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62 lines
1.8 KiB
C++
62 lines
1.8 KiB
C++
// SPDX-FileCopyrightText: 2019-2022 Connor McLaughlin <stenzek@gmail.com>
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// SPDX-License-Identifier: (GPL-3.0 OR CC-BY-NC-ND-4.0)
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#pragma once
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#include "types.h"
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#ifdef _MSC_VER
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#include <intrin.h>
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#endif
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/// Returns the number of zero bits before the first set bit, going MSB->LSB.
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template<typename T>
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ALWAYS_INLINE unsigned CountLeadingZeros(T value)
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{
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#ifdef _MSC_VER
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if constexpr (sizeof(value) >= sizeof(u64))
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{
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unsigned long index;
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_BitScanReverse64(&index, ZeroExtend64(value));
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return static_cast<unsigned>(index) ^ static_cast<unsigned>((sizeof(value) * 8u) - 1u);
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}
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else
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{
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unsigned long index;
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_BitScanReverse(&index, ZeroExtend32(value));
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return static_cast<unsigned>(index) ^ static_cast<unsigned>((sizeof(value) * 8u) - 1u);
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}
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#else
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if constexpr (sizeof(value) >= sizeof(u64))
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return static_cast<unsigned>(__builtin_clzl(ZeroExtend64(value)));
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else if constexpr (sizeof(value) == sizeof(u32))
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return static_cast<unsigned>(__builtin_clz(ZeroExtend32(value)));
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else
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return static_cast<unsigned>(__builtin_clz(ZeroExtend32(value))) & static_cast<unsigned>((sizeof(value) * 8u) - 1u);
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#endif
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}
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/// Returns the number of zero bits before the first set bit, going LSB->MSB.
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template<typename T>
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ALWAYS_INLINE unsigned CountTrailingZeros(T value)
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{
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#ifdef _MSC_VER
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if constexpr (sizeof(value) >= sizeof(u64))
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{
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unsigned long index;
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_BitScanForward64(&index, ZeroExtend64(value));
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return index;
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}
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else
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{
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unsigned long index;
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_BitScanForward(&index, ZeroExtend32(value));
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return index;
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}
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#else
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if constexpr (sizeof(value) >= sizeof(u64))
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return static_cast<unsigned>(__builtin_ctzl(ZeroExtend64(value)));
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else
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return static_cast<unsigned>(__builtin_ctz(ZeroExtend32(value)));
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#endif
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}
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