tsc.h

/*
 * Copyright 2021 Andrei Pangin
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef _TSC_H
#define _TSC_H

#include "os.h"

#if defined(__x86_64__)

#define TSC_SUPPORTED true

static inline u64 rdtsc() {
  u32 lo, hi;
  asm volatile("rdtsc" : "=a"(lo), "=d"(hi));
  return ((u64)hi << 32) | lo;
}

#elif defined(__i386__)

#define TSC_SUPPORTED true

static inline u64 rdtsc() {
  u64 result;
  asm volatile("rdtsc" : "=A"(result));
  return result;
}

#else

#define TSC_SUPPORTED false
#define rdtsc() 0

#endif

class TSC {
private:
  static bool _initialized;
  static bool _enabled;
  static u64 _offset;
  static u64 _frequency;

public:
  static void initialize();

  static bool initialized() { return TSC_SUPPORTED ? _initialized : true; }

  static bool enabled() { return TSC_SUPPORTED && _enabled; }

  static u64 ticks() { return enabled() ? rdtsc() - _offset : OS::nanotime(); }

  static u64 frequency() { return _frequency; }

  static u64 ticks_to_millis(u64 ticks) {
    return TSC_SUPPORTED ? 1000 * ticks / _frequency : ticks / 1000 / 1000;
  }
};

#endif // _TSC_H