cycle_counter.h

typedef unsigned long long CPU_clock_num;
CPU_clock_num realcc(void);

cycle_counter.c

#include "cycle_counter.h"

CPU_clock_num realcc(void) {
	unsigned long long cc;

	/* read the 64 bit process cycle counter into variable cc */

	asm volatile("rdtsc" : "=r"(cc) : : "memory");

	return cc;
}