[gcc r14-6625] libstdc++: Optimize std::is_scoped_enum compilation performance

[gcc r14-6625] libstdc++: Optimize std::is_scoped_enum compilation performance

[Ken Matsui]

https://gcc.gnu.org/g:4a235f8eb0f19292c007c4374d6b48ab01667a3b

commit r14-6625-g4a235f8eb0f19292c007c4374d6b48ab01667a3b
Author: Ken Matsui <kmatsui@gcc.gnu.org>
Date:   Mon Sep 11 17:14:32 2023 -0700

    libstdc++: Optimize std::is_scoped_enum compilation performance
    
    This patch optimizes the compilation performance of std::is_scoped_enum
    by dispatching to the new __is_scoped_enum built-in trait.
    
    libstdc++-v3/ChangeLog:
    
            * include/std/type_traits (is_scoped_enum): Use
            __is_scoped_enum built-in trait.
            (is_scoped_enum_v): Likewise.
    
    Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
    Reviewed-by: Jonathan Wakely <jwakely@redhat.com>

Diff:
---
 libstdc++-v3/include/std/type_traits | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 2a1a0aa80ff..4a5068791af 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -3602,6 +3602,12 @@ template<typename _Ret, typename _Fn, typename... _Args>
   /// True if the type is a scoped enumeration type.
   /// @since C++23
 
+# if _GLIBCXX_USE_BUILTIN_TRAIT(__is_scoped_enum)
+  template<typename _Tp>
+    struct is_scoped_enum
+    : bool_constant<__is_scoped_enum(_Tp)>
+    { };
+# else
   template<typename _Tp>
     struct is_scoped_enum
     : false_type
@@ -3613,11 +3619,17 @@ template<typename _Ret, typename _Fn, typename... _Args>
     struct is_scoped_enum<_Tp>
     : bool_constant<!requires(_Tp __t, void(*__f)(int)) { __f(__t); }>
     { };
+# endif
 
   /// @ingroup variable_templates
   /// @since C++23
+# if _GLIBCXX_USE_BUILTIN_TRAIT(__is_scoped_enum)
+  template<typename _Tp>
+    inline constexpr bool is_scoped_enum_v = __is_scoped_enum(_Tp);
+# else
   template<typename _Tp>
     inline constexpr bool is_scoped_enum_v = is_scoped_enum<_Tp>::value;
+# endif
 #endif
 
 #ifdef __cpp_lib_reference_from_temporary // C++ >= 23 && ref_{converts,constructs}_from_temp