lib/libc/quad/ashrdi3.c

   1 /*-
   2  * Copyright (c) 1992, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This software was developed by the Computer Systems Engineering group
   6  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
   7  * contributed to Berkeley.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)ashrdi3.c        8.1 (Berkeley) 6/4/93
  34  * $FreeBSD: src/lib/libc/quad/ashrdi3.c,v 1.3 2007/01/09 00:28:03 imp Exp $
  35  */
  36
  37 #include "quad.h"
  38
  39 /*
  40  * Shift a (signed) quad value right (arithmetic shift right).
  41  */
  42 quad_t
  43 __ashrdi3(quad_t a, qshift_t shift)
  44 {
  45         union uu aa;
  46
  47         aa.q = a;
  48         if (shift >= LONG_BITS) {
  49                 long s;
  50
  51                 /*
  52                  * Smear bits rightward using the machine's right-shift
  53                  * method, whether that is sign extension or zero fill,
  54                  * to get the `sign word' s.  Note that shifting by
  55                  * LONG_BITS is undefined, so we shift (LONG_BITS-1),
  56                  * then 1 more, to get our answer.
  57                  */
  58                 s = (aa.sl[H] >> (LONG_BITS - 1)) >> 1;
  59                 aa.ul[L] = shift >= QUAD_BITS ? s :
  60                     aa.sl[H] >> (shift - LONG_BITS);
  61                 aa.ul[H] = s;
  62         } else if (shift > 0) {
  63                 aa.ul[L] = (aa.ul[L] >> shift) |
  64                     (aa.ul[H] << (LONG_BITS - shift));
  65                 aa.sl[H] >>= shift;
  66         }
  67         return (aa.q);
  68 }