This is a code from this link from stackexchange: MIPS Assembly code to find all the prime numbers below an inputted number
I am studying this for my exam, but how would I fix this code to make it so that it prints out prime numbers from 2-N
As the post in the link, I was able to complete step two from the answer but am currently having difficultly implementing step 1 in the code
Here are the two problem that occur in the code: There are two problems:
When you increment i you forget to set j back to 2. L3 should be moved 1 line up. (difficulty implementing this)
ble in MIPS is less than or equal to, so your code is actually checking j <= i, not j < i. This causes your code to check i % j when i = j, which always has a remainder 0 and will register as not prime. Changing 'ble' to 'blt' should fix this. Same goes for the i < n check.
Here is the code:
# The number is read through the keyboard
.text
.globl main
main:
# Display message to user for a number
li $v0, 4
la $a0, prompt1
syscall
# read keyboard into $v0 (number x is upper bound number to find primes)
li $v0, 5
syscall
# move the number from $v0 to $t0
move $t0, $v0 # $t0 = n
# store 2 in $t1 and $t2
li $t1, 2 # i
li $t2, 2 # j
L3: # for (int i=2; i<n; i++)
# store 0 in $t3
li $t3, 0 # p = 0;
L2: # for (int j=2; j<i; j++)
# do div of two numbers
div $t2, $t1
# store the remainder in $t4
mfhi $t4
# branch if remainder is not 0 to L1
bne $t4, 0, L1 # if (i % j == 0)
# set $t3 as 1
li $t3, 1 # p = 1
# if p=1 break to next i
beq $t3, 1, L4
L1: # if (i % j == 0)
# add 1 to t2
addi $t2, $t2, 1 # j++
# repeat code while j < i
ble $t2, $t1, L2
# print integer function call 1
# put the answer into $a0
li $v0, 1
move $a0, $t1
syscall # System.out.println(i)
#print comma
li $v0, 4
la $a0, comma
syscall
L4:
# add 1 to t1
addi $t1, $t1, 1 # i++
# repeat code while i < n
ble $t1, $t0, L3 # for (int i=2; i<n; i++)
.data
prompt1:
.asciiz "Enter a number "
comma:
.asciiz ","
Thanks in advance :]
