85 lines
2.7 KiB
C++
85 lines
2.7 KiB
C++
/*
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* Copyright (C) 2022 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ART_RUNTIME_BASE_ATOMIC_PAIR_H_
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#define ART_RUNTIME_BASE_ATOMIC_PAIR_H_
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#include "base/macros.h"
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#include <type_traits>
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namespace art {
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// std::pair<> is not trivially copyable and as such it is unsuitable for atomic operations.
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template <typename IntType>
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struct PACKED(2 * sizeof(IntType)) AtomicPair {
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static_assert(std::is_integral_v<IntType>);
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constexpr AtomicPair() : first(0), second(0) { }
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AtomicPair(IntType f, IntType s) : first(f), second(s) { }
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AtomicPair(const AtomicPair&) = default;
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AtomicPair& operator=(const AtomicPair&) = default;
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IntType first;
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IntType second;
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};
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template <typename IntType>
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ALWAYS_INLINE static inline AtomicPair<IntType> AtomicPairLoadAcquire(
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std::atomic<AtomicPair<IntType>>* target) {
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static_assert(std::atomic<AtomicPair<IntType>>::is_always_lock_free);
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return target->load(std::memory_order_acquire);
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}
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template <typename IntType>
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ALWAYS_INLINE static inline void AtomicPairStoreRelease(
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std::atomic<AtomicPair<IntType>>* target, AtomicPair<IntType> value) {
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static_assert(std::atomic<AtomicPair<IntType>>::is_always_lock_free);
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target->store(value, std::memory_order_release);
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}
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// llvm does not implement 16-byte atomic operations on x86-64.
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#if defined(__x86_64__)
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ALWAYS_INLINE static inline AtomicPair<uint64_t> AtomicPairLoadAcquire(
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std::atomic<AtomicPair<uint64_t>>* target) {
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uint64_t first, second;
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__asm__ __volatile__(
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"lock cmpxchg16b (%2)"
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: "=&a"(first), "=&d"(second)
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: "r"(target), "a"(0), "d"(0), "b"(0), "c"(0)
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: "cc");
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return {first, second};
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}
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ALWAYS_INLINE static inline void AtomicPairStoreRelease(
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std::atomic<AtomicPair<uint64_t>>* target, AtomicPair<uint64_t> value) {
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uint64_t first, second;
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__asm__ __volatile__ (
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"movq (%2), %%rax\n\t"
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"movq 8(%2), %%rdx\n\t"
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"1:\n\t"
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"lock cmpxchg16b (%2)\n\t"
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"jnz 1b"
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: "=&a"(first), "=&d"(second)
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: "r"(target), "b"(value.first), "c"(value.second)
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: "cc");
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}
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#endif // defined(__x86_64__)
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} // namespace art
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#endif // ART_RUNTIME_BASE_ATOMIC_PAIR_H_
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