common/lib/libc/string/popcount64.c

   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