PC中的Mips例外

Question

我正在尝试在MIPS中实现二叉搜索树。为了实现，我迭代一个循环，要求用户输入一个数字并将数字插入BST。迭代继续，直到用户没有更多要插入的数字。在第一次迭代之后，会发生这种情况：

这是代码：

   .data             # Put Global Data here
    ask: .asciiz "Enter the list of numbers to be sorted one by one."
    input: .asciiz "Enter a number:"
    ques: .asciiz "Do you want to enter more? (input 1 if you want to enter
                    more, 0 if you are done)"
    root: .word 0
    # Code section
    .text             # Put program here
    .globl main           # globally define 'main'

    main:
    li $v0,4
    la $a0,ask
    syscall
    add $s0,$s0,$zero

    loop:
       li $v0,4
       la $a0,input
       syscall
       li $v0,5
       syscall
       lw $t0,root
       add $a1,$t0,$zero
       add $a0,$v0,$zero
       jal insert
       beq $t0,$zero,first
     first: sw $v0,root
            j cont
     cont:  li $v0,4
            la $a0,ques
            syscall
            li $v0,5
            syscall
            bne $v0,$zero,loop



     # terminate the program with system call
     li $v0, 10         # syscall to exit cleanly from main only
     syscall            # this ends execution
     .end

     insert:
             addi $sp,$sp,-12
             sw $a0,0($sp)
             sw $a1,4($sp)
             sw $ra,8($sp)
             add $s0,$a1,$zero
             beq $s0,$zero,start
             j c1
      start:
             jal newnode
             add $t1,$t1,$v0
             sw $a0,0($t1)
             sw $zero,4($t1)
             sw $zero,8($t1)
             j last

      c1:   lw $t6,0($s0)
            add $t2,$t6,$zero
            slt $t3,$a0,$t2
            bne $t3,$zero,left
            j right

      left: lw $t4,8($s0)
            add $a1,$t4,$zero
            jal insert
            add $t5,$v0,$zero
            sw $t5,8($s0)
            j last

      right: lw $t4,4($s0)
             add $a1,$t4,$zero
             jal insert
             add $t5,$v0,$zero
             sw $t5,4($s0)
             j last
      last: lw $a0,0($sp)
            lw $a1,4($sp)
            lw $ra,8($sp)
            addi $sp,$sp,12
            jr $ra


       newnode: addi $sp,$sp,-12
                sw $a0,0($sp)
                sw $a1,4($sp)
                sw $ra,8($sp)
                li $v0,9
                li $a0,12
                syscall
                lw $a0,0($sp)
                lw $a1,4($sp)
                lw $ra,8($sp)
                addi $sp,$sp,12
                jr $ra

任何帮助将不胜感激。谢谢。