common/lib/libc/quad/ashrdi3.c

   1 /*      $NetBSD: ashrdi3.c,v 1.1 2005/12/20 19:28:51 christos Exp $     */
   2
   3 /*-
   4  * Copyright (c) 1992, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This software was developed by the Computer Systems Engineering group
   8  * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
   9  * contributed to Berkeley.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 #include <sys/cdefs.h>
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 #if 0
  39 static char sccsid[] = "@(#)ashrdi3.c   8.1 (Berkeley) 6/4/93";
  40 #else
  41 __RCSID("$NetBSD: ashrdi3.c,v 1.1 2005/12/20 19:28:51 christos Exp $");
  42 #endif
  43 #endif /* LIBC_SCCS and not lint */
  44
  45 #include "quad.h"
  46
  47 /*
  48  * Shift a (signed) quad value right (arithmetic shift right).
  49  */
  50 quad_t
  51 __ashrdi3(quad_t a, qshift_t shift)
  52 {
  53         union uu aa;
  54
  55         if (shift == 0)
  56                 return(a);
  57         aa.q = a;
  58         if (shift >= INT_BITS) {
  59                 int s;
  60
  61                 /*
  62                  * Smear bits rightward using the machine's right-shift
  63                  * method, whether that is sign extension or zero fill,
  64                  * to get the `sign word' s.  Note that shifting by
  65                  * INT_BITS is undefined, so we shift (INT_BITS-1),
  66                  * then 1 more, to get our answer.
  67                  */
  68                 /* LINTED inherits machine dependency */
  69                 s = (aa.sl[H] >> (INT_BITS - 1)) >> 1;
  70                 /* LINTED inherits machine dependency*/
  71                 aa.ul[L] = aa.sl[H] >> (shift - INT_BITS);
  72                 aa.ul[H] = s;
  73         } else {
  74                 aa.ul[L] = (aa.ul[L] >> shift) |
  75                     (aa.ul[H] << (INT_BITS - shift));
  76                 /* LINTED inherits machine dependency */
  77                 aa.sl[H] >>= shift;
  78         }
  79         return (aa.q);
  80 }