; fib_simple.asm. Compute Fibonnaci numbers using a loop
; only using registers
; this assumes n>2

; initialize some values into registers
; this program assumes r0 = 0
; r1	current_result
; r2	fib(n-1)
; r3	fib(n-2)
; r4	n - how many fib numbers will we calculate?

	lar r31, loop	; put the address of loop label in r31
	addi r1, r0, 0	; initialize current_result to 0
	addi r2, r0, 1	; initialize fib(n-1) to fib(1) = 1
	addi r3, r0, 0	; initialize fib(n-2) to fib(0) = 0
	addi r4, r0, 5	; initialize number of iterations desired to 5 
				; We want to calculate 5 fib numbers beyond Fib(0), Fib(1)... so Fib(6)
loop:	add r1, r2, r3	; compute result and store in r1
	add r3, r0, r2	; set fib(n-2) register to hold fib(n-1)
	add r2, r0, r1	; set fib(n-1) register to hold current_result
	addi r4, r4, -1	; subtract 1 from the loop counter
	brnz r31, r4		; if loop counter is still not zero loop again
	
stop	; stop executing