Is there any way to create a counter by self-modifying in MIPS?

Question

I want to create a subroutine like this:

• first time call: return 0
• second time call: return 1
• third time call: return 2
• ...

but we should not use register and memory to save the current number. we have to solve this by changing the code (self-modifying). Is there any way?

Answer 1

This is the solution which I found:

# subroutine
nextInt:                    # return value is in $v0
add     $v0,$zero,0
la      $t0,nextInt         # load subroutine address
lw      $t1,0($t0)          # load content of address
addi    $t1,$t1,1           # change content (increment)
sw      $t1,0($t0)          # save
jr      $ra