MIPS vs Nios II instruction

I suspect the easiest way to do this is to have a additional register set, and use the 'previous' register set for additional workspace. You could designate the alternate r2 and r3 as %lo and %hi.

Convert the multiply to write it's result into r1 (asm temp - available as a scratch register), then use wrprs to save it in the alternate set.

Divide is a bit more tricky since the mips instruction generates the quotient and remainder. But you can still use r1 to generate both results.

Reads of %LO and %HI are then rdprs.