[libc++][atomic_ref] Implement C++20 atomic_ref

Author: dalg24

libcxx/include/CMakeLists.txt

@@ -236,6 +236,7 @@ set(files
   __atomic/atomic_flag.h
   __atomic/atomic_init.h
   __atomic/atomic_lock_free.h
+  __atomic/atomic_ref.h
   __atomic/atomic_sync.h
   __atomic/check_memory_order.h
   __atomic/contention_t.h

libcxx/include/__atomic/atomic_ref.h

@@ -0,0 +1,238 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//                        Kokkos v. 4.0
+//       Copyright (2022) National Technology & Engineering
+//               Solutions of Sandia, LLC (NTESS).
+//
+// Under the terms of Contract DE-NA0003525 with NTESS,
+// the U.S. Government retains certain rights in this software.
+//
+//===---------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ATOMIC_ATOMIC_REF_H
+#define _LIBCPP___ATOMIC_ATOMIC_REF_H
+
+#include <__assert>
+#include <__atomic/check_memory_order.h>
+#include <__atomic/cxx_atomic_impl.h>
+#include <__atomic/is_always_lock_free.h>
+#include <__config>
+#include <__memory/addressof.h>
+#include <__type_traits/is_floating_point.h>
+#include <__type_traits/is_function.h>
+#include <__type_traits/is_nothrow_constructible.h>
+#include <__type_traits/is_same.h>
+#include <cinttypes>
+#include <concepts>
+#include <cstddef>
+#include <limits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+template <class _Tp, bool = is_integral_v<_Tp> && !is_same_v<_Tp, bool>, bool = is_floating_point_v<_Tp>>
+struct __atomic_ref_base {
+  mutable __cxx_atomic_impl<_Tp&> __a_;
+
+  using value_type = _Tp;
+
+  static constexpr size_t required_alignment = alignof(_Tp);
+
+  static constexpr bool is_always_lock_free = __libcpp_is_always_lock_free<_Tp>::__value;
+
+  _LIBCPP_HIDE_FROM_ABI bool is_lock_free() const noexcept { return __cxx_atomic_is_lock_free(sizeof(_Tp)); }
+
+  _LIBCPP_HIDE_FROM_ABI void store(_Tp __desired, memory_order __order = memory_order::seq_cst) const noexcept
+      _LIBCPP_CHECK_STORE_MEMORY_ORDER(__order) {
+    _LIBCPP_ASSERT_UNCATEGORIZED(
+        __order == memory_order::relaxed || __order == memory_order::release || __order == memory_order::seq_cst,
+        "memory order argument to atomic store operation is invalid");
+    __cxx_atomic_store(&__a_, __desired, __order);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI _Tp operator=(_Tp __desired) const noexcept {
+    store(__desired);
+    return __desired;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI _Tp load(memory_order __order = memory_order::seq_cst) const noexcept
+      _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__order) {
+    _LIBCPP_ASSERT_UNCATEGORIZED(
+        __order == memory_order::relaxed || __order == memory_order::consume || __order == memory_order::acquire ||
+            __order == memory_order::seq_cst,
+        "memory order argument to atomic load operation is invalid");
+    return __cxx_atomic_load(&__a_, __order);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI operator _Tp() const noexcept { return load(); }
+
+  _LIBCPP_HIDE_FROM_ABI _Tp exchange(_Tp __desired, memory_order __order = memory_order::seq_cst) const noexcept {
+    return __cxx_atomic_exchange(&__a_, __desired, __order);
+  }
+  _LIBCPP_HIDE_FROM_ABI bool
+  compare_exchange_weak(_Tp& __expected, _Tp __desired, memory_order __success, memory_order __failure) const noexcept
+      _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__success, __failure) {
+    _LIBCPP_ASSERT_UNCATEGORIZED(
+        __failure == memory_order::relaxed || __failure == memory_order::consume ||
+            __failure == memory_order::acquire || __failure == memory_order::seq_cst,
+        "failure memory order argument to weak atomic compare-and-exchange operation is invalid");
+    return __cxx_atomic_compare_exchange_weak(&__a_, &__expected, __desired, __success, __failure);
+  }
+  _LIBCPP_HIDE_FROM_ABI bool
+  compare_exchange_strong(_Tp& __expected, _Tp __desired, memory_order __success, memory_order __failure) const noexcept
+      _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__success, __failure) {
+    _LIBCPP_ASSERT_UNCATEGORIZED(
+        __failure == memory_order::relaxed || __failure == memory_order::consume ||
+            __failure == memory_order::acquire || __failure == memory_order::seq_cst,
+        "failure memory order argument to strong atomic compare-and-exchange operation is invalid");
+    return __cxx_atomic_compare_exchange_strong(&__a_, &__expected, __desired, __success, __failure);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI bool
+  compare_exchange_weak(_Tp& __expected, _Tp __desired, memory_order __order = memory_order::seq_cst) const noexcept {
+    return __cxx_atomic_compare_exchange_weak(&__a_, &__expected, __desired, __order, __order);
+  }
+  _LIBCPP_HIDE_FROM_ABI bool
+  compare_exchange_strong(_Tp& __expected, _Tp __desired, memory_order __order = memory_order::seq_cst) const noexcept {
+    return __cxx_atomic_compare_exchange_strong(&__a_, &__expected, __desired, __order, __order);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI void wait(_Tp __old, memory_order __order = memory_order::seq_cst) const noexcept
+      _LIBCPP_CHECK_WAIT_MEMORY_ORDER(__order) {
+    _LIBCPP_ASSERT_UNCATEGORIZED(
+        __order == memory_order::relaxed || __order == memory_order::consume || __order == memory_order::acquire ||
+            __order == memory_order::seq_cst,
+        "memory order argument to atomic wait operation is invalid");
+    __cxx_atomic_wait(addressof(__a_), __old, __order);
+  }
+  _LIBCPP_HIDE_FROM_ABI void notify_one() const noexcept { __cxx_atomic_notify_one(addressof(__a_)); }
+  _LIBCPP_HIDE_FROM_ABI void notify_all() const noexcept { __cxx_atomic_notify_all(addressof(__a_)); }
+
+  _LIBCPP_HIDE_FROM_ABI __atomic_ref_base(_Tp& __obj) : __a_(__obj) {}
+};
+
+template <class _Tp>
+struct __atomic_ref_base<_Tp, /*_IsIntegral=*/true, /*_IsFloatingPoint=*/false>
+    : public __atomic_ref_base<_Tp, false, false> {
+  using __base = __atomic_ref_base<_Tp, false, false>;
+
+  using difference_type = __base::value_type;
+
+  _LIBCPP_HIDE_FROM_ABI __atomic_ref_base(_Tp& __obj) : __base(__obj) {}
+
+  _LIBCPP_HIDE_FROM_ABI _Tp operator=(_Tp __desired) const noexcept { return __base::operator=(__desired); }
+
+  _LIBCPP_HIDE_FROM_ABI _Tp fetch_add(_Tp __arg, memory_order __order = memory_order_seq_cst) const noexcept {
+    return __cxx_atomic_fetch_add(&this->__a_, __arg, __order);
+  }
+  _LIBCPP_HIDE_FROM_ABI _Tp fetch_sub(_Tp __arg, memory_order __order = memory_order_seq_cst) const noexcept {
+    return __cxx_atomic_fetch_sub(&this->__a_, __arg, __order);
+  }
+  _LIBCPP_HIDE_FROM_ABI _Tp fetch_and(_Tp __arg, memory_order __order = memory_order_seq_cst) const noexcept {
+    return __cxx_atomic_fetch_and(&this->__a_, __arg, __order);
+  }
+  _LIBCPP_HIDE_FROM_ABI _Tp fetch_or(_Tp __arg, memory_order __order = memory_order_seq_cst) const noexcept {
+    return __cxx_atomic_fetch_or(&this->__a_, __arg, __order);
+  }
+  _LIBCPP_HIDE_FROM_ABI _Tp fetch_xor(_Tp __arg, memory_order __order = memory_order_seq_cst) const noexcept {
+    return __cxx_atomic_fetch_xor(&this->__a_, __arg, __order);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI _Tp operator++(int) const noexcept { return fetch_add(_Tp(1)); }
+  _LIBCPP_HIDE_FROM_ABI _Tp operator--(int) const noexcept { return fetch_sub(_Tp(1)); }
+  _LIBCPP_HIDE_FROM_ABI _Tp operator++() const noexcept { return fetch_add(_Tp(1)) + _Tp(1); }
+  _LIBCPP_HIDE_FROM_ABI _Tp operator--() const noexcept { return fetch_sub(_Tp(1)) - _Tp(1); }
+  _LIBCPP_HIDE_FROM_ABI _Tp operator+=(_Tp __arg) const noexcept { return fetch_add(__arg) + __arg; }
+  _LIBCPP_HIDE_FROM_ABI _Tp operator-=(_Tp __arg) const noexcept { return fetch_sub(__arg) - __arg; }
+  _LIBCPP_HIDE_FROM_ABI _Tp operator&=(_Tp __arg) const noexcept { return fetch_and(__arg) & __arg; }
+  _LIBCPP_HIDE_FROM_ABI _Tp operator|=(_Tp __arg) const noexcept { return fetch_or(__arg) | __arg; }
+  _LIBCPP_HIDE_FROM_ABI _Tp operator^=(_Tp __arg) const noexcept { return fetch_xor(__arg) ^ __arg; }
+};
+
+template <class _Tp>
+struct __atomic_ref_base<_Tp, /*_IsIntegral=*/false, /*_IsFloatingPoint=*/true>
+    : public __atomic_ref_base<_Tp, false, false> {
+  using __base = __atomic_ref_base<_Tp, false, false>;
+
+  using difference_type = __base::value_type;
+
+  _LIBCPP_HIDE_FROM_ABI __atomic_ref_base(_Tp& __obj) : __base(__obj) {}
+
+  _LIBCPP_HIDE_FROM_ABI _Tp operator=(_Tp __desired) const noexcept { return __base::operator=(__desired); }
+
+  _LIBCPP_HIDE_FROM_ABI _Tp fetch_add(_Tp __arg, memory_order __order = memory_order_seq_cst) const noexcept {
+    return __cxx_atomic_fetch_add(&this->__a_, __arg, __order);
+  }
+  _LIBCPP_HIDE_FROM_ABI _Tp fetch_sub(_Tp __arg, memory_order __order = memory_order_seq_cst) const noexcept {
+    return __cxx_atomic_fetch_sub(&this->__a_, __arg, __order);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI _Tp operator+=(_Tp __arg) const noexcept { return fetch_add(__arg) + __arg; }
+  _LIBCPP_HIDE_FROM_ABI _Tp operator-=(_Tp __arg) const noexcept { return fetch_sub(__arg) - __arg; }
+};
+
+template <class _Tp>
+struct atomic_ref : public __atomic_ref_base<_Tp> {
+  static_assert(is_trivially_copyable<_Tp>::value, "std::atomic_ref<T> requires that 'T' be a trivially copyable type");
+
+  using __base = __atomic_ref_base<_Tp>;
+
+  _LIBCPP_HIDE_FROM_ABI explicit atomic_ref(_Tp& __obj) : __base(__obj) {
+    _LIBCPP_ASSERT_UNCATEGORIZED((uintptr_t)addressof(__obj) % __base::required_alignment == 0,
+                                 "atomic_ref ctor: referenced object must be aligned to required_alignment");
+  }
+
+  _LIBCPP_HIDE_FROM_ABI atomic_ref(const atomic_ref&) noexcept = default;
+
+  _LIBCPP_HIDE_FROM_ABI _Tp operator=(_Tp __desired) const noexcept { return __base::operator=(__desired); }
+
+  atomic_ref& operator=(const atomic_ref&) = delete;
+};
+
+template <class _Tp>
+struct atomic_ref<_Tp*> : public __atomic_ref_base<_Tp*> {
+  using __base = __atomic_ref_base<_Tp*>;
+
+  using difference_type = ptrdiff_t;
+
+  _LIBCPP_HIDE_FROM_ABI _Tp* fetch_add(ptrdiff_t __arg, memory_order __order = memory_order_seq_cst) const noexcept {
+    return __cxx_atomic_fetch_add(&this->__a_, __arg, __order);
+  }
+  _LIBCPP_HIDE_FROM_ABI _Tp* fetch_sub(ptrdiff_t __arg, memory_order __order = memory_order_seq_cst) const noexcept {
+    return __cxx_atomic_fetch_sub(&this->__a_, __arg, __order);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI _Tp* operator++(int) const noexcept { return fetch_add(1); }
+  _LIBCPP_HIDE_FROM_ABI _Tp* operator--(int) const noexcept { return fetch_sub(1); }
+  _LIBCPP_HIDE_FROM_ABI _Tp* operator++() const noexcept { return fetch_add(1) + 1; }
+  _LIBCPP_HIDE_FROM_ABI _Tp* operator--() const noexcept { return fetch_sub(1) - 1; }
+  _LIBCPP_HIDE_FROM_ABI _Tp* operator+=(ptrdiff_t __arg) const noexcept { return fetch_add(__arg) + __arg; }
+  _LIBCPP_HIDE_FROM_ABI _Tp* operator-=(ptrdiff_t __arg) const noexcept { return fetch_sub(__arg) - __arg; }
+
+  _LIBCPP_HIDE_FROM_ABI explicit atomic_ref(_Tp*& __ptr) : __base(__ptr) {}
+
+  _LIBCPP_HIDE_FROM_ABI _Tp* operator=(_Tp* __desired) const noexcept { return __base::operator=(__desired); }
+
+  atomic_ref& operator=(const atomic_ref&) = delete;
+};
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP__ATOMIC_ATOMIC_REF_H

libcxx/include/atomic

@@ -594,6 +594,7 @@ template <class T>
 #include <__atomic/atomic_flag.h>
 #include <__atomic/atomic_init.h>
 #include <__atomic/atomic_lock_free.h>
+#include <__atomic/atomic_ref.h>
 #include <__atomic/atomic_sync.h>
 #include <__atomic/check_memory_order.h>
 #include <__atomic/contention_t.h>