lib/Bitcode/Writer/BitcodeWriter.cpp

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