src/include/atomic_support.h

//===----------------------------------------------------------------------===////
//
// 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
//
//===----------------------------------------------------------------------===////

#ifndef ATOMIC_SUPPORT_H
#define ATOMIC_SUPPORT_H

#include <__config>
#include <memory> // for __libcpp_relaxed_load

#if defined(__clang__) && __has_builtin(__atomic_load_n) && __has_builtin(__atomic_store_n) &&                         \
    __has_builtin(__atomic_add_fetch) && __has_builtin(__atomic_exchange_n) &&                                         \
    __has_builtin(__atomic_compare_exchange_n) && defined(__ATOMIC_RELAXED) && defined(__ATOMIC_CONSUME) &&            \
    defined(__ATOMIC_ACQUIRE) && defined(__ATOMIC_RELEASE) && defined(__ATOMIC_ACQ_REL) && defined(__ATOMIC_SEQ_CST)
#  define _LIBCPP_HAS_ATOMIC_BUILTINS
#elif defined(_LIBCPP_COMPILER_GCC)
#  define _LIBCPP_HAS_ATOMIC_BUILTINS
#endif

#if !defined(_LIBCPP_HAS_ATOMIC_BUILTINS) && !defined(_LIBCPP_HAS_NO_THREADS)
#  if defined(_LIBCPP_WARNING)
_LIBCPP_WARNING("Building libc++ without __atomic builtins is unsupported")
#  else
#    warning Building libc++ without __atomic builtins is unsupported
#  endif
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

namespace {

#if defined(_LIBCPP_HAS_ATOMIC_BUILTINS) && !defined(_LIBCPP_HAS_NO_THREADS)

enum __libcpp_atomic_order {
  _AO_Relaxed = __ATOMIC_RELAXED,
  _AO_Consume = __ATOMIC_CONSUME,
  _AO_Acquire = __ATOMIC_ACQUIRE,
  _AO_Release = __ATOMIC_RELEASE,
  _AO_Acq_Rel = __ATOMIC_ACQ_REL,
  _AO_Seq     = __ATOMIC_SEQ_CST
};

template <class _ValueType, class _FromType>
inline _LIBCPP_HIDE_FROM_ABI void __libcpp_atomic_store(_ValueType* __dest, _FromType __val, int __order = _AO_Seq) {
  __atomic_store_n(__dest, __val, __order);
}

template <class _ValueType, class _FromType>
inline _LIBCPP_HIDE_FROM_ABI void __libcpp_relaxed_store(_ValueType* __dest, _FromType __val) {
  __atomic_store_n(__dest, __val, _AO_Relaxed);
}

template <class _ValueType>
inline _LIBCPP_HIDE_FROM_ABI _ValueType __libcpp_atomic_load(_ValueType const* __val, int __order = _AO_Seq) {
  return __atomic_load_n(__val, __order);
}

template <class _ValueType, class _AddType>
inline _LIBCPP_HIDE_FROM_ABI _ValueType __libcpp_atomic_add(_ValueType* __val, _AddType __a, int __order = _AO_Seq) {
  return __atomic_add_fetch(__val, __a, __order);
}

template <class _ValueType>
inline _LIBCPP_HIDE_FROM_ABI _ValueType
__libcpp_atomic_exchange(_ValueType* __target, _ValueType __value, int __order = _AO_Seq) {
  return __atomic_exchange_n(__target, __value, __order);
}

template <class _ValueType>
inline _LIBCPP_HIDE_FROM_ABI bool __libcpp_atomic_compare_exchange(
    _ValueType* __val,
    _ValueType* __expected,
    _ValueType __after,
    int __success_order = _AO_Seq,
    int __fail_order    = _AO_Seq) {
  return __atomic_compare_exchange_n(__val, __expected, __after, true, __success_order, __fail_order);
}

#else // _LIBCPP_HAS_NO_THREADS

enum __libcpp_atomic_order { _AO_Relaxed, _AO_Consume, _AO_Acquire, _AO_Release, _AO_Acq_Rel, _AO_Seq };

template <class _ValueType, class _FromType>
inline _LIBCPP_HIDE_FROM_ABI void __libcpp_atomic_store(_ValueType* __dest, _FromType __val, int = 0) {
  *__dest = __val;
}

template <class _ValueType, class _FromType>
inline _LIBCPP_HIDE_FROM_ABI void __libcpp_relaxed_store(_ValueType* __dest, _FromType __val) {
  *__dest = __val;
}

template <class _ValueType>
inline _LIBCPP_HIDE_FROM_ABI _ValueType __libcpp_atomic_load(_ValueType const* __val, int = 0) {
  return *__val;
}

template <class _ValueType, class _AddType>
inline _LIBCPP_HIDE_FROM_ABI _ValueType __libcpp_atomic_add(_ValueType* __val, _AddType __a, int = 0) {
  return *__val += __a;
}

template <class _ValueType>
inline _LIBCPP_HIDE_FROM_ABI _ValueType
__libcpp_atomic_exchange(_ValueType* __target, _ValueType __value, int = _AO_Seq) {
  _ValueType old = *__target;
  *__target      = __value;
  return old;
}

template <class _ValueType>
inline _LIBCPP_HIDE_FROM_ABI bool
__libcpp_atomic_compare_exchange(_ValueType* __val, _ValueType* __expected, _ValueType __after, int = 0, int = 0) {
  if (*__val == *__expected) {
    *__val = __after;
    return true;
  }
  *__expected = *__val;
  return false;
}

#endif // _LIBCPP_HAS_NO_THREADS

} // end namespace

_LIBCPP_END_NAMESPACE_STD

#endif // ATOMIC_SUPPORT_H