Retrieving Data from an Array (cannot seem to get it working) - mips

Question

I'm currently working on a palindrome function in MIPS that takes a char array and returns 0 if it is not a palindrome, else 1. I've got everything seemingly working except for the part where I find data at index i and array.length-i-1. If someone could lead me in the right direction I'd really appreciate it.
Here's the java code I'm going off of:
int Palindrome(char[] s) {
for(int i = 0; i < (s.length / 2); i++) {
if(s[i] != s[s.length - 1 - i])
return 0;
}
return 1;
}
Here's the Palindrome function:
palindrome:
# Get length of array and store it in $t1
addi $sp, $sp, -8
sw $ra, 0($sp)
sw $a0, 4($sp)
li $t1, 0
lengthWhile:
lw $t2, 0($a0)
beq $t2, $zero, startPalindrome
addi $t1, $t1, 1
addi $a0, $a0, 4
j lengthWhile
startPalindrome:
div $t2, $t1, 2 # Stores a.length / 2 into $t2
add $t3, $t3, $zero # i value (0 - (a.length/2 - 1))
add $t4, $t4, $t1
subi $t4, $t4, 1 # a.length-1
# $t1 = a.length
# $t2 = a.length / 2
# $t3 = i
# $t4 = a.length - 1
palLoop:
bge $t3, $t2, exitLoop
sub $t4, $t4, $t3 # Puts a.length-1-i into $t4
sll $t5, $t3, 2
add $t6, $a0, $t5
lw $s1, 0($t6)
sll $s3, $t4, 2
add $t7, $a0, $s3
lw $s2, 0($t7)
bne $s1, $s2, return0
# Increase i and start loop again
addi $t3, $t3, 1
j palLoop
return0:
li $v0, 0
jr $ra
exitLoop:
li $v0, 1
jr $ra
Here's the main:
.data
charArray: .word 'a', 'b', 'c', 'd', 'c', 'w', 'a'
.text
main:
# Palindrom Function
la $a0, charArray
jal palindrome
move $a0, $v0
li $v0, 1
syscall
# Exit Program
li $v0, 10
syscall
Thank you in advance for any help. (To specify, palLoop is where I'm having trouble).

Answer 1

Not directly part of your question, but charArray: .word 'a', 'b', 'c', 'd', 'c', 'w', 'a' is really a word array containing a chatarter value, not a character array.
It looks like that will wok as you are using word array everywhere, however wont wok if you use a proper character array.
add $t3, $t3, $zero is t3 = t3 + 0 - what is t3 prior to that?
add $t4, $t4, $t1 - same comment
sub $t4, $t4, $t3 # Puts a.length-1-i into $t4 - will overwrite a.length-1 (t4) so is going not be right on the 2nd time through the loop.