cosmopolitan/third_party/libcxx/atomic_support.hh

//===----------------------------------------------------------------------===////
//
// 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 "third_party/libcxx/__config"
#include "third_party/libcxx/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(__clang__) && defined(_GNUC_VER) && _GNUC_VER >= 407
#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_INLINE_VISIBILITY 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_INLINE_VISIBILITY void __libcpp_relaxed_store(_ValueType* __dest,
                                                             _FromType __val) {
  __atomic_store_n(__dest, __val, _AO_Relaxed);
}

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

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

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

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

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

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

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

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

template <class _ValueType>
inline _LIBCPP_INLINE_VISIBILITY 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