MOD command has no problem. If you use ROTL and ROTR, check the parameter first to make sure the value being shift is not zero and position to be shift is not zero, then it will have no problem. Also, if your just do:
ROTL RAM1 RAM2 RAM1
then does not matter if first or 2nd parameter zero will not have problem. If you do
ROTL RAM1 RAM2 RAM3
Then RAM3 may not have correct value, if RAM1 or RAM2 has zero in it. You will need to check first 2 parameters.
The current shipping firmware does the check internally and put 3rd parameter with correct value now. Think about it, maybe not checking and just let zero being rotated, or rotate zero position, that maybe use less CPU than checking.