mirror of
https://github.com/LadybirdBrowser/ladybird.git
synced 2024-11-21 23:20:20 +00:00
2af028132a
Doesn't use them in libc headers so that those don't have to pull in AK/Platform.h. AK_COMPILER_GCC is set _only_ for gcc, not for clang too. (__GNUC__ is defined in clang builds as well.) Using AK_COMPILER_GCC simplifies things some. AK_COMPILER_CLANG isn't as much of a win, other than that it's consistent with AK_COMPILER_GCC.
131 lines
4.5 KiB
C++
131 lines
4.5 KiB
C++
/*
|
|
* Copyright (c) 2021, Nick Johnson <sylvyrfysh@gmail.com>
|
|
*
|
|
* SPDX-License-Identifier: BSD-2-Clause
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include "Concepts.h"
|
|
|
|
template<Unsigned IntType>
|
|
inline constexpr int popcount(IntType value)
|
|
{
|
|
#if defined(AK_COMPILER_CLANG) || defined(AK_COMPILER_GCC)
|
|
static_assert(sizeof(IntType) <= sizeof(unsigned long long));
|
|
if constexpr (sizeof(IntType) <= sizeof(unsigned int))
|
|
return __builtin_popcount(value);
|
|
if constexpr (sizeof(IntType) == sizeof(unsigned long))
|
|
return __builtin_popcountl(value);
|
|
if constexpr (sizeof(IntType) == sizeof(unsigned long long))
|
|
return __builtin_popcountll(value);
|
|
VERIFY_NOT_REACHED();
|
|
#else
|
|
int ones = 0;
|
|
for (size_t i = 0; i < 8 * sizeof(IntType); ++i) {
|
|
if ((value >> i) & 1) {
|
|
++ones;
|
|
}
|
|
}
|
|
return ones;
|
|
#endif
|
|
}
|
|
|
|
// The function will return the number of trailing zeroes in the type. If
|
|
// the given number if zero, this function may contain undefined
|
|
// behavior, or it may return the number of bits in the number. If
|
|
// this function can be called with zero, the use of
|
|
// count_trailing_zeroes_safe is preferred.
|
|
template<Unsigned IntType>
|
|
inline constexpr int count_trailing_zeroes(IntType value)
|
|
{
|
|
#if defined(AK_COMPILER_CLANG) || defined(AK_COMPILER_GCC)
|
|
static_assert(sizeof(IntType) <= sizeof(unsigned long long));
|
|
if constexpr (sizeof(IntType) <= sizeof(unsigned int))
|
|
return __builtin_ctz(value);
|
|
if constexpr (sizeof(IntType) == sizeof(unsigned long))
|
|
return __builtin_ctzl(value);
|
|
if constexpr (sizeof(IntType) == sizeof(unsigned long long))
|
|
return __builtin_ctzll(value);
|
|
VERIFY_NOT_REACHED();
|
|
#else
|
|
for (size_t i = 0; i < 8 * sizeof(IntType); ++i) {
|
|
if ((value >> i) & 1) {
|
|
return i;
|
|
}
|
|
}
|
|
return 8 * sizeof(IntType);
|
|
#endif
|
|
}
|
|
|
|
// The function will return the number of trailing zeroes in the type. If
|
|
// the given number is zero, this function will return the number of bits
|
|
// bits in the IntType.
|
|
template<Unsigned IntType>
|
|
inline constexpr int count_trailing_zeroes_safe(IntType value)
|
|
{
|
|
if (value == 0)
|
|
return 8 * sizeof(IntType);
|
|
return count_trailing_zeroes(value);
|
|
}
|
|
|
|
// The function will return the number of leading zeroes in the type. If
|
|
// the given number if zero, this function may contain undefined
|
|
// behavior, or it may return the number of bits in the number. If
|
|
// this function can be called with zero, the use of
|
|
// count_leading_zeroes_safe is preferred.
|
|
template<Unsigned IntType>
|
|
inline constexpr int count_leading_zeroes(IntType value)
|
|
{
|
|
#if defined(AK_COMPILER_CLANG) || defined(AK_COMPILER_GCC)
|
|
static_assert(sizeof(IntType) <= sizeof(unsigned long long));
|
|
if constexpr (sizeof(IntType) <= sizeof(unsigned int))
|
|
return __builtin_clz(value) - (32 - (8 * sizeof(IntType)));
|
|
if constexpr (sizeof(IntType) == sizeof(unsigned long))
|
|
return __builtin_clzl(value);
|
|
if constexpr (sizeof(IntType) == sizeof(unsigned long long))
|
|
return __builtin_clzll(value);
|
|
VERIFY_NOT_REACHED();
|
|
#else
|
|
// Wrap around, catch going past zero by noticing that i is greater than the number of bits in the number
|
|
for (size_t i = (8 * sizeof(IntType)) - 1; i < 8 * sizeof(IntType); --i) {
|
|
if ((value >> i) & 1) {
|
|
return i;
|
|
}
|
|
}
|
|
return 8 * sizeof(IntType);
|
|
#endif
|
|
}
|
|
|
|
// The function will return the number of leading zeroes in the type. If
|
|
// the given number is zero, this function will return the number of bits
|
|
// in the IntType.
|
|
template<Unsigned IntType>
|
|
inline constexpr int count_leading_zeroes_safe(IntType value)
|
|
{
|
|
if (value == 0)
|
|
return 8 * sizeof(IntType);
|
|
return count_leading_zeroes(value);
|
|
}
|
|
|
|
// The function will return the number of leading zeroes in the type. If
|
|
// the given number is zero, this function will return the number of bits
|
|
// in the IntType.
|
|
template<Integral IntType>
|
|
inline constexpr int bit_scan_forward(IntType value)
|
|
{
|
|
#if defined(AK_COMPILER_CLANG) || defined(AK_COMPILER_GCC)
|
|
static_assert(sizeof(IntType) <= sizeof(unsigned long long));
|
|
if constexpr (sizeof(IntType) <= sizeof(unsigned int))
|
|
return __builtin_ffs(value);
|
|
if constexpr (sizeof(IntType) == sizeof(unsigned long))
|
|
return __builtin_ffsl(value);
|
|
if constexpr (sizeof(IntType) == sizeof(unsigned long long))
|
|
return __builtin_ffsll(value);
|
|
VERIFY_NOT_REACHED();
|
|
#else
|
|
if (value == 0)
|
|
return 0;
|
|
return 1 + count_trailing_zeroes(static_cast<MakeUnsigned<IntType>>(value));
|
|
#endif
|
|
}
|