This possible future instruction uses some of the multiplier's lookup table space. This table has 8 bits of address and 32 bits of data and must be initialised by MULI.
One important application is to compute a CRC (Cyclic Redundancy Check) byte from the operand. The table can be initialised to compute CRC16, CRC32 or any variation. Eventually, the result can be combined by XOR with a second operand (when any ?).
It's highly implementation dependent.