;;; Name: Shreyas Vaidya
;;; UID: 115415522
;;; Directory ID: shreyasv

;;; Implementation that computes a palindrome with a given array

    .global is_palindrome       ; exposes is_palindrome as a label
is_palindrome:                  ; the next instruction starts is_palindrome()
        ;; Add your code here
    mov r27, r25        ; copies argument to X pointer
    mov r26, r24
    push r30
    push r31
    mov r31, r25        ; copies argument to Z pointer
    mov r30, r24
    clr r20
    clr r21
    clr r22
    clr r23
    push r26
    push r27
    push r30
    push r31
    call strlen
    mov r20, r24        ; r20 now contains string length
    pop r31
    pop r30
    pop r27
    pop r26
    add r30, r16

2:
    ld r16, -Z      ; gets Z to the end of the string
    subi r20, 1
    add r26, r20

3:  ld r22, X+      ; loops through data-1/2 times & checks
    lsr r20         ; divides r14 by 2

6:  ldi r18, 0
    cp r16, r22
    brne 5f
    cp r20, r18
    breq 4f
    add r18, 1
    jmp 6b

4:  ldi r24, 1
    clr r25
    jmp 1f

5:  ldi r24, 0
    clr r25
    jmp 1f

1:
    pop r31
    pop r30
    ret