangler *Mang, 250 const TargetMachine &TM) const{ 251 assert(!Kind.isThreadLocal() && "Doesn't support TLS"); 252 253 if (Kind.isText()) 254 return getTextSection(); 255 256 if (Kind.isBSS() && BSSSection != 0) 257 return BSSSection; 258 259 if (Kind.isReadOnly() && ReadOnlySection != 0) 260 return ReadOnlySection; 261 262 return getDataSection(); 263 } 264 265 /// getSectionForConstant - Given a mergable constant with the 266 /// specified size and relocation information, return a section that it 267 /// should be placed in. 268 const MCSection * 269 TargetLoweringObjectFile::getSectionForConstant(SectionKind Kind) const { 270 if (Kind.isReadOnly() && ReadOnlySection != 0) 271 return ReadOnlySection; 272 273 return DataSection; 274 } 275 276 277 const MCSection *TargetLoweringObjectFile:: 278 getOrCreateSection(const char *Name, bool isDirective, SectionKind Kind) const { 279 if (MCSection *S = Ctx->GetSection(Name)) 280 return S; 281 return MCSection::Create(Name, isDirective, Kind, *Ctx); 282 } 283 284 285 286 //===----------------------------------------------------------------------===// 287 // ELF 288 //===----------------------------------------------------------------------===// 289 290 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx, 291 const TargetMachine &TM) { 292 TargetLoweringObjectFile::Initialize(Ctx, TM); 293 if (!HasCrazyBSS) 294 BSSSection = getOrCreateSection("\t.bss", true, SectionKind::getBSS()); 295 else 296 // PPC/Linux doesn't support the .bss directive, it needs .section .bss. 297 // FIXME: Does .section .bss work everywhere?? 298 // FIXME2: this should just be handle by the section printer. We should get 299 // away from syntactic view of the sections and MCSection should just be a 300 // semantic view. 301 BSSSection = getOrCreateSection("\t.bss", false, SectionKind::getBSS()); 302 303 304 TextSection = getOrCreateSection("\t.text", true, SectionKind::getText()); 305 DataSection = getOrCreateSection("\t.data", true, SectionKind::getDataRel()); 306 ReadOnlySection = 307 getOrCreateSection("\t.rodata", false, SectionKind::getReadOnly()); 308 TLSDataSection = 309 getOrCreateSection("\t.tdata", false, SectionKind::getThreadData()); 310 311 TLSBSSSection = getOrCreateSection("\t.tbss", false, 312 SectionKind::getThreadBSS()); 313 314 DataRelSection = getOrCreateSection("\t.data.rel", false, 315 SectionKind::getDataRel()); 316 DataRelLocalSection = getOrCreateSection("\t.data.rel.local", false, 317 SectionKind::getDataRelLocal()); 318 DataRelROSection = getOrCreateSection("\t.data.rel.ro", false, 319 SectionKind::getReadOnlyWithRel()); 320 DataRelROLocalSection = 321 getOrCreateSection("\t.data.rel.ro.local", false, 322 SectionKind::getReadOnlyWithRelLocal()); 323 324 MergeableConst4Section = getOrCreateSection(".rodata.cst4", false, 325 SectionKind::getMergeableConst4()); 326 MergeableConst8Section = getOrCreateSection(".rodata.cst8", false, 327 SectionKind::getMergeableConst8()); 328 MergeableConst16Section = getOrCreateSection(".rodata.cst16", false, 329 SectionKind::getMergeableConst16()); 330 331 StaticCtorSection = 332 getOrCreateSection(".ctors", false, SectionKind::getDataRel()); 333 StaticDtorSection = 334 getOrCreateSection(".dtors", false, SectionKind::getDataRel()); 335 336 // Exception Handling Sections. 337 338 // FIXME: We're emitting LSDA info into a readonly section on ELF, even though 339 // it contains relocatable pointers. In PIC mode, this is probably a big 340 // runtime hit for C++ apps. Either the contents of the LSDA need to be 341 // adjusted or this should be a data section. 342 LSDASection = 343 getOrCreateSection(".gcc_except_table", false, SectionKind::getReadOnly()); 344 EHFrameSection = 345 getOrCreateSection(".eh_frame", false, SectionKind::getDataRel()); 346 347 // Debug Info Sections. 348 DwarfAbbrevSection = 349 getOrCreateSection(".debug_abbrev", false, SectionKind::getMetadata()); 350 DwarfInfoSection = 351 getOrCreateSection(".debug_info", false, SectionKind::getMetadata()); 352 DwarfLineSection = 353 getOrCreateSection(".debug_line", false, SectionKind::getMetadata()); 354 DwarfFrameSection = 355 getOrCreateSection(".debug_frame", false, SectionKind::getMetadata()); 356 DwarfPubNamesSection = 357 getOrCreateSection(".debug_pubnames", false, SectionKind::getMetadata()); 358 DwarfPubTypesSection = 359 getOrCreateSection(".debug_pubtypes", false, SectionKind::getMetadata()); 360 DwarfStrSection = 361 getOrCreateSection(".debug_str", false, SectionKind::getMetadata()); 362 DwarfLocSection = 363 getOrCreateSection(".debug_loc", false, SectionKind::getMetadata()); 364 DwarfARangesSection = 365 getOrCreateSection(".debug_aranges", false, SectionKind::getMetadata()); 366 DwarfRangesSection = 367 getOrCreateSection(".debug_ranges", false, SectionKind::getMetadata()); 368 DwarfMacroInfoSection = 369 getOrCreateSection(".debug_macinfo", false, SectionKind::getMetadata()); 370 } 371 372 373 static SectionKind 374 getELFKindForNamedSection(const char *Name, SectionKind K) { 375 if (Name[0] != '.') return K; 376 377 // Some lame default implementation based on some magic section names. 378 if (strncmp(Name, ".gnu.linkonce.b.", 16) == 0 || 379 strncmp(Name, ".llvm.linkonce.b.", 17) == 0 || 380 strncmp(Name, ".gnu.linkonce.sb.", 17) == 0 || 381 strncmp(Name, ".llvm.linkonce.sb.", 18) == 0) 382 return SectionKind::getBSS(); 383 384 if (strcmp(Name, ".tdata") == 0 || 385 strncmp(Name, ".tdata.", 7) == 0 || 386 strncmp(Name, ".gnu.linkonce.td.", 17) == 0 || 387 strncmp(Name, ".llvm.linkonce.td.", 18) == 0) 388 return SectionKind::getThreadData(); 389 390 if (strcmp(Name, ".tbss") == 0 || 391 strncmp(Name, ".tbss.", 6) == 0 || 392 strncmp(Name, ".gnu.linkonce.tb.", 17) == 0 || 393 strncmp(Name, ".llvm.linkonce.tb.", 18) == 0) 394 return SectionKind::getThreadBSS(); 395 396 return K; 397 } 398 399 const MCSection *TargetLoweringObjectFileELF:: 400 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind, 401 Mangler *Mang, const TargetMachine &TM) const { 402 // Infer section flags from the section name if we can. 403 Kind = getELFKindForNamedSection(GV->getSection().c_str(), Kind); 404 405 return getOrCreateSection(GV->getSection().c_str(), false, Kind); 406 } 407 408 409 410 void TargetLoweringObjectFileELF:: 411 getSectionFlagsAsString(SectionKind Kind, SmallVectorImpl<char> &Str) const { 412 Str.push_back(','); 413 Str.push_back('"'); 414 415 if (!Kind.isMetadata()) 416 Str.push_back('a'); 417 if (Kind.isText()) 418 Str.push_back('x'); 419 if (Kind.isWriteable()) 420 Str.push_back('w'); 421 if (Kind.isMergeable1ByteCString() || 422 Kind.isMergeable2ByteCString() || 423 Kind.isMergeable4ByteCString() || 424 Kind.isMergeableConst4() || 425 Kind.isMergeableConst8() || 426 Kind.isMergeableConst16()) 427 Str.push_back('M'); 428 if (Kind.isMergeable1ByteCString() || 429 Kind.isMergeable2ByteCString() || 430 Kind.isMergeable4ByteCString()) 431 Str.push_back('S'); 432 if (Kind.isThreadLocal()) 433 Str.push_back('T'); 434 435 Str.push_back('"'); 436 Str.push_back(','); 437 438 // If comment string is '@', e.g. as on ARM - use '%' instead 439 if (AtIsCommentChar) 440 Str.push_back('%'); 441 else 442 Str.push_back('@'); 443 444 const char *KindStr; 445 if (Kind.isBSS() || Kind.isThreadBSS()) 446 KindStr = "nobits"; 447 else 448 KindStr = "progbits"; 449 450 Str.append(KindStr, KindStr+strlen(KindStr)); 451 452 if (Kind.isMergeable1ByteCString()) { 453 Str.push_back(','); 454 Str.push_back('1'); 455 } else if (Kind.isMergeable2ByteCString()) { 456 Str.push_back(','); 457 Str.push_back('2'); 458 } else if (Kind.isMergeable4ByteCString()) { 459 Str.push_back(','); 460 Str.push_back('4'); 461 } else if (Kind.isMergeableConst4()) { 462 Str.push_back(','); 463 Str.push_back('4'); 464 } else if (Kind.isMergeableConst8()) { 465 Str.push_back(','); 466 Str.push_back('8'); 467 } else if (Kind.isMergeableConst16()) { 468 Str.push_back(','); 469 Str.push_back('1'); 470 Str.push_back('6'); 471 } 472 } 473 474 475 static const char *getSectionPrefixForUniqueGlobal(SectionKind Kind) { 476 if (Kind.isText()) return ".gnu.linkonce.t."; 477 if (Kind.isReadOnly()) return ".gnu.linkonce.r."; 478 479 if (Kind.isThreadData()) return ".gnu.linkonce.td."; 480 if (Kind.isThreadBSS()) return ".gnu.linkonce.tb."; 481 482 if (Kind.isBSS()) return ".gnu.linkonce.b."; 483 if (Kind.isDataNoRel()) return ".gnu.linkonce.d."; 484 if (Kind.isDataRelLocal()) return ".gnu.linkonce.d.rel.local."; 485 if (Kind.isDataRel()) return ".gnu.linkonce.d.rel."; 486 if (Kind.isReadOnlyWithRelLocal()) return ".gnu.linkonce.d.rel.ro.local."; 487 488 assert(Kind.isReadOnlyWithRel() && "Unknown section kind"); 489 return ".gnu.linkonce.d.rel.ro."; 490 } 491 492 const MCSection *TargetLoweringObjectFileELF:: 493 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind, 494 Mangler *Mang, const TargetMachine &TM) const { 495 496 // If this global is linkonce/weak and the target handles this by emitting it 497 // into a 'uniqued' section name, create and return the section now. 498 if (GV->isWeakForLinker()) { 499 const char *Prefix = getSectionPrefixForUniqueGlobal(Kind); 500 std::string Name = Mang->makeNameProper(GV->getNameStr()); 501 return getOrCreateSection((Prefix+Name).c_str(), false, Kind); 502 } 503 504 if (Kind.isText()) return TextSection; 505 506 if (Kind.isMergeable1ByteCString() || 507 Kind.isMergeable2ByteCString() || 508 Kind.isMergeable4ByteCString()) { 509 510 // We also need alignment here. 511 // FIXME: this is getting the alignment of the character, not the 512 // alignment of the global! 513 unsigned Align = 514 TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)); 515 516 const char *SizeSpec = ".rodata.str1."; 517 if (Kind.isMergeable2ByteCString()) 518 SizeSpec = ".rodata.str2."; 519 else if (Kind.isMergeable4ByteCString()) 520 SizeSpec = ".rodata.str4."; 521 else 522 assert(Kind.isMergeable1ByteCString() && "unknown string width"); 523 524 525 std::string Name = SizeSpec + utostr(Align); 526 return getOrCreateSection(Name.c_str(), false, Kind); 527 } 528 529 if (Kind.isMergeableConst()) { 530 if (Kind.isMergeableConst4()) 531 return MergeableConst4Section; 532 if (Kind.isMergeableConst8()) 533 return MergeableConst8Section; 534 if (Kind.isMergeableConst16()) 535 return MergeableConst16Section; 536 return ReadOnlySection; // .const 537 } 538 539 if (Kind.isReadOnly()) return ReadOnlySection; 540 541 if (Kind.isThreadData()) return TLSDataSection; 542 if (Kind.isThreadBSS()) return TLSBSSSection; 543 544 if (Kind.isBSS()) return BSSSection; 545 546 if (Kind.isDataNoRel()) return DataSection; 547 if (Kind.isDataRelLocal()) return DataRelLocalSection; 548 if (Kind.isDataRel()) return DataRelSection; 549 if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection; 550 551 assert(Kind.isReadOnlyWithRel() && "Unknown section kind"); 552 return DataRelROSection; 553 } 554 555 /// getSectionForConstant - Given a mergeable constant with the 556 /// specified size and relocation information, return a section that it 557 /// should be placed in. 558 const MCSection *TargetLoweringObjectFileELF:: 559 getSectionForConstant(SectionKind Kind) const { 560 if (Kind.isMergeableConst4()) 561 return MergeableConst4Section; 562 if (Kind.isMergeableConst8()) 563 return MergeableConst8Section; 564 if (Kind.isMergeableConst16()) 565 return MergeableConst16Section; 566 if (Kind.isReadOnly()) 567 return ReadOnlySection; 568 569 if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection; 570 assert(Kind.isReadOnlyWithRel() && "Unknown section kind"); 571 return DataRelROSection; 572 } 573 574 //===----------------------------------------------------------------------===// 575 // MachO 576 //===----------------------------------------------------------------------===// 577 578 const MCSection *TargetLoweringObjectFileMachO:: 579 getMachOSection(const char *Name, bool isDirective, SectionKind K) { 580 // FOR NOW, Just forward. 581 return getOrCreateSection(Name, isDirective, K); 582 } 583 584 585 586 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx, 587 const TargetMachine &TM) { 588 TargetLoweringObjectFile::Initialize(Ctx, TM); 589 TextSection = getOrCreateSection("\t.text", true, 590 SectionKind::getText()); 591 DataSection = getOrCreateSection("\t.data", true, 592 SectionKind::getDataRel()); 593 594 CStringSection = getOrCreateSection("\t.cstring", true, 595 SectionKind::getMergeable1ByteCString()); 596 UStringSection = getOrCreateSection("__TEXT,__ustring", false, 597 SectionKind::getMergeable2ByteCString()); 598 FourByteConstantSection = getOrCreateSection("\t.literal4\n", true, 599 SectionKind::getMergeableConst4()); 600 EightByteConstantSection = getOrCreateSection("\t.literal8\n", true, 601 SectionKind::getMergeableConst8()); 602 603 // ld_classic doesn't support .literal16 in 32-bit mode, and ld64 falls back 604 // to using it in -static mode. 605 if (TM.getRelocationModel() != Reloc::Static && 606 TM.getTargetData()->getPointerSize() == 32) 607 SixteenByteConstantSection = 608 getOrCreateSection("\t.literal16\n", true, 609 SectionKind::getMergeableConst16()); 610 else 611 SixteenByteConstantSection = 0; 612 613 ReadOnlySection = getOrCreateSection("\t.const", true, 614 SectionKind::getReadOnly()); 615 616 TextCoalSection = 617 getOrCreateSection("\t__TEXT,__textcoal_nt,coalesced,pure_instructions", 618 false, SectionKind::getText()); 619 ConstTextCoalSection = getOrCreateSection("\t__TEXT,__const_coal,coalesced", 620 false, 621 SectionKind::getText()); 622 ConstDataCoalSection = getOrCreateSection("\t__DATA,__const_coal,coalesced", 623 false, 624 SectionKind::getText()); 625 ConstDataSection = getOrCreateSection("\t.const_data", true, 626 SectionKind::getReadOnlyWithRel()); 627 DataCoalSection = getOrCreateSection("\t__DATA,__datacoal_nt,coalesced", 628 false, 629 SectionKind::getDataRel()); 630 631 if (TM.getRelocationModel() == Reloc::Static) { 632 StaticCtorSection = 633 getOrCreateSection(".constructor", true, SectionKind::getDataRel()); 634 StaticDtorSection = 635 getOrCreateSection(".destructor", true, SectionKind::getDataRel()); 636 } else { 637 StaticCtorSection = 638 getOrCreateSection(".mod_init_func", true, SectionKind::getDataRel()); 639 StaticDtorSection = 640 getOrCreateSection(".mod_term_func", true, SectionKind::getDataRel()); 641 } 642 643 // Exception Handling. 644 LSDASection = getOrCreateSection("__DATA,__gcc_except_tab", false, 645 SectionKind::getDataRel()); 646 EHFrameSection = 647 getOrCreateSection("__TEXT,__eh_frame,coalesced,no_toc+strip_static_syms" 648 "+live_support", false, SectionKind::getReadOnly()); 649 650 // Debug Information. 651 // FIXME: Don't use 'directive' syntax: need flags for debug/regular?? 652 // FIXME: Need __DWARF segment. 653 DwarfAbbrevSection = 654 getOrCreateSection(".section __DWARF,__debug_abbrev,regular,debug", true, 655 SectionKind::getMetadata()); 656 DwarfInfoSection = 657 getOrCreateSection(".section __DWARF,__debug_info,regular,debug", true, 658 SectionKind::getMetadata()); 659 DwarfLineSection = 660 getOrCreateSection(".section __DWARF,__debug_line,regular,debug", true, 661 SectionKind::getMetadata()); 662 DwarfFrameSection = 663 getOrCreateSection(".section __DWARF,__debug_frame,regular,debug", true, 664 SectionKind::getMetadata()); 665 DwarfPubNamesSection = 666 getOrCreateSection(".section __DWARF,__debug_pubnames,regular,debug", true, 667 SectionKind::getMetadata()); 668 DwarfPubTypesSection = 669 getOrCreateSection(".section __DWARF,__debug_pubtypes,regular,debug", true, 670 SectionKind::getMetadata()); 671 DwarfStrSection = 672 getOrCreateSection(".section __DWARF,__debug_str,regular,debug", true, 673 SectionKind::getMetadata()); 674 DwarfLocSection = 675 getOrCreateSection(".section __DWARF,__debug_loc,regular,debug", true, 676 SectionKind::getMetadata()); 677 DwarfARangesSection = 678 getOrCreateSection(".section __DWARF,__debug_aranges,regular,debug", true, 679 SectionKind::getMetadata()); 680 DwarfRangesSection = 681 getOrCreateSection(".section __DWARF,__debug_ranges,regular,debug", true, 682 SectionKind::getMetadata()); 683 DwarfMacroInfoSection = 684 getOrCreateSection(".section __DWARF,__debug_macinfo,regular,debug", true, 685 SectionKind::getMetadata()); 686 DwarfDebugInlineSection = 687 getOrCreateSection(".section __DWARF,__debug_inlined,regular,debug", true, 688 SectionKind::getMetadata()); 689 } 690 691 const MCSection *TargetLoweringObjectFileMachO:: 692 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind, 693 Mangler *Mang, const TargetMachine &TM) const { 694 return getOrCreateSection(GV->getSection().c_str(), false, Kind); 695 } 696 697 const MCSection *TargetLoweringObjectFileMachO:: 698 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind, 699 Mangler *Mang, const TargetMachine &TM) const { 700 assert(!Kind.isThreadLocal() && "Darwin doesn't support TLS"); 701 702 if (Kind.isText()) 703 return GV->isWeakForLinker() ? TextCoalSection : TextSection; 704 705 // If this is weak/linkonce, put this in a coalescable section, either in text 706 // or data depending on if it is writable. 707 if (GV->isWeakForLinker()) { 708 if (Kind.isReadOnly()) 709 return ConstTextCoalSection; 710 return DataCoalSection; 711 } 712 713 // FIXME: Alignment check should be handled by section classifier. 714 if (Kind.isMergeable1ByteCString() || 715 Kind.isMergeable2ByteCString()) { 716 if (TM.getTargetData()->getPreferredAlignment( 717 cast<GlobalVariable>(GV)) < 32) { 718 if (Kind.isMergeable1ByteCString()) 719 return CStringSection; 720 assert(Kind.isMergeable2ByteCString()); 721 return UStringSection; 722 } 723 } 724 725 if (Kind.isMergeableConst()) { 726 if (Kind.isMergeableConst4()) 727 return FourByteConstantSection; 728 if (Kind.isMergeableConst8()) 729 return EightByteConstantSection; 730 if (Kind.isMergeableConst16() && SixteenByteConstantSection) 731 return SixteenByteConstantSection; 732 } 733 734 // Otherwise, if it is readonly, but not something we can specially optimize, 735 // just drop it in .const. 736 if (Kind.isReadOnly()) 737 return ReadOnlySection; 738 739 // If this is marked const, put it into a const section. But if the dynamic 740 // linker needs to write to it, put it in the data segment. 741 if (Kind.isReadOnlyWithRel()) 742 return ConstDataSection; 743 744 // Otherwise, just drop the variable in the normal data section. 745 return DataSection; 746 } 747 748 const MCSection * 749 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const { 750 // If this constant requires a relocation, we have to put it in the data 751 // segment, not in the text segment. 752 if (Kind.isDataRel()) 753 return ConstDataSection; 754 755 if (Kind.isMergeableConst4()) 756 return FourByteConstantSection; 757 if (Kind.isMergeableConst8()) 758 return EightByteConstantSection; 759 if (Kind.isMergeableConst16() && SixteenByteConstantSection) 760 return SixteenByteConstantSection; 761 return ReadOnlySection; // .const 762 } 763 764 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide 765 /// not to emit the UsedDirective for some symbols in llvm.used. 766 // FIXME: REMOVE this (rdar://7071300) 767 bool TargetLoweringObjectFileMachO:: 768 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const { 769 /// On Darwin, internally linked data beginning with "L" or "l" does not have 770 /// the directive emitted (this occurs in ObjC metadata). 771 if (!GV) return false; 772 773 // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix. 774 if (GV->hasLocalLinkage() && !isa<Function>(GV)) { 775 // FIXME: ObjC metadata is currently emitted as internal symbols that have 776 // \1L and \0l prefixes on them. Fix them to be Private/LinkerPrivate and 777 // this horrible hack can go away. 778 const std::string &Name = Mang->getMangledName(GV); 779 if (Name[0] == 'L' || Name[0] == 'l') 780 return false; 781 } 782 783 return true; 784 } 785 786 787 //===----------------------------------------------------------------------===// 788 // COFF 789 //===----------------------------------------------------------------------===// 790 791 const MCSection *TargetLoweringObjectFileCOFF:: 792 getCOFFSection(const char *Name, bool isDirective, SectionKind K) { 793 return getOrCreateSection(Name, isDirective, K); 794 } 795 796 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx, 797 const TargetMachine &TM) { 798 TargetLoweringObjectFile::Initialize(Ctx, TM); 799 TextSection = getOrCreateSection("\t.text", true, 800 SectionKind::getText()); 801 DataSection = getOrCreateSection("\t.data", true, 802 SectionKind::getDataRel()); 803 StaticCtorSection = 804 getOrCreateSection(".ctors", false, SectionKind::getDataRel()); 805 StaticDtorSection = 806 getOrCreateSection(".dtors", false, SectionKind::getDataRel()); 807 808 809 // Debug info. 810 // FIXME: Don't use 'directive' mode here. 811 DwarfAbbrevSection = 812 getOrCreateSection("\t.section\t.debug_abbrev,\"dr\"", 813 true, SectionKind::getMetadata()); 814 DwarfInfoSection = 815 getOrCreateSection("\t.section\t.debug_info,\"dr\"", 816 true, SectionKind::getMetadata()); 817 DwarfLineSection = 818 getOrCreateSection("\t.section\t.debug_line,\"dr\"", 819 true, SectionKind::getMetadata()); 820 DwarfFrameSection = 821 getOrCreateSection("\t.section\t.debug_frame,\"dr\"", 822 true, SectionKind::getMetadata()); 823 DwarfPubNamesSection = 824 getOrCreateSection("\t.section\t.debug_pubnames,\"dr\"", 825 true, SectionKind::getMetadata()); 826 DwarfPubTypesSection = 827 getOrCreateSection("\t.section\t.debug_pubtypes,\"dr\"", 828 true, SectionKind::getMetadata()); 829 DwarfStrSection = 830 getOrCreateSection("\t.section\t.debug_str,\"dr\"", 831 true, SectionKind::getMetadata()); 832 DwarfLocSection = 833 getOrCreateSection("\t.section\t.debug_loc,\"dr\"", 834 true, SectionKind::getMetadata()); 835 DwarfARangesSection = 836 getOrCreateSection("\t.section\t.debug_aranges,\"dr\"", 837 true, SectionKind::getMetadata()); 838 DwarfRangesSection = 839 getOrCreateSection("\t.section\t.debug_ranges,\"dr\"", 840 true, SectionKind::getMetadata()); 841 DwarfMacroInfoSection = 842 getOrCreateSection("\t.section\t.debug_macinfo,\"dr\"", 843 true, SectionKind::getMetadata()); 844 } 845 846 const MCSection *TargetLoweringObjectFileCOFF:: 847 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind, 848 Mangler *Mang, const TargetMachine &TM) const { 849 return getOrCreateSection(GV->getSection().c_str(), false, Kind); 850 } 851 852 853 void TargetLoweringObjectFileCOFF:: 854 getSectionFlagsAsString(SectionKind Kind, SmallVectorImpl<char> &Str) const { 855 // FIXME: Inefficient. 856 std::string Res = ",\""; 857 if (Kind.isText()) 858 Res += 'x'; 859 if (Kind.isWriteable()) 860 Res += 'w'; 861 Res += "\""; 862 863 Str.append(Res.begin(), Res.end()); 864 } 865 866 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) { 867 if (Kind.isText()) 868 return ".text$linkonce"; 869 if (Kind.isWriteable()) 870 return ".data$linkonce"; 871 return ".rdata$linkonce"; 872 } 873 874 875 const MCSection *TargetLoweringObjectFileCOFF:: 876 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind, 877 Mangler *Mang, const TargetMachine &TM) const { 878 assert(!Kind.isThreadLocal() && "Doesn't support TLS"); 879 880 // If this global is linkonce/weak and the target handles this by emitting it 881 // into a 'uniqued' section name, create and return the section now. 882 if (GV->isWeakForLinker()) { 883 const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind); 884 std::string Name = Mang->makeNameProper(GV->getNameStr()); 885 return getOrCreateSection((Prefix+Name).c_str(), false, Kind); 886 } 887 888 if (Kind.isText()) 889 return getTextSection(); 890 891 return getDataSection(); 892 } 893 894