lw	0	8	neg1	load reg8 with -1
	lw	0	5	four	load reg5 with 4
	sub	5	8	6	reg6 <- reg5 - reg8 (reg6 <- 5)
	addi	5	3	4	reg3 <- reg5 + 4  (reg3 <- 8)
	andi	5	2	240	reg2 <- reg5 & 0xf0  (reg2 <- 0)
loop	add	5	8	5	reg5 <- reg5 + reg8 (reg5 decremented)
	beqz	5	done		if reg5=0, go to done
	j	loop
	noop				(never executed)
done	halt
neg1	.fill	-1
four	.fill	4