lib/CodeGen/TargetLoweringObjectFileImpl.cpp

   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/Constants.h"
  17 #include "llvm/DerivedTypes.h"
  18 #include "llvm/Function.h"
  19 #include "llvm/GlobalVariable.h"
  20 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
  21 #include "llvm/MC/MCContext.h"
  22 #include "llvm/MC/MCExpr.h"
  23 #include "llvm/MC/MCSectionMachO.h"
  24 #include "llvm/MC/MCSectionELF.h"
  25 #include "llvm/MC/MCSectionCOFF.h"
  26 #include "llvm/MC/MCSymbol.h"
  27 #include "llvm/Target/Mangler.h"
  28 #include "llvm/Target/TargetData.h"
  29 #include "llvm/Target/TargetMachine.h"
  30 #include "llvm/Target/TargetOptions.h"
  31 #include "llvm/Support/Dwarf.h"
  32 #include "llvm/Support/ELF.h"
  33 #include "llvm/Support/ErrorHandling.h"
  34 #include "llvm/Support/raw_ostream.h"
  35 #include "llvm/ADT/SmallString.h"
  36 #include "llvm/ADT/StringExtras.h"
  37 #include "llvm/ADT/Triple.h"
  38 using namespace llvm;
  39 using namespace dwarf;
  40
  41 //===----------------------------------------------------------------------===//
  42 //                                  ELF
  43 //===----------------------------------------------------------------------===//
  44
  45 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
  46                                              const TargetMachine &TM) {
  47   TargetLoweringObjectFile::Initialize(Ctx, TM);
  48
  49   BSSSection =
  50     getContext().getELFSection(".bss", ELF::SHT_NOBITS,
  51                                ELF::SHF_WRITE |ELF::SHF_ALLOC,
  52                                SectionKind::getBSS());
  53
  54   TextSection =
  55     getContext().getELFSection(".text", ELF::SHT_PROGBITS,
  56                                ELF::SHF_EXECINSTR |
  57                                ELF::SHF_ALLOC,
  58                                SectionKind::getText());
  59
  60   DataSection =
  61     getContext().getELFSection(".data", ELF::SHT_PROGBITS,
  62                                ELF::SHF_WRITE |ELF::SHF_ALLOC,
  63                                SectionKind::getDataRel());
  64
  65   ReadOnlySection =
  66     getContext().getELFSection(".rodata", ELF::SHT_PROGBITS,
  67                                ELF::SHF_ALLOC,
  68                                SectionKind::getReadOnly());
  69
  70   TLSDataSection =
  71     getContext().getELFSection(".tdata", ELF::SHT_PROGBITS,
  72                                ELF::SHF_ALLOC | ELF::SHF_TLS |
  73                                ELF::SHF_WRITE,
  74                                SectionKind::getThreadData());
  75
  76   TLSBSSSection =
  77     getContext().getELFSection(".tbss", ELF::SHT_NOBITS,
  78                                ELF::SHF_ALLOC | ELF::SHF_TLS |
  79                                ELF::SHF_WRITE,
  80                                SectionKind::getThreadBSS());
  81
  82   DataRelSection =
  83     getContext().getELFSection(".data.rel", ELF::SHT_PROGBITS,
  84                                ELF::SHF_ALLOC |ELF::SHF_WRITE,
  85                                SectionKind::getDataRel());
  86
  87   DataRelLocalSection =
  88     getContext().getELFSection(".data.rel.local", ELF::SHT_PROGBITS,
  89                                ELF::SHF_ALLOC |ELF::SHF_WRITE,
  90                                SectionKind::getDataRelLocal());
  91
  92   DataRelROSection =
  93     getContext().getELFSection(".data.rel.ro", ELF::SHT_PROGBITS,
  94                                ELF::SHF_ALLOC |ELF::SHF_WRITE,
  95                                SectionKind::getReadOnlyWithRel());
  96
  97   DataRelROLocalSection =
  98     getContext().getELFSection(".data.rel.ro.local", ELF::SHT_PROGBITS,
  99                                ELF::SHF_ALLOC |ELF::SHF_WRITE,
 100                                SectionKind::getReadOnlyWithRelLocal());
 101
 102   MergeableConst4Section =
 103     getContext().getELFSection(".rodata.cst4", ELF::SHT_PROGBITS,
 104                                ELF::SHF_ALLOC |ELF::SHF_MERGE,
 105                                SectionKind::getMergeableConst4());
 106
 107   MergeableConst8Section =
 108     getContext().getELFSection(".rodata.cst8", ELF::SHT_PROGBITS,
 109                                ELF::SHF_ALLOC |ELF::SHF_MERGE,
 110                                SectionKind::getMergeableConst8());
 111
 112   MergeableConst16Section =
 113     getContext().getELFSection(".rodata.cst16", ELF::SHT_PROGBITS,
 114                                ELF::SHF_ALLOC |ELF::SHF_MERGE,
 115                                SectionKind::getMergeableConst16());
 116
 117   StaticCtorSection =
 118     getContext().getELFSection(".ctors", ELF::SHT_PROGBITS,
 119                                ELF::SHF_ALLOC |ELF::SHF_WRITE,
 120                                SectionKind::getDataRel());
 121
 122   StaticDtorSection =
 123     getContext().getELFSection(".dtors", ELF::SHT_PROGBITS,
 124                                ELF::SHF_ALLOC |ELF::SHF_WRITE,
 125                                SectionKind::getDataRel());
 126
 127   // Exception Handling Sections.
 128
 129   // FIXME: We're emitting LSDA info into a readonly section on ELF, even though
 130   // it contains relocatable pointers.  In PIC mode, this is probably a big
 131   // runtime hit for C++ apps.  Either the contents of the LSDA need to be
 132   // adjusted or this should be a data section.
 133   LSDASection =
 134     getContext().getELFSection(".gcc_except_table", ELF::SHT_PROGBITS,
 135                                ELF::SHF_ALLOC,
 136                                SectionKind::getReadOnly());
 137   // Debug Info Sections.
 138   DwarfAbbrevSection =
 139     getContext().getELFSection(".debug_abbrev", ELF::SHT_PROGBITS, 0,
 140                                SectionKind::getMetadata());
 141   DwarfInfoSection =
 142     getContext().getELFSection(".debug_info", ELF::SHT_PROGBITS, 0,
 143                                SectionKind::getMetadata());
 144   DwarfLineSection =
 145     getContext().getELFSection(".debug_line", ELF::SHT_PROGBITS, 0,
 146                                SectionKind::getMetadata());
 147   DwarfFrameSection =
 148     getContext().getELFSection(".debug_frame", ELF::SHT_PROGBITS, 0,
 149                                SectionKind::getMetadata());
 150   DwarfPubNamesSection =
 151     getContext().getELFSection(".debug_pubnames", ELF::SHT_PROGBITS, 0,
 152                                SectionKind::getMetadata());
 153   DwarfPubTypesSection =
 154     getContext().getELFSection(".debug_pubtypes", ELF::SHT_PROGBITS, 0,
 155                                SectionKind::getMetadata());
 156   DwarfStrSection =
 157     getContext().getELFSection(".debug_str", ELF::SHT_PROGBITS, 0,
 158                                SectionKind::getMetadata());
 159   DwarfLocSection =
 160     getContext().getELFSection(".debug_loc", ELF::SHT_PROGBITS, 0,
 161                                SectionKind::getMetadata());
 162   DwarfARangesSection =
 163     getContext().getELFSection(".debug_aranges", ELF::SHT_PROGBITS, 0,
 164                                SectionKind::getMetadata());
 165   DwarfRangesSection =
 166     getContext().getELFSection(".debug_ranges", ELF::SHT_PROGBITS, 0,
 167                                SectionKind::getMetadata());
 168   DwarfMacroInfoSection =
 169     getContext().getELFSection(".debug_macinfo", ELF::SHT_PROGBITS, 0,
 170                                SectionKind::getMetadata());
 171 }
 172
 173 const MCSection *TargetLoweringObjectFileELF::getEHFrameSection() const {
 174   return getContext().getELFSection(".eh_frame", ELF::SHT_PROGBITS,
 175                                     ELF::SHF_ALLOC,
 176                                     SectionKind::getDataRel());
 177 }
 178
 179 static SectionKind
 180 getELFKindForNamedSection(StringRef Name, SectionKind K) {
 181   // FIXME: Why is this here? Codegen is should not be in the business
 182   // of figuring section flags. If the user wrote section(".eh_frame"),
 183   // we should just pass that to MC which will defer to the assembly
 184   // or use its default if producing an object file.
 185   if (Name.empty() || Name[0] != '.') return K;
 186
 187   // Some lame default implementation based on some magic section names.
 188   if (Name == ".bss" ||
 189       Name.startswith(".bss.") ||
 190       Name.startswith(".gnu.linkonce.b.") ||
 191       Name.startswith(".llvm.linkonce.b.") ||
 192       Name == ".sbss" ||
 193       Name.startswith(".sbss.") ||
 194       Name.startswith(".gnu.linkonce.sb.") ||
 195       Name.startswith(".llvm.linkonce.sb."))
 196     return SectionKind::getBSS();
 197
 198   if (Name == ".tdata" ||
 199       Name.startswith(".tdata.") ||
 200       Name.startswith(".gnu.linkonce.td.") ||
 201       Name.startswith(".llvm.linkonce.td."))
 202     return SectionKind::getThreadData();
 203
 204   if (Name == ".tbss" ||
 205       Name.startswith(".tbss.") ||
 206       Name.startswith(".gnu.linkonce.tb.") ||
 207       Name.startswith(".llvm.linkonce.tb."))
 208     return SectionKind::getThreadBSS();
 209
 210   if (Name == ".eh_frame")
 211     return SectionKind::getDataRel();
 212
 213   return K;
 214 }
 215
 216
 217 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
 218
 219   if (Name == ".init_array")
 220     return ELF::SHT_INIT_ARRAY;
 221
 222   if (Name == ".fini_array")
 223     return ELF::SHT_FINI_ARRAY;
 224
 225   if (Name == ".preinit_array")
 226     return ELF::SHT_PREINIT_ARRAY;
 227
 228   if (K.isBSS() || K.isThreadBSS())
 229     return ELF::SHT_NOBITS;
 230
 231   return ELF::SHT_PROGBITS;
 232 }
 233
 234
 235 static unsigned
 236 getELFSectionFlags(SectionKind K) {
 237   unsigned Flags = 0;
 238
 239   if (!K.isMetadata())
 240     Flags |= ELF::SHF_ALLOC;
 241
 242   if (K.isText())
 243     Flags |= ELF::SHF_EXECINSTR;
 244
 245   if (K.isWriteable())
 246     Flags |= ELF::SHF_WRITE;
 247
 248   if (K.isThreadLocal())
 249     Flags |= ELF::SHF_TLS;
 250
 251   // K.isMergeableConst() is left out to honour PR4650
 252   if (K.isMergeableCString() || K.isMergeableConst4() ||
 253       K.isMergeableConst8() || K.isMergeableConst16())
 254     Flags |= ELF::SHF_MERGE;
 255
 256   if (K.isMergeableCString())
 257     Flags |= ELF::SHF_STRINGS;
 258
 259   return Flags;
 260 }
 261
 262
 263 const MCSection *TargetLoweringObjectFileELF::
 264 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
 265                          Mangler *Mang, const TargetMachine &TM) const {
 266   StringRef SectionName = GV->getSection();
 267
 268   // Infer section flags from the section name if we can.
 269   Kind = getELFKindForNamedSection(SectionName, Kind);
 270
 271   return getContext().getELFSection(SectionName,
 272                                     getELFSectionType(SectionName, Kind),
 273                                     getELFSectionFlags(Kind), Kind);
 274 }
 275
 276 /// getSectionPrefixForGlobal - Return the section prefix name used by options
 277 /// FunctionsSections and DataSections.
 278 static const char *getSectionPrefixForGlobal(SectionKind Kind) {
 279   if (Kind.isText())                 return ".text.";
 280   if (Kind.isReadOnly())             return ".rodata.";
 281
 282   if (Kind.isThreadData())           return ".tdata.";
 283   if (Kind.isThreadBSS())            return ".tbss.";
 284
 285   if (Kind.isDataNoRel())            return ".data.";
 286   if (Kind.isDataRelLocal())         return ".data.rel.local.";
 287   if (Kind.isDataRel())              return ".data.rel.";
 288   if (Kind.isReadOnlyWithRelLocal()) return ".data.rel.ro.local.";
 289
 290   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
 291   return ".data.rel.ro.";
 292 }
 293
 294
 295 const MCSection *TargetLoweringObjectFileELF::
 296 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
 297                        Mangler *Mang, const TargetMachine &TM) const {
 298   // If we have -ffunction-section or -fdata-section then we should emit the
 299   // global value to a uniqued section specifically for it.
 300   bool EmitUniquedSection;
 301   if (Kind.isText())
 302     EmitUniquedSection = TM.getFunctionSections();
 303   else
 304     EmitUniquedSection = TM.getDataSections();
 305
 306   // If this global is linkonce/weak and the target handles this by emitting it
 307   // into a 'uniqued' section name, create and return the section now.
 308   if ((GV->isWeakForLinker() || EmitUniquedSection) &&
 309       !Kind.isCommon() && !Kind.isBSS()) {
 310     const char *Prefix;
 311     Prefix = getSectionPrefixForGlobal(Kind);
 312
 313     SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
 314     MCSymbol *Sym = Mang->getSymbol(GV);
 315     Name.append(Sym->getName().begin(), Sym->getName().end());
 316     StringRef Group = "";
 317     unsigned Flags = getELFSectionFlags(Kind);
 318     if (GV->isWeakForLinker()) {
 319       Group = Sym->getName();
 320       Flags |= ELF::SHF_GROUP;
 321     }
 322
 323     return getContext().getELFSection(Name.str(),
 324                                       getELFSectionType(Name.str(), Kind),
 325                                       Flags, Kind, 0, Group);
 326   }
 327
 328   if (Kind.isText()) return TextSection;
 329
 330   if (Kind.isMergeable1ByteCString() ||
 331       Kind.isMergeable2ByteCString() ||
 332       Kind.isMergeable4ByteCString()) {
 333
 334     // We also need alignment here.
 335     // FIXME: this is getting the alignment of the character, not the
 336     // alignment of the global!
 337     unsigned Align =
 338       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV));
 339
 340     const char *SizeSpec = ".rodata.str1.";
 341     if (Kind.isMergeable2ByteCString())
 342       SizeSpec = ".rodata.str2.";
 343     else if (Kind.isMergeable4ByteCString())
 344       SizeSpec = ".rodata.str4.";
 345     else
 346       assert(Kind.isMergeable1ByteCString() && "unknown string width");
 347
 348
 349     std::string Name = SizeSpec + utostr(Align);
 350     return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
 351                                       ELF::SHF_ALLOC |
 352                                       ELF::SHF_MERGE |
 353                                       ELF::SHF_STRINGS,
 354                                       Kind);
 355   }
 356
 357   if (Kind.isMergeableConst()) {
 358     if (Kind.isMergeableConst4() && MergeableConst4Section)
 359       return MergeableConst4Section;
 360     if (Kind.isMergeableConst8() && MergeableConst8Section)
 361       return MergeableConst8Section;
 362     if (Kind.isMergeableConst16() && MergeableConst16Section)
 363       return MergeableConst16Section;
 364     return ReadOnlySection;  // .const
 365   }
 366
 367   if (Kind.isReadOnly())             return ReadOnlySection;
 368
 369   if (Kind.isThreadData())           return TLSDataSection;
 370   if (Kind.isThreadBSS())            return TLSBSSSection;
 371
 372   // Note: we claim that common symbols are put in BSSSection, but they are
 373   // really emitted with the magic .comm directive, which creates a symbol table
 374   // entry but not a section.
 375   if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
 376
 377   if (Kind.isDataNoRel())            return DataSection;
 378   if (Kind.isDataRelLocal())         return DataRelLocalSection;
 379   if (Kind.isDataRel())              return DataRelSection;
 380   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
 381
 382   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
 383   return DataRelROSection;
 384 }
 385
 386 /// getSectionForConstant - Given a mergeable constant with the
 387 /// specified size and relocation information, return a section that it
 388 /// should be placed in.
 389 const MCSection *TargetLoweringObjectFileELF::
 390 getSectionForConstant(SectionKind Kind) const {
 391   if (Kind.isMergeableConst4() && MergeableConst4Section)
 392     return MergeableConst4Section;
 393   if (Kind.isMergeableConst8() && MergeableConst8Section)
 394     return MergeableConst8Section;
 395   if (Kind.isMergeableConst16() && MergeableConst16Section)
 396     return MergeableConst16Section;
 397   if (Kind.isReadOnly())
 398     return ReadOnlySection;
 399
 400   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
 401   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
 402   return DataRelROSection;
 403 }
 404
 405 const MCExpr *TargetLoweringObjectFileELF::
 406 getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
 407                                MachineModuleInfo *MMI,
 408                                unsigned Encoding, MCStreamer &Streamer) const {
 409
 410   if (Encoding & dwarf::DW_EH_PE_indirect) {
 411     MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
 412
 413     SmallString<128> Name;
 414     Mang->getNameWithPrefix(Name, GV, true);
 415     Name += ".DW.stub";
 416
 417     // Add information about the stub reference to ELFMMI so that the stub
 418     // gets emitted by the asmprinter.
 419     MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
 420     MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
 421     if (StubSym.getPointer() == 0) {
 422       MCSymbol *Sym = Mang->getSymbol(GV);
 423       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
 424     }
 425
 426     return TargetLoweringObjectFile::
 427       getExprForDwarfReference(SSym, Mang, MMI,
 428                                Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
 429   }
 430
 431   return TargetLoweringObjectFile::
 432     getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, Streamer);
 433 }
 434
 435 //===----------------------------------------------------------------------===//
 436 //                                 MachO
 437 //===----------------------------------------------------------------------===//
 438
 439 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
 440                                                const TargetMachine &TM) {
 441   // _foo.eh symbols are currently always exported so that the linker knows
 442   // about them.  This is not necessary on 10.6 and later, but it
 443   // doesn't hurt anything.
 444   // FIXME: I need to get this from Triple.
 445   IsFunctionEHSymbolGlobal = true;
 446   IsFunctionEHFrameSymbolPrivate = false;
 447   SupportsWeakOmittedEHFrame = false;
 448
 449   Triple T(((LLVMTargetMachine&)TM).getTargetTriple());
 450   if (T.getOS() == Triple::Darwin) {
 451     switch (T.getDarwinMajorNumber()) {
 452     case 7:  // 10.3 Panther.
 453     case 8:  // 10.4 Tiger.
 454       CommDirectiveSupportsAlignment = false;
 455       break;
 456     case 9:   // 10.5 Leopard.
 457     case 10:  // 10.6 SnowLeopard.
 458       break;
 459     }
 460   }
 461
 462   TargetLoweringObjectFile::Initialize(Ctx, TM);
 463
 464   TextSection // .text
 465     = getContext().getMachOSection("__TEXT", "__text",
 466                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
 467                                    SectionKind::getText());
 468   DataSection // .data
 469     = getContext().getMachOSection("__DATA", "__data", 0,
 470                                    SectionKind::getDataRel());
 471
 472   TLSDataSection // .tdata
 473     = getContext().getMachOSection("__DATA", "__thread_data",
 474                                    MCSectionMachO::S_THREAD_LOCAL_REGULAR,
 475                                    SectionKind::getDataRel());
 476   TLSBSSSection // .tbss
 477     = getContext().getMachOSection("__DATA", "__thread_bss",
 478                                    MCSectionMachO::S_THREAD_LOCAL_ZEROFILL,
 479                                    SectionKind::getThreadBSS());
 480
 481   // TODO: Verify datarel below.
 482   TLSTLVSection // .tlv
 483     = getContext().getMachOSection("__DATA", "__thread_vars",
 484                                    MCSectionMachO::S_THREAD_LOCAL_VARIABLES,
 485                                    SectionKind::getDataRel());
 486
 487   TLSThreadInitSection
 488     = getContext().getMachOSection("__DATA", "__thread_init",
 489                           MCSectionMachO::S_THREAD_LOCAL_INIT_FUNCTION_POINTERS,
 490                           SectionKind::getDataRel());
 491
 492   CStringSection // .cstring
 493     = getContext().getMachOSection("__TEXT", "__cstring",
 494                                    MCSectionMachO::S_CSTRING_LITERALS,
 495                                    SectionKind::getMergeable1ByteCString());
 496   UStringSection
 497     = getContext().getMachOSection("__TEXT","__ustring", 0,
 498                                    SectionKind::getMergeable2ByteCString());
 499   FourByteConstantSection // .literal4
 500     = getContext().getMachOSection("__TEXT", "__literal4",
 501                                    MCSectionMachO::S_4BYTE_LITERALS,
 502                                    SectionKind::getMergeableConst4());
 503   EightByteConstantSection // .literal8
 504     = getContext().getMachOSection("__TEXT", "__literal8",
 505                                    MCSectionMachO::S_8BYTE_LITERALS,
 506                                    SectionKind::getMergeableConst8());
 507
 508   // ld_classic doesn't support .literal16 in 32-bit mode, and ld64 falls back
 509   // to using it in -static mode.
 510   SixteenByteConstantSection = 0;
 511   if (TM.getRelocationModel() != Reloc::Static &&
 512       TM.getTargetData()->getPointerSize() == 32)
 513     SixteenByteConstantSection =   // .literal16
 514       getContext().getMachOSection("__TEXT", "__literal16",
 515                                    MCSectionMachO::S_16BYTE_LITERALS,
 516                                    SectionKind::getMergeableConst16());
 517
 518   ReadOnlySection  // .const
 519     = getContext().getMachOSection("__TEXT", "__const", 0,
 520                                    SectionKind::getReadOnly());
 521
 522   TextCoalSection
 523     = getContext().getMachOSection("__TEXT", "__textcoal_nt",
 524                                    MCSectionMachO::S_COALESCED |
 525                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
 526                                    SectionKind::getText());
 527   ConstTextCoalSection
 528     = getContext().getMachOSection("__TEXT", "__const_coal",
 529                                    MCSectionMachO::S_COALESCED,
 530                                    SectionKind::getReadOnly());
 531   ConstDataSection  // .const_data
 532     = getContext().getMachOSection("__DATA", "__const", 0,
 533                                    SectionKind::getReadOnlyWithRel());
 534   DataCoalSection
 535     = getContext().getMachOSection("__DATA","__datacoal_nt",
 536                                    MCSectionMachO::S_COALESCED,
 537                                    SectionKind::getDataRel());
 538   DataCommonSection
 539     = getContext().getMachOSection("__DATA","__common",
 540                                    MCSectionMachO::S_ZEROFILL,
 541                                    SectionKind::getBSS());
 542   DataBSSSection
 543     = getContext().getMachOSection("__DATA","__bss", MCSectionMachO::S_ZEROFILL,
 544                                    SectionKind::getBSS());
 545
 546
 547   LazySymbolPointerSection
 548     = getContext().getMachOSection("__DATA", "__la_symbol_ptr",
 549                                    MCSectionMachO::S_LAZY_SYMBOL_POINTERS,
 550                                    SectionKind::getMetadata());
 551   NonLazySymbolPointerSection
 552     = getContext().getMachOSection("__DATA", "__nl_symbol_ptr",
 553                                    MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS,
 554                                    SectionKind::getMetadata());
 555
 556   if (TM.getRelocationModel() == Reloc::Static) {
 557     StaticCtorSection
 558       = getContext().getMachOSection("__TEXT", "__constructor", 0,
 559                                      SectionKind::getDataRel());
 560     StaticDtorSection
 561       = getContext().getMachOSection("__TEXT", "__destructor", 0,
 562                                      SectionKind::getDataRel());
 563   } else {
 564     StaticCtorSection
 565       = getContext().getMachOSection("__DATA", "__mod_init_func",
 566                                      MCSectionMachO::S_MOD_INIT_FUNC_POINTERS,
 567                                      SectionKind::getDataRel());
 568     StaticDtorSection
 569       = getContext().getMachOSection("__DATA", "__mod_term_func",
 570                                      MCSectionMachO::S_MOD_TERM_FUNC_POINTERS,
 571                                      SectionKind::getDataRel());
 572   }
 573
 574   // Exception Handling.
 575   LSDASection = getContext().getMachOSection("__TEXT", "__gcc_except_tab", 0,
 576                                              SectionKind::getReadOnlyWithRel());
 577   // Debug Information.
 578   DwarfAbbrevSection =
 579     getContext().getMachOSection("__DWARF", "__debug_abbrev",
 580                                  MCSectionMachO::S_ATTR_DEBUG,
 581                                  SectionKind::getMetadata());
 582   DwarfInfoSection =
 583     getContext().getMachOSection("__DWARF", "__debug_info",
 584                                  MCSectionMachO::S_ATTR_DEBUG,
 585                                  SectionKind::getMetadata());
 586   DwarfLineSection =
 587     getContext().getMachOSection("__DWARF", "__debug_line",
 588                                  MCSectionMachO::S_ATTR_DEBUG,
 589                                  SectionKind::getMetadata());
 590   DwarfFrameSection =
 591     getContext().getMachOSection("__DWARF", "__debug_frame",
 592                                  MCSectionMachO::S_ATTR_DEBUG,
 593                                  SectionKind::getMetadata());
 594   DwarfPubNamesSection =
 595     getContext().getMachOSection("__DWARF", "__debug_pubnames",
 596                                  MCSectionMachO::S_ATTR_DEBUG,
 597                                  SectionKind::getMetadata());
 598   DwarfPubTypesSection =
 599     getContext().getMachOSection("__DWARF", "__debug_pubtypes",
 600                                  MCSectionMachO::S_ATTR_DEBUG,
 601                                  SectionKind::getMetadata());
 602   DwarfStrSection =
 603     getContext().getMachOSection("__DWARF", "__debug_str",
 604                                  MCSectionMachO::S_ATTR_DEBUG,
 605                                  SectionKind::getMetadata());
 606   DwarfLocSection =
 607     getContext().getMachOSection("__DWARF", "__debug_loc",
 608                                  MCSectionMachO::S_ATTR_DEBUG,
 609                                  SectionKind::getMetadata());
 610   DwarfARangesSection =
 611     getContext().getMachOSection("__DWARF", "__debug_aranges",
 612                                  MCSectionMachO::S_ATTR_DEBUG,
 613                                  SectionKind::getMetadata());
 614   DwarfRangesSection =
 615     getContext().getMachOSection("__DWARF", "__debug_ranges",
 616                                  MCSectionMachO::S_ATTR_DEBUG,
 617                                  SectionKind::getMetadata());
 618   DwarfMacroInfoSection =
 619     getContext().getMachOSection("__DWARF", "__debug_macinfo",
 620                                  MCSectionMachO::S_ATTR_DEBUG,
 621                                  SectionKind::getMetadata());
 622   DwarfDebugInlineSection =
 623     getContext().getMachOSection("__DWARF", "__debug_inlined",
 624                                  MCSectionMachO::S_ATTR_DEBUG,
 625                                  SectionKind::getMetadata());
 626
 627   TLSExtraDataSection = TLSTLVSection;
 628 }
 629
 630 const MCSection *TargetLoweringObjectFileMachO::getEHFrameSection() const {
 631   return getContext().getMachOSection("__TEXT", "__eh_frame",
 632                                       MCSectionMachO::S_COALESCED |
 633                                       MCSectionMachO::S_ATTR_NO_TOC |
 634                                       MCSectionMachO::S_ATTR_STRIP_STATIC_SYMS |
 635                                       MCSectionMachO::S_ATTR_LIVE_SUPPORT,
 636                                       SectionKind::getReadOnly());
 637 }
 638
 639 const MCSection *TargetLoweringObjectFileMachO::
 640 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
 641                          Mangler *Mang, const TargetMachine &TM) const {
 642   // Parse the section specifier and create it if valid.
 643   StringRef Segment, Section;
 644   unsigned TAA = 0, StubSize = 0;
 645   bool TAAParsed;
 646   std::string ErrorCode =
 647     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
 648                                           TAA, TAAParsed, StubSize);
 649   if (!ErrorCode.empty()) {
 650     // If invalid, report the error with report_fatal_error.
 651     report_fatal_error("Global variable '" + GV->getNameStr() +
 652                       "' has an invalid section specifier '" + GV->getSection()+
 653                       "': " + ErrorCode + ".");
 654     // Fall back to dropping it into the data section.
 655     return DataSection;
 656   }
 657
 658   // Get the section.
 659   const MCSectionMachO *S =
 660     getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
 661
 662   // If TAA wasn't set by ParseSectionSpecifier() above,
 663   // use the value returned by getMachOSection() as a default.
 664   if (!TAAParsed)
 665     TAA = S->getTypeAndAttributes();
 666
 667   // Okay, now that we got the section, verify that the TAA & StubSize agree.
 668   // If the user declared multiple globals with different section flags, we need
 669   // to reject it here.
 670   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
 671     // If invalid, report the error with report_fatal_error.
 672     report_fatal_error("Global variable '" + GV->getNameStr() +
 673                       "' section type or attributes does not match previous"
 674                       " section specifier");
 675   }
 676
 677   return S;
 678 }
 679
 680 const MCSection *TargetLoweringObjectFileMachO::
 681 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
 682                        Mangler *Mang, const TargetMachine &TM) const {
 683
 684   // Handle thread local data.
 685   if (Kind.isThreadBSS()) return TLSBSSSection;
 686   if (Kind.isThreadData()) return TLSDataSection;
 687
 688   if (Kind.isText())
 689     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
 690
 691   // If this is weak/linkonce, put this in a coalescable section, either in text
 692   // or data depending on if it is writable.
 693   if (GV->isWeakForLinker()) {
 694     if (Kind.isReadOnly())
 695       return ConstTextCoalSection;
 696     return DataCoalSection;
 697   }
 698
 699   // FIXME: Alignment check should be handled by section classifier.
 700   if (Kind.isMergeable1ByteCString() &&
 701       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
 702     return CStringSection;
 703
 704   // Do not put 16-bit arrays in the UString section if they have an
 705   // externally visible label, this runs into issues with certain linker
 706   // versions.
 707   if (Kind.isMergeable2ByteCString() && !GV->hasExternalLinkage() &&
 708       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
 709     return UStringSection;
 710
 711   if (Kind.isMergeableConst()) {
 712     if (Kind.isMergeableConst4())
 713       return FourByteConstantSection;
 714     if (Kind.isMergeableConst8())
 715       return EightByteConstantSection;
 716     if (Kind.isMergeableConst16() && SixteenByteConstantSection)
 717       return SixteenByteConstantSection;
 718   }
 719
 720   // Otherwise, if it is readonly, but not something we can specially optimize,
 721   // just drop it in .const.
 722   if (Kind.isReadOnly())
 723     return ReadOnlySection;
 724
 725   // If this is marked const, put it into a const section.  But if the dynamic
 726   // linker needs to write to it, put it in the data segment.
 727   if (Kind.isReadOnlyWithRel())
 728     return ConstDataSection;
 729
 730   // Put zero initialized globals with strong external linkage in the
 731   // DATA, __common section with the .zerofill directive.
 732   if (Kind.isBSSExtern())
 733     return DataCommonSection;
 734
 735   // Put zero initialized globals with local linkage in __DATA,__bss directive
 736   // with the .zerofill directive (aka .lcomm).
 737   if (Kind.isBSSLocal())
 738     return DataBSSSection;
 739
 740   // Otherwise, just drop the variable in the normal data section.
 741   return DataSection;
 742 }
 743
 744 const MCSection *
 745 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
 746   // If this constant requires a relocation, we have to put it in the data
 747   // segment, not in the text segment.
 748   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
 749     return ConstDataSection;
 750
 751   if (Kind.isMergeableConst4())
 752     return FourByteConstantSection;
 753   if (Kind.isMergeableConst8())
 754     return EightByteConstantSection;
 755   if (Kind.isMergeableConst16() && SixteenByteConstantSection)
 756     return SixteenByteConstantSection;
 757   return ReadOnlySection;  // .const
 758 }
 759
 760 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
 761 /// not to emit the UsedDirective for some symbols in llvm.used.
 762 // FIXME: REMOVE this (rdar://7071300)
 763 bool TargetLoweringObjectFileMachO::
 764 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
 765   /// On Darwin, internally linked data beginning with "L" or "l" does not have
 766   /// the directive emitted (this occurs in ObjC metadata).
 767   if (!GV) return false;
 768
 769   // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
 770   if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
 771     // FIXME: ObjC metadata is currently emitted as internal symbols that have
 772     // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
 773     // this horrible hack can go away.
 774     MCSymbol *Sym = Mang->getSymbol(GV);
 775     if (Sym->getName()[0] == 'L' || Sym->getName()[0] == 'l')
 776       return false;
 777   }
 778
 779   return true;
 780 }
 781
 782 const MCExpr *TargetLoweringObjectFileMachO::
 783 getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
 784                                MachineModuleInfo *MMI, unsigned Encoding,
 785                                MCStreamer &Streamer) const {
 786   // The mach-o version of this method defaults to returning a stub reference.
 787
 788   if (Encoding & DW_EH_PE_indirect) {
 789     MachineModuleInfoMachO &MachOMMI =
 790       MMI->getObjFileInfo<MachineModuleInfoMachO>();
 791
 792     SmallString<128> Name;
 793     Mang->getNameWithPrefix(Name, GV, true);
 794     Name += "$non_lazy_ptr";
 795
 796     // Add information about the stub reference to MachOMMI so that the stub
 797     // gets emitted by the asmprinter.
 798     MCSymbol *SSym = getContext().GetOrCreateSymbol(Name.str());
 799     MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
 800     if (StubSym.getPointer() == 0) {
 801       MCSymbol *Sym = Mang->getSymbol(GV);
 802       StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
 803     }
 804
 805     return TargetLoweringObjectFile::
 806       getExprForDwarfReference(SSym, Mang, MMI,
 807                                Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
 808   }
 809
 810   return TargetLoweringObjectFile::
 811     getExprForDwarfGlobalReference(GV, Mang, MMI, Encoding, Streamer);
 812 }
 813
 814 unsigned TargetLoweringObjectFileMachO::getPersonalityEncoding() const {
 815   return DW_EH_PE_indirect | DW_EH_PE_pcrel | DW_EH_PE_sdata4;
 816 }
 817
 818 unsigned TargetLoweringObjectFileMachO::getLSDAEncoding() const {
 819   return DW_EH_PE_pcrel;
 820 }
 821
 822 unsigned TargetLoweringObjectFileMachO::getFDEEncoding() const {
 823   return DW_EH_PE_pcrel;
 824 }
 825
 826 unsigned TargetLoweringObjectFileMachO::getTTypeEncoding() const {
 827   return DW_EH_PE_indirect | DW_EH_PE_pcrel | DW_EH_PE_sdata4;
 828 }
 829
 830 //===----------------------------------------------------------------------===//
 831 //                                  COFF
 832 //===----------------------------------------------------------------------===//
 833
 834 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
 835                                               const TargetMachine &TM) {
 836   TargetLoweringObjectFile::Initialize(Ctx, TM);
 837   TextSection =
 838     getContext().getCOFFSection(".text",
 839                                 COFF::IMAGE_SCN_CNT_CODE |
 840                                 COFF::IMAGE_SCN_MEM_EXECUTE |
 841                                 COFF::IMAGE_SCN_MEM_READ,
 842                                 SectionKind::getText());
 843   DataSection =
 844     getContext().getCOFFSection(".data",
 845                                 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
 846                                 COFF::IMAGE_SCN_MEM_READ |
 847                                 COFF::IMAGE_SCN_MEM_WRITE,
 848                                 SectionKind::getDataRel());
 849   ReadOnlySection =
 850     getContext().getCOFFSection(".rdata",
 851                                 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
 852                                 COFF::IMAGE_SCN_MEM_READ,
 853                                 SectionKind::getReadOnly());
 854   StaticCtorSection =
 855     getContext().getCOFFSection(".ctors",
 856                                 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
 857                                 COFF::IMAGE_SCN_MEM_READ |
 858                                 COFF::IMAGE_SCN_MEM_WRITE,
 859                                 SectionKind::getDataRel());
 860   StaticDtorSection =
 861     getContext().getCOFFSection(".dtors",
 862                                 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
 863                                 COFF::IMAGE_SCN_MEM_READ |
 864                                 COFF::IMAGE_SCN_MEM_WRITE,
 865                                 SectionKind::getDataRel());
 866
 867   // FIXME: We're emitting LSDA info into a readonly section on COFF, even
 868   // though it contains relocatable pointers.  In PIC mode, this is probably a
 869   // big runtime hit for C++ apps.  Either the contents of the LSDA need to be
 870   // adjusted or this should be a data section.
 871   LSDASection =
 872     getContext().getCOFFSection(".gcc_except_table",
 873                                 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
 874                                 COFF::IMAGE_SCN_MEM_READ,
 875                                 SectionKind::getReadOnly());
 876   // Debug info.
 877   DwarfAbbrevSection =
 878     getContext().getCOFFSection(".debug_abbrev",
 879                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
 880                                 COFF::IMAGE_SCN_MEM_READ,
 881                                 SectionKind::getMetadata());
 882   DwarfInfoSection =
 883     getContext().getCOFFSection(".debug_info",
 884                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
 885                                 COFF::IMAGE_SCN_MEM_READ,
 886                                 SectionKind::getMetadata());
 887   DwarfLineSection =
 888     getContext().getCOFFSection(".debug_line",
 889                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
 890                                 COFF::IMAGE_SCN_MEM_READ,
 891                                 SectionKind::getMetadata());
 892   DwarfFrameSection =
 893     getContext().getCOFFSection(".debug_frame",
 894                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
 895                                 COFF::IMAGE_SCN_MEM_READ,
 896                                 SectionKind::getMetadata());
 897   DwarfPubNamesSection =
 898     getContext().getCOFFSection(".debug_pubnames",
 899                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
 900                                 COFF::IMAGE_SCN_MEM_READ,
 901                                 SectionKind::getMetadata());
 902   DwarfPubTypesSection =
 903     getContext().getCOFFSection(".debug_pubtypes",
 904                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
 905                                 COFF::IMAGE_SCN_MEM_READ,
 906                                 SectionKind::getMetadata());
 907   DwarfStrSection =
 908     getContext().getCOFFSection(".debug_str",
 909                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
 910                                 COFF::IMAGE_SCN_MEM_READ,
 911                                 SectionKind::getMetadata());
 912   DwarfLocSection =
 913     getContext().getCOFFSection(".debug_loc",
 914                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
 915                                 COFF::IMAGE_SCN_MEM_READ,
 916                                 SectionKind::getMetadata());
 917   DwarfARangesSection =
 918     getContext().getCOFFSection(".debug_aranges",
 919                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
 920                                 COFF::IMAGE_SCN_MEM_READ,
 921                                 SectionKind::getMetadata());
 922   DwarfRangesSection =
 923     getContext().getCOFFSection(".debug_ranges",
 924                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
 925                                 COFF::IMAGE_SCN_MEM_READ,
 926                                 SectionKind::getMetadata());
 927   DwarfMacroInfoSection =
 928     getContext().getCOFFSection(".debug_macinfo",
 929                                 COFF::IMAGE_SCN_MEM_DISCARDABLE |
 930                                 COFF::IMAGE_SCN_MEM_READ,
 931                                 SectionKind::getMetadata());
 932
 933   DrectveSection =
 934     getContext().getCOFFSection(".drectve",
 935                                 COFF::IMAGE_SCN_LNK_INFO,
 936                                 SectionKind::getMetadata());
 937 }
 938
 939 const MCSection *TargetLoweringObjectFileCOFF::getEHFrameSection() const {
 940   return getContext().getCOFFSection(".eh_frame",
 941                                      COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
 942                                      COFF::IMAGE_SCN_MEM_READ |
 943                                      COFF::IMAGE_SCN_MEM_WRITE,
 944                                      SectionKind::getDataRel());
 945 }
 946
 947
 948 static unsigned
 949 getCOFFSectionFlags(SectionKind K) {
 950   unsigned Flags = 0;
 951
 952   if (K.isMetadata())
 953     Flags |=
 954       COFF::IMAGE_SCN_MEM_DISCARDABLE;
 955   else if (K.isText())
 956     Flags |=
 957       COFF::IMAGE_SCN_MEM_EXECUTE |
 958       COFF::IMAGE_SCN_MEM_READ |
 959       COFF::IMAGE_SCN_CNT_CODE;
 960   else if (K.isBSS ())
 961     Flags |=
 962       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
 963       COFF::IMAGE_SCN_MEM_READ |
 964       COFF::IMAGE_SCN_MEM_WRITE;
 965   else if (K.isReadOnly())
 966     Flags |=
 967       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
 968       COFF::IMAGE_SCN_MEM_READ;
 969   else if (K.isWriteable())
 970     Flags |=
 971       COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
 972       COFF::IMAGE_SCN_MEM_READ |
 973       COFF::IMAGE_SCN_MEM_WRITE;
 974
 975   return Flags;
 976 }
 977
 978 const MCSection *TargetLoweringObjectFileCOFF::
 979 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
 980                          Mangler *Mang, const TargetMachine &TM) const {
 981   return getContext().getCOFFSection(GV->getSection(),
 982                                      getCOFFSectionFlags(Kind),
 983                                      Kind);
 984 }
 985
 986 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
 987   if (Kind.isText())
 988     return ".text$";
 989   if (Kind.isBSS ())
 990     return ".bss$";
 991   if (Kind.isWriteable())
 992     return ".data$";
 993   return ".rdata$";
 994 }
 995
 996
 997 const MCSection *TargetLoweringObjectFileCOFF::
 998 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
 999                        Mangler *Mang, const TargetMachine &TM) const {
1000   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
1001
1002   // If this global is linkonce/weak and the target handles this by emitting it
1003   // into a 'uniqued' section name, create and return the section now.
1004   if (GV->isWeakForLinker()) {
1005     const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
1006     SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
1007     MCSymbol *Sym = Mang->getSymbol(GV);
1008     Name.append(Sym->getName().begin() + 1, Sym->getName().end());
1009
1010     unsigned Characteristics = getCOFFSectionFlags(Kind);
1011
1012     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1013
1014     return getContext().getCOFFSection(Name.str(), Characteristics,
1015                           COFF::IMAGE_COMDAT_SELECT_ANY, Kind);
1016   }
1017
1018   if (Kind.isText())
1019     return getTextSection();
1020
1021   return getDataSection();
1022 }
1023