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  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 #if !defined(__ppc__)
  26 #include <stdint.h>
  27 #include <mach/clock.h>
  28 #include <mach/mach_time.h>
  29
  30 extern mach_port_t clock_port;
  31
  32 inline static uint64_t
  33 fast_get_nano_from_abs(int scale)
  34 {
  35     uint64_t value;
  36     asm (
  37         "rdtsc                  \n\t"
  38         "movl   %%edx,%%esi     \n\t"
  39         "mull   %%ecx           \n\t"
  40         "movl   %%edx,%%edi     \n\t"
  41         "movl   %%esi,%%eax     \n\t"
  42         "mull   %%ecx           \n\t"
  43         "xorl   %%ecx,%%ecx     \n\t"
  44         "addl   %%edi,%%eax     \n\t"
  45         "adcl   %%ecx,%%edx         "
  46                 : "=A"(value) : "c"(scale) : "%esi", "%edi");
  47         return value;
  48 }
  49
  50 uint64_t
  51 mach_absolute_time(void) {
  52         static int scale = 0;
  53
  54         if (__builtin_expect(scale == 0, 0)) {
  55                 mach_timebase_info_data_t info;
  56                 mach_timebase_info(&info);
  57                 scale = info.numer;
  58         }
  59         if (__builtin_expect(scale == 1, 0)) {
  60                 mach_timespec_t now;
  61                 (void)clock_get_time(clock_port, &now);
  62                 return (uint64_t)now.tv_sec * NSEC_PER_SEC + now.tv_nsec;
  63         }
  64         return fast_get_nano_from_abs(scale);
  65 }
  66 #endif