Using the rem instruction

Leap
Leap in MIPS Assembly 
## Registers

# | Register | Usage     | Type    | Description                                      |
# | -------- | --------- | ------- | ------------------------------------------------ |
# | `$a0`    | input     | integer | year to check                                    |
# | `$v0`    | output    | boolean | input is leap year (`0` = `false`, `1` = `true`) |
# | `$t0-9`  | temporary | any     | used for temporary storage                       |

.globl is_leap_year

is_leap_year:
        li      $v0, 0

        rem     $t0, $a0, 4
        bnez    $t0, end

        rem     $t0, $a0, 100
        bnez    $t0, set_leap

        rem     $t0, $a0, 400
        bnez    $t0, end

set_leap:
        li      $v0, 1
end:
        jr      $ra

Equivalent C code:

int is_leap_year(int year) {
    return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
}

This approach uses the rem instruction to compute the remainder of divisions. Since this instruction computes the remainder and stores it in a register directly, it is more concise than using div.

6th Nov 2024 · Found it useful?

Other Approaches to Leap in MIPS Assembly

Other ways our community solved this exercise
is_leap_year:
        li      $v0, 0

        li      $t0, 4
        div     $a0, $t0
        mfhi    $t0
        bnez    $t0, end
Using the div instruction

Use the div instruction to get a division's remainder. 

.macro if_divisible_by($divisor, $then_jump)
        li      $t0, $divisor
        div     $a0, $t0
        mfhi    $t0
        beqz    $t0, $then_jump
.end_macro
Using a "divisible by" macro

Define a macro to avoid repeating code too often. 

is_leap_year:
        li      $v0, 0

        andi    $t0, $a0, 3
        bnez    $t0, end
Using the andi instruction

Use the andi instruction to determine if a number is divisible by 4.