5.6 Exercise 5.6

In the Fibonacci program earlier, afterfib-n-1 ran the following instructions in order:

(restore continue)

(assign n (op -) (reg n) (const 2))

(save continue)

Immediately popping a value off of the stack into the continue register, computing a value entirely unrelated to it, and then pushing the value in the continue register back onto the stack is obviously an unnecessary restore/save pair. Both of these instructions can be deleted without consequence.