1/*	$NetBSD: popcount64.c,v 1.7 2012/03/09 15:41:16 christos 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 1.7 2012/03/09 15:41:16 christos Exp $");
36
37#if !defined(_KERNEL) && !defined(_STANDALONE)
38#include <limits.h>
39#include <stdint.h>
40#include <strings.h>
41#else
42#include <lib/libkern/libkern.h>
43#include <machine/limits.h>
44#endif
45
46#ifndef popcount64	// might be defined to use a __builtin
47
48/*
49 * If uint64_t is larger than size_t, the follow assumes that
50 * splitting into 32bit halves is faster.
51 *
52 * The native pocount64 version is based on the same ideas as popcount32(3),
53 * see popcount32.c for comments.
54 */
55
56#if SIZE_MAX < 0xffffffffffffffffULL
57unsigned int
58popcount64(uint64_t v)
59{
60	return popcount32((uint32_t)(v >> 32)) +
61	    popcount32((uint32_t)(v & 0xffffffffULL));
62}
63#else
64unsigned int
65popcount64(uint64_t v)
66{
67	unsigned int c;
68
69	v = v - ((v >> 1) & (uint64_t)0x5555555555555555ULL);
70	v = (v & (uint64_t)0x3333333333333333ULL) +
71	    ((v >> 2) & (uint64_t)0x3333333333333333ULL);
72	v = ((v + (v >> 4)) & (uint64_t)0x0f0f0f0f0f0f0f0fULL) *
73	    (uint64_t)0x0101010101010101ULL;
74	c = (unsigned int)(v >> 56);
75
76	return c;
77}
78#endif
79
80#if ULONG_MAX == 0xffffffffffffffffULL
81__strong_alias(popcountl, popcount64)
82#endif
83
84#if ULLONG_MAX == 0xffffffffffffffffULL
85__strong_alias(popcountll, popcount64)
86#endif
87
88#endif /* !popcount64 */
89