static ILExpression DivideBySize(ILExpression expr, TypeReference type)
{
expr = UnwrapIntPtrCast(expr);
ILExpression sizeOfExpression;
switch (TypeAnalysis.GetInformationAmount(type))
{
case 1:
case 8:
sizeOfExpression = new ILExpression(ILCode.Ldc_I4, 1);
break;
case 16:
sizeOfExpression = new ILExpression(ILCode.Ldc_I4, 2);
break;
case 32:
sizeOfExpression = new ILExpression(ILCode.Ldc_I4, 4);
break;
case 64:
sizeOfExpression = new ILExpression(ILCode.Ldc_I4, 8);
break;
default:
sizeOfExpression = new ILExpression(ILCode.Sizeof, type);
break;
}
if (expr.Code == ILCode.Mul || expr.Code == ILCode.Mul_Ovf || expr.Code == ILCode.Mul_Ovf_Un)
{
ILExpression mulArg = expr.Arguments[1];
if (mulArg.Code == sizeOfExpression.Code && sizeOfExpression.Operand.Equals(mulArg.Operand))
{
return(UnwrapIntPtrCast(expr.Arguments[0]));
}
}
if (expr.Code == sizeOfExpression.Code)
{
if (sizeOfExpression.Operand.Equals(expr.Operand))
{
return(new ILExpression(ILCode.Ldc_I4, 1));
}
if (expr.Code == ILCode.Ldc_I4)
{
int offsetInBytes = (int)expr.Operand;
int elementSize = (int)sizeOfExpression.Operand;
int offsetInElements = offsetInBytes / elementSize;
// ensure integer division
if (offsetInElements * elementSize == offsetInBytes)
{
expr.Operand = offsetInElements;
return(expr);
}
}
}
return(new ILExpression(ILCode.Div_Un, null, expr, sizeOfExpression));
}
