mirror of
https://github.com/LadybirdBrowser/ladybird.git
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08e4a1a4dc
In order to reduce our reliance on __builtin_{ffs, clz, ctz, popcount},
this commit removes all calls to these functions and replaces them with
the equivalent functions in AK/BuiltinWrappers.h.
132 lines
4.4 KiB
C++
132 lines
4.4 KiB
C++
/*
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* Copyright (c) 2021, Nick Johnson <sylvyrfysh@gmail.com>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include "Concepts.h"
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template<Unsigned IntType>
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inline constexpr int popcount(IntType value)
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{
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#if defined(__GNUC__) || defined(__clang__)
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static_assert(sizeof(IntType) <= sizeof(unsigned long long));
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if constexpr (sizeof(IntType) <= sizeof(unsigned int))
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return __builtin_popcount(value);
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if constexpr (sizeof(IntType) == sizeof(unsigned long))
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return __builtin_popcountl(value);
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if constexpr (sizeof(IntType) == sizeof(unsigned long long))
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return __builtin_popcountll(value);
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VERIFY_NOT_REACHED();
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#else
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int ones = 0;
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for (size_t i = 0; i < 8 * sizeof(IntType); ++i) {
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if ((val >> i) & 1) {
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++ones;
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}
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}
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return ones;
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#endif
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}
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// The function will return the number of trailing zeroes in the type. If
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// the given number if zero, this function may contain undefined
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// behavior, or it may return the number of bits in the number. If
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// this function can be called with zero, the use of
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// count_trailing_zeroes_safe is preferred.
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template<Unsigned IntType>
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inline constexpr int count_trailing_zeroes(IntType value)
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{
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#if defined(__GNUC__) || defined(__clang__)
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static_assert(sizeof(IntType) <= sizeof(unsigned long long));
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if constexpr (sizeof(IntType) <= sizeof(unsigned int))
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return __builtin_ctz(value);
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if constexpr (sizeof(IntType) == sizeof(unsigned long))
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return __builtin_ctzl(value);
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if constexpr (sizeof(IntType) == sizeof(unsigned long long))
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return __builtin_ctzll(value);
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VERIFY_NOT_REACHED();
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#else
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for (size_t i = 0; i < 8 * sizeof(IntType); ++i) {
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if ((val >> i) & 1) {
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return i;
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}
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}
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return 8 * sizeof(IntType);
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#endif
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}
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// The function will return the number of trailing zeroes in the type. If
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// the given number is zero, this function will return the number of bits
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// bits in the IntType.
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template<Unsigned IntType>
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inline constexpr int count_trailing_zeroes_safe(IntType value)
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{
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if (value == 0)
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return 8 * sizeof(IntType);
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return count_trailing_zeroes(value);
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}
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// The function will return the number of leading zeroes in the type. If
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// the given number if zero, this function may contain undefined
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// behavior, or it may return the number of bits in the number. If
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// this function can be called with zero, the use of
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// count_leading_zeroes_safe is preferred.
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template<Unsigned IntType>
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inline constexpr int count_leading_zeroes(IntType value)
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{
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#if defined(__GNUC__) || defined(__clang__)
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static_assert(sizeof(IntType) <= sizeof(unsigned long long));
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if constexpr (sizeof(IntType) <= sizeof(unsigned int))
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return __builtin_clz(value) - (32 - (8 * sizeof(IntType)));
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if constexpr (sizeof(IntType) == sizeof(unsigned long))
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return __builtin_clzl(value);
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if constexpr (sizeof(IntType) == sizeof(unsigned long long))
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return __builtin_clzll(value);
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VERIFY_NOT_REACHED();
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#else
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// Wrap around, catch going past zero by noticing that i is greater than the number of bits in the number
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for (size_t i = (8 * sizeof(IntType)) - 1; i < 8 * sizeof(IntType); --i) {
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if ((val >> i) & 1) {
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return i;
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}
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}
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return 8 * sizeof(IntType);
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#endif
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}
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// The function will return the number of leading zeroes in the type. If
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// the given number is zero, this function will return the number of bits
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// in the IntType.
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template<Unsigned IntType>
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inline constexpr int count_leading_zeroes_safe(IntType value)
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{
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if (value == 0)
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return 8 * sizeof(IntType);
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return count_leading_zeroes(value);
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}
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// The function will return the number of leading zeroes in the type. If
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// the given number is zero, this function will return the number of bits
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// in the IntType.
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template<Integral IntType>
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inline constexpr int bit_scan_forward(IntType value)
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{
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#if defined(__GNUC__) || defined(__clang__)
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static_assert(sizeof(IntType) <= sizeof(unsigned long long));
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if constexpr (sizeof(IntType) <= sizeof(unsigned int))
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return __builtin_ffs(value);
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if constexpr (sizeof(IntType) == sizeof(unsigned long))
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return __builtin_ffsl(value);
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if constexpr (sizeof(IntType) == sizeof(unsigned long long))
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return __builtin_ffsll(value);
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VERIFY_NOT_REACHED();
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#else
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if (value == 0)
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return 0;
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return 1 + count_trailing_zeroes(static_cast<MakeUnsigned<IntType>>(value));
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#endif
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}
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