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 #ifndef incl_HPHP_TSC_H_
  18 #define incl_HPHP_TSC_H_
  19
  20 #include <folly/portability/Asm.h>
  21
  22 #include "hphp/util/assertions.h"
  23 #ifdef _MSC_VER
  24 #include <intrin.h>
  25 #endif
  26
  27 namespace HPHP {
  28
  29 /*
  30  * Return the underlying machine cycle counter. While this is slightly
  31  * non-portable in theory, all the CPUs you're likely to care about support
  32  * it in some way or another.
  33  */
  34 inline uint64_t cpuCycles() {
  35 #ifdef __x86_64__
  36   uint64_t lo, hi;
  37   asm volatile("rdtsc" : "=a"((lo)),"=d"(hi));
  38   return lo | (hi << 32);
  39 #elif __powerpc64__
  40   // This returns a time-base
  41   uint64_t tb;
  42   asm volatile("mfspr %0, 268" : "=r" (tb));
  43   return tb;
  44 #elif _MSC_VER
  45   return (uint64_t)__rdtsc();
  46 #elif __aarch64__
  47   // FIXME: This returns the virtual timer which is not exactly
  48   // the core cycles but has a different frequency.
  49   uint64_t tb;
  50   asm volatile("mrs %0, cntvct_el0" : "=r" (tb));
  51   return tb;
  52 #else
  53   not_implemented();
  54 #endif
  55 }
  56
  57 inline void cpuRelax() {
  58   folly::asm_volatile_pause();
  59 }
  60
  61 inline void cycleDelay(uint32_t numCycles) {
  62   auto start = cpuCycles();
  63   do {
  64     if (numCycles > 100) cpuRelax();
  65   } while (cpuCycles() - start < numCycles);
  66 }
  67
  68 }
  69
  70 #endif