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/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     // If the target has special section hacks for specifically named globals,
 238     // return them now.
 239     if (const MCSection *TS = getSpecialCasedSectionGlobals(GV, Mang, Kind))
 240       return TS;
 241
 242     // If the target has magic semantics for certain section names, make sure to
 243     // pick up the flags.  This allows the user to write things with attribute
 244     // section and still get the appropriate section flags printed.
 245     Kind = getKindForNamedSection(GV->getSection().c_str(), Kind);
 246
 247     return getOrCreateSection(GV->getSection().c_str(), false, Kind);
 248   }
 249
 250
 251   // Use default section depending on the 'type' of global
 252   return SelectSectionForGlobal(GV, Kind, Mang, TM);
 253 }
 254
 255
 256 // Lame default implementation. Calculate the section name for global.
 257 const MCSection *
 258 TargetLoweringObjectFile::SelectSectionForGlobal(const GlobalValue *GV,
 259                                                  SectionKind Kind,
 260                                                  Mangler *Mang,
 261                                                  const TargetMachine &TM) const{
 262   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
 263
 264   if (Kind.isText())
 265     return getTextSection();
 266
 267   if (Kind.isBSS() && BSSSection != 0)
 268     return BSSSection;
 269
 270   if (Kind.isReadOnly() && ReadOnlySection != 0)
 271     return ReadOnlySection;
 272
 273   return getDataSection();
 274 }
 275
 276 /// getSectionForConstant - Given a mergable constant with the
 277 /// specified size and relocation information, return a section that it
 278 /// should be placed in.
 279 const MCSection *
 280 TargetLoweringObjectFile::getSectionForConstant(SectionKind Kind) const {
 281   if (Kind.isReadOnly() && ReadOnlySection != 0)
 282     return ReadOnlySection;
 283
 284   return DataSection;
 285 }
 286
 287
 288 const MCSection *TargetLoweringObjectFile::
 289 getOrCreateSection(const char *Name, bool isDirective, SectionKind Kind) const {
 290   if (MCSection *S = Ctx->GetSection(Name))
 291     return S;
 292   return MCSection::Create(Name, isDirective, Kind, *Ctx);
 293 }
 294
 295
 296
 297 //===----------------------------------------------------------------------===//
 298 //                                  ELF
 299 //===----------------------------------------------------------------------===//
 300
 301 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
 302                                              const TargetMachine &TM) {
 303   TargetLoweringObjectFile::Initialize(Ctx, TM);
 304   if (!HasCrazyBSS)
 305     BSSSection = getOrCreateSection("\t.bss", true, SectionKind::getBSS());
 306   else
 307     // PPC/Linux doesn't support the .bss directive, it needs .section .bss.
 308     // FIXME: Does .section .bss work everywhere??
 309     // FIXME2: this should just be handle by the section printer.  We should get
 310     // away from syntactic view of the sections and MCSection should just be a
 311     // semantic view.
 312     BSSSection = getOrCreateSection("\t.bss", false, SectionKind::getBSS());
 313
 314
 315   TextSection = getOrCreateSection("\t.text", true, SectionKind::getText());
 316   DataSection = getOrCreateSection("\t.data", true, SectionKind::getDataRel());
 317   ReadOnlySection =
 318     getOrCreateSection("\t.rodata", false, SectionKind::getReadOnly());
 319   TLSDataSection =
 320     getOrCreateSection("\t.tdata", false, SectionKind::getThreadData());
 321
 322   TLSBSSSection = getOrCreateSection("\t.tbss", false,
 323                                      SectionKind::getThreadBSS());
 324
 325   DataRelSection = getOrCreateSection("\t.data.rel", false,
 326                                       SectionKind::getDataRel());
 327   DataRelLocalSection = getOrCreateSection("\t.data.rel.local", false,
 328                                    SectionKind::getDataRelLocal());
 329   DataRelROSection = getOrCreateSection("\t.data.rel.ro", false,
 330                                 SectionKind::getReadOnlyWithRel());
 331   DataRelROLocalSection =
 332     getOrCreateSection("\t.data.rel.ro.local", false,
 333                        SectionKind::getReadOnlyWithRelLocal());
 334
 335   MergeableConst4Section = getOrCreateSection(".rodata.cst4", false,
 336                                 SectionKind::getMergeableConst4());
 337   MergeableConst8Section = getOrCreateSection(".rodata.cst8", false,
 338                                 SectionKind::getMergeableConst8());
 339   MergeableConst16Section = getOrCreateSection(".rodata.cst16", false,
 340                                SectionKind::getMergeableConst16());
 341
 342   StaticCtorSection =
 343     getOrCreateSection(".ctors", false, SectionKind::getDataRel());
 344   StaticDtorSection =
 345     getOrCreateSection(".dtors", false, SectionKind::getDataRel());
 346
 347   // Exception Handling Sections.
 348
 349   // FIXME: We're emitting LSDA info into a readonly section on ELF, even though
 350   // it contains relocatable pointers.  In PIC mode, this is probably a big
 351   // runtime hit for C++ apps.  Either the contents of the LSDA need to be
 352   // adjusted or this should be a data section.
 353   LSDASection =
 354     getOrCreateSection(".gcc_except_table", false, SectionKind::getReadOnly());
 355   EHFrameSection =
 356     getOrCreateSection(".eh_frame", false, SectionKind::getDataRel());
 357
 358   // Debug Info Sections.
 359   DwarfAbbrevSection =
 360     getOrCreateSection(".debug_abbrev", false, SectionKind::getMetadata());
 361   DwarfInfoSection =
 362     getOrCreateSection(".debug_info", false, SectionKind::getMetadata());
 363   DwarfLineSection =
 364     getOrCreateSection(".debug_line", false, SectionKind::getMetadata());
 365   DwarfFrameSection =
 366     getOrCreateSection(".debug_frame", false, SectionKind::getMetadata());
 367   DwarfPubNamesSection =
 368     getOrCreateSection(".debug_pubnames", false, SectionKind::getMetadata());
 369   DwarfPubTypesSection =
 370     getOrCreateSection(".debug_pubtypes", false, SectionKind::getMetadata());
 371   DwarfStrSection =
 372     getOrCreateSection(".debug_str", false, SectionKind::getMetadata());
 373   DwarfLocSection =
 374     getOrCreateSection(".debug_loc", false, SectionKind::getMetadata());
 375   DwarfARangesSection =
 376     getOrCreateSection(".debug_aranges", false, SectionKind::getMetadata());
 377   DwarfRangesSection =
 378     getOrCreateSection(".debug_ranges", false, SectionKind::getMetadata());
 379   DwarfMacroInfoSection =
 380     getOrCreateSection(".debug_macinfo", false, SectionKind::getMetadata());
 381 }
 382
 383
 384 SectionKind TargetLoweringObjectFileELF::
 385 getKindForNamedSection(const char *Name, SectionKind K) const {
 386   if (Name[0] != '.') return K;
 387
 388   // Some lame default implementation based on some magic section names.
 389   if (strncmp(Name, ".gnu.linkonce.b.", 16) == 0 ||
 390       strncmp(Name, ".llvm.linkonce.b.", 17) == 0 ||
 391       strncmp(Name, ".gnu.linkonce.sb.", 17) == 0 ||
 392       strncmp(Name, ".llvm.linkonce.sb.", 18) == 0)
 393     return SectionKind::getBSS();
 394
 395   if (strcmp(Name, ".tdata") == 0 ||
 396       strncmp(Name, ".tdata.", 7) == 0 ||
 397       strncmp(Name, ".gnu.linkonce.td.", 17) == 0 ||
 398       strncmp(Name, ".llvm.linkonce.td.", 18) == 0)
 399     return SectionKind::getThreadData();
 400
 401   if (strcmp(Name, ".tbss") == 0 ||
 402       strncmp(Name, ".tbss.", 6) == 0 ||
 403       strncmp(Name, ".gnu.linkonce.tb.", 17) == 0 ||
 404       strncmp(Name, ".llvm.linkonce.tb.", 18) == 0)
 405     return SectionKind::getThreadBSS();
 406
 407   return K;
 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 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
 693                        Mangler *Mang, const TargetMachine &TM) const {
 694   assert(!Kind.isThreadLocal() && "Darwin doesn't support TLS");
 695
 696   if (Kind.isText())
 697     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
 698
 699   // If this is weak/linkonce, put this in a coalescable section, either in text
 700   // or data depending on if it is writable.
 701   if (GV->isWeakForLinker()) {
 702     if (Kind.isReadOnly())
 703       return ConstTextCoalSection;
 704     return DataCoalSection;
 705   }
 706
 707   // FIXME: Alignment check should be handled by section classifier.
 708   if (Kind.isMergeable1ByteCString() ||
 709       Kind.isMergeable2ByteCString()) {
 710     if (TM.getTargetData()->getPreferredAlignment(
 711                                               cast<GlobalVariable>(GV)) < 32) {
 712       if (Kind.isMergeable1ByteCString())
 713         return CStringSection;
 714       assert(Kind.isMergeable2ByteCString());
 715       return UStringSection;
 716     }
 717   }
 718
 719   if (Kind.isMergeableConst()) {
 720     if (Kind.isMergeableConst4())
 721       return FourByteConstantSection;
 722     if (Kind.isMergeableConst8())
 723       return EightByteConstantSection;
 724     if (Kind.isMergeableConst16() && SixteenByteConstantSection)
 725       return SixteenByteConstantSection;
 726   }
 727
 728   // Otherwise, if it is readonly, but not something we can specially optimize,
 729   // just drop it in .const.
 730   if (Kind.isReadOnly())
 731     return ReadOnlySection;
 732
 733   // If this is marked const, put it into a const section.  But if the dynamic
 734   // linker needs to write to it, put it in the data segment.
 735   if (Kind.isReadOnlyWithRel())
 736     return ConstDataSection;
 737
 738   // Otherwise, just drop the variable in the normal data section.
 739   return DataSection;
 740 }
 741
 742 const MCSection *
 743 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
 744   // If this constant requires a relocation, we have to put it in the data
 745   // segment, not in the text segment.
 746   if (Kind.isDataRel())
 747     return ConstDataSection;
 748
 749   if (Kind.isMergeableConst4())
 750     return FourByteConstantSection;
 751   if (Kind.isMergeableConst8())
 752     return EightByteConstantSection;
 753   if (Kind.isMergeableConst16() && SixteenByteConstantSection)
 754     return SixteenByteConstantSection;
 755   return ReadOnlySection;  // .const
 756 }
 757
 758 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
 759 /// not to emit the UsedDirective for some symbols in llvm.used.
 760 // FIXME: REMOVE this (rdar://7071300)
 761 bool TargetLoweringObjectFileMachO::
 762 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
 763   /// On Darwin, internally linked data beginning with "L" or "l" does not have
 764   /// the directive emitted (this occurs in ObjC metadata).
 765   if (!GV) return false;
 766
 767   // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
 768   if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
 769     // FIXME: ObjC metadata is currently emitted as internal symbols that have
 770     // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
 771     // this horrible hack can go away.
 772     const std::string &Name = Mang->getMangledName(GV);
 773     if (Name[0] == 'L' || Name[0] == 'l')
 774       return false;
 775   }
 776
 777   return true;
 778 }
 779
 780
 781 //===----------------------------------------------------------------------===//
 782 //                                  COFF
 783 //===----------------------------------------------------------------------===//
 784
 785 const MCSection *TargetLoweringObjectFileCOFF::
 786 getCOFFSection(const char *Name, bool isDirective, SectionKind K) {
 787   return getOrCreateSection(Name, isDirective, K);
 788 }
 789
 790 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
 791                                               const TargetMachine &TM) {
 792   TargetLoweringObjectFile::Initialize(Ctx, TM);
 793   TextSection = getOrCreateSection("\t.text", true,
 794                                    SectionKind::getText());
 795   DataSection = getOrCreateSection("\t.data", true,
 796                                    SectionKind::getDataRel());
 797   StaticCtorSection =
 798     getOrCreateSection(".ctors", false, SectionKind::getDataRel());
 799   StaticDtorSection =
 800     getOrCreateSection(".dtors", false, SectionKind::getDataRel());
 801
 802
 803   // Debug info.
 804   // FIXME: Don't use 'directive' mode here.
 805   DwarfAbbrevSection =
 806     getOrCreateSection("\t.section\t.debug_abbrev,\"dr\"",
 807                        true, SectionKind::getMetadata());
 808   DwarfInfoSection =
 809     getOrCreateSection("\t.section\t.debug_info,\"dr\"",
 810                        true, SectionKind::getMetadata());
 811   DwarfLineSection =
 812     getOrCreateSection("\t.section\t.debug_line,\"dr\"",
 813                        true, SectionKind::getMetadata());
 814   DwarfFrameSection =
 815     getOrCreateSection("\t.section\t.debug_frame,\"dr\"",
 816                        true, SectionKind::getMetadata());
 817   DwarfPubNamesSection =
 818     getOrCreateSection("\t.section\t.debug_pubnames,\"dr\"",
 819                        true, SectionKind::getMetadata());
 820   DwarfPubTypesSection =
 821     getOrCreateSection("\t.section\t.debug_pubtypes,\"dr\"",
 822                        true, SectionKind::getMetadata());
 823   DwarfStrSection =
 824     getOrCreateSection("\t.section\t.debug_str,\"dr\"",
 825                        true, SectionKind::getMetadata());
 826   DwarfLocSection =
 827     getOrCreateSection("\t.section\t.debug_loc,\"dr\"",
 828                        true, SectionKind::getMetadata());
 829   DwarfARangesSection =
 830     getOrCreateSection("\t.section\t.debug_aranges,\"dr\"",
 831                        true, SectionKind::getMetadata());
 832   DwarfRangesSection =
 833     getOrCreateSection("\t.section\t.debug_ranges,\"dr\"",
 834                        true, SectionKind::getMetadata());
 835   DwarfMacroInfoSection =
 836     getOrCreateSection("\t.section\t.debug_macinfo,\"dr\"",
 837                        true, SectionKind::getMetadata());
 838 }
 839
 840 void TargetLoweringObjectFileCOFF::
 841 getSectionFlagsAsString(SectionKind Kind, SmallVectorImpl<char> &Str) const {
 842   // FIXME: Inefficient.
 843   std::string Res = ",\"";
 844   if (Kind.isText())
 845     Res += 'x';
 846   if (Kind.isWriteable())
 847     Res += 'w';
 848   Res += "\"";
 849
 850   Str.append(Res.begin(), Res.end());
 851 }
 852
 853 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
 854   if (Kind.isText())
 855     return ".text$linkonce";
 856   if (Kind.isWriteable())
 857     return ".data$linkonce";
 858   return ".rdata$linkonce";
 859 }
 860
 861
 862 const MCSection *TargetLoweringObjectFileCOFF::
 863 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
 864                        Mangler *Mang, const TargetMachine &TM) const {
 865   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
 866
 867   // If this global is linkonce/weak and the target handles this by emitting it
 868   // into a 'uniqued' section name, create and return the section now.
 869   if (GV->isWeakForLinker()) {
 870     const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
 871     std::string Name = Mang->makeNameProper(GV->getNameStr());
 872     return getOrCreateSection((Prefix+Name).c_str(), false, Kind);
 873   }
 874
 875   if (Kind.isText())
 876     return getTextSection();
 877
 878   return getDataSection();
 879 }
 880