xref: /netbsd-src/common/lib/libc/string/popcount64.c (revision b1c86f5f087524e68db12794ee9c3e3da1ab17a0)
1 /*	$NetBSD: popcount64.c,v 1.5 2009/08/05 15:04:15 joerg Exp $	*/
2 /*-
3  * Copyright (c) 2009 The NetBSD Foundation, Inc.
4  * All rights reserved.
5  *
6  * This code is derived from software contributed to The NetBSD Foundation
7  * by Joerg Sonnenberger.
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  *
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in
17  *    the documentation and/or other materials provided with the
18  *    distribution.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
24  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
27  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
30  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  */
33 
34 #include <sys/cdefs.h>
35 __RCSID("$NetBSD: popcount64.c,v 1.5 2009/08/05 15:04:15 joerg Exp $");
36 
37 #if !defined(_KERNEL) && !defined(_STANDALONE)
38 #include <limits.h>
39 #include <strings.h>
40 #else
41 #include <lib/libkern/libkern.h>
42 #include <machine/limits.h>
43 #endif
44 
45 /*
46  * If uint64_t is larger than size_t, the follow assumes that
47  * splitting into 32bit halfes is faster.
48  *
49  * The native pocount64 version is based on the same ideas as popcount32(3),
50  * see popcount32.c for comments.
51  */
52 
53 #if SIZE_MAX < 0xffffffffffffffffULL
54 unsigned int
55 popcount64(uint64_t v)
56 {
57 	return popcount32((uint32_t)(v >> 32)) +
58 	    popcount32((uint32_t)(v & 0xffffffffULL));
59 }
60 #else
61 unsigned int
62 popcount64(uint64_t v)
63 {
64 	unsigned int c;
65 
66 	v = v - ((v >> 1) & 0x5555555555555555ULL);
67 	v = (v & 0x3333333333333333ULL) + ((v >> 2) & 0x3333333333333333ULL);
68 	v = ((v + (v >> 4)) & 0x0f0f0f0f0f0f0f0fULL) * 0x0101010101010101ULL;
69 	c = v >> 56;
70 
71 	return c;
72 }
73 #endif
74 
75 #if ULONG_MAX == 0xffffffffffffffffULL
76 __strong_alias(popcountl, popcount64)
77 #endif
78 
79 #if ULLONG_MAX == 0xffffffffffffffffULL
80 __strong_alias(popcountll, popcount64)
81 #endif
82 
83