FreeBSD/Linux Kernel Cross Reference
sys/sys/bitcount.h

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * Copyright (c) 1982, 1986, 1991, 1993, 1994
      *      The Regents of the University of California.  All rights reserved.
      * (c) UNIX System Laboratories, Inc.
      * All or some portions of this file are derived from material licensed
      * to the University of California by American Telephone and Telegraph
      * Co. or Unix System Laboratories, Inc. and are reproduced herein with
     * the permission of UNIX System Laboratories, Inc.
     *
     * 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.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
     *
     *      @(#)types.h     8.6 (Berkeley) 2/19/95
     * $FreeBSD$
     */
    
    #ifndef _SYS_BITCOUNT_H_
    #define _SYS_BITCOUNT_H_
    
    #include <sys/_types.h>
    
    #ifdef __POPCNT__
    #define __bitcount64(x) __builtin_popcountll((__uint64_t)(x))
    #define __bitcount32(x) __builtin_popcount((__uint32_t)(x))
    #define __bitcount16(x) __builtin_popcount((__uint16_t)(x))
    #define __bitcountl(x)  __builtin_popcountl((unsigned long)(x))
    #define __bitcount(x)   __builtin_popcount((unsigned int)(x))
    #else
    /*
     * Population count algorithm using SWAR approach
     * - "SIMD Within A Register".
     */
    static __inline __uint16_t
    __bitcount16(__uint16_t _x)
    {
    
            _x = (_x & 0x5555) + ((_x & 0xaaaa) >> 1);
            _x = (_x & 0x3333) + ((_x & 0xcccc) >> 2);
            _x = (_x + (_x >> 4)) & 0x0f0f;
            _x = (_x + (_x >> 8)) & 0x00ff;
            return (_x);
    }
    
    static __inline __uint32_t
    __bitcount32(__uint32_t _x)
    {
    
            _x = (_x & 0x55555555) + ((_x & 0xaaaaaaaa) >> 1);
            _x = (_x & 0x33333333) + ((_x & 0xcccccccc) >> 2);
            _x = (_x + (_x >> 4)) & 0x0f0f0f0f;
            _x = (_x + (_x >> 8));
            _x = (_x + (_x >> 16)) & 0x000000ff;
            return (_x);
    }
    
    #ifdef __LP64__
    static __inline __uint64_t
    __bitcount64(__uint64_t _x)
    {
    
            _x = (_x & 0x5555555555555555) + ((_x & 0xaaaaaaaaaaaaaaaa) >> 1);
            _x = (_x & 0x3333333333333333) + ((_x & 0xcccccccccccccccc) >> 2);
            _x = (_x + (_x >> 4)) & 0x0f0f0f0f0f0f0f0f;
            _x = (_x + (_x >> 8));
            _x = (_x + (_x >> 16));
            _x = (_x + (_x >> 32)) & 0x000000ff;
            return (_x);
    }
    
    #define __bitcountl(x)  __bitcount64((unsigned long)(x))
    #else
    static __inline __uint64_t
    __bitcount64(__uint64_t _x)
    {
    
            return (__bitcount32(_x >> 32) + __bitcount32(_x));
   }
   
   #define __bitcountl(x)  __bitcount32((unsigned long)(x))
   #endif
   #define __bitcount(x)   __bitcount32((unsigned int)(x))
   #endif
   
   #endif /* !_SYS_BITCOUNT_H_ */

Cache object: e36c20ab417b955fa63b3881760d58f4