[PATCH v4 4/4] libstdc++: Optimize is_compound trait performance

[Ken Matsui via Gcc-patches]

This patch optimizes the performance of the is_compound trait by
dispatching to the new __is_arithmetic built-in trait.

libstdc++-v3/ChangeLog:

        * include/std/type_traits (is_compound): Use __is_arithmetic
        built-in trait.
        (is_compound_v): Use is_fundamental_v instead.

Signed-off-by: Ken Matsui <kmat...@gcc.gnu.org>
---
 libstdc++-v3/include/std/type_traits | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/type_traits 
b/libstdc++-v3/include/std/type_traits
index cf24de2fcac..73d9a2b16fc 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -702,9 +702,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { };
 
   /// is_compound
+#if __has_builtin(__is_arithmetic)
+  template<typename _Tp>
+    struct is_compound
+    : public __bool_constant<!(__is_arithmetic(_Tp)
+                             || is_void<_Tp>::value
+                             || is_null_pointer<_Tp>::value)>
+    { };
+#else
   template<typename _Tp>
     struct is_compound
     : public __not_<is_fundamental<_Tp>>::type { };
+#endif
 
   /// @cond undocumented
   template<typename _Tp>
@@ -3234,7 +3243,7 @@ template <typename _Tp>
 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;
+  inline constexpr bool is_compound_v = !is_fundamental_v<_Tp>;
 template <typename _Tp>
   inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
 template <typename _Tp>
-- 
2.41.0