text: /*
     +----------------------------------------------------------------------+
     | HipHop for PHP                                                       |
     +----------------------------------------------------------------------+
     | Copyright (c) 2010-2014 Facebook, Inc. (http://www.facebook.com)     |
     +----------------------------------------------------------------------+
     | This source file is subject to version 3.01 of the PHP license,      |
     | that is bundled with this package in the file LICENSE, and is        |
     | available through the world-wide-web at the following url:           |
     | http://www.php.net/license/3_01.txt                                  |
     | If you did not receive a copy of the PHP license and are unable to   |
     | obtain it through the world-wide-web, please send a note to          |
     | license@php.net so we can mail you a copy immediately.               |
     +----------------------------------------------------------------------+
  */
  
  #ifndef incl_HPHP_TSC_H_
  #define incl_HPHP_TSC_H_
  
  #include "hphp/util/assertions.h"
  
  namespace HPHP {
  
  /*
   * Return the underlying machine cycle counter. While this is slightly
   * non-portable in theory, all the CPUs you're likely to care about support
   * it in some way or another.
   */
  inline uint64_t cpuCycles() {
  #ifdef __x86_64__
    uint64_t lo, hi;
    asm volatile("rdtsc" : "=a"((lo)),"=d"(hi));
    return lo | (hi << 32);
  #else
    not_implemented();
  #endif
  }
  
  inline void cpuRelax() {
  #ifdef __x86_64__
    asm volatile("pause");
  #endif
  }
  
  inline void cycleDelay(uint32_t numCycles) {
    auto start = cpuCycles();
    do {
      if (numCycles > 100) cpuRelax();
    } while (cpuCycles() - start > numCycles);
  }
  
  }
  
  #endif
  