Specifically, I think the "sltu" (set if less than, unsigned) instruction is useful for carries. When you add two unsigned integers, the result is smaller than

Specifically, I think the "sltu" (set if less than, unsigned) instruction is useful for carries. When you add two unsigned integers, the result is smaller than the inputs if and only if an overflow occurred. ; a1:a0 * a2 --> a5:a4:a3 ; using t0 as temp reg mulhu a5, a1, a2 mulu a4, a1, a2 mulhu t0, a0, a2 mulu a3, a0, a2 add a4, a4, t0 ; carry a 1 or a 0, overwriting t0 sltu t0, a4, t0 add a5, a5, t0 (edit: switched a1 and a0 for consistency)