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Common: Use C++20 <bit> header in BitSet.h

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This commit is contained in:
JosJuice
2022-12-18 16:51:32 +01:00
parent a1c4861ad8
commit 547d956278
3 changed files with 12 additions and 86 deletions
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82
Source/Core/Common/BitSet.h
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@ -2,89 +2,15 @@
#pragma once
#include <bit>
#include <cstddef>
#include <initializer_list>
#include <type_traits>
#include "Common/CommonTypes.h"
#ifdef _WIN32
#include <intrin.h>
namespace Common
{
template <typename T>
constexpr int CountSetBits(T v)
{
// from https://graphics.stanford.edu/~seander/bithacks.html
// GCC has this built in, but MSVC's intrinsic will only emit the actual
// POPCNT instruction, which we're not depending on
v = v - ((v >> 1) & (T) ~(T)0 / 3);
v = (v & (T) ~(T)0 / 15 * 3) + ((v >> 2) & (T) ~(T)0 / 15 * 3);
v = (v + (v >> 4)) & (T) ~(T)0 / 255 * 15;
return (T)(v * ((T) ~(T)0 / 255)) >> (sizeof(T) - 1) * 8;
}
inline int LeastSignificantSetBit(u8 val)
{
unsigned long index;
_BitScanForward(&index, val);
return (int)index;
}
inline int LeastSignificantSetBit(u16 val)
{
unsigned long index;
_BitScanForward(&index, val);
return (int)index;
}
inline int LeastSignificantSetBit(u32 val)
{
unsigned long index;
_BitScanForward(&index, val);
return (int)index;
}
inline int LeastSignificantSetBit(u64 val)
{
unsigned long index;
_BitScanForward64(&index, val);
return (int)index;
}
#else
namespace Common
{
constexpr int CountSetBits(u8 val)
{
return __builtin_popcount(val);
}
constexpr int CountSetBits(u16 val)
{
return __builtin_popcount(val);
}
constexpr int CountSetBits(u32 val)
{
return __builtin_popcount(val);
}
constexpr int CountSetBits(u64 val)
{
return __builtin_popcountll(val);
}
inline int LeastSignificantSetBit(u8 val)
{
return __builtin_ctz(val);
}
inline int LeastSignificantSetBit(u16 val)
{
return __builtin_ctz(val);
}
inline int LeastSignificantSetBit(u32 val)
{
return __builtin_ctz(val);
}
inline int LeastSignificantSetBit(u64 val)
{
return __builtin_ctzll(val);
}
#endif
// Similar to std::bitset, this is a class which encapsulates a bitset, i.e.
// using the set bits of an integer to represent a set of integers. Like that
// class, it acts like an array of bools:
@ -146,7 +72,7 @@ public:
}
else
{
int bit = LeastSignificantSetBit(m_val);
int bit = std::countr_zero(m_val);
m_val &= ~(1 << bit);
m_bit = bit;
}
@ -203,7 +129,7 @@ public:
// Dolphin's official builds do not currently assume POPCNT support on x86,
// so slower explicit bit twiddling is generated. Still should generally
// be faster than a loop.
constexpr unsigned int Count() const { return CountSetBits(m_val); }
constexpr unsigned int Count() const { return std::popcount(m_val); }
constexpr Iterator begin() const { return ++Iterator(m_val, 0); }
constexpr Iterator end() const { return Iterator(m_val, -1); }
IntTy m_val;