MIPS汇编语言回文串

下面是一个用MIPS汇编语言实现的回文串判断程序：

.data
msg1: .asciiz "Enter a string: "
msg2: .asciiz "The string is a palindrome."
msg3: .asciiz "The string is not a palindrome."
str: .space 100

.text
main:
    # Print message to enter string
    li $v0, 4 # syscall code for printing a string
    la $a0, msg1 # load address of message to print
    syscall
    
    # Read string from user input
    li $v0, 8 # syscall code for reading a string
    la $a0, str # load address of buffer to store string
    li $a1, 100 # maximum number of characters to read
    syscall
    
    # Calculate length of string
    move $t0, $zero # initialize length to 0
    la $t1, str # load address of string
loop:
    lb $t2, ($t1) # load byte from string
    beqz $t2, check # if byte is null, go to check
    addi $t0, $t0, 1 # increment length
    addi $t1, $t1, 1 # increment pointer
    j loop # go back to loop
check:
    subi $t1, $t1, 1 # move pointer to end of string
    div $t0, $two # divide length by 2
    mflo $t2 # store quotient in $t2
    j check_loop # jump to check loop
check_loop:
    beqz $t2, palindrome # if quotient is 0, go to palindrome
    lb $t3, ($t1) # load byte from end of string
    lb $t4, (str) # load byte from start of string
    bne $t3, $t4, not_palindrome # if bytes are not equal, go to not_palindrome
    addi $t1, $t1, -1 # decrement pointer to end of string
    addi $t0, $t0, -1 # decrement length
    j check_loop # go back to check loop
palindrome:
    # Print message that string is a palindrome
    li $v0, 4 # syscall code for printing a string
    la $a0, msg2 # load address of message to print
    syscall
    j exit # jump to exit
not_palindrome:
    # Print message that string is not a palindrome
    li $v0, 4 # syscall code for printing a string
    la $a0, msg3 # load address of message to print
    syscall
exit:
    li $v0, 10 # syscall code for exiting program
    syscall

该程序首先从用户输入中读取一个字符串，并计算出字符串的长度。然后，程序从字符串的两端开始比较每个字符，如果字符相同，则继续比较下一个字符，如果字符不同，则程序将打印一条消息，指出该字符串不是回文串。如果程序成功比较了整个字符串，那么将打印一条消息，指出该字符串是回文串。最后，程序将退出。