I wrote this code to check if something is a prime number or not.
.data
is_prime: .asciiz "--Prime--"
not_prime: .asciiz "--No prime--"
element: .word 2
.text
main:
#importeer prime messages
la $t3, is_prime
la $t4, not_prime
lw $t1, element
# input variabele n
li $v0, 5
syscall
move $t0, $v0
if_loop:
beq $t0, 1, prime_true
bgt $t0, 1, prime_check
prime_check:
beq $t0, $t1, prime_true
div $t1, $t0
mfhi $t6
beq $t6, 0, prime_false
addi $t0, $t0, 1
prime_true:
li $v0, 4
move $a0, $t3
syscall
j exit
prime_false:
li $v0, 4
move $a0, $t4
syscall
j exit
exit:
However, every time I run it with any input like 3, 4, 5 or 6 it gives --Prime-- when for 4 and 6 it shouldn't.
My MIPS is quite rusty, but as I understand your code, the value you want to check is in $t0 and the incrementing divisor is in $t1. So your code has the following issues
div $t1, $t0 calculates $t1 / $t0. You want to calculate $t0 / $t1, so switch the parameters (as you already noticed yourself)
you are lacking a j if_loop somewhere -- probably best after addi -- for your loop to continue after you checked the remainder of the division. So for any odd number your code will just continue running straight ahead and print out "--Prime--"
addi $t0, $t0, 1 is incrementing the value you want to check, instead of the divisor. You have to addi $t1, $t1, 1 instead