gistfile1.asm

.text
.global main

; r0 = accumulator
; r1 = first
; r2 = second
; r3 = step
main:
    mov r1, #0
    mov r2, #1
    mov r3, #0
    b check
loop:
    cmp r3, #1
    blt lt_one
    add r0, r1, r2  ; accumulator = first + second
    mov r1, r2
    mov r2, r0
    b increment
lt_one:
    mov r0, r3      ; accumulator = step
increment:
    add r3, #1      ; step += 1
check:
    cmp r3, #10     ; 10 = N in f(N)
    blt loop
    bx lr