内联汇编的好处!

code

1. #include
   
2. 
   
3. int main(void)
   
4. {
   
5. int a = 10;
   
6. int b = 20;
   
7. int result;
   
8. 
   
9. __asm__("cmp %1, %2\n\t"
   
10. "jge greater\n\t"
    
11. "movl %1, %0\n\t"
    
12. "jmp end\n"
    
13. "greater:\n\t"
    
14. "movl %2, %0\n"
    
15. "end:"
    
16. :"=r"(result)
    
17. :"r"(a), "r"(b));
    
18. printf("The larger value is %d\n", result);
    
19. return 0;
    
20. }
    

1. #include
   
2. 
   
3. int main()
   
4. {
   
5. int a = 10;
   
6. int b = 20;
   
7. int result;
   
8. 
   
9. result = a > b ? a : b;
   
10. printf("The larger value is %d\n", result);
    
11. return 0;
    
12. }
    

Result

zhili-hus-computer:~/Documents zhilihu$ ls -l test a.out 

-rwxr-xr-x   1 zhilihu  zhilihu  13380 Feb 26 19:18 a.out

-rwxr-xr-x   1 zhilihu  zhilihu  13344 Feb 26 19:27 test

zhili-hus-computer:~/Documents zhilihu$ time ./a.out 

The larger value is 20

real    0m0.032s

user    0m0.002s

sys     0m0.007s

zhili-hus-computer:~/Documents zhilihu$ time ./test  

The larger value is 20

real    0m0.062s

user    0m0.002s

sys     0m0.010s