lib/CodeGen/MachOWriter.cpp

   1 //===-- MachOWriter.cpp - Target-independent Mach-O Writer code -----------===//
   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 the target-independent Mach-O writer.  This file writes
  11 // out the Mach-O file in the following order:
  12 //
  13 //  #1 FatHeader (universal-only)
  14 //  #2 FatArch (universal-only, 1 per universal arch)
  15 //  Per arch:
  16 //    #3 Header
  17 //    #4 Load Commands
  18 //    #5 Sections
  19 //    #6 Relocations
  20 //    #7 Symbols
  21 //    #8 Strings
  22 //
  23 //===----------------------------------------------------------------------===//
  24
  25 #include "MachO.h"
  26 #include "MachOWriter.h"
  27 #include "MachOCodeEmitter.h"
  28 #include "llvm/Constants.h"
  29 #include "llvm/DerivedTypes.h"
  30 #include "llvm/Module.h"
  31 #include "llvm/PassManager.h"
  32 #include "llvm/MC/MCAsmInfo.h"
  33 #include "llvm/Target/TargetData.h"
  34 #include "llvm/Target/TargetMachine.h"
  35 #include "llvm/Target/TargetMachOWriterInfo.h"
  36 #include "llvm/Support/Mangler.h"
  37 #include "llvm/Support/OutputBuffer.h"
  38 #include "llvm/Support/ErrorHandling.h"
  39 #include "llvm/Support/raw_ostream.h"
  40
  41 namespace llvm {
  42
  43 /// AddMachOWriter - Concrete function to add the Mach-O writer to the function
  44 /// pass manager.
  45 ObjectCodeEmitter *AddMachOWriter(PassManagerBase &PM,
  46                                          raw_ostream &O,
  47                                          TargetMachine &TM) {
  48   MachOWriter *MOW = new MachOWriter(O, TM);
  49   PM.add(MOW);
  50   return MOW->getObjectCodeEmitter();
  51 }
  52
  53 //===----------------------------------------------------------------------===//
  54 //                          MachOWriter Implementation
  55 //===----------------------------------------------------------------------===//
  56
  57 char MachOWriter::ID = 0;
  58
  59 MachOWriter::MachOWriter(raw_ostream &o, TargetMachine &tm)
  60   : MachineFunctionPass(&ID), O(o), TM(tm) {
  61   is64Bit = TM.getTargetData()->getPointerSizeInBits() == 64;
  62   isLittleEndian = TM.getTargetData()->isLittleEndian();
  63
  64   MAI = TM.getMCAsmInfo();
  65
  66   // Create the machine code emitter object for this target.
  67   MachOCE = new MachOCodeEmitter(*this, *getTextSection(true));
  68 }
  69
  70 MachOWriter::~MachOWriter() {
  71   delete MachOCE;
  72 }
  73
  74 bool MachOWriter::doInitialization(Module &M) {
  75   // Set the magic value, now that we know the pointer size and endianness
  76   Header.setMagic(isLittleEndian, is64Bit);
  77
  78   // Set the file type
  79   // FIXME: this only works for object files, we do not support the creation
  80   //        of dynamic libraries or executables at this time.
  81   Header.filetype = MachOHeader::MH_OBJECT;
  82
  83   Mang = new Mangler(M);
  84   return false;
  85 }
  86
  87 bool MachOWriter::runOnMachineFunction(MachineFunction &MF) {
  88   return false;
  89 }
  90
  91 /// doFinalization - Now that the module has been completely processed, emit
  92 /// the Mach-O file to 'O'.
  93 bool MachOWriter::doFinalization(Module &M) {
  94   // FIXME: we don't handle debug info yet, we should probably do that.
  95   // Okay, the.text section has been completed, build the .data, .bss, and
  96   // "common" sections next.
  97
  98   for (Module::global_iterator I = M.global_begin(), E = M.global_end();
  99        I != E; ++I)
 100     EmitGlobal(I);
 101
 102   // Emit the header and load commands.
 103   EmitHeaderAndLoadCommands();
 104
 105   // Emit the various sections and their relocation info.
 106   EmitSections();
 107   EmitRelocations();
 108
 109   // Write the symbol table and the string table to the end of the file.
 110   O.write((char*)&SymT[0], SymT.size());
 111   O.write((char*)&StrT[0], StrT.size());
 112
 113   // We are done with the abstract symbols.
 114   SectionList.clear();
 115   SymbolTable.clear();
 116   DynamicSymbolTable.clear();
 117
 118   // Release the name mangler object.
 119   delete Mang; Mang = 0;
 120   return false;
 121 }
 122
 123 // getConstSection - Get constant section for Constant 'C'
 124 MachOSection *MachOWriter::getConstSection(Constant *C) {
 125   const ConstantArray *CVA = dyn_cast<ConstantArray>(C);
 126   if (CVA && CVA->isCString())
 127     return getSection("__TEXT", "__cstring",
 128                       MachOSection::S_CSTRING_LITERALS);
 129
 130   const Type *Ty = C->getType();
 131   if (Ty->isPrimitiveType() || Ty->isInteger()) {
 132     unsigned Size = TM.getTargetData()->getTypeAllocSize(Ty);
 133     switch(Size) {
 134     default: break; // Fall through to __TEXT,__const
 135     case 4:
 136       return getSection("__TEXT", "__literal4",
 137                         MachOSection::S_4BYTE_LITERALS);
 138     case 8:
 139       return getSection("__TEXT", "__literal8",
 140                         MachOSection::S_8BYTE_LITERALS);
 141     case 16:
 142       return getSection("__TEXT", "__literal16",
 143                         MachOSection::S_16BYTE_LITERALS);
 144     }
 145   }
 146   return getSection("__TEXT", "__const");
 147 }
 148
 149 // getJumpTableSection - Select the Jump Table section
 150 MachOSection *MachOWriter::getJumpTableSection() {
 151   if (TM.getRelocationModel() == Reloc::PIC_)
 152     return getTextSection(false);
 153   else
 154     return getSection("__TEXT", "__const");
 155 }
 156
 157 // getSection - Return the section with the specified name, creating a new
 158 // section if one does not already exist.
 159 MachOSection *MachOWriter::getSection(const std::string &seg,
 160                                       const std::string &sect,
 161                                       unsigned Flags /* = 0 */ ) {
 162   MachOSection *MOS = SectionLookup[seg+sect];
 163   if (MOS) return MOS;
 164
 165   MOS = new MachOSection(seg, sect);
 166   SectionList.push_back(MOS);
 167   MOS->Index = SectionList.size();
 168   MOS->flags = MachOSection::S_REGULAR | Flags;
 169   SectionLookup[seg+sect] = MOS;
 170   return MOS;
 171 }
 172
 173 // getTextSection - Return text section with different flags for code/data
 174 MachOSection *MachOWriter::getTextSection(bool isCode /* = true */ ) {
 175   if (isCode)
 176     return getSection("__TEXT", "__text",
 177                       MachOSection::S_ATTR_PURE_INSTRUCTIONS |
 178                       MachOSection::S_ATTR_SOME_INSTRUCTIONS);
 179   else
 180     return getSection("__TEXT", "__text");
 181 }
 182
 183 MachOSection *MachOWriter::getBSSSection() {
 184   return getSection("__DATA", "__bss", MachOSection::S_ZEROFILL);
 185 }
 186
 187 // GetJTRelocation - Get a relocation a new BB relocation based
 188 // on target information.
 189 MachineRelocation MachOWriter::GetJTRelocation(unsigned Offset,
 190                                                MachineBasicBlock *MBB) const {
 191   return TM.getMachOWriterInfo()->GetJTRelocation(Offset, MBB);
 192 }
 193
 194 // GetTargetRelocation - Returns the number of relocations.
 195 unsigned MachOWriter::GetTargetRelocation(MachineRelocation &MR,
 196                              unsigned FromIdx, unsigned ToAddr,
 197                              unsigned ToIndex, OutputBuffer &RelocOut,
 198                              OutputBuffer &SecOut, bool Scattered,
 199                              bool Extern) {
 200   return TM.getMachOWriterInfo()->GetTargetRelocation(MR, FromIdx, ToAddr,
 201                                                       ToIndex, RelocOut,
 202                                                       SecOut, Scattered,
 203                                                       Extern);
 204 }
 205
 206 void MachOWriter::AddSymbolToSection(MachOSection *Sec, GlobalVariable *GV) {
 207   const Type *Ty = GV->getType()->getElementType();
 208   unsigned Size = TM.getTargetData()->getTypeAllocSize(Ty);
 209   unsigned Align = TM.getTargetData()->getPreferredAlignment(GV);
 210
 211   // Reserve space in the .bss section for this symbol while maintaining the
 212   // desired section alignment, which must be at least as much as required by
 213   // this symbol.
 214   OutputBuffer SecDataOut(Sec->getData(), is64Bit, isLittleEndian);
 215
 216   if (Align) {
 217     Align = Log2_32(Align);
 218     Sec->align = std::max(unsigned(Sec->align), Align);
 219
 220     Sec->emitAlignment(Sec->align);
 221   }
 222   // Globals without external linkage apparently do not go in the symbol table.
 223   if (!GV->hasLocalLinkage()) {
 224     MachOSym Sym(GV, Mang->getMangledName(GV), Sec->Index, MAI);
 225     Sym.n_value = Sec->size();
 226     SymbolTable.push_back(Sym);
 227   }
 228
 229   // Record the offset of the symbol, and then allocate space for it.
 230   // FIXME: remove when we have unified size + output buffer
 231
 232   // Now that we know what section the GlovalVariable is going to be emitted
 233   // into, update our mappings.
 234   // FIXME: We may also need to update this when outputting non-GlobalVariable
 235   // GlobalValues such as functions.
 236
 237   GVSection[GV] = Sec;
 238   GVOffset[GV] = Sec->size();
 239
 240   // Allocate space in the section for the global.
 241   for (unsigned i = 0; i < Size; ++i)
 242     SecDataOut.outbyte(0);
 243 }
 244
 245 void MachOWriter::EmitGlobal(GlobalVariable *GV) {
 246   const Type *Ty = GV->getType()->getElementType();
 247   unsigned Size = TM.getTargetData()->getTypeAllocSize(Ty);
 248   bool NoInit = !GV->hasInitializer();
 249
 250   // If this global has a zero initializer, it is part of the .bss or common
 251   // section.
 252   if (NoInit || GV->getInitializer()->isNullValue()) {
 253     // If this global is part of the common block, add it now.  Variables are
 254     // part of the common block if they are zero initialized and allowed to be
 255     // merged with other symbols.
 256     if (NoInit || GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
 257         GV->hasCommonLinkage()) {
 258       MachOSym ExtOrCommonSym(GV, Mang->getMangledName(GV),
 259                               MachOSym::NO_SECT, MAI);
 260       // For undefined (N_UNDF) external (N_EXT) types, n_value is the size in
 261       // bytes of the symbol.
 262       ExtOrCommonSym.n_value = Size;
 263       SymbolTable.push_back(ExtOrCommonSym);
 264       // Remember that we've seen this symbol
 265       GVOffset[GV] = Size;
 266       return;
 267     }
 268     // Otherwise, this symbol is part of the .bss section.
 269     MachOSection *BSS = getBSSSection();
 270     AddSymbolToSection(BSS, GV);
 271     return;
 272   }
 273
 274   // Scalar read-only data goes in a literal section if the scalar is 4, 8, or
 275   // 16 bytes, or a cstring.  Other read only data goes into a regular const
 276   // section.  Read-write data goes in the data section.
 277   MachOSection *Sec = GV->isConstant() ? getConstSection(GV->getInitializer()) :
 278                                          getDataSection();
 279   AddSymbolToSection(Sec, GV);
 280   InitMem(GV->getInitializer(), GVOffset[GV], TM.getTargetData(), Sec);
 281 }
 282
 283
 284
 285 void MachOWriter::EmitHeaderAndLoadCommands() {
 286   // Step #0: Fill in the segment load command size, since we need it to figure
 287   //          out the rest of the header fields
 288
 289   MachOSegment SEG("", is64Bit);
 290   SEG.nsects  = SectionList.size();
 291   SEG.cmdsize = SEG.cmdSize(is64Bit) +
 292                 SEG.nsects * SectionList[0]->cmdSize(is64Bit);
 293
 294   // Step #1: calculate the number of load commands.  We always have at least
 295   //          one, for the LC_SEGMENT load command, plus two for the normal
 296   //          and dynamic symbol tables, if there are any symbols.
 297   Header.ncmds = SymbolTable.empty() ? 1 : 3;
 298
 299   // Step #2: calculate the size of the load commands
 300   Header.sizeofcmds = SEG.cmdsize;
 301   if (!SymbolTable.empty())
 302     Header.sizeofcmds += SymTab.cmdsize + DySymTab.cmdsize;
 303
 304   // Step #3: write the header to the file
 305   // Local alias to shortenify coming code.
 306   std::vector<unsigned char> &FH = Header.HeaderData;
 307   OutputBuffer FHOut(FH, is64Bit, isLittleEndian);
 308
 309   FHOut.outword(Header.magic);
 310   FHOut.outword(TM.getMachOWriterInfo()->getCPUType());
 311   FHOut.outword(TM.getMachOWriterInfo()->getCPUSubType());
 312   FHOut.outword(Header.filetype);
 313   FHOut.outword(Header.ncmds);
 314   FHOut.outword(Header.sizeofcmds);
 315   FHOut.outword(Header.flags);
 316   if (is64Bit)
 317     FHOut.outword(Header.reserved);
 318
 319   // Step #4: Finish filling in the segment load command and write it out
 320   for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
 321          E = SectionList.end(); I != E; ++I)
 322     SEG.filesize += (*I)->size();
 323
 324   SEG.vmsize = SEG.filesize;
 325   SEG.fileoff = Header.cmdSize(is64Bit) + Header.sizeofcmds;
 326
 327   FHOut.outword(SEG.cmd);
 328   FHOut.outword(SEG.cmdsize);
 329   FHOut.outstring(SEG.segname, 16);
 330   FHOut.outaddr(SEG.vmaddr);
 331   FHOut.outaddr(SEG.vmsize);
 332   FHOut.outaddr(SEG.fileoff);
 333   FHOut.outaddr(SEG.filesize);
 334   FHOut.outword(SEG.maxprot);
 335   FHOut.outword(SEG.initprot);
 336   FHOut.outword(SEG.nsects);
 337   FHOut.outword(SEG.flags);
 338
 339   // Step #5: Finish filling in the fields of the MachOSections
 340   uint64_t currentAddr = 0;
 341   for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
 342          E = SectionList.end(); I != E; ++I) {
 343     MachOSection *MOS = *I;
 344     MOS->addr = currentAddr;
 345     MOS->offset = currentAddr + SEG.fileoff;
 346     // FIXME: do we need to do something with alignment here?
 347     currentAddr += MOS->size();
 348   }
 349
 350   // Step #6: Emit the symbol table to temporary buffers, so that we know the
 351   // size of the string table when we write the next load command.  This also
 352   // sorts and assigns indices to each of the symbols, which is necessary for
 353   // emitting relocations to externally-defined objects.
 354   BufferSymbolAndStringTable();
 355
 356   // Step #7: Calculate the number of relocations for each section and write out
 357   // the section commands for each section
 358   currentAddr += SEG.fileoff;
 359   for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
 360          E = SectionList.end(); I != E; ++I) {
 361     MachOSection *MOS = *I;
 362
 363     // Convert the relocations to target-specific relocations, and fill in the
 364     // relocation offset for this section.
 365     CalculateRelocations(*MOS);
 366     MOS->reloff = MOS->nreloc ? currentAddr : 0;
 367     currentAddr += MOS->nreloc * 8;
 368
 369     // write the finalized section command to the output buffer
 370     FHOut.outstring(MOS->sectname, 16);
 371     FHOut.outstring(MOS->segname, 16);
 372     FHOut.outaddr(MOS->addr);
 373     FHOut.outaddr(MOS->size());
 374     FHOut.outword(MOS->offset);
 375     FHOut.outword(MOS->align);
 376     FHOut.outword(MOS->reloff);
 377     FHOut.outword(MOS->nreloc);
 378     FHOut.outword(MOS->flags);
 379     FHOut.outword(MOS->reserved1);
 380     FHOut.outword(MOS->reserved2);
 381     if (is64Bit)
 382       FHOut.outword(MOS->reserved3);
 383   }
 384
 385   // Step #8: Emit LC_SYMTAB/LC_DYSYMTAB load commands
 386   SymTab.symoff  = currentAddr;
 387   SymTab.nsyms   = SymbolTable.size();
 388   SymTab.stroff  = SymTab.symoff + SymT.size();
 389   SymTab.strsize = StrT.size();
 390   FHOut.outword(SymTab.cmd);
 391   FHOut.outword(SymTab.cmdsize);
 392   FHOut.outword(SymTab.symoff);
 393   FHOut.outword(SymTab.nsyms);
 394   FHOut.outword(SymTab.stroff);
 395   FHOut.outword(SymTab.strsize);
 396
 397   // FIXME: set DySymTab fields appropriately
 398   // We should probably just update these in BufferSymbolAndStringTable since
 399   // thats where we're partitioning up the different kinds of symbols.
 400   FHOut.outword(DySymTab.cmd);
 401   FHOut.outword(DySymTab.cmdsize);
 402   FHOut.outword(DySymTab.ilocalsym);
 403   FHOut.outword(DySymTab.nlocalsym);
 404   FHOut.outword(DySymTab.iextdefsym);
 405   FHOut.outword(DySymTab.nextdefsym);
 406   FHOut.outword(DySymTab.iundefsym);
 407   FHOut.outword(DySymTab.nundefsym);
 408   FHOut.outword(DySymTab.tocoff);
 409   FHOut.outword(DySymTab.ntoc);
 410   FHOut.outword(DySymTab.modtaboff);
 411   FHOut.outword(DySymTab.nmodtab);
 412   FHOut.outword(DySymTab.extrefsymoff);
 413   FHOut.outword(DySymTab.nextrefsyms);
 414   FHOut.outword(DySymTab.indirectsymoff);
 415   FHOut.outword(DySymTab.nindirectsyms);
 416   FHOut.outword(DySymTab.extreloff);
 417   FHOut.outword(DySymTab.nextrel);
 418   FHOut.outword(DySymTab.locreloff);
 419   FHOut.outword(DySymTab.nlocrel);
 420
 421   O.write((char*)&FH[0], FH.size());
 422 }
 423
 424 /// EmitSections - Now that we have constructed the file header and load
 425 /// commands, emit the data for each section to the file.
 426 void MachOWriter::EmitSections() {
 427   for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
 428          E = SectionList.end(); I != E; ++I)
 429     // Emit the contents of each section
 430     if ((*I)->size())
 431       O.write((char*)&(*I)->getData()[0], (*I)->size());
 432 }
 433
 434 /// EmitRelocations - emit relocation data from buffer.
 435 void MachOWriter::EmitRelocations() {
 436   for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
 437          E = SectionList.end(); I != E; ++I)
 438     // Emit the relocation entry data for each section.
 439     if ((*I)->RelocBuffer.size())
 440       O.write((char*)&(*I)->RelocBuffer[0], (*I)->RelocBuffer.size());
 441 }
 442
 443 /// BufferSymbolAndStringTable - Sort the symbols we encountered and assign them
 444 /// each a string table index so that they appear in the correct order in the
 445 /// output file.
 446 void MachOWriter::BufferSymbolAndStringTable() {
 447   // The order of the symbol table is:
 448   // 1. local symbols
 449   // 2. defined external symbols (sorted by name)
 450   // 3. undefined external symbols (sorted by name)
 451
 452   // Before sorting the symbols, check the PendingGlobals for any undefined
 453   // globals that need to be put in the symbol table.
 454   for (std::vector<GlobalValue*>::iterator I = PendingGlobals.begin(),
 455          E = PendingGlobals.end(); I != E; ++I) {
 456     if (GVOffset[*I] == 0 && GVSection[*I] == 0) {
 457       MachOSym UndfSym(*I, Mang->getMangledName(*I), MachOSym::NO_SECT, MAI);
 458       SymbolTable.push_back(UndfSym);
 459       GVOffset[*I] = -1;
 460     }
 461   }
 462
 463   // Sort the symbols by name, so that when we partition the symbols by scope
 464   // of definition, we won't have to sort by name within each partition.
 465   std::sort(SymbolTable.begin(), SymbolTable.end(), MachOSym::SymCmp());
 466
 467   // Parition the symbol table entries so that all local symbols come before
 468   // all symbols with external linkage. { 1 | 2 3 }
 469   std::partition(SymbolTable.begin(), SymbolTable.end(),
 470                  MachOSym::PartitionByLocal);
 471
 472   // Advance iterator to beginning of external symbols and partition so that
 473   // all external symbols defined in this module come before all external
 474   // symbols defined elsewhere. { 1 | 2 | 3 }
 475   for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
 476          E = SymbolTable.end(); I != E; ++I) {
 477     if (!MachOSym::PartitionByLocal(*I)) {
 478       std::partition(I, E, MachOSym::PartitionByDefined);
 479       break;
 480     }
 481   }
 482
 483   // Calculate the starting index for each of the local, extern defined, and
 484   // undefined symbols, as well as the number of each to put in the LC_DYSYMTAB
 485   // load command.
 486   for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
 487          E = SymbolTable.end(); I != E; ++I) {
 488     if (MachOSym::PartitionByLocal(*I)) {
 489       ++DySymTab.nlocalsym;
 490       ++DySymTab.iextdefsym;
 491       ++DySymTab.iundefsym;
 492     } else if (MachOSym::PartitionByDefined(*I)) {
 493       ++DySymTab.nextdefsym;
 494       ++DySymTab.iundefsym;
 495     } else {
 496       ++DySymTab.nundefsym;
 497     }
 498   }
 499
 500   // Write out a leading zero byte when emitting string table, for n_strx == 0
 501   // which means an empty string.
 502   OutputBuffer StrTOut(StrT, is64Bit, isLittleEndian);
 503   StrTOut.outbyte(0);
 504
 505   // The order of the string table is:
 506   // 1. strings for external symbols
 507   // 2. strings for local symbols
 508   // Since this is the opposite order from the symbol table, which we have just
 509   // sorted, we can walk the symbol table backwards to output the string table.
 510   for (std::vector<MachOSym>::reverse_iterator I = SymbolTable.rbegin(),
 511         E = SymbolTable.rend(); I != E; ++I) {
 512     if (I->GVName == "") {
 513       I->n_strx = 0;
 514     } else {
 515       I->n_strx = StrT.size();
 516       StrTOut.outstring(I->GVName, I->GVName.length()+1);
 517     }
 518   }
 519
 520   OutputBuffer SymTOut(SymT, is64Bit, isLittleEndian);
 521
 522   unsigned index = 0;
 523   for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
 524          E = SymbolTable.end(); I != E; ++I, ++index) {
 525     // Add the section base address to the section offset in the n_value field
 526     // to calculate the full address.
 527     // FIXME: handle symbols where the n_value field is not the address
 528     GlobalValue *GV = const_cast<GlobalValue*>(I->GV);
 529     if (GV && GVSection[GV])
 530       I->n_value += GVSection[GV]->addr;
 531     if (GV && (GVOffset[GV] == -1))
 532       GVOffset[GV] = index;
 533
 534     // Emit nlist to buffer
 535     SymTOut.outword(I->n_strx);
 536     SymTOut.outbyte(I->n_type);
 537     SymTOut.outbyte(I->n_sect);
 538     SymTOut.outhalf(I->n_desc);
 539     SymTOut.outaddr(I->n_value);
 540   }
 541 }
 542
 543 /// CalculateRelocations - For each MachineRelocation in the current section,
 544 /// calculate the index of the section containing the object to be relocated,
 545 /// and the offset into that section.  From this information, create the
 546 /// appropriate target-specific MachORelocation type and add buffer it to be
 547 /// written out after we are finished writing out sections.
 548 void MachOWriter::CalculateRelocations(MachOSection &MOS) {
 549   std::vector<MachineRelocation> Relocations =  MOS.getRelocations();
 550   for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
 551     MachineRelocation &MR = Relocations[i];
 552     unsigned TargetSection = MR.getConstantVal();
 553     unsigned TargetAddr = 0;
 554     unsigned TargetIndex = 0;
 555
 556     // This is a scattered relocation entry if it points to a global value with
 557     // a non-zero offset.
 558     bool Scattered = false;
 559     bool Extern = false;
 560
 561     // Since we may not have seen the GlobalValue we were interested in yet at
 562     // the time we emitted the relocation for it, fix it up now so that it
 563     // points to the offset into the correct section.
 564     if (MR.isGlobalValue()) {
 565       GlobalValue *GV = MR.getGlobalValue();
 566       MachOSection *MOSPtr = GVSection[GV];
 567       intptr_t Offset = GVOffset[GV];
 568
 569       // If we have never seen the global before, it must be to a symbol
 570       // defined in another module (N_UNDF).
 571       if (!MOSPtr) {
 572         // FIXME: need to append stub suffix
 573         Extern = true;
 574         TargetAddr = 0;
 575         TargetIndex = GVOffset[GV];
 576       } else {
 577         Scattered = TargetSection != 0;
 578         TargetSection = MOSPtr->Index;
 579       }
 580       MR.setResultPointer((void*)Offset);
 581     }
 582
 583     // If the symbol is locally defined, pass in the address of the section and
 584     // the section index to the code which will generate the target relocation.
 585     if (!Extern) {
 586         MachOSection &To = *SectionList[TargetSection - 1];
 587         TargetAddr = To.addr;
 588         TargetIndex = To.Index;
 589     }
 590
 591     OutputBuffer RelocOut(MOS.RelocBuffer, is64Bit, isLittleEndian);
 592     OutputBuffer SecOut(MOS.getData(), is64Bit, isLittleEndian);
 593
 594     MOS.nreloc += GetTargetRelocation(MR, MOS.Index, TargetAddr, TargetIndex,
 595                                       RelocOut, SecOut, Scattered, Extern);
 596   }
 597 }
 598
 599 // InitMem - Write the value of a Constant to the specified memory location,
 600 // converting it into bytes and relocations.
 601 void MachOWriter::InitMem(const Constant *C, uintptr_t Offset,
 602                           const TargetData *TD, MachOSection* mos) {
 603   typedef std::pair<const Constant*, intptr_t> CPair;
 604   std::vector<CPair> WorkList;
 605   uint8_t *Addr = &mos->getData()[0];
 606
 607   WorkList.push_back(CPair(C,(intptr_t)Addr + Offset));
 608
 609   intptr_t ScatteredOffset = 0;
 610
 611   while (!WorkList.empty()) {
 612     const Constant *PC = WorkList.back().first;
 613     intptr_t PA = WorkList.back().second;
 614     WorkList.pop_back();
 615
 616     if (isa<UndefValue>(PC)) {
 617       continue;
 618     } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(PC)) {
 619       unsigned ElementSize =
 620         TD->getTypeAllocSize(CP->getType()->getElementType());
 621       for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i)
 622         WorkList.push_back(CPair(CP->getOperand(i), PA+i*ElementSize));
 623     } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(PC)) {
 624       //
 625       // FIXME: Handle ConstantExpression.  See EE::getConstantValue()
 626       //
 627       switch (CE->getOpcode()) {
 628       case Instruction::GetElementPtr: {
 629         SmallVector<Value*, 8> Indices(CE->op_begin()+1, CE->op_end());
 630         ScatteredOffset = TD->getIndexedOffset(CE->getOperand(0)->getType(),
 631                                                &Indices[0], Indices.size());
 632         WorkList.push_back(CPair(CE->getOperand(0), PA));
 633         break;
 634       }
 635       case Instruction::Add:
 636       default:
 637         errs() << "ConstantExpr not handled as global var init: " << *CE <<"\n";
 638         llvm_unreachable(0);
 639       }
 640     } else if (PC->getType()->isSingleValueType()) {
 641       unsigned char *ptr = (unsigned char *)PA;
 642       switch (PC->getType()->getTypeID()) {
 643       case Type::IntegerTyID: {
 644         unsigned NumBits = cast<IntegerType>(PC->getType())->getBitWidth();
 645         uint64_t val = cast<ConstantInt>(PC)->getZExtValue();
 646         if (NumBits <= 8)
 647           ptr[0] = val;
 648         else if (NumBits <= 16) {
 649           if (TD->isBigEndian())
 650             val = ByteSwap_16(val);
 651           ptr[0] = val;
 652           ptr[1] = val >> 8;
 653         } else if (NumBits <= 32) {
 654           if (TD->isBigEndian())
 655             val = ByteSwap_32(val);
 656           ptr[0] = val;
 657           ptr[1] = val >> 8;
 658           ptr[2] = val >> 16;
 659           ptr[3] = val >> 24;
 660         } else if (NumBits <= 64) {
 661           if (TD->isBigEndian())
 662             val = ByteSwap_64(val);
 663           ptr[0] = val;
 664           ptr[1] = val >> 8;
 665           ptr[2] = val >> 16;
 666           ptr[3] = val >> 24;
 667           ptr[4] = val >> 32;
 668           ptr[5] = val >> 40;
 669           ptr[6] = val >> 48;
 670           ptr[7] = val >> 56;
 671         } else {
 672           llvm_unreachable("Not implemented: bit widths > 64");
 673         }
 674         break;
 675       }
 676       case Type::FloatTyID: {
 677         uint32_t val = cast<ConstantFP>(PC)->getValueAPF().bitcastToAPInt().
 678                         getZExtValue();
 679         if (TD->isBigEndian())
 680           val = ByteSwap_32(val);
 681         ptr[0] = val;
 682         ptr[1] = val >> 8;
 683         ptr[2] = val >> 16;
 684         ptr[3] = val >> 24;
 685         break;
 686       }
 687       case Type::DoubleTyID: {
 688         uint64_t val = cast<ConstantFP>(PC)->getValueAPF().bitcastToAPInt().
 689                          getZExtValue();
 690         if (TD->isBigEndian())
 691           val = ByteSwap_64(val);
 692         ptr[0] = val;
 693         ptr[1] = val >> 8;
 694         ptr[2] = val >> 16;
 695         ptr[3] = val >> 24;
 696         ptr[4] = val >> 32;
 697         ptr[5] = val >> 40;
 698         ptr[6] = val >> 48;
 699         ptr[7] = val >> 56;
 700         break;
 701       }
 702       case Type::PointerTyID:
 703         if (isa<ConstantPointerNull>(PC))
 704           memset(ptr, 0, TD->getPointerSize());
 705         else if (const GlobalValue* GV = dyn_cast<GlobalValue>(PC)) {
 706           // FIXME: what about function stubs?
 707           mos->addRelocation(MachineRelocation::getGV(PA-(intptr_t)Addr,
 708                                                  MachineRelocation::VANILLA,
 709                                                  const_cast<GlobalValue*>(GV),
 710                                                  ScatteredOffset));
 711           ScatteredOffset = 0;
 712         } else
 713           llvm_unreachable("Unknown constant pointer type!");
 714         break;
 715       default:
 716         std::string msg;
 717         raw_string_ostream Msg(msg);
 718         Msg << "ERROR: Constant unimp for type: " << *PC->getType();
 719         llvm_report_error(Msg.str());
 720       }
 721     } else if (isa<ConstantAggregateZero>(PC)) {
 722       memset((void*)PA, 0, (size_t)TD->getTypeAllocSize(PC->getType()));
 723     } else if (const ConstantArray *CPA = dyn_cast<ConstantArray>(PC)) {
 724       unsigned ElementSize =
 725         TD->getTypeAllocSize(CPA->getType()->getElementType());
 726       for (unsigned i = 0, e = CPA->getNumOperands(); i != e; ++i)
 727         WorkList.push_back(CPair(CPA->getOperand(i), PA+i*ElementSize));
 728     } else if (const ConstantStruct *CPS = dyn_cast<ConstantStruct>(PC)) {
 729       const StructLayout *SL =
 730         TD->getStructLayout(cast<StructType>(CPS->getType()));
 731       for (unsigned i = 0, e = CPS->getNumOperands(); i != e; ++i)
 732         WorkList.push_back(CPair(CPS->getOperand(i),
 733                                  PA+SL->getElementOffset(i)));
 734     } else {
 735       errs() << "Bad Type: " << *PC->getType() << "\n";
 736       llvm_unreachable("Unknown constant type to initialize memory with!");
 737     }
 738   }
 739 }
 740
 741 //===----------------------------------------------------------------------===//
 742 //                          MachOSym Implementation
 743 //===----------------------------------------------------------------------===//
 744
 745 MachOSym::MachOSym(const GlobalValue *gv, std::string name, uint8_t sect,
 746                    const MCAsmInfo *MAI) :
 747   GV(gv), n_strx(0), n_type(sect == NO_SECT ? N_UNDF : N_SECT), n_sect(sect),
 748   n_desc(0), n_value(0) {
 749
 750   // FIXME: This is completely broken, it should use the mangler interface.
 751   switch (GV->getLinkage()) {
 752   default:
 753     llvm_unreachable("Unexpected linkage type!");
 754     break;
 755   case GlobalValue::WeakAnyLinkage:
 756   case GlobalValue::WeakODRLinkage:
 757   case GlobalValue::LinkOnceAnyLinkage:
 758   case GlobalValue::LinkOnceODRLinkage:
 759   case GlobalValue::CommonLinkage:
 760     assert(!isa<Function>(gv) && "Unexpected linkage type for Function!");
 761   case GlobalValue::ExternalLinkage:
 762     GVName = MAI->getGlobalPrefix() + name;
 763     n_type |= GV->hasHiddenVisibility() ? N_PEXT : N_EXT;
 764     break;
 765   case GlobalValue::PrivateLinkage:
 766     GVName = MAI->getPrivateGlobalPrefix() + name;
 767     break;
 768   case GlobalValue::LinkerPrivateLinkage:
 769     GVName = MAI->getLinkerPrivateGlobalPrefix() + name;
 770     break;
 771   case GlobalValue::InternalLinkage:
 772     GVName = MAI->getGlobalPrefix() + name;
 773     break;
 774   }
 775 }
 776
 777 } // end namespace llvm