usr/src/lib/libc/port/fp/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
  34 #pragma ident   "%Z%%M% %I%     %E% SMI"
  35
  36 #include "quadint.h"
  37
  38 #pragma weak __ashrdi3 = ___ashrdi3
  39
  40 /*
  41  * Shift a (signed) quad value right (arithmetic shift right).
  42  */
  43 longlong_t
  44 ___ashrdi3(longlong_t a, qshift_t shift)
  45 {
  46         union uu aa;
  47
  48         aa.q = a;
  49         if (shift >= LONG_BITS) {
  50                 long s;
  51
  52                 /*
  53                  * Smear bits rightward using the machine's right-shift
  54                  * method, whether that is sign extension or zero fill,
  55                  * to get the `sign word' s.  Note that shifting by
  56                  * LONG_BITS is undefined, so we shift (LONG_BITS-1),
  57                  * then 1 more, to get our answer.
  58                  */
  59                 s = (aa.sl[H] >> (LONG_BITS - 1)) >> 1;
  60                 aa.ul[L] = shift >= QUAD_BITS ? s :
  61                     aa.sl[H] >> (shift - LONG_BITS);
  62                 aa.ul[H] = s;
  63         } else if (shift > 0) {
  64                 aa.ul[L] = (aa.ul[L] >> shift) |
  65                     (aa.ul[H] << (LONG_BITS - shift));
  66                 aa.sl[H] >>= shift;
  67         }
  68         return (aa.q);
  69 }