hphp/util/cycles.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-present Facebook, Inc. (http://www.facebook.com)  |
   6    +----------------------------------------------------------------------+
   7    | This source file is subject to version 3.01 of the PHP license,      |
   8    | that is bundled with this package in the file LICENSE, and is        |
   9    | available through the world-wide-web at the following url:           |
  10    | http://www.php.net/license/3_01.txt                                  |
  11    | If you did not receive a copy of the PHP license and are unable to   |
  12    | obtain it through the world-wide-web, please send a note to          |
  13    | license@php.net so we can mail you a copy immediately.               |
  14    +----------------------------------------------------------------------+
  15 */
  16
  17 #pragma once
  18
  19 #include <folly/portability/Asm.h>
  20
  21 #include "hphp/util/assertions.h"
  22 #ifdef _MSC_VER
  23 #include <intrin.h>
  24 #endif
  25
  26 namespace HPHP {
  27
  28 /*
  29  * Return the underlying machine cycle counter. While this is slightly
  30  * non-portable in theory, all the CPUs you're likely to care about support
  31  * it in some way or another.
  32  */
  33 inline uint64_t cpuCycles() {
  34 #ifdef __x86_64__
  35   uint64_t lo, hi;
  36   asm volatile("rdtsc" : "=a"((lo)),"=d"(hi));
  37   return lo | (hi << 32);
  38 #elif __powerpc64__
  39   // This returns a time-base
  40   uint64_t tb;
  41   asm volatile("mfspr %0, 268" : "=r" (tb));
  42   return tb;
  43 #elif _MSC_VER
  44   return (uint64_t)__rdtsc();
  45 #elif __aarch64__
  46   // FIXME: This returns the virtual timer which is not exactly
  47   // the core cycles but has a different frequency.
  48   uint64_t tb;
  49   asm volatile("mrs %0, cntvct_el0" : "=r" (tb));
  50   return tb;
  51 #else
  52   not_implemented();
  53 #endif
  54 }
  55
  56 inline void cpuRelax() {
  57   folly::asm_volatile_pause();
  58 }
  59
  60 inline void cycleDelay(uint32_t numCycles) {
  61   auto start = cpuCycles();
  62   do {
  63     if (numCycles > 100) cpuRelax();
  64   } while (cpuCycles() - start < numCycles);
  65 }
  66
  67 }
  68