;;  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
	sp 4
	link 3
	n 1
	retv 2
	t1 5
	t3 6

.a 0
.c
:main	ld sp #200  ;; init sp
	ld n #6
	jal link fib  ;; call fib 3
	st b retv
	trap stop r0

:fib	st @1 sp link  ;; push link
	st @2 sp t1  ;; push t1
	st @3 sp t3  ;; push t3
	add sp sp #3

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