[libc++] constexpr atomic and atomic_ref

llvm · Jul 14, 2024 · 8eb0435 · 8eb0435
1 parent 125f277
commit 8eb0435
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Showing 8 changed files with 95 additions and 13 deletions.
diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
@@ -402,6 +402,8 @@ Status
     ---------------------------------------------------------- -----------------
     ``__cpp_lib_bitset``                                       ``202306L``
     ---------------------------------------------------------- -----------------
+    ``__cpp_lib_constexpr_atomic``                             ``202406L``
+    ---------------------------------------------------------- -----------------
     ``__cpp_lib_constexpr_new``                                *unimplemented*
     ---------------------------------------------------------- -----------------
     ``__cpp_lib_constrained_equality``                         *unimplemented*

diff --git a/libcxx/include/__atomic/atomic_base.h b/libcxx/include/__atomic/atomic_base.h
@@ -122,23 +122,23 @@ struct __atomic_base // false
     std::__atomic_notify_one(*this);
   }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void notify_one() _NOEXCEPT {
-    if !consteval {
+    if (!__libcpp_is_constant_evaluated()) {
       std::__atomic_notify_one(*this);
     }
   }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void notify_all() volatile _NOEXCEPT {
     std::__atomic_notify_all(*this);
   }
   _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void notify_all() _NOEXCEPT {
-    if !consteval {
+    if (!__libcpp_is_constant_evaluated()) {
       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()) {}
 #else
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __atomic_base() _NOEXCEPT = default;
+  _LIBCPP_HIDE_FROM_ABI __atomic_base() _NOEXCEPT = default;
 #endif
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __atomic_base(_Tp __d) _NOEXCEPT : __a_(__d) {}

diff --git a/libcxx/include/__atomic/atomic_ref.h b/libcxx/include/__atomic/atomic_ref.h
@@ -27,6 +27,7 @@
 #include <__memory/addressof.h>
 #include <__type_traits/has_unique_object_representation.h>
 #include <__type_traits/is_trivially_copyable.h>
+#include <__utility/exchange.h>
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
@@ -148,9 +149,7 @@ struct __atomic_ref_base {
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 _Tp
   exchange(_Tp __desired, memory_order __order = memory_order::seq_cst) const noexcept {
     if (__libcpp_is_constant_evaluated()) {
-      _Tp tmp = *__ptr_;
-      *__ptr_ = __desired;
-      return tmp;
+      return std::exchange(*__ptr_, __desired);
     } else {
       alignas(_Tp) byte __mem[sizeof(_Tp)];
       auto* __ret = reinterpret_cast<_Tp*>(__mem);
@@ -273,12 +272,12 @@ struct __atomic_ref_base {
     }
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void notify_one() const noexcept {
-    if !consteval {
+    if (!__libcpp_is_constant_evaluated()) {
       std::__atomic_notify_one(*this);
     }
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void notify_all() const noexcept {
-    if !consteval {
+    if (!__libcpp_is_constant_evaluated()) {
       std::__atomic_notify_all(*this);
     }
   }

diff --git a/libcxx/include/__atomic/cxx_atomic_impl.h b/libcxx/include/__atomic/cxx_atomic_impl.h
@@ -14,6 +14,7 @@
 #include <__config>
 #include <__memory/addressof.h>
 #include <__type_traits/is_assignable.h>
+#include <__type_traits/is_constant_evaluated.h>
 #include <__type_traits/is_trivially_copyable.h>
 #include <__type_traits/remove_const.h>
 #include <cstddef>
@@ -283,11 +284,15 @@ struct __cxx_atomic_base_impl {
 #  define __cxx_atomic_is_lock_free(__s) __c11_atomic_is_lock_free(__s)
 
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR inline void __cxx_atomic_thread_fence(memory_order __order) _NOEXCEPT {
-  __c11_atomic_thread_fence(static_cast<__memory_order_underlying_t>(__order));
+  if (!__libcpp_is_constant_evaluated()) {
+    __c11_atomic_thread_fence(static_cast<__memory_order_underlying_t>(__order));
+  }
 }
 
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR inline void __cxx_atomic_signal_fence(memory_order __order) _NOEXCEPT {
-  __c11_atomic_signal_fence(static_cast<__memory_order_underlying_t>(__order));
+  if (!__libcpp_is_constant_evaluated()) {
+    __c11_atomic_signal_fence(static_cast<__memory_order_underlying_t>(__order));
+  }
 }
 
 template <class _Tp>

diff --git a/libcxx/include/version b/libcxx/include/version
@@ -61,6 +61,7 @@ __cpp_lib_clamp                                         201603L <algorithm>
 __cpp_lib_complex_udls                                  201309L <complex>
 __cpp_lib_concepts                                      202002L <concepts>
 __cpp_lib_constexpr_algorithms                          201806L <algorithm> <utility>
+__cpp_lib_constexpr_atomic                              202406L <atomic>
 __cpp_lib_constexpr_bitset                              202207L <bitset>
 __cpp_lib_constexpr_charconv                            202207L <charconv>
 __cpp_lib_constexpr_cmath                               202202L <cmath> <cstdlib>
@@ -384,9 +385,6 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # endif
 # define __cpp_lib_concepts                             202002L
 # define __cpp_lib_constexpr_algorithms                 201806L
-# if __has_constexpr_builtin(__c11_atomic_load)
-# define __cpp_constexpr_atomic                         202406L
-# endif
 # define __cpp_lib_constexpr_complex                    201711L
 # define __cpp_lib_constexpr_dynamic_alloc              201907L
 # define __cpp_lib_constexpr_functional                 201907L
@@ -509,6 +507,9 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # undef  __cpp_lib_bind_front
 # define __cpp_lib_bind_front                           202306L
 # define __cpp_lib_bitset                               202306L
+# if __has_constexpr_builtin(__c11_atomic_load)
+#   define __cpp_lib_constexpr_atomic                   202406L
+# endif
 // # define __cpp_lib_constexpr_new                        202406L
 // # define __cpp_lib_constrained_equality                 202403L
 // # define __cpp_lib_copyable_function                    202306L

diff --git a/...td/language.support/support.limits/support.limits.general/atomic.version.compile.pass.cpp b/...td/language.support/support.limits/support.limits.general/atomic.version.compile.pass.cpp
@@ -26,6 +26,7 @@
     __cpp_lib_atomic_value_initialization      201911L [C++20]
     __cpp_lib_atomic_wait                      201907L [C++20]
     __cpp_lib_char8_t                          201907L [C++20]
+    __cpp_lib_constexpr_atomic                 202406L [C++26]
 */
 
 #include <atomic>
@@ -73,6 +74,10 @@
 #   error "__cpp_lib_char8_t should not be defined before c++20"
 # endif
 
+# ifdef __cpp_lib_constexpr_atomic
+#   error "__cpp_lib_constexpr_atomic should not be defined before c++26"
+# endif
+
 #elif TEST_STD_VER == 14
 
 # ifdef __cpp_lib_atomic_flag_test
@@ -115,6 +120,10 @@
 #   error "__cpp_lib_char8_t should not be defined before c++20"
 # endif
 
+# ifdef __cpp_lib_constexpr_atomic
+#   error "__cpp_lib_constexpr_atomic should not be defined before c++26"
+# endif
+
 #elif TEST_STD_VER == 17
 
 # ifdef __cpp_lib_atomic_flag_test
@@ -160,6 +169,10 @@
 #   error "__cpp_lib_char8_t should not be defined before c++20"
 # endif
 
+# ifdef __cpp_lib_constexpr_atomic
+#   error "__cpp_lib_constexpr_atomic should not be defined before c++26"
+# endif
+
 #elif TEST_STD_VER == 20
 
 # ifndef __cpp_lib_atomic_flag_test
@@ -253,6 +266,10 @@
 #   endif
 # endif
 
+# ifdef __cpp_lib_constexpr_atomic
+#   error "__cpp_lib_constexpr_atomic should not be defined before c++26"
+# endif
+
 #elif TEST_STD_VER == 23
 
 # ifndef __cpp_lib_atomic_flag_test
@@ -346,6 +363,10 @@
 #   endif
 # endif
 
+# ifdef __cpp_lib_constexpr_atomic
+#   error "__cpp_lib_constexpr_atomic should not be defined before c++26"
+# endif
+
 #elif TEST_STD_VER > 23
 
 # ifndef __cpp_lib_atomic_flag_test
@@ -448,5 +469,18 @@
 #   endif
 # endif
 
+# if __has_constexpr_builtin(__c11_atomic_load)
+#   ifndef __cpp_lib_constexpr_atomic
+#     error "__cpp_lib_constexpr_atomic should be defined in c++26"
+#   endif
+#   if __cpp_lib_constexpr_atomic != 202406L
+#     error "__cpp_lib_constexpr_atomic should have the value 202406L in c++26"
+#   endif
+# else
+#   ifdef __cpp_lib_constexpr_atomic
+#     error "__cpp_lib_constexpr_atomic should not be defined when the requirement '__has_constexpr_builtin(__c11_atomic_load)' is not met!"
+#   endif
+# endif
+
 #endif // TEST_STD_VER > 23
 
diff --git a/...d/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp b/...d/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
@@ -56,6 +56,7 @@
     __cpp_lib_complex_udls                                  201309L [C++14]
     __cpp_lib_concepts                                      202002L [C++20]
     __cpp_lib_constexpr_algorithms                          201806L [C++20]
+    __cpp_lib_constexpr_atomic                              202406L [C++26]
     __cpp_lib_constexpr_bitset                              202207L [C++23]
     __cpp_lib_constexpr_charconv                            202207L [C++23]
     __cpp_lib_constexpr_cmath                               202202L [C++23]
@@ -399,6 +400,10 @@
 #   error "__cpp_lib_constexpr_algorithms should not be defined before c++20"
 # endif
 
+# ifdef __cpp_lib_constexpr_atomic
+#   error "__cpp_lib_constexpr_atomic should not be defined before c++26"
+# endif
+
 # ifdef __cpp_lib_constexpr_bitset
 #   error "__cpp_lib_constexpr_bitset should not be defined before c++23"
 # endif
@@ -1259,6 +1264,10 @@
 #   error "__cpp_lib_constexpr_algorithms should not be defined before c++20"
 # endif
 
+# ifdef __cpp_lib_constexpr_atomic
+#   error "__cpp_lib_constexpr_atomic should not be defined before c++26"
+# endif
+
 # ifdef __cpp_lib_constexpr_bitset
 #   error "__cpp_lib_constexpr_bitset should not be defined before c++23"
 # endif
@@ -2221,6 +2230,10 @@
 #   error "__cpp_lib_constexpr_algorithms should not be defined before c++20"
 # endif
 
+# ifdef __cpp_lib_constexpr_atomic
+#   error "__cpp_lib_constexpr_atomic should not be defined before c++26"
+# endif
+
 # ifdef __cpp_lib_constexpr_bitset
 #   error "__cpp_lib_constexpr_bitset should not be defined before c++23"
 # endif
@@ -3423,6 +3436,10 @@
 #   error "__cpp_lib_constexpr_algorithms should have the value 201806L in c++20"
 # endif
 
+# ifdef __cpp_lib_constexpr_atomic
+#   error "__cpp_lib_constexpr_atomic should not be defined before c++26"
+# endif
+
 # ifdef __cpp_lib_constexpr_bitset
 #   error "__cpp_lib_constexpr_bitset should not be defined before c++23"
 # endif
@@ -4838,6 +4855,10 @@
 #   error "__cpp_lib_constexpr_algorithms should have the value 201806L in c++23"
 # endif
 
+# ifdef __cpp_lib_constexpr_atomic
+#   error "__cpp_lib_constexpr_atomic should not be defined before c++26"
+# endif
+
 # ifndef __cpp_lib_constexpr_bitset
 #   error "__cpp_lib_constexpr_bitset should be defined in c++23"
 # endif
@@ -6472,6 +6493,19 @@
 #   error "__cpp_lib_constexpr_algorithms should have the value 201806L in c++26"
 # endif
 
+# if __has_constexpr_builtin(__c11_atomic_load)
+#   ifndef __cpp_lib_constexpr_atomic
+#     error "__cpp_lib_constexpr_atomic should be defined in c++26"
+#   endif
+#   if __cpp_lib_constexpr_atomic != 202406L
+#     error "__cpp_lib_constexpr_atomic should have the value 202406L in c++26"
+#   endif
+# else
+#   ifdef __cpp_lib_constexpr_atomic
+#     error "__cpp_lib_constexpr_atomic should not be defined when the requirement '__has_constexpr_builtin(__c11_atomic_load)' is not met!"
+#   endif
+# endif
+
 # ifndef __cpp_lib_constexpr_bitset
 #   error "__cpp_lib_constexpr_bitset should be defined in c++26"
 # endif

diff --git a/libcxx/utils/generate_feature_test_macro_components.py b/libcxx/utils/generate_feature_test_macro_components.py
@@ -318,6 +318,13 @@ def add_version_header(tc):
             },
             "headers": ["algorithm", "utility"],
         },
+        {
+            "name": "__cpp_lib_constexpr_atomic",
+            "values": {"c++26": 202406},
+            "headers": ["atomic"],
+            "libcxx_guard": "__has_constexpr_builtin(__c11_atomic_load)",
+            "test_suite_guard": "__has_constexpr_builtin(__c11_atomic_load)",
+        },
         {
             "name": "__cpp_lib_constexpr_bitset",
             "values": {"c++23": 202207},