汇编写下strcpy

  1 #include <stdio.h>
  2
  3 int main()
  4 {
  5         char *source = "hello world\n";
  6         char dest[1024] = {0};
  7         char *p = dest;
  8         char c = ‘\0‘;
  9 #if 0
 10 loop:
 11         if(*(source + i) == ‘\0‘){
 12                 *(dest + i) = ‘\0‘;
 13                 goto exit;
 14         }
 15         *(dest + i) = *(source + i);
 16         i++;
 17         goto loop;
 18 exit:
 19 #else
 20         __asm__ __volatile__(
 21                 "ldr r2, [%2]\n"
 22                 "mov r0, #0\n"
 23                 "loop:\n"
 24                 "ldr r1, [%0, r0]\n"
 25                 "cmp r1, r2\n"
 26                 "beq exit\n"
 27                 "str r1, [%1, r0]\n"
 28                 "add r0, r0, #1\n"
 29                 "b loop\n"
 30                 "exit:\n"
 31                 :
 32                 :"r" (source), "r" (dest), "r" (&c)
 33                 :"r0", "r1", "r2", "memory"
 34         );
 35 #endif
 36
 37         printf("%s\n", p);
 38 }

注意：最后一行要写上保护（r1,r2,r3）否则会段错误。