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

via libcxx-commits libcxx-commits at lists.llvm.org
Mon Feb 12 09:50:27 PST 2024


https://github.com/huixie90 updated https://github.com/llvm/llvm-project/pull/81427

>From 6a4f73d6a144c7e3649c0efd3f4e0a68552fb1b8 Mon Sep 17 00:00:00 2001
From: Hui <hui.xie0621 at gmail.com>
Date: Sun, 11 Feb 2024 19:11:28 +0000
Subject: [PATCH 1/4] [libc++] refactor `cxx_atomic_wait` to make it reusable
 for atomic_ref

---
 libcxx/include/__atomic/atomic_base.h |  36 ++++--
 libcxx/include/__atomic/atomic_flag.h |  25 +++-
 libcxx/include/__atomic/atomic_sync.h | 173 +++++++++++++++++++-------
 libcxx/include/latch                  |  11 +-
 libcxx/include/semaphore              |  13 +-
 5 files changed, 190 insertions(+), 68 deletions(-)

diff --git a/libcxx/include/__atomic/atomic_base.h b/libcxx/include/__atomic/atomic_base.h
index 3ad3b562c59805..b7eebcb7651aea 100644
--- a/libcxx/include/__atomic/atomic_base.h
+++ b/libcxx/include/__atomic/atomic_base.h
@@ -102,26 +102,42 @@ struct __atomic_base // false
     return std::__cxx_atomic_compare_exchange_strong(std::addressof(__a_), std::addressof(__e), __d, __m, __m);
   }
 
+  friend _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI _Tp
+  __tag_invoke(__atomic_load_cpo, const __atomic_base& __this, memory_order __order) {
+    return __this.load(__order);
+  }
+
+  friend _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI _Tp
+  __tag_invoke(__atomic_load_cpo, const volatile __atomic_base& __this, memory_order __order) {
+    return __this.load(__order);
+  }
+
+  friend _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI __cxx_atomic_impl<_Tp> const*
+  __tag_invoke(__atomic_contention_address_cpo, const __atomic_base& __this) {
+    return std::addressof(__this.__a_);
+  }
+
+  friend _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI __cxx_atomic_impl<_Tp> const volatile*
+  __tag_invoke(__atomic_contention_address_cpo, const volatile __atomic_base& __this) {
+    return std::addressof(__this.__a_);
+  }
+
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void wait(_Tp __v, memory_order __m = memory_order_seq_cst) const
       volatile _NOEXCEPT {
-    std::__cxx_atomic_wait(std::addressof(__a_), __v, __m);
+    std::__atomic_wait(*this, __v, __m);
   }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
   wait(_Tp __v, memory_order __m = memory_order_seq_cst) const _NOEXCEPT {
-    std::__cxx_atomic_wait(std::addressof(__a_), __v, __m);
+    std::__atomic_wait(*this, __v, __m);
   }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() volatile _NOEXCEPT {
-    std::__cxx_atomic_notify_one(std::addressof(__a_));
-  }
-  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() _NOEXCEPT {
-    std::__cxx_atomic_notify_one(std::addressof(__a_));
+    std::__atomic_notify_one(*this);
   }
+  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() _NOEXCEPT { std::__atomic_notify_one(*this); }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() volatile _NOEXCEPT {
-    std::__cxx_atomic_notify_all(std::addressof(__a_));
-  }
-  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() _NOEXCEPT {
-    std::__cxx_atomic_notify_all(std::addressof(__a_));
+    std::__atomic_notify_all(*this);
   }
+  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() _NOEXCEPT { std::__atomic_notify_all(*this); }
 
 #if _LIBCPP_STD_VER >= 20
   _LIBCPP_HIDE_FROM_ABI constexpr __atomic_base() noexcept(is_nothrow_default_constructible_v<_Tp>) : __a_(_Tp()) {}
diff --git a/libcxx/include/__atomic/atomic_flag.h b/libcxx/include/__atomic/atomic_flag.h
index a45a7183547726..f66caf7d1f5217 100644
--- a/libcxx/include/__atomic/atomic_flag.h
+++ b/libcxx/include/__atomic/atomic_flag.h
@@ -15,6 +15,7 @@
 #include <__atomic/memory_order.h>
 #include <__chrono/duration.h>
 #include <__config>
+#include <__memory/addressof.h>
 #include <__thread/support.h>
 #include <cstdint>
 
@@ -47,13 +48,33 @@ struct atomic_flag {
     __cxx_atomic_store(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(false), __m);
   }
 
+  friend _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_ATOMIC_FLAG_TYPE
+  __tag_invoke(__atomic_load_cpo, const atomic_flag& __this, memory_order __order) {
+    return std::__cxx_atomic_load(&__this.__a_, __order);
+  }
+
+  friend _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_ATOMIC_FLAG_TYPE
+  __tag_invoke(__atomic_load_cpo, const volatile atomic_flag& __this, memory_order __order) {
+    return std::__cxx_atomic_load(&__this.__a_, __order);
+  }
+
+  friend _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI __cxx_atomic_impl<_LIBCPP_ATOMIC_FLAG_TYPE> const*
+  __tag_invoke(__atomic_contention_address_cpo, const atomic_flag& __this) {
+    return std::addressof(__this.__a_);
+  }
+
+  friend _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI __cxx_atomic_impl<_LIBCPP_ATOMIC_FLAG_TYPE> const volatile*
+  __tag_invoke(__atomic_contention_address_cpo, const volatile atomic_flag& __this) {
+    return std::addressof(__this.__a_);
+  }
+
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void wait(bool __v, memory_order __m = memory_order_seq_cst) const
       volatile _NOEXCEPT {
-    __cxx_atomic_wait(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(__v), __m);
+    std::__atomic_wait(*this, _LIBCPP_ATOMIC_FLAG_TYPE(__v), __m);
   }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
   wait(bool __v, memory_order __m = memory_order_seq_cst) const _NOEXCEPT {
-    __cxx_atomic_wait(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(__v), __m);
+    std::__atomic_wait(*this, _LIBCPP_ATOMIC_FLAG_TYPE(__v), __m);
   }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() volatile _NOEXCEPT {
     __cxx_atomic_notify_one(&__a_);
diff --git a/libcxx/include/__atomic/atomic_sync.h b/libcxx/include/__atomic/atomic_sync.h
index e1994ddde86c19..12f70f9a936590 100644
--- a/libcxx/include/__atomic/atomic_sync.h
+++ b/libcxx/include/__atomic/atomic_sync.h
@@ -18,7 +18,10 @@
 #include <__memory/addressof.h>
 #include <__thread/poll_with_backoff.h>
 #include <__thread/support.h>
+#include <__type_traits/conjunction.h>
 #include <__type_traits/decay.h>
+#include <__type_traits/invoke.h>
+#include <__utility/declval.h>
 #include <cstring>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -27,6 +30,57 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+// The customisation points to enable the following functions:
+// - __atomic_wait
+// - __atomic_wait_unless
+// - __atomic_notify_one
+// - __atomic_notify_all
+// Note that std::atomic<T>::wait was back-ported to C++03
+// there the below implementations look ugly to support C++03
+
+struct __atomic_load_cpo {
+  template <class _Tp>
+  using _Ret = decltype(__tag_invoke(
+      std::declval<__atomic_load_cpo>(), std::declval<const _Tp&>(), std::declval<memory_order>()));
+
+  template <class _Tp>
+  _Ret<_Tp> operator()(const _Tp& __t, memory_order __order) const _NOEXCEPT {
+    return __tag_invoke(*this, __t, __order);
+  }
+};
+// TODO: if we can deprecate std::atomic<T>::wait before c++17, we could add
+// inline constexpr __atomic_load_cpo __atomic_load{};
+
+struct __atomic_contention_address_cpo {
+  template <class _Tp>
+  using _Ret = decltype(__tag_invoke(std::declval<__atomic_contention_address_cpo>(), std::declval<const _Tp&>()));
+
+  template <class _Tp>
+  _Ret<_Tp> operator()(const _Tp& __t) const _NOEXCEPT {
+    return __tag_invoke(*this, __t);
+  }
+};
+// TODO: if we can deprecate std::atomic<T>::wait before c++17, we could add
+// inline constexpr __atomic_contention_address_cpo __atomic_contention_address{};
+
+template <class _Tp>
+using __atomic_waitable =
+    _And<__invokable<__atomic_load_cpo, const _Tp&, memory_order>,
+         __invokable<__atomic_contention_address_cpo, const _Tp&> >;
+
+template <class _AtomicWaitable, class _Poll>
+struct __atomic_wait_poll_impl {
+  const _AtomicWaitable& __a_;
+  _Poll __poll_;
+  memory_order __order_;
+
+  _LIBCPP_HIDE_FROM_ABI bool operator()() const {
+    __atomic_load_cpo __atomic_load = {};
+    auto __current_val              = __atomic_load(__a_, __order_);
+    return __poll_(__current_val);
+  }
+};
+
 #ifndef _LIBCPP_HAS_NO_THREADS
 
 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_EXPORTED_FROM_ABI void __cxx_atomic_notify_one(void const volatile*);
@@ -43,17 +97,42 @@ __libcpp_atomic_monitor(__cxx_atomic_contention_t const volatile*);
 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_EXPORTED_FROM_ABI void
 __libcpp_atomic_wait(__cxx_atomic_contention_t const volatile*, __cxx_contention_t);
 
-template <class _Atp, class _BackoffTest>
-struct __libcpp_atomic_wait_backoff_impl {
-  _Atp* __a_;
-  _BackoffTest __backoff_test_;
+template <class _AtomicWaitable, class _Poll>
+struct __atomic_wait_backoff_impl {
+  const _AtomicWaitable& __a_;
+  _Poll __poll_;
+  memory_order __order_;
+
+  _LIBCPP_AVAILABILITY_SYNC
+  _LIBCPP_HIDE_FROM_ABI bool
+  __update_monitor_val_and_poll(__cxx_atomic_contention_t const volatile*, __cxx_contention_t& __monitor_val) const {
+    // In case the contention type happens to be __cxx_atomic_contention_t, i.e. __cxx_atomic_impl<int64_t>,
+    // the platform wait is directly monitoring the atomic value itself.
+    __atomic_load_cpo __atomic_load = {};
+    __monitor_val                   = __atomic_load(__a_, __order_);
+    return __poll_(__monitor_val);
+  }
+
+  _LIBCPP_AVAILABILITY_SYNC
+  _LIBCPP_HIDE_FROM_ABI bool
+  __update_monitor_val_and_poll(void const volatile* __contention_address, __cxx_contention_t& __monitor_val) const {
+    // In case the contention type is anything else, platform wait is monitoring a __cxx_atomic_contention_t
+    // from the global pool, the monitor comes from __libcpp_atomic_monitor
+    __monitor_val                   = std::__libcpp_atomic_monitor(__contention_address);
+    __atomic_load_cpo __atomic_load = {};
+    auto __current_val              = __atomic_load(__a_, __order_);
+    return __poll_(__current_val);
+  }
+
   _LIBCPP_AVAILABILITY_SYNC
   _LIBCPP_HIDE_FROM_ABI bool operator()(chrono::nanoseconds __elapsed) const {
     if (__elapsed > chrono::microseconds(64)) {
-      auto __monitor = std::__libcpp_atomic_monitor(__a_);
-      if (__backoff_test_(__monitor))
+      __atomic_contention_address_cpo __atomic_contention_address = {};
+      auto __contention_address                                   = __atomic_contention_address(__a_);
+      __cxx_contention_t __monitor_val;
+      if (__update_monitor_val_and_poll(__contention_address, __monitor_val))
         return true;
-      std::__libcpp_atomic_wait(__a_, __monitor);
+      std::__libcpp_atomic_wait(__contention_address, __monitor_val);
     } else if (__elapsed > chrono::microseconds(4))
       __libcpp_thread_yield();
     else {
@@ -62,37 +141,46 @@ 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) {
+  static_assert(__atomic_waitable<_AtomicWaitable>::value, "");
+  __atomic_wait_poll_impl<_AtomicWaitable, __decay_t<_Poll> > __poll_fn = {__a, __poll, __order};
+  return std::__libcpp_thread_poll_with_backoff(__poll_fn, __spinning_backoff_policy());
+}
+
+template <class _AtomicWaitable>
+_LIBCPP_HIDE_FROM_ABI void __atomic_notify_one(const _AtomicWaitable&) {
+  static_assert(__atomic_waitable<_AtomicWaitable>::value, "");
+}
+
+template <class _AtomicWaitable>
+_LIBCPP_HIDE_FROM_ABI void __atomic_notify_all(const _AtomicWaitable&) {
+  static_assert(__atomic_waitable<_AtomicWaitable>::value, "");
 }
 
 #endif // _LIBCPP_HAS_NO_THREADS
@@ -102,21 +190,20 @@ _LIBCPP_HIDE_FROM_ABI bool __cxx_nonatomic_compare_equal(_Tp const& __lhs, _Tp c
   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>
+_LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void
+__atomic_wait(_AtomicWaitable& __a, _Up __val, memory_order __order) {
+  static_assert(__atomic_waitable<_AtomicWaitable>::value, "");
+  __bind_nonatomic_equal<_Up> __nonatomic_equal = {__val};
+  std::__atomic_wait_unless(__a, __nonatomic_equal, __order);
 }
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/latch b/libcxx/include/latch
index ad7b35579913b3..684244baaaf1e1 100644
--- a/libcxx/include/latch
+++ b/libcxx/include/latch
@@ -97,9 +97,13 @@ public:
     if (__old == __update)
       __a_.notify_all();
   }
-  inline _LIBCPP_HIDE_FROM_ABI bool try_wait() const noexcept { return 0 == __a_.load(memory_order_acquire); }
+  inline _LIBCPP_HIDE_FROM_ABI bool try_wait() const noexcept {
+    auto __value = __a_.load(memory_order_acquire);
+    return try_wait_impl(__value);
+  }
   inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void wait() const {
-    __cxx_atomic_wait(&__a_.__a_, [this]() -> bool { return try_wait(); });
+    std::__atomic_wait_unless(
+        __a_, [this](ptrdiff_t& __value) -> bool { return try_wait_impl(__value); }, memory_order_acquire);
   }
   inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void arrive_and_wait(ptrdiff_t __update = 1) {
     _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(__update >= 0, "latch::arrive_and_wait called with a negative value");
@@ -108,6 +112,9 @@ public:
     count_down(__update);
     wait();
   }
+
+private:
+  _LIBCPP_HIDE_FROM_ABI bool try_wait_impl(ptrdiff_t& __value) const noexcept { return __value == 0; }
 };
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/semaphore b/libcxx/include/semaphore
index 5235d720bf6fee..a49a888d907227 100644
--- a/libcxx/include/semaphore
+++ b/libcxx/include/semaphore
@@ -100,17 +100,8 @@ public:
     }
   }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void acquire() {
-    auto const __poll_fn = [this]() -> bool {
-      auto __old = __a_.load(memory_order_relaxed);
-      return (__old != 0) && __a_.compare_exchange_strong(__old, __old - 1, memory_order_acquire, memory_order_relaxed);
-    };
-    auto const __backoff_test = [this](__cxx_contention_t& __monitor) -> bool {
-      ptrdiff_t __old = __monitor;
-      bool __r        = __try_acquire_impl(__old);
-      __monitor       = static_cast<__cxx_contention_t>(__old);
-      return __r;
-    };
-    __cxx_atomic_wait(&__a_.__a_, __poll_fn, __backoff_test);
+    std::__atomic_wait_unless(
+        __a_, [this](ptrdiff_t& __old) { return __try_acquire_impl(__old); }, memory_order_relaxed);
   }
   template <class _Rep, class _Period>
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool

>From 35f01cd28f09e2f437966c39a8c4fce6b840fa58 Mon Sep 17 00:00:00 2001
From: Hui <hui.xie0621 at gmail.com>
Date: Sun, 11 Feb 2024 20:20:12 +0000
Subject: [PATCH 2/4] adl lint

---
 libcxx/include/__atomic/atomic_sync.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/libcxx/include/__atomic/atomic_sync.h b/libcxx/include/__atomic/atomic_sync.h
index 12f70f9a936590..9adcbaa133ca1b 100644
--- a/libcxx/include/__atomic/atomic_sync.h
+++ b/libcxx/include/__atomic/atomic_sync.h
@@ -38,13 +38,14 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 // Note that std::atomic<T>::wait was back-ported to C++03
 // there the below implementations look ugly to support C++03
 
+// NOLINTBEGIN(libcpp-robust-against-adl)
 struct __atomic_load_cpo {
   template <class _Tp>
   using _Ret = decltype(__tag_invoke(
       std::declval<__atomic_load_cpo>(), std::declval<const _Tp&>(), std::declval<memory_order>()));
 
   template <class _Tp>
-  _Ret<_Tp> operator()(const _Tp& __t, memory_order __order) const _NOEXCEPT {
+  _LIBCPP_HIDE_FROM_ABI _Ret<_Tp> operator()(const _Tp& __t, memory_order __order) const _NOEXCEPT {
     return __tag_invoke(*this, __t, __order);
   }
 };
@@ -56,13 +57,15 @@ struct __atomic_contention_address_cpo {
   using _Ret = decltype(__tag_invoke(std::declval<__atomic_contention_address_cpo>(), std::declval<const _Tp&>()));
 
   template <class _Tp>
-  _Ret<_Tp> operator()(const _Tp& __t) const _NOEXCEPT {
+  _LIBCPP_HIDE_FROM_ABI _Ret<_Tp> operator()(const _Tp& __t) const _NOEXCEPT {
     return __tag_invoke(*this, __t);
   }
 };
 // TODO: if we can deprecate std::atomic<T>::wait before c++17, we could add
 // inline constexpr __atomic_contention_address_cpo __atomic_contention_address{};
 
+// NOLINTEND(libcpp-robust-against-adl)
+
 template <class _Tp>
 using __atomic_waitable =
     _And<__invokable<__atomic_load_cpo, const _Tp&, memory_order>,

>From 5fda0a21581005fe00caaa05d34cf536f3831ceb Mon Sep 17 00:00:00 2001
From: Hui <hui.xie0621 at gmail.com>
Date: Mon, 12 Feb 2024 12:11:56 +0000
Subject: [PATCH 3/4] ci

---
 libcxx/include/__atomic/atomic_flag.h | 8 ++++----
 libcxx/include/__atomic/atomic_sync.h | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/libcxx/include/__atomic/atomic_flag.h b/libcxx/include/__atomic/atomic_flag.h
index f66caf7d1f5217..a8fac3344a3c21 100644
--- a/libcxx/include/__atomic/atomic_flag.h
+++ b/libcxx/include/__atomic/atomic_flag.h
@@ -77,13 +77,13 @@ struct atomic_flag {
     std::__atomic_wait(*this, _LIBCPP_ATOMIC_FLAG_TYPE(__v), __m);
   }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() volatile _NOEXCEPT {
-    __cxx_atomic_notify_one(&__a_);
+    std::__atomic_notify_one(*this);
   }
-  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() _NOEXCEPT { __cxx_atomic_notify_one(&__a_); }
+  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_one() _NOEXCEPT { std::__atomic_notify_one(*this); }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() volatile _NOEXCEPT {
-    __cxx_atomic_notify_all(&__a_);
+    std::__atomic_notify_all(*this);
   }
-  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() _NOEXCEPT { __cxx_atomic_notify_all(&__a_); }
+  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() _NOEXCEPT { std::__atomic_notify_all(*this); }
 
 #if _LIBCPP_STD_VER >= 20
   _LIBCPP_HIDE_FROM_ABI constexpr atomic_flag() _NOEXCEPT : __a_(false) {}
diff --git a/libcxx/include/__atomic/atomic_sync.h b/libcxx/include/__atomic/atomic_sync.h
index 9adcbaa133ca1b..8c830aa7b0bd43 100644
--- a/libcxx/include/__atomic/atomic_sync.h
+++ b/libcxx/include/__atomic/atomic_sync.h
@@ -173,7 +173,7 @@ template <class _AtomicWaitable, class _Poll>
 _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_fn = {__a, __poll, __order};
-  return std::__libcpp_thread_poll_with_backoff(__poll_fn, __spinning_backoff_policy());
+  std::__libcpp_thread_poll_with_backoff(__poll_fn, __spinning_backoff_policy());
 }
 
 template <class _AtomicWaitable>

>From 877bc78068e1337dc5f6ced0b62a50da4b886110 Mon Sep 17 00:00:00 2001
From: Hui <hui.xie0621 at gmail.com>
Date: Mon, 12 Feb 2024 17:50:15 +0000
Subject: [PATCH 4/4] try again

---
 libcxx/include/__atomic/atomic_sync.h | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/libcxx/include/__atomic/atomic_sync.h b/libcxx/include/__atomic/atomic_sync.h
index 8c830aa7b0bd43..b641d442cd734b 100644
--- a/libcxx/include/__atomic/atomic_sync.h
+++ b/libcxx/include/__atomic/atomic_sync.h
@@ -171,20 +171,15 @@ _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void __atomic_notify_all(const _
 
 template <class _AtomicWaitable, class _Poll>
 _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_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&) {
-  static_assert(__atomic_waitable<_AtomicWaitable>::value, "");
-}
+_LIBCPP_HIDE_FROM_ABI void __atomic_notify_one(const _AtomicWaitable&) {}
 
 template <class _AtomicWaitable>
-_LIBCPP_HIDE_FROM_ABI void __atomic_notify_all(const _AtomicWaitable&) {
-  static_assert(__atomic_waitable<_AtomicWaitable>::value, "");
-}
+_LIBCPP_HIDE_FROM_ABI void __atomic_notify_all(const _AtomicWaitable&) {}
 
 #endif // _LIBCPP_HAS_NO_THREADS
 



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