Complications in MIPS code of Recursive Reversal of a string - string

Question

I have written this MIPS code of recursive reversal of a string. However, the output is coming out to be the same that has been input by the user. Can someone please help me out and indicate where am I going wrong? Please reply as soon as possible.
# Program to reverse a string input by the user
.data
.align 2
array: .space 50
input: .asciiz "Enter a string: "
output: .asciiz "\nThe reversed string is: "
.text
.globl main
main:
addi $s0, $zero, 50
addi $t0, $zero, 0
la $a0, input
li $v0, 4
syscall
la $a0, array
li $v0, 8
syscall
initiate:
add $t0, $a0, $zero # initial address
add $t1, $zero, $zero # count=0
add $t2, $zero, $zero # i=0
la $t0, array # base address of the array
add $t3, $t0, $t2 # & array[i]
loop:
lb $t3, 0($t3) # fetch array[i]
beqz $t3, EndOfString # loop exits if it is a null character;array[i] !='\0'
bne $t3, $0, continue # otherwise loop continues
add $t1, $t1, 1 # count++
continue:
add $t2, $t2, 1 # i++
j loop
addi $a1, $zero, 50
jal StringReversal
EndOfString:
la $a0, output
li $v0, 4
syscall
la $a0, array
li $v0, 4
syscall
li $v0, 10
syscall
StringReversal:
add $t0, $a0, $zero # initial address
add $t4, $zero, $zero # j = start = 0
addi $t5, $a1, -1 # k = end-1
SwapLoop:
add $t6, $t0, $t4
lb $t7, 0($t6) # load byte array[start]
add $t8, $t0, $t5
lb $t9, 0($t8) # load byte array[end-1]
sb $t7, 0($t8) # array[end-1] = array[start]
sb $t9, 0($t6) # array[start] = array[end-1]
addi $t4, $t4, 1 # j++
addi $t5, $t5, -1 # k--
slt $t9, $t5, $t4
beqz $t9, SwapLoop
jr $ra

Answer 1

# Program to reverse a string input by the user
.data
.align 2
array: .space 50
input: .asciiz "Enter a string: "
output: .space 50
size: .word 49
.text
j main
length:
# return length of the input string
# $a0 - address of string
# $v0 - length of the string
move $v0, $zero # set $v0 to 0
length_loop:
lb $t0, 0($a0)
beqz $t0, length_end
addi $v0, $v0, 1
addi $a0, $a0, 1
b length_loop
length_end:
subi $v0, $v0, 1
jr $ra
reverse:
# $a0 - address of string to reverse
# a1 - length of the string
# a2 - address of string where to store the reverse
addi $sp, $sp, -4
sw $ra, 0($sp)
bltz $a1, reverse_end
lb $t0, 0($a0)
subi $a1, $a1, 1
subi $a0, $a0, 1
sb $t0, 0($a2)
addi $a2, $a2, 1
jal reverse
reverse_end:
lw $ra, 0($sp)
addi $sp, $sp, 4
jr $ra
main:
addi $s0, $zero, 50
addi $t0, $zero, 0
la $a0, input
li $v0, 4
syscall
# read string from the user into $a0
la $a0, array
lw $a1, size
li $v0, 8
syscall
# reverse the string
jal length # $v0 contains length of string
la $a0, array
move $a1, $v0
add $a0, $a0, $a1 # pointer to the last character
la $a2, output
jal reverse
# print the reverse string
la $a0, output
li $v0, 4
syscall
Output:
Enter a string: hello
olleh
-- program is finished running (dropped off bottom) --

Answer 2

In your continue label, it looks as though j loop is called too early, and hence
addi $a1, $zero, 50
jal StringReversal
is never reached, hence the instructions in the StringReversal label are not performed.