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 "ValueEnumerator.h"
  16 #include "llvm/ADT/Triple.h"
  17 #include "llvm/Bitcode/BitstreamWriter.h"
  18 #include "llvm/Bitcode/LLVMBitCodes.h"
  19 #include "llvm/IR/Constants.h"
  20 #include "llvm/IR/DerivedTypes.h"
  21 #include "llvm/IR/InlineAsm.h"
  22 #include "llvm/IR/Instructions.h"
  23 #include "llvm/IR/Module.h"
  24 #include "llvm/IR/Operator.h"
  25 #include "llvm/IR/ValueSymbolTable.h"
  26 #include "llvm/Support/CommandLine.h"
  27 #include "llvm/Support/ErrorHandling.h"
  28 #include "llvm/Support/MathExtras.h"
  29 #include "llvm/Support/Program.h"
  30 #include "llvm/Support/raw_ostream.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
  66 static unsigned GetEncodedCastOpcode(unsigned Opcode) {
  67   switch (Opcode) {
  68   default: llvm_unreachable("Unknown cast instruction!");
  69   case Instruction::Trunc   : return bitc::CAST_TRUNC;
  70   case Instruction::ZExt    : return bitc::CAST_ZEXT;
  71   case Instruction::SExt    : return bitc::CAST_SEXT;
  72   case Instruction::FPToUI  : return bitc::CAST_FPTOUI;
  73   case Instruction::FPToSI  : return bitc::CAST_FPTOSI;
  74   case Instruction::UIToFP  : return bitc::CAST_UITOFP;
  75   case Instruction::SIToFP  : return bitc::CAST_SITOFP;
  76   case Instruction::FPTrunc : return bitc::CAST_FPTRUNC;
  77   case Instruction::FPExt   : return bitc::CAST_FPEXT;
  78   case Instruction::PtrToInt: return bitc::CAST_PTRTOINT;
  79   case Instruction::IntToPtr: return bitc::CAST_INTTOPTR;
  80   case Instruction::BitCast : return bitc::CAST_BITCAST;
  81   case Instruction::AddrSpaceCast: return bitc::CAST_ADDRSPACECAST;
  82   }
  83 }
  84
  85 static unsigned GetEncodedBinaryOpcode(unsigned Opcode) {
  86   switch (Opcode) {
  87   default: llvm_unreachable("Unknown binary instruction!");
  88   case Instruction::Add:
  89   case Instruction::FAdd: return bitc::BINOP_ADD;
  90   case Instruction::Sub:
  91   case Instruction::FSub: return bitc::BINOP_SUB;
  92   case Instruction::Mul:
  93   case Instruction::FMul: return bitc::BINOP_MUL;
  94   case Instruction::UDiv: return bitc::BINOP_UDIV;
  95   case Instruction::FDiv:
  96   case Instruction::SDiv: return bitc::BINOP_SDIV;
  97   case Instruction::URem: return bitc::BINOP_UREM;
  98   case Instruction::FRem:
  99   case Instruction::SRem: return bitc::BINOP_SREM;
 100   case Instruction::Shl:  return bitc::BINOP_SHL;
 101   case Instruction::LShr: return bitc::BINOP_LSHR;
 102   case Instruction::AShr: return bitc::BINOP_ASHR;
 103   case Instruction::And:  return bitc::BINOP_AND;
 104   case Instruction::Or:   return bitc::BINOP_OR;
 105   case Instruction::Xor:  return bitc::BINOP_XOR;
 106   }
 107 }
 108
 109 static unsigned GetEncodedRMWOperation(AtomicRMWInst::BinOp Op) {
 110   switch (Op) {
 111   default: llvm_unreachable("Unknown RMW operation!");
 112   case AtomicRMWInst::Xchg: return bitc::RMW_XCHG;
 113   case AtomicRMWInst::Add: return bitc::RMW_ADD;
 114   case AtomicRMWInst::Sub: return bitc::RMW_SUB;
 115   case AtomicRMWInst::And: return bitc::RMW_AND;
 116   case AtomicRMWInst::Nand: return bitc::RMW_NAND;
 117   case AtomicRMWInst::Or: return bitc::RMW_OR;
 118   case AtomicRMWInst::Xor: return bitc::RMW_XOR;
 119   case AtomicRMWInst::Max: return bitc::RMW_MAX;
 120   case AtomicRMWInst::Min: return bitc::RMW_MIN;
 121   case AtomicRMWInst::UMax: return bitc::RMW_UMAX;
 122   case AtomicRMWInst::UMin: return bitc::RMW_UMIN;
 123   }
 124 }
 125
 126 static unsigned GetEncodedOrdering(AtomicOrdering Ordering) {
 127   switch (Ordering) {
 128   case NotAtomic: return bitc::ORDERING_NOTATOMIC;
 129   case Unordered: return bitc::ORDERING_UNORDERED;
 130   case Monotonic: return bitc::ORDERING_MONOTONIC;
 131   case Acquire: return bitc::ORDERING_ACQUIRE;
 132   case Release: return bitc::ORDERING_RELEASE;
 133   case AcquireRelease: return bitc::ORDERING_ACQREL;
 134   case SequentiallyConsistent: return bitc::ORDERING_SEQCST;
 135   }
 136   llvm_unreachable("Invalid ordering");
 137 }
 138
 139 static unsigned GetEncodedSynchScope(SynchronizationScope SynchScope) {
 140   switch (SynchScope) {
 141   case SingleThread: return bitc::SYNCHSCOPE_SINGLETHREAD;
 142   case CrossThread: return bitc::SYNCHSCOPE_CROSSTHREAD;
 143   }
 144   llvm_unreachable("Invalid synch scope");
 145 }
 146
 147 static void WriteStringRecord(unsigned Code, StringRef Str,
 148                               unsigned AbbrevToUse, BitstreamWriter &Stream) {
 149   SmallVector<unsigned, 64> Vals;
 150
 151   // Code: [strchar x N]
 152   for (unsigned i = 0, e = Str.size(); i != e; ++i) {
 153     if (AbbrevToUse && !BitCodeAbbrevOp::isChar6(Str[i]))
 154       AbbrevToUse = 0;
 155     Vals.push_back(Str[i]);
 156   }
 157
 158   // Emit the finished record.
 159   Stream.EmitRecord(Code, Vals, AbbrevToUse);
 160 }
 161
 162 static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
 163   switch (Kind) {
 164   case Attribute::Alignment:
 165     return bitc::ATTR_KIND_ALIGNMENT;
 166   case Attribute::AlwaysInline:
 167     return bitc::ATTR_KIND_ALWAYS_INLINE;
 168   case Attribute::Builtin:
 169     return bitc::ATTR_KIND_BUILTIN;
 170   case Attribute::ByVal:
 171     return bitc::ATTR_KIND_BY_VAL;
 172   case Attribute::InAlloca:
 173     return bitc::ATTR_KIND_IN_ALLOCA;
 174   case Attribute::Cold:
 175     return bitc::ATTR_KIND_COLD;
 176   case Attribute::InlineHint:
 177     return bitc::ATTR_KIND_INLINE_HINT;
 178   case Attribute::InReg:
 179     return bitc::ATTR_KIND_IN_REG;
 180   case Attribute::MinSize:
 181     return bitc::ATTR_KIND_MIN_SIZE;
 182   case Attribute::Naked:
 183     return bitc::ATTR_KIND_NAKED;
 184   case Attribute::Nest:
 185     return bitc::ATTR_KIND_NEST;
 186   case Attribute::NoAlias:
 187     return bitc::ATTR_KIND_NO_ALIAS;
 188   case Attribute::NoBuiltin:
 189     return bitc::ATTR_KIND_NO_BUILTIN;
 190   case Attribute::NoCapture:
 191     return bitc::ATTR_KIND_NO_CAPTURE;
 192   case Attribute::NoDuplicate:
 193     return bitc::ATTR_KIND_NO_DUPLICATE;
 194   case Attribute::NoImplicitFloat:
 195     return bitc::ATTR_KIND_NO_IMPLICIT_FLOAT;
 196   case Attribute::NoInline:
 197     return bitc::ATTR_KIND_NO_INLINE;
 198   case Attribute::NonLazyBind:
 199     return bitc::ATTR_KIND_NON_LAZY_BIND;
 200   case Attribute::NoRedZone:
 201     return bitc::ATTR_KIND_NO_RED_ZONE;
 202   case Attribute::NoReturn:
 203     return bitc::ATTR_KIND_NO_RETURN;
 204   case Attribute::NoUnwind:
 205     return bitc::ATTR_KIND_NO_UNWIND;
 206   case Attribute::OptimizeForSize:
 207     return bitc::ATTR_KIND_OPTIMIZE_FOR_SIZE;
 208   case Attribute::OptimizeNone:
 209     return bitc::ATTR_KIND_OPTIMIZE_NONE;
 210   case Attribute::ReadNone:
 211     return bitc::ATTR_KIND_READ_NONE;
 212   case Attribute::ReadOnly:
 213     return bitc::ATTR_KIND_READ_ONLY;
 214   case Attribute::Returned:
 215     return bitc::ATTR_KIND_RETURNED;
 216   case Attribute::ReturnsTwice:
 217     return bitc::ATTR_KIND_RETURNS_TWICE;
 218   case Attribute::SExt:
 219     return bitc::ATTR_KIND_S_EXT;
 220   case Attribute::StackAlignment:
 221     return bitc::ATTR_KIND_STACK_ALIGNMENT;
 222   case Attribute::StackProtect:
 223     return bitc::ATTR_KIND_STACK_PROTECT;
 224   case Attribute::StackProtectReq:
 225     return bitc::ATTR_KIND_STACK_PROTECT_REQ;
 226   case Attribute::StackProtectStrong:
 227     return bitc::ATTR_KIND_STACK_PROTECT_STRONG;
 228   case Attribute::StructRet:
 229     return bitc::ATTR_KIND_STRUCT_RET;
 230   case Attribute::SanitizeAddress:
 231     return bitc::ATTR_KIND_SANITIZE_ADDRESS;
 232   case Attribute::SanitizeThread:
 233     return bitc::ATTR_KIND_SANITIZE_THREAD;
 234   case Attribute::SanitizeMemory:
 235     return bitc::ATTR_KIND_SANITIZE_MEMORY;
 236   case Attribute::UWTable:
 237     return bitc::ATTR_KIND_UW_TABLE;
 238   case Attribute::ZExt:
 239     return bitc::ATTR_KIND_Z_EXT;
 240   case Attribute::EndAttrKinds:
 241     llvm_unreachable("Can not encode end-attribute kinds marker.");
 242   case Attribute::None:
 243     llvm_unreachable("Can not encode none-attribute.");
 244   }
 245
 246   llvm_unreachable("Trying to encode unknown attribute");
 247 }
 248
 249 static void WriteAttributeGroupTable(const ValueEnumerator &VE,
 250                                      BitstreamWriter &Stream) {
 251   const std::vector<AttributeSet> &AttrGrps = VE.getAttributeGroups();
 252   if (AttrGrps.empty()) return;
 253
 254   Stream.EnterSubblock(bitc::PARAMATTR_GROUP_BLOCK_ID, 3);
 255
 256   SmallVector<uint64_t, 64> Record;
 257   for (unsigned i = 0, e = AttrGrps.size(); i != e; ++i) {
 258     AttributeSet AS = AttrGrps[i];
 259     for (unsigned i = 0, e = AS.getNumSlots(); i != e; ++i) {
 260       AttributeSet A = AS.getSlotAttributes(i);
 261
 262       Record.push_back(VE.getAttributeGroupID(A));
 263       Record.push_back(AS.getSlotIndex(i));
 264
 265       for (AttributeSet::iterator I = AS.begin(0), E = AS.end(0);
 266            I != E; ++I) {
 267         Attribute Attr = *I;
 268         if (Attr.isEnumAttribute()) {
 269           Record.push_back(0);
 270           Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
 271         } else if (Attr.isAlignAttribute()) {
 272           Record.push_back(1);
 273           Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
 274           Record.push_back(Attr.getValueAsInt());
 275         } else {
 276           StringRef Kind = Attr.getKindAsString();
 277           StringRef Val = Attr.getValueAsString();
 278
 279           Record.push_back(Val.empty() ? 3 : 4);
 280           Record.append(Kind.begin(), Kind.end());
 281           Record.push_back(0);
 282           if (!Val.empty()) {
 283             Record.append(Val.begin(), Val.end());
 284             Record.push_back(0);
 285           }
 286         }
 287       }
 288
 289       Stream.EmitRecord(bitc::PARAMATTR_GRP_CODE_ENTRY, Record);
 290       Record.clear();
 291     }
 292   }
 293
 294   Stream.ExitBlock();
 295 }
 296
 297 static void WriteAttributeTable(const ValueEnumerator &VE,
 298                                 BitstreamWriter &Stream) {
 299   const std::vector<AttributeSet> &Attrs = VE.getAttributes();
 300   if (Attrs.empty()) return;
 301
 302   Stream.EnterSubblock(bitc::PARAMATTR_BLOCK_ID, 3);
 303
 304   SmallVector<uint64_t, 64> Record;
 305   for (unsigned i = 0, e = Attrs.size(); i != e; ++i) {
 306     const AttributeSet &A = Attrs[i];
 307     for (unsigned i = 0, e = A.getNumSlots(); i != e; ++i)
 308       Record.push_back(VE.getAttributeGroupID(A.getSlotAttributes(i)));
 309
 310     Stream.EmitRecord(bitc::PARAMATTR_CODE_ENTRY, Record);
 311     Record.clear();
 312   }
 313
 314   Stream.ExitBlock();
 315 }
 316
 317 /// WriteTypeTable - Write out the type table for a module.
 318 static void WriteTypeTable(const ValueEnumerator &VE, BitstreamWriter &Stream) {
 319   const ValueEnumerator::TypeList &TypeList = VE.getTypes();
 320
 321   Stream.EnterSubblock(bitc::TYPE_BLOCK_ID_NEW, 4 /*count from # abbrevs */);
 322   SmallVector<uint64_t, 64> TypeVals;
 323
 324   uint64_t NumBits = Log2_32_Ceil(VE.getTypes().size()+1);
 325
 326   // Abbrev for TYPE_CODE_POINTER.
 327   BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 328   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_POINTER));
 329   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
 330   Abbv->Add(BitCodeAbbrevOp(0));  // Addrspace = 0
 331   unsigned PtrAbbrev = Stream.EmitAbbrev(Abbv);
 332
 333   // Abbrev for TYPE_CODE_FUNCTION.
 334   Abbv = new BitCodeAbbrev();
 335   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_FUNCTION));
 336   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // isvararg
 337   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 338   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
 339
 340   unsigned FunctionAbbrev = Stream.EmitAbbrev(Abbv);
 341
 342   // Abbrev for TYPE_CODE_STRUCT_ANON.
 343   Abbv = new BitCodeAbbrev();
 344   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_ANON));
 345   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // ispacked
 346   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 347   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
 348
 349   unsigned StructAnonAbbrev = Stream.EmitAbbrev(Abbv);
 350
 351   // Abbrev for TYPE_CODE_STRUCT_NAME.
 352   Abbv = new BitCodeAbbrev();
 353   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_NAME));
 354   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 355   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
 356   unsigned StructNameAbbrev = Stream.EmitAbbrev(Abbv);
 357
 358   // Abbrev for TYPE_CODE_STRUCT_NAMED.
 359   Abbv = new BitCodeAbbrev();
 360   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_NAMED));
 361   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // ispacked
 362   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 363   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
 364
 365   unsigned StructNamedAbbrev = Stream.EmitAbbrev(Abbv);
 366
 367   // Abbrev for TYPE_CODE_ARRAY.
 368   Abbv = new BitCodeAbbrev();
 369   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_ARRAY));
 370   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));   // size
 371   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
 372
 373   unsigned ArrayAbbrev = Stream.EmitAbbrev(Abbv);
 374
 375   // Emit an entry count so the reader can reserve space.
 376   TypeVals.push_back(TypeList.size());
 377   Stream.EmitRecord(bitc::TYPE_CODE_NUMENTRY, TypeVals);
 378   TypeVals.clear();
 379
 380   // Loop over all of the types, emitting each in turn.
 381   for (unsigned i = 0, e = TypeList.size(); i != e; ++i) {
 382     Type *T = TypeList[i];
 383     int AbbrevToUse = 0;
 384     unsigned Code = 0;
 385
 386     switch (T->getTypeID()) {
 387     case Type::VoidTyID:      Code = bitc::TYPE_CODE_VOID;      break;
 388     case Type::HalfTyID:      Code = bitc::TYPE_CODE_HALF;      break;
 389     case Type::FloatTyID:     Code = bitc::TYPE_CODE_FLOAT;     break;
 390     case Type::DoubleTyID:    Code = bitc::TYPE_CODE_DOUBLE;    break;
 391     case Type::X86_FP80TyID:  Code = bitc::TYPE_CODE_X86_FP80;  break;
 392     case Type::FP128TyID:     Code = bitc::TYPE_CODE_FP128;     break;
 393     case Type::PPC_FP128TyID: Code = bitc::TYPE_CODE_PPC_FP128; break;
 394     case Type::LabelTyID:     Code = bitc::TYPE_CODE_LABEL;     break;
 395     case Type::MetadataTyID:  Code = bitc::TYPE_CODE_METADATA;  break;
 396     case Type::X86_MMXTyID:   Code = bitc::TYPE_CODE_X86_MMX;   break;
 397     case Type::IntegerTyID:
 398       // INTEGER: [width]
 399       Code = bitc::TYPE_CODE_INTEGER;
 400       TypeVals.push_back(cast<IntegerType>(T)->getBitWidth());
 401       break;
 402     case Type::PointerTyID: {
 403       PointerType *PTy = cast<PointerType>(T);
 404       // POINTER: [pointee type, address space]
 405       Code = bitc::TYPE_CODE_POINTER;
 406       TypeVals.push_back(VE.getTypeID(PTy->getElementType()));
 407       unsigned AddressSpace = PTy->getAddressSpace();
 408       TypeVals.push_back(AddressSpace);
 409       if (AddressSpace == 0) AbbrevToUse = PtrAbbrev;
 410       break;
 411     }
 412     case Type::FunctionTyID: {
 413       FunctionType *FT = cast<FunctionType>(T);
 414       // FUNCTION: [isvararg, retty, paramty x N]
 415       Code = bitc::TYPE_CODE_FUNCTION;
 416       TypeVals.push_back(FT->isVarArg());
 417       TypeVals.push_back(VE.getTypeID(FT->getReturnType()));
 418       for (unsigned i = 0, e = FT->getNumParams(); i != e; ++i)
 419         TypeVals.push_back(VE.getTypeID(FT->getParamType(i)));
 420       AbbrevToUse = FunctionAbbrev;
 421       break;
 422     }
 423     case Type::StructTyID: {
 424       StructType *ST = cast<StructType>(T);
 425       // STRUCT: [ispacked, eltty x N]
 426       TypeVals.push_back(ST->isPacked());
 427       // Output all of the element types.
 428       for (StructType::element_iterator I = ST->element_begin(),
 429            E = ST->element_end(); I != E; ++I)
 430         TypeVals.push_back(VE.getTypeID(*I));
 431
 432       if (ST->isLiteral()) {
 433         Code = bitc::TYPE_CODE_STRUCT_ANON;
 434         AbbrevToUse = StructAnonAbbrev;
 435       } else {
 436         if (ST->isOpaque()) {
 437           Code = bitc::TYPE_CODE_OPAQUE;
 438         } else {
 439           Code = bitc::TYPE_CODE_STRUCT_NAMED;
 440           AbbrevToUse = StructNamedAbbrev;
 441         }
 442
 443         // Emit the name if it is present.
 444         if (!ST->getName().empty())
 445           WriteStringRecord(bitc::TYPE_CODE_STRUCT_NAME, ST->getName(),
 446                             StructNameAbbrev, Stream);
 447       }
 448       break;
 449     }
 450     case Type::ArrayTyID: {
 451       ArrayType *AT = cast<ArrayType>(T);
 452       // ARRAY: [numelts, eltty]
 453       Code = bitc::TYPE_CODE_ARRAY;
 454       TypeVals.push_back(AT->getNumElements());
 455       TypeVals.push_back(VE.getTypeID(AT->getElementType()));
 456       AbbrevToUse = ArrayAbbrev;
 457       break;
 458     }
 459     case Type::VectorTyID: {
 460       VectorType *VT = cast<VectorType>(T);
 461       // VECTOR [numelts, eltty]
 462       Code = bitc::TYPE_CODE_VECTOR;
 463       TypeVals.push_back(VT->getNumElements());
 464       TypeVals.push_back(VE.getTypeID(VT->getElementType()));
 465       break;
 466     }
 467     }
 468
 469     // Emit the finished record.
 470     Stream.EmitRecord(Code, TypeVals, AbbrevToUse);
 471     TypeVals.clear();
 472   }
 473
 474   Stream.ExitBlock();
 475 }
 476
 477 static unsigned getEncodedLinkage(const GlobalValue *GV) {
 478   switch (GV->getLinkage()) {
 479   case GlobalValue::ExternalLinkage:                 return 0;
 480   case GlobalValue::WeakAnyLinkage:                  return 1;
 481   case GlobalValue::AppendingLinkage:                return 2;
 482   case GlobalValue::InternalLinkage:                 return 3;
 483   case GlobalValue::LinkOnceAnyLinkage:              return 4;
 484   case GlobalValue::DLLImportLinkage:                return 5;
 485   case GlobalValue::DLLExportLinkage:                return 6;
 486   case GlobalValue::ExternalWeakLinkage:             return 7;
 487   case GlobalValue::CommonLinkage:                   return 8;
 488   case GlobalValue::PrivateLinkage:                  return 9;
 489   case GlobalValue::WeakODRLinkage:                  return 10;
 490   case GlobalValue::LinkOnceODRLinkage:              return 11;
 491   case GlobalValue::AvailableExternallyLinkage:      return 12;
 492   case GlobalValue::LinkerPrivateLinkage:            return 13;
 493   case GlobalValue::LinkerPrivateWeakLinkage:        return 14;
 494   }
 495   llvm_unreachable("Invalid linkage");
 496 }
 497
 498 static unsigned getEncodedVisibility(const GlobalValue *GV) {
 499   switch (GV->getVisibility()) {
 500   case GlobalValue::DefaultVisibility:   return 0;
 501   case GlobalValue::HiddenVisibility:    return 1;
 502   case GlobalValue::ProtectedVisibility: return 2;
 503   }
 504   llvm_unreachable("Invalid visibility");
 505 }
 506
 507 static unsigned getEncodedThreadLocalMode(const GlobalVariable *GV) {
 508   switch (GV->getThreadLocalMode()) {
 509     case GlobalVariable::NotThreadLocal:         return 0;
 510     case GlobalVariable::GeneralDynamicTLSModel: return 1;
 511     case GlobalVariable::LocalDynamicTLSModel:   return 2;
 512     case GlobalVariable::InitialExecTLSModel:    return 3;
 513     case GlobalVariable::LocalExecTLSModel:      return 4;
 514   }
 515   llvm_unreachable("Invalid TLS model");
 516 }
 517
 518 // Emit top-level description of module, including target triple, inline asm,
 519 // descriptors for global variables, and function prototype info.
 520 static void WriteModuleInfo(const Module *M, const ValueEnumerator &VE,
 521                             BitstreamWriter &Stream) {
 522   // Emit various pieces of data attached to a module.
 523   if (!M->getTargetTriple().empty())
 524     WriteStringRecord(bitc::MODULE_CODE_TRIPLE, M->getTargetTriple(),
 525                       0/*TODO*/, Stream);
 526   if (!M->getDataLayout().empty())
 527     WriteStringRecord(bitc::MODULE_CODE_DATALAYOUT, M->getDataLayout(),
 528                       0/*TODO*/, Stream);
 529   if (!M->getModuleInlineAsm().empty())
 530     WriteStringRecord(bitc::MODULE_CODE_ASM, M->getModuleInlineAsm(),
 531                       0/*TODO*/, Stream);
 532
 533   // Emit information about sections and GC, computing how many there are. Also
 534   // compute the maximum alignment value.
 535   std::map<std::string, unsigned> SectionMap;
 536   std::map<std::string, unsigned> GCMap;
 537   unsigned MaxAlignment = 0;
 538   unsigned MaxGlobalType = 0;
 539   for (Module::const_global_iterator GV = M->global_begin(),E = M->global_end();
 540        GV != E; ++GV) {
 541     MaxAlignment = std::max(MaxAlignment, GV->getAlignment());
 542     MaxGlobalType = std::max(MaxGlobalType, VE.getTypeID(GV->getType()));
 543     if (GV->hasSection()) {
 544       // Give section names unique ID's.
 545       unsigned &Entry = SectionMap[GV->getSection()];
 546       if (!Entry) {
 547         WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, GV->getSection(),
 548                           0/*TODO*/, Stream);
 549         Entry = SectionMap.size();
 550       }
 551     }
 552   }
 553   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F) {
 554     MaxAlignment = std::max(MaxAlignment, F->getAlignment());
 555     if (F->hasSection()) {
 556       // Give section names unique ID's.
 557       unsigned &Entry = SectionMap[F->getSection()];
 558       if (!Entry) {
 559         WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, F->getSection(),
 560                           0/*TODO*/, Stream);
 561         Entry = SectionMap.size();
 562       }
 563     }
 564     if (F->hasGC()) {
 565       // Same for GC names.
 566       unsigned &Entry = GCMap[F->getGC()];
 567       if (!Entry) {
 568         WriteStringRecord(bitc::MODULE_CODE_GCNAME, F->getGC(),
 569                           0/*TODO*/, Stream);
 570         Entry = GCMap.size();
 571       }
 572     }
 573   }
 574
 575   // Emit abbrev for globals, now that we know # sections and max alignment.
 576   unsigned SimpleGVarAbbrev = 0;
 577   if (!M->global_empty()) {
 578     // Add an abbrev for common globals with no visibility or thread localness.
 579     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 580     Abbv->Add(BitCodeAbbrevOp(bitc::MODULE_CODE_GLOBALVAR));
 581     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 582                               Log2_32_Ceil(MaxGlobalType+1)));
 583     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));      // Constant.
 584     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));        // Initializer.
 585     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));      // Linkage.
 586     if (MaxAlignment == 0)                                      // Alignment.
 587       Abbv->Add(BitCodeAbbrevOp(0));
 588     else {
 589       unsigned MaxEncAlignment = Log2_32(MaxAlignment)+1;
 590       Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 591                                Log2_32_Ceil(MaxEncAlignment+1)));
 592     }
 593     if (SectionMap.empty())                                    // Section.
 594       Abbv->Add(BitCodeAbbrevOp(0));
 595     else
 596       Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
 597                                Log2_32_Ceil(SectionMap.size()+1)));
 598     // Don't bother emitting vis + thread local.
 599     SimpleGVarAbbrev = Stream.EmitAbbrev(Abbv);
 600   }
 601
 602   // Emit the global variable information.
 603   SmallVector<unsigned, 64> Vals;
 604   for (Module::const_global_iterator GV = M->global_begin(),E = M->global_end();
 605        GV != E; ++GV) {
 606     unsigned AbbrevToUse = 0;
 607
 608     // GLOBALVAR: [type, isconst, initid,
 609     //             linkage, alignment, section, visibility, threadlocal,
 610     //             unnamed_addr, externally_initialized]
 611     Vals.push_back(VE.getTypeID(GV->getType()));
 612     Vals.push_back(GV->isConstant());
 613     Vals.push_back(GV->isDeclaration() ? 0 :
 614                    (VE.getValueID(GV->getInitializer()) + 1));
 615     Vals.push_back(getEncodedLinkage(GV));
 616     Vals.push_back(Log2_32(GV->getAlignment())+1);
 617     Vals.push_back(GV->hasSection() ? SectionMap[GV->getSection()] : 0);
 618     if (GV->isThreadLocal() ||
 619         GV->getVisibility() != GlobalValue::DefaultVisibility ||
 620         GV->hasUnnamedAddr() || GV->isExternallyInitialized()) {
 621       Vals.push_back(getEncodedVisibility(GV));
 622       Vals.push_back(getEncodedThreadLocalMode(GV));
 623       Vals.push_back(GV->hasUnnamedAddr());
 624       Vals.push_back(GV->isExternallyInitialized());
 625     } else {
 626       AbbrevToUse = SimpleGVarAbbrev;
 627     }
 628
 629     Stream.EmitRecord(bitc::MODULE_CODE_GLOBALVAR, Vals, AbbrevToUse);
 630     Vals.clear();
 631   }
 632
 633   // Emit the function proto information.
 634   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F) {
 635     // FUNCTION:  [type, callingconv, isproto, linkage, paramattrs, alignment,
 636     //             section, visibility, gc, unnamed_addr, prefix]
 637     Vals.push_back(VE.getTypeID(F->getType()));
 638     Vals.push_back(F->getCallingConv());
 639     Vals.push_back(F->isDeclaration());
 640     Vals.push_back(getEncodedLinkage(F));
 641     Vals.push_back(VE.getAttributeID(F->getAttributes()));
 642     Vals.push_back(Log2_32(F->getAlignment())+1);
 643     Vals.push_back(F->hasSection() ? SectionMap[F->getSection()] : 0);
 644     Vals.push_back(getEncodedVisibility(F));
 645     Vals.push_back(F->hasGC() ? GCMap[F->getGC()] : 0);
 646     Vals.push_back(F->hasUnnamedAddr());
 647     Vals.push_back(F->hasPrefixData() ? (VE.getValueID(F->getPrefixData()) + 1)
 648                                       : 0);
 649
 650     unsigned AbbrevToUse = 0;
 651     Stream.EmitRecord(bitc::MODULE_CODE_FUNCTION, Vals, AbbrevToUse);
 652     Vals.clear();
 653   }
 654
 655   // Emit the alias information.
 656   for (Module::const_alias_iterator AI = M->alias_begin(), E = M->alias_end();
 657        AI != E; ++AI) {
 658     // ALIAS: [alias type, aliasee val#, linkage, visibility]
 659     Vals.push_back(VE.getTypeID(AI->getType()));
 660     Vals.push_back(VE.getValueID(AI->getAliasee()));
 661     Vals.push_back(getEncodedLinkage(AI));
 662     Vals.push_back(getEncodedVisibility(AI));
 663     unsigned AbbrevToUse = 0;
 664     Stream.EmitRecord(bitc::MODULE_CODE_ALIAS, Vals, AbbrevToUse);
 665     Vals.clear();
 666   }
 667 }
 668
 669 static uint64_t GetOptimizationFlags(const Value *V) {
 670   uint64_t Flags = 0;
 671
 672   if (const OverflowingBinaryOperator *OBO =
 673         dyn_cast<OverflowingBinaryOperator>(V)) {
 674     if (OBO->hasNoSignedWrap())
 675       Flags |= 1 << bitc::OBO_NO_SIGNED_WRAP;
 676     if (OBO->hasNoUnsignedWrap())
 677       Flags |= 1 << bitc::OBO_NO_UNSIGNED_WRAP;
 678   } else if (const PossiblyExactOperator *PEO =
 679                dyn_cast<PossiblyExactOperator>(V)) {
 680     if (PEO->isExact())
 681       Flags |= 1 << bitc::PEO_EXACT;
 682   } else if (const FPMathOperator *FPMO =
 683              dyn_cast<const FPMathOperator>(V)) {
 684     if (FPMO->hasUnsafeAlgebra())
 685       Flags |= FastMathFlags::UnsafeAlgebra;
 686     if (FPMO->hasNoNaNs())
 687       Flags |= FastMathFlags::NoNaNs;
 688     if (FPMO->hasNoInfs())
 689       Flags |= FastMathFlags::NoInfs;
 690     if (FPMO->hasNoSignedZeros())
 691       Flags |= FastMathFlags::NoSignedZeros;
 692     if (FPMO->hasAllowReciprocal())
 693       Flags |= FastMathFlags::AllowReciprocal;
 694   }
 695
 696   return Flags;
 697 }
 698
 699 static void WriteMDNode(const MDNode *N,
 700                         const ValueEnumerator &VE,
 701                         BitstreamWriter &Stream,
 702                         SmallVectorImpl<uint64_t> &Record) {
 703   for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
 704     if (N->getOperand(i)) {
 705       Record.push_back(VE.getTypeID(N->getOperand(i)->getType()));
 706       Record.push_back(VE.getValueID(N->getOperand(i)));
 707     } else {
 708       Record.push_back(VE.getTypeID(Type::getVoidTy(N->getContext())));
 709       Record.push_back(0);
 710     }
 711   }
 712   unsigned MDCode = N->isFunctionLocal() ? bitc::METADATA_FN_NODE :
 713                                            bitc::METADATA_NODE;
 714   Stream.EmitRecord(MDCode, Record, 0);
 715   Record.clear();
 716 }
 717
 718 static void WriteModuleMetadata(const Module *M,
 719                                 const ValueEnumerator &VE,
 720                                 BitstreamWriter &Stream) {
 721   const ValueEnumerator::ValueList &Vals = VE.getMDValues();
 722   bool StartedMetadataBlock = false;
 723   unsigned MDSAbbrev = 0;
 724   SmallVector<uint64_t, 64> Record;
 725   for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
 726
 727     if (const MDNode *N = dyn_cast<MDNode>(Vals[i].first)) {
 728       if (!N->isFunctionLocal() || !N->getFunction()) {
 729         if (!StartedMetadataBlock) {
 730           Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 731           StartedMetadataBlock = true;
 732         }
 733         WriteMDNode(N, VE, Stream, Record);
 734       }
 735     } else if (const MDString *MDS = dyn_cast<MDString>(Vals[i].first)) {
 736       if (!StartedMetadataBlock)  {
 737         Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 738
 739         // Abbrev for METADATA_STRING.
 740         BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 741         Abbv->Add(BitCodeAbbrevOp(bitc::METADATA_STRING));
 742         Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 743         Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
 744         MDSAbbrev = Stream.EmitAbbrev(Abbv);
 745         StartedMetadataBlock = true;
 746       }
 747
 748       // Code: [strchar x N]
 749       Record.append(MDS->begin(), MDS->end());
 750
 751       // Emit the finished record.
 752       Stream.EmitRecord(bitc::METADATA_STRING, Record, MDSAbbrev);
 753       Record.clear();
 754     }
 755   }
 756
 757   // Write named metadata.
 758   for (Module::const_named_metadata_iterator I = M->named_metadata_begin(),
 759        E = M->named_metadata_end(); I != E; ++I) {
 760     const NamedMDNode *NMD = I;
 761     if (!StartedMetadataBlock)  {
 762       Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 763       StartedMetadataBlock = true;
 764     }
 765
 766     // Write name.
 767     StringRef Str = NMD->getName();
 768     for (unsigned i = 0, e = Str.size(); i != e; ++i)
 769       Record.push_back(Str[i]);
 770     Stream.EmitRecord(bitc::METADATA_NAME, Record, 0/*TODO*/);
 771     Record.clear();
 772
 773     // Write named metadata operands.
 774     for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
 775       Record.push_back(VE.getValueID(NMD->getOperand(i)));
 776     Stream.EmitRecord(bitc::METADATA_NAMED_NODE, Record, 0);
 777     Record.clear();
 778   }
 779
 780   if (StartedMetadataBlock)
 781     Stream.ExitBlock();
 782 }
 783
 784 static void WriteFunctionLocalMetadata(const Function &F,
 785                                        const ValueEnumerator &VE,
 786                                        BitstreamWriter &Stream) {
 787   bool StartedMetadataBlock = false;
 788   SmallVector<uint64_t, 64> Record;
 789   const SmallVectorImpl<const MDNode *> &Vals = VE.getFunctionLocalMDValues();
 790   for (unsigned i = 0, e = Vals.size(); i != e; ++i)
 791     if (const MDNode *N = Vals[i])
 792       if (N->isFunctionLocal() && N->getFunction() == &F) {
 793         if (!StartedMetadataBlock) {
 794           Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 795           StartedMetadataBlock = true;
 796         }
 797         WriteMDNode(N, VE, Stream, Record);
 798       }
 799
 800   if (StartedMetadataBlock)
 801     Stream.ExitBlock();
 802 }
 803
 804 static void WriteMetadataAttachment(const Function &F,
 805                                     const ValueEnumerator &VE,
 806                                     BitstreamWriter &Stream) {
 807   Stream.EnterSubblock(bitc::METADATA_ATTACHMENT_ID, 3);
 808
 809   SmallVector<uint64_t, 64> Record;
 810
 811   // Write metadata attachments
 812   // METADATA_ATTACHMENT - [m x [value, [n x [id, mdnode]]]
 813   SmallVector<std::pair<unsigned, MDNode*>, 4> MDs;
 814
 815   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
 816     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
 817          I != E; ++I) {
 818       MDs.clear();
 819       I->getAllMetadataOtherThanDebugLoc(MDs);
 820
 821       // If no metadata, ignore instruction.
 822       if (MDs.empty()) continue;
 823
 824       Record.push_back(VE.getInstructionID(I));
 825
 826       for (unsigned i = 0, e = MDs.size(); i != e; ++i) {
 827         Record.push_back(MDs[i].first);
 828         Record.push_back(VE.getValueID(MDs[i].second));
 829       }
 830       Stream.EmitRecord(bitc::METADATA_ATTACHMENT, Record, 0);
 831       Record.clear();
 832     }
 833
 834   Stream.ExitBlock();
 835 }
 836
 837 static void WriteModuleMetadataStore(const Module *M, BitstreamWriter &Stream) {
 838   SmallVector<uint64_t, 64> Record;
 839
 840   // Write metadata kinds
 841   // METADATA_KIND - [n x [id, name]]
 842   SmallVector<StringRef, 8> Names;
 843   M->getMDKindNames(Names);
 844
 845   if (Names.empty()) return;
 846
 847   Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
 848
 849   for (unsigned MDKindID = 0, e = Names.size(); MDKindID != e; ++MDKindID) {
 850     Record.push_back(MDKindID);
 851     StringRef KName = Names[MDKindID];
 852     Record.append(KName.begin(), KName.end());
 853
 854     Stream.EmitRecord(bitc::METADATA_KIND, Record, 0);
 855     Record.clear();
 856   }
 857
 858   Stream.ExitBlock();
 859 }
 860
 861 static void emitSignedInt64(SmallVectorImpl<uint64_t> &Vals, uint64_t V) {
 862   if ((int64_t)V >= 0)
 863     Vals.push_back(V << 1);
 864   else
 865     Vals.push_back((-V << 1) | 1);
 866 }
 867
 868 static void WriteConstants(unsigned FirstVal, unsigned LastVal,
 869                            const ValueEnumerator &VE,
 870                            BitstreamWriter &Stream, bool isGlobal) {
 871   if (FirstVal == LastVal) return;
 872
 873   Stream.EnterSubblock(bitc::CONSTANTS_BLOCK_ID, 4);
 874
 875   unsigned AggregateAbbrev = 0;
 876   unsigned String8Abbrev = 0;
 877   unsigned CString7Abbrev = 0;
 878   unsigned CString6Abbrev = 0;
 879   // If this is a constant pool for the module, emit module-specific abbrevs.
 880   if (isGlobal) {
 881     // Abbrev for CST_CODE_AGGREGATE.
 882     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
 883     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_AGGREGATE));
 884     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 885     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, Log2_32_Ceil(LastVal+1)));
 886     AggregateAbbrev = Stream.EmitAbbrev(Abbv);
 887
 888     // Abbrev for CST_CODE_STRING.
 889     Abbv = new BitCodeAbbrev();
 890     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_STRING));
 891     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 892     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
 893     String8Abbrev = Stream.EmitAbbrev(Abbv);
 894     // Abbrev for CST_CODE_CSTRING.
 895     Abbv = new BitCodeAbbrev();
 896     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CSTRING));
 897     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 898     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
 899     CString7Abbrev = Stream.EmitAbbrev(Abbv);
 900     // Abbrev for CST_CODE_CSTRING.
 901     Abbv = new BitCodeAbbrev();
 902     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CSTRING));
 903     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
 904     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
 905     CString6Abbrev = Stream.EmitAbbrev(Abbv);
 906   }
 907
 908   SmallVector<uint64_t, 64> Record;
 909
 910   const ValueEnumerator::ValueList &Vals = VE.getValues();
 911   Type *LastTy = 0;
 912   for (unsigned i = FirstVal; i != LastVal; ++i) {
 913     const Value *V = Vals[i].first;
 914     // If we need to switch types, do so now.
 915     if (V->getType() != LastTy) {
 916       LastTy = V->getType();
 917       Record.push_back(VE.getTypeID(LastTy));
 918       Stream.EmitRecord(bitc::CST_CODE_SETTYPE, Record,
 919                         CONSTANTS_SETTYPE_ABBREV);
 920       Record.clear();
 921     }
 922
 923     if (const InlineAsm *IA = dyn_cast<InlineAsm>(V)) {
 924       Record.push_back(unsigned(IA->hasSideEffects()) |
 925                        unsigned(IA->isAlignStack()) << 1 |
 926                        unsigned(IA->getDialect()&1) << 2);
 927
 928       // Add the asm string.
 929       const std::string &AsmStr = IA->getAsmString();
 930       Record.push_back(AsmStr.size());
 931       for (unsigned i = 0, e = AsmStr.size(); i != e; ++i)
 932         Record.push_back(AsmStr[i]);
 933
 934       // Add the constraint string.
 935       const std::string &ConstraintStr = IA->getConstraintString();
 936       Record.push_back(ConstraintStr.size());
 937       for (unsigned i = 0, e = ConstraintStr.size(); i != e; ++i)
 938         Record.push_back(ConstraintStr[i]);
 939       Stream.EmitRecord(bitc::CST_CODE_INLINEASM, Record);
 940       Record.clear();
 941       continue;
 942     }
 943     const Constant *C = cast<Constant>(V);
 944     unsigned Code = -1U;
 945     unsigned AbbrevToUse = 0;
 946     if (C->isNullValue()) {
 947       Code = bitc::CST_CODE_NULL;
 948     } else if (isa<UndefValue>(C)) {
 949       Code = bitc::CST_CODE_UNDEF;
 950     } else if (const ConstantInt *IV = dyn_cast<ConstantInt>(C)) {
 951       if (IV->getBitWidth() <= 64) {
 952         uint64_t V = IV->getSExtValue();
 953         emitSignedInt64(Record, V);
 954         Code = bitc::CST_CODE_INTEGER;
 955         AbbrevToUse = CONSTANTS_INTEGER_ABBREV;
 956       } else {                             // Wide integers, > 64 bits in size.
 957         // We have an arbitrary precision integer value to write whose
 958         // bit width is > 64. However, in canonical unsigned integer
 959         // format it is likely that the high bits are going to be zero.
 960         // So, we only write the number of active words.
 961         unsigned NWords = IV->getValue().getActiveWords();
 962         const uint64_t *RawWords = IV->getValue().getRawData();
 963         for (unsigned i = 0; i != NWords; ++i) {
 964           emitSignedInt64(Record, RawWords[i]);
 965         }
 966         Code = bitc::CST_CODE_WIDE_INTEGER;
 967       }
 968     } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
 969       Code = bitc::CST_CODE_FLOAT;
 970       Type *Ty = CFP->getType();
 971       if (Ty->isHalfTy() || Ty->isFloatTy() || Ty->isDoubleTy()) {
 972         Record.push_back(CFP->getValueAPF().bitcastToAPInt().getZExtValue());
 973       } else if (Ty->isX86_FP80Ty()) {
 974         // api needed to prevent premature destruction
 975         // bits are not in the same order as a normal i80 APInt, compensate.
 976         APInt api = CFP->getValueAPF().bitcastToAPInt();
 977         const uint64_t *p = api.getRawData();
 978         Record.push_back((p[1] << 48) | (p[0] >> 16));
 979         Record.push_back(p[0] & 0xffffLL);
 980       } else if (Ty->isFP128Ty() || Ty->isPPC_FP128Ty()) {
 981         APInt api = CFP->getValueAPF().bitcastToAPInt();
 982         const uint64_t *p = api.getRawData();
 983         Record.push_back(p[0]);
 984         Record.push_back(p[1]);
 985       } else {
 986         assert (0 && "Unknown FP type!");
 987       }
 988     } else if (isa<ConstantDataSequential>(C) &&
 989                cast<ConstantDataSequential>(C)->isString()) {
 990       const ConstantDataSequential *Str = cast<ConstantDataSequential>(C);
 991       // Emit constant strings specially.
 992       unsigned NumElts = Str->getNumElements();
 993       // If this is a null-terminated string, use the denser CSTRING encoding.
 994       if (Str->isCString()) {
 995         Code = bitc::CST_CODE_CSTRING;
 996         --NumElts;  // Don't encode the null, which isn't allowed by char6.
 997       } else {
 998         Code = bitc::CST_CODE_STRING;
 999         AbbrevToUse = String8Abbrev;
1000       }
1001       bool isCStr7 = Code == bitc::CST_CODE_CSTRING;
1002       bool isCStrChar6 = Code == bitc::CST_CODE_CSTRING;
1003       for (unsigned i = 0; i != NumElts; ++i) {
1004         unsigned char V = Str->getElementAsInteger(i);
1005         Record.push_back(V);
1006         isCStr7 &= (V & 128) == 0;
1007         if (isCStrChar6)
1008           isCStrChar6 = BitCodeAbbrevOp::isChar6(V);
1009       }
1010
1011       if (isCStrChar6)
1012         AbbrevToUse = CString6Abbrev;
1013       else if (isCStr7)
1014         AbbrevToUse = CString7Abbrev;
1015     } else if (const ConstantDataSequential *CDS =
1016                   dyn_cast<ConstantDataSequential>(C)) {
1017       Code = bitc::CST_CODE_DATA;
1018       Type *EltTy = CDS->getType()->getElementType();
1019       if (isa<IntegerType>(EltTy)) {
1020         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i)
1021           Record.push_back(CDS->getElementAsInteger(i));
1022       } else if (EltTy->isFloatTy()) {
1023         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
1024           union { float F; uint32_t I; };
1025           F = CDS->getElementAsFloat(i);
1026           Record.push_back(I);
1027         }
1028       } else {
1029         assert(EltTy->isDoubleTy() && "Unknown ConstantData element type");
1030         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
1031           union { double F; uint64_t I; };
1032           F = CDS->getElementAsDouble(i);
1033           Record.push_back(I);
1034         }
1035       }
1036     } else if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
1037                isa<ConstantVector>(C)) {
1038       Code = bitc::CST_CODE_AGGREGATE;
1039       for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
1040         Record.push_back(VE.getValueID(C->getOperand(i)));
1041       AbbrevToUse = AggregateAbbrev;
1042     } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
1043       switch (CE->getOpcode()) {
1044       default:
1045         if (Instruction::isCast(CE->getOpcode())) {
1046           Code = bitc::CST_CODE_CE_CAST;
1047           Record.push_back(GetEncodedCastOpcode(CE->getOpcode()));
1048           Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
1049           Record.push_back(VE.getValueID(C->getOperand(0)));
1050           AbbrevToUse = CONSTANTS_CE_CAST_Abbrev;
1051         } else {
1052           assert(CE->getNumOperands() == 2 && "Unknown constant expr!");
1053           Code = bitc::CST_CODE_CE_BINOP;
1054           Record.push_back(GetEncodedBinaryOpcode(CE->getOpcode()));
1055           Record.push_back(VE.getValueID(C->getOperand(0)));
1056           Record.push_back(VE.getValueID(C->getOperand(1)));
1057           uint64_t Flags = GetOptimizationFlags(CE);
1058           if (Flags != 0)
1059             Record.push_back(Flags);
1060         }
1061         break;
1062       case Instruction::GetElementPtr:
1063         Code = bitc::CST_CODE_CE_GEP;
1064         if (cast<GEPOperator>(C)->isInBounds())
1065           Code = bitc::CST_CODE_CE_INBOUNDS_GEP;
1066         for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) {
1067           Record.push_back(VE.getTypeID(C->getOperand(i)->getType()));
1068           Record.push_back(VE.getValueID(C->getOperand(i)));
1069         }
1070         break;
1071       case Instruction::Select:
1072         Code = bitc::CST_CODE_CE_SELECT;
1073         Record.push_back(VE.getValueID(C->getOperand(0)));
1074         Record.push_back(VE.getValueID(C->getOperand(1)));
1075         Record.push_back(VE.getValueID(C->getOperand(2)));
1076         break;
1077       case Instruction::ExtractElement:
1078         Code = bitc::CST_CODE_CE_EXTRACTELT;
1079         Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
1080         Record.push_back(VE.getValueID(C->getOperand(0)));
1081         Record.push_back(VE.getValueID(C->getOperand(1)));
1082         break;
1083       case Instruction::InsertElement:
1084         Code = bitc::CST_CODE_CE_INSERTELT;
1085         Record.push_back(VE.getValueID(C->getOperand(0)));
1086         Record.push_back(VE.getValueID(C->getOperand(1)));
1087         Record.push_back(VE.getValueID(C->getOperand(2)));
1088         break;
1089       case Instruction::ShuffleVector:
1090         // If the return type and argument types are the same, this is a
1091         // standard shufflevector instruction.  If the types are different,
1092         // then the shuffle is widening or truncating the input vectors, and
1093         // the argument type must also be encoded.
1094         if (C->getType() == C->getOperand(0)->getType()) {
1095           Code = bitc::CST_CODE_CE_SHUFFLEVEC;
1096         } else {
1097           Code = bitc::CST_CODE_CE_SHUFVEC_EX;
1098           Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
1099         }
1100         Record.push_back(VE.getValueID(C->getOperand(0)));
1101         Record.push_back(VE.getValueID(C->getOperand(1)));
1102         Record.push_back(VE.getValueID(C->getOperand(2)));
1103         break;
1104       case Instruction::ICmp:
1105       case Instruction::FCmp:
1106         Code = bitc::CST_CODE_CE_CMP;
1107         Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
1108         Record.push_back(VE.getValueID(C->getOperand(0)));
1109         Record.push_back(VE.getValueID(C->getOperand(1)));
1110         Record.push_back(CE->getPredicate());
1111         break;
1112       }
1113     } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
1114       Code = bitc::CST_CODE_BLOCKADDRESS;
1115       Record.push_back(VE.getTypeID(BA->getFunction()->getType()));
1116       Record.push_back(VE.getValueID(BA->getFunction()));
1117       Record.push_back(VE.getGlobalBasicBlockID(BA->getBasicBlock()));
1118     } else {
1119 #ifndef NDEBUG
1120       C->dump();
1121 #endif
1122       llvm_unreachable("Unknown constant!");
1123     }
1124     Stream.EmitRecord(Code, Record, AbbrevToUse);
1125     Record.clear();
1126   }
1127
1128   Stream.ExitBlock();
1129 }
1130
1131 static void WriteModuleConstants(const ValueEnumerator &VE,
1132                                  BitstreamWriter &Stream) {
1133   const ValueEnumerator::ValueList &Vals = VE.getValues();
1134
1135   // Find the first constant to emit, which is the first non-globalvalue value.
1136   // We know globalvalues have been emitted by WriteModuleInfo.
1137   for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
1138     if (!isa<GlobalValue>(Vals[i].first)) {
1139       WriteConstants(i, Vals.size(), VE, Stream, true);
1140       return;
1141     }
1142   }
1143 }
1144
1145 /// PushValueAndType - The file has to encode both the value and type id for
1146 /// many values, because we need to know what type to create for forward
1147 /// references.  However, most operands are not forward references, so this type
1148 /// field is not needed.
1149 ///
1150 /// This function adds V's value ID to Vals.  If the value ID is higher than the
1151 /// instruction ID, then it is a forward reference, and it also includes the
1152 /// type ID.  The value ID that is written is encoded relative to the InstID.
1153 static bool PushValueAndType(const Value *V, unsigned InstID,
1154                              SmallVectorImpl<unsigned> &Vals,
1155                              ValueEnumerator &VE) {
1156   unsigned ValID = VE.getValueID(V);
1157   // Make encoding relative to the InstID.
1158   Vals.push_back(InstID - ValID);
1159   if (ValID >= InstID) {
1160     Vals.push_back(VE.getTypeID(V->getType()));
1161     return true;
1162   }
1163   return false;
1164 }
1165
1166 /// pushValue - Like PushValueAndType, but where the type of the value is
1167 /// omitted (perhaps it was already encoded in an earlier operand).
1168 static void pushValue(const Value *V, unsigned InstID,
1169                       SmallVectorImpl<unsigned> &Vals,
1170                       ValueEnumerator &VE) {
1171   unsigned ValID = VE.getValueID(V);
1172   Vals.push_back(InstID - ValID);
1173 }
1174
1175 static void pushValueSigned(const Value *V, unsigned InstID,
1176                             SmallVectorImpl<uint64_t> &Vals,
1177                             ValueEnumerator &VE) {
1178   unsigned ValID = VE.getValueID(V);
1179   int64_t diff = ((int32_t)InstID - (int32_t)ValID);
1180   emitSignedInt64(Vals, diff);
1181 }
1182
1183 /// WriteInstruction - Emit an instruction to the specified stream.
1184 static void WriteInstruction(const Instruction &I, unsigned InstID,
1185                              ValueEnumerator &VE, BitstreamWriter &Stream,
1186                              SmallVectorImpl<unsigned> &Vals) {
1187   unsigned Code = 0;
1188   unsigned AbbrevToUse = 0;
1189   VE.setInstructionID(&I);
1190   switch (I.getOpcode()) {
1191   default:
1192     if (Instruction::isCast(I.getOpcode())) {
1193       Code = bitc::FUNC_CODE_INST_CAST;
1194       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1195         AbbrevToUse = FUNCTION_INST_CAST_ABBREV;
1196       Vals.push_back(VE.getTypeID(I.getType()));
1197       Vals.push_back(GetEncodedCastOpcode(I.getOpcode()));
1198     } else {
1199       assert(isa<BinaryOperator>(I) && "Unknown instruction!");
1200       Code = bitc::FUNC_CODE_INST_BINOP;
1201       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1202         AbbrevToUse = FUNCTION_INST_BINOP_ABBREV;
1203       pushValue(I.getOperand(1), InstID, Vals, VE);
1204       Vals.push_back(GetEncodedBinaryOpcode(I.getOpcode()));
1205       uint64_t Flags = GetOptimizationFlags(&I);
1206       if (Flags != 0) {
1207         if (AbbrevToUse == FUNCTION_INST_BINOP_ABBREV)
1208           AbbrevToUse = FUNCTION_INST_BINOP_FLAGS_ABBREV;
1209         Vals.push_back(Flags);
1210       }
1211     }
1212     break;
1213
1214   case Instruction::GetElementPtr:
1215     Code = bitc::FUNC_CODE_INST_GEP;
1216     if (cast<GEPOperator>(&I)->isInBounds())
1217       Code = bitc::FUNC_CODE_INST_INBOUNDS_GEP;
1218     for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
1219       PushValueAndType(I.getOperand(i), InstID, Vals, VE);
1220     break;
1221   case Instruction::ExtractValue: {
1222     Code = bitc::FUNC_CODE_INST_EXTRACTVAL;
1223     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1224     const ExtractValueInst *EVI = cast<ExtractValueInst>(&I);
1225     for (const unsigned *i = EVI->idx_begin(), *e = EVI->idx_end(); i != e; ++i)
1226       Vals.push_back(*i);
1227     break;
1228   }
1229   case Instruction::InsertValue: {
1230     Code = bitc::FUNC_CODE_INST_INSERTVAL;
1231     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1232     PushValueAndType(I.getOperand(1), InstID, Vals, VE);
1233     const InsertValueInst *IVI = cast<InsertValueInst>(&I);
1234     for (const unsigned *i = IVI->idx_begin(), *e = IVI->idx_end(); i != e; ++i)
1235       Vals.push_back(*i);
1236     break;
1237   }
1238   case Instruction::Select:
1239     Code = bitc::FUNC_CODE_INST_VSELECT;
1240     PushValueAndType(I.getOperand(1), InstID, Vals, VE);
1241     pushValue(I.getOperand(2), InstID, Vals, VE);
1242     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1243     break;
1244   case Instruction::ExtractElement:
1245     Code = bitc::FUNC_CODE_INST_EXTRACTELT;
1246     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1247     pushValue(I.getOperand(1), InstID, Vals, VE);
1248     break;
1249   case Instruction::InsertElement:
1250     Code = bitc::FUNC_CODE_INST_INSERTELT;
1251     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1252     pushValue(I.getOperand(1), InstID, Vals, VE);
1253     pushValue(I.getOperand(2), InstID, Vals, VE);
1254     break;
1255   case Instruction::ShuffleVector:
1256     Code = bitc::FUNC_CODE_INST_SHUFFLEVEC;
1257     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1258     pushValue(I.getOperand(1), InstID, Vals, VE);
1259     pushValue(I.getOperand(2), InstID, Vals, VE);
1260     break;
1261   case Instruction::ICmp:
1262   case Instruction::FCmp:
1263     // compare returning Int1Ty or vector of Int1Ty
1264     Code = bitc::FUNC_CODE_INST_CMP2;
1265     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1266     pushValue(I.getOperand(1), InstID, Vals, VE);
1267     Vals.push_back(cast<CmpInst>(I).getPredicate());
1268     break;
1269
1270   case Instruction::Ret:
1271     {
1272       Code = bitc::FUNC_CODE_INST_RET;
1273       unsigned NumOperands = I.getNumOperands();
1274       if (NumOperands == 0)
1275         AbbrevToUse = FUNCTION_INST_RET_VOID_ABBREV;
1276       else if (NumOperands == 1) {
1277         if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1278           AbbrevToUse = FUNCTION_INST_RET_VAL_ABBREV;
1279       } else {
1280         for (unsigned i = 0, e = NumOperands; i != e; ++i)
1281           PushValueAndType(I.getOperand(i), InstID, Vals, VE);
1282       }
1283     }
1284     break;
1285   case Instruction::Br:
1286     {
1287       Code = bitc::FUNC_CODE_INST_BR;
1288       const BranchInst &II = cast<BranchInst>(I);
1289       Vals.push_back(VE.getValueID(II.getSuccessor(0)));
1290       if (II.isConditional()) {
1291         Vals.push_back(VE.getValueID(II.getSuccessor(1)));
1292         pushValue(II.getCondition(), InstID, Vals, VE);
1293       }
1294     }
1295     break;
1296   case Instruction::Switch:
1297     {
1298       Code = bitc::FUNC_CODE_INST_SWITCH;
1299       const SwitchInst &SI = cast<SwitchInst>(I);
1300       Vals.push_back(VE.getTypeID(SI.getCondition()->getType()));
1301       pushValue(SI.getCondition(), InstID, Vals, VE);
1302       Vals.push_back(VE.getValueID(SI.getDefaultDest()));
1303       for (SwitchInst::ConstCaseIt i = SI.case_begin(), e = SI.case_end();
1304            i != e; ++i) {
1305         Vals.push_back(VE.getValueID(i.getCaseValue()));
1306         Vals.push_back(VE.getValueID(i.getCaseSuccessor()));
1307       }
1308     }
1309     break;
1310   case Instruction::IndirectBr:
1311     Code = bitc::FUNC_CODE_INST_INDIRECTBR;
1312     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));
1313     // Encode the address operand as relative, but not the basic blocks.
1314     pushValue(I.getOperand(0), InstID, Vals, VE);
1315     for (unsigned i = 1, e = I.getNumOperands(); i != e; ++i)
1316       Vals.push_back(VE.getValueID(I.getOperand(i)));
1317     break;
1318
1319   case Instruction::Invoke: {
1320     const InvokeInst *II = cast<InvokeInst>(&I);
1321     const Value *Callee(II->getCalledValue());
1322     PointerType *PTy = cast<PointerType>(Callee->getType());
1323     FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1324     Code = bitc::FUNC_CODE_INST_INVOKE;
1325
1326     Vals.push_back(VE.getAttributeID(II->getAttributes()));
1327     Vals.push_back(II->getCallingConv());
1328     Vals.push_back(VE.getValueID(II->getNormalDest()));
1329     Vals.push_back(VE.getValueID(II->getUnwindDest()));
1330     PushValueAndType(Callee, InstID, Vals, VE);
1331
1332     // Emit value #'s for the fixed parameters.
1333     for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
1334       pushValue(I.getOperand(i), InstID, Vals, VE);  // fixed param.
1335
1336     // Emit type/value pairs for varargs params.
1337     if (FTy->isVarArg()) {
1338       for (unsigned i = FTy->getNumParams(), e = I.getNumOperands()-3;
1339            i != e; ++i)
1340         PushValueAndType(I.getOperand(i), InstID, Vals, VE); // vararg
1341     }
1342     break;
1343   }
1344   case Instruction::Resume:
1345     Code = bitc::FUNC_CODE_INST_RESUME;
1346     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1347     break;
1348   case Instruction::Unreachable:
1349     Code = bitc::FUNC_CODE_INST_UNREACHABLE;
1350     AbbrevToUse = FUNCTION_INST_UNREACHABLE_ABBREV;
1351     break;
1352
1353   case Instruction::PHI: {
1354     const PHINode &PN = cast<PHINode>(I);
1355     Code = bitc::FUNC_CODE_INST_PHI;
1356     // With the newer instruction encoding, forward references could give
1357     // negative valued IDs.  This is most common for PHIs, so we use
1358     // signed VBRs.
1359     SmallVector<uint64_t, 128> Vals64;
1360     Vals64.push_back(VE.getTypeID(PN.getType()));
1361     for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
1362       pushValueSigned(PN.getIncomingValue(i), InstID, Vals64, VE);
1363       Vals64.push_back(VE.getValueID(PN.getIncomingBlock(i)));
1364     }
1365     // Emit a Vals64 vector and exit.
1366     Stream.EmitRecord(Code, Vals64, AbbrevToUse);
1367     Vals64.clear();
1368     return;
1369   }
1370
1371   case Instruction::LandingPad: {
1372     const LandingPadInst &LP = cast<LandingPadInst>(I);
1373     Code = bitc::FUNC_CODE_INST_LANDINGPAD;
1374     Vals.push_back(VE.getTypeID(LP.getType()));
1375     PushValueAndType(LP.getPersonalityFn(), InstID, Vals, VE);
1376     Vals.push_back(LP.isCleanup());
1377     Vals.push_back(LP.getNumClauses());
1378     for (unsigned I = 0, E = LP.getNumClauses(); I != E; ++I) {
1379       if (LP.isCatch(I))
1380         Vals.push_back(LandingPadInst::Catch);
1381       else
1382         Vals.push_back(LandingPadInst::Filter);
1383       PushValueAndType(LP.getClause(I), InstID, Vals, VE);
1384     }
1385     break;
1386   }
1387
1388   case Instruction::Alloca:
1389     Code = bitc::FUNC_CODE_INST_ALLOCA;
1390     Vals.push_back(VE.getTypeID(I.getType()));
1391     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));
1392     Vals.push_back(VE.getValueID(I.getOperand(0))); // size.
1393     Vals.push_back(Log2_32(cast<AllocaInst>(I).getAlignment())+1);
1394     break;
1395
1396   case Instruction::Load:
1397     if (cast<LoadInst>(I).isAtomic()) {
1398       Code = bitc::FUNC_CODE_INST_LOADATOMIC;
1399       PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1400     } else {
1401       Code = bitc::FUNC_CODE_INST_LOAD;
1402       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))  // ptr
1403         AbbrevToUse = FUNCTION_INST_LOAD_ABBREV;
1404     }
1405     Vals.push_back(Log2_32(cast<LoadInst>(I).getAlignment())+1);
1406     Vals.push_back(cast<LoadInst>(I).isVolatile());
1407     if (cast<LoadInst>(I).isAtomic()) {
1408       Vals.push_back(GetEncodedOrdering(cast<LoadInst>(I).getOrdering()));
1409       Vals.push_back(GetEncodedSynchScope(cast<LoadInst>(I).getSynchScope()));
1410     }
1411     break;
1412   case Instruction::Store:
1413     if (cast<StoreInst>(I).isAtomic())
1414       Code = bitc::FUNC_CODE_INST_STOREATOMIC;
1415     else
1416       Code = bitc::FUNC_CODE_INST_STORE;
1417     PushValueAndType(I.getOperand(1), InstID, Vals, VE);  // ptrty + ptr
1418     pushValue(I.getOperand(0), InstID, Vals, VE);         // val.
1419     Vals.push_back(Log2_32(cast<StoreInst>(I).getAlignment())+1);
1420     Vals.push_back(cast<StoreInst>(I).isVolatile());
1421     if (cast<StoreInst>(I).isAtomic()) {
1422       Vals.push_back(GetEncodedOrdering(cast<StoreInst>(I).getOrdering()));
1423       Vals.push_back(GetEncodedSynchScope(cast<StoreInst>(I).getSynchScope()));
1424     }
1425     break;
1426   case Instruction::AtomicCmpXchg:
1427     Code = bitc::FUNC_CODE_INST_CMPXCHG;
1428     PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // ptrty + ptr
1429     pushValue(I.getOperand(1), InstID, Vals, VE);         // cmp.
1430     pushValue(I.getOperand(2), InstID, Vals, VE);         // newval.
1431     Vals.push_back(cast<AtomicCmpXchgInst>(I).isVolatile());
1432     Vals.push_back(GetEncodedOrdering(
1433                      cast<AtomicCmpXchgInst>(I).getOrdering()));
1434     Vals.push_back(GetEncodedSynchScope(
1435                      cast<AtomicCmpXchgInst>(I).getSynchScope()));
1436     break;
1437   case Instruction::AtomicRMW:
1438     Code = bitc::FUNC_CODE_INST_ATOMICRMW;
1439     PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // ptrty + ptr
1440     pushValue(I.getOperand(1), InstID, Vals, VE);         // val.
1441     Vals.push_back(GetEncodedRMWOperation(
1442                      cast<AtomicRMWInst>(I).getOperation()));
1443     Vals.push_back(cast<AtomicRMWInst>(I).isVolatile());
1444     Vals.push_back(GetEncodedOrdering(cast<AtomicRMWInst>(I).getOrdering()));
1445     Vals.push_back(GetEncodedSynchScope(
1446                      cast<AtomicRMWInst>(I).getSynchScope()));
1447     break;
1448   case Instruction::Fence:
1449     Code = bitc::FUNC_CODE_INST_FENCE;
1450     Vals.push_back(GetEncodedOrdering(cast<FenceInst>(I).getOrdering()));
1451     Vals.push_back(GetEncodedSynchScope(cast<FenceInst>(I).getSynchScope()));
1452     break;
1453   case Instruction::Call: {
1454     const CallInst &CI = cast<CallInst>(I);
1455     PointerType *PTy = cast<PointerType>(CI.getCalledValue()->getType());
1456     FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1457
1458     Code = bitc::FUNC_CODE_INST_CALL;
1459
1460     Vals.push_back(VE.getAttributeID(CI.getAttributes()));
1461     Vals.push_back((CI.getCallingConv() << 1) | unsigned(CI.isTailCall()));
1462     PushValueAndType(CI.getCalledValue(), InstID, Vals, VE);  // Callee
1463
1464     // Emit value #'s for the fixed parameters.
1465     for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i) {
1466       // Check for labels (can happen with asm labels).
1467       if (FTy->getParamType(i)->isLabelTy())
1468         Vals.push_back(VE.getValueID(CI.getArgOperand(i)));
1469       else
1470         pushValue(CI.getArgOperand(i), InstID, Vals, VE);  // fixed param.
1471     }
1472
1473     // Emit type/value pairs for varargs params.
1474     if (FTy->isVarArg()) {
1475       for (unsigned i = FTy->getNumParams(), e = CI.getNumArgOperands();
1476            i != e; ++i)
1477         PushValueAndType(CI.getArgOperand(i), InstID, Vals, VE);  // varargs
1478     }
1479     break;
1480   }
1481   case Instruction::VAArg:
1482     Code = bitc::FUNC_CODE_INST_VAARG;
1483     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));   // valistty
1484     pushValue(I.getOperand(0), InstID, Vals, VE); // valist.
1485     Vals.push_back(VE.getTypeID(I.getType())); // restype.
1486     break;
1487   }
1488
1489   Stream.EmitRecord(Code, Vals, AbbrevToUse);
1490   Vals.clear();
1491 }
1492
1493 // Emit names for globals/functions etc.
1494 static void WriteValueSymbolTable(const ValueSymbolTable &VST,
1495                                   const ValueEnumerator &VE,
1496                                   BitstreamWriter &Stream) {
1497   if (VST.empty()) return;
1498   Stream.EnterSubblock(bitc::VALUE_SYMTAB_BLOCK_ID, 4);
1499
1500   // FIXME: Set up the abbrev, we know how many values there are!
1501   // FIXME: We know if the type names can use 7-bit ascii.
1502   SmallVector<unsigned, 64> NameVals;
1503
1504   for (ValueSymbolTable::const_iterator SI = VST.begin(), SE = VST.end();
1505        SI != SE; ++SI) {
1506
1507     const ValueName &Name = *SI;
1508
1509     // Figure out the encoding to use for the name.
1510     bool is7Bit = true;
1511     bool isChar6 = true;
1512     for (const char *C = Name.getKeyData(), *E = C+Name.getKeyLength();
1513          C != E; ++C) {
1514       if (isChar6)
1515         isChar6 = BitCodeAbbrevOp::isChar6(*C);
1516       if ((unsigned char)*C & 128) {
1517         is7Bit = false;
1518         break;  // don't bother scanning the rest.
1519       }
1520     }
1521
1522     unsigned AbbrevToUse = VST_ENTRY_8_ABBREV;
1523
1524     // VST_ENTRY:   [valueid, namechar x N]
1525     // VST_BBENTRY: [bbid, namechar x N]
1526     unsigned Code;
1527     if (isa<BasicBlock>(SI->getValue())) {
1528       Code = bitc::VST_CODE_BBENTRY;
1529       if (isChar6)
1530         AbbrevToUse = VST_BBENTRY_6_ABBREV;
1531     } else {
1532       Code = bitc::VST_CODE_ENTRY;
1533       if (isChar6)
1534         AbbrevToUse = VST_ENTRY_6_ABBREV;
1535       else if (is7Bit)
1536         AbbrevToUse = VST_ENTRY_7_ABBREV;
1537     }
1538
1539     NameVals.push_back(VE.getValueID(SI->getValue()));
1540     for (const char *P = Name.getKeyData(),
1541          *E = Name.getKeyData()+Name.getKeyLength(); P != E; ++P)
1542       NameVals.push_back((unsigned char)*P);
1543
1544     // Emit the finished record.
1545     Stream.EmitRecord(Code, NameVals, AbbrevToUse);
1546     NameVals.clear();
1547   }
1548   Stream.ExitBlock();
1549 }
1550
1551 /// WriteFunction - Emit a function body to the module stream.
1552 static void WriteFunction(const Function &F, ValueEnumerator &VE,
1553                           BitstreamWriter &Stream) {
1554   Stream.EnterSubblock(bitc::FUNCTION_BLOCK_ID, 4);
1555   VE.incorporateFunction(F);
1556
1557   SmallVector<unsigned, 64> Vals;
1558
1559   // Emit the number of basic blocks, so the reader can create them ahead of
1560   // time.
1561   Vals.push_back(VE.getBasicBlocks().size());
1562   Stream.EmitRecord(bitc::FUNC_CODE_DECLAREBLOCKS, Vals);
1563   Vals.clear();
1564
1565   // If there are function-local constants, emit them now.
1566   unsigned CstStart, CstEnd;
1567   VE.getFunctionConstantRange(CstStart, CstEnd);
1568   WriteConstants(CstStart, CstEnd, VE, Stream, false);
1569
1570   // If there is function-local metadata, emit it now.
1571   WriteFunctionLocalMetadata(F, VE, Stream);
1572
1573   // Keep a running idea of what the instruction ID is.
1574   unsigned InstID = CstEnd;
1575
1576   bool NeedsMetadataAttachment = false;
1577
1578   DebugLoc LastDL;
1579
1580   // Finally, emit all the instructions, in order.
1581   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
1582     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
1583          I != E; ++I) {
1584       WriteInstruction(*I, InstID, VE, Stream, Vals);
1585
1586       if (!I->getType()->isVoidTy())
1587         ++InstID;
1588
1589       // If the instruction has metadata, write a metadata attachment later.
1590       NeedsMetadataAttachment |= I->hasMetadataOtherThanDebugLoc();
1591
1592       // If the instruction has a debug location, emit it.
1593       DebugLoc DL = I->getDebugLoc();
1594       if (DL.isUnknown()) {
1595         // nothing todo.
1596       } else if (DL == LastDL) {
1597         // Just repeat the same debug loc as last time.
1598         Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC_AGAIN, Vals);
1599       } else {
1600         MDNode *Scope, *IA;
1601         DL.getScopeAndInlinedAt(Scope, IA, I->getContext());
1602
1603         Vals.push_back(DL.getLine());
1604         Vals.push_back(DL.getCol());
1605         Vals.push_back(Scope ? VE.getValueID(Scope)+1 : 0);
1606         Vals.push_back(IA ? VE.getValueID(IA)+1 : 0);
1607         Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC, Vals);
1608         Vals.clear();
1609
1610         LastDL = DL;
1611       }
1612     }
1613
1614   // Emit names for all the instructions etc.
1615   WriteValueSymbolTable(F.getValueSymbolTable(), VE, Stream);
1616
1617   if (NeedsMetadataAttachment)
1618     WriteMetadataAttachment(F, VE, Stream);
1619   VE.purgeFunction();
1620   Stream.ExitBlock();
1621 }
1622
1623 // Emit blockinfo, which defines the standard abbreviations etc.
1624 static void WriteBlockInfo(const ValueEnumerator &VE, BitstreamWriter &Stream) {
1625   // We only want to emit block info records for blocks that have multiple
1626   // instances: CONSTANTS_BLOCK, FUNCTION_BLOCK and VALUE_SYMTAB_BLOCK.
1627   // Other blocks can define their abbrevs inline.
1628   Stream.EnterBlockInfoBlock(2);
1629
1630   { // 8-bit fixed-width VST_ENTRY/VST_BBENTRY strings.
1631     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1632     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3));
1633     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1634     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1635     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
1636     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1637                                    Abbv) != VST_ENTRY_8_ABBREV)
1638       llvm_unreachable("Unexpected abbrev ordering!");
1639   }
1640
1641   { // 7-bit fixed width VST_ENTRY strings.
1642     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1643     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
1644     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1645     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1646     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
1647     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1648                                    Abbv) != VST_ENTRY_7_ABBREV)
1649       llvm_unreachable("Unexpected abbrev ordering!");
1650   }
1651   { // 6-bit char6 VST_ENTRY strings.
1652     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1653     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
1654     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1655     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1656     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
1657     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1658                                    Abbv) != VST_ENTRY_6_ABBREV)
1659       llvm_unreachable("Unexpected abbrev ordering!");
1660   }
1661   { // 6-bit char6 VST_BBENTRY strings.
1662     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1663     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_BBENTRY));
1664     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1665     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1666     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
1667     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1668                                    Abbv) != VST_BBENTRY_6_ABBREV)
1669       llvm_unreachable("Unexpected abbrev ordering!");
1670   }
1671
1672
1673
1674   { // SETTYPE abbrev for CONSTANTS_BLOCK.
1675     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1676     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_SETTYPE));
1677     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
1678                               Log2_32_Ceil(VE.getTypes().size()+1)));
1679     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1680                                    Abbv) != CONSTANTS_SETTYPE_ABBREV)
1681       llvm_unreachable("Unexpected abbrev ordering!");
1682   }
1683
1684   { // INTEGER abbrev for CONSTANTS_BLOCK.
1685     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1686     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_INTEGER));
1687     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1688     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1689                                    Abbv) != CONSTANTS_INTEGER_ABBREV)
1690       llvm_unreachable("Unexpected abbrev ordering!");
1691   }
1692
1693   { // CE_CAST abbrev for CONSTANTS_BLOCK.
1694     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1695     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CE_CAST));
1696     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));  // cast opc
1697     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,       // typeid
1698                               Log2_32_Ceil(VE.getTypes().size()+1)));
1699     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));    // value id
1700
1701     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1702                                    Abbv) != CONSTANTS_CE_CAST_Abbrev)
1703       llvm_unreachable("Unexpected abbrev ordering!");
1704   }
1705   { // NULL abbrev for CONSTANTS_BLOCK.
1706     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1707     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_NULL));
1708     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1709                                    Abbv) != CONSTANTS_NULL_Abbrev)
1710       llvm_unreachable("Unexpected abbrev ordering!");
1711   }
1712
1713   // FIXME: This should only use space for first class types!
1714
1715   { // INST_LOAD abbrev for FUNCTION_BLOCK.
1716     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1717     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_LOAD));
1718     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Ptr
1719     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // Align
1720     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // volatile
1721     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1722                                    Abbv) != FUNCTION_INST_LOAD_ABBREV)
1723       llvm_unreachable("Unexpected abbrev ordering!");
1724   }
1725   { // INST_BINOP abbrev for FUNCTION_BLOCK.
1726     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1727     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_BINOP));
1728     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
1729     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // RHS
1730     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
1731     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1732                                    Abbv) != FUNCTION_INST_BINOP_ABBREV)
1733       llvm_unreachable("Unexpected abbrev ordering!");
1734   }
1735   { // INST_BINOP_FLAGS abbrev for FUNCTION_BLOCK.
1736     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1737     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_BINOP));
1738     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
1739     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // RHS
1740     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
1741     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7)); // flags
1742     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1743                                    Abbv) != FUNCTION_INST_BINOP_FLAGS_ABBREV)
1744       llvm_unreachable("Unexpected abbrev ordering!");
1745   }
1746   { // INST_CAST abbrev for FUNCTION_BLOCK.
1747     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1748     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_CAST));
1749     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));    // OpVal
1750     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,       // dest ty
1751                               Log2_32_Ceil(VE.getTypes().size()+1)));
1752     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));  // opc
1753     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1754                                    Abbv) != FUNCTION_INST_CAST_ABBREV)
1755       llvm_unreachable("Unexpected abbrev ordering!");
1756   }
1757
1758   { // INST_RET abbrev for FUNCTION_BLOCK.
1759     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1760     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_RET));
1761     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1762                                    Abbv) != FUNCTION_INST_RET_VOID_ABBREV)
1763       llvm_unreachable("Unexpected abbrev ordering!");
1764   }
1765   { // INST_RET abbrev for FUNCTION_BLOCK.
1766     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1767     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_RET));
1768     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // ValID
1769     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1770                                    Abbv) != FUNCTION_INST_RET_VAL_ABBREV)
1771       llvm_unreachable("Unexpected abbrev ordering!");
1772   }
1773   { // INST_UNREACHABLE abbrev for FUNCTION_BLOCK.
1774     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1775     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_UNREACHABLE));
1776     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1777                                    Abbv) != FUNCTION_INST_UNREACHABLE_ABBREV)
1778       llvm_unreachable("Unexpected abbrev ordering!");
1779   }
1780
1781   Stream.ExitBlock();
1782 }
1783
1784 // Sort the Users based on the order in which the reader parses the bitcode
1785 // file.
1786 static bool bitcodereader_order(const User *lhs, const User *rhs) {
1787   // TODO: Implement.
1788   return true;
1789 }
1790
1791 static void WriteUseList(const Value *V, const ValueEnumerator &VE,
1792                          BitstreamWriter &Stream) {
1793
1794   // One or zero uses can't get out of order.
1795   if (V->use_empty() || V->hasNUses(1))
1796     return;
1797
1798   // Make a copy of the in-memory use-list for sorting.
1799   unsigned UseListSize = std::distance(V->use_begin(), V->use_end());
1800   SmallVector<const User*, 8> UseList;
1801   UseList.reserve(UseListSize);
1802   for (Value::const_use_iterator I = V->use_begin(), E = V->use_end();
1803        I != E; ++I) {
1804     const User *U = *I;
1805     UseList.push_back(U);
1806   }
1807
1808   // Sort the copy based on the order read by the BitcodeReader.
1809   std::sort(UseList.begin(), UseList.end(), bitcodereader_order);
1810
1811   // TODO: Generate a diff between the BitcodeWriter in-memory use-list and the
1812   // sorted list (i.e., the expected BitcodeReader in-memory use-list).
1813
1814   // TODO: Emit the USELIST_CODE_ENTRYs.
1815 }
1816
1817 static void WriteFunctionUseList(const Function *F, ValueEnumerator &VE,
1818                                  BitstreamWriter &Stream) {
1819   VE.incorporateFunction(*F);
1820
1821   for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
1822        AI != AE; ++AI)
1823     WriteUseList(AI, VE, Stream);
1824   for (Function::const_iterator BB = F->begin(), FE = F->end(); BB != FE;
1825        ++BB) {
1826     WriteUseList(BB, VE, Stream);
1827     for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end(); II != IE;
1828          ++II) {
1829       WriteUseList(II, VE, Stream);
1830       for (User::const_op_iterator OI = II->op_begin(), E = II->op_end();
1831            OI != E; ++OI) {
1832         if ((isa<Constant>(*OI) && !isa<GlobalValue>(*OI)) ||
1833             isa<InlineAsm>(*OI))
1834           WriteUseList(*OI, VE, Stream);
1835       }
1836     }
1837   }
1838   VE.purgeFunction();
1839 }
1840
1841 // Emit use-lists.
1842 static void WriteModuleUseLists(const Module *M, ValueEnumerator &VE,
1843                                 BitstreamWriter &Stream) {
1844   Stream.EnterSubblock(bitc::USELIST_BLOCK_ID, 3);
1845
1846   // XXX: this modifies the module, but in a way that should never change the
1847   // behavior of any pass or codegen in LLVM. The problem is that GVs may
1848   // contain entries in the use_list that do not exist in the Module and are
1849   // not stored in the .bc file.
1850   for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
1851        I != E; ++I)
1852     I->removeDeadConstantUsers();
1853
1854   // Write the global variables.
1855   for (Module::const_global_iterator GI = M->global_begin(),
1856          GE = M->global_end(); GI != GE; ++GI) {
1857     WriteUseList(GI, VE, Stream);
1858
1859     // Write the global variable initializers.
1860     if (GI->hasInitializer())
1861       WriteUseList(GI->getInitializer(), VE, Stream);
1862   }
1863
1864   // Write the functions.
1865   for (Module::const_iterator FI = M->begin(), FE = M->end(); FI != FE; ++FI) {
1866     WriteUseList(FI, VE, Stream);
1867     if (!FI->isDeclaration())
1868       WriteFunctionUseList(FI, VE, Stream);
1869     if (FI->hasPrefixData())
1870       WriteUseList(FI->getPrefixData(), VE, Stream);
1871   }
1872
1873   // Write the aliases.
1874   for (Module::const_alias_iterator AI = M->alias_begin(), AE = M->alias_end();
1875        AI != AE; ++AI) {
1876     WriteUseList(AI, VE, Stream);
1877     WriteUseList(AI->getAliasee(), VE, Stream);
1878   }
1879
1880   Stream.ExitBlock();
1881 }
1882
1883 /// WriteModule - Emit the specified module to the bitstream.
1884 static void WriteModule(const Module *M, BitstreamWriter &Stream) {
1885   Stream.EnterSubblock(bitc::MODULE_BLOCK_ID, 3);
1886
1887   SmallVector<unsigned, 1> Vals;
1888   unsigned CurVersion = 1;
1889   Vals.push_back(CurVersion);
1890   Stream.EmitRecord(bitc::MODULE_CODE_VERSION, Vals);
1891
1892   // Analyze the module, enumerating globals, functions, etc.
1893   ValueEnumerator VE(M);
1894
1895   // Emit blockinfo, which defines the standard abbreviations etc.
1896   WriteBlockInfo(VE, Stream);
1897
1898   // Emit information about attribute groups.
1899   WriteAttributeGroupTable(VE, Stream);
1900
1901   // Emit information about parameter attributes.
1902   WriteAttributeTable(VE, Stream);
1903
1904   // Emit information describing all of the types in the module.
1905   WriteTypeTable(VE, Stream);
1906
1907   // Emit top-level description of module, including target triple, inline asm,
1908   // descriptors for global variables, and function prototype info.
1909   WriteModuleInfo(M, VE, Stream);
1910
1911   // Emit constants.
1912   WriteModuleConstants(VE, Stream);
1913
1914   // Emit metadata.
1915   WriteModuleMetadata(M, VE, Stream);
1916
1917   // Emit metadata.
1918   WriteModuleMetadataStore(M, Stream);
1919
1920   // Emit names for globals/functions etc.
1921   WriteValueSymbolTable(M->getValueSymbolTable(), VE, Stream);
1922
1923   // Emit use-lists.
1924   if (EnablePreserveUseListOrdering)
1925     WriteModuleUseLists(M, VE, Stream);
1926
1927   // Emit function bodies.
1928   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F)
1929     if (!F->isDeclaration())
1930       WriteFunction(*F, VE, Stream);
1931
1932   Stream.ExitBlock();
1933 }
1934
1935 /// EmitDarwinBCHeader - If generating a bc file on darwin, we have to emit a
1936 /// header and trailer to make it compatible with the system archiver.  To do
1937 /// this we emit the following header, and then emit a trailer that pads the
1938 /// file out to be a multiple of 16 bytes.
1939 ///
1940 /// struct bc_header {
1941 ///   uint32_t Magic;         // 0x0B17C0DE
1942 ///   uint32_t Version;       // Version, currently always 0.
1943 ///   uint32_t BitcodeOffset; // Offset to traditional bitcode file.
1944 ///   uint32_t BitcodeSize;   // Size of traditional bitcode file.
1945 ///   uint32_t CPUType;       // CPU specifier.
1946 ///   ... potentially more later ...
1947 /// };
1948 enum {
1949   DarwinBCSizeFieldOffset = 3*4, // Offset to bitcode_size.
1950   DarwinBCHeaderSize = 5*4
1951 };
1952
1953 static void WriteInt32ToBuffer(uint32_t Value, SmallVectorImpl<char> &Buffer,
1954                                uint32_t &Position) {
1955   Buffer[Position + 0] = (unsigned char) (Value >>  0);
1956   Buffer[Position + 1] = (unsigned char) (Value >>  8);
1957   Buffer[Position + 2] = (unsigned char) (Value >> 16);
1958   Buffer[Position + 3] = (unsigned char) (Value >> 24);
1959   Position += 4;
1960 }
1961
1962 static void EmitDarwinBCHeaderAndTrailer(SmallVectorImpl<char> &Buffer,
1963                                          const Triple &TT) {
1964   unsigned CPUType = ~0U;
1965
1966   // Match x86_64-*, i[3-9]86-*, powerpc-*, powerpc64-*, arm-*, thumb-*,
1967   // armv[0-9]-*, thumbv[0-9]-*, armv5te-*, or armv6t2-*. The CPUType is a magic
1968   // number from /usr/include/mach/machine.h.  It is ok to reproduce the
1969   // specific constants here because they are implicitly part of the Darwin ABI.
1970   enum {
1971     DARWIN_CPU_ARCH_ABI64      = 0x01000000,
1972     DARWIN_CPU_TYPE_X86        = 7,
1973     DARWIN_CPU_TYPE_ARM        = 12,
1974     DARWIN_CPU_TYPE_POWERPC    = 18
1975   };
1976
1977   Triple::ArchType Arch = TT.getArch();
1978   if (Arch == Triple::x86_64)
1979     CPUType = DARWIN_CPU_TYPE_X86 | DARWIN_CPU_ARCH_ABI64;
1980   else if (Arch == Triple::x86)
1981     CPUType = DARWIN_CPU_TYPE_X86;
1982   else if (Arch == Triple::ppc)
1983     CPUType = DARWIN_CPU_TYPE_POWERPC;
1984   else if (Arch == Triple::ppc64)
1985     CPUType = DARWIN_CPU_TYPE_POWERPC | DARWIN_CPU_ARCH_ABI64;
1986   else if (Arch == Triple::arm || Arch == Triple::thumb)
1987     CPUType = DARWIN_CPU_TYPE_ARM;
1988
1989   // Traditional Bitcode starts after header.
1990   assert(Buffer.size() >= DarwinBCHeaderSize &&
1991          "Expected header size to be reserved");
1992   unsigned BCOffset = DarwinBCHeaderSize;
1993   unsigned BCSize = Buffer.size()-DarwinBCHeaderSize;
1994
1995   // Write the magic and version.
1996   unsigned Position = 0;
1997   WriteInt32ToBuffer(0x0B17C0DE , Buffer, Position);
1998   WriteInt32ToBuffer(0          , Buffer, Position); // Version.
1999   WriteInt32ToBuffer(BCOffset   , Buffer, Position);
2000   WriteInt32ToBuffer(BCSize     , Buffer, Position);
2001   WriteInt32ToBuffer(CPUType    , Buffer, Position);
2002
2003   // If the file is not a multiple of 16 bytes, insert dummy padding.
2004   while (Buffer.size() & 15)
2005     Buffer.push_back(0);
2006 }
2007
2008 /// WriteBitcodeToFile - Write the specified module to the specified output
2009 /// stream.
2010 void llvm::WriteBitcodeToFile(const Module *M, raw_ostream &Out) {
2011   SmallVector<char, 0> Buffer;
2012   Buffer.reserve(256*1024);
2013
2014   // If this is darwin or another generic macho target, reserve space for the
2015   // header.
2016   Triple TT(M->getTargetTriple());
2017   if (TT.isOSDarwin())
2018     Buffer.insert(Buffer.begin(), DarwinBCHeaderSize, 0);
2019
2020   // Emit the module into the buffer.
2021   {
2022     BitstreamWriter Stream(Buffer);
2023
2024     // Emit the file header.
2025     Stream.Emit((unsigned)'B', 8);
2026     Stream.Emit((unsigned)'C', 8);
2027     Stream.Emit(0x0, 4);
2028     Stream.Emit(0xC, 4);
2029     Stream.Emit(0xE, 4);
2030     Stream.Emit(0xD, 4);
2031
2032     // Emit the module.
2033     WriteModule(M, Stream);
2034   }
2035
2036   if (TT.isOSDarwin())
2037     EmitDarwinBCHeaderAndTrailer(Buffer, TT);
2038
2039   // Write the generated bitstream to "Out".
2040   Out.write((char*)&Buffer.front(), Buffer.size());
2041 }