C++ TargetData::getTypeSize方法代码示例

// Peephole Malloc instructions: we take a look at the use chain of the
// malloc instruction, and try to find out if the following conditions hold:
//   1. The malloc is of the form: 'malloc [sbyte], uint <constant>'
//   2. The only users of the malloc are cast & add instructions
//   3. Of the cast instructions, there is only one destination pointer type
//      [RTy] where the size of the pointed to object is equal to the number
//      of bytes allocated.
//
// If these conditions hold, we convert the malloc to allocate an [RTy]
// element.  TODO: This comment is out of date WRT arrays
//
static bool MallocConvertibleToType(MallocInst *MI, const Type *Ty,
                                    ValueTypeCache &CTMap,
                                    const TargetData &TD) {
  if (!isa<PointerType>(Ty)) return false;   // Malloc always returns pointers

  // Deal with the type to allocate, not the pointer type...
  Ty = cast<PointerType>(Ty)->getElementType();
  if (!Ty->isSized()) return false;      // Can only alloc something with a size

  // Analyze the number of bytes allocated...
  ExprType Expr = ClassifyExpr(MI->getArraySize());

  // Get information about the base datatype being allocated, before & after
  int ReqTypeSize = TD.getTypeSize(Ty);
  if (ReqTypeSize == 0) return false;
  unsigned OldTypeSize = TD.getTypeSize(MI->getType()->getElementType());

  // Must have a scale or offset to analyze it...
  if (!Expr.Offset && !Expr.Scale && OldTypeSize == 1) return false;

  // Get the offset and scale of the allocation...
  int64_t OffsetVal = Expr.Offset ? getConstantValue(Expr.Offset) : 0;
  int64_t ScaleVal = Expr.Scale ? getConstantValue(Expr.Scale) :(Expr.Var != 0);

  // The old type might not be of unit size, take old size into consideration
  // here...
  int64_t Offset = OffsetVal * OldTypeSize;
  int64_t Scale  = ScaleVal  * OldTypeSize;
  
  // In order to be successful, both the scale and the offset must be a multiple
  // of the requested data type's size.
  //
  if (Offset/ReqTypeSize*ReqTypeSize != Offset ||
      Scale/ReqTypeSize*ReqTypeSize != Scale)
    return false;   // Nope.

  return true;
}

/// IsConstantOffsetFromGlobal - If this constant is actually a constant offset
/// from a global, return the global and the constant.  Because of
/// constantexprs, this function is recursive.
static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
                                       int64_t &Offset, const TargetData &TD) {
  // Trivial case, constant is the global.
  if ((GV = dyn_cast<GlobalValue>(C))) {
    Offset = 0;
    return true;
  }
  
  // Otherwise, if this isn't a constant expr, bail out.
  ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
  if (!CE) return false;
  
  // Look through ptr->int and ptr->ptr casts.
  if (CE->getOpcode() == Instruction::PtrToInt ||
      CE->getOpcode() == Instruction::BitCast)
    return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD);
  
  // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)    
  if (CE->getOpcode() == Instruction::GetElementPtr) {
    // Cannot compute this if the element type of the pointer is missing size
    // info.
    if (!cast<PointerType>(CE->getOperand(0)->getType())->getElementType()->isSized())
      return false;
    
    // If the base isn't a global+constant, we aren't either.
    if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD))
      return false;
    
    // Otherwise, add any offset that our operands provide.
    gep_type_iterator GTI = gep_type_begin(CE);
    for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i, ++GTI) {
      ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(i));
      if (!CI) return false;  // Index isn't a simple constant?
      if (CI->getZExtValue() == 0) continue;  // Not adding anything.
      
      if (const StructType *ST = dyn_cast<StructType>(*GTI)) {
        // N = N + Offset
        Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue());
      } else {
        const SequentialType *SQT = cast<SequentialType>(*GTI);
        Offset += TD.getTypeSize(SQT->getElementType())*CI->getSExtValue();
      }
    }
    return true;
  }
  
  return false;
}

//.........这里部分代码省略.........
      const Type *ValTy = cast<PointerType>(NewTy)->getElementType();

      Value *SrcPtr = NewVal;

      if (isa<StructType>(ValTy)) {
        std::vector<Value*> Indices;
        Indices.push_back(Constant::getNullValue(Type::UIntTy));

        unsigned Offset = 0;
        ValTy = getStructOffsetType(ValTy, Offset, Indices, TD, false);

        assert(Offset == 0 && ValTy);

        // Insert the GEP instruction before this store.
        SrcPtr = new GetElementPtrInst(SrcPtr, Indices,
                                       SrcPtr->getName()+".idx", I);
      }

      Res = new StoreInst(Constant::getNullValue(ValTy), SrcPtr);
      VMC.ExprMap[I] = Res;
      Res->setOperand(0, ConvertExpressionToType(I->getOperand(0),
                                                 ValTy, VMC, TD));
    }
    break;
  }


  case Instruction::GetElementPtr: {
    // Convert a one index getelementptr into just about anything that is
    // desired.
    //
    BasicBlock::iterator It = I;
    const Type *OldElTy = cast<PointerType>(I->getType())->getElementType();
    unsigned DataSize = TD.getTypeSize(OldElTy);
    Value *Index = I->getOperand(1);

    if (DataSize != 1) {
      // Insert a multiply of the old element type is not a unit size...
      Value *CST;
      if (Index->getType()->isSigned())
        CST = ConstantSInt::get(Index->getType(), DataSize);
      else
        CST = ConstantUInt::get(Index->getType(), DataSize);

      Index = BinaryOperator::create(Instruction::Mul, Index, CST, "scale", It);
    }

    // Perform the conversion now...
    //
    std::vector<Value*> Indices;
    const Type *ElTy = ConvertibleToGEP(NewVal->getType(),Index,Indices,TD,&It);
    assert(ElTy != 0 && "GEP Conversion Failure!");
    Res = new GetElementPtrInst(NewVal, Indices, Name);
    assert(Res->getType() == PointerType::get(ElTy) &&
           "ConvertibleToGet failed!");
  }
#if 0
    if (I->getType() == PointerType::get(Type::SByteTy)) {
      // Convert a getelementptr sbyte * %reg111, uint 16 freely back to
      // anything that is a pointer type...
      //
      BasicBlock::iterator It = I;
    
      // Check to see if the second argument is an expression that can
      // be converted to the appropriate size... if so, allow it.
      //

//.........这里部分代码省略.........
  }
  case Instruction::Shr:
    if (Ty->isSigned() != V->getType()->isSigned()) return false;
    // FALL THROUGH
  case Instruction::Shl:
    if (I->getOperand(1) == V) return false;  // Cannot change shift amount type
    if (!Ty->isInteger()) return false;
    return ValueConvertibleToType(I, Ty, CTMap, TD);

  case Instruction::Free:
    assert(I->getOperand(0) == V);
    return isa<PointerType>(Ty);    // Free can free any pointer type!

  case Instruction::Load:
    // Cannot convert the types of any subscripts...
    if (I->getOperand(0) != V) return false;

    if (const PointerType *PT = dyn_cast<PointerType>(Ty)) {
      LoadInst *LI = cast<LoadInst>(I);
      
      const Type *LoadedTy = PT->getElementType();

      // They could be loading the first element of a composite type...
      if (const CompositeType *CT = dyn_cast<CompositeType>(LoadedTy)) {
        unsigned Offset = 0;     // No offset, get first leaf.
        std::vector<Value*> Indices;  // Discarded...
        LoadedTy = getStructOffsetType(CT, Offset, Indices, TD, false);
        assert(Offset == 0 && "Offset changed from zero???");
      }

      if (!LoadedTy->isFirstClassType())
        return false;

      if (TD.getTypeSize(LoadedTy) != TD.getTypeSize(LI->getType()))
        return false;

      return ValueConvertibleToType(LI, LoadedTy, CTMap, TD);
    }
    return false;

  case Instruction::Store: {
    StoreInst *SI = cast<StoreInst>(I);

    if (V == I->getOperand(0)) {
      ValueTypeCache::iterator CTMI = CTMap.find(I->getOperand(1));
      if (CTMI != CTMap.end()) {   // Operand #1 is in the table already?
        // If so, check to see if it's Ty*, or, more importantly, if it is a
        // pointer to a structure where the first element is a Ty... this code
        // is necessary because we might be trying to change the source and
        // destination type of the store (they might be related) and the dest
        // pointer type might be a pointer to structure.  Below we allow pointer
        // to structures where the 0th element is compatible with the value,
        // now we have to support the symmetrical part of this.
        //
        const Type *ElTy = cast<PointerType>(CTMI->second)->getElementType();

        // Already a pointer to what we want?  Trivially accept...
        if (ElTy == Ty) return true;

        // Tricky case now, if the destination is a pointer to structure,
        // obviously the source is not allowed to be a structure (cannot copy
        // a whole structure at a time), so the level raiser must be trying to
        // store into the first field.  Check for this and allow it now:
        //
        if (const StructType *SElTy = dyn_cast<StructType>(ElTy)) {
          unsigned Offset = 0;

//.........这里部分代码省略.........
    // 
    GetElementPtrInst *GEP = cast<GetElementPtrInst>(I);
    const PointerType *PTy = dyn_cast<PointerType>(Ty);
    if (!PTy) return false;  // GEP must always return a pointer...
    const Type *PVTy = PTy->getElementType();

    // Check to see if there are zero elements that we can remove from the
    // index array.  If there are, check to see if removing them causes us to
    // get to the right type...
    //
    std::vector<Value*> Indices(GEP->idx_begin(), GEP->idx_end());
    const Type *BaseType = GEP->getPointerOperand()->getType();
    const Type *ElTy = 0;

    while (!Indices.empty() &&
           Indices.back() == Constant::getNullValue(Indices.back()->getType())){
      Indices.pop_back();
      ElTy = GetElementPtrInst::getIndexedType(BaseType, Indices, true);
      if (ElTy == PVTy)
        break;  // Found a match!!
      ElTy = 0;
    }

    if (ElTy) break;   // Found a number of zeros we can strip off!

    // Otherwise, we can convert a GEP from one form to the other iff the
    // current gep is of the form 'getelementptr sbyte*, long N
    // and we could convert this to an appropriate GEP for the new type.
    //
    if (GEP->getNumOperands() == 2 &&
        GEP->getType() == PointerType::get(Type::SByteTy)) {

      // Do not Check to see if our incoming pointer can be converted
      // to be a ptr to an array of the right type... because in more cases than
      // not, it is simply not analyzable because of pointer/array
      // discrepancies.  To fix this, we will insert a cast before the GEP.
      //

      // Check to see if 'N' is an expression that can be converted to
      // the appropriate size... if so, allow it.
      //
      std::vector<Value*> Indices;
      const Type *ElTy = ConvertibleToGEP(PTy, I->getOperand(1), Indices, TD);
      if (ElTy == PVTy) {
        if (!ExpressionConvertibleToType(I->getOperand(0),
                                         PointerType::get(ElTy), CTMap, TD))
          return false;  // Can't continue, ExConToTy might have polluted set!
        break;
      }
    }

    // Otherwise, it could be that we have something like this:
    //     getelementptr [[sbyte] *] * %reg115, long %reg138    ; [sbyte]**
    // and want to convert it into something like this:
    //     getelemenptr [[int] *] * %reg115, long %reg138      ; [int]**
    //
    if (GEP->getNumOperands() == 2 && 
        PTy->getElementType()->isSized() &&
        TD.getTypeSize(PTy->getElementType()) == 
        TD.getTypeSize(GEP->getType()->getElementType())) {
      const PointerType *NewSrcTy = PointerType::get(PVTy);
      if (!ExpressionConvertibleToType(I->getOperand(0), NewSrcTy, CTMap, TD))
        return false;
      break;
    }

    return false;   // No match, maybe next time.
  }

  case Instruction::Call: {
    if (isa<Function>(I->getOperand(0)))
      return false;  // Don't even try to change direct calls.

    // If this is a function pointer, we can convert the return type if we can
    // convert the source function pointer.
    //
    const PointerType *PT = cast<PointerType>(I->getOperand(0)->getType());
    const FunctionType *FT = cast<FunctionType>(PT->getElementType());
    std::vector<const Type *> ArgTys(FT->param_begin(), FT->param_end());
    const FunctionType *NewTy =
      FunctionType::get(Ty, ArgTys, FT->isVarArg());
    if (!ExpressionConvertibleToType(I->getOperand(0),
                                     PointerType::get(NewTy), CTMap, TD))
      return false;
    break;
  }
  default:
    return false;
  }

  // Expressions are only convertible if all of the users of the expression can
  // have this value converted.  This makes use of the map to avoid infinite
  // recursion.
  //
  for (Value::use_iterator It = I->use_begin(), E = I->use_end(); It != E; ++It)
    if (!OperandConvertibleToType(*It, I, Ty, CTMap, TD))
      return false;

  return true;
}