private CPUState _mul(Instruction instruction)
{
_newProgramCounter++;
if (instruction.SecondRegister.HasValue)
{
_alu.Multiply(Registers[instruction.FirstRegister.Value],
Registers[instruction.SecondRegister.Value]);
Registers[instruction.FirstRegister.Value] =
_alu.AluResult;
return(new CPUState(Registers, instruction, _programCounter));
}
else if (instruction.FirstConstant.HasValue)
{
_alu.Multiply(Registers[instruction.FirstRegister.Value],
instruction.FirstConstant.Value);
Registers[instruction.FirstRegister.Value] =
_alu.AluResult;
return(new CPUState(Registers, instruction, _programCounter));
}
else
{
throw new InvalidOperationException("No corresponding number of operands given.");
}
}