;;  example of recursive function call
;;  fib n
;;    if n < 2 return n
;;    else return fib(n - 1) + fib(n - 2)

;;  many local variables are required
;;  t3 = n
;;  t1 = fib t3 - 1
;;  retv = fib t3 - 2
;;  retv = retv + t1

;;  r1 = input n, r2 = output retv,
;;  r3 = link, r4 = sp,
;;  r5 = t1, r6 = t3, 

;;  main() { b = fib(6) }

.s
	b 100

.a 0
.c
:main	ld r4 #200  ;; init sp
	ld r1 #6
	jal r3 fib  ;; call fib 3
	st b r2
	trap stop r0

:fib	st @1 r4 r3  ;; push link
	st @2 r4 r5  ;; push t1
	st @3 r4 r6  ;; push t3
	add r4 r4 #3

	sub r0 r1 #2 ;; n < 2
	jmp GE else
:then	or r2 r1 r0 ;; retv = n
	jmp always ret
:else	or r6 r1 r0 ;; t3 = n
	sub r1 r6 #1 ;; n - 1
	jal r3 fib
	or r5 r2 r0 ;; t1 = fib n - 1
	sub r1 r6 #2 ;; n - 2
	jal r3 fib  ;; retv = fib n - 2
	add r2 r2 r5
	
	;; restore locals
:ret	ld r6 @0 r4
	ld r5 @-1 r4
	ld r3 @-2 r4
	sub r4 r4 #3
	jr r3
.e