-rw-r--r-- 1070 djbsort-20190516/cpucycles/cortex_vct/cpucycles.c
/*
cpucycles/cortex_vct.c version 20180222
D. J. Bernstein
Romain Dolbeau
Public domain.
*/
#define SCALE 1
#include <time.h>
#include <unistd.h>
#include <sys/time.h>
#include <stdlib.h>
#include "cpucycles.h"
static inline unsigned long long aarch64_timer_get_cntfrq(void) {
unsigned long long val;
asm volatile("mrs %0, CNTFRQ_EL0" : "=r" (val));
return val;
}
#define V8FREQ 1
long long cpucycles(void)
{
long long Rt;
asm volatile("mrs %0, CNTVCT_EL0" : "=r" (Rt));
return Rt * V8FREQ;
}
long long cpucycles_persecond(void) {
struct timeval t0,t1;
long long c0,c1;
unsigned long long f;
long long r;
double d0,d1;
gettimeofday(&t0,(struct timezone *) 0);
c0 = cpucycles();
sleep(1);
gettimeofday(&t1,(struct timezone *) 0);
c1 = cpucycles();
d0 = (double) t0.tv_sec;
d0 += ((double) t0.tv_usec) / 1000000.0;
d1 = (double) t1.tv_sec;
d1 += ((double) t1.tv_usec) / 1000000.0;
r = (c1-c0)/(d1-d0);
f = aarch64_timer_get_cntfrq();
if (llabs(f-r) < 100)
return f;
/* something is wrong here, fixme ? */
return r;
}