#include <stdio.h>

int main()
{
    char ciag[] = "Hello";

    asm volatile(
        ".intel_syntax noprefix;"

        "mov eax, %0;"  //pointer to the first char in array
        "xor ebx, ebx;"

        "length:"
                "mov cl, [eax];"
                "inc eax;"
                "inc ebx;"
                "cmp cl, 0;"
                "jne length;"

        "dec eax;" // eax was on 0 of a string, now its on the last char
        "mov edx, eax;" //edx on the last char
        "mov eax, %0;"
        "shr ebx, 1;" //divide counter by 2 to get the number of reverse repetition
        "mov esi, edx;"//dont know why but it cant be ebx when MOV CL, EBX - need esi
        "mov edi, eax;"//same

        "reverse:"
                "mov cl, [esi];" //cl has last char
                "mov di, [edi];" //dl has first char
                "mov [edi], cl;"
                "mov [esi], di;"
                "dec esi;"
                "inc edi;"
                "dec ebx;"
                "jnz reverse;"
        ".att_syntax prefix;"
        :
        :"r" (ciag)
        :"eax", "ebx", "ecx", "edi", "esi"
    );


    printf("Reverse string: %s\n", ciag);
    return 0;
}