rot.mips

  .text
  .globl main

main:
  addi $a0, $zero, 7
  jal rot
  j exit

rot:
# Check if $a0 < 2
  slti $t0, $a0, 2
  bne $t0, $zero, rot_return_0

# Check if $a0 == 2
  addi $t0, $zero, 2
  beq $t0, $a0, rot_return_1

# Preserve original argument and return address
  addi $sp, $sp, -8
  sw $a0, 0($sp)
  sw $ra, 4($sp)

# $v0 = 1 + rot($a0 - 2)
  addi $a0, $a0, -2
  jal rot
  addi $v0, $v0, 1
  
# Restore original argument and return address
  lw $a0, 0($sp)
  lw $ra, 4($sp)
  addi $sp, $sp, 8

# return $v0
  jr $ra

rot_return_0:
  addi $v0, $zero, 0
  jr $ra

rot_return_1:
  addi $v0, $zero, 1
  jr $ra

exit:

Ficou bem parecido com o meu, só mudou o fato de eu já entrar empilhando e sempre desempilhar no fim. Se liga:

j MAIN


ROT:
	addi $sp, $sp, -8
	sw $ra, 4($sp)
	sw $a0, 0($sp)
BODY:
	addi $t2, $zero, 2		#holds the value 2 (should've been initialized only once)
	slt $t0, $a0, $t2		#if n < 2
	beq $t0, $zero, ELSE1
	addi $v0, $zero, 0
	j RET
ELSE1:
	bne $a0, $t2, ELSE2		#if n == 2
	addi $v0, $zero, 1
	j RET
ELSE2:
	addi $a0, $a0, -2
	jal ROT
	lw $ra, 4($sp)
	lw $a0, 0($sp)
	addi $v0, $v0, 1
RET:
	addi $sp, $sp, 8
	jr $ra


MAIN:
	addi $s0, $zero, 6		#n = 6
	add $a0, $zero, $s0
	jal ROT
	add $s1, $zero, $v0		#result = rot(6)