[gcc(refs/users/kmatsui/heads/remove_pointer)] libstdc++: use new built-in trait __remove_pointer

[Ken Matsui <kmatsui@gcc.gnu.org>]

https://gcc.gnu.org/g:811b961b748b7a1d6dbc4bedf3ae7400ebcc0584

commit 811b961b748b7a1d6dbc4bedf3ae7400ebcc0584
Author: Ken Matsui <kmatsui@gcc.gnu.org>
Date:   Mon Mar 20 14:05:48 2023 -0700

    libstdc++: use new built-in trait __remove_pointer
    
    This patch lets libstdc++ use new built-in trait __remove_pointer.
    
    libstdc++-v3/ChangeLog:
    
            * include/std/type_traits (remove_pointer): Use __remove_pointer built-in trait.
    
    Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>

Diff:
---
 libstdc++-v3/include/std/type_traits | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 0e7a9c9c7f3..81497e2f3e1 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -2023,6 +2023,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   // Pointer modifications.
 
+  /// remove_pointer
+#if __has_builtin(__remove_pointer)
+  template<typename _Tp>
+    struct remove_pointer
+    { using type = __remove_pointer(_Tp); };
+#else
   template<typename _Tp, typename>
     struct __remove_pointer_helper
     { using type = _Tp; };
@@ -2031,11 +2037,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct __remove_pointer_helper<_Tp, _Up*>
     { using type = _Up; };
 
-  /// remove_pointer
   template<typename _Tp>
     struct remove_pointer
     : public __remove_pointer_helper<_Tp, __remove_cv_t<_Tp>>
     { };
+#endif
 
   template<typename _Tp, typename = void>
     struct __add_pointer_helper