tsc -= _dl_cpuclock_offset;
tsc -= GL(dl_cpuclock_offset);
clock_gettime (clockid_t clock_id, struct timespec *tp){  struct timeval tv;  int retval = -1;  switch (clock_id)    {    case CLOCK_REALTIME:      retval = gettimeofday (&tv, NULL);      if (retval == 0)	/* Convert into `timespec'.  */	TIMEVAL_TO_TIMESPEC (&tv, tp);      break;#if HP_TIMING_AVAIL    case CLOCK_PROCESS_CPUTIME_ID:    case CLOCK_THREAD_CPUTIME_ID:      {	hp_timing_t tsc;	if (__builtin_expect (freq == 0, 0))	  {	    /* This can only happen if we haven't initialized the `freq'	       variable yet.  Do this now. We don't have to protect this	       code against multiple execution since all of them should	       lead to the same result.  */	    freq = __get_clockfreq ();	    if (__builtin_expect (freq == 0, 0))	      /* Something went wrong.  */	      break;	  }	if (clock_id == CLOCK_THREAD_CPUTIME_ID	    && __pthread_clock_gettime != NULL)	  {	    retval = __pthread_clock_gettime (freq, tp);	    break;	  }	/* Get the current counter.  */	HP_TIMING_NOW (tsc);	/* Compute the offset since the start time of the process.  */	tsc -= _dl_cpuclock_offset;	/* Compute the seconds.  */	tp->tv_sec = tsc / freq;	/* And the nanoseconds.  This computation should be stable until	   we get machines with about 16GHz frequency.  */	tp->tv_nsec = ((tsc % freq) * UINT64_C (1000000000)) / freq;	retval = 0;      }    break;#endif    default:      __set_errno (EINVAL);      break;    }  return retval;}