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util: update some bit utility logic

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This commit is contained in:
Michael Scire 2022-04-03 10:51:46 -07:00
parent d7f89a0c31
commit 442656899f
3 changed files with 102 additions and 130 deletions
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131
libraries/libvapours/include/vapours/util/util_bitutil.hpp
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@ -30,108 +30,91 @@ namespace ams::util {
}
template <typename T> requires std::integral<T>
class BitsOf {
private:
static constexpr ALWAYS_INLINE int GetLsbPos(T v) {
return __builtin_ctzll(static_cast<u64>(v));
}
template<std::integral T>
constexpr inline T ReverseBits(T x, int sw_bits = 1, int swar_words = 1) {
/* Check pre-conditions. */
AMS_ASSERT(0 <= swar_words && swar_words < (BITSIZEOF(T) + 1));
AMS_ASSERT(BITSIZEOF(T) % swar_words == 0);
AMS_ASSERT(0 <= sw_bits && sw_bits < ((BITSIZEOF(T) / swar_words) + 1));
AMS_ASSERT((BITSIZEOF(T) / swar_words) % sw_bits == 0);
T m_value;
public:
/* Note: GCC has a bug in constant-folding here. Workaround: wrap entire caller with constexpr. */
constexpr ALWAYS_INLINE BitsOf(T value = T(0u)) : m_value(value) {
/* ... */
}
using U = typename std::make_unsigned<T>::type;
const int word_size = BITSIZEOF(T) / swar_words;
const int k = word_size - sw_bits;
constexpr ALWAYS_INLINE bool operator==(const BitsOf &other) const {
return m_value == other.m_value;
}
U u = std::bit_cast<U, T>(x);
for (int i = 1; i < BITSIZEOF(T); i <<= 1) {
const U mask = static_cast<U>(static_cast<U>(-1) / ((static_cast<U>(1) << i) + 1));
constexpr ALWAYS_INLINE bool operator!=(const BitsOf &other) const {
return m_value != other.m_value;
if (k & i) {
u = static_cast<U>(((u & mask) << i) | ((u & static_cast<U>(~mask)) >> i));
}
}
constexpr ALWAYS_INLINE int operator*() const {
return GetLsbPos(m_value);
}
return std::bit_cast<T, U>(u);
}
constexpr ALWAYS_INLINE BitsOf &operator++() {
m_value &= ~(T(1u) << GetLsbPos(m_value));
return *this;
}
constexpr ALWAYS_INLINE BitsOf &operator++(int) {
BitsOf ret(m_value);
++(*this);
return ret;
}
constexpr ALWAYS_INLINE BitsOf begin() const {
return *this;
}
constexpr ALWAYS_INLINE BitsOf end() const {
return BitsOf(T(0u));
}
};
template<std::integral T>
constexpr ALWAYS_INLINE T ReverseBytes(T x, int sw_bytes = 1, int swar_words = 1) {
return ReverseBits(x, sw_bytes * BITSIZEOF(u8), swar_words);
}
template<typename T = u64, typename ...Args> requires std::integral<T>
constexpr ALWAYS_INLINE T CombineBits(Args... args) {
return (... | (T(1u) << args));
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE T ResetLeastSignificantOneBit(T x) {
return x & (x - 1);
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE T SetLeastSignificantZeroBit(T x) {
return x | (x + 1);
}
template<typename T> requires std::integral<T>
constexpr ALWAYS_INLINE T LeastSignificantOneBit(T x) {
return x & ~(x - 1);
}
template<typename T> requires std::integral<T>
constexpr ALWAYS_INLINE T LeastSignificantZeroBit(T x) {
return ~x & (x + 1);
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE T ResetTrailingOnes(T x) {
return x & (x + 1);
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE T SetTrailingZeros(T x) {
return x | (x - 1);
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE T LeastSignificantOneBit(T x) {
return x & ~(x - 1);
}
template<std::integral T>
constexpr ALWAYS_INLINE T LeastSignificantZeroBit(T x) {
return ~x & (x + 1);
}
template<std::integral T>
constexpr ALWAYS_INLINE T MaskTrailingZeros(T x) {
return (~x) & (x - 1);
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE T MaskTrailingOnes(T x) {
return ~((~x) | (x + 1));
return x & ~(x + 1);
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE T MaskTrailingZerosAndLeastSignificantOneBit(T x) {
return x ^ (x - 1);
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE T MaskTrailingOnesAndLeastSignificantZeroBit(T x) {
return x ^ (x + 1);
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE int PopCount(T x) {
using U = typename std::make_unsigned<T>::type;
U u = static_cast<U>(x);
@ -164,7 +147,7 @@ namespace ams::util {
}
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE int CountLeadingZeros(T x) {
if (std::is_constant_evaluated()) {
for (size_t i = 0; i < impl::Log2<BITSIZEOF(T)>; ++i) {
@ -174,9 +157,8 @@ namespace ams::util {
return PopCount(static_cast<T>(~x));
} else {
using U = typename std::make_unsigned<T>::type;
const U u = static_cast<U>(x);
if (u != 0) {
if (const U u = static_cast<U>(x); u != 0) {
if constexpr (std::is_same<U, unsigned long long>::value) {
return __builtin_clzll(u);
} else if constexpr (std::is_same<U, unsigned long>::value) {
@ -198,7 +180,7 @@ namespace ams::util {
static_assert(CountLeadingZeros(static_cast<u64>(1) << 5) == BITSIZEOF(u64) - 1 - 5);
static_assert(CountLeadingZeros(static_cast<u64>(0)) == BITSIZEOF(u64));
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE int CountTrailingZeros(T x) {
if (std::is_constant_evaluated()) {
auto count = 0;
@ -209,8 +191,7 @@ namespace ams::util {
return count;
} else {
using U = typename std::make_unsigned<T>::type;
const U u = static_cast<U>(x);
if (u != 0) {
if (const U u = static_cast<U>(x); u != 0) {
if constexpr (std::is_same<U, unsigned long long>::value) {
return __builtin_ctzll(u);
} else if constexpr (std::is_same<U, unsigned long>::value) {
@ -231,31 +212,39 @@ namespace ams::util {
static_assert(CountTrailingZeros(static_cast<u64>(1) << 5) == 5);
static_assert(CountTrailingZeros(static_cast<u64>(0)) == BITSIZEOF(u64));
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE bool IsPowerOfTwo(T x) {
return x > 0 && ResetLeastSignificantOneBit(x) == 0;
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE T CeilingPowerOfTwo(T x) {
AMS_ASSERT(x > 0);
return T(1) << (BITSIZEOF(T) - CountLeadingZeros(T(x - 1)));
}
template<typename T> requires std::integral<T>
template<std::integral T>
constexpr ALWAYS_INLINE T FloorPowerOfTwo(T x) {
AMS_ASSERT(x > 0);
return T(1) << (BITSIZEOF(T) - CountLeadingZeros(x) - 1);
}
template<typename T, typename U>
template<std::integral T, std::integral U>
constexpr ALWAYS_INLINE T DivideUp(T v, U d) {
using Unsigned = typename std::make_unsigned<U>::type;
using Sum = decltype(T{0} + U{0});
#if defined(ATMOSPHERE_IS_STRATOSPHERE)
AMS_ASSERT(v >= 0);
AMS_ASSERT(d > 0);
AMS_ASSERT(static_cast<Sum>(v) <= (std::numeric_limits<Sum>::max() - static_cast<Sum>(d) + static_cast<Sum>(1)));
#endif
const Unsigned add = static_cast<Unsigned>(d) - 1;
return static_cast<T>((v + add) / d);
return static_cast<T>((static_cast<Sum>(v) + static_cast<Sum>(add)) / static_cast<Sum>(d));
}
template<typename T, T N, T D>
template<std::integral T, T N, T D>
constexpr ALWAYS_INLINE T ScaleByConstantFactorUp(const T V) {
/* Multiplying and dividing by large numerator/denominator can cause error to be introduced. */
/* This algorithm multiples/divides in stages, so as to mitigate this (particularly with large denominator). */