li $a0, 6
jal fib
move $a0, $v0
li $v0, 1
syscall
li $v0, 10
syscall

fib:
# computes fib(n), provided n > 0
# $a0 holds n
# $ra holds the return address
# $v0 will hold the computed value
# $v0 is also used for F_k
# $t0 holds k
# $t1 holds F_{k-1}

li $v0, 1
li $t0, 1
li $t1, 0

loop:
beq $t0, $a0, end
addi $t0, $t0, 1
move $t2, $v0
add $v0, $v0, $t1
move $t1, $t2
j loop

end:
jr $ra