usr/src/lib/libc/sparc/sys/gettimeofday.s

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1988 AT&T */
  28 /*        All Rights Reserved   */
  29
  30         .file   "gettimeofday.s"
  31
  32 /*
  33  * C library -- gettimeofday
  34  * int gettimeofday (struct timeval *tp);
  35  */
  36
  37 #include "SYS.h"
  38
  39         ANSI_PRAGMA_WEAK(gettimeofday,function)
  40
  41 /*
  42  * The interface below calls the trap (0x27) to get the timestamp in
  43  * secs and nsecs. It than converts the nsecs value into usecs before
  44  * it returns.
  45  *
  46  * The algorithm used to perform the division by 1000 is based upon
  47  * algorithms for division based upon multiplication by invariant
  48  * integers.  Relevant sources for these algorithms are:
  49  *
  50  * Granlund, T.; Montgomery, P.L.: "Division by Invariant Integers using
  51  * Multiplication". SIGPLAN Notices, Vol. 29, June 1994, page 61.
  52  *
  53  * Magenheimer, D.J.; et al: "Integer Multiplication and Division on the HP
  54  * Precision Architecture". IEEE Transactions on Computers, Vol 37, No. 8,
  55  * August 1988, page 980.
  56  *
  57  * Steele G.; Warren H.: Hacker's Delight. 2002 Pearson Education, Ch 10
  58  *
  59  */
  60
  61         ENTRY(gettimeofday)
  62         brz,pn  %o0, 1f
  63         mov     %o0, %o5
  64         SYSFASTTRAP(GETHRESTIME)
  65         stn     %o0, [%o5]
  66         sethi   %hi(0x10624DD3), %o2
  67         or      %o2, %lo(0x10624DD3), %o2
  68         mulx    %o1, %o2, %o2
  69         srlx    %o2, 38, %o2
  70         stn     %o2, [%o5 + CLONGSIZE]
  71 1:      RETC
  72         SET_SIZE(gettimeofday)