MIPS中使用addu检测溢出

我很难在MIPS中实现检测溢出并使用addu抛出错误。

这是学校的作业。我们得到的代码是一个非常基本的银行分类账。分类账要求用户输入,如果是正数,则添加到余额中,如果是负数,则从余额中减去。我已经改进了它,可以根据分配检测非整数输入,现在我需要能够检测溢出并抛出错误消息,如果检测到溢出,则不更改余额(然后重新提示事务)。我在这里想,因为这只是加法,如果符号相同,结果是相反的符号,那么就有溢出。我还认为,如果迹象相反,那么就不应该发生溢出。

目前,它似乎跳过了我的溢出检测,所以它可以工作,但没有检测到我需要的溢出。关于我做错了什么有什么建议吗?

以下是我的代码的相关部分:

loopB:
    li  $s1, 0          #### reset $s1
    add $s1, $zero, $t3     #### load integer value into $s1
    beqz    $s1, done       # If $s1 equals zero, branch to done
    li  $s2, 0          #### initialize $s2 for temporary balance
    addu    $s2, $s0, $t6       #### set temporary balance to initial balance
    addu    $s2, $s0, $s1       # add transaction amount to the temporary Balance

oTest:
    sltiu   $t6, $s0, 0     #### if $t6 == 1 then number is negative
    sltiu   $t7, $s1, 0     #### if $t7 == 1 then number is negative
    
    bne $t6, $t7, LoopC     #### if opposite signs then no overflow
    
    sltiu   $t8, $s2, 0     #### if $t8 == 1 then the number is negative
    
    and $t9, $t6, $t7       #### if $t9 == 1 then $t6 and $t7 are both negative
    
    bne     $t9, $t8, over      #### if $t9 and $t8 are not both negative, then overflow has occured
    
    sgtu    $t6, $s0, $zero     #### if $t6 == 1 then number is positive
    sgtu    $t7, $s0, $zero     #### if $t7 == 1 then number is positive
    sgtu    $t8, $s0, $zero     #### if $t8 == 1 then number is positive
    
    and $t9, $t6, $t7       #### if $t9 == 1 then $t6 and $t7 are both positive
    
    bne $t9, $t8, over      #### if $t8 and $t9 are not equal then overflow has occured

LoopC:
    addu    $s0, $s0, $s1       #### add transaction to balance
    li  $v0, 4          # system call code for print_string
    la  $a0, tabs       # load address of tabs into $a0
    syscall             # used to space over to the Balance column
    
    li  $v0, 1          # system call code for print_integer
    move    $a0, $s0        # move Bank Balance value to $a0 
    syscall             # print Bank Balance
    
    b   loop            # branch to loop
    
over:
    li  $v0, 4          #### system call code for print_string
    la  $a0, oMsg       #### load address of msg. into $a0
    syscall             #### print the string
    
    li  $s2, 0          #### reset $s2
    
    li  $v0, 1          #### system call code for print_integer
    move    $a0, $s0        #### move Bank Balance value to $a0 
    syscall             #### print Bank Balance
    
    b   loop            # branch to loop