libstdc++: Optimize std::add_pointer compilation performance

This patch optimizes the compilation performance of std::add_pointer
by dispatching to the new __add_pointer built-in trait.

libstdc++-v3/ChangeLog:

	* include/std/type_traits (add_pointer): Use __add_pointer
	built-in trait.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Patrick Palka <ppalka@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index efbe273d38a9b0efa1474b78b2adf41377e5d182..e179015be9342914b78b49cc49069fc3cb4d6ed5 100644 (file)
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -2135,6 +2135,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { };
 #endif
 
+  /// add_pointer
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__add_pointer)
+  template<typename _Tp>
+    struct add_pointer
+    { using type = __add_pointer(_Tp); };
+#else
   template<typename _Tp, typename = void>
     struct __add_pointer_helper
     { using type = _Tp; };
@@ -2143,7 +2149,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     struct __add_pointer_helper<_Tp, __void_t<_Tp*>>
     { using type = _Tp*; };
 
-  /// add_pointer
   template<typename _Tp>
     struct add_pointer
     : public __add_pointer_helper<_Tp>
@@ -2156,6 +2161,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct add_pointer<_Tp&&>
     { using type = _Tp*; };
+#endif
 
 #if __cplusplus > 201103L
   /// Alias template for remove_pointer