lib/Target/TargetLoweringObjectFile.cpp

   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/Function.h"
  19 #include "llvm/GlobalVariable.h"
  20 #include "llvm/MC/MCContext.h"
  21 #include "llvm/MC/MCSectionMachO.h"
  22 #include "llvm/MC/MCSectionELF.h"
  23 #include "llvm/Target/TargetData.h"
  24 #include "llvm/Target/TargetMachine.h"
  25 #include "llvm/Target/TargetOptions.h"
  26 #include "llvm/Support/Mangler.h"
  27 #include "llvm/ADT/SmallString.h"
  28 #include "llvm/ADT/StringExtras.h"
  29 using namespace llvm;
  30
  31 //===----------------------------------------------------------------------===//
  32 //                              Generic Code
  33 //===----------------------------------------------------------------------===//
  34
  35 TargetLoweringObjectFile::TargetLoweringObjectFile() : Ctx(0) {
  36   TextSection = 0;
  37   DataSection = 0;
  38   BSSSection = 0;
  39   ReadOnlySection = 0;
  40   StaticCtorSection = 0;
  41   StaticDtorSection = 0;
  42   LSDASection = 0;
  43   EHFrameSection = 0;
  44
  45   DwarfAbbrevSection = 0;
  46   DwarfInfoSection = 0;
  47   DwarfLineSection = 0;
  48   DwarfFrameSection = 0;
  49   DwarfPubNamesSection = 0;
  50   DwarfPubTypesSection = 0;
  51   DwarfDebugInlineSection = 0;
  52   DwarfStrSection = 0;
  53   DwarfLocSection = 0;
  54   DwarfARangesSection = 0;
  55   DwarfRangesSection = 0;
  56   DwarfMacroInfoSection = 0;
  57 }
  58
  59 TargetLoweringObjectFile::~TargetLoweringObjectFile() {
  60 }
  61
  62 static bool isSuitableForBSS(const GlobalVariable *GV) {
  63   Constant *C = GV->getInitializer();
  64
  65   // Must have zero initializer.
  66   if (!C->isNullValue())
  67     return false;
  68
  69   // Leave constant zeros in readonly constant sections, so they can be shared.
  70   if (GV->isConstant())
  71     return false;
  72
  73   // If the global has an explicit section specified, don't put it in BSS.
  74   if (!GV->getSection().empty())
  75     return false;
  76
  77   // If -nozero-initialized-in-bss is specified, don't ever use BSS.
  78   if (NoZerosInBSS)
  79     return false;
  80
  81   // Otherwise, put it in BSS!
  82   return true;
  83 }
  84
  85 /// IsNullTerminatedString - Return true if the specified constant (which is
  86 /// known to have a type that is an array of 1/2/4 byte elements) ends with a
  87 /// nul value and contains no other nuls in it.
  88 static bool IsNullTerminatedString(const Constant *C) {
  89   const ArrayType *ATy = cast<ArrayType>(C->getType());
  90
  91   // First check: is we have constant array of i8 terminated with zero
  92   if (const ConstantArray *CVA = dyn_cast<ConstantArray>(C)) {
  93     if (ATy->getNumElements() == 0) return false;
  94
  95     ConstantInt *Null =
  96       dyn_cast<ConstantInt>(CVA->getOperand(ATy->getNumElements()-1));
  97     if (Null == 0 || Null->getZExtValue() != 0)
  98       return false; // Not null terminated.
  99
 100     // Verify that the null doesn't occur anywhere else in the string.
 101     for (unsigned i = 0, e = ATy->getNumElements()-1; i != e; ++i)
 102       // Reject constantexpr elements etc.
 103       if (!isa<ConstantInt>(CVA->getOperand(i)) ||
 104           CVA->getOperand(i) == Null)
 105         return false;
 106     return true;
 107   }
 108
 109   // Another possibility: [1 x i8] zeroinitializer
 110   if (isa<ConstantAggregateZero>(C))
 111     return ATy->getNumElements() == 1;
 112
 113   return false;
 114 }
 115
 116 /// getKindForGlobal - This is a top-level target-independent classifier for
 117 /// a global variable.  Given an global variable and information from TM, it
 118 /// classifies the global in a variety of ways that make various target
 119 /// implementations simpler.  The target implementation is free to ignore this
 120 /// extra info of course.
 121 SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalValue *GV,
 122                                                        const TargetMachine &TM){
 123   assert(!GV->isDeclaration() && !GV->hasAvailableExternallyLinkage() &&
 124          "Can only be used for global definitions");
 125
 126   Reloc::Model ReloModel = TM.getRelocationModel();
 127
 128   // Early exit - functions should be always in text sections.
 129   const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
 130   if (GVar == 0)
 131     return SectionKind::getText();
 132
 133   // Handle thread-local data first.
 134   if (GVar->isThreadLocal()) {
 135     if (isSuitableForBSS(GVar))
 136       return SectionKind::getThreadBSS();
 137     return SectionKind::getThreadData();
 138   }
 139
 140   // Variable can be easily put to BSS section.
 141   if (isSuitableForBSS(GVar))
 142     return SectionKind::getBSS();
 143
 144   Constant *C = GVar->getInitializer();
 145
 146   // If the global is marked constant, we can put it into a mergable section,
 147   // a mergable string section, or general .data if it contains relocations.
 148   if (GVar->isConstant()) {
 149     // If the initializer for the global contains something that requires a
 150     // relocation, then we may have to drop this into a wriable data section
 151     // even though it is marked const.
 152     switch (C->getRelocationInfo()) {
 153     default: llvm_unreachable("unknown relocation info kind");
 154     case Constant::NoRelocation:
 155       // If initializer is a null-terminated string, put it in a "cstring"
 156       // section of the right width.
 157       if (const ArrayType *ATy = dyn_cast<ArrayType>(C->getType())) {
 158         if (const IntegerType *ITy =
 159               dyn_cast<IntegerType>(ATy->getElementType())) {
 160           if ((ITy->getBitWidth() == 8 || ITy->getBitWidth() == 16 ||
 161                ITy->getBitWidth() == 32) &&
 162               IsNullTerminatedString(C)) {
 163             if (ITy->getBitWidth() == 8)
 164               return SectionKind::getMergeable1ByteCString();
 165             if (ITy->getBitWidth() == 16)
 166               return SectionKind::getMergeable2ByteCString();
 167
 168             assert(ITy->getBitWidth() == 32 && "Unknown width");
 169             return SectionKind::getMergeable4ByteCString();
 170           }
 171         }
 172       }
 173
 174       // Otherwise, just drop it into a mergable constant section.  If we have
 175       // a section for this size, use it, otherwise use the arbitrary sized
 176       // mergable section.
 177       switch (TM.getTargetData()->getTypeAllocSize(C->getType())) {
 178       case 4:  return SectionKind::getMergeableConst4();
 179       case 8:  return SectionKind::getMergeableConst8();
 180       case 16: return SectionKind::getMergeableConst16();
 181       default: return SectionKind::getMergeableConst();
 182       }
 183
 184     case Constant::LocalRelocation:
 185       // In static relocation model, the linker will resolve all addresses, so
 186       // the relocation entries will actually be constants by the time the app
 187       // starts up.  However, we can't put this into a mergable section, because
 188       // the linker doesn't take relocations into consideration when it tries to
 189       // merge entries in the section.
 190       if (ReloModel == Reloc::Static)
 191         return SectionKind::getReadOnly();
 192
 193       // Otherwise, the dynamic linker needs to fix it up, put it in the
 194       // writable data.rel.local section.
 195       return SectionKind::getReadOnlyWithRelLocal();
 196
 197     case Constant::GlobalRelocations:
 198       // In static relocation model, the linker will resolve all addresses, so
 199       // the relocation entries will actually be constants by the time the app
 200       // starts up.  However, we can't put this into a mergable section, because
 201       // the linker doesn't take relocations into consideration when it tries to
 202       // merge entries in the section.
 203       if (ReloModel == Reloc::Static)
 204         return SectionKind::getReadOnly();
 205
 206       // Otherwise, the dynamic linker needs to fix it up, put it in the
 207       // writable data.rel section.
 208       return SectionKind::getReadOnlyWithRel();
 209     }
 210   }
 211
 212   // Okay, this isn't a constant.  If the initializer for the global is going
 213   // to require a runtime relocation by the dynamic linker, put it into a more
 214   // specific section to improve startup time of the app.  This coalesces these
 215   // globals together onto fewer pages, improving the locality of the dynamic
 216   // linker.
 217   if (ReloModel == Reloc::Static)
 218     return SectionKind::getDataNoRel();
 219
 220   switch (C->getRelocationInfo()) {
 221   default: llvm_unreachable("unknown relocation info kind");
 222   case Constant::NoRelocation:
 223     return SectionKind::getDataNoRel();
 224   case Constant::LocalRelocation:
 225     return SectionKind::getDataRelLocal();
 226   case Constant::GlobalRelocations:
 227     return SectionKind::getDataRel();
 228   }
 229 }
 230
 231 /// SectionForGlobal - This method computes the appropriate section to emit
 232 /// the specified global variable or function definition.  This should not
 233 /// be passed external (or available externally) globals.
 234 const MCSection *TargetLoweringObjectFile::
 235 SectionForGlobal(const GlobalValue *GV, SectionKind Kind, Mangler *Mang,
 236                  const TargetMachine &TM) const {
 237   // Select section name.
 238   if (GV->hasSection())
 239     return getExplicitSectionGlobal(GV, Kind, Mang, TM);
 240
 241
 242   // Use default section depending on the 'type' of global
 243   return SelectSectionForGlobal(GV, Kind, Mang, TM);
 244 }
 245
 246
 247 // Lame default implementation. Calculate the section name for global.
 248 const MCSection *
 249 TargetLoweringObjectFile::SelectSectionForGlobal(const GlobalValue *GV,
 250                                                  SectionKind Kind,
 251                                                  Mangler *Mang,
 252                                                  const TargetMachine &TM) const{
 253   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
 254
 255   if (Kind.isText())
 256     return getTextSection();
 257
 258   if (Kind.isBSS() && BSSSection != 0)
 259     return BSSSection;
 260
 261   if (Kind.isReadOnly() && ReadOnlySection != 0)
 262     return ReadOnlySection;
 263
 264   return getDataSection();
 265 }
 266
 267 /// getSectionForConstant - Given a mergable constant with the
 268 /// specified size and relocation information, return a section that it
 269 /// should be placed in.
 270 const MCSection *
 271 TargetLoweringObjectFile::getSectionForConstant(SectionKind Kind) const {
 272   if (Kind.isReadOnly() && ReadOnlySection != 0)
 273     return ReadOnlySection;
 274
 275   return DataSection;
 276 }
 277
 278
 279
 280 //===----------------------------------------------------------------------===//
 281 //                                  ELF
 282 //===----------------------------------------------------------------------===//
 283 typedef StringMap<const MCSectionELF*> ELFUniqueMapTy;
 284
 285 TargetLoweringObjectFileELF::~TargetLoweringObjectFileELF() {
 286   // If we have the section uniquing map, free it.
 287   delete (ELFUniqueMapTy*)UniquingMap;
 288 }
 289
 290 const MCSection *TargetLoweringObjectFileELF::
 291 getELFSection(StringRef Section, unsigned Type, unsigned Flags,
 292               SectionKind Kind, bool IsExplicit) const {
 293   if (UniquingMap == 0)
 294     UniquingMap = new ELFUniqueMapTy();
 295   ELFUniqueMapTy &Map = *(ELFUniqueMapTy*)UniquingMap;
 296
 297   // Do the lookup, if we have a hit, return it.
 298   const MCSectionELF *&Entry = Map[Section];
 299   if (Entry) return Entry;
 300
 301   return Entry = MCSectionELF::Create(Section, Type, Flags, Kind, IsExplicit,
 302                                       getContext());
 303 }
 304
 305 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
 306                                              const TargetMachine &TM) {
 307   TargetLoweringObjectFile::Initialize(Ctx, TM);
 308
 309   BSSSection =
 310     getELFSection(".bss", MCSectionELF::SHT_NOBITS,
 311                   MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
 312                   SectionKind::getBSS());
 313
 314   TextSection =
 315     getELFSection(".text", MCSectionELF::SHT_PROGBITS,
 316                   MCSectionELF::SHF_EXECINSTR | MCSectionELF::SHF_ALLOC,
 317                   SectionKind::getText());
 318
 319   DataSection =
 320     getELFSection(".data", MCSectionELF::SHT_PROGBITS,
 321                   MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
 322                   SectionKind::getDataRel());
 323
 324   ReadOnlySection =
 325     getELFSection(".rodata", MCSectionELF::SHT_PROGBITS,
 326                   MCSectionELF::SHF_ALLOC,
 327                   SectionKind::getReadOnly());
 328
 329   TLSDataSection =
 330     getELFSection(".tdata", MCSectionELF::SHT_PROGBITS,
 331                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
 332                   MCSectionELF::SHF_WRITE, SectionKind::getThreadData());
 333
 334   TLSBSSSection =
 335     getELFSection(".tbss", MCSectionELF::SHT_NOBITS,
 336                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
 337                   MCSectionELF::SHF_WRITE, SectionKind::getThreadBSS());
 338
 339   DataRelSection =
 340     getELFSection(".data.rel", MCSectionELF::SHT_PROGBITS,
 341                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
 342                   SectionKind::getDataRel());
 343
 344   DataRelLocalSection =
 345     getELFSection(".data.rel.local", MCSectionELF::SHT_PROGBITS,
 346                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
 347                   SectionKind::getDataRelLocal());
 348
 349   DataRelROSection =
 350     getELFSection(".data.rel.ro", MCSectionELF::SHT_PROGBITS,
 351                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
 352                   SectionKind::getReadOnlyWithRel());
 353
 354   DataRelROLocalSection =
 355     getELFSection(".data.rel.ro.local", MCSectionELF::SHT_PROGBITS,
 356                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
 357                   SectionKind::getReadOnlyWithRelLocal());
 358
 359   MergeableConst4Section =
 360     getELFSection(".rodata.cst4", MCSectionELF::SHT_PROGBITS,
 361                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
 362                   SectionKind::getMergeableConst4());
 363
 364   MergeableConst8Section =
 365     getELFSection(".rodata.cst8", MCSectionELF::SHT_PROGBITS,
 366                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
 367                   SectionKind::getMergeableConst8());
 368
 369   MergeableConst16Section =
 370     getELFSection(".rodata.cst16", MCSectionELF::SHT_PROGBITS,
 371                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
 372                   SectionKind::getMergeableConst16());
 373
 374   StaticCtorSection =
 375     getELFSection(".ctors", MCSectionELF::SHT_PROGBITS,
 376                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
 377                   SectionKind::getDataRel());
 378
 379   StaticDtorSection =
 380     getELFSection(".dtors", MCSectionELF::SHT_PROGBITS,
 381                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
 382                   SectionKind::getDataRel());
 383
 384   // Exception Handling Sections.
 385
 386   // FIXME: We're emitting LSDA info into a readonly section on ELF, even though
 387   // it contains relocatable pointers.  In PIC mode, this is probably a big
 388   // runtime hit for C++ apps.  Either the contents of the LSDA need to be
 389   // adjusted or this should be a data section.
 390   LSDASection =
 391     getELFSection(".gcc_except_table", MCSectionELF::SHT_PROGBITS,
 392                   MCSectionELF::SHF_ALLOC, SectionKind::getReadOnly());
 393   EHFrameSection =
 394     getELFSection(".eh_frame", MCSectionELF::SHT_PROGBITS,
 395                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
 396                   SectionKind::getDataRel());
 397
 398   // Debug Info Sections.
 399   DwarfAbbrevSection =
 400     getELFSection(".debug_abbrev", MCSectionELF::SHT_PROGBITS, 0,
 401                   SectionKind::getMetadata());
 402   DwarfInfoSection =
 403     getELFSection(".debug_info", MCSectionELF::SHT_PROGBITS, 0,
 404                   SectionKind::getMetadata());
 405   DwarfLineSection =
 406     getELFSection(".debug_line", MCSectionELF::SHT_PROGBITS, 0,
 407                   SectionKind::getMetadata());
 408   DwarfFrameSection =
 409     getELFSection(".debug_frame", MCSectionELF::SHT_PROGBITS, 0,
 410                   SectionKind::getMetadata());
 411   DwarfPubNamesSection =
 412     getELFSection(".debug_pubnames", MCSectionELF::SHT_PROGBITS, 0,
 413                   SectionKind::getMetadata());
 414   DwarfPubTypesSection =
 415     getELFSection(".debug_pubtypes", MCSectionELF::SHT_PROGBITS, 0,
 416                   SectionKind::getMetadata());
 417   DwarfStrSection =
 418     getELFSection(".debug_str", MCSectionELF::SHT_PROGBITS, 0,
 419                   SectionKind::getMetadata());
 420   DwarfLocSection =
 421     getELFSection(".debug_loc", MCSectionELF::SHT_PROGBITS, 0,
 422                   SectionKind::getMetadata());
 423   DwarfARangesSection =
 424     getELFSection(".debug_aranges", MCSectionELF::SHT_PROGBITS, 0,
 425                   SectionKind::getMetadata());
 426   DwarfRangesSection =
 427     getELFSection(".debug_ranges", MCSectionELF::SHT_PROGBITS, 0,
 428                   SectionKind::getMetadata());
 429   DwarfMacroInfoSection =
 430     getELFSection(".debug_macinfo", MCSectionELF::SHT_PROGBITS, 0,
 431                   SectionKind::getMetadata());
 432 }
 433
 434
 435 static SectionKind
 436 getELFKindForNamedSection(const char *Name, SectionKind K) {
 437   if (Name[0] != '.') return K;
 438
 439   // Some lame default implementation based on some magic section names.
 440   if (strncmp(Name, ".gnu.linkonce.b.", 16) == 0 ||
 441       strncmp(Name, ".llvm.linkonce.b.", 17) == 0 ||
 442       strncmp(Name, ".gnu.linkonce.sb.", 17) == 0 ||
 443       strncmp(Name, ".llvm.linkonce.sb.", 18) == 0)
 444     return SectionKind::getBSS();
 445
 446   if (strcmp(Name, ".tdata") == 0 ||
 447       strncmp(Name, ".tdata.", 7) == 0 ||
 448       strncmp(Name, ".gnu.linkonce.td.", 17) == 0 ||
 449       strncmp(Name, ".llvm.linkonce.td.", 18) == 0)
 450     return SectionKind::getThreadData();
 451
 452   if (strcmp(Name, ".tbss") == 0 ||
 453       strncmp(Name, ".tbss.", 6) == 0 ||
 454       strncmp(Name, ".gnu.linkonce.tb.", 17) == 0 ||
 455       strncmp(Name, ".llvm.linkonce.tb.", 18) == 0)
 456     return SectionKind::getThreadBSS();
 457
 458   return K;
 459 }
 460
 461
 462 static unsigned
 463 getELFSectionType(const char *Name, SectionKind K) {
 464
 465   if (strcmp(Name, ".init_array") == 0)
 466     return MCSectionELF::SHT_INIT_ARRAY;
 467
 468   if (strcmp(Name, ".fini_array") == 0)
 469     return MCSectionELF::SHT_FINI_ARRAY;
 470
 471   if (strcmp(Name, ".preinit_array") == 0)
 472     return MCSectionELF::SHT_PREINIT_ARRAY;
 473
 474   if (K.isBSS() || K.isThreadBSS())
 475     return MCSectionELF::SHT_NOBITS;
 476
 477   return MCSectionELF::SHT_PROGBITS;
 478 }
 479
 480
 481 static unsigned
 482 getELFSectionFlags(SectionKind K) {
 483   unsigned Flags = 0;
 484
 485   if (!K.isMetadata())
 486     Flags |= MCSectionELF::SHF_ALLOC;
 487
 488   if (K.isWriteable())
 489     Flags |= MCSectionELF::SHF_WRITE;
 490
 491   if (K.isThreadLocal())
 492     Flags |= MCSectionELF::SHF_TLS;
 493
 494   // K.isMergeableConst() is left out to honour PR4650
 495   if (K.isMergeableCString() || K.isMergeableConst4() ||
 496       K.isMergeableConst8() || K.isMergeableConst16())
 497     Flags |= MCSectionELF::SHF_MERGE;
 498
 499   if (K.isMergeableCString())
 500     Flags |= MCSectionELF::SHF_STRINGS;
 501
 502   return Flags;
 503 }
 504
 505
 506 const MCSection *TargetLoweringObjectFileELF::
 507 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
 508                          Mangler *Mang, const TargetMachine &TM) const {
 509   const char *SectionName = GV->getSection().c_str();
 510
 511   // Infer section flags from the section name if we can.
 512   Kind = getELFKindForNamedSection(SectionName, Kind);
 513
 514   return getELFSection(SectionName,
 515                        getELFSectionType(SectionName, Kind),
 516                        getELFSectionFlags(Kind), Kind, true);
 517 }
 518
 519 static const char *getSectionPrefixForUniqueGlobal(SectionKind Kind) {
 520   if (Kind.isText())                 return ".gnu.linkonce.t.";
 521   if (Kind.isReadOnly())             return ".gnu.linkonce.r.";
 522
 523   if (Kind.isThreadData())           return ".gnu.linkonce.td.";
 524   if (Kind.isThreadBSS())            return ".gnu.linkonce.tb.";
 525
 526   if (Kind.isBSS())                  return ".gnu.linkonce.b.";
 527   if (Kind.isDataNoRel())            return ".gnu.linkonce.d.";
 528   if (Kind.isDataRelLocal())         return ".gnu.linkonce.d.rel.local.";
 529   if (Kind.isDataRel())              return ".gnu.linkonce.d.rel.";
 530   if (Kind.isReadOnlyWithRelLocal()) return ".gnu.linkonce.d.rel.ro.local.";
 531
 532   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
 533   return ".gnu.linkonce.d.rel.ro.";
 534 }
 535
 536 const MCSection *TargetLoweringObjectFileELF::
 537 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
 538                        Mangler *Mang, const TargetMachine &TM) const {
 539
 540   // If this global is linkonce/weak and the target handles this by emitting it
 541   // into a 'uniqued' section name, create and return the section now.
 542   if (GV->isWeakForLinker()) {
 543     const char *Prefix = getSectionPrefixForUniqueGlobal(Kind);
 544     std::string Name = Mang->makeNameProper(GV->getNameStr());
 545
 546     return getELFSection((Prefix+Name).c_str(),
 547                          getELFSectionType((Prefix+Name).c_str(), Kind),
 548                          getELFSectionFlags(Kind),
 549                          Kind);
 550   }
 551
 552   if (Kind.isText()) return TextSection;
 553
 554   if (Kind.isMergeable1ByteCString() ||
 555       Kind.isMergeable2ByteCString() ||
 556       Kind.isMergeable4ByteCString()) {
 557
 558     // We also need alignment here.
 559     // FIXME: this is getting the alignment of the character, not the
 560     // alignment of the global!
 561     unsigned Align =
 562       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV));
 563
 564     const char *SizeSpec = ".rodata.str1.";
 565     if (Kind.isMergeable2ByteCString())
 566       SizeSpec = ".rodata.str2.";
 567     else if (Kind.isMergeable4ByteCString())
 568       SizeSpec = ".rodata.str4.";
 569     else
 570       assert(Kind.isMergeable1ByteCString() && "unknown string width");
 571
 572
 573     std::string Name = SizeSpec + utostr(Align);
 574     return getELFSection(Name.c_str(), MCSectionELF::SHT_PROGBITS,
 575                          MCSectionELF::SHF_ALLOC |
 576                          MCSectionELF::SHF_MERGE |
 577                          MCSectionELF::SHF_STRINGS,
 578                          Kind);
 579   }
 580
 581   if (Kind.isMergeableConst()) {
 582     if (Kind.isMergeableConst4() && MergeableConst4Section)
 583       return MergeableConst4Section;
 584     if (Kind.isMergeableConst8() && MergeableConst8Section)
 585       return MergeableConst8Section;
 586     if (Kind.isMergeableConst16() && MergeableConst16Section)
 587       return MergeableConst16Section;
 588     return ReadOnlySection;  // .const
 589   }
 590
 591   if (Kind.isReadOnly())             return ReadOnlySection;
 592
 593   if (Kind.isThreadData())           return TLSDataSection;
 594   if (Kind.isThreadBSS())            return TLSBSSSection;
 595
 596   if (Kind.isBSS())                  return BSSSection;
 597
 598   if (Kind.isDataNoRel())            return DataSection;
 599   if (Kind.isDataRelLocal())         return DataRelLocalSection;
 600   if (Kind.isDataRel())              return DataRelSection;
 601   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
 602
 603   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
 604   return DataRelROSection;
 605 }
 606
 607 /// getSectionForConstant - Given a mergeable constant with the
 608 /// specified size and relocation information, return a section that it
 609 /// should be placed in.
 610 const MCSection *TargetLoweringObjectFileELF::
 611 getSectionForConstant(SectionKind Kind) const {
 612   if (Kind.isMergeableConst4())
 613     return MergeableConst4Section;
 614   if (Kind.isMergeableConst8())
 615     return MergeableConst8Section;
 616   if (Kind.isMergeableConst16())
 617     return MergeableConst16Section;
 618   if (Kind.isReadOnly())
 619     return ReadOnlySection;
 620
 621   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
 622   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
 623   return DataRelROSection;
 624 }
 625
 626 //===----------------------------------------------------------------------===//
 627 //                                 MachO
 628 //===----------------------------------------------------------------------===//
 629
 630 typedef StringMap<const MCSectionMachO*> MachOUniqueMapTy;
 631
 632 TargetLoweringObjectFileMachO::~TargetLoweringObjectFileMachO() {
 633   // If we have the MachO uniquing map, free it.
 634   delete (MachOUniqueMapTy*)UniquingMap;
 635 }
 636
 637
 638 const MCSectionMachO *TargetLoweringObjectFileMachO::
 639 getMachOSection(const StringRef &Segment, const StringRef &Section,
 640                 unsigned TypeAndAttributes,
 641                 unsigned Reserved2, SectionKind Kind) const {
 642   // We unique sections by their segment/section pair.  The returned section
 643   // may not have the same flags as the requested section, if so this should be
 644   // diagnosed by the client as an error.
 645
 646   // Create the map if it doesn't already exist.
 647   if (UniquingMap == 0)
 648     UniquingMap = new MachOUniqueMapTy();
 649   MachOUniqueMapTy &Map = *(MachOUniqueMapTy*)UniquingMap;
 650
 651   // Form the name to look up.
 652   SmallString<64> Name;
 653   Name.append(Segment.begin(), Segment.end());
 654   Name.push_back(',');
 655   Name.append(Section.begin(), Section.end());
 656
 657   // Do the lookup, if we have a hit, return it.
 658   const MCSectionMachO *&Entry = Map[StringRef(Name.data(), Name.size())];
 659   if (Entry) return Entry;
 660
 661   // Otherwise, return a new section.
 662   return Entry = MCSectionMachO::Create(Segment, Section, TypeAndAttributes,
 663                                         Reserved2, Kind, getContext());
 664 }
 665
 666
 667 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
 668                                                const TargetMachine &TM) {
 669   TargetLoweringObjectFile::Initialize(Ctx, TM);
 670
 671   TextSection // .text
 672     = getMachOSection("__TEXT", "__text",
 673                       MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
 674                       SectionKind::getText());
 675   DataSection // .data
 676     = getMachOSection("__DATA", "__data", 0, SectionKind::getDataRel());
 677
 678   CStringSection // .cstring
 679     = getMachOSection("__TEXT", "__cstring", MCSectionMachO::S_CSTRING_LITERALS,
 680                       SectionKind::getMergeable1ByteCString());
 681   UStringSection
 682     = getMachOSection("__TEXT","__ustring", 0,
 683                       SectionKind::getMergeable2ByteCString());
 684   FourByteConstantSection // .literal4
 685     = getMachOSection("__TEXT", "__literal4", MCSectionMachO::S_4BYTE_LITERALS,
 686                       SectionKind::getMergeableConst4());
 687   EightByteConstantSection // .literal8
 688     = getMachOSection("__TEXT", "__literal8", MCSectionMachO::S_8BYTE_LITERALS,
 689                       SectionKind::getMergeableConst8());
 690
 691   // ld_classic doesn't support .literal16 in 32-bit mode, and ld64 falls back
 692   // to using it in -static mode.
 693   SixteenByteConstantSection = 0;
 694   if (TM.getRelocationModel() != Reloc::Static &&
 695       TM.getTargetData()->getPointerSize() == 32)
 696     SixteenByteConstantSection =   // .literal16
 697       getMachOSection("__TEXT", "__literal16",MCSectionMachO::S_16BYTE_LITERALS,
 698                       SectionKind::getMergeableConst16());
 699
 700   ReadOnlySection  // .const
 701     = getMachOSection("__TEXT", "__const", 0, SectionKind::getReadOnly());
 702
 703   TextCoalSection
 704     = getMachOSection("__TEXT", "__textcoal_nt",
 705                       MCSectionMachO::S_COALESCED |
 706                       MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
 707                       SectionKind::getText());
 708   ConstTextCoalSection
 709     = getMachOSection("__TEXT", "__const_coal", MCSectionMachO::S_COALESCED,
 710                       SectionKind::getText());
 711   ConstDataCoalSection
 712     = getMachOSection("__DATA","__const_coal", MCSectionMachO::S_COALESCED,
 713                       SectionKind::getText());
 714   ConstDataSection  // .const_data
 715     = getMachOSection("__DATA", "__const", 0,
 716                       SectionKind::getReadOnlyWithRel());
 717   DataCoalSection
 718     = getMachOSection("__DATA","__datacoal_nt", MCSectionMachO::S_COALESCED,
 719                       SectionKind::getDataRel());
 720
 721
 722   LazySymbolPointerSection
 723     = getMachOSection("__DATA", "__la_symbol_ptr",
 724                       MCSectionMachO::S_LAZY_SYMBOL_POINTERS,
 725                       SectionKind::getMetadata());
 726   NonLazySymbolPointerSection
 727     = getMachOSection("__DATA", "__nl_symbol_ptr",
 728                       MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS,
 729                       SectionKind::getMetadata());
 730
 731   if (TM.getRelocationModel() == Reloc::Static) {
 732     StaticCtorSection
 733       = getMachOSection("__TEXT", "__constructor", 0,SectionKind::getDataRel());
 734     StaticDtorSection
 735       = getMachOSection("__TEXT", "__destructor", 0, SectionKind::getDataRel());
 736   } else {
 737     StaticCtorSection
 738       = getMachOSection("__DATA", "__mod_init_func",
 739                         MCSectionMachO::S_MOD_INIT_FUNC_POINTERS,
 740                         SectionKind::getDataRel());
 741     StaticDtorSection
 742       = getMachOSection("__DATA", "__mod_term_func",
 743                         MCSectionMachO::S_MOD_TERM_FUNC_POINTERS,
 744                         SectionKind::getDataRel());
 745   }
 746
 747   // Exception Handling.
 748   LSDASection = getMachOSection("__DATA", "__gcc_except_tab", 0,
 749                                 SectionKind::getDataRel());
 750   EHFrameSection =
 751     getMachOSection("__TEXT", "__eh_frame",
 752                     MCSectionMachO::S_COALESCED |
 753                     MCSectionMachO::S_ATTR_NO_TOC |
 754                     MCSectionMachO::S_ATTR_STRIP_STATIC_SYMS |
 755                     MCSectionMachO::S_ATTR_LIVE_SUPPORT,
 756                     SectionKind::getReadOnly());
 757
 758   // Debug Information.
 759   DwarfAbbrevSection =
 760     getMachOSection("__DWARF", "__debug_abbrev", MCSectionMachO::S_ATTR_DEBUG,
 761                     SectionKind::getMetadata());
 762   DwarfInfoSection =
 763     getMachOSection("__DWARF", "__debug_info", MCSectionMachO::S_ATTR_DEBUG,
 764                     SectionKind::getMetadata());
 765   DwarfLineSection =
 766     getMachOSection("__DWARF", "__debug_line", MCSectionMachO::S_ATTR_DEBUG,
 767                     SectionKind::getMetadata());
 768   DwarfFrameSection =
 769     getMachOSection("__DWARF", "__debug_frame", MCSectionMachO::S_ATTR_DEBUG,
 770                     SectionKind::getMetadata());
 771   DwarfPubNamesSection =
 772     getMachOSection("__DWARF", "__debug_pubnames", MCSectionMachO::S_ATTR_DEBUG,
 773                     SectionKind::getMetadata());
 774   DwarfPubTypesSection =
 775     getMachOSection("__DWARF", "__debug_pubtypes", MCSectionMachO::S_ATTR_DEBUG,
 776                     SectionKind::getMetadata());
 777   DwarfStrSection =
 778     getMachOSection("__DWARF", "__debug_str", MCSectionMachO::S_ATTR_DEBUG,
 779                     SectionKind::getMetadata());
 780   DwarfLocSection =
 781     getMachOSection("__DWARF", "__debug_loc", MCSectionMachO::S_ATTR_DEBUG,
 782                     SectionKind::getMetadata());
 783   DwarfARangesSection =
 784     getMachOSection("__DWARF", "__debug_aranges", MCSectionMachO::S_ATTR_DEBUG,
 785                     SectionKind::getMetadata());
 786   DwarfRangesSection =
 787     getMachOSection("__DWARF", "__debug_ranges", MCSectionMachO::S_ATTR_DEBUG,
 788                     SectionKind::getMetadata());
 789   DwarfMacroInfoSection =
 790     getMachOSection("__DWARF", "__debug_macinfo", MCSectionMachO::S_ATTR_DEBUG,
 791                     SectionKind::getMetadata());
 792   DwarfDebugInlineSection =
 793     getMachOSection("__DWARF", "__debug_inlined", MCSectionMachO::S_ATTR_DEBUG,
 794                     SectionKind::getMetadata());
 795 }
 796
 797 const MCSection *TargetLoweringObjectFileMachO::
 798 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
 799                          Mangler *Mang, const TargetMachine &TM) const {
 800   // Parse the section specifier and create it if valid.
 801   StringRef Segment, Section;
 802   unsigned TAA, StubSize;
 803   std::string ErrorCode =
 804     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
 805                                           TAA, StubSize);
 806   if (!ErrorCode.empty()) {
 807     // If invalid, report the error with llvm_report_error.
 808     llvm_report_error("Global variable '" + GV->getNameStr() +
 809                       "' has an invalid section specifier '" + GV->getSection()+
 810                       "': " + ErrorCode + ".");
 811     // Fall back to dropping it into the data section.
 812     return DataSection;
 813   }
 814
 815   // Get the section.
 816   const MCSectionMachO *S =
 817     getMachOSection(Segment, Section, TAA, StubSize, Kind);
 818
 819   // Okay, now that we got the section, verify that the TAA & StubSize agree.
 820   // If the user declared multiple globals with different section flags, we need
 821   // to reject it here.
 822   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
 823     // If invalid, report the error with llvm_report_error.
 824     llvm_report_error("Global variable '" + GV->getNameStr() +
 825                       "' section type or attributes does not match previous"
 826                       " section specifier");
 827   }
 828
 829   return S;
 830 }
 831
 832 const MCSection *TargetLoweringObjectFileMachO::
 833 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
 834                        Mangler *Mang, const TargetMachine &TM) const {
 835   assert(!Kind.isThreadLocal() && "Darwin doesn't support TLS");
 836
 837   if (Kind.isText())
 838     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
 839
 840   // If this is weak/linkonce, put this in a coalescable section, either in text
 841   // or data depending on if it is writable.
 842   if (GV->isWeakForLinker()) {
 843     if (Kind.isReadOnly())
 844       return ConstTextCoalSection;
 845     return DataCoalSection;
 846   }
 847
 848   // FIXME: Alignment check should be handled by section classifier.
 849   if (Kind.isMergeable1ByteCString() ||
 850       Kind.isMergeable2ByteCString()) {
 851     if (TM.getTargetData()->getPreferredAlignment(
 852                                               cast<GlobalVariable>(GV)) < 32) {
 853       if (Kind.isMergeable1ByteCString())
 854         return CStringSection;
 855       assert(Kind.isMergeable2ByteCString());
 856       return UStringSection;
 857     }
 858   }
 859
 860   if (Kind.isMergeableConst()) {
 861     if (Kind.isMergeableConst4())
 862       return FourByteConstantSection;
 863     if (Kind.isMergeableConst8())
 864       return EightByteConstantSection;
 865     if (Kind.isMergeableConst16() && SixteenByteConstantSection)
 866       return SixteenByteConstantSection;
 867   }
 868
 869   // Otherwise, if it is readonly, but not something we can specially optimize,
 870   // just drop it in .const.
 871   if (Kind.isReadOnly())
 872     return ReadOnlySection;
 873
 874   // If this is marked const, put it into a const section.  But if the dynamic
 875   // linker needs to write to it, put it in the data segment.
 876   if (Kind.isReadOnlyWithRel())
 877     return ConstDataSection;
 878
 879   // Otherwise, just drop the variable in the normal data section.
 880   return DataSection;
 881 }
 882
 883 const MCSection *
 884 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
 885   // If this constant requires a relocation, we have to put it in the data
 886   // segment, not in the text segment.
 887   if (Kind.isDataRel())
 888     return ConstDataSection;
 889
 890   if (Kind.isMergeableConst4())
 891     return FourByteConstantSection;
 892   if (Kind.isMergeableConst8())
 893     return EightByteConstantSection;
 894   if (Kind.isMergeableConst16() && SixteenByteConstantSection)
 895     return SixteenByteConstantSection;
 896   return ReadOnlySection;  // .const
 897 }
 898
 899 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
 900 /// not to emit the UsedDirective for some symbols in llvm.used.
 901 // FIXME: REMOVE this (rdar://7071300)
 902 bool TargetLoweringObjectFileMachO::
 903 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
 904   /// On Darwin, internally linked data beginning with "L" or "l" does not have
 905   /// the directive emitted (this occurs in ObjC metadata).
 906   if (!GV) return false;
 907
 908   // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
 909   if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
 910     // FIXME: ObjC metadata is currently emitted as internal symbols that have
 911     // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
 912     // this horrible hack can go away.
 913     const std::string &Name = Mang->getMangledName(GV);
 914     if (Name[0] == 'L' || Name[0] == 'l')
 915       return false;
 916   }
 917
 918   return true;
 919 }
 920
 921
 922 //===----------------------------------------------------------------------===//
 923 //                                  COFF
 924 //===----------------------------------------------------------------------===//
 925
 926 typedef StringMap<const MCSectionCOFF*> COFFUniqueMapTy;
 927
 928 TargetLoweringObjectFileCOFF::~TargetLoweringObjectFileCOFF() {
 929   delete (COFFUniqueMapTy*)UniquingMap;
 930 }
 931
 932
 933 const MCSection *TargetLoweringObjectFileCOFF::
 934 getCOFFSection(const char *Name, bool isDirective, SectionKind Kind) const {
 935   // Create the map if it doesn't already exist.
 936   if (UniquingMap == 0)
 937     UniquingMap = new MachOUniqueMapTy();
 938   COFFUniqueMapTy &Map = *(COFFUniqueMapTy*)UniquingMap;
 939
 940   // Do the lookup, if we have a hit, return it.
 941   const MCSectionCOFF *&Entry = Map[Name];
 942   if (Entry) return Entry;
 943
 944   return Entry = MCSectionCOFF::Create(Name, isDirective, Kind, getContext());
 945 }
 946
 947 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
 948                                               const TargetMachine &TM) {
 949   TargetLoweringObjectFile::Initialize(Ctx, TM);
 950   TextSection = getCOFFSection("\t.text", true, SectionKind::getText());
 951   DataSection = getCOFFSection("\t.data", true, SectionKind::getDataRel());
 952   StaticCtorSection =
 953     getCOFFSection(".ctors", false, SectionKind::getDataRel());
 954   StaticDtorSection =
 955     getCOFFSection(".dtors", false, SectionKind::getDataRel());
 956
 957
 958   // Debug info.
 959   // FIXME: Don't use 'directive' mode here.
 960   DwarfAbbrevSection =
 961     getCOFFSection("\t.section\t.debug_abbrev,\"dr\"",
 962                    true, SectionKind::getMetadata());
 963   DwarfInfoSection =
 964     getCOFFSection("\t.section\t.debug_info,\"dr\"",
 965                    true, SectionKind::getMetadata());
 966   DwarfLineSection =
 967     getCOFFSection("\t.section\t.debug_line,\"dr\"",
 968                    true, SectionKind::getMetadata());
 969   DwarfFrameSection =
 970     getCOFFSection("\t.section\t.debug_frame,\"dr\"",
 971                    true, SectionKind::getMetadata());
 972   DwarfPubNamesSection =
 973     getCOFFSection("\t.section\t.debug_pubnames,\"dr\"",
 974                    true, SectionKind::getMetadata());
 975   DwarfPubTypesSection =
 976     getCOFFSection("\t.section\t.debug_pubtypes,\"dr\"",
 977                    true, SectionKind::getMetadata());
 978   DwarfStrSection =
 979     getCOFFSection("\t.section\t.debug_str,\"dr\"",
 980                    true, SectionKind::getMetadata());
 981   DwarfLocSection =
 982     getCOFFSection("\t.section\t.debug_loc,\"dr\"",
 983                    true, SectionKind::getMetadata());
 984   DwarfARangesSection =
 985     getCOFFSection("\t.section\t.debug_aranges,\"dr\"",
 986                    true, SectionKind::getMetadata());
 987   DwarfRangesSection =
 988     getCOFFSection("\t.section\t.debug_ranges,\"dr\"",
 989                    true, SectionKind::getMetadata());
 990   DwarfMacroInfoSection =
 991     getCOFFSection("\t.section\t.debug_macinfo,\"dr\"",
 992                    true, SectionKind::getMetadata());
 993 }
 994
 995 const MCSection *TargetLoweringObjectFileCOFF::
 996 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
 997                          Mangler *Mang, const TargetMachine &TM) const {
 998   return getCOFFSection(GV->getSection().c_str(), false, Kind);
 999 }
1000
1001 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
1002   if (Kind.isText())
1003     return ".text$linkonce";
1004   if (Kind.isWriteable())
1005     return ".data$linkonce";
1006   return ".rdata$linkonce";
1007 }
1008
1009
1010 const MCSection *TargetLoweringObjectFileCOFF::
1011 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
1012                        Mangler *Mang, const TargetMachine &TM) const {
1013   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
1014
1015   // If this global is linkonce/weak and the target handles this by emitting it
1016   // into a 'uniqued' section name, create and return the section now.
1017   if (GV->isWeakForLinker()) {
1018     const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
1019     std::string Name = Mang->makeNameProper(GV->getNameStr());
1020     return getCOFFSection((Prefix+Name).c_str(), false, Kind);
1021   }
1022
1023   if (Kind.isText())
1024     return getTextSection();
1025
1026   return getDataSection();
1027 }
1028