3a63407686
The __atomic_base base class is only useful to conditionalize the operations we provide inside std::atomic. It shouldn't be used directly from other places in the library which can use std::atomic directly instead. Since we've granularized our includes, using std::atomic directly should not make much of a difference compile-time wise. This patch starts using std::atomic directly from other classes like std::barrier and std::latch. Changing this shouldn't be an ABI break since both classes have the same size and layout. The benefits of this patch are isolating other parts of the code base from implementation details of std::atomic and simplifying the mental model for std::atomic's layers of implementation by making it clear that __atomic_base is only an implementation detail of std::atomic.
131 lines
3.6 KiB
C++
131 lines
3.6 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP_LATCH
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#define _LIBCPP_LATCH
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/*
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latch synopsis
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namespace std
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{
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class latch // since C++20
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{
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public:
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static constexpr ptrdiff_t max() noexcept;
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constexpr explicit latch(ptrdiff_t __expected);
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~latch();
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latch(const latch&) = delete;
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latch& operator=(const latch&) = delete;
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void count_down(ptrdiff_t __update = 1);
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bool try_wait() const noexcept;
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void wait() const;
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void arrive_and_wait(ptrdiff_t __update = 1);
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private:
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ptrdiff_t __counter; // exposition only
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};
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}
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*/
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#include <__config>
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#if _LIBCPP_HAS_THREADS
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# include <__assert>
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# include <__atomic/atomic.h>
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# include <__atomic/atomic_sync.h>
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# include <__atomic/memory_order.h>
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# include <__cstddef/ptrdiff_t.h>
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# include <limits>
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# include <version>
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# if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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# endif
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_LIBCPP_PUSH_MACROS
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# include <__undef_macros>
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# if _LIBCPP_STD_VER >= 20
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_LIBCPP_BEGIN_NAMESPACE_STD
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class latch {
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atomic<ptrdiff_t> __a_;
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public:
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static _LIBCPP_HIDE_FROM_ABI constexpr ptrdiff_t max() noexcept { return numeric_limits<ptrdiff_t>::max(); }
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inline _LIBCPP_HIDE_FROM_ABI constexpr explicit latch(ptrdiff_t __expected) : __a_(__expected) {
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_LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
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__expected >= 0,
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"latch::latch(ptrdiff_t): latch cannot be "
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"initialized with a negative value");
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_LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
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__expected <= max(),
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"latch::latch(ptrdiff_t): latch cannot be "
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"initialized with a value greater than max()");
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}
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_LIBCPP_HIDE_FROM_ABI ~latch() = default;
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latch(const latch&) = delete;
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latch& operator=(const latch&) = delete;
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inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void count_down(ptrdiff_t __update = 1) {
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_LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(__update >= 0, "latch::count_down called with a negative value");
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auto const __old = __a_.fetch_sub(__update, memory_order_release);
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_LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
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__update <= __old,
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"latch::count_down called with a value greater "
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"than the internal counter");
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if (__old == __update)
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__a_.notify_all();
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}
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inline _LIBCPP_HIDE_FROM_ABI bool try_wait() const noexcept {
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auto __value = __a_.load(memory_order_acquire);
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return try_wait_impl(__value);
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}
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inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void wait() const {
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std::__atomic_wait_unless(
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__a_, [this](ptrdiff_t& __value) -> bool { return try_wait_impl(__value); }, memory_order_acquire);
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}
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inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void arrive_and_wait(ptrdiff_t __update = 1) {
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_LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(__update >= 0, "latch::arrive_and_wait called with a negative value");
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// other preconditions on __update are checked in count_down()
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count_down(__update);
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wait();
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}
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private:
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_LIBCPP_HIDE_FROM_ABI bool try_wait_impl(ptrdiff_t& __value) const noexcept { return __value == 0; }
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};
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_LIBCPP_END_NAMESPACE_STD
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# endif // _LIBCPP_STD_VER >= 20
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP_HAS_THREADS
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#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
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# include <atomic>
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# include <cstddef>
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#endif
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#endif // _LIBCPP_LATCH
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