cpython/Modules/_decimal/libmpdec/bits.h

/*
 * Copyright (c) 2008-2020 Stefan Krah. 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.
 *
 * 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.
 */


#ifndef LIBMPDEC_BITS_H_
#define LIBMPDEC_BITS_H_


#include "mpdecimal.h"


/* Check if n is a power of 2. */
static inline int
ispower2(mpd_size_t n)
{ … }

#if defined(ANSI)
/*
 * Return the most significant bit position of n from 0 to 31 (63).
 * Assumptions: n != 0.
 */
static inline int
mpd_bsr(mpd_size_t n)
{ … }

/*
 * Return the least significant bit position of n from 0 to 31 (63).
 * Assumptions: n != 0.
 */
static inline int
mpd_bsf(mpd_size_t n)
{ … }
/* END ANSI */

#elif defined(ASM)
/*
 * Bit scan reverse. Assumptions: a != 0.
 */
static inline int
mpd_bsr(mpd_size_t a)
{
    mpd_size_t retval;

    __asm__ (
#ifdef CONFIG_64
        "bsrq %1, %0\n\t"
#else
        "bsr %1, %0\n\t"
#endif
        :"=r" (retval)
        :"r" (a)
        :"cc"
    );

    return (int)retval;
}

/*
 * Bit scan forward. Assumptions: a != 0.
 */
static inline int
mpd_bsf(mpd_size_t a)
{
    mpd_size_t retval;

    __asm__ (
#ifdef CONFIG_64
        "bsfq %1, %0\n\t"
#else
        "bsf %1, %0\n\t"
#endif
        :"=r" (retval)
        :"r" (a)
        :"cc"
    );

    return (int)retval;
}
/* END ASM */

#elif defined(MASM)
#include <intrin.h>
/*
 * Bit scan reverse. Assumptions: a != 0.
 */
static inline int __cdecl
mpd_bsr(mpd_size_t a)
{
    unsigned long retval;

#ifdef CONFIG_64
    _BitScanReverse64(&retval, a);
#else
    _BitScanReverse(&retval, a);
#endif

    return (int)retval;
}

/*
 * Bit scan forward. Assumptions: a != 0.
 */
static inline int __cdecl
mpd_bsf(mpd_size_t a)
{
    unsigned long retval;

#ifdef CONFIG_64
    _BitScanForward64(&retval, a);
#else
    _BitScanForward(&retval, a);
#endif

    return (int)retval;
}
/* END MASM (_MSC_VER) */
#else
  #error "missing preprocessor definitions"
#endif /* BSR/BSF */


#endif /* LIBMPDEC_BITS_H_ */