Move data from NIOS to hardware and then back to NIOS

For loops are synthesizable but may give different results that what you expect. In this case it would create 8 multipliers and 8 adders that would all work in parallel to do the operation in one clock cycle. If you want to have only one multiplier and do the operation in 8 cycles instead, then yes you need to get rid of the loop and do a clocked process.