BitcodeReader.cpp

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//===- BitcodeReader.cpp - Internal BitcodeReader implementation ----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This header defines the BitcodeReader class.
//
//===----------------------------------------------------------------------===//

#include "llvm/Bitcode/ReaderWriter.h"
#include "BitcodeReader.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/InlineAsm.h"
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/AutoUpgrade.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/OperandTraits.h"
using namespace llvm;

void BitcodeReader::FreeState() {
  delete Buffer;
  Buffer = 0;
  std::vector<PATypeHolder>().swap(TypeList);
  ValueList.clear();
  
  std::vector<AttrListPtr>().swap(MAttributes);
  std::vector<BasicBlock*>().swap(FunctionBBs);
  std::vector<Function*>().swap(FunctionsWithBodies);
  DeferredFunctionInfo.clear();
}

//===----------------------------------------------------------------------===//
//  Helper functions to implement forward reference resolution, etc.
//===----------------------------------------------------------------------===//

/// ConvertToString - Convert a string from a record into an std::string, return
/// true on failure.
template<typename StrTy>
static bool ConvertToString(SmallVector<uint64_t, 64> &Record, unsigned Idx,
                            StrTy &Result) {
  if (Idx > Record.size())
    return true;
  
  for (unsigned i = Idx, e = Record.size(); i != e; ++i)
    Result += (char)Record[i];
  return false;
}

static GlobalValue::LinkageTypes GetDecodedLinkage(unsigned Val) {
  switch (Val) {
  default: // Map unknown/new linkages to external
  case 0: return GlobalValue::ExternalLinkage;
  case 1: return GlobalValue::WeakLinkage;
  case 2: return GlobalValue::AppendingLinkage;
  case 3: return GlobalValue::InternalLinkage;
  case 4: return GlobalValue::LinkOnceLinkage;
  case 5: return GlobalValue::DLLImportLinkage;
  case 6: return GlobalValue::DLLExportLinkage;
  case 7: return GlobalValue::ExternalWeakLinkage;
  case 8: return GlobalValue::CommonLinkage;
  }
}

static GlobalValue::VisibilityTypes GetDecodedVisibility(unsigned Val) {
  switch (Val) {
  default: // Map unknown visibilities to default.
  case 0: return GlobalValue::DefaultVisibility;
  case 1: return GlobalValue::HiddenVisibility;
  case 2: return GlobalValue::ProtectedVisibility;
  }
}

static int GetDecodedCastOpcode(unsigned Val) {
  switch (Val) {
  default: return -1;
  case bitc::CAST_TRUNC   : return Instruction::Trunc;
  case bitc::CAST_ZEXT    : return Instruction::ZExt;
  case bitc::CAST_SEXT    : return Instruction::SExt;
  case bitc::CAST_FPTOUI  : return Instruction::FPToUI;
  case bitc::CAST_FPTOSI  : return Instruction::FPToSI;
  case bitc::CAST_UITOFP  : return Instruction::UIToFP;
  case bitc::CAST_SITOFP  : return Instruction::SIToFP;
  case bitc::CAST_FPTRUNC : return Instruction::FPTrunc;
  case bitc::CAST_FPEXT   : return Instruction::FPExt;
  case bitc::CAST_PTRTOINT: return Instruction::PtrToInt;
  case bitc::CAST_INTTOPTR: return Instruction::IntToPtr;
  case bitc::CAST_BITCAST : return Instruction::BitCast;
  }
}
static int GetDecodedBinaryOpcode(unsigned Val, const Type *Ty) {
  switch (Val) {
  default: return -1;
  case bitc::BINOP_ADD:  return Instruction::Add;
  case bitc::BINOP_SUB:  return Instruction::Sub;
  case bitc::BINOP_MUL:  return Instruction::Mul;
  case bitc::BINOP_UDIV: return Instruction::UDiv;
  case bitc::BINOP_SDIV:
    return Ty->isFPOrFPVector() ? Instruction::FDiv : Instruction::SDiv;
  case bitc::BINOP_UREM: return Instruction::URem;
  case bitc::BINOP_SREM:
    return Ty->isFPOrFPVector() ? Instruction::FRem : Instruction::SRem;
  case bitc::BINOP_SHL:  return Instruction::Shl;
  case bitc::BINOP_LSHR: return Instruction::LShr;
  case bitc::BINOP_ASHR: return Instruction::AShr;
  case bitc::BINOP_AND:  return Instruction::And;
  case bitc::BINOP_OR:   return Instruction::Or;
  case bitc::BINOP_XOR:  return Instruction::Xor;
  }
}

namespace llvm {
namespace {
  /// @brief A class for maintaining the slot number definition
  /// as a placeholder for the actual definition for forward constants defs.
  class ConstantPlaceHolder : public ConstantExpr {
    ConstantPlaceHolder();                       // DO NOT IMPLEMENT
    void operator=(const ConstantPlaceHolder &); // DO NOT IMPLEMENT
  public:
    // allocate space for exactly one operand
    void *operator new(size_t s) {
      return User::operator new(s, 1);
    }
    explicit ConstantPlaceHolder(const Type *Ty)
      : ConstantExpr(Ty, Instruction::UserOp1, &Op<0>(), 1) {
      Op<0>() = UndefValue::get(Type::Int32Ty);
    }
    
    /// @brief Methods to support type inquiry through isa, cast, and dyn_cast.
    static inline bool classof(const ConstantPlaceHolder *) { return true; }
    static bool classof(const Value *V) {
      return isa<ConstantExpr>(V) && 
             cast<ConstantExpr>(V)->getOpcode() == Instruction::UserOp1;
    }
    
    
    /// Provide fast operand accessors
    DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
  };
}


  // FIXME: can we inherit this from ConstantExpr?
template <>
struct OperandTraits<ConstantPlaceHolder> : FixedNumOperandTraits<1> {
};

DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ConstantPlaceHolder, Value)
}

void BitcodeReaderValueList::resize(unsigned Desired) {
  if (Desired > Capacity) {
    // Since we expect many values to come from the bitcode file we better
    // allocate the double amount, so that the array size grows exponentially
    // at each reallocation.  Also, add a small amount of 100 extra elements
    // each time, to reallocate less frequently when the array is still small.
    //
    Capacity = Desired * 2 + 100;
    Use *New = allocHungoffUses(Capacity);
    Use *Old = OperandList;
    unsigned Ops = getNumOperands();
    for (int i(Ops - 1); i >= 0; --i)
      New[i] = Old[i].get();
    OperandList = New;
    if (Old) Use::zap(Old, Old + Ops, true);
  }
}

Constant *BitcodeReaderValueList::getConstantFwdRef(unsigned Idx,
                                                    const Type *Ty) {
  if (Idx >= size()) {
    // Insert a bunch of null values.
    resize(Idx + 1);
    NumOperands = Idx+1;
  }

  if (Value *V = OperandList[Idx]) {
    assert(Ty == V->getType() && "Type mismatch in constant table!");
    return cast<Constant>(V);
  }

  // Create and return a placeholder, which will later be RAUW'd.
  Constant *C = new ConstantPlaceHolder(Ty);
  OperandList[Idx] = C;
  return C;
}

Value *BitcodeReaderValueList::getValueFwdRef(unsigned Idx, const Type *Ty) {
  if (Idx >= size()) {
    // Insert a bunch of null values.
    resize(Idx + 1);
    NumOperands = Idx+1;
  }
  
  if (Value *V = OperandList[Idx]) {
    assert((Ty == 0 || Ty == V->getType()) && "Type mismatch in value table!");
    return V;
  }
  
  // No type specified, must be invalid reference.
  if (Ty == 0) return 0;
  
  // Create and return a placeholder, which will later be RAUW'd.
  Value *V = new Argument(Ty);
  OperandList[Idx] = V;
  return V;
}

/// ResolveConstantForwardRefs - Once all constants are read, this method bulk
/// resolves any forward references.  The idea behind this is that we sometimes
/// get constants (such as large arrays) which reference *many* forward ref
/// constants.  Replacing each of these causes a lot of thrashing when
/// building/reuniquing the constant.  Instead of doing this, we look at all the
/// uses and rewrite all the place holders at once for any constant that uses
/// a placeholder.
void BitcodeReaderValueList::ResolveConstantForwardRefs() {
  // Sort the values by-pointer so that they are efficient to look up with a 
  // binary search.
  std::sort(ResolveConstants.begin(), ResolveConstants.end());
  
  SmallVector<Constant*, 64> NewOps;
  
  while (!ResolveConstants.empty()) {
    Value *RealVal = getOperand(ResolveConstants.back().second);
    Constant *Placeholder = ResolveConstants.back().first;
    ResolveConstants.pop_back();
    
    // Loop over all users of the placeholder, updating them to reference the
    // new value.  If they reference more than one placeholder, update them all
    // at once.
    while (!Placeholder->use_empty()) {
      Value::use_iterator UI = Placeholder->use_begin();
      
      // If the using object isn't uniqued, just update the operands.  This
      // handles instructions and initializers for global variables.
      if (!isa<Constant>(*UI) || isa<GlobalValue>(*UI)) {
        UI.getUse().set(RealVal);
        continue;
      }
      
      // Otherwise, we have a constant that uses the placeholder.  Replace that
      // constant with a new constant that has *all* placeholder uses updated.
      Constant *UserC = cast<Constant>(*UI);
      for (User::op_iterator I = UserC->op_begin(), E = UserC->op_end();
           I != E; ++I) {
        Value *NewOp;
        if (!isa<ConstantPlaceHolder>(*I)) {
          // Not a placeholder reference.
          NewOp = *I;
        } else if (*I == Placeholder) {
          // Common case is that it just references this one placeholder.
          NewOp = RealVal;
        } else {
          // Otherwise, look up the placeholder in ResolveConstants.
          ResolveConstantsTy::iterator It = 
            std::lower_bound(ResolveConstants.begin(), ResolveConstants.end(), 
                             std::pair<Constant*, unsigned>(cast<Constant>(*I),
                                                            0));
          assert(It != ResolveConstants.end() && It->first == *I);
          NewOp = this->getOperand(It->second);
        }

        NewOps.push_back(cast<Constant>(NewOp));
      }

      // Make the new constant.
      Constant *NewC;
      if (ConstantArray *UserCA = dyn_cast<ConstantArray>(UserC)) {
        NewC = ConstantArray::get(UserCA->getType(), &NewOps[0], NewOps.size());
      } else if (ConstantStruct *UserCS = dyn_cast<ConstantStruct>(UserC)) {
        NewC = ConstantStruct::get(&NewOps[0], NewOps.size(),
                                   UserCS->getType()->isPacked());
      } else if (isa<ConstantVector>(UserC)) {
        NewC = ConstantVector::get(&NewOps[0], NewOps.size());
      } else {
        // Must be a constant expression.
        NewC = cast<ConstantExpr>(UserC)->getWithOperands(&NewOps[0],
                                                          NewOps.size());
      }
      
      UserC->replaceAllUsesWith(NewC);
      UserC->destroyConstant();
      NewOps.clear();
    }
    
    delete Placeholder;
  }
}


const Type *BitcodeReader::getTypeByID(unsigned ID, bool isTypeTable) {
  // If the TypeID is in range, return it.
  if (ID < TypeList.size())
    return TypeList[ID].get();
  if (!isTypeTable) return 0;
  
  // The type table allows forward references.  Push as many Opaque types as
  // needed to get up to ID.
  while (TypeList.size() <= ID)
    TypeList.push_back(OpaqueType::get());
  return TypeList.back().get();
}

//===----------------------------------------------------------------------===//
//  Functions for parsing blocks from the bitcode file
//===----------------------------------------------------------------------===//

bool BitcodeReader::ParseAttributeBlock() {
  if (Stream.EnterSubBlock(bitc::PARAMATTR_BLOCK_ID))
    return Error("Malformed block record");
  
  if (!MAttributes.empty())
    return Error("Multiple PARAMATTR blocks found!");
  
  SmallVector<uint64_t, 64> Record;
  
  SmallVector<AttributeWithIndex, 8> Attrs;
  
  // Read all the records.
  while (1) {
    unsigned Code = Stream.ReadCode();
    if (Code == bitc::END_BLOCK) {
      if (Stream.ReadBlockEnd())
        return Error("Error at end of PARAMATTR block");
      return false;
    }
    
    if (Code == bitc::ENTER_SUBBLOCK) {
      // No known subblocks, always skip them.
      Stream.ReadSubBlockID();
      if (Stream.SkipBlock())
        return Error("Malformed block record");
      continue;
    }
    
    if (Code == bitc::DEFINE_ABBREV) {
      Stream.ReadAbbrevRecord();
      continue;
    }
    
    // Read a record.
    Record.clear();
    switch (Stream.ReadRecord(Code, Record)) {
    default:  // Default behavior: ignore.
      break;
    case bitc::PARAMATTR_CODE_ENTRY: { // ENTRY: [paramidx0, attr0, ...]
      if (Record.size() & 1)
        return Error("Invalid ENTRY record");

      // FIXME : Remove this autoupgrade code in LLVM 3.0.
      // If Function attributes are using index 0 then transfer them
      // to index ~0. Index 0 is used for return value attributes but used to be
      // used for function attributes.
      Attributes RetAttribute = Attribute::None;
      Attributes FnAttribute = Attribute::None;
      for (unsigned i = 0, e = Record.size(); i != e; i += 2) {
        // FIXME: remove in LLVM 3.0
        // The alignment is stored as a 16-bit raw value from bits 31--16.
        // We shift the bits above 31 down by 11 bits.

        unsigned Alignment = (Record[i+1] & (0xffffull << 16)) >> 16;
        if (Alignment && !isPowerOf2_32(Alignment))
          return Error("Alignment is not a power of two.");

        Attributes ReconstitutedAttr = Record[i+1] & 0xffff;
        if (Alignment)
          ReconstitutedAttr |= Attribute::constructAlignmentFromInt(Alignment);
        ReconstitutedAttr |= (Record[i+1] & (0xffffull << 32)) >> 11;
        Record[i+1] = ReconstitutedAttr;

        if (Record[i] == 0)
          RetAttribute = Record[i+1];
        else if (Record[i] == ~0U)
          FnAttribute = Record[i+1];
      }

      unsigned OldRetAttrs = (Attribute::NoUnwind|Attribute::NoReturn|
                              Attribute::ReadOnly|Attribute::ReadNone);
      
      if (FnAttribute == Attribute::None && RetAttribute != Attribute::None &&
          (RetAttribute & OldRetAttrs) != 0) {
        if (FnAttribute == Attribute::None) { // add a slot so they get added.
          Record.push_back(~0U);
          Record.push_back(0);
        }
        
        FnAttribute  |= RetAttribute & OldRetAttrs;
        RetAttribute &= ~OldRetAttrs;
      }

      for (unsigned i = 0, e = Record.size(); i != e; i += 2) {
        if (Record[i] == 0) {
          if (RetAttribute != Attribute::None)
            Attrs.push_back(AttributeWithIndex::get(0, RetAttribute));
        } else if (Record[i] == ~0U) {
          if (FnAttribute != Attribute::None)
            Attrs.push_back(AttributeWithIndex::get(~0U, FnAttribute));
        } else if (Record[i+1] != Attribute::None)
          Attrs.push_back(AttributeWithIndex::get(Record[i], Record[i+1]));
      }

      MAttributes.push_back(AttrListPtr::get(Attrs.begin(), Attrs.end()));
      Attrs.clear();
      break;
    }
    }
  }
}


bool BitcodeReader::ParseTypeTable() {
  if (Stream.EnterSubBlock(bitc::TYPE_BLOCK_ID))
    return Error("Malformed block record");
  
  if (!TypeList.empty())
    return Error("Multiple TYPE_BLOCKs found!");

  SmallVector<uint64_t, 64> Record;
  unsigned NumRecords = 0;

  // Read all the records for this type table.
  while (1) {
    unsigned Code = Stream.ReadCode();
    if (Code == bitc::END_BLOCK) {
      if (NumRecords != TypeList.size())
        return Error("Invalid type forward reference in TYPE_BLOCK");
      if (Stream.ReadBlockEnd())
        return Error("Error at end of type table block");
      return false;
    }
    
    if (Code == bitc::ENTER_SUBBLOCK) {
      // No known subblocks, always skip them.
      Stream.ReadSubBlockID();
      if (Stream.SkipBlock())
        return Error("Malformed block record");
      continue;
    }
    
    if (Code == bitc::DEFINE_ABBREV) {
      Stream.ReadAbbrevRecord();
      continue;
    }
    
    // Read a record.
    Record.clear();
    const Type *ResultTy = 0;
    switch (Stream.ReadRecord(Code, Record)) {
    default:  // Default behavior: unknown type.
      ResultTy = 0;
      break;
    case bitc::TYPE_CODE_NUMENTRY: // TYPE_CODE_NUMENTRY: [numentries]
      // TYPE_CODE_NUMENTRY contains a count of the number of types in the
      // type list.  This allows us to reserve space.
      if (Record.size() < 1)
        return Error("Invalid TYPE_CODE_NUMENTRY record");
      TypeList.reserve(Record[0]);
      continue;
    case bitc::TYPE_CODE_VOID:      // VOID
      ResultTy = Type::VoidTy;
      break;
    case bitc::TYPE_CODE_FLOAT:     // FLOAT
      ResultTy = Type::FloatTy;
      break;
    case bitc::TYPE_CODE_DOUBLE:    // DOUBLE
      ResultTy = Type::DoubleTy;
      break;
    case bitc::TYPE_CODE_X86_FP80:  // X86_FP80
      ResultTy = Type::X86_FP80Ty;
      break;
    case bitc::TYPE_CODE_FP128:     // FP128
      ResultTy = Type::FP128Ty;
      break;
    case bitc::TYPE_CODE_PPC_FP128: // PPC_FP128
      ResultTy = Type::PPC_FP128Ty;
      break;
    case bitc::TYPE_CODE_LABEL:     // LABEL
      ResultTy = Type::LabelTy;
      break;
    case bitc::TYPE_CODE_OPAQUE:    // OPAQUE
      ResultTy = 0;
      break;
    case bitc::TYPE_CODE_INTEGER:   // INTEGER: [width]
      if (Record.size() < 1)
        return Error("Invalid Integer type record");
      
      ResultTy = IntegerType::get(Record[0]);
      break;
    case bitc::TYPE_CODE_POINTER: { // POINTER: [pointee type] or 
                                    //          [pointee type, address space]
      if (Record.size() < 1)
        return Error("Invalid POINTER type record");
      unsigned AddressSpace = 0;
      if (Record.size() == 2)
        AddressSpace = Record[1];
      ResultTy = PointerType::get(getTypeByID(Record[0], true), AddressSpace);
      break;
    }
    case bitc::TYPE_CODE_FUNCTION: {
      // FIXME: attrid is dead, remove it in LLVM 3.0
      // FUNCTION: [vararg, attrid, retty, paramty x N]
      if (Record.size() < 3)
        return Error("Invalid FUNCTION type record");
      std::vector<const Type*> ArgTys;
      for (unsigned i = 3, e = Record.size(); i != e; ++i)
        ArgTys.push_back(getTypeByID(Record[i], true));
      
      ResultTy = FunctionType::get(getTypeByID(Record[2], true), ArgTys,
                                   Record[0]);
      break;
    }
    case bitc::TYPE_CODE_STRUCT: {  // STRUCT: [ispacked, eltty x N]
      if (Record.size() < 1)
        return Error("Invalid STRUCT type record");
      std::vector<const Type*> EltTys;
      for (unsigned i = 1, e = Record.size(); i != e; ++i)
        EltTys.push_back(getTypeByID(Record[i], true));
      ResultTy = StructType::get(EltTys, Record[0]);
      break;
    }
    case bitc::TYPE_CODE_ARRAY:     // ARRAY: [numelts, eltty]
      if (Record.size() < 2)
        return Error("Invalid ARRAY type record");
      ResultTy = ArrayType::get(getTypeByID(Record[1], true), Record[0]);
      break;
    case bitc::TYPE_CODE_VECTOR:    // VECTOR: [numelts, eltty]
      if (Record.size() < 2)
        return Error("Invalid VECTOR type record");
      ResultTy = VectorType::get(getTypeByID(Record[1], true), Record[0]);
      break;
    }
    
    if (NumRecords == TypeList.size()) {
      // If this is a new type slot, just append it.
      TypeList.push_back(ResultTy ? ResultTy : OpaqueType::get());
      ++NumRecords;
    } else if (ResultTy == 0) {
      // Otherwise, this was forward referenced, so an opaque type was created,
      // but the result type is actually just an opaque.  Leave the one we
      // created previously.
      ++NumRecords;
    } else {
      // Otherwise, this was forward referenced, so an opaque type was created.
      // Resolve the opaque type to the real type now.
      assert(NumRecords < TypeList.size() && "Typelist imbalance");
      const OpaqueType *OldTy = cast<OpaqueType>(TypeList[NumRecords++].get());
     
      // Don't directly push the new type on the Tab. Instead we want to replace
      // the opaque type we previously inserted with the new concrete value. The
      // refinement from the abstract (opaque) type to the new type causes all
      // uses of the abstract type to use the concrete type (NewTy). This will
      // also cause the opaque type to be deleted.
      const_cast<OpaqueType*>(OldTy)->refineAbstractTypeTo(ResultTy);
      
      // This should have replaced the old opaque type with the new type in the
      // value table... or with a preexisting type that was already in the
      // system.  Let's just make sure it did.
      assert(TypeList[NumRecords-1].get() != OldTy &&
             "refineAbstractType didn't work!");
    }
  }
}


bool BitcodeReader::ParseTypeSymbolTable() {
  if (Stream.EnterSubBlock(bitc::TYPE_SYMTAB_BLOCK_ID))
    return Error("Malformed block record");
  
  SmallVector<uint64_t, 64> Record;
  
  // Read all the records for this type table.
  std::string TypeName;
  while (1) {
    unsigned Code = Stream.ReadCode();
    if (Code == bitc::END_BLOCK) {
      if (Stream.ReadBlockEnd())
        return Error("Error at end of type symbol table block");
      return false;
    }
    
    if (Code == bitc::ENTER_SUBBLOCK) {
      // No known subblocks, always skip them.
      Stream.ReadSubBlockID();
      if (Stream.SkipBlock())
        return Error("Malformed block record");
      continue;
    }
    
    if (Code == bitc::DEFINE_ABBREV) {
      Stream.ReadAbbrevRecord();
      continue;
    }
    
    // Read a record.
    Record.clear();
    switch (Stream.ReadRecord(Code, Record)) {
    default:  // Default behavior: unknown type.
      break;
    case bitc::TST_CODE_ENTRY:    // TST_ENTRY: [typeid, namechar x N]
      if (ConvertToString(Record, 1, TypeName))
        return Error("Invalid TST_ENTRY record");
      unsigned TypeID = Record[0];
      if (TypeID >= TypeList.size())
        return Error("Invalid Type ID in TST_ENTRY record");

      TheModule->addTypeName(TypeName, TypeList[TypeID].get());
      TypeName.clear();
      break;
    }
  }
}

bool BitcodeReader::ParseValueSymbolTable() {
  if (Stream.EnterSubBlock(bitc::VALUE_SYMTAB_BLOCK_ID))
    return Error("Malformed block record");

  SmallVector<uint64_t, 64> Record;
  
  // Read all the records for this value table.
  SmallString<128> ValueName;
  while (1) {
    unsigned Code = Stream.ReadCode();
    if (Code == bitc::END_BLOCK) {
      if (Stream.ReadBlockEnd())
        return Error("Error at end of value symbol table block");
      return false;
    }    
    if (Code == bitc::ENTER_SUBBLOCK) {
      // No known subblocks, always skip them.
      Stream.ReadSubBlockID();
      if (Stream.SkipBlock())
        return Error("Malformed block record");
      continue;
    }
    
    if (Code == bitc::DEFINE_ABBREV) {
      Stream.ReadAbbrevRecord();
      continue;
    }
    
    // Read a record.
    Record.clear();
    switch (Stream.ReadRecord(Code, Record)) {
    default:  // Default behavior: unknown type.
      break;
    case bitc::VST_CODE_ENTRY: {  // VST_ENTRY: [valueid, namechar x N]
      if (ConvertToString(Record, 1, ValueName))
        return Error("Invalid TST_ENTRY record");
      unsigned ValueID = Record[0];
      if (ValueID >= ValueList.size())
        return Error("Invalid Value ID in VST_ENTRY record");
      Value *V = ValueList[ValueID];
      
      V->setName(&ValueName[0], ValueName.size());
      ValueName.clear();
      break;
    }
    case bitc::VST_CODE_BBENTRY: {
      if (ConvertToString(Record, 1, ValueName))
        return Error("Invalid VST_BBENTRY record");
      BasicBlock *BB = getBasicBlock(Record[0]);
      if (BB == 0)
        return Error("Invalid BB ID in VST_BBENTRY record");
      
      BB->setName(&ValueName[0], ValueName.size());
      ValueName.clear();
      break;
    }
    }
  }
}

/// DecodeSignRotatedValue - Decode a signed value stored with the sign bit in
/// the LSB for dense VBR encoding.
static uint64_t DecodeSignRotatedValue(uint64_t V) {
  if ((V & 1) == 0)
    return V >> 1;
  if (V != 1) 
    return -(V >> 1);
  // There is no such thing as -0 with integers.  "-0" really means MININT.
  return 1ULL << 63;
}

/// ResolveGlobalAndAliasInits - Resolve all of the initializers for global
/// values and aliases that we can.
bool BitcodeReader::ResolveGlobalAndAliasInits() {
  std::vector<std::pair<GlobalVariable*, unsigned> > GlobalInitWorklist;
  std::vector<std::pair<GlobalAlias*, unsigned> > AliasInitWorklist;
  
  GlobalInitWorklist.swap(GlobalInits);
  AliasInitWorklist.swap(AliasInits);

  while (!GlobalInitWorklist.empty()) {
    unsigned ValID = GlobalInitWorklist.back().second;
    if (ValID >= ValueList.size()) {
      // Not ready to resolve this yet, it requires something later in the file.
      GlobalInits.push_back(GlobalInitWorklist.back());
    } else {
      if (Constant *C = dyn_cast<Constant>(ValueList[ValID]))
        GlobalInitWorklist.back().first->setInitializer(C);
      else
        return Error("Global variable initializer is not a constant!");
    }
    GlobalInitWorklist.pop_back(); 
  }

  while (!AliasInitWorklist.empty()) {
    unsigned ValID = AliasInitWorklist.back().second;
    if (ValID >= ValueList.size()) {
      AliasInits.push_back(AliasInitWorklist.back());
    } else {
      if (Constant *C = dyn_cast<Constant>(ValueList[ValID]))
        AliasInitWorklist.back().first->setAliasee(C);
      else
        return Error("Alias initializer is not a constant!");
    }
    AliasInitWorklist.pop_back(); 
  }
  return false;
}


bool BitcodeReader::ParseConstants() {
  if (Stream.EnterSubBlock(bitc::CONSTANTS_BLOCK_ID))
    return Error("Malformed block record");

  SmallVector<uint64_t, 64> Record;
  
  // Read all the records for this value table.
  const Type *CurTy = Type::Int32Ty;
  unsigned NextCstNo = ValueList.size();
  while (1) {
    unsigned Code = Stream.ReadCode();
    if (Code == bitc::END_BLOCK)
      break;
    
    if (Code == bitc::ENTER_SUBBLOCK) {
      // No known subblocks, always skip them.
      Stream.ReadSubBlockID();
      if (Stream.SkipBlock())
        return Error("Malformed block record");
      continue;
    }
    
    if (Code == bitc::DEFINE_ABBREV) {
      Stream.ReadAbbrevRecord();
      continue;
    }
    
    // Read a record.
    Record.clear();
    Value *V = 0;
    switch (Stream.ReadRecord(Code, Record)) {
    default:  // Default behavior: unknown constant
    case bitc::CST_CODE_UNDEF:     // UNDEF
      V = UndefValue::get(CurTy);
      break;
    case bitc::CST_CODE_SETTYPE:   // SETTYPE: [typeid]
      if (Record.empty())
        return Error("Malformed CST_SETTYPE record");
      if (Record[0] >= TypeList.size())
        return Error("Invalid Type ID in CST_SETTYPE record");
      CurTy = TypeList[Record[0]];
      continue;  // Skip the ValueList manipulation.
    case bitc::CST_CODE_NULL:      // NULL
      V = Constant::getNullValue(CurTy);
      break;
    case bitc::CST_CODE_INTEGER:   // INTEGER: [intval]
      if (!isa<IntegerType>(CurTy) || Record.empty())
        return Error("Invalid CST_INTEGER record");
      V = ConstantInt::get(CurTy, DecodeSignRotatedValue(Record[0]));
      break;
    case bitc::CST_CODE_WIDE_INTEGER: {// WIDE_INTEGER: [n x intval]
      if (!isa<IntegerType>(CurTy) || Record.empty())
        return Error("Invalid WIDE_INTEGER record");
      
      unsigned NumWords = Record.size();
      SmallVector<uint64_t, 8> Words;
      Words.resize(NumWords);
      for (unsigned i = 0; i != NumWords; ++i)
        Words[i] = DecodeSignRotatedValue(Record[i]);
      V = ConstantInt::get(APInt(cast<IntegerType>(CurTy)->getBitWidth(),
                                 NumWords, &Words[0]));
      break;
    }
    case bitc::CST_CODE_FLOAT: {    // FLOAT: [fpval]
      if (Record.empty())
        return Error("Invalid FLOAT record");
      if (CurTy == Type::FloatTy)
        V = ConstantFP::get(APFloat(APInt(32, (uint32_t)Record[0])));
      else if (CurTy == Type::DoubleTy)
        V = ConstantFP::get(APFloat(APInt(64, Record[0])));
      else if (CurTy == Type::X86_FP80Ty)
        V = ConstantFP::get(APFloat(APInt(80, 2, &Record[0])));
      else if (CurTy == Type::FP128Ty)
        V = ConstantFP::get(APFloat(APInt(128, 2, &Record[0]), true));
      else if (CurTy == Type::PPC_FP128Ty)
        V = ConstantFP::get(APFloat(APInt(128, 2, &Record[0])));
      else
        V = UndefValue::get(CurTy);
      break;
    }
      
    case bitc::CST_CODE_AGGREGATE: {// AGGREGATE: [n x value number]
      if (Record.empty())
        return Error("Invalid CST_AGGREGATE record");
      
      unsigned Size = Record.size();
      std::vector<Constant*> Elts;
      
      if (const StructType *STy = dyn_cast<StructType>(CurTy)) {
        for (unsigned i = 0; i != Size; ++i)
          Elts.push_back(ValueList.getConstantFwdRef(Record[i],
                                                     STy->getElementType(i)));
        V = ConstantStruct::get(STy, Elts);
      } else if (const ArrayType *ATy = dyn_cast<ArrayType>(CurTy)) {
        const Type *EltTy = ATy->getElementType();
        for (unsigned i = 0; i != Size; ++i)
          Elts.push_back(ValueList.getConstantFwdRef(Record[i], EltTy));
        V = ConstantArray::get(ATy, Elts);
      } else if (const VectorType *VTy = dyn_cast<VectorType>(CurTy)) {
        const Type *EltTy = VTy->getElementType();
        for (unsigned i = 0; i != Size; ++i)
          Elts.push_back(ValueList.getConstantFwdRef(Record[i], EltTy));
        V = ConstantVector::get(Elts);
      } else {
        V = UndefValue::get(CurTy);
      }
      break;
    }
    case bitc::CST_CODE_STRING: { // STRING: [values]
      if (Record.empty())
        return Error("Invalid CST_AGGREGATE record");

      const ArrayType *ATy = cast<ArrayType>(CurTy);
      const Type *EltTy = ATy->getElementType();
      
      unsigned Size = Record.size();
      std::vector<Constant*> Elts;
      for (unsigned i = 0; i != Size; ++i)
        Elts.push_back(ConstantInt::get(EltTy, Record[i]));
      V = ConstantArray::get(ATy, Elts);
      break;
    }
    case bitc::CST_CODE_CSTRING: { // CSTRING: [values]
      if (Record.empty())
        return Error("Invalid CST_AGGREGATE record");
      
      const ArrayType *ATy = cast<ArrayType>(CurTy);
      const Type *EltTy = ATy->getElementType();
      
      unsigned Size = Record.size();
      std::vector<Constant*> Elts;
      for (unsigned i = 0; i != Size; ++i)
        Elts.push_back(ConstantInt::get(EltTy, Record[i]));
      Elts.push_back(Constant::getNullValue(EltTy));
      V = ConstantArray::get(ATy, Elts);
      break;
    }
    case bitc::CST_CODE_CE_BINOP: {  // CE_BINOP: [opcode, opval, opval]
      if (Record.size() < 3) return Error("Invalid CE_BINOP record");
      int Opc = GetDecodedBinaryOpcode(Record[0], CurTy);
      if (Opc < 0) {
        V = UndefValue::get(CurTy);  // Unknown binop.
      } else {
        Constant *LHS = ValueList.getConstantFwdRef(Record[1], CurTy);
        Constant *RHS = ValueList.getConstantFwdRef(Record[2], CurTy);
        V = ConstantExpr::get(Opc, LHS, RHS);
      }
      break;
    }  
    case bitc::CST_CODE_CE_CAST: {  // CE_CAST: [opcode, opty, opval]
      if (Record.size() < 3) return Error("Invalid CE_CAST record");
      int Opc = GetDecodedCastOpcode(Record[0]);
      if (Opc < 0) {
        V = UndefValue::get(CurTy);  // Unknown cast.
      } else {
        const Type *OpTy = getTypeByID(Record[1]);
        if (!OpTy) return Error("Invalid CE_CAST record");
        Constant *Op = ValueList.getConstantFwdRef(Record[2], OpTy);
        V = ConstantExpr::getCast(Opc, Op, CurTy);
      }
      break;
    }  
    case bitc::CST_CODE_CE_GEP: {  // CE_GEP:        [n x operands]
      if (Record.size() & 1) return Error("Invalid CE_GEP record");
      SmallVector<Constant*, 16> Elts;
      for<