[libcxx-commits] [libcxx] [libc++] Allows any types of size 4 and 8 to use native platform ulock_wait (PR #161086)

[Louis Dionne via libcxx-commits]

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@@ -69,6 +76,113 @@ _LIBCPP_EXPORTED_FROM_ABI __cxx_contention_t
 __libcpp_atomic_monitor(__cxx_atomic_contention_t const volatile*) _NOEXCEPT;
 _LIBCPP_EXPORTED_FROM_ABI void
 __libcpp_atomic_wait(__cxx_atomic_contention_t const volatile*, __cxx_contention_t) _NOEXCEPT;
+#    endif // !_LIBCPP_AVAILABILITY_HAS_NEW_SYNC
+
+// new dylib interface
+
+// return the global contention state's current value for the address
+_LIBCPP_AVAILABILITY_NEW_SYNC _LIBCPP_EXPORTED_FROM_ABI __cxx_contention_t
+__atomic_monitor_global(void const* __address) _NOEXCEPT;
+
+// wait on the global contention state to be changed from the given value for the address
+_LIBCPP_AVAILABILITY_NEW_SYNC _LIBCPP_EXPORTED_FROM_ABI void
+__atomic_wait_global_table(void const* __address, __cxx_contention_t __monitor_value) _NOEXCEPT;
+
+// notify one waiter waiting on the global contention state for the address
+_LIBCPP_AVAILABILITY_NEW_SYNC _LIBCPP_EXPORTED_FROM_ABI void __atomic_notify_one_global_table(void const*) _NOEXCEPT;
+
+// notify all waiters waiting on the global contention state for the address
+_LIBCPP_AVAILABILITY_NEW_SYNC _LIBCPP_EXPORTED_FROM_ABI void __atomic_notify_all_global_table(void const*) _NOEXCEPT;
+
+// wait on the address directly with the native platform wait
+template <std::size_t _Size>
+_LIBCPP_AVAILABILITY_NEW_SYNC _LIBCPP_EXPORTED_FROM_ABI void
+__atomic_wait_native(void const* __address, void const* __old_value) _NOEXCEPT;
+
+// notify one waiter waiting on the address directly with the native platform wait
+template <std::size_t _Size>
+_LIBCPP_AVAILABILITY_NEW_SYNC _LIBCPP_EXPORTED_FROM_ABI void __atomic_notify_one_native(const void*) _NOEXCEPT;
+
+// notify all waiters waiting on the address directly with the native platform wait
+template <std::size_t _Size>
+_LIBCPP_AVAILABILITY_NEW_SYNC _LIBCPP_EXPORTED_FROM_ABI void __atomic_notify_all_native(const void*) _NOEXCEPT;
+
+#    ifdef __linux__
+#      define _LIBCPP_NATIVE_PLATFORM_WAIT_SIZES(_APPLY) _APPLY(4)
+#    elif defined(__APPLE__)
+#      define _LIBCPP_NATIVE_PLATFORM_WAIT_SIZES(_APPLY)                                                               \
+        _APPLY(4)                                                                                                      \
+        _APPLY(8)
+#    elif defined(__FreeBSD__) && __SIZEOF_LONG__ == 8
+#      define _LIBCPP_NATIVE_PLATFORM_WAIT_SIZES(_APPLY) _APPLY(8)
+#    elif defined(_WIN32)
+#      define _LIBCPP_NATIVE_PLATFORM_WAIT_SIZES(_APPLY) _APPLY(8)
+#    else
+#      define _LIBCPP_NATIVE_PLATFORM_WAIT_SIZES(_APPLY) _APPLY(sizeof(__cxx_contention_t))
+#    endif // __linux__
+
+// concepts defines the types are supported natively by the platform's wait
+
+#    if defined(_LIBCPP_ABI_ATOMIC_WAIT_NATIVE_BY_SIZE)
+
+_LIBCPP_HIDE_FROM_ABI constexpr bool __has_native_atomic_wait_impl(size_t __size) {
+  switch (__size) {
+#      define _LIBCPP_MAKE_CASE(n)                                                                                     \
+      case n:                                                                                                          \
+        return true;
+    _LIBCPP_NATIVE_PLATFORM_WAIT_SIZES(_LIBCPP_MAKE_CASE)
+  default:
+    return false;
+#      undef _LIBCPP_MAKE_CASE
+  };
+}
+
+template <class _Tp>
+concept __has_native_atomic_wait =
+    has_unique_object_representations_v<_Tp> && __has_native_atomic_wait_impl(sizeof(_Tp));
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ldionne wrote:

I think we need `is_trivially_copyable` explicitly here, since you do `memcpy` the objects.

https://github.com/llvm/llvm-project/pull/161086