lib/Bitcode/Writer/BitcodeWriter.cpp

   1 //===--- Bitcode/Writer/BitcodeWriter.cpp - Bitcode Writer ----------------===//
   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 // Bitcode writer implementation.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Bitcode/ReaderWriter.h"
  15 #include "llvm/Bitcode/BitstreamWriter.h"
  16 #include "llvm/Bitcode/LLVMBitCodes.h"
  17 #include "ValueEnumerator.h"
  18 #include "llvm/Constants.h"
  19 #include "llvm/DerivedTypes.h"
  20 #include "llvm/InlineAsm.h"
  21 #include "llvm/Instructions.h"
  22 #include "llvm/Module.h"
  23 #include "llvm/TypeSymbolTable.h"
  24 #include "llvm/ValueSymbolTable.h"
  25 #include "llvm/Support/MathExtras.h"
  26 #include "llvm/Support/Streams.h"
  27 #include "llvm/Support/raw_ostream.h"
  28 #include "llvm/System/Program.h"
  29 using namespace llvm;
  30
  31 /// These are manifest constants used by the bitcode writer. They do not need to
  32 /// be kept in sync with the reader, but need to be consistent within this file.
  33 enum {
  34   CurVersion = 0,
  35
  36   // VALUE_SYMTAB_BLOCK abbrev id's.
  37   VST_ENTRY_8_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
  38   VST_ENTRY_7_ABBREV,
  39   VST_ENTRY_6_ABBREV,
  40   VST_BBENTRY_6_ABBREV,
  41
  42   // CONSTANTS_BLOCK abbrev id's.
  43   CONSTANTS_SETTYPE_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
  44   CONSTANTS_INTEGER_ABBREV,
  45   CONSTANTS_CE_CAST_Abbrev,
  46   CONSTANTS_NULL_Abbrev,
  47
  48   // FUNCTION_BLOCK abbrev id's.
  49   FUNCTION_INST_LOAD_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
  50   FUNCTION_INST_BINOP_ABBREV,
  51   FUNCTION_INST_CAST_ABBREV,
  52   FUNCTION_INST_RET_VOID_ABBREV,
  53   FUNCTION_INST_RET_VAL_ABBREV,
  54   FUNCTION_INST_UNREACHABLE_ABBREV
  55 };
  56
  57
  58 static unsigned GetEncodedCastOpcode(unsigned Opcode) {
  59   switch (Opcode) {
  60   default: assert(0 && "Unknown cast instruction!");
  61   case Instruction::Trunc   : return bitc::CAST_TRUNC;
  62   case Instruction::ZExt    : return bitc::CAST_ZEXT;
  63   case Instruction::SExt    : return bitc::CAST_SEXT;
  64   case Instruction::FPToUI  : return bitc::CAST_FPTOUI;
  65   case Instruction::FPToSI  : return bitc::CAST_FPTOSI;
  66   case Instruction::UIToFP  : return bitc::CAST_UITOFP;
  67   case Instruction::SIToFP  : return bitc::CAST_SITOFP;
  68   case Instruction::FPTrunc : return bitc::CAST_FPTRUNC;
  69   case Instruction::FPExt   : return bitc::CAST_FPEXT;
  70   case Instruction::PtrToInt: return bitc::CAST_PTRTOINT;
  71   case Instruction::IntToPtr: return bitc::CAST_INTTOPTR;
  72   case Instruction::BitCast : return bitc::CAST_BITCAST;
  73   }
  74 }
  75
  76 static unsigned GetEncodedBinaryOpcode(unsigned Opcode) {
  77   switch (Opcode) {
  78   default: assert(0 && "Unknown binary instruction!");
  79   case Instruction::Add:  return bitc::BINOP_ADD;
  80   case Instruction::Sub:  return bitc::BINOP_SUB;
  81   case Instruction::Mul:  return bitc::BINOP_MUL;
  82   case Instruction::UDiv: return bitc::BINOP_UDIV;
  83   case Instruction::FDiv:
  84   case Instruction::SDiv: return bitc::BINOP_SDIV;
  85   case Instruction::URem: return bitc::BINOP_UREM;
  86   case Instruction::FRem:
  87   case Instruction::SRem: return bitc::BINOP_SREM;
  88   case Instruction::Shl:  return bitc::BINOP_SHL;
  89   case Instruction::LShr: return bitc::BINOP_LSHR;
  90   case Instruction::AShr: return bitc::BINOP_ASHR;
  91   case Instruction::And:  return bitc::BINOP_AND;
  92   case Instruction::Or:   return bitc::BINOP_OR;
  93   case Instruction::Xor:  return bitc::BINOP_XOR;
  94   }
  95 }
  96
  97
  98
  99 static void WriteStringRecord(unsigned Code, const std::string &Str,
 100                               unsigned AbbrevToUse, BitstreamWriter &Stream) {
 101   SmallVector<unsigned, 64> Vals;
 102
 103   // Code: [strchar x N]
 104   for (unsigned i = 0, e = Str.size(); i != e; ++i)
 105     Vals.push_back(Str[i]);
 106
 107   // Emit the finished record.
 108   Stream.EmitRecord(Code, Vals, AbbrevToUse);
 109 }
 110
 111 // Emit information about parameter attributes.
 112 static void WriteAttributeTable(const ValueEnumerator &VE,
 113                                 BitstreamWriter &Stream) {
 114   const std::vector<AttrListPtr> &Attrs = VE.getAttributes();
 115   if (Attrs.empty()) return;
 116
 117   Stream.EnterSubblock(bitc::PARAMATTR_BLOCK_ID, 3);
 118
 119   SmallVector<uint64_t, 64> Record;
 120   for (unsigned i = 0, e = Attrs.size(); i != e; ++i) {
 121     const AttrListPtr &A = Attrs[i];
 122     for (unsigned i = 0, e = A.getNumSlots(); i != e; ++i) {
 123       const AttributeWithIndex &PAWI = A.getSlot(i);
 124       Record.push_back(PAWI.Index);
 125
 126       // FIXME: remove in LLVM 3.0
 127       // Store the alignment in the bitcode as a 16-bit raw value instead of a
 128       // 5-bit log2 encoded value. Shift the bits above the alignment up by
 129       // 11 bits.
 130       uint64_t FauxAttr = PAWI.Attrs & 0xffff;
 131       if (PAWI.Attrs & Attribute::Alignment)
 132         FauxAttr |= (1ull<<16)<<(((PAWI.Attrs & Attribute::Alignment)-1) >> 16);
 133       FauxAttr |= (PAWI.Attrs & (0x3FFull << 21)) << 11;
 134
 135       Record.push_back(FauxAttr);
 136     }
 137
 138     Stream.EmitRecord(bitc::PARAMATTR_CODE_ENTRY, Record);
 139     Record.clear();
 140   }
 141
 142   Stream.ExitBlock();
 143 }
 144
 145 /// WriteTypeTable - Write out the type table for a module.
 146 static void WriteTypeTable(const ValueEnumerator &VE, BitstreamWriter &Stream) {
 147   const ValueEnumerator::TypeList &TypeList = VE.getTypes();
 148
 149   Stream.EnterSubblock(bitc::TYPE_BLOCK_ID, 4 /*count from # abbrevs */);
 150   SmallVector<uint64_t, 64> TypeVals;
 151
 152   // Abbrev for TYPE_CODE_POINTER.
 153   BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 154   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_POINTER));
 155   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 156                             Log2_32_Ceil(VE.getTypes().size()+1)));
 157   Abbv->Add(BitCodeAbbrevOp(0));  // Addrspace = 0
 158   unsigned PtrAbbrev = Stream.EmitAbbrev(Abbv);
 159
 160   // Abbrev for TYPE_CODE_FUNCTION.
 161   Abbv = new BitCodeAbbrev();
 162   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_FUNCTION));
 163   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // isvararg
 164   Abbv->Add(BitCodeAbbrevOp(0));  // FIXME: DEAD value, remove in LLVM 3.0
 165   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 166   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 167                             Log2_32_Ceil(VE.getTypes().size()+1)));
 168   unsigned FunctionAbbrev = Stream.EmitAbbrev(Abbv);
 169
 170   // Abbrev for TYPE_CODE_STRUCT.
 171   Abbv = new BitCodeAbbrev();
 172   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT));
 173   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // ispacked
 174   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 175   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 176                             Log2_32_Ceil(VE.getTypes().size()+1)));
 177   unsigned StructAbbrev = Stream.EmitAbbrev(Abbv);
 178
 179   // Abbrev for TYPE_CODE_ARRAY.
 180   Abbv = new BitCodeAbbrev();
 181   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_ARRAY));
 182   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));   // size
 183   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 184                             Log2_32_Ceil(VE.getTypes().size()+1)));
 185   unsigned ArrayAbbrev = Stream.EmitAbbrev(Abbv);
 186
 187   // Emit an entry count so the reader can reserve space.
 188   TypeVals.push_back(TypeList.size());
 189   Stream.EmitRecord(bitc::TYPE_CODE_NUMENTRY, TypeVals);
 190   TypeVals.clear();
 191
 192   // Loop over all of the types, emitting each in turn.
 193   for (unsigned i = 0, e = TypeList.size(); i != e; ++i) {
 194     const Type *T = TypeList[i].first;
 195     int AbbrevToUse = 0;
 196     unsigned Code = 0;
 197
 198     switch (T->getTypeID()) {
 199     default: assert(0 && "Unknown type!");
 200     case Type::VoidTyID:   Code = bitc::TYPE_CODE_VOID;   break;
 201     case Type::FloatTyID:  Code = bitc::TYPE_CODE_FLOAT;  break;
 202     case Type::DoubleTyID: Code = bitc::TYPE_CODE_DOUBLE; break;
 203     case Type::X86_FP80TyID: Code = bitc::TYPE_CODE_X86_FP80; break;
 204     case Type::FP128TyID: Code = bitc::TYPE_CODE_FP128; break;
 205     case Type::PPC_FP128TyID: Code = bitc::TYPE_CODE_PPC_FP128; break;
 206     case Type::LabelTyID:  Code = bitc::TYPE_CODE_LABEL;  break;
 207     case Type::OpaqueTyID: Code = bitc::TYPE_CODE_OPAQUE; break;
 208     case Type::IntegerTyID:
 209       // INTEGER: [width]
 210       Code = bitc::TYPE_CODE_INTEGER;
 211       TypeVals.push_back(cast<IntegerType>(T)->getBitWidth());
 212       break;
 213     case Type::PointerTyID: {
 214       const PointerType *PTy = cast<PointerType>(T);
 215       // POINTER: [pointee type, address space]
 216       Code = bitc::TYPE_CODE_POINTER;
 217       TypeVals.push_back(VE.getTypeID(PTy->getElementType()));
 218       unsigned AddressSpace = PTy->getAddressSpace();
 219       TypeVals.push_back(AddressSpace);
 220       if (AddressSpace == 0) AbbrevToUse = PtrAbbrev;
 221       break;
 222     }
 223     case Type::FunctionTyID: {
 224       const FunctionType *FT = cast<FunctionType>(T);
 225       // FUNCTION: [isvararg, attrid, retty, paramty x N]
 226       Code = bitc::TYPE_CODE_FUNCTION;
 227       TypeVals.push_back(FT->isVarArg());
 228       TypeVals.push_back(0);  // FIXME: DEAD: remove in llvm 3.0
 229       TypeVals.push_back(VE.getTypeID(FT->getReturnType()));
 230       for (unsigned i = 0, e = FT->getNumParams(); i != e; ++i)
 231         TypeVals.push_back(VE.getTypeID(FT->getParamType(i)));
 232       AbbrevToUse = FunctionAbbrev;
 233       break;
 234     }
 235     case Type::StructTyID: {
 236       const StructType *ST = cast<StructType>(T);
 237       // STRUCT: [ispacked, eltty x N]
 238       Code = bitc::TYPE_CODE_STRUCT;
 239       TypeVals.push_back(ST->isPacked());
 240       // Output all of the element types.
 241       for (StructType::element_iterator I = ST->element_begin(),
 242            E = ST->element_end(); I != E; ++I)
 243         TypeVals.push_back(VE.getTypeID(*I));
 244       AbbrevToUse = StructAbbrev;
 245       break;
 246     }
 247     case Type::ArrayTyID: {
 248       const ArrayType *AT = cast<ArrayType>(T);
 249       // ARRAY: [numelts, eltty]
 250       Code = bitc::TYPE_CODE_ARRAY;
 251       TypeVals.push_back(AT->getNumElements());
 252       TypeVals.push_back(VE.getTypeID(AT->getElementType()));
 253       AbbrevToUse = ArrayAbbrev;
 254       break;
 255     }
 256     case Type::VectorTyID: {
 257       const VectorType *VT = cast<VectorType>(T);
 258       // VECTOR [numelts, eltty]
 259       Code = bitc::TYPE_CODE_VECTOR;
 260       TypeVals.push_back(VT->getNumElements());
 261       TypeVals.push_back(VE.getTypeID(VT->getElementType()));
 262       break;
 263     }
 264     }
 265
 266     // Emit the finished record.
 267     Stream.EmitRecord(Code, TypeVals, AbbrevToUse);
 268     TypeVals.clear();
 269   }
 270
 271   Stream.ExitBlock();
 272 }
 273
 274 static unsigned getEncodedLinkage(const GlobalValue *GV) {
 275   switch (GV->getLinkage()) {
 276   default: assert(0 && "Invalid linkage!");
 277   case GlobalValue::GhostLinkage:  // Map ghost linkage onto external.
 278   case GlobalValue::ExternalLinkage:     return 0;
 279   case GlobalValue::WeakLinkage:         return 1;
 280   case GlobalValue::AppendingLinkage:    return 2;
 281   case GlobalValue::InternalLinkage:     return 3;
 282   case GlobalValue::LinkOnceLinkage:     return 4;
 283   case GlobalValue::DLLImportLinkage:    return 5;
 284   case GlobalValue::DLLExportLinkage:    return 6;
 285   case GlobalValue::ExternalWeakLinkage: return 7;
 286   case GlobalValue::CommonLinkage:       return 8;
 287   case GlobalValue::PrivateLinkage:      return 9;
 288   }
 289 }
 290
 291 static unsigned getEncodedVisibility(const GlobalValue *GV) {
 292   switch (GV->getVisibility()) {
 293   default: assert(0 && "Invalid visibility!");
 294   case GlobalValue::DefaultVisibility:   return 0;
 295   case GlobalValue::HiddenVisibility:    return 1;
 296   case GlobalValue::ProtectedVisibility: return 2;
 297   }
 298 }
 299
 300 // Emit top-level description of module, including target triple, inline asm,
 301 // descriptors for global variables, and function prototype info.
 302 static void WriteModuleInfo(const Module *M, const ValueEnumerator &VE,
 303                             BitstreamWriter &Stream) {
 304   // Emit the list of dependent libraries for the Module.
 305   for (Module::lib_iterator I = M->lib_begin(), E = M->lib_end(); I != E; ++I)
 306     WriteStringRecord(bitc::MODULE_CODE_DEPLIB, *I, 0/*TODO*/, Stream);
 307
 308   // Emit various pieces of data attached to a module.
 309   if (!M->getTargetTriple().empty())
 310     WriteStringRecord(bitc::MODULE_CODE_TRIPLE, M->getTargetTriple(),
 311                       0/*TODO*/, Stream);
 312   if (!M->getDataLayout().empty())
 313     WriteStringRecord(bitc::MODULE_CODE_DATALAYOUT, M->getDataLayout(),
 314                       0/*TODO*/, Stream);
 315   if (!M->getModuleInlineAsm().empty())
 316     WriteStringRecord(bitc::MODULE_CODE_ASM, M->getModuleInlineAsm(),
 317                       0/*TODO*/, Stream);
 318
 319   // Emit information about sections and GC, computing how many there are. Also
 320   // compute the maximum alignment value.
 321   std::map<std::string, unsigned> SectionMap;
 322   std::map<std::string, unsigned> GCMap;
 323   unsigned MaxAlignment = 0;
 324   unsigned MaxGlobalType = 0;
 325   for (Module::const_global_iterator GV = M->global_begin(),E = M->global_end();
 326        GV != E; ++GV) {
 327     MaxAlignment = std::max(MaxAlignment, GV->getAlignment());
 328     MaxGlobalType = std::max(MaxGlobalType, VE.getTypeID(GV->getType()));
 329
 330     if (!GV->hasSection()) continue;
 331     // Give section names unique ID's.
 332     unsigned &Entry = SectionMap[GV->getSection()];
 333     if (Entry != 0) continue;
 334     WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, GV->getSection(),
 335                       0/*TODO*/, Stream);
 336     Entry = SectionMap.size();
 337   }
 338   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F) {
 339     MaxAlignment = std::max(MaxAlignment, F->getAlignment());
 340     if (F->hasSection()) {
 341       // Give section names unique ID's.
 342       unsigned &Entry = SectionMap[F->getSection()];
 343       if (!Entry) {
 344         WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, F->getSection(),
 345                           0/*TODO*/, Stream);
 346         Entry = SectionMap.size();
 347       }
 348     }
 349     if (F->hasGC()) {
 350       // Same for GC names.
 351       unsigned &Entry = GCMap[F->getGC()];
 352       if (!Entry) {
 353         WriteStringRecord(bitc::MODULE_CODE_GCNAME, F->getGC(),
 354                           0/*TODO*/, Stream);
 355         Entry = GCMap.size();
 356       }
 357     }
 358   }
 359
 360   // Emit abbrev for globals, now that we know # sections and max alignment.
 361   unsigned SimpleGVarAbbrev = 0;
 362   if (!M->global_empty()) {
 363     // Add an abbrev for common globals with no visibility or thread localness.
 364     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 365     Abbv->Add(BitCodeAbbrevOp(bitc::MODULE_CODE_GLOBALVAR));
 366     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 367                               Log2_32_Ceil(MaxGlobalType+1)));
 368     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));      // Constant.
 369     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));        // Initializer.
 370     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));      // Linkage.
 371     if (MaxAlignment == 0)                                      // Alignment.
 372       Abbv->Add(BitCodeAbbrevOp(0));
 373     else {
 374       unsigned MaxEncAlignment = Log2_32(MaxAlignment)+1;
 375       Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 376                                Log2_32_Ceil(MaxEncAlignment+1)));
 377     }
 378     if (SectionMap.empty())                                    // Section.
 379       Abbv->Add(BitCodeAbbrevOp(0));
 380     else
 381       Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 382                                Log2_32_Ceil(SectionMap.size()+1)));
 383     // Don't bother emitting vis + thread local.
 384     SimpleGVarAbbrev = Stream.EmitAbbrev(Abbv);
 385   }
 386
 387   // Emit the global variable information.
 388   SmallVector<unsigned, 64> Vals;
 389   for (Module::const_global_iterator GV = M->global_begin(),E = M->global_end();
 390        GV != E; ++GV) {
 391     unsigned AbbrevToUse = 0;
 392
 393     // GLOBALVAR: [type, isconst, initid,
 394     //             linkage, alignment, section, visibility, threadlocal]
 395     Vals.push_back(VE.getTypeID(GV->getType()));
 396     Vals.push_back(GV->isConstant());
 397     Vals.push_back(GV->isDeclaration() ? 0 :
 398                    (VE.getValueID(GV->getInitializer()) + 1));
 399     Vals.push_back(getEncodedLinkage(GV));
 400     Vals.push_back(Log2_32(GV->getAlignment())+1);
 401     Vals.push_back(GV->hasSection() ? SectionMap[GV->getSection()] : 0);
 402     if (GV->isThreadLocal() ||
 403         GV->getVisibility() != GlobalValue::DefaultVisibility) {
 404       Vals.push_back(getEncodedVisibility(GV));
 405       Vals.push_back(GV->isThreadLocal());
 406     } else {
 407       AbbrevToUse = SimpleGVarAbbrev;
 408     }
 409
 410     Stream.EmitRecord(bitc::MODULE_CODE_GLOBALVAR, Vals, AbbrevToUse);
 411     Vals.clear();
 412   }
 413
 414   // Emit the function proto information.
 415   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F) {
 416     // FUNCTION:  [type, callingconv, isproto, paramattr,
 417     //             linkage, alignment, section, visibility, gc]
 418     Vals.push_back(VE.getTypeID(F->getType()));
 419     Vals.push_back(F->getCallingConv());
 420     Vals.push_back(F->isDeclaration());
 421     Vals.push_back(getEncodedLinkage(F));
 422     Vals.push_back(VE.getAttributeID(F->getAttributes()));
 423     Vals.push_back(Log2_32(F->getAlignment())+1);
 424     Vals.push_back(F->hasSection() ? SectionMap[F->getSection()] : 0);
 425     Vals.push_back(getEncodedVisibility(F));
 426     Vals.push_back(F->hasGC() ? GCMap[F->getGC()] : 0);
 427
 428     unsigned AbbrevToUse = 0;
 429     Stream.EmitRecord(bitc::MODULE_CODE_FUNCTION, Vals, AbbrevToUse);
 430     Vals.clear();
 431   }
 432
 433
 434   // Emit the alias information.
 435   for (Module::const_alias_iterator AI = M->alias_begin(), E = M->alias_end();
 436        AI != E; ++AI) {
 437     Vals.push_back(VE.getTypeID(AI->getType()));
 438     Vals.push_back(VE.getValueID(AI->getAliasee()));
 439     Vals.push_back(getEncodedLinkage(AI));
 440     Vals.push_back(getEncodedVisibility(AI));
 441     unsigned AbbrevToUse = 0;
 442     Stream.EmitRecord(bitc::MODULE_CODE_ALIAS, Vals, AbbrevToUse);
 443     Vals.clear();
 444   }
 445 }
 446
 447
 448 static void WriteConstants(unsigned FirstVal, unsigned LastVal,
 449                            const ValueEnumerator &VE,
 450                            BitstreamWriter &Stream, bool isGlobal) {
 451   if (FirstVal == LastVal) return;
 452
 453   Stream.EnterSubblock(bitc::CONSTANTS_BLOCK_ID, 4);
 454
 455   unsigned AggregateAbbrev = 0;
 456   unsigned String8Abbrev = 0;
 457   unsigned CString7Abbrev = 0;
 458   unsigned CString6Abbrev = 0;
 459   // If this is a constant pool for the module, emit module-specific abbrevs.
 460   if (isGlobal) {
 461     // Abbrev for CST_CODE_AGGREGATE.
 462     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 463     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_AGGREGATE));
 464     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 465     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, Log2_32_Ceil(LastVal+1)));
 466     AggregateAbbrev = Stream.EmitAbbrev(Abbv);
 467
 468     // Abbrev for CST_CODE_STRING.
 469     Abbv = new BitCodeAbbrev();
 470     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_STRING));
 471     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 472     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
 473     String8Abbrev = Stream.EmitAbbrev(Abbv);
 474     // Abbrev for CST_CODE_CSTRING.
 475     Abbv = new BitCodeAbbrev();
 476     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CSTRING));
 477     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 478     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
 479     CString7Abbrev = Stream.EmitAbbrev(Abbv);
 480     // Abbrev for CST_CODE_CSTRING.
 481     Abbv = new BitCodeAbbrev();
 482     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CSTRING));
 483     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 484     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
 485     CString6Abbrev = Stream.EmitAbbrev(Abbv);
 486   }
 487
 488   SmallVector<uint64_t, 64> Record;
 489
 490   const ValueEnumerator::ValueList &Vals = VE.getValues();
 491   const Type *LastTy = 0;
 492   for (unsigned i = FirstVal; i != LastVal; ++i) {
 493     const Value *V = Vals[i].first;
 494     // If we need to switch types, do so now.
 495     if (V->getType() != LastTy) {
 496       LastTy = V->getType();
 497       Record.push_back(VE.getTypeID(LastTy));
 498       Stream.EmitRecord(bitc::CST_CODE_SETTYPE, Record,
 499                         CONSTANTS_SETTYPE_ABBREV);
 500       Record.clear();
 501     }
 502
 503     if (const InlineAsm *IA = dyn_cast<InlineAsm>(V)) {
 504       Record.push_back(unsigned(IA->hasSideEffects()));
 505
 506       // Add the asm string.
 507       const std::string &AsmStr = IA->getAsmString();
 508       Record.push_back(AsmStr.size());
 509       for (unsigned i = 0, e = AsmStr.size(); i != e; ++i)
 510         Record.push_back(AsmStr[i]);
 511
 512       // Add the constraint string.
 513       const std::string &ConstraintStr = IA->getConstraintString();
 514       Record.push_back(ConstraintStr.size());
 515       for (unsigned i = 0, e = ConstraintStr.size(); i != e; ++i)
 516         Record.push_back(ConstraintStr[i]);
 517       Stream.EmitRecord(bitc::CST_CODE_INLINEASM, Record);
 518       Record.clear();
 519       continue;
 520     }
 521     const Constant *C = cast<Constant>(V);
 522     unsigned Code = -1U;
 523     unsigned AbbrevToUse = 0;
 524     if (C->isNullValue()) {
 525       Code = bitc::CST_CODE_NULL;
 526     } else if (isa<UndefValue>(C)) {
 527       Code = bitc::CST_CODE_UNDEF;
 528     } else if (const ConstantInt *IV = dyn_cast<ConstantInt>(C)) {
 529       if (IV->getBitWidth() <= 64) {
 530         int64_t V = IV->getSExtValue();
 531         if (V >= 0)
 532           Record.push_back(V << 1);
 533         else
 534           Record.push_back((-V << 1) | 1);
 535         Code = bitc::CST_CODE_INTEGER;
 536         AbbrevToUse = CONSTANTS_INTEGER_ABBREV;
 537       } else {                             // Wide integers, > 64 bits in size.
 538         // We have an arbitrary precision integer value to write whose
 539         // bit width is > 64. However, in canonical unsigned integer
 540         // format it is likely that the high bits are going to be zero.
 541         // So, we only write the number of active words.
 542         unsigned NWords = IV->getValue().getActiveWords();
 543         const uint64_t *RawWords = IV->getValue().getRawData();
 544         for (unsigned i = 0; i != NWords; ++i) {
 545           int64_t V = RawWords[i];
 546           if (V >= 0)
 547             Record.push_back(V << 1);
 548           else
 549             Record.push_back((-V << 1) | 1);
 550         }
 551         Code = bitc::CST_CODE_WIDE_INTEGER;
 552       }
 553     } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
 554       Code = bitc::CST_CODE_FLOAT;
 555       const Type *Ty = CFP->getType();
 556       if (Ty == Type::FloatTy || Ty == Type::DoubleTy) {
 557         Record.push_back(CFP->getValueAPF().bitcastToAPInt().getZExtValue());
 558       } else if (Ty == Type::X86_FP80Ty) {
 559         // api needed to prevent premature destruction
 560         APInt api = CFP->getValueAPF().bitcastToAPInt();
 561         const uint64_t *p = api.getRawData();
 562         Record.push_back(p[0]);
 563         Record.push_back((uint16_t)p[1]);
 564       } else if (Ty == Type::FP128Ty || Ty == Type::PPC_FP128Ty) {
 565         APInt api = CFP->getValueAPF().bitcastToAPInt();
 566         const uint64_t *p = api.getRawData();
 567         Record.push_back(p[0]);
 568         Record.push_back(p[1]);
 569       } else {
 570         assert (0 && "Unknown FP type!");
 571       }
 572     } else if (isa<ConstantArray>(C) && cast<ConstantArray>(C)->isString()) {
 573       // Emit constant strings specially.
 574       unsigned NumOps = C->getNumOperands();
 575       // If this is a null-terminated string, use the denser CSTRING encoding.
 576       if (C->getOperand(NumOps-1)->isNullValue()) {
 577         Code = bitc::CST_CODE_CSTRING;
 578         --NumOps;  // Don't encode the null, which isn't allowed by char6.
 579       } else {
 580         Code = bitc::CST_CODE_STRING;
 581         AbbrevToUse = String8Abbrev;
 582       }
 583       bool isCStr7 = Code == bitc::CST_CODE_CSTRING;
 584       bool isCStrChar6 = Code == bitc::CST_CODE_CSTRING;
 585       for (unsigned i = 0; i != NumOps; ++i) {
 586         unsigned char V = cast<ConstantInt>(C->getOperand(i))->getZExtValue();
 587         Record.push_back(V);
 588         isCStr7 &= (V & 128) == 0;
 589         if (isCStrChar6)
 590           isCStrChar6 = BitCodeAbbrevOp::isChar6(V);
 591       }
 592
 593       if (isCStrChar6)
 594         AbbrevToUse = CString6Abbrev;
 595       else if (isCStr7)
 596         AbbrevToUse = CString7Abbrev;
 597     } else if (isa<ConstantArray>(C) || isa<ConstantStruct>(V) ||
 598                isa<ConstantVector>(V)) {
 599       Code = bitc::CST_CODE_AGGREGATE;
 600       for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
 601         Record.push_back(VE.getValueID(C->getOperand(i)));
 602       AbbrevToUse = AggregateAbbrev;
 603     } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
 604       switch (CE->getOpcode()) {
 605       default:
 606         if (Instruction::isCast(CE->getOpcode())) {
 607           Code = bitc::CST_CODE_CE_CAST;
 608           Record.push_back(GetEncodedCastOpcode(CE->getOpcode()));
 609           Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
 610           Record.push_back(VE.getValueID(C->getOperand(0)));
 611           AbbrevToUse = CONSTANTS_CE_CAST_Abbrev;
 612         } else {
 613           assert(CE->getNumOperands() == 2 && "Unknown constant expr!");
 614           Code = bitc::CST_CODE_CE_BINOP;
 615           Record.push_back(GetEncodedBinaryOpcode(CE->getOpcode()));
 616           Record.push_back(VE.getValueID(C->getOperand(0)));
 617           Record.push_back(VE.getValueID(C->getOperand(1)));
 618         }
 619         break;
 620       case Instruction::GetElementPtr:
 621         Code = bitc::CST_CODE_CE_GEP;
 622         for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) {
 623           Record.push_back(VE.getTypeID(C->getOperand(i)->getType()));
 624           Record.push_back(VE.getValueID(C->getOperand(i)));
 625         }
 626         break;
 627       case Instruction::Select:
 628         Code = bitc::CST_CODE_CE_SELECT;
 629         Record.push_back(VE.getValueID(C->getOperand(0)));
 630         Record.push_back(VE.getValueID(C->getOperand(1)));
 631         Record.push_back(VE.getValueID(C->getOperand(2)));
 632         break;
 633       case Instruction::ExtractElement:
 634         Code = bitc::CST_CODE_CE_EXTRACTELT;
 635         Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
 636         Record.push_back(VE.getValueID(C->getOperand(0)));
 637         Record.push_back(VE.getValueID(C->getOperand(1)));
 638         break;
 639       case Instruction::InsertElement:
 640         Code = bitc::CST_CODE_CE_INSERTELT;
 641         Record.push_back(VE.getValueID(C->getOperand(0)));
 642         Record.push_back(VE.getValueID(C->getOperand(1)));
 643         Record.push_back(VE.getValueID(C->getOperand(2)));
 644         break;
 645       case Instruction::ShuffleVector:
 646         Code = bitc::CST_CODE_CE_SHUFFLEVEC;
 647         Record.push_back(VE.getValueID(C->getOperand(0)));
 648         Record.push_back(VE.getValueID(C->getOperand(1)));
 649         Record.push_back(VE.getValueID(C->getOperand(2)));
 650         break;
 651       case Instruction::ICmp:
 652       case Instruction::FCmp:
 653       case Instruction::VICmp:
 654       case Instruction::VFCmp:
 655         if (isa<VectorType>(C->getOperand(0)->getType())
 656             && (CE->getOpcode() == Instruction::ICmp
 657                 || CE->getOpcode() == Instruction::FCmp)) {
 658           // compare returning vector of Int1Ty
 659           assert(0 && "Unsupported constant!");
 660         } else {
 661           Code = bitc::CST_CODE_CE_CMP;
 662         }
 663         Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
 664         Record.push_back(VE.getValueID(C->getOperand(0)));
 665         Record.push_back(VE.getValueID(C->getOperand(1)));
 666         Record.push_back(CE->getPredicate());
 667         break;
 668       }
 669     } else {
 670       assert(0 && "Unknown constant!");
 671     }
 672     Stream.EmitRecord(Code, Record, AbbrevToUse);
 673     Record.clear();
 674   }
 675
 676   Stream.ExitBlock();
 677 }
 678
 679 static void WriteModuleConstants(const ValueEnumerator &VE,
 680                                  BitstreamWriter &Stream) {
 681   const ValueEnumerator::ValueList &Vals = VE.getValues();
 682
 683   // Find the first constant to emit, which is the first non-globalvalue value.
 684   // We know globalvalues have been emitted by WriteModuleInfo.
 685   for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
 686     if (!isa<GlobalValue>(Vals[i].first)) {
 687       WriteConstants(i, Vals.size(), VE, Stream, true);
 688       return;
 689     }
 690   }
 691 }
 692
 693 /// PushValueAndType - The file has to encode both the value and type id for
 694 /// many values, because we need to know what type to create for forward
 695 /// references.  However, most operands are not forward references, so this type
 696 /// field is not needed.
 697 ///
 698 /// This function adds V's value ID to Vals.  If the value ID is higher than the
 699 /// instruction ID, then it is a forward reference, and it also includes the
 700 /// type ID.
 701 static bool PushValueAndType(const Value *V, unsigned InstID,
 702                              SmallVector<unsigned, 64> &Vals,
 703                              ValueEnumerator &VE) {
 704   unsigned ValID = VE.getValueID(V);
 705   Vals.push_back(ValID);
 706   if (ValID >= InstID) {
 707     Vals.push_back(VE.getTypeID(V->getType()));
 708     return true;
 709   }
 710   return false;
 711 }
 712
 713 /// WriteInstruction - Emit an instruction to the specified stream.
 714 static void WriteInstruction(const Instruction &I, unsigned InstID,
 715                              ValueEnumerator &VE, BitstreamWriter &Stream,
 716                              SmallVector<unsigned, 64> &Vals) {
 717   unsigned Code = 0;
 718   unsigned AbbrevToUse = 0;
 719   switch (I.getOpcode()) {
 720   default:
 721     if (Instruction::isCast(I.getOpcode())) {
 722       Code = bitc::FUNC_CODE_INST_CAST;
 723       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
 724         AbbrevToUse = FUNCTION_INST_CAST_ABBREV;
 725       Vals.push_back(VE.getTypeID(I.getType()));
 726       Vals.push_back(GetEncodedCastOpcode(I.getOpcode()));
 727     } else {
 728       assert(isa<BinaryOperator>(I) && "Unknown instruction!");
 729       Code = bitc::FUNC_CODE_INST_BINOP;
 730       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
 731         AbbrevToUse = FUNCTION_INST_BINOP_ABBREV;
 732       Vals.push_back(VE.getValueID(I.getOperand(1)));
 733       Vals.push_back(GetEncodedBinaryOpcode(I.getOpcode()));
 734     }
 735     break;
 736
 737   case Instruction::GetElementPtr:
 738     Code = bitc::FUNC_CODE_INST_GEP;
 739     for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
 740       PushValueAndType(I.getOperand(i), InstID, Vals, VE);
 741     break;
 742   case Instruction::ExtractValue: {
 743     Code = bitc::FUNC_CODE_INST_EXTRACTVAL;
 744     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
 745     const ExtractValueInst *EVI = cast<ExtractValueInst>(&I);
 746     for (const unsigned *i = EVI->idx_begin(), *e = EVI->idx_end(); i != e; ++i)
 747       Vals.push_back(*i);
 748     break;
 749   }
 750   case Instruction::InsertValue: {
 751     Code = bitc::FUNC_CODE_INST_INSERTVAL;
 752     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
 753     PushValueAndType(I.getOperand(1), InstID, Vals, VE);
 754     const InsertValueInst *IVI = cast<InsertValueInst>(&I);
 755     for (const unsigned *i = IVI->idx_begin(), *e = IVI->idx_end(); i != e; ++i)
 756       Vals.push_back(*i);
 757     break;
 758   }
 759   case Instruction::Select:
 760     Code = bitc::FUNC_CODE_INST_VSELECT;
 761     PushValueAndType(I.getOperand(1), InstID, Vals, VE);
 762     Vals.push_back(VE.getValueID(I.getOperand(2)));
 763     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
 764     break;
 765   case Instruction::ExtractElement:
 766     Code = bitc::FUNC_CODE_INST_EXTRACTELT;
 767     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
 768     Vals.push_back(VE.getValueID(I.getOperand(1)));
 769     break;
 770   case Instruction::InsertElement:
 771     Code = bitc::FUNC_CODE_INST_INSERTELT;
 772     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
 773     Vals.push_back(VE.getValueID(I.getOperand(1)));
 774     Vals.push_back(VE.getValueID(I.getOperand(2)));
 775     break;
 776   case Instruction::ShuffleVector:
 777     Code = bitc::FUNC_CODE_INST_SHUFFLEVEC;
 778     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
 779     Vals.push_back(VE.getValueID(I.getOperand(1)));
 780     Vals.push_back(VE.getValueID(I.getOperand(2)));
 781     break;
 782   case Instruction::ICmp:
 783   case Instruction::FCmp:
 784   case Instruction::VICmp:
 785   case Instruction::VFCmp:
 786     if (I.getOpcode() == Instruction::ICmp
 787         || I.getOpcode() == Instruction::FCmp) {
 788       // compare returning Int1Ty or vector of Int1Ty
 789       Code = bitc::FUNC_CODE_INST_CMP2;
 790     } else {
 791       Code = bitc::FUNC_CODE_INST_CMP;
 792     }
 793     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
 794     Vals.push_back(VE.getValueID(I.getOperand(1)));
 795     Vals.push_back(cast<CmpInst>(I).getPredicate());
 796     break;
 797
 798   case Instruction::Ret:
 799     {
 800       Code = bitc::FUNC_CODE_INST_RET;
 801       unsigned NumOperands = I.getNumOperands();
 802       if (NumOperands == 0)
 803         AbbrevToUse = FUNCTION_INST_RET_VOID_ABBREV;
 804       else if (NumOperands == 1) {
 805         if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
 806           AbbrevToUse = FUNCTION_INST_RET_VAL_ABBREV;
 807       } else {
 808         for (unsigned i = 0, e = NumOperands; i != e; ++i)
 809           PushValueAndType(I.getOperand(i), InstID, Vals, VE);
 810       }
 811     }
 812     break;
 813   case Instruction::Br:
 814     {
 815       Code = bitc::FUNC_CODE_INST_BR;
 816       BranchInst &II(cast<BranchInst>(I));
 817       Vals.push_back(VE.getValueID(II.getSuccessor(0)));
 818       if (II.isConditional()) {
 819         Vals.push_back(VE.getValueID(II.getSuccessor(1)));
 820         Vals.push_back(VE.getValueID(II.getCondition()));
 821       }
 822     }
 823     break;
 824   case Instruction::Switch:
 825     Code = bitc::FUNC_CODE_INST_SWITCH;
 826     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));
 827     for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
 828       Vals.push_back(VE.getValueID(I.getOperand(i)));
 829     break;
 830   case Instruction::Invoke: {
 831     const InvokeInst *II = cast<InvokeInst>(&I);
 832     const Value *Callee(II->getCalledValue());
 833     const PointerType *PTy = cast<PointerType>(Callee->getType());
 834     const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
 835     Code = bitc::FUNC_CODE_INST_INVOKE;
 836
 837     Vals.push_back(VE.getAttributeID(II->getAttributes()));
 838     Vals.push_back(II->getCallingConv());
 839     Vals.push_back(VE.getValueID(II->getNormalDest()));
 840     Vals.push_back(VE.getValueID(II->getUnwindDest()));
 841     PushValueAndType(Callee, InstID, Vals, VE);
 842
 843     // Emit value #'s for the fixed parameters.
 844     for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
 845       Vals.push_back(VE.getValueID(I.getOperand(i+3)));  // fixed param.
 846
 847     // Emit type/value pairs for varargs params.
 848     if (FTy->isVarArg()) {
 849       for (unsigned i = 3+FTy->getNumParams(), e = I.getNumOperands();
 850            i != e; ++i)
 851         PushValueAndType(I.getOperand(i), InstID, Vals, VE); // vararg
 852     }
 853     break;
 854   }
 855   case Instruction::Unwind:
 856     Code = bitc::FUNC_CODE_INST_UNWIND;
 857     break;
 858   case Instruction::Unreachable:
 859     Code = bitc::FUNC_CODE_INST_UNREACHABLE;
 860     AbbrevToUse = FUNCTION_INST_UNREACHABLE_ABBREV;
 861     break;
 862
 863   case Instruction::PHI:
 864     Code = bitc::FUNC_CODE_INST_PHI;
 865     Vals.push_back(VE.getTypeID(I.getType()));
 866     for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
 867       Vals.push_back(VE.getValueID(I.getOperand(i)));
 868     break;
 869
 870   case Instruction::Malloc:
 871     Code = bitc::FUNC_CODE_INST_MALLOC;
 872     Vals.push_back(VE.getTypeID(I.getType()));
 873     Vals.push_back(VE.getValueID(I.getOperand(0))); // size.
 874     Vals.push_back(Log2_32(cast<MallocInst>(I).getAlignment())+1);
 875     break;
 876
 877   case Instruction::Free:
 878     Code = bitc::FUNC_CODE_INST_FREE;
 879     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
 880     break;
 881
 882   case Instruction::Alloca:
 883     Code = bitc::FUNC_CODE_INST_ALLOCA;
 884     Vals.push_back(VE.getTypeID(I.getType()));
 885     Vals.push_back(VE.getValueID(I.getOperand(0))); // size.
 886     Vals.push_back(Log2_32(cast<AllocaInst>(I).getAlignment())+1);
 887     break;
 888
 889   case Instruction::Load:
 890     Code = bitc::FUNC_CODE_INST_LOAD;
 891     if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))  // ptr
 892       AbbrevToUse = FUNCTION_INST_LOAD_ABBREV;
 893
 894     Vals.push_back(Log2_32(cast<LoadInst>(I).getAlignment())+1);
 895     Vals.push_back(cast<LoadInst>(I).isVolatile());
 896     break;
 897   case Instruction::Store:
 898     Code = bitc::FUNC_CODE_INST_STORE2;
 899     PushValueAndType(I.getOperand(1), InstID, Vals, VE);  // ptrty + ptr
 900     Vals.push_back(VE.getValueID(I.getOperand(0)));       // val.
 901     Vals.push_back(Log2_32(cast<StoreInst>(I).getAlignment())+1);
 902     Vals.push_back(cast<StoreInst>(I).isVolatile());
 903     break;
 904   case Instruction::Call: {
 905     const PointerType *PTy = cast<PointerType>(I.getOperand(0)->getType());
 906     const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
 907
 908     Code = bitc::FUNC_CODE_INST_CALL;
 909
 910     const CallInst *CI = cast<CallInst>(&I);
 911     Vals.push_back(VE.getAttributeID(CI->getAttributes()));
 912     Vals.push_back((CI->getCallingConv() << 1) | unsigned(CI->isTailCall()));
 913     PushValueAndType(CI->getOperand(0), InstID, Vals, VE);  // Callee
 914
 915     // Emit value #'s for the fixed parameters.
 916     for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
 917       Vals.push_back(VE.getValueID(I.getOperand(i+1)));  // fixed param.
 918
 919     // Emit type/value pairs for varargs params.
 920     if (FTy->isVarArg()) {
 921       unsigned NumVarargs = I.getNumOperands()-1-FTy->getNumParams();
 922       for (unsigned i = I.getNumOperands()-NumVarargs, e = I.getNumOperands();
 923            i != e; ++i)
 924         PushValueAndType(I.getOperand(i), InstID, Vals, VE);  // varargs
 925     }
 926     break;
 927   }
 928   case Instruction::VAArg:
 929     Code = bitc::FUNC_CODE_INST_VAARG;
 930     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));   // valistty
 931     Vals.push_back(VE.getValueID(I.getOperand(0))); // valist.
 932     Vals.push_back(VE.getTypeID(I.getType())); // restype.
 933     break;
 934   }
 935
 936   Stream.EmitRecord(Code, Vals, AbbrevToUse);
 937   Vals.clear();
 938 }
 939
 940 // Emit names for globals/functions etc.
 941 static void WriteValueSymbolTable(const ValueSymbolTable &VST,
 942                                   const ValueEnumerator &VE,
 943                                   BitstreamWriter &Stream) {
 944   if (VST.empty()) return;
 945   Stream.EnterSubblock(bitc::VALUE_SYMTAB_BLOCK_ID, 4);
 946
 947   // FIXME: Set up the abbrev, we know how many values there are!
 948   // FIXME: We know if the type names can use 7-bit ascii.
 949   SmallVector<unsigned, 64> NameVals;
 950
 951   for (ValueSymbolTable::const_iterator SI = VST.begin(), SE = VST.end();
 952        SI != SE; ++SI) {
 953
 954     const ValueName &Name = *SI;
 955
 956     // Figure out the encoding to use for the name.
 957     bool is7Bit = true;
 958     bool isChar6 = true;
 959     for (const char *C = Name.getKeyData(), *E = C+Name.getKeyLength();
 960          C != E; ++C) {
 961       if (isChar6)
 962         isChar6 = BitCodeAbbrevOp::isChar6(*C);
 963       if ((unsigned char)*C & 128) {
 964         is7Bit = false;
 965         break;  // don't bother scanning the rest.
 966       }
 967     }
 968
 969     unsigned AbbrevToUse = VST_ENTRY_8_ABBREV;
 970
 971     // VST_ENTRY:   [valueid, namechar x N]
 972     // VST_BBENTRY: [bbid, namechar x N]
 973     unsigned Code;
 974     if (isa<BasicBlock>(SI->getValue())) {
 975       Code = bitc::VST_CODE_BBENTRY;
 976       if (isChar6)
 977         AbbrevToUse = VST_BBENTRY_6_ABBREV;
 978     } else {
 979       Code = bitc::VST_CODE_ENTRY;
 980       if (isChar6)
 981         AbbrevToUse = VST_ENTRY_6_ABBREV;
 982       else if (is7Bit)
 983         AbbrevToUse = VST_ENTRY_7_ABBREV;
 984     }
 985
 986     NameVals.push_back(VE.getValueID(SI->getValue()));
 987     for (const char *P = Name.getKeyData(),
 988          *E = Name.getKeyData()+Name.getKeyLength(); P != E; ++P)
 989       NameVals.push_back((unsigned char)*P);
 990
 991     // Emit the finished record.
 992     Stream.EmitRecord(Code, NameVals, AbbrevToUse);
 993     NameVals.clear();
 994   }
 995   Stream.ExitBlock();
 996 }
 997
 998 /// WriteFunction - Emit a function body to the module stream.
 999 static void WriteFunction(const Function &F, ValueEnumerator &VE,
1000                           BitstreamWriter &Stream) {
1001   Stream.EnterSubblock(bitc::FUNCTION_BLOCK_ID, 4);
1002   VE.incorporateFunction(F);
1003
1004   SmallVector<unsigned, 64> Vals;
1005
1006   // Emit the number of basic blocks, so the reader can create them ahead of
1007   // time.
1008   Vals.push_back(VE.getBasicBlocks().size());
1009   Stream.EmitRecord(bitc::FUNC_CODE_DECLAREBLOCKS, Vals);
1010   Vals.clear();
1011
1012   // If there are function-local constants, emit them now.
1013   unsigned CstStart, CstEnd;
1014   VE.getFunctionConstantRange(CstStart, CstEnd);
1015   WriteConstants(CstStart, CstEnd, VE, Stream, false);
1016
1017   // Keep a running idea of what the instruction ID is.
1018   unsigned InstID = CstEnd;
1019
1020   // Finally, emit all the instructions, in order.
1021   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
1022     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
1023          I != E; ++I) {
1024       WriteInstruction(*I, InstID, VE, Stream, Vals);
1025       if (I->getType() != Type::VoidTy)
1026         ++InstID;
1027     }
1028
1029   // Emit names for all the instructions etc.
1030   WriteValueSymbolTable(F.getValueSymbolTable(), VE, Stream);
1031
1032   VE.purgeFunction();
1033   Stream.ExitBlock();
1034 }
1035
1036 /// WriteTypeSymbolTable - Emit a block for the specified type symtab.
1037 static void WriteTypeSymbolTable(const TypeSymbolTable &TST,
1038                                  const ValueEnumerator &VE,
1039                                  BitstreamWriter &Stream) {
1040   if (TST.empty()) return;
1041
1042   Stream.EnterSubblock(bitc::TYPE_SYMTAB_BLOCK_ID, 3);
1043
1044   // 7-bit fixed width VST_CODE_ENTRY strings.
1045   BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1046   Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
1047   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
1048                             Log2_32_Ceil(VE.getTypes().size()+1)));
1049   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1050   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
1051   unsigned V7Abbrev = Stream.EmitAbbrev(Abbv);
1052
1053   SmallVector<unsigned, 64> NameVals;
1054
1055   for (TypeSymbolTable::const_iterator TI = TST.begin(), TE = TST.end();
1056        TI != TE; ++TI) {
1057     // TST_ENTRY: [typeid, namechar x N]
1058     NameVals.push_back(VE.getTypeID(TI->second));
1059
1060     const std::string &Str = TI->first;
1061     bool is7Bit = true;
1062     for (unsigned i = 0, e = Str.size(); i != e; ++i) {
1063       NameVals.push_back((unsigned char)Str[i]);
1064       if (Str[i] & 128)
1065         is7Bit = false;
1066     }
1067
1068     // Emit the finished record.
1069     Stream.EmitRecord(bitc::VST_CODE_ENTRY, NameVals, is7Bit ? V7Abbrev : 0);
1070     NameVals.clear();
1071   }
1072
1073   Stream.ExitBlock();
1074 }
1075
1076 // Emit blockinfo, which defines the standard abbreviations etc.
1077 static void WriteBlockInfo(const ValueEnumerator &VE, BitstreamWriter &Stream) {
1078   // We only want to emit block info records for blocks that have multiple
1079   // instances: CONSTANTS_BLOCK, FUNCTION_BLOCK and VALUE_SYMTAB_BLOCK.  Other
1080   // blocks can defined their abbrevs inline.
1081   Stream.EnterBlockInfoBlock(2);
1082
1083   { // 8-bit fixed-width VST_ENTRY/VST_BBENTRY strings.
1084     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1085     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3));
1086     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1087     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1088     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
1089     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1090                                    Abbv) != VST_ENTRY_8_ABBREV)
1091       assert(0 && "Unexpected abbrev ordering!");
1092   }
1093
1094   { // 7-bit fixed width VST_ENTRY strings.
1095     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1096     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
1097     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1098     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1099     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
1100     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1101                                    Abbv) != VST_ENTRY_7_ABBREV)
1102       assert(0 && "Unexpected abbrev ordering!");
1103   }
1104   { // 6-bit char6 VST_ENTRY strings.
1105     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1106     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
1107     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1108     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1109     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
1110     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1111                                    Abbv) != VST_ENTRY_6_ABBREV)
1112       assert(0 && "Unexpected abbrev ordering!");
1113   }
1114   { // 6-bit char6 VST_BBENTRY strings.
1115     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1116     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_BBENTRY));
1117     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1118     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1119     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
1120     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1121                                    Abbv) != VST_BBENTRY_6_ABBREV)
1122       assert(0 && "Unexpected abbrev ordering!");
1123   }
1124
1125
1126
1127   { // SETTYPE abbrev for CONSTANTS_BLOCK.
1128     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1129     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_SETTYPE));
1130     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
1131                               Log2_32_Ceil(VE.getTypes().size()+1)));
1132     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1133                                    Abbv) != CONSTANTS_SETTYPE_ABBREV)
1134       assert(0 && "Unexpected abbrev ordering!");
1135   }
1136
1137   { // INTEGER abbrev for CONSTANTS_BLOCK.
1138     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1139     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_INTEGER));
1140     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1141     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1142                                    Abbv) != CONSTANTS_INTEGER_ABBREV)
1143       assert(0 && "Unexpected abbrev ordering!");
1144   }
1145
1146   { // CE_CAST abbrev for CONSTANTS_BLOCK.
1147     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1148     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CE_CAST));
1149     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));  // cast opc
1150     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,       // typeid
1151                               Log2_32_Ceil(VE.getTypes().size()+1)));
1152     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));    // value id
1153
1154     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1155                                    Abbv) != CONSTANTS_CE_CAST_Abbrev)
1156       assert(0 && "Unexpected abbrev ordering!");
1157   }
1158   { // NULL abbrev for CONSTANTS_BLOCK.
1159     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1160     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_NULL));
1161     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1162                                    Abbv) != CONSTANTS_NULL_Abbrev)
1163       assert(0 && "Unexpected abbrev ordering!");
1164   }
1165
1166   // FIXME: This should only use space for first class types!
1167
1168   { // INST_LOAD abbrev for FUNCTION_BLOCK.
1169     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1170     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_LOAD));
1171     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Ptr
1172     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // Align
1173     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // volatile
1174     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1175                                    Abbv) != FUNCTION_INST_LOAD_ABBREV)
1176       assert(0 && "Unexpected abbrev ordering!");
1177   }
1178   { // INST_BINOP abbrev for FUNCTION_BLOCK.
1179     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1180     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_BINOP));
1181     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
1182     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // RHS
1183     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
1184     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1185                                    Abbv) != FUNCTION_INST_BINOP_ABBREV)
1186       assert(0 && "Unexpected abbrev ordering!");
1187   }
1188   { // INST_CAST abbrev for FUNCTION_BLOCK.
1189     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1190     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_CAST));
1191     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));    // OpVal
1192     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,       // dest ty
1193                               Log2_32_Ceil(VE.getTypes().size()+1)));
1194     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));  // opc
1195     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1196                                    Abbv) != FUNCTION_INST_CAST_ABBREV)
1197       assert(0 && "Unexpected abbrev ordering!");
1198   }
1199
1200   { // INST_RET abbrev for FUNCTION_BLOCK.
1201     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1202     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_RET));
1203     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1204                                    Abbv) != FUNCTION_INST_RET_VOID_ABBREV)
1205       assert(0 && "Unexpected abbrev ordering!");
1206   }
1207   { // INST_RET abbrev for FUNCTION_BLOCK.
1208     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1209     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_RET));
1210     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // ValID
1211     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1212                                    Abbv) != FUNCTION_INST_RET_VAL_ABBREV)
1213       assert(0 && "Unexpected abbrev ordering!");
1214   }
1215   { // INST_UNREACHABLE abbrev for FUNCTION_BLOCK.
1216     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1217     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_UNREACHABLE));
1218     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1219                                    Abbv) != FUNCTION_INST_UNREACHABLE_ABBREV)
1220       assert(0 && "Unexpected abbrev ordering!");
1221   }
1222
1223   Stream.ExitBlock();
1224 }
1225
1226
1227 /// WriteModule - Emit the specified module to the bitstream.
1228 static void WriteModule(const Module *M, BitstreamWriter &Stream) {
1229   Stream.EnterSubblock(bitc::MODULE_BLOCK_ID, 3);
1230
1231   // Emit the version number if it is non-zero.
1232   if (CurVersion) {
1233     SmallVector<unsigned, 1> Vals;
1234     Vals.push_back(CurVersion);
1235     Stream.EmitRecord(bitc::MODULE_CODE_VERSION, Vals);
1236   }
1237
1238   // Analyze the module, enumerating globals, functions, etc.
1239   ValueEnumerator VE(M);
1240
1241   // Emit blockinfo, which defines the standard abbreviations etc.
1242   WriteBlockInfo(VE, Stream);
1243
1244   // Emit information about parameter attributes.
1245   WriteAttributeTable(VE, Stream);
1246
1247   // Emit information describing all of the types in the module.
1248   WriteTypeTable(VE, Stream);
1249
1250   // Emit top-level description of module, including target triple, inline asm,
1251   // descriptors for global variables, and function prototype info.
1252   WriteModuleInfo(M, VE, Stream);
1253
1254   // Emit constants.
1255   WriteModuleConstants(VE, Stream);
1256
1257   // If we have any aggregate values in the value table, purge them - these can
1258   // only be used to initialize global variables.  Doing so makes the value
1259   // namespace smaller for code in functions.
1260   int NumNonAggregates = VE.PurgeAggregateValues();
1261   if (NumNonAggregates != -1) {
1262     SmallVector<unsigned, 1> Vals;
1263     Vals.push_back(NumNonAggregates);
1264     Stream.EmitRecord(bitc::MODULE_CODE_PURGEVALS, Vals);
1265   }
1266
1267   // Emit function bodies.
1268   for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I)
1269     if (!I->isDeclaration())
1270       WriteFunction(*I, VE, Stream);
1271
1272   // Emit the type symbol table information.
1273   WriteTypeSymbolTable(M->getTypeSymbolTable(), VE, Stream);
1274
1275   // Emit names for globals/functions etc.
1276   WriteValueSymbolTable(M->getValueSymbolTable(), VE, Stream);
1277
1278   Stream.ExitBlock();
1279 }
1280
1281 /// EmitDarwinBCHeader - If generating a bc file on darwin, we have to emit a
1282 /// header and trailer to make it compatible with the system archiver.  To do
1283 /// this we emit the following header, and then emit a trailer that pads the
1284 /// file out to be a multiple of 16 bytes.
1285 ///
1286 /// struct bc_header {
1287 ///   uint32_t Magic;         // 0x0B17C0DE
1288 ///   uint32_t Version;       // Version, currently always 0.
1289 ///   uint32_t BitcodeOffset; // Offset to traditional bitcode file.
1290 ///   uint32_t BitcodeSize;   // Size of traditional bitcode file.
1291 ///   uint32_t CPUType;       // CPU specifier.
1292 ///   ... potentially more later ...
1293 /// };
1294 enum {
1295   DarwinBCSizeFieldOffset = 3*4, // Offset to bitcode_size.
1296   DarwinBCHeaderSize = 5*4
1297 };
1298
1299 static void EmitDarwinBCHeader(BitstreamWriter &Stream,
1300                                const std::string &TT) {
1301   unsigned CPUType = ~0U;
1302
1303   // Match x86_64-*, i[3-9]86-*, powerpc-*, powerpc64-*.  The CPUType is a
1304   // magic number from /usr/include/mach/machine.h.  It is ok to reproduce the
1305   // specific constants here because they are implicitly part of the Darwin ABI.
1306   enum {
1307     DARWIN_CPU_ARCH_ABI64      = 0x01000000,
1308     DARWIN_CPU_TYPE_X86        = 7,
1309     DARWIN_CPU_TYPE_POWERPC    = 18
1310   };
1311
1312   if (TT.find("x86_64-") == 0)
1313     CPUType = DARWIN_CPU_TYPE_X86 | DARWIN_CPU_ARCH_ABI64;
1314   else if (TT.size() >= 5 && TT[0] == 'i' && TT[2] == '8' && TT[3] == '6' &&
1315            TT[4] == '-' && TT[1] - '3' < 6)
1316     CPUType = DARWIN_CPU_TYPE_X86;
1317   else if (TT.find("powerpc-") == 0)
1318     CPUType = DARWIN_CPU_TYPE_POWERPC;
1319   else if (TT.find("powerpc64-") == 0)
1320     CPUType = DARWIN_CPU_TYPE_POWERPC | DARWIN_CPU_ARCH_ABI64;
1321
1322   // Traditional Bitcode starts after header.
1323   unsigned BCOffset = DarwinBCHeaderSize;
1324
1325   Stream.Emit(0x0B17C0DE, 32);
1326   Stream.Emit(0         , 32);  // Version.
1327   Stream.Emit(BCOffset  , 32);
1328   Stream.Emit(0         , 32);  // Filled in later.
1329   Stream.Emit(CPUType   , 32);
1330 }
1331
1332 /// EmitDarwinBCTrailer - Emit the darwin epilog after the bitcode file and
1333 /// finalize the header.
1334 static void EmitDarwinBCTrailer(BitstreamWriter &Stream, unsigned BufferSize) {
1335   // Update the size field in the header.
1336   Stream.BackpatchWord(DarwinBCSizeFieldOffset, BufferSize-DarwinBCHeaderSize);
1337
1338   // If the file is not a multiple of 16 bytes, insert dummy padding.
1339   while (BufferSize & 15) {
1340     Stream.Emit(0, 8);
1341     ++BufferSize;
1342   }
1343 }
1344
1345
1346 /// WriteBitcodeToFile - Write the specified module to the specified output
1347 /// stream.
1348 void llvm::WriteBitcodeToFile(const Module *M, std::ostream &Out) {
1349   raw_os_ostream RawOut(Out);
1350   // If writing to stdout, set binary mode.
1351   if (llvm::cout == Out)
1352     sys::Program::ChangeStdoutToBinary();
1353   WriteBitcodeToFile(M, RawOut);
1354 }
1355
1356 /// WriteBitcodeToFile - Write the specified module to the specified output
1357 /// stream.
1358 void llvm::WriteBitcodeToFile(const Module *M, raw_ostream &Out) {
1359   std::vector<unsigned char> Buffer;
1360   BitstreamWriter Stream(Buffer);
1361
1362   Buffer.reserve(256*1024);
1363
1364   WriteBitcodeToStream( M, Stream );
1365
1366   // If writing to stdout, set binary mode.
1367   if (&llvm::outs() == &Out)
1368     sys::Program::ChangeStdoutToBinary();
1369
1370   // Write the generated bitstream to "Out".
1371   Out.write((char*)&Buffer.front(), Buffer.size());
1372
1373   // Make sure it hits disk now.
1374   Out.flush();
1375 }
1376
1377 /// WriteBitcodeToStream - Write the specified module to the specified output
1378 /// stream.
1379 void llvm::WriteBitcodeToStream(const Module *M, BitstreamWriter &Stream) {
1380   // If this is darwin, emit a file header and trailer if needed.
1381   bool isDarwin = M->getTargetTriple().find("-darwin") != std::string::npos;
1382   if (isDarwin)
1383     EmitDarwinBCHeader(Stream, M->getTargetTriple());
1384
1385   // Emit the file header.
1386   Stream.Emit((unsigned)'B', 8);
1387   Stream.Emit((unsigned)'C', 8);
1388   Stream.Emit(0x0, 4);
1389   Stream.Emit(0xC, 4);
1390   Stream.Emit(0xE, 4);
1391   Stream.Emit(0xD, 4);
1392
1393   // Emit the module.
1394   WriteModule(M, Stream);
1395
1396   if (isDarwin)
1397     EmitDarwinBCTrailer(Stream, Stream.getBuffer().size());
1398 }