#define rdtscll(val) __asm__ __volatile__ ("rdtsc" : "=A" (val))

#include<stdio.h>int i;unsigned long e;#define as(p) __asm__ __volatile__ (p)#define rdtscll() as("rdtsc")int main(void){	rdtscll();	as("movl %eax,%ecx");	rdtscll();	as("subl %ecx,%eax");	as("movl %eax,e");	printf("duration:%lld\n", e);	return 0;}