xref: /freebsd/lib/libc/quad/ashrdi3.c (revision c17d43407fe04133a94055b0dbc7ea8965654a9f)
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. All advertising materials mentioning features or use of this software
18  *    must display the following acknowledgement:
19  *	This product includes software developed by the University of
20  *	California, Berkeley and its contributors.
21  * 4. Neither the name of the University nor the names of its contributors
22  *    may be used to endorse or promote products derived from this software
23  *    without specific prior written permission.
24  *
25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35  * SUCH DAMAGE.
36  */
37 
38 #if defined(LIBC_SCCS) && !defined(lint)
39 static char sccsid[] = "@(#)ashrdi3.c	8.1 (Berkeley) 6/4/93";
40 #endif /* LIBC_SCCS and not lint */
41 #include <sys/cdefs.h>
42 __FBSDID("$FreeBSD$");
43 
44 #include "quad.h"
45 
46 /*
47  * Shift a (signed) quad value right (arithmetic shift right).
48  */
49 quad_t
50 __ashrdi3(a, shift)
51 	quad_t a;
52 	qshift_t shift;
53 {
54 	union uu aa;
55 
56 	aa.q = a;
57 	if (shift >= LONG_BITS) {
58 		long s;
59 
60 		/*
61 		 * Smear bits rightward using the machine's right-shift
62 		 * method, whether that is sign extension or zero fill,
63 		 * to get the `sign word' s.  Note that shifting by
64 		 * LONG_BITS is undefined, so we shift (LONG_BITS-1),
65 		 * then 1 more, to get our answer.
66 		 */
67 		s = (aa.sl[H] >> (LONG_BITS - 1)) >> 1;
68 		aa.ul[L] = shift >= QUAD_BITS ? s :
69 		    aa.sl[H] >> (shift - LONG_BITS);
70 		aa.ul[H] = s;
71 	} else if (shift > 0) {
72 		aa.ul[L] = (aa.ul[L] >> shift) |
73 		    (aa.ul[H] << (LONG_BITS - shift));
74 		aa.sl[H] >>= shift;
75 	}
76 	return (aa.q);
77 }
78