Nested Loops in MIPS - mips

Question

This is boiling my brain, I've just started learn MIPS. The assignment asks us to use loops and maybe even a stack to do a simple multiplication by squaring a three digit number. For the assignment to be correct, the program needs to run for a minimum of 30 seconds doing the same calculation over and over.
Obviously I'm not asking for you to do my assignment (I want to learn), however I'm stumped on how to implement nested loops in MIPS, there isn't much online. I found something on Stack Overflow and tried to implement the same style but it doesn't work. A single loop works fine, it only runs for one second though so its nowhere near close enough. My problem is how to input a second loop really.
Here's my code:
.data
enterNumber: .asciiz "Enter three digit number \n"
.text
main:
addi $t3, $zero, 0
addi $t1, $zero, 0 #counter for second for loop
#asks for number
li $v0, 4
la $a0, enterNumber
syscall
#receives number
li $v0, 5
syscall
move $t0, $v0 #move number to t0
For1:
beq, $t3, $t0, exit #if counter= t0 then loop ends
For2:
beq, $t1, $t0, For1 #if counter= t0 then loop ends
addi $t2, $zero, 0 #resets t2 to 0
mul $t2, $t0, $t0 #multiply number multiplied by number
addi $t1, $t1, 1 #add 1 to counter
j For2 #jump back to the top
addi $t2, $zero, 0 #resets t2 to 0
mul $t2, $t0, $t0 #multiply number multiplied by number
addi $t3, $t3, 1 #add 1 to counter
j For1 #jump back to for loop
exit:
li $v0, 1
move $a0, $t2 #print out multiplication
syscall
#tell system to stop
li $v0, 10
syscall
The program runs through the inner loop (For2) fine, but its not incrementing the outer loop at all. Thanks in advance

Answer 1

The only problem with your code is that everything you've written in the outer loop(For1), after the inner loop (For2) will never be executed, because of the way you've written the conditions in For2. You only need to make a small change to your loops code: make For2 jump to the last part of your For1 loop in case counter = t0 instead of making it jump to For1.
For1:
beq, $t3, $t0, exit #if counter= t0 then loop ends
For2:
beq, $t1, $t0, exit2 #if counter= t0 then loop ends
addi $t2, $zero, 0 #resets t2 to 0
mul $t2, $t0, $t0 #multiply number multiplied by number
addi $t1, $t1, 1 #add 1 to counter
j For2 #jump back to the top
exit2:
addi $t2, $zero, 0 #resets t2 to 0
mul $t2, $t0, $t0 #multiply number multiplied by number
addi $t3, $t3, 1 #add 1 to counter
j For1 #jump back to for loop

Answer 2

You need to make a small change to your loops code.
Make For2 jump to the last part of your For1 loop in case counter = t0 instead of making it jump to For1.
write below code under For1 loop.
For2exit:
addi $t2, $zero, 0 #resets t2 to 0
mul $t2, $t0, $t0 #multiply number multiplied by number
addi $t3, $t3, 1 #add 1 to counter
j For1 #jump back to for loop
and make change in the for2. make it jump to For2exit rather to For1.