Fibonacci Iterativo ASM

.data
    n:  .word   0
    res:    .word   0
.text
    main:   lw $4, n($0)
        jal fib
        sw $2, res($0)
        li $2, 10
        syscall

    fib:    add $16, $0, $0
        addi $17, $0, 1
    for:    blt $8, $4, less
        add $2, $0, $16
        jr $31
    less:   add $9, $0, $17
        add $17, $16, $17
        add $16, $0, $9
        addi $8, $8, 1
        j for