gcd.asm

; MIPS - Euclidean Recursive
;
; @author       Mr. Polywhirl
; @description  The following program is an implementation of the Euclidean
;               Greatest Common Divisor algorithm C function below.
;
;               int gcd_recursive(int a, int b) {
;                   if (b == 0)
;                       return a;
;                    else
;                        return gcd_recursive(b, a % b);
;                }
;
; @registers    $t0 - Stores an integer value for 'a'
;               $t1 - Stores an integer value for 'b'
;               $t2 - The remainder from the division of a / b

        .data                   ;; DECLARATIONS
ans:    .word 0x0000            ; Answer place holder
a:      .word 0x00000162        ; a = 354
b:      .word 0x00000084        ; b = 132
        .text                   ;; INSTRUCTIONS
main:   lwu   $t1, b($zero)     ; load b into $t1
        lwu   $t0, a($zero)     ; load a into $t0
gcd:    beqz  $t1, res          ; if b == 0, jump to result
        div   $t0, $t1          ; a / b
        mfhi  $t2               ; Retrieve and store remainder from HI
        or    $t0, $zero, $t1   ; a = b
        or    $t1, $zero, $t2   ; b = remainder (a % b)
        bnez  $t1, gcd          ; if b != 0
res:    sd    $t0, ans($zero)   ; Store result to memory: 6
exit:   halt                    ; Exit program.