i386/mach/mach_absolute_time.c

   1 /*
   2  * Copyright (c) 2000-2002 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23 #if !defined(__ppc__)
  24 #include <stdint.h>
  25 #include <mach/clock.h>
  26 #include <mach/mach_time.h>
  27
  28 extern mach_port_t clock_port;
  29
  30 inline static uint64_t
  31 fast_get_nano_from_abs(int scale)
  32 {
  33     uint64_t value;
  34     asm (
  35         "rdtsc                  \n\t"
  36         "movl   %%edx,%%esi     \n\t"
  37         "mull   %%ecx           \n\t"
  38         "movl   %%edx,%%edi     \n\t"
  39         "movl   %%esi,%%eax     \n\t"
  40         "mull   %%ecx           \n\t"
  41         "xorl   %%ecx,%%ecx     \n\t"
  42         "addl   %%edi,%%eax     \n\t"
  43         "adcl   %%ecx,%%edx         "
  44                 : "=A"(value) : "c"(scale) : "%esi", "%edi");
  45         return value;
  46 }
  47
  48 uint64_t
  49 mach_absolute_time(void) {
  50         static int scale = 0;
  51
  52         if (__builtin_expect(scale == 0, 0)) {
  53                 mach_timebase_info_data_t info;
  54                 mach_timebase_info(&info);
  55                 scale = info.numer;
  56         }
  57         if (__builtin_expect(scale == 1, 0)) {
  58                 mach_timespec_t now;
  59                 (void)clock_get_time(clock_port, &now);
  60                 return (uint64_t)now.tv_sec * NSEC_PER_SEC + now.tv_nsec;
  61         }
  62         return fast_get_nano_from_abs(scale);
  63 }
  64 #endif