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/Operator.h"
  24 #include "llvm/ValueSymbolTable.h"
  25 #include "llvm/ADT/Triple.h"
  26 #include "llvm/Support/CommandLine.h"
  27 #include "llvm/Support/ErrorHandling.h"
  28 #include "llvm/Support/MathExtras.h"
  29 #include "llvm/Support/raw_ostream.h"
  30 #include "llvm/Support/Program.h"
  31 #include <cctype>
  32 #include <map>
  33 using namespace llvm;
  34
  35 static cl::opt<bool>
  36 EnablePreserveUseListOrdering("enable-bc-uselist-preserve",
  37                               cl::desc("Turn on experimental support for "
  38                                        "use-list order preservation."),
  39                               cl::init(false), cl::Hidden);
  40
  41 /// These are manifest constants used by the bitcode writer. They do not need to
  42 /// be kept in sync with the reader, but need to be consistent within this file.
  43 enum {
  44   // VALUE_SYMTAB_BLOCK abbrev id's.
  45   VST_ENTRY_8_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
  46   VST_ENTRY_7_ABBREV,
  47   VST_ENTRY_6_ABBREV,
  48   VST_BBENTRY_6_ABBREV,
  49
  50   // CONSTANTS_BLOCK abbrev id's.
  51   CONSTANTS_SETTYPE_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
  52   CONSTANTS_INTEGER_ABBREV,
  53   CONSTANTS_CE_CAST_Abbrev,
  54   CONSTANTS_NULL_Abbrev,
  55
  56   // FUNCTION_BLOCK abbrev id's.
  57   FUNCTION_INST_LOAD_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
  58   FUNCTION_INST_BINOP_ABBREV,
  59   FUNCTION_INST_BINOP_FLAGS_ABBREV,
  60   FUNCTION_INST_CAST_ABBREV,
  61   FUNCTION_INST_RET_VOID_ABBREV,
  62   FUNCTION_INST_RET_VAL_ABBREV,
  63   FUNCTION_INST_UNREACHABLE_ABBREV,
  64
  65   // SwitchInst Magic
  66   SWITCH_INST_MAGIC = 0x4B5 // May 2012 => 1205 => Hex
  67 };
  68
  69 static unsigned GetEncodedCastOpcode(unsigned Opcode) {
  70   switch (Opcode) {
  71   default: llvm_unreachable("Unknown cast instruction!");
  72   case Instruction::Trunc   : return bitc::CAST_TRUNC;
  73   case Instruction::ZExt    : return bitc::CAST_ZEXT;
  74   case Instruction::SExt    : return bitc::CAST_SEXT;
  75   case Instruction::FPToUI  : return bitc::CAST_FPTOUI;
  76   case Instruction::FPToSI  : return bitc::CAST_FPTOSI;
  77   case Instruction::UIToFP  : return bitc::CAST_UITOFP;
  78   case Instruction::SIToFP  : return bitc::CAST_SITOFP;
  79   case Instruction::FPTrunc : return bitc::CAST_FPTRUNC;
  80   case Instruction::FPExt   : return bitc::CAST_FPEXT;
  81   case Instruction::PtrToInt: return bitc::CAST_PTRTOINT;
  82   case Instruction::IntToPtr: return bitc::CAST_INTTOPTR;
  83   case Instruction::BitCast : return bitc::CAST_BITCAST;
  84   }
  85 }
  86
  87 static unsigned GetEncodedBinaryOpcode(unsigned Opcode) {
  88   switch (Opcode) {
  89   default: llvm_unreachable("Unknown binary instruction!");
  90   case Instruction::Add:
  91   case Instruction::FAdd: return bitc::BINOP_ADD;
  92   case Instruction::Sub:
  93   case Instruction::FSub: return bitc::BINOP_SUB;
  94   case Instruction::Mul:
  95   case Instruction::FMul: return bitc::BINOP_MUL;
  96   case Instruction::UDiv: return bitc::BINOP_UDIV;
  97   case Instruction::FDiv:
  98   case Instruction::SDiv: return bitc::BINOP_SDIV;
  99   case Instruction::URem: return bitc::BINOP_UREM;
 100   case Instruction::FRem:
 101   case Instruction::SRem: return bitc::BINOP_SREM;
 102   case Instruction::Shl:  return bitc::BINOP_SHL;
 103   case Instruction::LShr: return bitc::BINOP_LSHR;
 104   case Instruction::AShr: return bitc::BINOP_ASHR;
 105   case Instruction::And:  return bitc::BINOP_AND;
 106   case Instruction::Or:   return bitc::BINOP_OR;
 107   case Instruction::Xor:  return bitc::BINOP_XOR;
 108   }
 109 }
 110
 111 static unsigned GetEncodedRMWOperation(AtomicRMWInst::BinOp Op) {
 112   switch (Op) {
 113   default: llvm_unreachable("Unknown RMW operation!");
 114   case AtomicRMWInst::Xchg: return bitc::RMW_XCHG;
 115   case AtomicRMWInst::Add: return bitc::RMW_ADD;
 116   case AtomicRMWInst::Sub: return bitc::RMW_SUB;
 117   case AtomicRMWInst::And: return bitc::RMW_AND;
 118   case AtomicRMWInst::Nand: return bitc::RMW_NAND;
 119   case AtomicRMWInst::Or: return bitc::RMW_OR;
 120   case AtomicRMWInst::Xor: return bitc::RMW_XOR;
 121   case AtomicRMWInst::Max: return bitc::RMW_MAX;
 122   case AtomicRMWInst::Min: return bitc::RMW_MIN;
 123   case AtomicRMWInst::UMax: return bitc::RMW_UMAX;
 124   case AtomicRMWInst::UMin: return bitc::RMW_UMIN;
 125   }
 126 }
 127
 128 static unsigned GetEncodedOrdering(AtomicOrdering Ordering) {
 129   switch (Ordering) {
 130   case NotAtomic: return bitc::ORDERING_NOTATOMIC;
 131   case Unordered: return bitc::ORDERING_UNORDERED;
 132   case Monotonic: return bitc::ORDERING_MONOTONIC;
 133   case Acquire: return bitc::ORDERING_ACQUIRE;
 134   case Release: return bitc::ORDERING_RELEASE;
 135   case AcquireRelease: return bitc::ORDERING_ACQREL;
 136   case SequentiallyConsistent: return bitc::ORDERING_SEQCST;
 137   }
 138   llvm_unreachable("Invalid ordering");
 139 }
 140
 141 static unsigned GetEncodedSynchScope(SynchronizationScope SynchScope) {
 142   switch (SynchScope) {
 143   case SingleThread: return bitc::SYNCHSCOPE_SINGLETHREAD;
 144   case CrossThread: return bitc::SYNCHSCOPE_CROSSTHREAD;
 145   }
 146   llvm_unreachable("Invalid synch scope");
 147 }
 148
 149 static void WriteStringRecord(unsigned Code, StringRef Str,
 150                               unsigned AbbrevToUse, BitstreamWriter &Stream) {
 151   SmallVector<unsigned, 64> Vals;
 152
 153   // Code: [strchar x N]
 154   for (unsigned i = 0, e = Str.size(); i != e; ++i) {
 155     if (AbbrevToUse && !BitCodeAbbrevOp::isChar6(Str[i]))
 156       AbbrevToUse = 0;
 157     Vals.push_back(Str[i]);
 158   }
 159
 160   // Emit the finished record.
 161   Stream.EmitRecord(Code, Vals, AbbrevToUse);
 162 }
 163
 164 // Emit information about parameter attributes.
 165 static void WriteAttributeTable(const ValueEnumerator &VE,
 166                                 BitstreamWriter &Stream) {
 167   const std::vector<AttrListPtr> &Attrs = VE.getAttributes();
 168   if (Attrs.empty()) return;
 169
 170   Stream.EnterSubblock(bitc::PARAMATTR_BLOCK_ID, 3);
 171
 172   SmallVector<uint64_t, 64> Record;
 173   for (unsigned i = 0, e = Attrs.size(); i != e; ++i) {
 174     const AttrListPtr &A = Attrs[i];
 175     for (unsigned i = 0, e = A.getNumSlots(); i != e; ++i) {
 176       const AttributeWithIndex &PAWI = A.getSlot(i);
 177       Record.push_back(PAWI.Index);
 178       Record.push_back(Attributes::encodeLLVMAttributesForBitcode(PAWI.Attrs));
 179     }
 180
 181     Stream.EmitRecord(bitc::PARAMATTR_CODE_ENTRY, Record);
 182     Record.clear();
 183   }
 184
 185   Stream.ExitBlock();
 186 }
 187
 188 /// WriteTypeTable - Write out the type table for a module.
 189 static void WriteTypeTable(const ValueEnumerator &VE, BitstreamWriter &Stream) {
 190   const ValueEnumerator::TypeList &TypeList = VE.getTypes();
 191
 192   Stream.EnterSubblock(bitc::TYPE_BLOCK_ID_NEW, 4 /*count from # abbrevs */);
 193   SmallVector<uint64_t, 64> TypeVals;
 194
 195   uint64_t NumBits = Log2_32_Ceil(VE.getTypes().size()+1);
 196
 197   // Abbrev for TYPE_CODE_POINTER.
 198   BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 199   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_POINTER));
 200   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
 201   Abbv->Add(BitCodeAbbrevOp(0));  // Addrspace = 0
 202   unsigned PtrAbbrev = Stream.EmitAbbrev(Abbv);
 203
 204   // Abbrev for TYPE_CODE_FUNCTION.
 205   Abbv = new BitCodeAbbrev();
 206   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_FUNCTION));
 207   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // isvararg
 208   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 209   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
 210
 211   unsigned FunctionAbbrev = Stream.EmitAbbrev(Abbv);
 212
 213   // Abbrev for TYPE_CODE_STRUCT_ANON.
 214   Abbv = new BitCodeAbbrev();
 215   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_ANON));
 216   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // ispacked
 217   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 218   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
 219
 220   unsigned StructAnonAbbrev = Stream.EmitAbbrev(Abbv);
 221
 222   // Abbrev for TYPE_CODE_STRUCT_NAME.
 223   Abbv = new BitCodeAbbrev();
 224   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_NAME));
 225   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 226   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
 227   unsigned StructNameAbbrev = Stream.EmitAbbrev(Abbv);
 228
 229   // Abbrev for TYPE_CODE_STRUCT_NAMED.
 230   Abbv = new BitCodeAbbrev();
 231   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_NAMED));
 232   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // ispacked
 233   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 234   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
 235
 236   unsigned StructNamedAbbrev = Stream.EmitAbbrev(Abbv);
 237
 238   // Abbrev for TYPE_CODE_ARRAY.
 239   Abbv = new BitCodeAbbrev();
 240   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_ARRAY));
 241   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));   // size
 242   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
 243
 244   unsigned ArrayAbbrev = Stream.EmitAbbrev(Abbv);
 245
 246   // Emit an entry count so the reader can reserve space.
 247   TypeVals.push_back(TypeList.size());
 248   Stream.EmitRecord(bitc::TYPE_CODE_NUMENTRY, TypeVals);
 249   TypeVals.clear();
 250
 251   // Loop over all of the types, emitting each in turn.
 252   for (unsigned i = 0, e = TypeList.size(); i != e; ++i) {
 253     Type *T = TypeList[i];
 254     int AbbrevToUse = 0;
 255     unsigned Code = 0;
 256
 257     switch (T->getTypeID()) {
 258     default: llvm_unreachable("Unknown type!");
 259     case Type::VoidTyID:      Code = bitc::TYPE_CODE_VOID;      break;
 260     case Type::HalfTyID:      Code = bitc::TYPE_CODE_HALF;      break;
 261     case Type::FloatTyID:     Code = bitc::TYPE_CODE_FLOAT;     break;
 262     case Type::DoubleTyID:    Code = bitc::TYPE_CODE_DOUBLE;    break;
 263     case Type::X86_FP80TyID:  Code = bitc::TYPE_CODE_X86_FP80;  break;
 264     case Type::FP128TyID:     Code = bitc::TYPE_CODE_FP128;     break;
 265     case Type::PPC_FP128TyID: Code = bitc::TYPE_CODE_PPC_FP128; break;
 266     case Type::LabelTyID:     Code = bitc::TYPE_CODE_LABEL;     break;
 267     case Type::MetadataTyID:  Code = bitc::TYPE_CODE_METADATA;  break;
 268     case Type::X86_MMXTyID:   Code = bitc::TYPE_CODE_X86_MMX;   break;
 269     case Type::IntegerTyID:
 270       // INTEGER: [width]
 271       Code = bitc::TYPE_CODE_INTEGER;
 272       TypeVals.push_back(cast<IntegerType>(T)->getBitWidth());
 273       break;
 274     case Type::PointerTyID: {
 275       PointerType *PTy = cast<PointerType>(T);
 276       // POINTER: [pointee type, address space]
 277       Code = bitc::TYPE_CODE_POINTER;
 278       TypeVals.push_back(VE.getTypeID(PTy->getElementType()));
 279       unsigned AddressSpace = PTy->getAddressSpace();
 280       TypeVals.push_back(AddressSpace);
 281       if (AddressSpace == 0) AbbrevToUse = PtrAbbrev;
 282       break;
 283     }
 284     case Type::FunctionTyID: {
 285       FunctionType *FT = cast<FunctionType>(T);
 286       // FUNCTION: [isvararg, retty, paramty x N]
 287       Code = bitc::TYPE_CODE_FUNCTION;
 288       TypeVals.push_back(FT->isVarArg());
 289       TypeVals.push_back(VE.getTypeID(FT->getReturnType()));
 290       for (unsigned i = 0, e = FT->getNumParams(); i != e; ++i)
 291         TypeVals.push_back(VE.getTypeID(FT->getParamType(i)));
 292       AbbrevToUse = FunctionAbbrev;
 293       break;
 294     }
 295     case Type::StructTyID: {
 296       StructType *ST = cast<StructType>(T);
 297       // STRUCT: [ispacked, eltty x N]
 298       TypeVals.push_back(ST->isPacked());
 299       // Output all of the element types.
 300       for (StructType::element_iterator I = ST->element_begin(),
 301            E = ST->element_end(); I != E; ++I)
 302         TypeVals.push_back(VE.getTypeID(*I));
 303
 304       if (ST->isLiteral()) {
 305         Code = bitc::TYPE_CODE_STRUCT_ANON;
 306         AbbrevToUse = StructAnonAbbrev;
 307       } else {
 308         if (ST->isOpaque()) {
 309           Code = bitc::TYPE_CODE_OPAQUE;
 310         } else {
 311           Code = bitc::TYPE_CODE_STRUCT_NAMED;
 312           AbbrevToUse = StructNamedAbbrev;
 313         }
 314
 315         // Emit the name if it is present.
 316         if (!ST->getName().empty())
 317           WriteStringRecord(bitc::TYPE_CODE_STRUCT_NAME, ST->getName(),
 318                             StructNameAbbrev, Stream);
 319       }
 320       break;
 321     }
 322     case Type::ArrayTyID: {
 323       ArrayType *AT = cast<ArrayType>(T);
 324       // ARRAY: [numelts, eltty]
 325       Code = bitc::TYPE_CODE_ARRAY;
 326       TypeVals.push_back(AT->getNumElements());
 327       TypeVals.push_back(VE.getTypeID(AT->getElementType()));
 328       AbbrevToUse = ArrayAbbrev;
 329       break;
 330     }
 331     case Type::VectorTyID: {
 332       VectorType *VT = cast<VectorType>(T);
 333       // VECTOR [numelts, eltty]
 334       Code = bitc::TYPE_CODE_VECTOR;
 335       TypeVals.push_back(VT->getNumElements());
 336       TypeVals.push_back(VE.getTypeID(VT->getElementType()));
 337       break;
 338     }
 339     }
 340
 341     // Emit the finished record.
 342     Stream.EmitRecord(Code, TypeVals, AbbrevToUse);
 343     TypeVals.clear();
 344   }
 345
 346   Stream.ExitBlock();
 347 }
 348
 349 static unsigned getEncodedLinkage(const GlobalValue *GV) {
 350   switch (GV->getLinkage()) {
 351   case GlobalValue::ExternalLinkage:                 return 0;
 352   case GlobalValue::WeakAnyLinkage:                  return 1;
 353   case GlobalValue::AppendingLinkage:                return 2;
 354   case GlobalValue::InternalLinkage:                 return 3;
 355   case GlobalValue::LinkOnceAnyLinkage:              return 4;
 356   case GlobalValue::DLLImportLinkage:                return 5;
 357   case GlobalValue::DLLExportLinkage:                return 6;
 358   case GlobalValue::ExternalWeakLinkage:             return 7;
 359   case GlobalValue::CommonLinkage:                   return 8;
 360   case GlobalValue::PrivateLinkage:                  return 9;
 361   case GlobalValue::WeakODRLinkage:                  return 10;
 362   case GlobalValue::LinkOnceODRLinkage:              return 11;
 363   case GlobalValue::AvailableExternallyLinkage:      return 12;
 364   case GlobalValue::LinkerPrivateLinkage:            return 13;
 365   case GlobalValue::LinkerPrivateWeakLinkage:        return 14;
 366   case GlobalValue::LinkOnceODRAutoHideLinkage:      return 15;
 367   }
 368   llvm_unreachable("Invalid linkage");
 369 }
 370
 371 static unsigned getEncodedVisibility(const GlobalValue *GV) {
 372   switch (GV->getVisibility()) {
 373   case GlobalValue::DefaultVisibility:   return 0;
 374   case GlobalValue::HiddenVisibility:    return 1;
 375   case GlobalValue::ProtectedVisibility: return 2;
 376   }
 377   llvm_unreachable("Invalid visibility");
 378 }
 379
 380 static unsigned getEncodedThreadLocalMode(const GlobalVariable *GV) {
 381   switch (GV->getThreadLocalMode()) {
 382     case GlobalVariable::NotThreadLocal:         return 0;
 383     case GlobalVariable::GeneralDynamicTLSModel: return 1;
 384     case GlobalVariable::LocalDynamicTLSModel:   return 2;
 385     case GlobalVariable::InitialExecTLSModel:    return 3;
 386     case GlobalVariable::LocalExecTLSModel:      return 4;
 387   }
 388   llvm_unreachable("Invalid TLS model");
 389 }
 390
 391 // Emit top-level description of module, including target triple, inline asm,
 392 // descriptors for global variables, and function prototype info.
 393 static void WriteModuleInfo(const Module *M, const ValueEnumerator &VE,
 394                             BitstreamWriter &Stream) {
 395   // Emit various pieces of data attached to a module.
 396   if (!M->getTargetTriple().empty())
 397     WriteStringRecord(bitc::MODULE_CODE_TRIPLE, M->getTargetTriple(),
 398                       0/*TODO*/, Stream);
 399   if (!M->getDataLayout().empty())
 400     WriteStringRecord(bitc::MODULE_CODE_DATALAYOUT, M->getDataLayout(),
 401                       0/*TODO*/, Stream);
 402   if (!M->getModuleInlineAsm().empty())
 403     WriteStringRecord(bitc::MODULE_CODE_ASM, M->getModuleInlineAsm(),
 404                       0/*TODO*/, Stream);
 405
 406   // Emit information about sections and GC, computing how many there are. Also
 407   // compute the maximum alignment value.
 408   std::map<std::string, unsigned> SectionMap;
 409   std::map<std::string, unsigned> GCMap;
 410   unsigned MaxAlignment = 0;
 411   unsigned MaxGlobalType = 0;
 412   for (Module::const_global_iterator GV = M->global_begin(),E = M->global_end();
 413        GV != E; ++GV) {
 414     MaxAlignment = std::max(MaxAlignment, GV->getAlignment());
 415     MaxGlobalType = std::max(MaxGlobalType, VE.getTypeID(GV->getType()));
 416     if (GV->hasSection()) {
 417       // Give section names unique ID's.
 418       unsigned &Entry = SectionMap[GV->getSection()];
 419       if (!Entry) {
 420         WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, GV->getSection(),
 421                           0/*TODO*/, Stream);
 422         Entry = SectionMap.size();
 423       }
 424     }
 425   }
 426   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F) {
 427     MaxAlignment = std::max(MaxAlignment, F->getAlignment());
 428     if (F->hasSection()) {
 429       // Give section names unique ID's.
 430       unsigned &Entry = SectionMap[F->getSection()];
 431       if (!Entry) {
 432         WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, F->getSection(),
 433                           0/*TODO*/, Stream);
 434         Entry = SectionMap.size();
 435       }
 436     }
 437     if (F->hasGC()) {
 438       // Same for GC names.
 439       unsigned &Entry = GCMap[F->getGC()];
 440       if (!Entry) {
 441         WriteStringRecord(bitc::MODULE_CODE_GCNAME, F->getGC(),
 442                           0/*TODO*/, Stream);
 443         Entry = GCMap.size();
 444       }
 445     }
 446   }
 447
 448   // Emit abbrev for globals, now that we know # sections and max alignment.
 449   unsigned SimpleGVarAbbrev = 0;
 450   if (!M->global_empty()) {
 451     // Add an abbrev for common globals with no visibility or thread localness.
 452     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 453     Abbv->Add(BitCodeAbbrevOp(bitc::MODULE_CODE_GLOBALVAR));
 454     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 455                               Log2_32_Ceil(MaxGlobalType+1)));
 456     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));      // Constant.
 457     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));        // Initializer.
 458     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));      // Linkage.
 459     if (MaxAlignment == 0)                                      // Alignment.
 460       Abbv->Add(BitCodeAbbrevOp(0));
 461     else {
 462       unsigned MaxEncAlignment = Log2_32(MaxAlignment)+1;
 463       Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 464                                Log2_32_Ceil(MaxEncAlignment+1)));
 465     }
 466     if (SectionMap.empty())                                    // Section.
 467       Abbv->Add(BitCodeAbbrevOp(0));
 468     else
 469       Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 470                                Log2_32_Ceil(SectionMap.size()+1)));
 471     // Don't bother emitting vis + thread local.
 472     SimpleGVarAbbrev = Stream.EmitAbbrev(Abbv);
 473   }
 474
 475   // Emit the global variable information.
 476   SmallVector<unsigned, 64> Vals;
 477   for (Module::const_global_iterator GV = M->global_begin(),E = M->global_end();
 478        GV != E; ++GV) {
 479     unsigned AbbrevToUse = 0;
 480
 481     // GLOBALVAR: [type, isconst, initid,
 482     //             linkage, alignment, section, visibility, threadlocal,
 483     //             unnamed_addr]
 484     Vals.push_back(VE.getTypeID(GV->getType()));
 485     Vals.push_back(GV->isConstant());
 486     Vals.push_back(GV->isDeclaration() ? 0 :
 487                    (VE.getValueID(GV->getInitializer()) + 1));
 488     Vals.push_back(getEncodedLinkage(GV));
 489     Vals.push_back(Log2_32(GV->getAlignment())+1);
 490     Vals.push_back(GV->hasSection() ? SectionMap[GV->getSection()] : 0);
 491     if (GV->isThreadLocal() ||
 492         GV->getVisibility() != GlobalValue::DefaultVisibility ||
 493         GV->hasUnnamedAddr()) {
 494       Vals.push_back(getEncodedVisibility(GV));
 495       Vals.push_back(getEncodedThreadLocalMode(GV));
 496       Vals.push_back(GV->hasUnnamedAddr());
 497     } else {
 498       AbbrevToUse = SimpleGVarAbbrev;
 499     }
 500
 501     Stream.EmitRecord(bitc::MODULE_CODE_GLOBALVAR, Vals, AbbrevToUse);
 502     Vals.clear();
 503   }
 504
 505   // Emit the function proto information.
 506   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F) {
 507     // FUNCTION:  [type, callingconv, isproto, linkage, paramattrs, alignment,
 508     //             section, visibility, gc, unnamed_addr]
 509     Vals.push_back(VE.getTypeID(F->getType()));
 510     Vals.push_back(F->getCallingConv());
 511     Vals.push_back(F->isDeclaration());
 512     Vals.push_back(getEncodedLinkage(F));
 513     Vals.push_back(VE.getAttributeID(F->getAttributes()));
 514     Vals.push_back(Log2_32(F->getAlignment())+1);
 515     Vals.push_back(F->hasSection() ? SectionMap[F->getSection()] : 0);
 516     Vals.push_back(getEncodedVisibility(F));
 517     Vals.push_back(F->hasGC() ? GCMap[F->getGC()] : 0);
 518     Vals.push_back(F->hasUnnamedAddr());
 519
 520     unsigned AbbrevToUse = 0;
 521     Stream.EmitRecord(bitc::MODULE_CODE_FUNCTION, Vals, AbbrevToUse);
 522     Vals.clear();
 523   }
 524
 525   // Emit the alias information.
 526   for (Module::const_alias_iterator AI = M->alias_begin(), E = M->alias_end();
 527        AI != E; ++AI) {
 528     // ALIAS: [alias type, aliasee val#, linkage, visibility]
 529     Vals.push_back(VE.getTypeID(AI->getType()));
 530     Vals.push_back(VE.getValueID(AI->getAliasee()));
 531     Vals.push_back(getEncodedLinkage(AI));
 532     Vals.push_back(getEncodedVisibility(AI));
 533     unsigned AbbrevToUse = 0;
 534     Stream.EmitRecord(bitc::MODULE_CODE_ALIAS, Vals, AbbrevToUse);
 535     Vals.clear();
 536   }
 537 }
 538
 539 static uint64_t GetOptimizationFlags(const Value *V) {
 540   uint64_t Flags = 0;
 541
 542   if (const OverflowingBinaryOperator *OBO =
 543         dyn_cast<OverflowingBinaryOperator>(V)) {
 544     if (OBO->hasNoSignedWrap())
 545       Flags |= 1 << bitc::OBO_NO_SIGNED_WRAP;
 546     if (OBO->hasNoUnsignedWrap())
 547       Flags |= 1 << bitc::OBO_NO_UNSIGNED_WRAP;
 548   } else if (const PossiblyExactOperator *PEO =
 549                dyn_cast<PossiblyExactOperator>(V)) {
 550     if (PEO->isExact())
 551       Flags |= 1 << bitc::PEO_EXACT;
 552   } else if (const FPMathOperator *FPMO =
 553              dyn_cast<const FPMathOperator>(V)) {
 554     if (FPMO->hasUnsafeAlgebra())
 555       Flags |= 1 << bitc::FMF_UNSAFE_ALGEBRA;
 556     if (FPMO->hasNoNaNs())
 557       Flags |= 1 << bitc::FMF_NO_NANS;
 558     if (FPMO->hasNoInfs())
 559       Flags |= 1 << bitc::FMF_NO_INFS;
 560     if (FPMO->hasNoSignedZeros())
 561       Flags |= 1 << bitc::FMF_NO_SIGNED_ZEROS;
 562     if (FPMO->hasAllowReciprocal())
 563       Flags |= 1 << bitc::FMF_ALLOW_RECIPROCAL;
 564   }
 565
 566   return Flags;
 567 }
 568
 569 static void WriteMDNode(const MDNode *N,
 570                         const ValueEnumerator &VE,
 571                         BitstreamWriter &Stream,
 572                         SmallVector<uint64_t, 64> &Record) {
 573   for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
 574     if (N->getOperand(i)) {
 575       Record.push_back(VE.getTypeID(N->getOperand(i)->getType()));
 576       Record.push_back(VE.getValueID(N->getOperand(i)));
 577     } else {
 578       Record.push_back(VE.getTypeID(Type::getVoidTy(N->getContext())));
 579       Record.push_back(0);
 580     }
 581   }
 582   unsigned MDCode = N->isFunctionLocal() ? bitc::METADATA_FN_NODE :
 583                                            bitc::METADATA_NODE;
 584   Stream.EmitRecord(MDCode, Record, 0);
 585   Record.clear();
 586 }
 587
 588 static void WriteModuleMetadata(const Module *M,
 589                                 const ValueEnumerator &VE,
 590                                 BitstreamWriter &Stream) {
 591   const ValueEnumerator::ValueList &Vals = VE.getMDValues();
 592   bool StartedMetadataBlock = false;
 593   unsigned MDSAbbrev = 0;
 594   SmallVector<uint64_t, 64> Record;
 595   for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
 596
 597     if (const MDNode *N = dyn_cast<MDNode>(Vals[i].first)) {
 598       if (!N->isFunctionLocal() || !N->getFunction()) {
 599         if (!StartedMetadataBlock) {
 600           Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 601           StartedMetadataBlock = true;
 602         }
 603         WriteMDNode(N, VE, Stream, Record);
 604       }
 605     } else if (const MDString *MDS = dyn_cast<MDString>(Vals[i].first)) {
 606       if (!StartedMetadataBlock)  {
 607         Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 608
 609         // Abbrev for METADATA_STRING.
 610         BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 611         Abbv->Add(BitCodeAbbrevOp(bitc::METADATA_STRING));
 612         Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 613         Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
 614         MDSAbbrev = Stream.EmitAbbrev(Abbv);
 615         StartedMetadataBlock = true;
 616       }
 617
 618       // Code: [strchar x N]
 619       Record.append(MDS->begin(), MDS->end());
 620
 621       // Emit the finished record.
 622       Stream.EmitRecord(bitc::METADATA_STRING, Record, MDSAbbrev);
 623       Record.clear();
 624     }
 625   }
 626
 627   // Write named metadata.
 628   for (Module::const_named_metadata_iterator I = M->named_metadata_begin(),
 629        E = M->named_metadata_end(); I != E; ++I) {
 630     const NamedMDNode *NMD = I;
 631     if (!StartedMetadataBlock)  {
 632       Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 633       StartedMetadataBlock = true;
 634     }
 635
 636     // Write name.
 637     StringRef Str = NMD->getName();
 638     for (unsigned i = 0, e = Str.size(); i != e; ++i)
 639       Record.push_back(Str[i]);
 640     Stream.EmitRecord(bitc::METADATA_NAME, Record, 0/*TODO*/);
 641     Record.clear();
 642
 643     // Write named metadata operands.
 644     for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
 645       Record.push_back(VE.getValueID(NMD->getOperand(i)));
 646     Stream.EmitRecord(bitc::METADATA_NAMED_NODE, Record, 0);
 647     Record.clear();
 648   }
 649
 650   if (StartedMetadataBlock)
 651     Stream.ExitBlock();
 652 }
 653
 654 static void WriteFunctionLocalMetadata(const Function &F,
 655                                        const ValueEnumerator &VE,
 656                                        BitstreamWriter &Stream) {
 657   bool StartedMetadataBlock = false;
 658   SmallVector<uint64_t, 64> Record;
 659   const SmallVector<const MDNode *, 8> &Vals = VE.getFunctionLocalMDValues();
 660   for (unsigned i = 0, e = Vals.size(); i != e; ++i)
 661     if (const MDNode *N = Vals[i])
 662       if (N->isFunctionLocal() && N->getFunction() == &F) {
 663         if (!StartedMetadataBlock) {
 664           Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 665           StartedMetadataBlock = true;
 666         }
 667         WriteMDNode(N, VE, Stream, Record);
 668       }
 669
 670   if (StartedMetadataBlock)
 671     Stream.ExitBlock();
 672 }
 673
 674 static void WriteMetadataAttachment(const Function &F,
 675                                     const ValueEnumerator &VE,
 676                                     BitstreamWriter &Stream) {
 677   Stream.EnterSubblock(bitc::METADATA_ATTACHMENT_ID, 3);
 678
 679   SmallVector<uint64_t, 64> Record;
 680
 681   // Write metadata attachments
 682   // METADATA_ATTACHMENT - [m x [value, [n x [id, mdnode]]]
 683   SmallVector<std::pair<unsigned, MDNode*>, 4> MDs;
 684
 685   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
 686     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
 687          I != E; ++I) {
 688       MDs.clear();
 689       I->getAllMetadataOtherThanDebugLoc(MDs);
 690
 691       // If no metadata, ignore instruction.
 692       if (MDs.empty()) continue;
 693
 694       Record.push_back(VE.getInstructionID(I));
 695
 696       for (unsigned i = 0, e = MDs.size(); i != e; ++i) {
 697         Record.push_back(MDs[i].first);
 698         Record.push_back(VE.getValueID(MDs[i].second));
 699       }
 700       Stream.EmitRecord(bitc::METADATA_ATTACHMENT, Record, 0);
 701       Record.clear();
 702     }
 703
 704   Stream.ExitBlock();
 705 }
 706
 707 static void WriteModuleMetadataStore(const Module *M, BitstreamWriter &Stream) {
 708   SmallVector<uint64_t, 64> Record;
 709
 710   // Write metadata kinds
 711   // METADATA_KIND - [n x [id, name]]
 712   SmallVector<StringRef, 4> Names;
 713   M->getMDKindNames(Names);
 714
 715   if (Names.empty()) return;
 716
 717   Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 718
 719   for (unsigned MDKindID = 0, e = Names.size(); MDKindID != e; ++MDKindID) {
 720     Record.push_back(MDKindID);
 721     StringRef KName = Names[MDKindID];
 722     Record.append(KName.begin(), KName.end());
 723
 724     Stream.EmitRecord(bitc::METADATA_KIND, Record, 0);
 725     Record.clear();
 726   }
 727
 728   Stream.ExitBlock();
 729 }
 730
 731 static void emitSignedInt64(SmallVectorImpl<uint64_t> &Vals, uint64_t V) {
 732   if ((int64_t)V >= 0)
 733     Vals.push_back(V << 1);
 734   else
 735     Vals.push_back((-V << 1) | 1);
 736 }
 737
 738 static void EmitAPInt(SmallVectorImpl<uint64_t> &Vals,
 739                       unsigned &Code, unsigned &AbbrevToUse, const APInt &Val,
 740                       bool EmitSizeForWideNumbers = false
 741                       ) {
 742   if (Val.getBitWidth() <= 64) {
 743     uint64_t V = Val.getSExtValue();
 744     emitSignedInt64(Vals, V);
 745     Code = bitc::CST_CODE_INTEGER;
 746     AbbrevToUse = CONSTANTS_INTEGER_ABBREV;
 747   } else {
 748     // Wide integers, > 64 bits in size.
 749     // We have an arbitrary precision integer value to write whose
 750     // bit width is > 64. However, in canonical unsigned integer
 751     // format it is likely that the high bits are going to be zero.
 752     // So, we only write the number of active words.
 753     unsigned NWords = Val.getActiveWords();
 754
 755     if (EmitSizeForWideNumbers)
 756       Vals.push_back(NWords);
 757
 758     const uint64_t *RawWords = Val.getRawData();
 759     for (unsigned i = 0; i != NWords; ++i) {
 760       emitSignedInt64(Vals, RawWords[i]);
 761     }
 762     Code = bitc::CST_CODE_WIDE_INTEGER;
 763   }
 764 }
 765
 766 static void WriteConstants(unsigned FirstVal, unsigned LastVal,
 767                            const ValueEnumerator &VE,
 768                            BitstreamWriter &Stream, bool isGlobal) {
 769   if (FirstVal == LastVal) return;
 770
 771   Stream.EnterSubblock(bitc::CONSTANTS_BLOCK_ID, 4);
 772
 773   unsigned AggregateAbbrev = 0;
 774   unsigned String8Abbrev = 0;
 775   unsigned CString7Abbrev = 0;
 776   unsigned CString6Abbrev = 0;
 777   // If this is a constant pool for the module, emit module-specific abbrevs.
 778   if (isGlobal) {
 779     // Abbrev for CST_CODE_AGGREGATE.
 780     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 781     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_AGGREGATE));
 782     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 783     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, Log2_32_Ceil(LastVal+1)));
 784     AggregateAbbrev = Stream.EmitAbbrev(Abbv);
 785
 786     // Abbrev for CST_CODE_STRING.
 787     Abbv = new BitCodeAbbrev();
 788     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_STRING));
 789     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 790     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
 791     String8Abbrev = Stream.EmitAbbrev(Abbv);
 792     // Abbrev for CST_CODE_CSTRING.
 793     Abbv = new BitCodeAbbrev();
 794     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CSTRING));
 795     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 796     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
 797     CString7Abbrev = Stream.EmitAbbrev(Abbv);
 798     // Abbrev for CST_CODE_CSTRING.
 799     Abbv = new BitCodeAbbrev();
 800     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CSTRING));
 801     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 802     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
 803     CString6Abbrev = Stream.EmitAbbrev(Abbv);
 804   }
 805
 806   SmallVector<uint64_t, 64> Record;
 807
 808   const ValueEnumerator::ValueList &Vals = VE.getValues();
 809   Type *LastTy = 0;
 810   for (unsigned i = FirstVal; i != LastVal; ++i) {
 811     const Value *V = Vals[i].first;
 812     // If we need to switch types, do so now.
 813     if (V->getType() != LastTy) {
 814       LastTy = V->getType();
 815       Record.push_back(VE.getTypeID(LastTy));
 816       Stream.EmitRecord(bitc::CST_CODE_SETTYPE, Record,
 817                         CONSTANTS_SETTYPE_ABBREV);
 818       Record.clear();
 819     }
 820
 821     if (const InlineAsm *IA = dyn_cast<InlineAsm>(V)) {
 822       Record.push_back(unsigned(IA->hasSideEffects()) |
 823                        unsigned(IA->isAlignStack()) << 1 |
 824                        unsigned(IA->getDialect()&1) << 2);
 825
 826       // Add the asm string.
 827       const std::string &AsmStr = IA->getAsmString();
 828       Record.push_back(AsmStr.size());
 829       for (unsigned i = 0, e = AsmStr.size(); i != e; ++i)
 830         Record.push_back(AsmStr[i]);
 831
 832       // Add the constraint string.
 833       const std::string &ConstraintStr = IA->getConstraintString();
 834       Record.push_back(ConstraintStr.size());
 835       for (unsigned i = 0, e = ConstraintStr.size(); i != e; ++i)
 836         Record.push_back(ConstraintStr[i]);
 837       Stream.EmitRecord(bitc::CST_CODE_INLINEASM, Record);
 838       Record.clear();
 839       continue;
 840     }
 841     const Constant *C = cast<Constant>(V);
 842     unsigned Code = -1U;
 843     unsigned AbbrevToUse = 0;
 844     if (C->isNullValue()) {
 845       Code = bitc::CST_CODE_NULL;
 846     } else if (isa<UndefValue>(C)) {
 847       Code = bitc::CST_CODE_UNDEF;
 848     } else if (const ConstantInt *IV = dyn_cast<ConstantInt>(C)) {
 849       EmitAPInt(Record, Code, AbbrevToUse, IV->getValue());
 850     } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
 851       Code = bitc::CST_CODE_FLOAT;
 852       Type *Ty = CFP->getType();
 853       if (Ty->isHalfTy() || Ty->isFloatTy() || Ty->isDoubleTy()) {
 854         Record.push_back(CFP->getValueAPF().bitcastToAPInt().getZExtValue());
 855       } else if (Ty->isX86_FP80Ty()) {
 856         // api needed to prevent premature destruction
 857         // bits are not in the same order as a normal i80 APInt, compensate.
 858         APInt api = CFP->getValueAPF().bitcastToAPInt();
 859         const uint64_t *p = api.getRawData();
 860         Record.push_back((p[1] << 48) | (p[0] >> 16));
 861         Record.push_back(p[0] & 0xffffLL);
 862       } else if (Ty->isFP128Ty() || Ty->isPPC_FP128Ty()) {
 863         APInt api = CFP->getValueAPF().bitcastToAPInt();
 864         const uint64_t *p = api.getRawData();
 865         Record.push_back(p[0]);
 866         Record.push_back(p[1]);
 867       } else {
 868         assert (0 && "Unknown FP type!");
 869       }
 870     } else if (isa<ConstantDataSequential>(C) &&
 871                cast<ConstantDataSequential>(C)->isString()) {
 872       const ConstantDataSequential *Str = cast<ConstantDataSequential>(C);
 873       // Emit constant strings specially.
 874       unsigned NumElts = Str->getNumElements();
 875       // If this is a null-terminated string, use the denser CSTRING encoding.
 876       if (Str->isCString()) {
 877         Code = bitc::CST_CODE_CSTRING;
 878         --NumElts;  // Don't encode the null, which isn't allowed by char6.
 879       } else {
 880         Code = bitc::CST_CODE_STRING;
 881         AbbrevToUse = String8Abbrev;
 882       }
 883       bool isCStr7 = Code == bitc::CST_CODE_CSTRING;
 884       bool isCStrChar6 = Code == bitc::CST_CODE_CSTRING;
 885       for (unsigned i = 0; i != NumElts; ++i) {
 886         unsigned char V = Str->getElementAsInteger(i);
 887         Record.push_back(V);
 888         isCStr7 &= (V & 128) == 0;
 889         if (isCStrChar6)
 890           isCStrChar6 = BitCodeAbbrevOp::isChar6(V);
 891       }
 892
 893       if (isCStrChar6)
 894         AbbrevToUse = CString6Abbrev;
 895       else if (isCStr7)
 896         AbbrevToUse = CString7Abbrev;
 897     } else if (const ConstantDataSequential *CDS =
 898                   dyn_cast<ConstantDataSequential>(C)) {
 899       Code = bitc::CST_CODE_DATA;
 900       Type *EltTy = CDS->getType()->getElementType();
 901       if (isa<IntegerType>(EltTy)) {
 902         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i)
 903           Record.push_back(CDS->getElementAsInteger(i));
 904       } else if (EltTy->isFloatTy()) {
 905         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
 906           union { float F; uint32_t I; };
 907           F = CDS->getElementAsFloat(i);
 908           Record.push_back(I);
 909         }
 910       } else {
 911         assert(EltTy->isDoubleTy() && "Unknown ConstantData element type");
 912         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
 913           union { double F; uint64_t I; };
 914           F = CDS->getElementAsDouble(i);
 915           Record.push_back(I);
 916         }
 917       }
 918     } else if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
 919                isa<ConstantVector>(C)) {
 920       Code = bitc::CST_CODE_AGGREGATE;
 921       for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
 922         Record.push_back(VE.getValueID(C->getOperand(i)));
 923       AbbrevToUse = AggregateAbbrev;
 924     } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
 925       switch (CE->getOpcode()) {
 926       default:
 927         if (Instruction::isCast(CE->getOpcode())) {
 928           Code = bitc::CST_CODE_CE_CAST;
 929           Record.push_back(GetEncodedCastOpcode(CE->getOpcode()));
 930           Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
 931           Record.push_back(VE.getValueID(C->getOperand(0)));
 932           AbbrevToUse = CONSTANTS_CE_CAST_Abbrev;
 933         } else {
 934           assert(CE->getNumOperands() == 2 && "Unknown constant expr!");
 935           Code = bitc::CST_CODE_CE_BINOP;
 936           Record.push_back(GetEncodedBinaryOpcode(CE->getOpcode()));
 937           Record.push_back(VE.getValueID(C->getOperand(0)));
 938           Record.push_back(VE.getValueID(C->getOperand(1)));
 939           uint64_t Flags = GetOptimizationFlags(CE);
 940           if (Flags != 0)
 941             Record.push_back(Flags);
 942         }
 943         break;
 944       case Instruction::GetElementPtr:
 945         Code = bitc::CST_CODE_CE_GEP;
 946         if (cast<GEPOperator>(C)->isInBounds())
 947           Code = bitc::CST_CODE_CE_INBOUNDS_GEP;
 948         for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) {
 949           Record.push_back(VE.getTypeID(C->getOperand(i)->getType()));
 950           Record.push_back(VE.getValueID(C->getOperand(i)));
 951         }
 952         break;
 953       case Instruction::Select:
 954         Code = bitc::CST_CODE_CE_SELECT;
 955         Record.push_back(VE.getValueID(C->getOperand(0)));
 956         Record.push_back(VE.getValueID(C->getOperand(1)));
 957         Record.push_back(VE.getValueID(C->getOperand(2)));
 958         break;
 959       case Instruction::ExtractElement:
 960         Code = bitc::CST_CODE_CE_EXTRACTELT;
 961         Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
 962         Record.push_back(VE.getValueID(C->getOperand(0)));
 963         Record.push_back(VE.getValueID(C->getOperand(1)));
 964         break;
 965       case Instruction::InsertElement:
 966         Code = bitc::CST_CODE_CE_INSERTELT;
 967         Record.push_back(VE.getValueID(C->getOperand(0)));
 968         Record.push_back(VE.getValueID(C->getOperand(1)));
 969         Record.push_back(VE.getValueID(C->getOperand(2)));
 970         break;
 971       case Instruction::ShuffleVector:
 972         // If the return type and argument types are the same, this is a
 973         // standard shufflevector instruction.  If the types are different,
 974         // then the shuffle is widening or truncating the input vectors, and
 975         // the argument type must also be encoded.
 976         if (C->getType() == C->getOperand(0)->getType()) {
 977           Code = bitc::CST_CODE_CE_SHUFFLEVEC;
 978         } else {
 979           Code = bitc::CST_CODE_CE_SHUFVEC_EX;
 980           Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
 981         }
 982         Record.push_back(VE.getValueID(C->getOperand(0)));
 983         Record.push_back(VE.getValueID(C->getOperand(1)));
 984         Record.push_back(VE.getValueID(C->getOperand(2)));
 985         break;
 986       case Instruction::ICmp:
 987       case Instruction::FCmp:
 988         Code = bitc::CST_CODE_CE_CMP;
 989         Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
 990         Record.push_back(VE.getValueID(C->getOperand(0)));
 991         Record.push_back(VE.getValueID(C->getOperand(1)));
 992         Record.push_back(CE->getPredicate());
 993         break;
 994       }
 995     } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
 996       Code = bitc::CST_CODE_BLOCKADDRESS;
 997       Record.push_back(VE.getTypeID(BA->getFunction()->getType()));
 998       Record.push_back(VE.getValueID(BA->getFunction()));
 999       Record.push_back(VE.getGlobalBasicBlockID(BA->getBasicBlock()));
1000     } else {
1001 #ifndef NDEBUG
1002       C->dump();
1003 #endif
1004       llvm_unreachable("Unknown constant!");
1005     }
1006     Stream.EmitRecord(Code, Record, AbbrevToUse);
1007     Record.clear();
1008   }
1009
1010   Stream.ExitBlock();
1011 }
1012
1013 static void WriteModuleConstants(const ValueEnumerator &VE,
1014                                  BitstreamWriter &Stream) {
1015   const ValueEnumerator::ValueList &Vals = VE.getValues();
1016
1017   // Find the first constant to emit, which is the first non-globalvalue value.
1018   // We know globalvalues have been emitted by WriteModuleInfo.
1019   for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
1020     if (!isa<GlobalValue>(Vals[i].first)) {
1021       WriteConstants(i, Vals.size(), VE, Stream, true);
1022       return;
1023     }
1024   }
1025 }
1026
1027 /// PushValueAndType - The file has to encode both the value and type id for
1028 /// many values, because we need to know what type to create for forward
1029 /// references.  However, most operands are not forward references, so this type
1030 /// field is not needed.
1031 ///
1032 /// This function adds V's value ID to Vals.  If the value ID is higher than the
1033 /// instruction ID, then it is a forward reference, and it also includes the
1034 /// type ID.  The value ID that is written is encoded relative to the InstID.
1035 static bool PushValueAndType(const Value *V, unsigned InstID,
1036                              SmallVector<unsigned, 64> &Vals,
1037                              ValueEnumerator &VE) {
1038   unsigned ValID = VE.getValueID(V);
1039   // Make encoding relative to the InstID.
1040   Vals.push_back(InstID - ValID);
1041   if (ValID >= InstID) {
1042     Vals.push_back(VE.getTypeID(V->getType()));
1043     return true;
1044   }
1045   return false;
1046 }
1047
1048 /// pushValue - Like PushValueAndType, but where the type of the value is
1049 /// omitted (perhaps it was already encoded in an earlier operand).
1050 static void pushValue(const Value *V, unsigned InstID,
1051                       SmallVector<unsigned, 64> &Vals,
1052                       ValueEnumerator &VE) {
1053   unsigned ValID = VE.getValueID(V);
1054   Vals.push_back(InstID - ValID);
1055 }
1056
1057 static void pushValue64(const Value *V, unsigned InstID,
1058                         SmallVector<uint64_t, 128> &Vals,
1059                         ValueEnumerator &VE) {
1060   uint64_t ValID = VE.getValueID(V);
1061   Vals.push_back(InstID - ValID);
1062 }
1063
1064 static void pushValueSigned(const Value *V, unsigned InstID,
1065                             SmallVector<uint64_t, 128> &Vals,
1066                             ValueEnumerator &VE) {
1067   unsigned ValID = VE.getValueID(V);
1068   int64_t diff = ((int32_t)InstID - (int32_t)ValID);
1069   emitSignedInt64(Vals, diff);
1070 }
1071
1072 /// WriteInstruction - Emit an instruction to the specified stream.
1073 static void WriteInstruction(const Instruction &I, unsigned InstID,
1074                              ValueEnumerator &VE, BitstreamWriter &Stream,
1075                              SmallVector<unsigned, 64> &Vals) {
1076   unsigned Code = 0;
1077   unsigned AbbrevToUse = 0;
1078   VE.setInstructionID(&I);
1079   switch (I.getOpcode()) {
1080   default:
1081     if (Instruction::isCast(I.getOpcode())) {
1082       Code = bitc::FUNC_CODE_INST_CAST;
1083       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1084         AbbrevToUse = FUNCTION_INST_CAST_ABBREV;
1085       Vals.push_back(VE.getTypeID(I.getType()));
1086       Vals.push_back(GetEncodedCastOpcode(I.getOpcode()));
1087     } else {
1088       assert(isa<BinaryOperator>(I) && "Unknown instruction!");
1089       Code = bitc::FUNC_CODE_INST_BINOP;
1090       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1091         AbbrevToUse = FUNCTION_INST_BINOP_ABBREV;
1092       pushValue(I.getOperand(1), InstID, Vals, VE);
1093       Vals.push_back(GetEncodedBinaryOpcode(I.getOpcode()));
1094       uint64_t Flags = GetOptimizationFlags(&I);
1095       if (Flags != 0) {
1096         if (AbbrevToUse == FUNCTION_INST_BINOP_ABBREV)
1097           AbbrevToUse = FUNCTION_INST_BINOP_FLAGS_ABBREV;
1098         Vals.push_back(Flags);
1099       }
1100     }
1101     break;
1102
1103   case Instruction::GetElementPtr:
1104     Code = bitc::FUNC_CODE_INST_GEP;
1105     if (cast<GEPOperator>(&I)->isInBounds())
1106       Code = bitc::FUNC_CODE_INST_INBOUNDS_GEP;
1107     for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
1108       PushValueAndType(I.getOperand(i), InstID, Vals, VE);
1109     break;
1110   case Instruction::ExtractValue: {
1111     Code = bitc::FUNC_CODE_INST_EXTRACTVAL;
1112     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1113     const ExtractValueInst *EVI = cast<ExtractValueInst>(&I);
1114     for (const unsigned *i = EVI->idx_begin(), *e = EVI->idx_end(); i != e; ++i)
1115       Vals.push_back(*i);
1116     break;
1117   }
1118   case Instruction::InsertValue: {
1119     Code = bitc::FUNC_CODE_INST_INSERTVAL;
1120     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1121     PushValueAndType(I.getOperand(1), InstID, Vals, VE);
1122     const InsertValueInst *IVI = cast<InsertValueInst>(&I);
1123     for (const unsigned *i = IVI->idx_begin(), *e = IVI->idx_end(); i != e; ++i)
1124       Vals.push_back(*i);
1125     break;
1126   }
1127   case Instruction::Select:
1128     Code = bitc::FUNC_CODE_INST_VSELECT;
1129     PushValueAndType(I.getOperand(1), InstID, Vals, VE);
1130     pushValue(I.getOperand(2), InstID, Vals, VE);
1131     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1132     break;
1133   case Instruction::ExtractElement:
1134     Code = bitc::FUNC_CODE_INST_EXTRACTELT;
1135     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1136     pushValue(I.getOperand(1), InstID, Vals, VE);
1137     break;
1138   case Instruction::InsertElement:
1139     Code = bitc::FUNC_CODE_INST_INSERTELT;
1140     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1141     pushValue(I.getOperand(1), InstID, Vals, VE);
1142     pushValue(I.getOperand(2), InstID, Vals, VE);
1143     break;
1144   case Instruction::ShuffleVector:
1145     Code = bitc::FUNC_CODE_INST_SHUFFLEVEC;
1146     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1147     pushValue(I.getOperand(1), InstID, Vals, VE);
1148     pushValue(I.getOperand(2), InstID, Vals, VE);
1149     break;
1150   case Instruction::ICmp:
1151   case Instruction::FCmp:
1152     // compare returning Int1Ty or vector of Int1Ty
1153     Code = bitc::FUNC_CODE_INST_CMP2;
1154     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1155     pushValue(I.getOperand(1), InstID, Vals, VE);
1156     Vals.push_back(cast<CmpInst>(I).getPredicate());
1157     break;
1158
1159   case Instruction::Ret:
1160     {
1161       Code = bitc::FUNC_CODE_INST_RET;
1162       unsigned NumOperands = I.getNumOperands();
1163       if (NumOperands == 0)
1164         AbbrevToUse = FUNCTION_INST_RET_VOID_ABBREV;
1165       else if (NumOperands == 1) {
1166         if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1167           AbbrevToUse = FUNCTION_INST_RET_VAL_ABBREV;
1168       } else {
1169         for (unsigned i = 0, e = NumOperands; i != e; ++i)
1170           PushValueAndType(I.getOperand(i), InstID, Vals, VE);
1171       }
1172     }
1173     break;
1174   case Instruction::Br:
1175     {
1176       Code = bitc::FUNC_CODE_INST_BR;
1177       BranchInst &II = cast<BranchInst>(I);
1178       Vals.push_back(VE.getValueID(II.getSuccessor(0)));
1179       if (II.isConditional()) {
1180         Vals.push_back(VE.getValueID(II.getSuccessor(1)));
1181         pushValue(II.getCondition(), InstID, Vals, VE);
1182       }
1183     }
1184     break;
1185   case Instruction::Switch:
1186     {
1187       // Redefine Vals, since here we need to use 64 bit values
1188       // explicitly to store large APInt numbers.
1189       SmallVector<uint64_t, 128> Vals64;
1190
1191       Code = bitc::FUNC_CODE_INST_SWITCH;
1192       SwitchInst &SI = cast<SwitchInst>(I);
1193
1194       uint32_t SwitchRecordHeader = SI.hash() | (SWITCH_INST_MAGIC << 16);
1195       Vals64.push_back(SwitchRecordHeader);
1196
1197       Vals64.push_back(VE.getTypeID(SI.getCondition()->getType()));
1198       pushValue64(SI.getCondition(), InstID, Vals64, VE);
1199       Vals64.push_back(VE.getValueID(SI.getDefaultDest()));
1200       Vals64.push_back(SI.getNumCases());
1201       for (SwitchInst::CaseIt i = SI.case_begin(), e = SI.case_end();
1202            i != e; ++i) {
1203         IntegersSubset& CaseRanges = i.getCaseValueEx();
1204         unsigned Code, Abbrev; // will unused.
1205
1206         if (CaseRanges.isSingleNumber()) {
1207           Vals64.push_back(1/*NumItems = 1*/);
1208           Vals64.push_back(true/*IsSingleNumber = true*/);
1209           EmitAPInt(Vals64, Code, Abbrev, CaseRanges.getSingleNumber(0), true);
1210         } else {
1211
1212           Vals64.push_back(CaseRanges.getNumItems());
1213
1214           if (CaseRanges.isSingleNumbersOnly()) {
1215             for (unsigned ri = 0, rn = CaseRanges.getNumItems();
1216                  ri != rn; ++ri) {
1217
1218               Vals64.push_back(true/*IsSingleNumber = true*/);
1219
1220               EmitAPInt(Vals64, Code, Abbrev,
1221                         CaseRanges.getSingleNumber(ri), true);
1222             }
1223           } else
1224             for (unsigned ri = 0, rn = CaseRanges.getNumItems();
1225                  ri != rn; ++ri) {
1226               IntegersSubset::Range r = CaseRanges.getItem(ri);
1227               bool IsSingleNumber = CaseRanges.isSingleNumber(ri);
1228
1229               Vals64.push_back(IsSingleNumber);
1230
1231               EmitAPInt(Vals64, Code, Abbrev, r.getLow(), true);
1232               if (!IsSingleNumber)
1233                 EmitAPInt(Vals64, Code, Abbrev, r.getHigh(), true);
1234             }
1235         }
1236         Vals64.push_back(VE.getValueID(i.getCaseSuccessor()));
1237       }
1238
1239       Stream.EmitRecord(Code, Vals64, AbbrevToUse);
1240
1241       // Also do expected action - clear external Vals collection:
1242       Vals.clear();
1243       return;
1244     }
1245     break;
1246   case Instruction::IndirectBr:
1247     Code = bitc::FUNC_CODE_INST_INDIRECTBR;
1248     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));
1249     // Encode the address operand as relative, but not the basic blocks.
1250     pushValue(I.getOperand(0), InstID, Vals, VE);
1251     for (unsigned i = 1, e = I.getNumOperands(); i != e; ++i)
1252       Vals.push_back(VE.getValueID(I.getOperand(i)));
1253     break;
1254
1255   case Instruction::Invoke: {
1256     const InvokeInst *II = cast<InvokeInst>(&I);
1257     const Value *Callee(II->getCalledValue());
1258     PointerType *PTy = cast<PointerType>(Callee->getType());
1259     FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1260     Code = bitc::FUNC_CODE_INST_INVOKE;
1261
1262     Vals.push_back(VE.getAttributeID(II->getAttributes()));
1263     Vals.push_back(II->getCallingConv());
1264     Vals.push_back(VE.getValueID(II->getNormalDest()));
1265     Vals.push_back(VE.getValueID(II->getUnwindDest()));
1266     PushValueAndType(Callee, InstID, Vals, VE);
1267
1268     // Emit value #'s for the fixed parameters.
1269     for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
1270       pushValue(I.getOperand(i), InstID, Vals, VE);  // fixed param.
1271
1272     // Emit type/value pairs for varargs params.
1273     if (FTy->isVarArg()) {
1274       for (unsigned i = FTy->getNumParams(), e = I.getNumOperands()-3;
1275            i != e; ++i)
1276         PushValueAndType(I.getOperand(i), InstID, Vals, VE); // vararg
1277     }
1278     break;
1279   }
1280   case Instruction::Resume:
1281     Code = bitc::FUNC_CODE_INST_RESUME;
1282     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1283     break;
1284   case Instruction::Unreachable:
1285     Code = bitc::FUNC_CODE_INST_UNREACHABLE;
1286     AbbrevToUse = FUNCTION_INST_UNREACHABLE_ABBREV;
1287     break;
1288
1289   case Instruction::PHI: {
1290     const PHINode &PN = cast<PHINode>(I);
1291     Code = bitc::FUNC_CODE_INST_PHI;
1292     // With the newer instruction encoding, forward references could give
1293     // negative valued IDs.  This is most common for PHIs, so we use
1294     // signed VBRs.
1295     SmallVector<uint64_t, 128> Vals64;
1296     Vals64.push_back(VE.getTypeID(PN.getType()));
1297     for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
1298       pushValueSigned(PN.getIncomingValue(i), InstID, Vals64, VE);
1299       Vals64.push_back(VE.getValueID(PN.getIncomingBlock(i)));
1300     }
1301     // Emit a Vals64 vector and exit.
1302     Stream.EmitRecord(Code, Vals64, AbbrevToUse);
1303     Vals64.clear();
1304     return;
1305   }
1306
1307   case Instruction::LandingPad: {
1308     const LandingPadInst &LP = cast<LandingPadInst>(I);
1309     Code = bitc::FUNC_CODE_INST_LANDINGPAD;
1310     Vals.push_back(VE.getTypeID(LP.getType()));
1311     PushValueAndType(LP.getPersonalityFn(), InstID, Vals, VE);
1312     Vals.push_back(LP.isCleanup());
1313     Vals.push_back(LP.getNumClauses());
1314     for (unsigned I = 0, E = LP.getNumClauses(); I != E; ++I) {
1315       if (LP.isCatch(I))
1316         Vals.push_back(LandingPadInst::Catch);
1317       else
1318         Vals.push_back(LandingPadInst::Filter);
1319       PushValueAndType(LP.getClause(I), InstID, Vals, VE);
1320     }
1321     break;
1322   }
1323
1324   case Instruction::Alloca:
1325     Code = bitc::FUNC_CODE_INST_ALLOCA;
1326     Vals.push_back(VE.getTypeID(I.getType()));
1327     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));
1328     Vals.push_back(VE.getValueID(I.getOperand(0))); // size.
1329     Vals.push_back(Log2_32(cast<AllocaInst>(I).getAlignment())+1);
1330     break;
1331
1332   case Instruction::Load:
1333     if (cast<LoadInst>(I).isAtomic()) {
1334       Code = bitc::FUNC_CODE_INST_LOADATOMIC;
1335       PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1336     } else {
1337       Code = bitc::FUNC_CODE_INST_LOAD;
1338       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))  // ptr
1339         AbbrevToUse = FUNCTION_INST_LOAD_ABBREV;
1340     }
1341     Vals.push_back(Log2_32(cast<LoadInst>(I).getAlignment())+1);
1342     Vals.push_back(cast<LoadInst>(I).isVolatile());
1343     if (cast<LoadInst>(I).isAtomic()) {
1344       Vals.push_back(GetEncodedOrdering(cast<LoadInst>(I).getOrdering()));
1345       Vals.push_back(GetEncodedSynchScope(cast<LoadInst>(I).getSynchScope()));
1346     }
1347     break;
1348   case Instruction::Store:
1349     if (cast<StoreInst>(I).isAtomic())
1350       Code = bitc::FUNC_CODE_INST_STOREATOMIC;
1351     else
1352       Code = bitc::FUNC_CODE_INST_STORE;
1353     PushValueAndType(I.getOperand(1), InstID, Vals, VE);  // ptrty + ptr
1354     pushValue(I.getOperand(0), InstID, Vals, VE);         // val.
1355     Vals.push_back(Log2_32(cast<StoreInst>(I).getAlignment())+1);
1356     Vals.push_back(cast<StoreInst>(I).isVolatile());
1357     if (cast<StoreInst>(I).isAtomic()) {
1358       Vals.push_back(GetEncodedOrdering(cast<StoreInst>(I).getOrdering()));
1359       Vals.push_back(GetEncodedSynchScope(cast<StoreInst>(I).getSynchScope()));
1360     }
1361     break;
1362   case Instruction::AtomicCmpXchg:
1363     Code = bitc::FUNC_CODE_INST_CMPXCHG;
1364     PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // ptrty + ptr
1365     pushValue(I.getOperand(1), InstID, Vals, VE);         // cmp.
1366     pushValue(I.getOperand(2), InstID, Vals, VE);         // newval.
1367     Vals.push_back(cast<AtomicCmpXchgInst>(I).isVolatile());
1368     Vals.push_back(GetEncodedOrdering(
1369                      cast<AtomicCmpXchgInst>(I).getOrdering()));
1370     Vals.push_back(GetEncodedSynchScope(
1371                      cast<AtomicCmpXchgInst>(I).getSynchScope()));
1372     break;
1373   case Instruction::AtomicRMW:
1374     Code = bitc::FUNC_CODE_INST_ATOMICRMW;
1375     PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // ptrty + ptr
1376     pushValue(I.getOperand(1), InstID, Vals, VE);         // val.
1377     Vals.push_back(GetEncodedRMWOperation(
1378                      cast<AtomicRMWInst>(I).getOperation()));
1379     Vals.push_back(cast<AtomicRMWInst>(I).isVolatile());
1380     Vals.push_back(GetEncodedOrdering(cast<AtomicRMWInst>(I).getOrdering()));
1381     Vals.push_back(GetEncodedSynchScope(
1382                      cast<AtomicRMWInst>(I).getSynchScope()));
1383     break;
1384   case Instruction::Fence:
1385     Code = bitc::FUNC_CODE_INST_FENCE;
1386     Vals.push_back(GetEncodedOrdering(cast<FenceInst>(I).getOrdering()));
1387     Vals.push_back(GetEncodedSynchScope(cast<FenceInst>(I).getSynchScope()));
1388     break;
1389   case Instruction::Call: {
1390     const CallInst &CI = cast<CallInst>(I);
1391     PointerType *PTy = cast<PointerType>(CI.getCalledValue()->getType());
1392     FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1393
1394     Code = bitc::FUNC_CODE_INST_CALL;
1395
1396     Vals.push_back(VE.getAttributeID(CI.getAttributes()));
1397     Vals.push_back((CI.getCallingConv() << 1) | unsigned(CI.isTailCall()));
1398     PushValueAndType(CI.getCalledValue(), InstID, Vals, VE);  // Callee
1399
1400     // Emit value #'s for the fixed parameters.
1401     for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i) {
1402       // Check for labels (can happen with asm labels).
1403       if (FTy->getParamType(i)->isLabelTy())
1404         Vals.push_back(VE.getValueID(CI.getArgOperand(i)));
1405       else
1406         pushValue(CI.getArgOperand(i), InstID, Vals, VE);  // fixed param.
1407     }
1408
1409     // Emit type/value pairs for varargs params.
1410     if (FTy->isVarArg()) {
1411       for (unsigned i = FTy->getNumParams(), e = CI.getNumArgOperands();
1412            i != e; ++i)
1413         PushValueAndType(CI.getArgOperand(i), InstID, Vals, VE);  // varargs
1414     }
1415     break;
1416   }
1417   case Instruction::VAArg:
1418     Code = bitc::FUNC_CODE_INST_VAARG;
1419     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));   // valistty
1420     pushValue(I.getOperand(0), InstID, Vals, VE); // valist.
1421     Vals.push_back(VE.getTypeID(I.getType())); // restype.
1422     break;
1423   }
1424
1425   Stream.EmitRecord(Code, Vals, AbbrevToUse);
1426   Vals.clear();
1427 }
1428
1429 // Emit names for globals/functions etc.
1430 static void WriteValueSymbolTable(const ValueSymbolTable &VST,
1431                                   const ValueEnumerator &VE,
1432                                   BitstreamWriter &Stream) {
1433   if (VST.empty()) return;
1434   Stream.EnterSubblock(bitc::VALUE_SYMTAB_BLOCK_ID, 4);
1435
1436   // FIXME: Set up the abbrev, we know how many values there are!
1437   // FIXME: We know if the type names can use 7-bit ascii.
1438   SmallVector<unsigned, 64> NameVals;
1439
1440   for (ValueSymbolTable::const_iterator SI = VST.begin(), SE = VST.end();
1441        SI != SE; ++SI) {
1442
1443     const ValueName &Name = *SI;
1444
1445     // Figure out the encoding to use for the name.
1446     bool is7Bit = true;
1447     bool isChar6 = true;
1448     for (const char *C = Name.getKeyData(), *E = C+Name.getKeyLength();
1449          C != E; ++C) {
1450       if (isChar6)
1451         isChar6 = BitCodeAbbrevOp::isChar6(*C);
1452       if ((unsigned char)*C & 128) {
1453         is7Bit = false;
1454         break;  // don't bother scanning the rest.
1455       }
1456     }
1457
1458     unsigned AbbrevToUse = VST_ENTRY_8_ABBREV;
1459
1460     // VST_ENTRY:   [valueid, namechar x N]
1461     // VST_BBENTRY: [bbid, namechar x N]
1462     unsigned Code;
1463     if (isa<BasicBlock>(SI->getValue())) {
1464       Code = bitc::VST_CODE_BBENTRY;
1465       if (isChar6)
1466         AbbrevToUse = VST_BBENTRY_6_ABBREV;
1467     } else {
1468       Code = bitc::VST_CODE_ENTRY;
1469       if (isChar6)
1470         AbbrevToUse = VST_ENTRY_6_ABBREV;
1471       else if (is7Bit)
1472         AbbrevToUse = VST_ENTRY_7_ABBREV;
1473     }
1474
1475     NameVals.push_back(VE.getValueID(SI->getValue()));
1476     for (const char *P = Name.getKeyData(),
1477          *E = Name.getKeyData()+Name.getKeyLength(); P != E; ++P)
1478       NameVals.push_back((unsigned char)*P);
1479
1480     // Emit the finished record.
1481     Stream.EmitRecord(Code, NameVals, AbbrevToUse);
1482     NameVals.clear();
1483   }
1484   Stream.ExitBlock();
1485 }
1486
1487 /// WriteFunction - Emit a function body to the module stream.
1488 static void WriteFunction(const Function &F, ValueEnumerator &VE,
1489                           BitstreamWriter &Stream) {
1490   Stream.EnterSubblock(bitc::FUNCTION_BLOCK_ID, 4);
1491   VE.incorporateFunction(F);
1492
1493   SmallVector<unsigned, 64> Vals;
1494
1495   // Emit the number of basic blocks, so the reader can create them ahead of
1496   // time.
1497   Vals.push_back(VE.getBasicBlocks().size());
1498   Stream.EmitRecord(bitc::FUNC_CODE_DECLAREBLOCKS, Vals);
1499   Vals.clear();
1500
1501   // If there are function-local constants, emit them now.
1502   unsigned CstStart, CstEnd;
1503   VE.getFunctionConstantRange(CstStart, CstEnd);
1504   WriteConstants(CstStart, CstEnd, VE, Stream, false);
1505
1506   // If there is function-local metadata, emit it now.
1507   WriteFunctionLocalMetadata(F, VE, Stream);
1508
1509   // Keep a running idea of what the instruction ID is.
1510   unsigned InstID = CstEnd;
1511
1512   bool NeedsMetadataAttachment = false;
1513
1514   DebugLoc LastDL;
1515
1516   // Finally, emit all the instructions, in order.
1517   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
1518     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
1519          I != E; ++I) {
1520       WriteInstruction(*I, InstID, VE, Stream, Vals);
1521
1522       if (!I->getType()->isVoidTy())
1523         ++InstID;
1524
1525       // If the instruction has metadata, write a metadata attachment later.
1526       NeedsMetadataAttachment |= I->hasMetadataOtherThanDebugLoc();
1527
1528       // If the instruction has a debug location, emit it.
1529       DebugLoc DL = I->getDebugLoc();
1530       if (DL.isUnknown()) {
1531         // nothing todo.
1532       } else if (DL == LastDL) {
1533         // Just repeat the same debug loc as last time.
1534         Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC_AGAIN, Vals);
1535       } else {
1536         MDNode *Scope, *IA;
1537         DL.getScopeAndInlinedAt(Scope, IA, I->getContext());
1538
1539         Vals.push_back(DL.getLine());
1540         Vals.push_back(DL.getCol());
1541         Vals.push_back(Scope ? VE.getValueID(Scope)+1 : 0);
1542         Vals.push_back(IA ? VE.getValueID(IA)+1 : 0);
1543         Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC, Vals);
1544         Vals.clear();
1545
1546         LastDL = DL;
1547       }
1548     }
1549
1550   // Emit names for all the instructions etc.
1551   WriteValueSymbolTable(F.getValueSymbolTable(), VE, Stream);
1552
1553   if (NeedsMetadataAttachment)
1554     WriteMetadataAttachment(F, VE, Stream);
1555   VE.purgeFunction();
1556   Stream.ExitBlock();
1557 }
1558
1559 // Emit blockinfo, which defines the standard abbreviations etc.
1560 static void WriteBlockInfo(const ValueEnumerator &VE, BitstreamWriter &Stream) {
1561   // We only want to emit block info records for blocks that have multiple
1562   // instances: CONSTANTS_BLOCK, FUNCTION_BLOCK and VALUE_SYMTAB_BLOCK.
1563   // Other blocks can define their abbrevs inline.
1564   Stream.EnterBlockInfoBlock(2);
1565
1566   { // 8-bit fixed-width VST_ENTRY/VST_BBENTRY strings.
1567     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1568     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3));
1569     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1570     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1571     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
1572     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1573                                    Abbv) != VST_ENTRY_8_ABBREV)
1574       llvm_unreachable("Unexpected abbrev ordering!");
1575   }
1576
1577   { // 7-bit fixed width VST_ENTRY strings.
1578     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1579     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
1580     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1581     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1582     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
1583     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1584                                    Abbv) != VST_ENTRY_7_ABBREV)
1585       llvm_unreachable("Unexpected abbrev ordering!");
1586   }
1587   { // 6-bit char6 VST_ENTRY strings.
1588     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1589     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
1590     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1591     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1592     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
1593     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1594                                    Abbv) != VST_ENTRY_6_ABBREV)
1595       llvm_unreachable("Unexpected abbrev ordering!");
1596   }
1597   { // 6-bit char6 VST_BBENTRY strings.
1598     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1599     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_BBENTRY));
1600     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1601     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1602     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
1603     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1604                                    Abbv) != VST_BBENTRY_6_ABBREV)
1605       llvm_unreachable("Unexpected abbrev ordering!");
1606   }
1607
1608
1609
1610   { // SETTYPE abbrev for CONSTANTS_BLOCK.
1611     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1612     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_SETTYPE));
1613     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
1614                               Log2_32_Ceil(VE.getTypes().size()+1)));
1615     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1616                                    Abbv) != CONSTANTS_SETTYPE_ABBREV)
1617       llvm_unreachable("Unexpected abbrev ordering!");
1618   }
1619
1620   { // INTEGER abbrev for CONSTANTS_BLOCK.
1621     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1622     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_INTEGER));
1623     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1624     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1625                                    Abbv) != CONSTANTS_INTEGER_ABBREV)
1626       llvm_unreachable("Unexpected abbrev ordering!");
1627   }
1628
1629   { // CE_CAST abbrev for CONSTANTS_BLOCK.
1630     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1631     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CE_CAST));
1632     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));  // cast opc
1633     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,       // typeid
1634                               Log2_32_Ceil(VE.getTypes().size()+1)));
1635     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));    // value id
1636
1637     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1638                                    Abbv) != CONSTANTS_CE_CAST_Abbrev)
1639       llvm_unreachable("Unexpected abbrev ordering!");
1640   }
1641   { // NULL abbrev for CONSTANTS_BLOCK.
1642     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1643     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_NULL));
1644     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1645                                    Abbv) != CONSTANTS_NULL_Abbrev)
1646       llvm_unreachable("Unexpected abbrev ordering!");
1647   }
1648
1649   // FIXME: This should only use space for first class types!
1650
1651   { // INST_LOAD abbrev for FUNCTION_BLOCK.
1652     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1653     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_LOAD));
1654     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Ptr
1655     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // Align
1656     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // volatile
1657     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1658                                    Abbv) != FUNCTION_INST_LOAD_ABBREV)
1659       llvm_unreachable("Unexpected abbrev ordering!");
1660   }
1661   { // INST_BINOP abbrev for FUNCTION_BLOCK.
1662     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1663     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_BINOP));
1664     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
1665     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // RHS
1666     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
1667     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1668                                    Abbv) != FUNCTION_INST_BINOP_ABBREV)
1669       llvm_unreachable("Unexpected abbrev ordering!");
1670   }
1671   { // INST_BINOP_FLAGS abbrev for FUNCTION_BLOCK.
1672     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1673     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_BINOP));
1674     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
1675     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // RHS
1676     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
1677     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7)); // flags
1678     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1679                                    Abbv) != FUNCTION_INST_BINOP_FLAGS_ABBREV)
1680       llvm_unreachable("Unexpected abbrev ordering!");
1681   }
1682   { // INST_CAST abbrev for FUNCTION_BLOCK.
1683     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1684     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_CAST));
1685     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));    // OpVal
1686     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,       // dest ty
1687                               Log2_32_Ceil(VE.getTypes().size()+1)));
1688     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));  // opc
1689     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1690                                    Abbv) != FUNCTION_INST_CAST_ABBREV)
1691       llvm_unreachable("Unexpected abbrev ordering!");
1692   }
1693
1694   { // INST_RET abbrev for FUNCTION_BLOCK.
1695     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1696     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_RET));
1697     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1698                                    Abbv) != FUNCTION_INST_RET_VOID_ABBREV)
1699       llvm_unreachable("Unexpected abbrev ordering!");
1700   }
1701   { // INST_RET abbrev for FUNCTION_BLOCK.
1702     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1703     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_RET));
1704     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // ValID
1705     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1706                                    Abbv) != FUNCTION_INST_RET_VAL_ABBREV)
1707       llvm_unreachable("Unexpected abbrev ordering!");
1708   }
1709   { // INST_UNREACHABLE abbrev for FUNCTION_BLOCK.
1710     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1711     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_UNREACHABLE));
1712     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1713                                    Abbv) != FUNCTION_INST_UNREACHABLE_ABBREV)
1714       llvm_unreachable("Unexpected abbrev ordering!");
1715   }
1716
1717   Stream.ExitBlock();
1718 }
1719
1720 // Sort the Users based on the order in which the reader parses the bitcode
1721 // file.
1722 static bool bitcodereader_order(const User *lhs, const User *rhs) {
1723   // TODO: Implement.
1724   return true;
1725 }
1726
1727 static void WriteUseList(const Value *V, const ValueEnumerator &VE,
1728                          BitstreamWriter &Stream) {
1729
1730   // One or zero uses can't get out of order.
1731   if (V->use_empty() || V->hasNUses(1))
1732     return;
1733
1734   // Make a copy of the in-memory use-list for sorting.
1735   unsigned UseListSize = std::distance(V->use_begin(), V->use_end());
1736   SmallVector<const User*, 8> UseList;
1737   UseList.reserve(UseListSize);
1738   for (Value::const_use_iterator I = V->use_begin(), E = V->use_end();
1739        I != E; ++I) {
1740     const User *U = *I;
1741     UseList.push_back(U);
1742   }
1743
1744   // Sort the copy based on the order read by the BitcodeReader.
1745   std::sort(UseList.begin(), UseList.end(), bitcodereader_order);
1746
1747   // TODO: Generate a diff between the BitcodeWriter in-memory use-list and the
1748   // sorted list (i.e., the expected BitcodeReader in-memory use-list).
1749
1750   // TODO: Emit the USELIST_CODE_ENTRYs.
1751 }
1752
1753 static void WriteFunctionUseList(const Function *F, ValueEnumerator &VE,
1754                                  BitstreamWriter &Stream) {
1755   VE.incorporateFunction(*F);
1756
1757   for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
1758        AI != AE; ++AI)
1759     WriteUseList(AI, VE, Stream);
1760   for (Function::const_iterator BB = F->begin(), FE = F->end(); BB != FE;
1761        ++BB) {
1762     WriteUseList(BB, VE, Stream);
1763     for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end(); II != IE;
1764          ++II) {
1765       WriteUseList(II, VE, Stream);
1766       for (User::const_op_iterator OI = II->op_begin(), E = II->op_end();
1767            OI != E; ++OI) {
1768         if ((isa<Constant>(*OI) && !isa<GlobalValue>(*OI)) ||
1769             isa<InlineAsm>(*OI))
1770           WriteUseList(*OI, VE, Stream);
1771       }
1772     }
1773   }
1774   VE.purgeFunction();
1775 }
1776
1777 // Emit use-lists.
1778 static void WriteModuleUseLists(const Module *M, ValueEnumerator &VE,
1779                                 BitstreamWriter &Stream) {
1780   Stream.EnterSubblock(bitc::USELIST_BLOCK_ID, 3);
1781
1782   // XXX: this modifies the module, but in a way that should never change the
1783   // behavior of any pass or codegen in LLVM. The problem is that GVs may
1784   // contain entries in the use_list that do not exist in the Module and are
1785   // not stored in the .bc file.
1786   for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
1787        I != E; ++I)
1788     I->removeDeadConstantUsers();
1789
1790   // Write the global variables.
1791   for (Module::const_global_iterator GI = M->global_begin(),
1792          GE = M->global_end(); GI != GE; ++GI) {
1793     WriteUseList(GI, VE, Stream);
1794
1795     // Write the global variable initializers.
1796     if (GI->hasInitializer())
1797       WriteUseList(GI->getInitializer(), VE, Stream);
1798   }
1799
1800   // Write the functions.
1801   for (Module::const_iterator FI = M->begin(), FE = M->end(); FI != FE; ++FI) {
1802     WriteUseList(FI, VE, Stream);
1803     if (!FI->isDeclaration())
1804       WriteFunctionUseList(FI, VE, Stream);
1805   }
1806
1807   // Write the aliases.
1808   for (Module::const_alias_iterator AI = M->alias_begin(), AE = M->alias_end();
1809        AI != AE; ++AI) {
1810     WriteUseList(AI, VE, Stream);
1811     WriteUseList(AI->getAliasee(), VE, Stream);
1812   }
1813
1814   Stream.ExitBlock();
1815 }
1816
1817 /// WriteModule - Emit the specified module to the bitstream.
1818 static void WriteModule(const Module *M, BitstreamWriter &Stream) {
1819   Stream.EnterSubblock(bitc::MODULE_BLOCK_ID, 3);
1820
1821   SmallVector<unsigned, 1> Vals;
1822   unsigned CurVersion = 1;
1823   Vals.push_back(CurVersion);
1824   Stream.EmitRecord(bitc::MODULE_CODE_VERSION, Vals);
1825
1826   // Analyze the module, enumerating globals, functions, etc.
1827   ValueEnumerator VE(M);
1828
1829   // Emit blockinfo, which defines the standard abbreviations etc.
1830   WriteBlockInfo(VE, Stream);
1831
1832   // Emit information about parameter attributes.
1833   WriteAttributeTable(VE, Stream);
1834
1835   // Emit information describing all of the types in the module.
1836   WriteTypeTable(VE, Stream);
1837
1838   // Emit top-level description of module, including target triple, inline asm,
1839   // descriptors for global variables, and function prototype info.
1840   WriteModuleInfo(M, VE, Stream);
1841
1842   // Emit constants.
1843   WriteModuleConstants(VE, Stream);
1844
1845   // Emit metadata.
1846   WriteModuleMetadata(M, VE, Stream);
1847
1848   // Emit metadata.
1849   WriteModuleMetadataStore(M, Stream);
1850
1851   // Emit names for globals/functions etc.
1852   WriteValueSymbolTable(M->getValueSymbolTable(), VE, Stream);
1853
1854   // Emit use-lists.
1855   if (EnablePreserveUseListOrdering)
1856     WriteModuleUseLists(M, VE, Stream);
1857
1858   // Emit function bodies.
1859   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F)
1860     if (!F->isDeclaration())
1861       WriteFunction(*F, VE, Stream);
1862
1863   Stream.ExitBlock();
1864 }
1865
1866 /// EmitDarwinBCHeader - If generating a bc file on darwin, we have to emit a
1867 /// header and trailer to make it compatible with the system archiver.  To do
1868 /// this we emit the following header, and then emit a trailer that pads the
1869 /// file out to be a multiple of 16 bytes.
1870 ///
1871 /// struct bc_header {
1872 ///   uint32_t Magic;         // 0x0B17C0DE
1873 ///   uint32_t Version;       // Version, currently always 0.
1874 ///   uint32_t BitcodeOffset; // Offset to traditional bitcode file.
1875 ///   uint32_t BitcodeSize;   // Size of traditional bitcode file.
1876 ///   uint32_t CPUType;       // CPU specifier.
1877 ///   ... potentially more later ...
1878 /// };
1879 enum {
1880   DarwinBCSizeFieldOffset = 3*4, // Offset to bitcode_size.
1881   DarwinBCHeaderSize = 5*4
1882 };
1883
1884 static void WriteInt32ToBuffer(uint32_t Value, SmallVectorImpl<char> &Buffer,
1885                                uint32_t &Position) {
1886   Buffer[Position + 0] = (unsigned char) (Value >>  0);
1887   Buffer[Position + 1] = (unsigned char) (Value >>  8);
1888   Buffer[Position + 2] = (unsigned char) (Value >> 16);
1889   Buffer[Position + 3] = (unsigned char) (Value >> 24);
1890   Position += 4;
1891 }
1892
1893 static void EmitDarwinBCHeaderAndTrailer(SmallVectorImpl<char> &Buffer,
1894                                          const Triple &TT) {
1895   unsigned CPUType = ~0U;
1896
1897   // Match x86_64-*, i[3-9]86-*, powerpc-*, powerpc64-*, arm-*, thumb-*,
1898   // armv[0-9]-*, thumbv[0-9]-*, armv5te-*, or armv6t2-*. The CPUType is a magic
1899   // number from /usr/include/mach/machine.h.  It is ok to reproduce the
1900   // specific constants here because they are implicitly part of the Darwin ABI.
1901   enum {
1902     DARWIN_CPU_ARCH_ABI64      = 0x01000000,
1903     DARWIN_CPU_TYPE_X86        = 7,
1904     DARWIN_CPU_TYPE_ARM        = 12,
1905     DARWIN_CPU_TYPE_POWERPC    = 18
1906   };
1907
1908   Triple::ArchType Arch = TT.getArch();
1909   if (Arch == Triple::x86_64)
1910     CPUType = DARWIN_CPU_TYPE_X86 | DARWIN_CPU_ARCH_ABI64;
1911   else if (Arch == Triple::x86)
1912     CPUType = DARWIN_CPU_TYPE_X86;
1913   else if (Arch == Triple::ppc)
1914     CPUType = DARWIN_CPU_TYPE_POWERPC;
1915   else if (Arch == Triple::ppc64)
1916     CPUType = DARWIN_CPU_TYPE_POWERPC | DARWIN_CPU_ARCH_ABI64;
1917   else if (Arch == Triple::arm || Arch == Triple::thumb)
1918     CPUType = DARWIN_CPU_TYPE_ARM;
1919
1920   // Traditional Bitcode starts after header.
1921   assert(Buffer.size() >= DarwinBCHeaderSize &&
1922          "Expected header size to be reserved");
1923   unsigned BCOffset = DarwinBCHeaderSize;
1924   unsigned BCSize = Buffer.size()-DarwinBCHeaderSize;
1925
1926   // Write the magic and version.
1927   unsigned Position = 0;
1928   WriteInt32ToBuffer(0x0B17C0DE , Buffer, Position);
1929   WriteInt32ToBuffer(0          , Buffer, Position); // Version.
1930   WriteInt32ToBuffer(BCOffset   , Buffer, Position);
1931   WriteInt32ToBuffer(BCSize     , Buffer, Position);
1932   WriteInt32ToBuffer(CPUType    , Buffer, Position);
1933
1934   // If the file is not a multiple of 16 bytes, insert dummy padding.
1935   while (Buffer.size() & 15)
1936     Buffer.push_back(0);
1937 }
1938
1939 /// WriteBitcodeToFile - Write the specified module to the specified output
1940 /// stream.
1941 void llvm::WriteBitcodeToFile(const Module *M, raw_ostream &Out) {
1942   SmallVector<char, 1024> Buffer;
1943   Buffer.reserve(256*1024);
1944
1945   // If this is darwin or another generic macho target, reserve space for the
1946   // header.
1947   Triple TT(M->getTargetTriple());
1948   if (TT.isOSDarwin())
1949     Buffer.insert(Buffer.begin(), DarwinBCHeaderSize, 0);
1950
1951   // Emit the module into the buffer.
1952   {
1953     BitstreamWriter Stream(Buffer);
1954
1955     // Emit the file header.
1956     Stream.Emit((unsigned)'B', 8);
1957     Stream.Emit((unsigned)'C', 8);
1958     Stream.Emit(0x0, 4);
1959     Stream.Emit(0xC, 4);
1960     Stream.Emit(0xE, 4);
1961     Stream.Emit(0xD, 4);
1962
1963     // Emit the module.
1964     WriteModule(M, Stream);
1965   }
1966
1967   if (TT.isOSDarwin())
1968     EmitDarwinBCHeaderAndTrailer(Buffer, TT);
1969
1970   // Write the generated bitstream to "Out".
1971   Out.write((char*)&Buffer.front(), Buffer.size());
1972 }