bitscanintrinsics.h

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/*  This file is part of the Vc library.

    Copyright (C) 2011-2012 Matthias Kretz <kretz@kde.org>

    Vc is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as
    published by the Free Software Foundation, either version 3 of
    the License, or (at your option) any later version.

    Vc is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with Vc.  If not, see <http://www.gnu.org/licenses/>.

*/

#ifndef VC_COMMON_BITSCANINTRINSICS_H
#define VC_COMMON_BITSCANINTRINSICS_H

#if defined(VC_GCC) || defined(VC_CLANG)
#  if VC_GCC >= 0x40500
     // GCC 4.5.0 introduced _bit_scan_forward / _bit_scan_reverse
#    include <x86intrin.h>
#  else
     // GCC <= 4.4 and clang have x86intrin.h, but not the required functions
#    define _bit_scan_forward(x) __builtin_ctz(x)
#include "macros.h"
static Vc_ALWAYS_INLINE Vc_CONST int _Vc_bit_scan_reverse_asm(unsigned int x) {
    int r;
    __asm__("bsr %1,%0" : "=r"(r) : "X"(x));
    return r;
}
#include "undomacros.h"
#    define _bit_scan_reverse(x) _Vc_bit_scan_reverse_asm(x)
#  endif
#elif defined(VC_ICC)
// for all I know ICC supports the _bit_scan_* intrinsics
#elif defined(VC_OPEN64)
// TODO
#elif defined(VC_MSVC)
#include "windows_fix_intrin.h"
#pragma intrinsic(_BitScanForward)
#pragma intrinsic(_BitScanReverse)
static inline __forceinline unsigned long _bit_scan_forward(unsigned long x) {
    unsigned long index;
    _BitScanForward(&index, x);
    return index;
}
static inline __forceinline unsigned long _bit_scan_reverse(unsigned long x) {
    unsigned long index;
    _BitScanReverse(&index, x);
    return index;
}
#else
// just assume the compiler can do it
#endif


#endif // VC_COMMON_BITSCANINTRINSICS_H