FreeBSD/Linux Kernel Cross Reference
sys/mips/include/fls64.h

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * Copyright (c) 2003-2009 RMI Corporation
      * All rights reserved.
      *
      * 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 RMI Corporation, 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 AUTHOR 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 AUTHOR 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.
     *
     * $FreeBSD: releng/11.2/sys/mips/include/fls64.h 330897 2018-03-14 03:19:51Z eadler $
     * RMI_BSD */
    #ifndef _MIPS_FLS64_H_
    #define _MIPS_FLS64_H_
    
    /*
     * Find Last Set bit (64 bit)
     */
    static inline int
    fls64(__uint64_t mask)
    {
            int bit;
    
            if (mask == 0)
                    return (0);
            for (bit = 1; ((mask & 0x1ULL) == 0); bit++)
                    mask = mask >> 1;
            return (bit);
    }
    #endif

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