Multiplier and Divider

In that case, all you need for a single overflow but is to or the top 32 bits of the output of the multuplier (because you connect the least significant 32 bits of the multiplier to your output) for your unsigned ALU.

for the signed, the output becomes and overflow/underflow. first check is to see if the top 32 bit are all 1 or all 0. If this fails, there is an overflow (in the case of MSB = '1') or underflow (MSB = '0'). Then you compare MSB with bit 31. MSB = '1' and bit31 = '0' means underflow, MSB = '0' and bit31 = '1' mean overflow. You can of course combine all this for a single bit "error".