cycles.c

#include <stdio.h>

static inline void _main (void){

}

typedef unsigned long long u64;
static inline u64 cycle (void){
  u64 stamp;
  __asm__ __volatile__("rdtscp; shl $32,%%rdx; or %%rdx,%%rax" : "=a"(stamp));
  return stamp;
}

u64 try (void){
  u64 st,end;
  st  = cycle();
  _main();
  end = cycle();
  printf("%llu\n", end-st);
  return 0;
}

int main (void){

  for(int i=0; i <= 1000; i++)
    try();
}