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common: Remove bit_set.h

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This is an analog of BitSet from Dolphin that was introduced to allow
iterating over a set of bits. Given it's currently unused, and given
that std::bitset exists, we can remove this. If it's ever needed in the
future it can be brought back.
This commit is contained in:
Lioncash 2018-11-21 21:29:39 -05:00
parent ec38b4e883
commit 8b27e73bd7
2 changed files with 0 additions and 245 deletions
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1
src/common/CMakeLists.txt
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@ -44,7 +44,6 @@ add_library(common STATIC
detached_tasks.cpp detached_tasks.cpp
detached_tasks.h detached_tasks.h
bit_field.h bit_field.h
bit_set.h
cityhash.cpp cityhash.cpp
cityhash.h cityhash.h
color.h color.h

244
src/common/bit_set.h
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@ -1,244 +0,0 @@
// This file is under the public domain.
#pragma once
#include <cstddef>
#ifdef _WIN32
#include <intrin.h>
#endif
#include <initializer_list>
#include <new>
#include <type_traits>
#include "common/common_types.h"
// namespace avoids conflict with OS X Carbon; don't use BitSet<T> directly
namespace Common {
// Helper functions:
#ifdef _MSC_VER
template <typename T>
static inline 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;
}
static inline int LeastSignificantSetBit(u8 val) {
unsigned long index;
_BitScanForward(&index, val);
return (int)index;
}
static inline int LeastSignificantSetBit(u16 val) {
unsigned long index;
_BitScanForward(&index, val);
return (int)index;
}
static inline int LeastSignificantSetBit(u32 val) {
unsigned long index;
_BitScanForward(&index, val);
return (int)index;
}
static inline int LeastSignificantSetBit(u64 val) {
unsigned long index;
_BitScanForward64(&index, val);
return (int)index;
}
#else
static inline int CountSetBits(u8 val) {
return __builtin_popcount(val);
}
static inline int CountSetBits(u16 val) {
return __builtin_popcount(val);
}
static inline int CountSetBits(u32 val) {
return __builtin_popcount(val);
}
static inline int CountSetBits(u64 val) {
return __builtin_popcountll(val);
}
static inline int LeastSignificantSetBit(u8 val) {
return __builtin_ctz(val);
}
static inline int LeastSignificantSetBit(u16 val) {
return __builtin_ctz(val);
}
static inline int LeastSignificantSetBit(u32 val) {
return __builtin_ctz(val);
}
static 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:
// BitSet32 bs;
// bs[1] = true;
// but also like the underlying integer ([0] = least significant bit):
// BitSet32 bs2 = ...;
// bs = (bs ^ bs2) & BitSet32(0xffff);
// The following additional functionality is provided:
// - Construction using an initializer list.
// BitSet bs { 1, 2, 4, 8 };
// - Efficiently iterating through the set bits:
// for (int i : bs)
// [i is the *index* of a set bit]
// (This uses the appropriate CPU instruction to find the next set bit in one
// operation.)
// - Counting set bits using .Count() - see comment on that method.
// TODO: use constexpr when MSVC gets out of the Dark Ages
template <typename IntTy>
class BitSet {
static_assert(!std::is_signed_v<IntTy>, "BitSet should not be used with signed types");
public:
// A reference to a particular bit, returned from operator[].
class Ref {
public:
Ref(Ref&& other) : m_bs(other.m_bs), m_mask(other.m_mask) {}
Ref(BitSet* bs, IntTy mask) : m_bs(bs), m_mask(mask) {}
operator bool() const {
return (m_bs->m_val & m_mask) != 0;
}
bool operator=(bool set) {
m_bs->m_val = (m_bs->m_val & ~m_mask) | (set ? m_mask : 0);
return set;
}
private:
BitSet* m_bs;
IntTy m_mask;
};
// A STL-like iterator is required to be able to use range-based for loops.
class Iterator {
public:
Iterator(const Iterator& other) : m_val(other.m_val), m_bit(other.m_bit) {}
Iterator(IntTy val) : m_val(val), m_bit(0) {}
Iterator& operator=(Iterator other) {
new (this) Iterator(other);
return *this;
}
int operator*() {
return m_bit + ComputeLsb();
}
Iterator& operator++() {
int lsb = ComputeLsb();
m_val >>= lsb + 1;
m_bit += lsb + 1;
m_has_lsb = false;
return *this;
}
Iterator operator++(int _) {
Iterator other(*this);
++*this;
return other;
}
bool operator==(Iterator other) const {
return m_val == other.m_val;
}
bool operator!=(Iterator other) const {
return m_val != other.m_val;
}
private:
int ComputeLsb() {
if (!m_has_lsb) {
m_lsb = LeastSignificantSetBit(m_val);
m_has_lsb = true;
}
return m_lsb;
}
IntTy m_val;
int m_bit;
int m_lsb = -1;
bool m_has_lsb = false;
};
BitSet() : m_val(0) {}
explicit BitSet(IntTy val) : m_val(val) {}
BitSet(std::initializer_list<int> init) {
m_val = 0;
for (int bit : init)
m_val |= (IntTy)1 << bit;
}
static BitSet AllTrue(std::size_t count) {
return BitSet(count == sizeof(IntTy) * 8 ? ~(IntTy)0 : (((IntTy)1 << count) - 1));
}
Ref operator[](std::size_t bit) {
return Ref(this, (IntTy)1 << bit);
}
const Ref operator[](std::size_t bit) const {
return (*const_cast<BitSet*>(this))[bit];
}
bool operator==(BitSet other) const {
return m_val == other.m_val;
}
bool operator!=(BitSet other) const {
return m_val != other.m_val;
}
bool operator<(BitSet other) const {
return m_val < other.m_val;
}
bool operator>(BitSet other) const {
return m_val > other.m_val;
}
BitSet operator|(BitSet other) const {
return BitSet(m_val | other.m_val);
}
BitSet operator&(BitSet other) const {
return BitSet(m_val & other.m_val);
}
BitSet operator^(BitSet other) const {
return BitSet(m_val ^ other.m_val);
}
BitSet operator~() const {
return BitSet(~m_val);
}
BitSet& operator|=(BitSet other) {
return *this = *this | other;
}
BitSet& operator&=(BitSet other) {
return *this = *this & other;
}
BitSet& operator^=(BitSet other) {
return *this = *this ^ other;
}
operator u32() = delete;
operator bool() {
return m_val != 0;
}
// Warning: Even though on modern CPUs this is a single fast instruction,
// 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.
unsigned int Count() const {
return CountSetBits(m_val);
}
Iterator begin() const {
return Iterator(m_val);
}
Iterator end() const {
return Iterator(0);
}
IntTy m_val;
};
} // namespace Common
typedef Common::BitSet<u8> BitSet8;
typedef Common::BitSet<u16> BitSet16;
typedef Common::BitSet<u32> BitSet32;
typedef Common::BitSet<u64> BitSet64;