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[libc++] Extract a clean base support API for std::atomic
This doesn't change the operations that std::atomic is based on, but it reorganizes the C11 / GCC implementation split to make it clearer what's the base support layer and what's not.
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5 files changed

+409
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‎libcxx/include/CMakeLists.txt

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@@ -212,11 +212,13 @@ set(files
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__atomic/atomic_sync.h
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__atomic/check_memory_order.h
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__atomic/contention_t.h
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__atomic/cxx_atomic_impl.h
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__atomic/fence.h
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__atomic/is_always_lock_free.h
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__atomic/kill_dependency.h
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__atomic/memory_order.h
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__atomic/support/c11.h
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__atomic/support/gcc.h
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__atomic/support.h
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__atomic/to_gcc_order.h
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__bit/bit_cast.h
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__bit/bit_ceil.h

‎libcxx/include/__atomic/support.h

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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___ATOMIC_SUPPORT_H
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#define _LIBCPP___ATOMIC_SUPPORT_H
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#include <__config>
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#include <__type_traits/is_trivially_copyable.h>
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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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//
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// This file implements base support for atomics on the platform.
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//
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// The following operations and types must be implemented (where _Atmc
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// is __cxx_atomic_base_impl for readability):
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//
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// clang-format off
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//
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// template <class _Tp>
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// struct __cxx_atomic_base_impl;
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//
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// #define __cxx_atomic_is_lock_free(__size)
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//
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// void __cxx_atomic_thread_fence(memory_order __order) noexcept;
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// void __cxx_atomic_signal_fence(memory_order __order) noexcept;
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//
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// template <class _Tp>
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// void __cxx_atomic_init(_Atmc<_Tp> volatile* __a, _Tp __val) noexcept;
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// template <class _Tp>
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// void __cxx_atomic_init(_Atmc<_Tp>* __a, _Tp __val) noexcept;
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//
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// template <class _Tp>
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// void __cxx_atomic_store(_Atmc<_Tp> volatile* __a, _Tp __val, memory_order __order) noexcept;
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// template <class _Tp>
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// void __cxx_atomic_store(_Atmc<_Tp>* __a, _Tp __val, memory_order __order) noexcept;
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//
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// template <class _Tp>
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// _Tp __cxx_atomic_load(_Atmc<_Tp> const volatile* __a, memory_order __order) noexcept;
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// template <class _Tp>
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// _Tp __cxx_atomic_load(_Atmc<_Tp> const* __a, memory_order __order) noexcept;
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//
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// template <class _Tp>
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// void __cxx_atomic_load_inplace(_Atmc<_Tp> const volatile* __a, _Tp* __dst, memory_order __order) noexcept;
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// template <class _Tp>
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// void __cxx_atomic_load_inplace(_Atmc<_Tp> const* __a, _Tp* __dst, memory_order __order) noexcept;
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//
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// template <class _Tp>
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// _Tp __cxx_atomic_exchange(_Atmc<_Tp> volatile* __a, _Tp __value, memory_order __order) noexcept;
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// template <class _Tp>
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// _Tp __cxx_atomic_exchange(_Atmc<_Tp>* __a, _Tp __value, memory_order __order) noexcept;
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//
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// template <class _Tp>
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// bool __cxx_atomic_compare_exchange_strong(_Atmc<_Tp> volatile* __a, _Tp* __expected, _Tp __value, memory_order __success, memory_order __failure) noexcept;
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// template <class _Tp>
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// bool __cxx_atomic_compare_exchange_strong(_Atmc<_Tp>* __a, _Tp* __expected, _Tp __value, memory_order __success, memory_order __failure) noexcept;
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//
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// template <class _Tp>
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// bool __cxx_atomic_compare_exchange_weak(_Atmc<_Tp> volatile* __a, _Tp* __expected, _Tp __value, memory_order __success, memory_order __failure) noexcept;
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// template <class _Tp>
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// bool __cxx_atomic_compare_exchange_weak(_Atmc<_Tp>* __a, _Tp* __expected, _Tp __value, memory_order __success, memory_order __failure) noexcept;
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//
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// template <class _Tp>
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// _Tp __cxx_atomic_fetch_add(_Atmc<_Tp> volatile* __a, _Tp __delta, memory_order __order) noexcept;
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// template <class _Tp>
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// _Tp __cxx_atomic_fetch_add(_Atmc<_Tp>* __a, _Tp __delta, memory_order __order) noexcept;
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//
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// template <class _Tp>
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// _Tp* __cxx_atomic_fetch_add(_Atmc<_Tp*> volatile* __a, ptrdiff_t __delta, memory_order __order) noexcept;
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// template <class _Tp>
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// _Tp* __cxx_atomic_fetch_add(_Atmc<_Tp*>* __a, ptrdiff_t __delta, memory_order __order) noexcept;
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//
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// template <class _Tp>
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// _Tp __cxx_atomic_fetch_sub(_Atmc<_Tp> volatile* __a, _Tp __delta, memory_order __order) noexcept;
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// template <class _Tp>
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// _Tp __cxx_atomic_fetch_sub(_Atmc<_Tp>* __a, _Tp __delta, memory_order __order) noexcept;
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// template <class _Tp>
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// _Tp* __cxx_atomic_fetch_sub(_Atmc<_Tp*> volatile* __a, ptrdiff_t __delta, memory_order __order) noexcept;
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// template <class _Tp>
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// _Tp* __cxx_atomic_fetch_sub(_Atmc<_Tp*>* __a, ptrdiff_t __delta, memory_order __order) noexcept;
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//
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// template <class _Tp>
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// _Tp __cxx_atomic_fetch_and(_Atmc<_Tp> volatile* __a, _Tp __pattern, memory_order __order) noexcept;
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// template <class _Tp>
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// _Tp __cxx_atomic_fetch_and(_Atmc<_Tp>* __a, _Tp __pattern, memory_order __order) noexcept;
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//
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// template <class _Tp>
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// _Tp __cxx_atomic_fetch_or(_Atmc<_Tp> volatile* __a, _Tp __pattern, memory_order __order) noexcept;
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// template <class _Tp>
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// _Tp __cxx_atomic_fetch_or(_Atmc<_Tp>* __a, _Tp __pattern, memory_order __order) noexcept;
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// template <class _Tp>
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// _Tp __cxx_atomic_fetch_xor(_Atmc<_Tp> volatile* __a, _Tp __pattern, memory_order __order) noexcept;
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// template <class _Tp>
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// _Tp __cxx_atomic_fetch_xor(_Atmc<_Tp>* __a, _Tp __pattern, memory_order __order) noexcept;
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//
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// clang-format on
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//
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#if _LIBCPP_HAS_GCC_ATOMIC_IMP
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# include <__atomic/support/gcc.h>
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#elif _LIBCPP_HAS_C_ATOMIC_IMP
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# include <__atomic/support/c11.h>
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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template <typename _Tp, typename _Base = __cxx_atomic_base_impl<_Tp> >
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struct __cxx_atomic_impl : public _Base {
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static_assert(is_trivially_copyable<_Tp>::value, "std::atomic<T> requires that 'T' be a trivially copyable type");
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_LIBCPP_HIDE_FROM_ABI __cxx_atomic_impl() _NOEXCEPT = default;
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR explicit __cxx_atomic_impl(_Tp __value) _NOEXCEPT : _Base(__value) {}
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};
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___ATOMIC_SUPPORT_H

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