Annotation of sys/lib/libkern/ashrdi3.c, Revision 1.1.1.1
1.1 nbrk 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)
35: static 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: */
43: quad_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: }
CVSweb