[PATCH 2/2] libstdc++: Optimize is_member_pointer trait performance

[Ken Matsui]

This patch optimizes the performance of the is_member_pointer trait
by dispatching to the new __is_member_pointer built-in trait.

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_member_pointer): Use __is_member_pointer
	built-in trait.
	(is_member_pointer_v): Likewise.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 libstdc++-v3/include/std/type_traits | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 677cd934b94..69dccfa035d 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -709,6 +709,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct is_compound
     : public __not_<is_fundamental<_Tp>>::type { };
 
+  /// is_member_pointer
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_member_pointer)
+  template<typename _Tp>
+    struct is_member_pointer
+    : public __bool_constant<__is_member_pointer(_Tp)>
+    { };
+#else
   /// @cond undocumented
   template<typename _Tp>
     struct __is_member_pointer_helper
@@ -719,11 +726,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     : public true_type { };
   /// @endcond
 
-  /// is_member_pointer
   template<typename _Tp>
     struct is_member_pointer
     : public __is_member_pointer_helper<__remove_cv_t<_Tp>>::type
     { };
+#endif
 
   template<typename, typename>
     struct is_same;
@@ -3216,8 +3223,15 @@ template <typename _Tp>
   inline constexpr bool is_scalar_v = is_scalar<_Tp>::value;
 template <typename _Tp>
   inline constexpr bool is_compound_v = is_compound<_Tp>::value;
+
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_member_pointer)
+template <typename _Tp>
+  inline constexpr bool is_member_pointer_v = __is_member_pointer(_Tp);
+#else
 template <typename _Tp>
   inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
+#endif
+
 template <typename _Tp>
   inline constexpr bool is_const_v = false;
 template <typename _Tp>
-- 
2.42.0