70 lines
2.0 KiB
C
70 lines
2.0 KiB
C
/*
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* Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip.
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* All rights reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include <config.h>
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#include <assert.h>
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#include "roken.h"
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#if defined(_MSC_VER)
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#include <intrin.h>
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#if defined(_WIN64)
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#pragma intrinsic(_BitScanReverse64)
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#else
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#pragma intrinsic(_BitScanReverse)
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#endif
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#endif
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ROKEN_LIB_FUNCTION int ROKEN_LIB_CALL
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rk_clzll(uint64_t x)
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{
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#if defined(_MSC_VER)
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unsigned long r = 0;
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#elif !(defined(__GNUC__) && __GNUC__ >= 4)
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int r = 0;
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#endif
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assert(x != 0);
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#if defined(_MSC_VER)
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# if defined(_WIN64)
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_BitScanReverse64(&r, x);
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# else
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if (_BitScanReverse(&r, (uint32_t)(x >> 32)))
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return 63 - (r + 32);
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_BitScanReverse(&r, (uint32_t)(x & 0xFFFFFFFF));
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# endif
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return 63 - r;
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#elif (defined(__GNUC__) && __GNUC__ >= 4)
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return __builtin_clzll(x);
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#else
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while (!(x & ((uint64_t)1 << 63))) {
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x <<= 1;
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++r;
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}
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return r;
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#endif /* _MSC_VER || __GNUC__ */
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}
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