4684ddb6aa
- import libcxx - reduce targets to the one when compiled as a tools Change-Id: Iabb8427f80ff8e89463559a28bcb8b4f2bdbc496
78 lines
2.6 KiB
C
78 lines
2.6 KiB
C
/* $NetBSD: popcount32.c,v 1.4 2011/08/21 21:25:04 dholland Exp $ */
|
|
/*-
|
|
* Copyright (c) 2009 The NetBSD Foundation, Inc.
|
|
* All rights reserved.
|
|
*
|
|
* This code is derived from software contributed to The NetBSD Foundation
|
|
* by Joerg Sonnenberger.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
*
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in
|
|
* the documentation and/or other materials provided with the
|
|
* distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
|
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
|
* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
* INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
|
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
|
|
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
|
|
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
|
|
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
|
|
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*/
|
|
|
|
#include <sys/cdefs.h>
|
|
__RCSID("$NetBSD: popcount32.c,v 1.4 2011/08/21 21:25:04 dholland Exp $");
|
|
|
|
#if !defined(_KERNEL) && !defined(_STANDALONE)
|
|
#include <limits.h>
|
|
#include <stdint.h>
|
|
#include <strings.h>
|
|
#else
|
|
#include <lib/libkern/libkern.h>
|
|
#include <machine/limits.h>
|
|
#endif
|
|
|
|
/*
|
|
* This a hybrid algorithm for bit counting between parallel counting and
|
|
* using multiplication. The idea is to sum up the bits in each Byte, so
|
|
* that the final accumulation can be done with a single multiplication.
|
|
* If the platform has a slow multiplication instruction, it can be replaced
|
|
* by the commented out version below.
|
|
*/
|
|
|
|
unsigned int
|
|
popcount32(uint32_t v)
|
|
{
|
|
unsigned int c;
|
|
|
|
v = v - ((v >> 1) & 0x55555555U);
|
|
v = (v & 0x33333333U) + ((v >> 2) & 0x33333333U);
|
|
v = (v + (v >> 4)) & 0x0f0f0f0fU;
|
|
c = (v * 0x01010101U) >> 24;
|
|
/*
|
|
* v = (v >> 16) + v;
|
|
* v = (v >> 8) + v;
|
|
* c = v & 255;
|
|
*/
|
|
|
|
return c;
|
|
}
|
|
|
|
#if UINT_MAX == 0xffffffffU
|
|
__strong_alias(popcount, popcount32)
|
|
#endif
|
|
|
|
#if ULONG_MAX == 0xffffffffU
|
|
__strong_alias(popcountl, popcount32)
|
|
#endif
|