Question

我正在尝试使用MASM编写InsertionSort的迭代版本。在反复遇到意外错误之后，我尝试逐行运行代码，并在调试器中查看它是否达到了预期的效果。可以肯定的是，我在“ while循环”中的cmp指令似乎并没有每次都应该跳：

; store tmp in edx
    movzx edx, word ptr[ebx + esi * 2];   edx: tmp = A[i]
    ...
    //blah blah

while_loop :
...
    movzx eax, word ptr[ebx + 2 * edi]
    cmp dx, ax
    jge exit_while

例如，如果我使用给定的数据，则在第一次“ for循环”迭代之后，将到达EDX = 0000ABAB和EAX = 00003333的地步。我到达了线：

cmp dx, ax
jge exit_while

自ABAB> 3333起，我希望它会跳到exit_while，但事实并非如此！

这是怎么回事？？？我完全不知所措。

.data
arr word 3333h, 1111h, 0ABABh, 1999h, 25Abh, 8649h, 0DEh, 99h
sizeArr dword lengthof arr
printmsg byte "The array is: [ ", 0
comma byte ", ", 0
endmsg byte " ]", 0

.code
main proc
    call printArr
    call crlf
    push sizeArr
    push offset arr
    call insertionsort
    call crlf
    call printArr
    call crlf
    call exitprocess
main endp


insertionsort proc
    push ebp
    mov ebp, esp
    _arr = 8
    len = _arr + 4

    mov ebx, [ebp + _arr]
    mov ecx, [ebp + len]
    dec ecx
    mov esi, 1; store i in esi, with i=1 initially

;   for (i = 1; i < SIZE; i++)
forloop:

; store tmp in edx
    movzx edx, word ptr[ebx + esi * 2];   edx: tmp = A[i]

; store j in edi, where in initially j = i
    mov edi, esi
;set j=i-1
    dec edi

;while (j >= 0 &&   tmp<arr[j])
while_loop :
    cmp edi, 0
    jl exit_while
    movzx eax, word ptr[ebx + 2 * edi]
; cmp dx, [ebx + 2 * edi]
    cmp dx, ax
    jge exit_while

; A[j] = A[j-1]
    push word ptr [ebx+2*edi]
    pop word ptr [ebx+2*edi+2]
; j = j - 1
    dec edi
    jmp while_loop

exit_while:
    push dx
    pop word ptr[ebx + 2*edi+2]
    ; mov[ebx + edi], dx;    A[j] = tmp
    inc esi;     i = i + 1
    loop forloop

finished:
    mov esp, ebp
    pop ebp
    ret 8
insertionsort endp



printArr proc
    push ebp
    mov ebp, esp
    mov ebx, offset sizeArr
    mov ecx, [ebx]
    mov esi, offset arr
    mov edx, offset printmsg
    call writestring
    mov edx, offset comma
loop1 :
    movzx eax, word ptr [esi]
    call writeHex
    call writestring
    add esi, 2
loop loop1

    mov edx, offset endmsg
    call writestring
    mov esp, ebp
    pop ebp
    ret
printArr endp

Answer 1

jge是带符号值的版本-因此，具有值ABAB的单词为负-因此您会看到比较结果。

请尝试jae（如果大于或等于则跳转）-等价的无符号。

cmp指令未使jge在InsertionSort

1 个答案: