一段汇编

#include<stdio.h>
int main()
{
    int n = 2;
    while (n--) {
        printf("%d", n);
    }

    return 0;
}

.LC0:
        .string "%d"
main:
        push    rbp
        mov     rbp, rsp
        sub     rsp, 16
        mov     DWORD PTR [rbp-4], 2
        jmp     .L2
.L3:
        mov     eax, DWORD PTR [rbp-4]
        mov     esi, eax
        mov     edi, OFFSET FLAT:.LC0
        mov     eax, 0
        call    printf
.L2:
        mov     eax, DWORD PTR [rbp-4]
        lea     edx, [rax-1]
        mov     DWORD PTR [rbp-4], edx
        test    eax, eax
        jne     .L3
        mov     eax, 0
        leave
        ret

#include<stdio.h>
int main()
{
    int n = 2;
    while (--n) {
        printf("%d", n);
    }

    return 0;
}

.LC0:
        .string "%d"
main:
        push    rbp
        mov     rbp, rsp
        sub     rsp, 16
        mov     DWORD PTR [rbp-4], 2
        jmp     .L2
.L3:
        mov     eax, DWORD PTR [rbp-4]
        mov     esi, eax
        mov     edi, OFFSET FLAT:.LC0
        mov     eax, 0
        call    printf
.L2:
        sub     DWORD PTR [rbp-4], 1
        cmp     DWORD PTR [rbp-4], 0
        jne     .L3
        mov     eax, 0
        leave
        ret