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// Copyright 2020 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef SRC_DAWN_COMMON_ITYP_BITSET_H_
#define SRC_DAWN_COMMON_ITYP_BITSET_H_
#include "dawn/common/BitSetIterator.h"
#include "dawn/common/Platform.h"
#include "dawn/common/TypedInteger.h"
#include "dawn/common/UnderlyingType.h"
namespace dawn {
namespace ityp {
// ityp::bitset is a helper class that wraps std::bitset with the restriction that
// indices must be a particular type |Index|.
template <typename Index, size_t N>
class bitset : private ::std::bitset<N> {
using I = UnderlyingType<Index>;
using Base = ::std::bitset<N>;
static_assert(sizeof(I) <= sizeof(size_t));
explicit constexpr bitset(const Base& rhs) : Base(rhs) {}
public:
using reference = typename Base::reference;
constexpr bitset() noexcept : Base() {}
// NOLINTNEXTLINE(runtime/explicit)
constexpr bitset(uint64_t value) noexcept : Base(value) {}
constexpr bool operator[](Index i) const { return Base::operator[](static_cast<I>(i)); }
typename Base::reference operator[](Index i) { return Base::operator[](static_cast<I>(i)); }
bool test(Index i) const { return Base::test(static_cast<I>(i)); }
using Base::all;
using Base::any;
using Base::count;
using Base::none;
using Base::size;
bool operator==(const bitset& other) const noexcept {
return Base::operator==(static_cast<const Base&>(other));
}
bool operator!=(const bitset& other) const noexcept {
return !Base::operator==(static_cast<const Base&>(other));
}
bitset& operator&=(const bitset& other) noexcept {
return static_cast<bitset&>(Base::operator&=(static_cast<const Base&>(other)));
}
bitset& operator|=(const bitset& other) noexcept {
return static_cast<bitset&>(Base::operator|=(static_cast<const Base&>(other)));
}
bitset& operator^=(const bitset& other) noexcept {
return static_cast<bitset&>(Base::operator^=(static_cast<const Base&>(other)));
}
bitset operator~() const noexcept { return bitset(*this).flip(); }
bitset& set() noexcept { return static_cast<bitset&>(Base::set()); }
bitset& set(Index i, bool value = true) {
return static_cast<bitset&>(Base::set(static_cast<I>(i), value));
}
bitset& reset() noexcept { return static_cast<bitset&>(Base::reset()); }
bitset& reset(Index i) { return static_cast<bitset&>(Base::reset(static_cast<I>(i))); }
bitset& flip() noexcept { return static_cast<bitset&>(Base::flip()); }
bitset& flip(Index i) { return static_cast<bitset&>(Base::flip(static_cast<I>(i))); }
using Base::to_string;
using Base::to_ullong;
using Base::to_ulong;
friend bitset operator&(const bitset& lhs, const bitset& rhs) noexcept {
return bitset(static_cast<const Base&>(lhs) & static_cast<const Base&>(rhs));
}
friend bitset operator|(const bitset& lhs, const bitset& rhs) noexcept {
return bitset(static_cast<const Base&>(lhs) | static_cast<const Base&>(rhs));
}
friend bitset operator^(const bitset& lhs, const bitset& rhs) noexcept {
return bitset(static_cast<const Base&>(lhs) ^ static_cast<const Base&>(rhs));
}
friend BitSetIterator<N, Index> IterateBitSet(const bitset& bitset) {
return BitSetIterator<N, Index>(static_cast<const Base&>(bitset));
}
friend struct std::hash<bitset>;
};
} // namespace ityp
// Assume we have bitset of at most 64 bits
// Returns i which is the next integer of the index of the highest bit
// i == 0 if there is no bit set to true
// i == 1 if only the least significant bit (at index 0) is the bit set to true with the
// highest index
// ...
// i == 64 if the most significant bit (at index 64) is the bit set to true with the highest
// index
template <typename Index, size_t N>
Index GetHighestBitIndexPlusOne(const ityp::bitset<Index, N>& bitset) {
using I = UnderlyingType<Index>;
#if DAWN_COMPILER_IS(MSVC)
if constexpr (N > 32) {
#if DAWN_PLATFORM_IS(64_BIT)
// NOLINTNEXTLINE(runtime/int)
unsigned long firstBitIndex = 0ul;
unsigned char ret = _BitScanReverse64(&firstBitIndex, bitset.to_ullong());
if (ret == 0) {
return Index(static_cast<I>(0));
}
return Index(static_cast<I>(firstBitIndex + 1));
#else // DAWN_PLATFORM_IS(64_BIT)
if (bitset.none()) {
return Index(static_cast<I>(0));
}
for (size_t i = 0u; i < N; i++) {
if (bitset.test(Index(static_cast<I>(N - 1 - i)))) {
return Index(static_cast<I>(N - i));
}
}
UNREACHABLE();
#endif // DAWN_PLATFORM_IS(64_BIT)
} else {
// NOLINTNEXTLINE(runtime/int)
unsigned long firstBitIndex = 0ul;
unsigned char ret = _BitScanReverse(&firstBitIndex, bitset.to_ulong());
if (ret == 0) {
return Index(static_cast<I>(0));
}
return Index(static_cast<I>(firstBitIndex + 1));
}
#else // DAWN_COMPILER_IS(MSVC)
if (bitset.none()) {
return Index(static_cast<I>(0));
}
if constexpr (N > 32) {
return Index(
static_cast<I>(64 - static_cast<uint32_t>(__builtin_clzll(bitset.to_ullong()))));
} else {
return Index(static_cast<I>(32 - static_cast<uint32_t>(__builtin_clz(bitset.to_ulong()))));
}
#endif // DAWN_COMPILER_IS(MSVC)
}
} // namespace dawn
#endif // SRC_DAWN_COMMON_ITYP_BITSET_H_