ashrdi3.c revision 1.5 
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 * 3. 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#if defined(LIBC_SCCS) && !defined(lint)
35static char rcsid[] = "$OpenBSD: ashrdi3.c,v 1.5 2004/11/28 07:23:41 mickey Exp $";
36#endif /* LIBC_SCCS and not lint */
37
38#include "quad.h"
39
40/*
41 * Shift a (signed) quad value right (arithmetic shift right).
42 */
43quad_t
44__ashrdi3(quad_t a, qshift_t shift)
45{
46	union uu aa;
47
48	if (shift == 0)
49		return(a);
50	aa.q = a;
51	if (shift >= INT_BITS) {
52		int s;
53
54		/*
55		 * Smear bits rightward using the machine's right-shift
56		 * method, whether that is sign extension or zero fill,
57		 * to get the `sign word' s.  Note that shifting by
58		 * INT_BITS is undefined, so we shift (INT_BITS-1),
59		 * then 1 more, to get our answer.
60		 */
61		/* LINTED inherits machine dependency */
62		s = (aa.sl[H] >> (INT_BITS - 1)) >> 1;
63		/* LINTED inherits machine dependency*/
64		aa.ul[L] = aa.sl[H] >> (shift - INT_BITS);
65		aa.ul[H] = s;
66	} else {
67		aa.ul[L] = (aa.ul[L] >> shift) |
68		    (aa.ul[H] << (INT_BITS - shift));
69		/* LINTED inherits machine dependency */
70		aa.sl[H] >>= shift;
71	}
72	return (aa.q);
73}
74