[libcxx-commits] [libcxx] [libc++] refactor `cxx_atomic_wait` to make it reusable for atomic_ref (PR #81427)

[Louis Dionne via libcxx-commits]

================
@@ -62,61 +144,63 @@ struct __libcpp_atomic_wait_backoff_impl {
   }
 };
 
-template <class _Atp, class _Poll, class _BackoffTest>
-_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool
-__cxx_atomic_wait(_Atp* __a, _Poll&& __poll, _BackoffTest&& __backoff_test) {
-  __libcpp_atomic_wait_backoff_impl<_Atp, __decay_t<_BackoffTest> > __backoff_fn = {__a, __backoff_test};
-  return std::__libcpp_thread_poll_with_backoff(__poll, __backoff_fn);
+template <class _AtomicWaitable, class _Poll>
+_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
+__atomic_wait_unless(const _AtomicWaitable& __a, _Poll&& __poll, memory_order __order) {
+  static_assert(__atomic_waitable<_AtomicWaitable>::value, "");
+  __atomic_wait_poll_impl<_AtomicWaitable, __decay_t<_Poll> > __poll_impl     = {__a, __poll, __order};
+  __atomic_wait_backoff_impl<_AtomicWaitable, __decay_t<_Poll> > __backoff_fn = {__a, __poll, __order};
+  std::__libcpp_thread_poll_with_backoff(__poll_impl, __backoff_fn);
 }
 
-template <class _Poll>
-struct __libcpp_atomic_wait_poll_as_backoff_test {
-  _Poll __poll_;
-
-  _LIBCPP_AVAILABILITY_SYNC
-  _LIBCPP_HIDE_FROM_ABI bool operator()(__cxx_contention_t&) const { return __poll_(); }
-};
+template <class _AtomicWaitable>
+_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void __atomic_notify_one(const _AtomicWaitable& __a) {
+  static_assert(__atomic_waitable<_AtomicWaitable>::value, "");
+  __atomic_contention_address_cpo __atomic_contention_address = {};
+  std::__cxx_atomic_notify_one(__atomic_contention_address(__a));
+}
 
-template <class _Atp, class _Poll>
-_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool __cxx_atomic_wait(_Atp* __a, _Poll&& __poll) {
-  __libcpp_atomic_wait_backoff_impl<_Atp, __libcpp_atomic_wait_poll_as_backoff_test<_Poll&> > __backoff_fn = {
-      __a, {__poll}};
-  return std::__libcpp_thread_poll_with_backoff(__poll, __backoff_fn);
+template <class _AtomicWaitable>
+_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void __atomic_notify_all(const _AtomicWaitable& __a) {
+  static_assert(__atomic_waitable<_AtomicWaitable>::value, "");
+  __atomic_contention_address_cpo __atomic_contention_address = {};
+  std::__cxx_atomic_notify_all(__atomic_contention_address(__a));
 }
 
 #else // _LIBCPP_HAS_NO_THREADS
 
-template <class _Tp>
-_LIBCPP_HIDE_FROM_ABI void __cxx_atomic_notify_all(__cxx_atomic_impl<_Tp> const volatile*) {}
-template <class _Tp>
-_LIBCPP_HIDE_FROM_ABI void __cxx_atomic_notify_one(__cxx_atomic_impl<_Tp> const volatile*) {}
-template <class _Atp, class _Fn>
-_LIBCPP_HIDE_FROM_ABI bool __cxx_atomic_wait(_Atp*, _Fn&& __test_fn) {
-  return std::__libcpp_thread_poll_with_backoff(__test_fn, __spinning_backoff_policy());
+template <class _AtomicWaitable, class _Poll>
+_LIBCPP_HIDE_FROM_ABI void __atomic_wait_unless(const _AtomicWaitable& __a, _Poll&& __poll, memory_order __order) {
+  __atomic_wait_poll_impl<_AtomicWaitable, __decay_t<_Poll> > __poll_fn = {__a, __poll, __order};
+  std::__libcpp_thread_poll_with_backoff(__poll_fn, __spinning_backoff_policy());
 }
 
+template <class _AtomicWaitable>
+_LIBCPP_HIDE_FROM_ABI void __atomic_notify_one(const _AtomicWaitable&) {}
+
+template <class _AtomicWaitable>
+_LIBCPP_HIDE_FROM_ABI void __atomic_notify_all(const _AtomicWaitable&) {}
+
 #endif // _LIBCPP_HAS_NO_THREADS
 
 template <typename _Tp>
 _LIBCPP_HIDE_FROM_ABI bool __cxx_nonatomic_compare_equal(_Tp const& __lhs, _Tp const& __rhs) {
   return std::memcmp(std::addressof(__lhs), std::addressof(__rhs), sizeof(_Tp)) == 0;
 }
 
-template <class _Atp, class _Tp>
-struct __cxx_atomic_wait_test_fn_impl {
-  _Atp* __a;
-  _Tp __val;
-  memory_order __order;
-  _LIBCPP_HIDE_FROM_ABI bool operator()() const {
-    return !std::__cxx_nonatomic_compare_equal(std::__cxx_atomic_load(__a, __order), __val);
+template <class _Tp>
+struct __bind_nonatomic_equal {
+  _Tp __val_;
+  _LIBCPP_HIDE_FROM_ABI bool operator()(const _Tp& __arg) const {
+    return !std::__cxx_nonatomic_compare_equal(__arg, __val_);
   }
 };
 
-template <class _Atp, class _Tp>
-_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool
-__cxx_atomic_wait(_Atp* __a, _Tp const __val, memory_order __order) {
-  __cxx_atomic_wait_test_fn_impl<_Atp, _Tp> __test_fn = {__a, __val, __order};
-  return std::__cxx_atomic_wait(__a, __test_fn);
+template <class _AtomicWaitable, class _Up>
----------------
ldionne wrote:

`enable_if<__atomic_waitable<...>>`? Or at least `static_assert`?

https://github.com/llvm/llvm-project/pull/81427