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 the list of dependent libraries for the Module.
 396   for (Module::lib_iterator I = M->lib_begin(), E = M->lib_end(); I != E; ++I)
 397     WriteStringRecord(bitc::MODULE_CODE_DEPLIB, *I, 0/*TODO*/, Stream);
 398
 399   // Emit various pieces of data attached to a module.
 400   if (!M->getTargetTriple().empty())
 401     WriteStringRecord(bitc::MODULE_CODE_TRIPLE, M->getTargetTriple(),
 402                       0/*TODO*/, Stream);
 403   if (!M->getDataLayout().empty())
 404     WriteStringRecord(bitc::MODULE_CODE_DATALAYOUT, M->getDataLayout(),
 405                       0/*TODO*/, Stream);
 406   if (!M->getModuleInlineAsm().empty())
 407     WriteStringRecord(bitc::MODULE_CODE_ASM, M->getModuleInlineAsm(),
 408                       0/*TODO*/, Stream);
 409
 410   // Emit information about sections and GC, computing how many there are. Also
 411   // compute the maximum alignment value.
 412   std::map<std::string, unsigned> SectionMap;
 413   std::map<std::string, unsigned> GCMap;
 414   unsigned MaxAlignment = 0;
 415   unsigned MaxGlobalType = 0;
 416   for (Module::const_global_iterator GV = M->global_begin(),E = M->global_end();
 417        GV != E; ++GV) {
 418     MaxAlignment = std::max(MaxAlignment, GV->getAlignment());
 419     MaxGlobalType = std::max(MaxGlobalType, VE.getTypeID(GV->getType()));
 420     if (GV->hasSection()) {
 421       // Give section names unique ID's.
 422       unsigned &Entry = SectionMap[GV->getSection()];
 423       if (!Entry) {
 424         WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, GV->getSection(),
 425                           0/*TODO*/, Stream);
 426         Entry = SectionMap.size();
 427       }
 428     }
 429   }
 430   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F) {
 431     MaxAlignment = std::max(MaxAlignment, F->getAlignment());
 432     if (F->hasSection()) {
 433       // Give section names unique ID's.
 434       unsigned &Entry = SectionMap[F->getSection()];
 435       if (!Entry) {
 436         WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, F->getSection(),
 437                           0/*TODO*/, Stream);
 438         Entry = SectionMap.size();
 439       }
 440     }
 441     if (F->hasGC()) {
 442       // Same for GC names.
 443       unsigned &Entry = GCMap[F->getGC()];
 444       if (!Entry) {
 445         WriteStringRecord(bitc::MODULE_CODE_GCNAME, F->getGC(),
 446                           0/*TODO*/, Stream);
 447         Entry = GCMap.size();
 448       }
 449     }
 450   }
 451
 452   // Emit abbrev for globals, now that we know # sections and max alignment.
 453   unsigned SimpleGVarAbbrev = 0;
 454   if (!M->global_empty()) {
 455     // Add an abbrev for common globals with no visibility or thread localness.
 456     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 457     Abbv->Add(BitCodeAbbrevOp(bitc::MODULE_CODE_GLOBALVAR));
 458     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 459                               Log2_32_Ceil(MaxGlobalType+1)));
 460     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));      // Constant.
 461     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));        // Initializer.
 462     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));      // Linkage.
 463     if (MaxAlignment == 0)                                      // Alignment.
 464       Abbv->Add(BitCodeAbbrevOp(0));
 465     else {
 466       unsigned MaxEncAlignment = Log2_32(MaxAlignment)+1;
 467       Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 468                                Log2_32_Ceil(MaxEncAlignment+1)));
 469     }
 470     if (SectionMap.empty())                                    // Section.
 471       Abbv->Add(BitCodeAbbrevOp(0));
 472     else
 473       Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 474                                Log2_32_Ceil(SectionMap.size()+1)));
 475     // Don't bother emitting vis + thread local.
 476     SimpleGVarAbbrev = Stream.EmitAbbrev(Abbv);
 477   }
 478
 479   // Emit the global variable information.
 480   SmallVector<unsigned, 64> Vals;
 481   for (Module::const_global_iterator GV = M->global_begin(),E = M->global_end();
 482        GV != E; ++GV) {
 483     unsigned AbbrevToUse = 0;
 484
 485     // GLOBALVAR: [type, isconst, initid,
 486     //             linkage, alignment, section, visibility, threadlocal,
 487     //             unnamed_addr]
 488     Vals.push_back(VE.getTypeID(GV->getType()));
 489     Vals.push_back(GV->isConstant());
 490     Vals.push_back(GV->isDeclaration() ? 0 :
 491                    (VE.getValueID(GV->getInitializer()) + 1));
 492     Vals.push_back(getEncodedLinkage(GV));
 493     Vals.push_back(Log2_32(GV->getAlignment())+1);
 494     Vals.push_back(GV->hasSection() ? SectionMap[GV->getSection()] : 0);
 495     if (GV->isThreadLocal() ||
 496         GV->getVisibility() != GlobalValue::DefaultVisibility ||
 497         GV->hasUnnamedAddr()) {
 498       Vals.push_back(getEncodedVisibility(GV));
 499       Vals.push_back(getEncodedThreadLocalMode(GV));
 500       Vals.push_back(GV->hasUnnamedAddr());
 501     } else {
 502       AbbrevToUse = SimpleGVarAbbrev;
 503     }
 504
 505     Stream.EmitRecord(bitc::MODULE_CODE_GLOBALVAR, Vals, AbbrevToUse);
 506     Vals.clear();
 507   }
 508
 509   // Emit the function proto information.
 510   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F) {
 511     // FUNCTION:  [type, callingconv, isproto, linkage, paramattrs, alignment,
 512     //             section, visibility, gc, unnamed_addr]
 513     Vals.push_back(VE.getTypeID(F->getType()));
 514     Vals.push_back(F->getCallingConv());
 515     Vals.push_back(F->isDeclaration());
 516     Vals.push_back(getEncodedLinkage(F));
 517     Vals.push_back(VE.getAttributeID(F->getAttributes()));
 518     Vals.push_back(Log2_32(F->getAlignment())+1);
 519     Vals.push_back(F->hasSection() ? SectionMap[F->getSection()] : 0);
 520     Vals.push_back(getEncodedVisibility(F));
 521     Vals.push_back(F->hasGC() ? GCMap[F->getGC()] : 0);
 522     Vals.push_back(F->hasUnnamedAddr());
 523
 524     unsigned AbbrevToUse = 0;
 525     Stream.EmitRecord(bitc::MODULE_CODE_FUNCTION, Vals, AbbrevToUse);
 526     Vals.clear();
 527   }
 528
 529   // Emit the alias information.
 530   for (Module::const_alias_iterator AI = M->alias_begin(), E = M->alias_end();
 531        AI != E; ++AI) {
 532     // ALIAS: [alias type, aliasee val#, linkage, visibility]
 533     Vals.push_back(VE.getTypeID(AI->getType()));
 534     Vals.push_back(VE.getValueID(AI->getAliasee()));
 535     Vals.push_back(getEncodedLinkage(AI));
 536     Vals.push_back(getEncodedVisibility(AI));
 537     unsigned AbbrevToUse = 0;
 538     Stream.EmitRecord(bitc::MODULE_CODE_ALIAS, Vals, AbbrevToUse);
 539     Vals.clear();
 540   }
 541 }
 542
 543 static uint64_t GetOptimizationFlags(const Value *V) {
 544   uint64_t Flags = 0;
 545
 546   if (const OverflowingBinaryOperator *OBO =
 547         dyn_cast<OverflowingBinaryOperator>(V)) {
 548     if (OBO->hasNoSignedWrap())
 549       Flags |= 1 << bitc::OBO_NO_SIGNED_WRAP;
 550     if (OBO->hasNoUnsignedWrap())
 551       Flags |= 1 << bitc::OBO_NO_UNSIGNED_WRAP;
 552   } else if (const PossiblyExactOperator *PEO =
 553                dyn_cast<PossiblyExactOperator>(V)) {
 554     if (PEO->isExact())
 555       Flags |= 1 << bitc::PEO_EXACT;
 556   } else if (const FPMathOperator *FPMO =
 557              dyn_cast<const FPMathOperator>(V)) {
 558     if (FPMO->hasUnsafeAlgebra())
 559       Flags |= 1 << bitc::FMF_UNSAFE_ALGEBRA;
 560     if (FPMO->hasNoNaNs())
 561       Flags |= 1 << bitc::FMF_NO_NANS;
 562     if (FPMO->hasNoInfs())
 563       Flags |= 1 << bitc::FMF_NO_INFS;
 564     if (FPMO->hasNoSignedZeros())
 565       Flags |= 1 << bitc::FMF_NO_SIGNED_ZEROS;
 566     if (FPMO->hasAllowReciprocal())
 567       Flags |= 1 << bitc::FMF_ALLOW_RECIPROCAL;
 568   }
 569
 570   return Flags;
 571 }
 572
 573 static void WriteMDNode(const MDNode *N,
 574                         const ValueEnumerator &VE,
 575                         BitstreamWriter &Stream,
 576                         SmallVector<uint64_t, 64> &Record) {
 577   for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
 578     if (N->getOperand(i)) {
 579       Record.push_back(VE.getTypeID(N->getOperand(i)->getType()));
 580       Record.push_back(VE.getValueID(N->getOperand(i)));
 581     } else {
 582       Record.push_back(VE.getTypeID(Type::getVoidTy(N->getContext())));
 583       Record.push_back(0);
 584     }
 585   }
 586   unsigned MDCode = N->isFunctionLocal() ? bitc::METADATA_FN_NODE :
 587                                            bitc::METADATA_NODE;
 588   Stream.EmitRecord(MDCode, Record, 0);
 589   Record.clear();
 590 }
 591
 592 static void WriteModuleMetadata(const Module *M,
 593                                 const ValueEnumerator &VE,
 594                                 BitstreamWriter &Stream) {
 595   const ValueEnumerator::ValueList &Vals = VE.getMDValues();
 596   bool StartedMetadataBlock = false;
 597   unsigned MDSAbbrev = 0;
 598   SmallVector<uint64_t, 64> Record;
 599   for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
 600
 601     if (const MDNode *N = dyn_cast<MDNode>(Vals[i].first)) {
 602       if (!N->isFunctionLocal() || !N->getFunction()) {
 603         if (!StartedMetadataBlock) {
 604           Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 605           StartedMetadataBlock = true;
 606         }
 607         WriteMDNode(N, VE, Stream, Record);
 608       }
 609     } else if (const MDString *MDS = dyn_cast<MDString>(Vals[i].first)) {
 610       if (!StartedMetadataBlock)  {
 611         Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 612
 613         // Abbrev for METADATA_STRING.
 614         BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 615         Abbv->Add(BitCodeAbbrevOp(bitc::METADATA_STRING));
 616         Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 617         Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
 618         MDSAbbrev = Stream.EmitAbbrev(Abbv);
 619         StartedMetadataBlock = true;
 620       }
 621
 622       // Code: [strchar x N]
 623       Record.append(MDS->begin(), MDS->end());
 624
 625       // Emit the finished record.
 626       Stream.EmitRecord(bitc::METADATA_STRING, Record, MDSAbbrev);
 627       Record.clear();
 628     }
 629   }
 630
 631   // Write named metadata.
 632   for (Module::const_named_metadata_iterator I = M->named_metadata_begin(),
 633        E = M->named_metadata_end(); I != E; ++I) {
 634     const NamedMDNode *NMD = I;
 635     if (!StartedMetadataBlock)  {
 636       Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 637       StartedMetadataBlock = true;
 638     }
 639
 640     // Write name.
 641     StringRef Str = NMD->getName();
 642     for (unsigned i = 0, e = Str.size(); i != e; ++i)
 643       Record.push_back(Str[i]);
 644     Stream.EmitRecord(bitc::METADATA_NAME, Record, 0/*TODO*/);
 645     Record.clear();
 646
 647     // Write named metadata operands.
 648     for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
 649       Record.push_back(VE.getValueID(NMD->getOperand(i)));
 650     Stream.EmitRecord(bitc::METADATA_NAMED_NODE, Record, 0);
 651     Record.clear();
 652   }
 653
 654   if (StartedMetadataBlock)
 655     Stream.ExitBlock();
 656 }
 657
 658 static void WriteFunctionLocalMetadata(const Function &F,
 659                                        const ValueEnumerator &VE,
 660                                        BitstreamWriter &Stream) {
 661   bool StartedMetadataBlock = false;
 662   SmallVector<uint64_t, 64> Record;
 663   const SmallVector<const MDNode *, 8> &Vals = VE.getFunctionLocalMDValues();
 664   for (unsigned i = 0, e = Vals.size(); i != e; ++i)
 665     if (const MDNode *N = Vals[i])
 666       if (N->isFunctionLocal() && N->getFunction() == &F) {
 667         if (!StartedMetadataBlock) {
 668           Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 669           StartedMetadataBlock = true;
 670         }
 671         WriteMDNode(N, VE, Stream, Record);
 672       }
 673
 674   if (StartedMetadataBlock)
 675     Stream.ExitBlock();
 676 }
 677
 678 static void WriteMetadataAttachment(const Function &F,
 679                                     const ValueEnumerator &VE,
 680                                     BitstreamWriter &Stream) {
 681   Stream.EnterSubblock(bitc::METADATA_ATTACHMENT_ID, 3);
 682
 683   SmallVector<uint64_t, 64> Record;
 684
 685   // Write metadata attachments
 686   // METADATA_ATTACHMENT - [m x [value, [n x [id, mdnode]]]
 687   SmallVector<std::pair<unsigned, MDNode*>, 4> MDs;
 688
 689   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
 690     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
 691          I != E; ++I) {
 692       MDs.clear();
 693       I->getAllMetadataOtherThanDebugLoc(MDs);
 694
 695       // If no metadata, ignore instruction.
 696       if (MDs.empty()) continue;
 697
 698       Record.push_back(VE.getInstructionID(I));
 699
 700       for (unsigned i = 0, e = MDs.size(); i != e; ++i) {
 701         Record.push_back(MDs[i].first);
 702         Record.push_back(VE.getValueID(MDs[i].second));
 703       }
 704       Stream.EmitRecord(bitc::METADATA_ATTACHMENT, Record, 0);
 705       Record.clear();
 706     }
 707
 708   Stream.ExitBlock();
 709 }
 710
 711 static void WriteModuleMetadataStore(const Module *M, BitstreamWriter &Stream) {
 712   SmallVector<uint64_t, 64> Record;
 713
 714   // Write metadata kinds
 715   // METADATA_KIND - [n x [id, name]]
 716   SmallVector<StringRef, 4> Names;
 717   M->getMDKindNames(Names);
 718
 719   if (Names.empty()) return;
 720
 721   Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 722
 723   for (unsigned MDKindID = 0, e = Names.size(); MDKindID != e; ++MDKindID) {
 724     Record.push_back(MDKindID);
 725     StringRef KName = Names[MDKindID];
 726     Record.append(KName.begin(), KName.end());
 727
 728     Stream.EmitRecord(bitc::METADATA_KIND, Record, 0);
 729     Record.clear();
 730   }
 731
 732   Stream.ExitBlock();
 733 }
 734
 735 static void emitSignedInt64(SmallVectorImpl<uint64_t> &Vals, uint64_t V) {
 736   if ((int64_t)V >= 0)
 737     Vals.push_back(V << 1);
 738   else
 739     Vals.push_back((-V << 1) | 1);
 740 }
 741
 742 static void EmitAPInt(SmallVectorImpl<uint64_t> &Vals,
 743                       unsigned &Code, unsigned &AbbrevToUse, const APInt &Val,
 744                       bool EmitSizeForWideNumbers = false
 745                       ) {
 746   if (Val.getBitWidth() <= 64) {
 747     uint64_t V = Val.getSExtValue();
 748     emitSignedInt64(Vals, V);
 749     Code = bitc::CST_CODE_INTEGER;
 750     AbbrevToUse = CONSTANTS_INTEGER_ABBREV;
 751   } else {
 752     // Wide integers, > 64 bits in size.
 753     // We have an arbitrary precision integer value to write whose
 754     // bit width is > 64. However, in canonical unsigned integer
 755     // format it is likely that the high bits are going to be zero.
 756     // So, we only write the number of active words.
 757     unsigned NWords = Val.getActiveWords();
 758
 759     if (EmitSizeForWideNumbers)
 760       Vals.push_back(NWords);
 761
 762     const uint64_t *RawWords = Val.getRawData();
 763     for (unsigned i = 0; i != NWords; ++i) {
 764       emitSignedInt64(Vals, RawWords[i]);
 765     }
 766     Code = bitc::CST_CODE_WIDE_INTEGER;
 767   }
 768 }
 769
 770 static void WriteConstants(unsigned FirstVal, unsigned LastVal,
 771                            const ValueEnumerator &VE,
 772                            BitstreamWriter &Stream, bool isGlobal) {
 773   if (FirstVal == LastVal) return;
 774
 775   Stream.EnterSubblock(bitc::CONSTANTS_BLOCK_ID, 4);
 776
 777   unsigned AggregateAbbrev = 0;
 778   unsigned String8Abbrev = 0;
 779   unsigned CString7Abbrev = 0;
 780   unsigned CString6Abbrev = 0;
 781   // If this is a constant pool for the module, emit module-specific abbrevs.
 782   if (isGlobal) {
 783     // Abbrev for CST_CODE_AGGREGATE.
 784     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 785     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_AGGREGATE));
 786     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 787     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, Log2_32_Ceil(LastVal+1)));
 788     AggregateAbbrev = Stream.EmitAbbrev(Abbv);
 789
 790     // Abbrev for CST_CODE_STRING.
 791     Abbv = new BitCodeAbbrev();
 792     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_STRING));
 793     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 794     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
 795     String8Abbrev = Stream.EmitAbbrev(Abbv);
 796     // Abbrev for CST_CODE_CSTRING.
 797     Abbv = new BitCodeAbbrev();
 798     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CSTRING));
 799     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 800     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
 801     CString7Abbrev = Stream.EmitAbbrev(Abbv);
 802     // Abbrev for CST_CODE_CSTRING.
 803     Abbv = new BitCodeAbbrev();
 804     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CSTRING));
 805     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 806     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
 807     CString6Abbrev = Stream.EmitAbbrev(Abbv);
 808   }
 809
 810   SmallVector<uint64_t, 64> Record;
 811
 812   const ValueEnumerator::ValueList &Vals = VE.getValues();
 813   Type *LastTy = 0;
 814   for (unsigned i = FirstVal; i != LastVal; ++i) {
 815     const Value *V = Vals[i].first;
 816     // If we need to switch types, do so now.
 817     if (V->getType() != LastTy) {
 818       LastTy = V->getType();
 819       Record.push_back(VE.getTypeID(LastTy));
 820       Stream.EmitRecord(bitc::CST_CODE_SETTYPE, Record,
 821                         CONSTANTS_SETTYPE_ABBREV);
 822       Record.clear();
 823     }
 824
 825     if (const InlineAsm *IA = dyn_cast<InlineAsm>(V)) {
 826       Record.push_back(unsigned(IA->hasSideEffects()) |
 827                        unsigned(IA->isAlignStack()) << 1 |
 828                        unsigned(IA->getDialect()&1) << 2);
 829
 830       // Add the asm string.
 831       const std::string &AsmStr = IA->getAsmString();
 832       Record.push_back(AsmStr.size());
 833       for (unsigned i = 0, e = AsmStr.size(); i != e; ++i)
 834         Record.push_back(AsmStr[i]);
 835
 836       // Add the constraint string.
 837       const std::string &ConstraintStr = IA->getConstraintString();
 838       Record.push_back(ConstraintStr.size());
 839       for (unsigned i = 0, e = ConstraintStr.size(); i != e; ++i)
 840         Record.push_back(ConstraintStr[i]);
 841       Stream.EmitRecord(bitc::CST_CODE_INLINEASM, Record);
 842       Record.clear();
 843       continue;
 844     }
 845     const Constant *C = cast<Constant>(V);
 846     unsigned Code = -1U;
 847     unsigned AbbrevToUse = 0;
 848     if (C->isNullValue()) {
 849       Code = bitc::CST_CODE_NULL;
 850     } else if (isa<UndefValue>(C)) {
 851       Code = bitc::CST_CODE_UNDEF;
 852     } else if (const ConstantInt *IV = dyn_cast<ConstantInt>(C)) {
 853       EmitAPInt(Record, Code, AbbrevToUse, IV->getValue());
 854     } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
 855       Code = bitc::CST_CODE_FLOAT;
 856       Type *Ty = CFP->getType();
 857       if (Ty->isHalfTy() || Ty->isFloatTy() || Ty->isDoubleTy()) {
 858         Record.push_back(CFP->getValueAPF().bitcastToAPInt().getZExtValue());
 859       } else if (Ty->isX86_FP80Ty()) {
 860         // api needed to prevent premature destruction
 861         // bits are not in the same order as a normal i80 APInt, compensate.
 862         APInt api = CFP->getValueAPF().bitcastToAPInt();
 863         const uint64_t *p = api.getRawData();
 864         Record.push_back((p[1] << 48) | (p[0] >> 16));
 865         Record.push_back(p[0] & 0xffffLL);
 866       } else if (Ty->isFP128Ty() || Ty->isPPC_FP128Ty()) {
 867         APInt api = CFP->getValueAPF().bitcastToAPInt();
 868         const uint64_t *p = api.getRawData();
 869         Record.push_back(p[0]);
 870         Record.push_back(p[1]);
 871       } else {
 872         assert (0 && "Unknown FP type!");
 873       }
 874     } else if (isa<ConstantDataSequential>(C) &&
 875                cast<ConstantDataSequential>(C)->isString()) {
 876       const ConstantDataSequential *Str = cast<ConstantDataSequential>(C);
 877       // Emit constant strings specially.
 878       unsigned NumElts = Str->getNumElements();
 879       // If this is a null-terminated string, use the denser CSTRING encoding.
 880       if (Str->isCString()) {
 881         Code = bitc::CST_CODE_CSTRING;
 882         --NumElts;  // Don't encode the null, which isn't allowed by char6.
 883       } else {
 884         Code = bitc::CST_CODE_STRING;
 885         AbbrevToUse = String8Abbrev;
 886       }
 887       bool isCStr7 = Code == bitc::CST_CODE_CSTRING;
 888       bool isCStrChar6 = Code == bitc::CST_CODE_CSTRING;
 889       for (unsigned i = 0; i != NumElts; ++i) {
 890         unsigned char V = Str->getElementAsInteger(i);
 891         Record.push_back(V);
 892         isCStr7 &= (V & 128) == 0;
 893         if (isCStrChar6)
 894           isCStrChar6 = BitCodeAbbrevOp::isChar6(V);
 895       }
 896
 897       if (isCStrChar6)
 898         AbbrevToUse = CString6Abbrev;
 899       else if (isCStr7)
 900         AbbrevToUse = CString7Abbrev;
 901     } else if (const ConstantDataSequential *CDS =
 902                   dyn_cast<ConstantDataSequential>(C)) {
 903       Code = bitc::CST_CODE_DATA;
 904       Type *EltTy = CDS->getType()->getElementType();
 905       if (isa<IntegerType>(EltTy)) {
 906         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i)
 907           Record.push_back(CDS->getElementAsInteger(i));
 908       } else if (EltTy->isFloatTy()) {
 909         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
 910           union { float F; uint32_t I; };
 911           F = CDS->getElementAsFloat(i);
 912           Record.push_back(I);
 913         }
 914       } else {
 915         assert(EltTy->isDoubleTy() && "Unknown ConstantData element type");
 916         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
 917           union { double F; uint64_t I; };
 918           F = CDS->getElementAsDouble(i);
 919           Record.push_back(I);
 920         }
 921       }
 922     } else if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
 923                isa<ConstantVector>(C)) {
 924       Code = bitc::CST_CODE_AGGREGATE;
 925       for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
 926         Record.push_back(VE.getValueID(C->getOperand(i)));
 927       AbbrevToUse = AggregateAbbrev;
 928     } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
 929       switch (CE->getOpcode()) {
 930       default:
 931         if (Instruction::isCast(CE->getOpcode())) {
 932           Code = bitc::CST_CODE_CE_CAST;
 933           Record.push_back(GetEncodedCastOpcode(CE->getOpcode()));
 934           Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
 935           Record.push_back(VE.getValueID(C->getOperand(0)));
 936           AbbrevToUse = CONSTANTS_CE_CAST_Abbrev;
 937         } else {
 938           assert(CE->getNumOperands() == 2 && "Unknown constant expr!");
 939           Code = bitc::CST_CODE_CE_BINOP;
 940           Record.push_back(GetEncodedBinaryOpcode(CE->getOpcode()));
 941           Record.push_back(VE.getValueID(C->getOperand(0)));
 942           Record.push_back(VE.getValueID(C->getOperand(1)));
 943           uint64_t Flags = GetOptimizationFlags(CE);
 944           if (Flags != 0)
 945             Record.push_back(Flags);
 946         }
 947         break;
 948       case Instruction::GetElementPtr:
 949         Code = bitc::CST_CODE_CE_GEP;
 950         if (cast<GEPOperator>(C)->isInBounds())
 951           Code = bitc::CST_CODE_CE_INBOUNDS_GEP;
 952         for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) {
 953           Record.push_back(VE.getTypeID(C->getOperand(i)->getType()));
 954           Record.push_back(VE.getValueID(C->getOperand(i)));
 955         }
 956         break;
 957       case Instruction::Select:
 958         Code = bitc::CST_CODE_CE_SELECT;
 959         Record.push_back(VE.getValueID(C->getOperand(0)));
 960         Record.push_back(VE.getValueID(C->getOperand(1)));
 961         Record.push_back(VE.getValueID(C->getOperand(2)));
 962         break;
 963       case Instruction::ExtractElement:
 964         Code = bitc::CST_CODE_CE_EXTRACTELT;
 965         Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
 966         Record.push_back(VE.getValueID(C->getOperand(0)));
 967         Record.push_back(VE.getValueID(C->getOperand(1)));
 968         break;
 969       case Instruction::InsertElement:
 970         Code = bitc::CST_CODE_CE_INSERTELT;
 971         Record.push_back(VE.getValueID(C->getOperand(0)));
 972         Record.push_back(VE.getValueID(C->getOperand(1)));
 973         Record.push_back(VE.getValueID(C->getOperand(2)));
 974         break;
 975       case Instruction::ShuffleVector:
 976         // If the return type and argument types are the same, this is a
 977         // standard shufflevector instruction.  If the types are different,
 978         // then the shuffle is widening or truncating the input vectors, and
 979         // the argument type must also be encoded.
 980         if (C->getType() == C->getOperand(0)->getType()) {
 981           Code = bitc::CST_CODE_CE_SHUFFLEVEC;
 982         } else {
 983           Code = bitc::CST_CODE_CE_SHUFVEC_EX;
 984           Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
 985         }
 986         Record.push_back(VE.getValueID(C->getOperand(0)));
 987         Record.push_back(VE.getValueID(C->getOperand(1)));
 988         Record.push_back(VE.getValueID(C->getOperand(2)));
 989         break;
 990       case Instruction::ICmp:
 991       case Instruction::FCmp:
 992         Code = bitc::CST_CODE_CE_CMP;
 993         Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
 994         Record.push_back(VE.getValueID(C->getOperand(0)));
 995         Record.push_back(VE.getValueID(C->getOperand(1)));
 996         Record.push_back(CE->getPredicate());
 997         break;
 998       }
 999     } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
1000       Code = bitc::CST_CODE_BLOCKADDRESS;
1001       Record.push_back(VE.getTypeID(BA->getFunction()->getType()));
1002       Record.push_back(VE.getValueID(BA->getFunction()));
1003       Record.push_back(VE.getGlobalBasicBlockID(BA->getBasicBlock()));
1004     } else {
1005 #ifndef NDEBUG
1006       C->dump();
1007 #endif
1008       llvm_unreachable("Unknown constant!");
1009     }
1010     Stream.EmitRecord(Code, Record, AbbrevToUse);
1011     Record.clear();
1012   }
1013
1014   Stream.ExitBlock();
1015 }
1016
1017 static void WriteModuleConstants(const ValueEnumerator &VE,
1018                                  BitstreamWriter &Stream) {
1019   const ValueEnumerator::ValueList &Vals = VE.getValues();
1020
1021   // Find the first constant to emit, which is the first non-globalvalue value.
1022   // We know globalvalues have been emitted by WriteModuleInfo.
1023   for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
1024     if (!isa<GlobalValue>(Vals[i].first)) {
1025       WriteConstants(i, Vals.size(), VE, Stream, true);
1026       return;
1027     }
1028   }
1029 }
1030
1031 /// PushValueAndType - The file has to encode both the value and type id for
1032 /// many values, because we need to know what type to create for forward
1033 /// references.  However, most operands are not forward references, so this type
1034 /// field is not needed.
1035 ///
1036 /// This function adds V's value ID to Vals.  If the value ID is higher than the
1037 /// instruction ID, then it is a forward reference, and it also includes the
1038 /// type ID.  The value ID that is written is encoded relative to the InstID.
1039 static bool PushValueAndType(const Value *V, unsigned InstID,
1040                              SmallVector<unsigned, 64> &Vals,
1041                              ValueEnumerator &VE) {
1042   unsigned ValID = VE.getValueID(V);
1043   // Make encoding relative to the InstID.
1044   Vals.push_back(InstID - ValID);
1045   if (ValID >= InstID) {
1046     Vals.push_back(VE.getTypeID(V->getType()));
1047     return true;
1048   }
1049   return false;
1050 }
1051
1052 /// pushValue - Like PushValueAndType, but where the type of the value is
1053 /// omitted (perhaps it was already encoded in an earlier operand).
1054 static void pushValue(const Value *V, unsigned InstID,
1055                       SmallVector<unsigned, 64> &Vals,
1056                       ValueEnumerator &VE) {
1057   unsigned ValID = VE.getValueID(V);
1058   Vals.push_back(InstID - ValID);
1059 }
1060
1061 static void pushValue64(const Value *V, unsigned InstID,
1062                         SmallVector<uint64_t, 128> &Vals,
1063                         ValueEnumerator &VE) {
1064   uint64_t ValID = VE.getValueID(V);
1065   Vals.push_back(InstID - ValID);
1066 }
1067
1068 static void pushValueSigned(const Value *V, unsigned InstID,
1069                             SmallVector<uint64_t, 128> &Vals,
1070                             ValueEnumerator &VE) {
1071   unsigned ValID = VE.getValueID(V);
1072   int64_t diff = ((int32_t)InstID - (int32_t)ValID);
1073   emitSignedInt64(Vals, diff);
1074 }
1075
1076 /// WriteInstruction - Emit an instruction to the specified stream.
1077 static void WriteInstruction(const Instruction &I, unsigned InstID,
1078                              ValueEnumerator &VE, BitstreamWriter &Stream,
1079                              SmallVector<unsigned, 64> &Vals) {
1080   unsigned Code = 0;
1081   unsigned AbbrevToUse = 0;
1082   VE.setInstructionID(&I);
1083   switch (I.getOpcode()) {
1084   default:
1085     if (Instruction::isCast(I.getOpcode())) {
1086       Code = bitc::FUNC_CODE_INST_CAST;
1087       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1088         AbbrevToUse = FUNCTION_INST_CAST_ABBREV;
1089       Vals.push_back(VE.getTypeID(I.getType()));
1090       Vals.push_back(GetEncodedCastOpcode(I.getOpcode()));
1091     } else {
1092       assert(isa<BinaryOperator>(I) && "Unknown instruction!");
1093       Code = bitc::FUNC_CODE_INST_BINOP;
1094       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1095         AbbrevToUse = FUNCTION_INST_BINOP_ABBREV;
1096       pushValue(I.getOperand(1), InstID, Vals, VE);
1097       Vals.push_back(GetEncodedBinaryOpcode(I.getOpcode()));
1098       uint64_t Flags = GetOptimizationFlags(&I);
1099       if (Flags != 0) {
1100         if (AbbrevToUse == FUNCTION_INST_BINOP_ABBREV)
1101           AbbrevToUse = FUNCTION_INST_BINOP_FLAGS_ABBREV;
1102         Vals.push_back(Flags);
1103       }
1104     }
1105     break;
1106
1107   case Instruction::GetElementPtr:
1108     Code = bitc::FUNC_CODE_INST_GEP;
1109     if (cast<GEPOperator>(&I)->isInBounds())
1110       Code = bitc::FUNC_CODE_INST_INBOUNDS_GEP;
1111     for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
1112       PushValueAndType(I.getOperand(i), InstID, Vals, VE);
1113     break;
1114   case Instruction::ExtractValue: {
1115     Code = bitc::FUNC_CODE_INST_EXTRACTVAL;
1116     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1117     const ExtractValueInst *EVI = cast<ExtractValueInst>(&I);
1118     for (const unsigned *i = EVI->idx_begin(), *e = EVI->idx_end(); i != e; ++i)
1119       Vals.push_back(*i);
1120     break;
1121   }
1122   case Instruction::InsertValue: {
1123     Code = bitc::FUNC_CODE_INST_INSERTVAL;
1124     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1125     PushValueAndType(I.getOperand(1), InstID, Vals, VE);
1126     const InsertValueInst *IVI = cast<InsertValueInst>(&I);
1127     for (const unsigned *i = IVI->idx_begin(), *e = IVI->idx_end(); i != e; ++i)
1128       Vals.push_back(*i);
1129     break;
1130   }
1131   case Instruction::Select:
1132     Code = bitc::FUNC_CODE_INST_VSELECT;
1133     PushValueAndType(I.getOperand(1), InstID, Vals, VE);
1134     pushValue(I.getOperand(2), InstID, Vals, VE);
1135     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1136     break;
1137   case Instruction::ExtractElement:
1138     Code = bitc::FUNC_CODE_INST_EXTRACTELT;
1139     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1140     pushValue(I.getOperand(1), InstID, Vals, VE);
1141     break;
1142   case Instruction::InsertElement:
1143     Code = bitc::FUNC_CODE_INST_INSERTELT;
1144     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1145     pushValue(I.getOperand(1), InstID, Vals, VE);
1146     pushValue(I.getOperand(2), InstID, Vals, VE);
1147     break;
1148   case Instruction::ShuffleVector:
1149     Code = bitc::FUNC_CODE_INST_SHUFFLEVEC;
1150     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1151     pushValue(I.getOperand(1), InstID, Vals, VE);
1152     pushValue(I.getOperand(2), InstID, Vals, VE);
1153     break;
1154   case Instruction::ICmp:
1155   case Instruction::FCmp:
1156     // compare returning Int1Ty or vector of Int1Ty
1157     Code = bitc::FUNC_CODE_INST_CMP2;
1158     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1159     pushValue(I.getOperand(1), InstID, Vals, VE);
1160     Vals.push_back(cast<CmpInst>(I).getPredicate());
1161     break;
1162
1163   case Instruction::Ret:
1164     {
1165       Code = bitc::FUNC_CODE_INST_RET;
1166       unsigned NumOperands = I.getNumOperands();
1167       if (NumOperands == 0)
1168         AbbrevToUse = FUNCTION_INST_RET_VOID_ABBREV;
1169       else if (NumOperands == 1) {
1170         if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1171           AbbrevToUse = FUNCTION_INST_RET_VAL_ABBREV;
1172       } else {
1173         for (unsigned i = 0, e = NumOperands; i != e; ++i)
1174           PushValueAndType(I.getOperand(i), InstID, Vals, VE);
1175       }
1176     }
1177     break;
1178   case Instruction::Br:
1179     {
1180       Code = bitc::FUNC_CODE_INST_BR;
1181       BranchInst &II = cast<BranchInst>(I);
1182       Vals.push_back(VE.getValueID(II.getSuccessor(0)));
1183       if (II.isConditional()) {
1184         Vals.push_back(VE.getValueID(II.getSuccessor(1)));
1185         pushValue(II.getCondition(), InstID, Vals, VE);
1186       }
1187     }
1188     break;
1189   case Instruction::Switch:
1190     {
1191       // Redefine Vals, since here we need to use 64 bit values
1192       // explicitly to store large APInt numbers.
1193       SmallVector<uint64_t, 128> Vals64;
1194
1195       Code = bitc::FUNC_CODE_INST_SWITCH;
1196       SwitchInst &SI = cast<SwitchInst>(I);
1197
1198       uint32_t SwitchRecordHeader = SI.hash() | (SWITCH_INST_MAGIC << 16);
1199       Vals64.push_back(SwitchRecordHeader);
1200
1201       Vals64.push_back(VE.getTypeID(SI.getCondition()->getType()));
1202       pushValue64(SI.getCondition(), InstID, Vals64, VE);
1203       Vals64.push_back(VE.getValueID(SI.getDefaultDest()));
1204       Vals64.push_back(SI.getNumCases());
1205       for (SwitchInst::CaseIt i = SI.case_begin(), e = SI.case_end();
1206            i != e; ++i) {
1207         IntegersSubset& CaseRanges = i.getCaseValueEx();
1208         unsigned Code, Abbrev; // will unused.
1209
1210         if (CaseRanges.isSingleNumber()) {
1211           Vals64.push_back(1/*NumItems = 1*/);
1212           Vals64.push_back(true/*IsSingleNumber = true*/);
1213           EmitAPInt(Vals64, Code, Abbrev, CaseRanges.getSingleNumber(0), true);
1214         } else {
1215
1216           Vals64.push_back(CaseRanges.getNumItems());
1217
1218           if (CaseRanges.isSingleNumbersOnly()) {
1219             for (unsigned ri = 0, rn = CaseRanges.getNumItems();
1220                  ri != rn; ++ri) {
1221
1222               Vals64.push_back(true/*IsSingleNumber = true*/);
1223
1224               EmitAPInt(Vals64, Code, Abbrev,
1225                         CaseRanges.getSingleNumber(ri), true);
1226             }
1227           } else
1228             for (unsigned ri = 0, rn = CaseRanges.getNumItems();
1229                  ri != rn; ++ri) {
1230               IntegersSubset::Range r = CaseRanges.getItem(ri);
1231               bool IsSingleNumber = CaseRanges.isSingleNumber(ri);
1232
1233               Vals64.push_back(IsSingleNumber);
1234
1235               EmitAPInt(Vals64, Code, Abbrev, r.getLow(), true);
1236               if (!IsSingleNumber)
1237                 EmitAPInt(Vals64, Code, Abbrev, r.getHigh(), true);
1238             }
1239         }
1240         Vals64.push_back(VE.getValueID(i.getCaseSuccessor()));
1241       }
1242
1243       Stream.EmitRecord(Code, Vals64, AbbrevToUse);
1244
1245       // Also do expected action - clear external Vals collection:
1246       Vals.clear();
1247       return;
1248     }
1249     break;
1250   case Instruction::IndirectBr:
1251     Code = bitc::FUNC_CODE_INST_INDIRECTBR;
1252     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));
1253     // Encode the address operand as relative, but not the basic blocks.
1254     pushValue(I.getOperand(0), InstID, Vals, VE);
1255     for (unsigned i = 1, e = I.getNumOperands(); i != e; ++i)
1256       Vals.push_back(VE.getValueID(I.getOperand(i)));
1257     break;
1258
1259   case Instruction::Invoke: {
1260     const InvokeInst *II = cast<InvokeInst>(&I);
1261     const Value *Callee(II->getCalledValue());
1262     PointerType *PTy = cast<PointerType>(Callee->getType());
1263     FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1264     Code = bitc::FUNC_CODE_INST_INVOKE;
1265
1266     Vals.push_back(VE.getAttributeID(II->getAttributes()));
1267     Vals.push_back(II->getCallingConv());
1268     Vals.push_back(VE.getValueID(II->getNormalDest()));
1269     Vals.push_back(VE.getValueID(II->getUnwindDest()));
1270     PushValueAndType(Callee, InstID, Vals, VE);
1271
1272     // Emit value #'s for the fixed parameters.
1273     for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
1274       pushValue(I.getOperand(i), InstID, Vals, VE);  // fixed param.
1275
1276     // Emit type/value pairs for varargs params.
1277     if (FTy->isVarArg()) {
1278       for (unsigned i = FTy->getNumParams(), e = I.getNumOperands()-3;
1279            i != e; ++i)
1280         PushValueAndType(I.getOperand(i), InstID, Vals, VE); // vararg
1281     }
1282     break;
1283   }
1284   case Instruction::Resume:
1285     Code = bitc::FUNC_CODE_INST_RESUME;
1286     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1287     break;
1288   case Instruction::Unreachable:
1289     Code = bitc::FUNC_CODE_INST_UNREACHABLE;
1290     AbbrevToUse = FUNCTION_INST_UNREACHABLE_ABBREV;
1291     break;
1292
1293   case Instruction::PHI: {
1294     const PHINode &PN = cast<PHINode>(I);
1295     Code = bitc::FUNC_CODE_INST_PHI;
1296     // With the newer instruction encoding, forward references could give
1297     // negative valued IDs.  This is most common for PHIs, so we use
1298     // signed VBRs.
1299     SmallVector<uint64_t, 128> Vals64;
1300     Vals64.push_back(VE.getTypeID(PN.getType()));
1301     for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
1302       pushValueSigned(PN.getIncomingValue(i), InstID, Vals64, VE);
1303       Vals64.push_back(VE.getValueID(PN.getIncomingBlock(i)));
1304     }
1305     // Emit a Vals64 vector and exit.
1306     Stream.EmitRecord(Code, Vals64, AbbrevToUse);
1307     Vals64.clear();
1308     return;
1309   }
1310
1311   case Instruction::LandingPad: {
1312     const LandingPadInst &LP = cast<LandingPadInst>(I);
1313     Code = bitc::FUNC_CODE_INST_LANDINGPAD;
1314     Vals.push_back(VE.getTypeID(LP.getType()));
1315     PushValueAndType(LP.getPersonalityFn(), InstID, Vals, VE);
1316     Vals.push_back(LP.isCleanup());
1317     Vals.push_back(LP.getNumClauses());
1318     for (unsigned I = 0, E = LP.getNumClauses(); I != E; ++I) {
1319       if (LP.isCatch(I))
1320         Vals.push_back(LandingPadInst::Catch);
1321       else
1322         Vals.push_back(LandingPadInst::Filter);
1323       PushValueAndType(LP.getClause(I), InstID, Vals, VE);
1324     }
1325     break;
1326   }
1327
1328   case Instruction::Alloca:
1329     Code = bitc::FUNC_CODE_INST_ALLOCA;
1330     Vals.push_back(VE.getTypeID(I.getType()));
1331     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));
1332     Vals.push_back(VE.getValueID(I.getOperand(0))); // size.
1333     Vals.push_back(Log2_32(cast<AllocaInst>(I).getAlignment())+1);
1334     break;
1335
1336   case Instruction::Load:
1337     if (cast<LoadInst>(I).isAtomic()) {
1338       Code = bitc::FUNC_CODE_INST_LOADATOMIC;
1339       PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1340     } else {
1341       Code = bitc::FUNC_CODE_INST_LOAD;
1342       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))  // ptr
1343         AbbrevToUse = FUNCTION_INST_LOAD_ABBREV;
1344     }
1345     Vals.push_back(Log2_32(cast<LoadInst>(I).getAlignment())+1);
1346     Vals.push_back(cast<LoadInst>(I).isVolatile());
1347     if (cast<LoadInst>(I).isAtomic()) {
1348       Vals.push_back(GetEncodedOrdering(cast<LoadInst>(I).getOrdering()));
1349       Vals.push_back(GetEncodedSynchScope(cast<LoadInst>(I).getSynchScope()));
1350     }
1351     break;
1352   case Instruction::Store:
1353     if (cast<StoreInst>(I).isAtomic())
1354       Code = bitc::FUNC_CODE_INST_STOREATOMIC;
1355     else
1356       Code = bitc::FUNC_CODE_INST_STORE;
1357     PushValueAndType(I.getOperand(1), InstID, Vals, VE);  // ptrty + ptr
1358     pushValue(I.getOperand(0), InstID, Vals, VE);         // val.
1359     Vals.push_back(Log2_32(cast<StoreInst>(I).getAlignment())+1);
1360     Vals.push_back(cast<StoreInst>(I).isVolatile());
1361     if (cast<StoreInst>(I).isAtomic()) {
1362       Vals.push_back(GetEncodedOrdering(cast<StoreInst>(I).getOrdering()));
1363       Vals.push_back(GetEncodedSynchScope(cast<StoreInst>(I).getSynchScope()));
1364     }
1365     break;
1366   case Instruction::AtomicCmpXchg:
1367     Code = bitc::FUNC_CODE_INST_CMPXCHG;
1368     PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // ptrty + ptr
1369     pushValue(I.getOperand(1), InstID, Vals, VE);         // cmp.
1370     pushValue(I.getOperand(2), InstID, Vals, VE);         // newval.
1371     Vals.push_back(cast<AtomicCmpXchgInst>(I).isVolatile());
1372     Vals.push_back(GetEncodedOrdering(
1373                      cast<AtomicCmpXchgInst>(I).getOrdering()));
1374     Vals.push_back(GetEncodedSynchScope(
1375                      cast<AtomicCmpXchgInst>(I).getSynchScope()));
1376     break;
1377   case Instruction::AtomicRMW:
1378     Code = bitc::FUNC_CODE_INST_ATOMICRMW;
1379     PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // ptrty + ptr
1380     pushValue(I.getOperand(1), InstID, Vals, VE);         // val.
1381     Vals.push_back(GetEncodedRMWOperation(
1382                      cast<AtomicRMWInst>(I).getOperation()));
1383     Vals.push_back(cast<AtomicRMWInst>(I).isVolatile());
1384     Vals.push_back(GetEncodedOrdering(cast<AtomicRMWInst>(I).getOrdering()));
1385     Vals.push_back(GetEncodedSynchScope(
1386                      cast<AtomicRMWInst>(I).getSynchScope()));
1387     break;
1388   case Instruction::Fence:
1389     Code = bitc::FUNC_CODE_INST_FENCE;
1390     Vals.push_back(GetEncodedOrdering(cast<FenceInst>(I).getOrdering()));
1391     Vals.push_back(GetEncodedSynchScope(cast<FenceInst>(I).getSynchScope()));
1392     break;
1393   case Instruction::Call: {
1394     const CallInst &CI = cast<CallInst>(I);
1395     PointerType *PTy = cast<PointerType>(CI.getCalledValue()->getType());
1396     FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1397
1398     Code = bitc::FUNC_CODE_INST_CALL;
1399
1400     Vals.push_back(VE.getAttributeID(CI.getAttributes()));
1401     Vals.push_back((CI.getCallingConv() << 1) | unsigned(CI.isTailCall()));
1402     PushValueAndType(CI.getCalledValue(), InstID, Vals, VE);  // Callee
1403
1404     // Emit value #'s for the fixed parameters.
1405     for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i) {
1406       // Check for labels (can happen with asm labels).
1407       if (FTy->getParamType(i)->isLabelTy())
1408         Vals.push_back(VE.getValueID(CI.getArgOperand(i)));
1409       else
1410         pushValue(CI.getArgOperand(i), InstID, Vals, VE);  // fixed param.
1411     }
1412
1413     // Emit type/value pairs for varargs params.
1414     if (FTy->isVarArg()) {
1415       for (unsigned i = FTy->getNumParams(), e = CI.getNumArgOperands();
1416            i != e; ++i)
1417         PushValueAndType(CI.getArgOperand(i), InstID, Vals, VE);  // varargs
1418     }
1419     break;
1420   }
1421   case Instruction::VAArg:
1422     Code = bitc::FUNC_CODE_INST_VAARG;
1423     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));   // valistty
1424     pushValue(I.getOperand(0), InstID, Vals, VE); // valist.
1425     Vals.push_back(VE.getTypeID(I.getType())); // restype.
1426     break;
1427   }
1428
1429   Stream.EmitRecord(Code, Vals, AbbrevToUse);
1430   Vals.clear();
1431 }
1432
1433 // Emit names for globals/functions etc.
1434 static void WriteValueSymbolTable(const ValueSymbolTable &VST,
1435                                   const ValueEnumerator &VE,
1436                                   BitstreamWriter &Stream) {
1437   if (VST.empty()) return;
1438   Stream.EnterSubblock(bitc::VALUE_SYMTAB_BLOCK_ID, 4);
1439
1440   // FIXME: Set up the abbrev, we know how many values there are!
1441   // FIXME: We know if the type names can use 7-bit ascii.
1442   SmallVector<unsigned, 64> NameVals;
1443
1444   for (ValueSymbolTable::const_iterator SI = VST.begin(), SE = VST.end();
1445        SI != SE; ++SI) {
1446
1447     const ValueName &Name = *SI;
1448
1449     // Figure out the encoding to use for the name.
1450     bool is7Bit = true;
1451     bool isChar6 = true;
1452     for (const char *C = Name.getKeyData(), *E = C+Name.getKeyLength();
1453          C != E; ++C) {
1454       if (isChar6)
1455         isChar6 = BitCodeAbbrevOp::isChar6(*C);
1456       if ((unsigned char)*C & 128) {
1457         is7Bit = false;
1458         break;  // don't bother scanning the rest.
1459       }
1460     }
1461
1462     unsigned AbbrevToUse = VST_ENTRY_8_ABBREV;
1463
1464     // VST_ENTRY:   [valueid, namechar x N]
1465     // VST_BBENTRY: [bbid, namechar x N]
1466     unsigned Code;
1467     if (isa<BasicBlock>(SI->getValue())) {
1468       Code = bitc::VST_CODE_BBENTRY;
1469       if (isChar6)
1470         AbbrevToUse = VST_BBENTRY_6_ABBREV;
1471     } else {
1472       Code = bitc::VST_CODE_ENTRY;
1473       if (isChar6)
1474         AbbrevToUse = VST_ENTRY_6_ABBREV;
1475       else if (is7Bit)
1476         AbbrevToUse = VST_ENTRY_7_ABBREV;
1477     }
1478
1479     NameVals.push_back(VE.getValueID(SI->getValue()));
1480     for (const char *P = Name.getKeyData(),
1481          *E = Name.getKeyData()+Name.getKeyLength(); P != E; ++P)
1482       NameVals.push_back((unsigned char)*P);
1483
1484     // Emit the finished record.
1485     Stream.EmitRecord(Code, NameVals, AbbrevToUse);
1486     NameVals.clear();
1487   }
1488   Stream.ExitBlock();
1489 }
1490
1491 /// WriteFunction - Emit a function body to the module stream.
1492 static void WriteFunction(const Function &F, ValueEnumerator &VE,
1493                           BitstreamWriter &Stream) {
1494   Stream.EnterSubblock(bitc::FUNCTION_BLOCK_ID, 4);
1495   VE.incorporateFunction(F);
1496
1497   SmallVector<unsigned, 64> Vals;
1498
1499   // Emit the number of basic blocks, so the reader can create them ahead of
1500   // time.
1501   Vals.push_back(VE.getBasicBlocks().size());
1502   Stream.EmitRecord(bitc::FUNC_CODE_DECLAREBLOCKS, Vals);
1503   Vals.clear();
1504
1505   // If there are function-local constants, emit them now.
1506   unsigned CstStart, CstEnd;
1507   VE.getFunctionConstantRange(CstStart, CstEnd);
1508   WriteConstants(CstStart, CstEnd, VE, Stream, false);
1509
1510   // If there is function-local metadata, emit it now.
1511   WriteFunctionLocalMetadata(F, VE, Stream);
1512
1513   // Keep a running idea of what the instruction ID is.
1514   unsigned InstID = CstEnd;
1515
1516   bool NeedsMetadataAttachment = false;
1517
1518   DebugLoc LastDL;
1519
1520   // Finally, emit all the instructions, in order.
1521   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
1522     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
1523          I != E; ++I) {
1524       WriteInstruction(*I, InstID, VE, Stream, Vals);
1525
1526       if (!I->getType()->isVoidTy())
1527         ++InstID;
1528
1529       // If the instruction has metadata, write a metadata attachment later.
1530       NeedsMetadataAttachment |= I->hasMetadataOtherThanDebugLoc();
1531
1532       // If the instruction has a debug location, emit it.
1533       DebugLoc DL = I->getDebugLoc();
1534       if (DL.isUnknown()) {
1535         // nothing todo.
1536       } else if (DL == LastDL) {
1537         // Just repeat the same debug loc as last time.
1538         Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC_AGAIN, Vals);
1539       } else {
1540         MDNode *Scope, *IA;
1541         DL.getScopeAndInlinedAt(Scope, IA, I->getContext());
1542
1543         Vals.push_back(DL.getLine());
1544         Vals.push_back(DL.getCol());
1545         Vals.push_back(Scope ? VE.getValueID(Scope)+1 : 0);
1546         Vals.push_back(IA ? VE.getValueID(IA)+1 : 0);
1547         Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC, Vals);
1548         Vals.clear();
1549
1550         LastDL = DL;
1551       }
1552     }
1553
1554   // Emit names for all the instructions etc.
1555   WriteValueSymbolTable(F.getValueSymbolTable(), VE, Stream);
1556
1557   if (NeedsMetadataAttachment)
1558     WriteMetadataAttachment(F, VE, Stream);
1559   VE.purgeFunction();
1560   Stream.ExitBlock();
1561 }
1562
1563 // Emit blockinfo, which defines the standard abbreviations etc.
1564 static void WriteBlockInfo(const ValueEnumerator &VE, BitstreamWriter &Stream) {
1565   // We only want to emit block info records for blocks that have multiple
1566   // instances: CONSTANTS_BLOCK, FUNCTION_BLOCK and VALUE_SYMTAB_BLOCK.
1567   // Other blocks can define their abbrevs inline.
1568   Stream.EnterBlockInfoBlock(2);
1569
1570   { // 8-bit fixed-width VST_ENTRY/VST_BBENTRY strings.
1571     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1572     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3));
1573     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1574     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1575     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
1576     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1577                                    Abbv) != VST_ENTRY_8_ABBREV)
1578       llvm_unreachable("Unexpected abbrev ordering!");
1579   }
1580
1581   { // 7-bit fixed width VST_ENTRY strings.
1582     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1583     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
1584     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1585     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1586     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
1587     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1588                                    Abbv) != VST_ENTRY_7_ABBREV)
1589       llvm_unreachable("Unexpected abbrev ordering!");
1590   }
1591   { // 6-bit char6 VST_ENTRY strings.
1592     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1593     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
1594     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1595     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1596     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
1597     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1598                                    Abbv) != VST_ENTRY_6_ABBREV)
1599       llvm_unreachable("Unexpected abbrev ordering!");
1600   }
1601   { // 6-bit char6 VST_BBENTRY strings.
1602     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1603     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_BBENTRY));
1604     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1605     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1606     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
1607     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1608                                    Abbv) != VST_BBENTRY_6_ABBREV)
1609       llvm_unreachable("Unexpected abbrev ordering!");
1610   }
1611
1612
1613
1614   { // SETTYPE abbrev for CONSTANTS_BLOCK.
1615     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1616     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_SETTYPE));
1617     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
1618                               Log2_32_Ceil(VE.getTypes().size()+1)));
1619     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1620                                    Abbv) != CONSTANTS_SETTYPE_ABBREV)
1621       llvm_unreachable("Unexpected abbrev ordering!");
1622   }
1623
1624   { // INTEGER abbrev for CONSTANTS_BLOCK.
1625     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1626     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_INTEGER));
1627     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1628     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1629                                    Abbv) != CONSTANTS_INTEGER_ABBREV)
1630       llvm_unreachable("Unexpected abbrev ordering!");
1631   }
1632
1633   { // CE_CAST abbrev for CONSTANTS_BLOCK.
1634     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1635     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CE_CAST));
1636     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));  // cast opc
1637     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,       // typeid
1638                               Log2_32_Ceil(VE.getTypes().size()+1)));
1639     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));    // value id
1640
1641     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1642                                    Abbv) != CONSTANTS_CE_CAST_Abbrev)
1643       llvm_unreachable("Unexpected abbrev ordering!");
1644   }
1645   { // NULL abbrev for CONSTANTS_BLOCK.
1646     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1647     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_NULL));
1648     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1649                                    Abbv) != CONSTANTS_NULL_Abbrev)
1650       llvm_unreachable("Unexpected abbrev ordering!");
1651   }
1652
1653   // FIXME: This should only use space for first class types!
1654
1655   { // INST_LOAD abbrev for FUNCTION_BLOCK.
1656     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1657     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_LOAD));
1658     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Ptr
1659     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // Align
1660     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // volatile
1661     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1662                                    Abbv) != FUNCTION_INST_LOAD_ABBREV)
1663       llvm_unreachable("Unexpected abbrev ordering!");
1664   }
1665   { // INST_BINOP abbrev for FUNCTION_BLOCK.
1666     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1667     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_BINOP));
1668     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
1669     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // RHS
1670     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
1671     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1672                                    Abbv) != FUNCTION_INST_BINOP_ABBREV)
1673       llvm_unreachable("Unexpected abbrev ordering!");
1674   }
1675   { // INST_BINOP_FLAGS abbrev for FUNCTION_BLOCK.
1676     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1677     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_BINOP));
1678     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
1679     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // RHS
1680     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
1681     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7)); // flags
1682     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1683                                    Abbv) != FUNCTION_INST_BINOP_FLAGS_ABBREV)
1684       llvm_unreachable("Unexpected abbrev ordering!");
1685   }
1686   { // INST_CAST abbrev for FUNCTION_BLOCK.
1687     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1688     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_CAST));
1689     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));    // OpVal
1690     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,       // dest ty
1691                               Log2_32_Ceil(VE.getTypes().size()+1)));
1692     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));  // opc
1693     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1694                                    Abbv) != FUNCTION_INST_CAST_ABBREV)
1695       llvm_unreachable("Unexpected abbrev ordering!");
1696   }
1697
1698   { // INST_RET abbrev for FUNCTION_BLOCK.
1699     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1700     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_RET));
1701     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1702                                    Abbv) != FUNCTION_INST_RET_VOID_ABBREV)
1703       llvm_unreachable("Unexpected abbrev ordering!");
1704   }
1705   { // INST_RET abbrev for FUNCTION_BLOCK.
1706     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1707     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_RET));
1708     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // ValID
1709     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1710                                    Abbv) != FUNCTION_INST_RET_VAL_ABBREV)
1711       llvm_unreachable("Unexpected abbrev ordering!");
1712   }
1713   { // INST_UNREACHABLE abbrev for FUNCTION_BLOCK.
1714     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1715     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_UNREACHABLE));
1716     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1717                                    Abbv) != FUNCTION_INST_UNREACHABLE_ABBREV)
1718       llvm_unreachable("Unexpected abbrev ordering!");
1719   }
1720
1721   Stream.ExitBlock();
1722 }
1723
1724 // Sort the Users based on the order in which the reader parses the bitcode
1725 // file.
1726 static bool bitcodereader_order(const User *lhs, const User *rhs) {
1727   // TODO: Implement.
1728   return true;
1729 }
1730
1731 static void WriteUseList(const Value *V, const ValueEnumerator &VE,
1732                          BitstreamWriter &Stream) {
1733
1734   // One or zero uses can't get out of order.
1735   if (V->use_empty() || V->hasNUses(1))
1736     return;
1737
1738   // Make a copy of the in-memory use-list for sorting.
1739   unsigned UseListSize = std::distance(V->use_begin(), V->use_end());
1740   SmallVector<const User*, 8> UseList;
1741   UseList.reserve(UseListSize);
1742   for (Value::const_use_iterator I = V->use_begin(), E = V->use_end();
1743        I != E; ++I) {
1744     const User *U = *I;
1745     UseList.push_back(U);
1746   }
1747
1748   // Sort the copy based on the order read by the BitcodeReader.
1749   std::sort(UseList.begin(), UseList.end(), bitcodereader_order);
1750
1751   // TODO: Generate a diff between the BitcodeWriter in-memory use-list and the
1752   // sorted list (i.e., the expected BitcodeReader in-memory use-list).
1753
1754   // TODO: Emit the USELIST_CODE_ENTRYs.
1755 }
1756
1757 static void WriteFunctionUseList(const Function *F, ValueEnumerator &VE,
1758                                  BitstreamWriter &Stream) {
1759   VE.incorporateFunction(*F);
1760
1761   for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
1762        AI != AE; ++AI)
1763     WriteUseList(AI, VE, Stream);
1764   for (Function::const_iterator BB = F->begin(), FE = F->end(); BB != FE;
1765        ++BB) {
1766     WriteUseList(BB, VE, Stream);
1767     for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end(); II != IE;
1768          ++II) {
1769       WriteUseList(II, VE, Stream);
1770       for (User::const_op_iterator OI = II->op_begin(), E = II->op_end();
1771            OI != E; ++OI) {
1772         if ((isa<Constant>(*OI) && !isa<GlobalValue>(*OI)) ||
1773             isa<InlineAsm>(*OI))
1774           WriteUseList(*OI, VE, Stream);
1775       }
1776     }
1777   }
1778   VE.purgeFunction();
1779 }
1780
1781 // Emit use-lists.
1782 static void WriteModuleUseLists(const Module *M, ValueEnumerator &VE,
1783                                 BitstreamWriter &Stream) {
1784   Stream.EnterSubblock(bitc::USELIST_BLOCK_ID, 3);
1785
1786   // XXX: this modifies the module, but in a way that should never change the
1787   // behavior of any pass or codegen in LLVM. The problem is that GVs may
1788   // contain entries in the use_list that do not exist in the Module and are
1789   // not stored in the .bc file.
1790   for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
1791        I != E; ++I)
1792     I->removeDeadConstantUsers();
1793
1794   // Write the global variables.
1795   for (Module::const_global_iterator GI = M->global_begin(),
1796          GE = M->global_end(); GI != GE; ++GI) {
1797     WriteUseList(GI, VE, Stream);
1798
1799     // Write the global variable initializers.
1800     if (GI->hasInitializer())
1801       WriteUseList(GI->getInitializer(), VE, Stream);
1802   }
1803
1804   // Write the functions.
1805   for (Module::const_iterator FI = M->begin(), FE = M->end(); FI != FE; ++FI) {
1806     WriteUseList(FI, VE, Stream);
1807     if (!FI->isDeclaration())
1808       WriteFunctionUseList(FI, VE, Stream);
1809   }
1810
1811   // Write the aliases.
1812   for (Module::const_alias_iterator AI = M->alias_begin(), AE = M->alias_end();
1813        AI != AE; ++AI) {
1814     WriteUseList(AI, VE, Stream);
1815     WriteUseList(AI->getAliasee(), VE, Stream);
1816   }
1817
1818   Stream.ExitBlock();
1819 }
1820
1821 /// WriteModule - Emit the specified module to the bitstream.
1822 static void WriteModule(const Module *M, BitstreamWriter &Stream) {
1823   Stream.EnterSubblock(bitc::MODULE_BLOCK_ID, 3);
1824
1825   SmallVector<unsigned, 1> Vals;
1826   unsigned CurVersion = 1;
1827   Vals.push_back(CurVersion);
1828   Stream.EmitRecord(bitc::MODULE_CODE_VERSION, Vals);
1829
1830   // Analyze the module, enumerating globals, functions, etc.
1831   ValueEnumerator VE(M);
1832
1833   // Emit blockinfo, which defines the standard abbreviations etc.
1834   WriteBlockInfo(VE, Stream);
1835
1836   // Emit information about parameter attributes.
1837   WriteAttributeTable(VE, Stream);
1838
1839   // Emit information describing all of the types in the module.
1840   WriteTypeTable(VE, Stream);
1841
1842   // Emit top-level description of module, including target triple, inline asm,
1843   // descriptors for global variables, and function prototype info.
1844   WriteModuleInfo(M, VE, Stream);
1845
1846   // Emit constants.
1847   WriteModuleConstants(VE, Stream);
1848
1849   // Emit metadata.
1850   WriteModuleMetadata(M, VE, Stream);
1851
1852   // Emit metadata.
1853   WriteModuleMetadataStore(M, Stream);
1854
1855   // Emit names for globals/functions etc.
1856   WriteValueSymbolTable(M->getValueSymbolTable(), VE, Stream);
1857
1858   // Emit use-lists.
1859   if (EnablePreserveUseListOrdering)
1860     WriteModuleUseLists(M, VE, Stream);
1861
1862   // Emit function bodies.
1863   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F)
1864     if (!F->isDeclaration())
1865       WriteFunction(*F, VE, Stream);
1866
1867   Stream.ExitBlock();
1868 }
1869
1870 /// EmitDarwinBCHeader - If generating a bc file on darwin, we have to emit a
1871 /// header and trailer to make it compatible with the system archiver.  To do
1872 /// this we emit the following header, and then emit a trailer that pads the
1873 /// file out to be a multiple of 16 bytes.
1874 ///
1875 /// struct bc_header {
1876 ///   uint32_t Magic;         // 0x0B17C0DE
1877 ///   uint32_t Version;       // Version, currently always 0.
1878 ///   uint32_t BitcodeOffset; // Offset to traditional bitcode file.
1879 ///   uint32_t BitcodeSize;   // Size of traditional bitcode file.
1880 ///   uint32_t CPUType;       // CPU specifier.
1881 ///   ... potentially more later ...
1882 /// };
1883 enum {
1884   DarwinBCSizeFieldOffset = 3*4, // Offset to bitcode_size.
1885   DarwinBCHeaderSize = 5*4
1886 };
1887
1888 static void WriteInt32ToBuffer(uint32_t Value, SmallVectorImpl<char> &Buffer,
1889                                uint32_t &Position) {
1890   Buffer[Position + 0] = (unsigned char) (Value >>  0);
1891   Buffer[Position + 1] = (unsigned char) (Value >>  8);
1892   Buffer[Position + 2] = (unsigned char) (Value >> 16);
1893   Buffer[Position + 3] = (unsigned char) (Value >> 24);
1894   Position += 4;
1895 }
1896
1897 static void EmitDarwinBCHeaderAndTrailer(SmallVectorImpl<char> &Buffer,
1898                                          const Triple &TT) {
1899   unsigned CPUType = ~0U;
1900
1901   // Match x86_64-*, i[3-9]86-*, powerpc-*, powerpc64-*, arm-*, thumb-*,
1902   // armv[0-9]-*, thumbv[0-9]-*, armv5te-*, or armv6t2-*. The CPUType is a magic
1903   // number from /usr/include/mach/machine.h.  It is ok to reproduce the
1904   // specific constants here because they are implicitly part of the Darwin ABI.
1905   enum {
1906     DARWIN_CPU_ARCH_ABI64      = 0x01000000,
1907     DARWIN_CPU_TYPE_X86        = 7,
1908     DARWIN_CPU_TYPE_ARM        = 12,
1909     DARWIN_CPU_TYPE_POWERPC    = 18
1910   };
1911
1912   Triple::ArchType Arch = TT.getArch();
1913   if (Arch == Triple::x86_64)
1914     CPUType = DARWIN_CPU_TYPE_X86 | DARWIN_CPU_ARCH_ABI64;
1915   else if (Arch == Triple::x86)
1916     CPUType = DARWIN_CPU_TYPE_X86;
1917   else if (Arch == Triple::ppc)
1918     CPUType = DARWIN_CPU_TYPE_POWERPC;
1919   else if (Arch == Triple::ppc64)
1920     CPUType = DARWIN_CPU_TYPE_POWERPC | DARWIN_CPU_ARCH_ABI64;
1921   else if (Arch == Triple::arm || Arch == Triple::thumb)
1922     CPUType = DARWIN_CPU_TYPE_ARM;
1923
1924   // Traditional Bitcode starts after header.
1925   assert(Buffer.size() >= DarwinBCHeaderSize &&
1926          "Expected header size to be reserved");
1927   unsigned BCOffset = DarwinBCHeaderSize;
1928   unsigned BCSize = Buffer.size()-DarwinBCHeaderSize;
1929
1930   // Write the magic and version.
1931   unsigned Position = 0;
1932   WriteInt32ToBuffer(0x0B17C0DE , Buffer, Position);
1933   WriteInt32ToBuffer(0          , Buffer, Position); // Version.
1934   WriteInt32ToBuffer(BCOffset   , Buffer, Position);
1935   WriteInt32ToBuffer(BCSize     , Buffer, Position);
1936   WriteInt32ToBuffer(CPUType    , Buffer, Position);
1937
1938   // If the file is not a multiple of 16 bytes, insert dummy padding.
1939   while (Buffer.size() & 15)
1940     Buffer.push_back(0);
1941 }
1942
1943 /// WriteBitcodeToFile - Write the specified module to the specified output
1944 /// stream.
1945 void llvm::WriteBitcodeToFile(const Module *M, raw_ostream &Out) {
1946   SmallVector<char, 1024> Buffer;
1947   Buffer.reserve(256*1024);
1948
1949   // If this is darwin or another generic macho target, reserve space for the
1950   // header.
1951   Triple TT(M->getTargetTriple());
1952   if (TT.isOSDarwin())
1953     Buffer.insert(Buffer.begin(), DarwinBCHeaderSize, 0);
1954
1955   // Emit the module into the buffer.
1956   {
1957     BitstreamWriter Stream(Buffer);
1958
1959     // Emit the file header.
1960     Stream.Emit((unsigned)'B', 8);
1961     Stream.Emit((unsigned)'C', 8);
1962     Stream.Emit(0x0, 4);
1963     Stream.Emit(0xC, 4);
1964     Stream.Emit(0xE, 4);
1965     Stream.Emit(0xD, 4);
1966
1967     // Emit the module.
1968     WriteModule(M, Stream);
1969   }
1970
1971   if (TT.isOSDarwin())
1972     EmitDarwinBCHeaderAndTrailer(Buffer, TT);
1973
1974   // Write the generated bitstream to "Out".
1975   Out.write((char*)&Buffer.front(), Buffer.size());
1976 }