58 lines
1.4 KiB
C
58 lines
1.4 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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* Licensed under the MIT License (the "License"); you may not use this file except
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* in compliance with the License. You may obtain a copy of the License at
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*
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* http://opensource.org/licenses/MIT
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*
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* Unless required by applicable law or agreed to in writing, software distributed
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* under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
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* CONDITIONS OF ANY KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations under the License.
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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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assert(x != 0);
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#if defined(_MSC_VER)
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unsigned long r = 0;
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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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int r = 0;
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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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