From 7fd9c349e455345a8b94d8fcee1c92b5c92873a5 Mon Sep 17 00:00:00 2001
From: Ken Matsui <kmatsui@gcc.gnu.org>
Date: Tue, 21 Mar 2023 08:57:14 -0700
Subject: [PATCH] libstdc++: Optimize std::is_array compilation performance

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

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_array): Use __is_array built-in
	trait.
	(is_array_v): Likewise.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
---
 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 677cd934b94..64f9d67fe29 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -523,6 +523,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { };
 
   /// is_array
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_array)
+  template<typename _Tp>
+    struct is_array
+    : public __bool_constant<__is_array(_Tp)>
+    { };
+#else
   template<typename>
     struct is_array
     : public false_type { };
@@ -534,6 +540,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_array<_Tp[]>
     : public true_type { };
+#endif
 
   template<typename>
     struct __is_pointer_helper
@@ -3169,12 +3176,17 @@ template <typename _Tp>
 template <typename _Tp>
   inline constexpr bool is_floating_point_v = is_floating_point<_Tp>::value;
 
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_array)
+template <typename _Tp>
+  inline constexpr bool is_array_v = __is_array(_Tp);
+#else
 template <typename _Tp>
   inline constexpr bool is_array_v = false;
 template <typename _Tp>
   inline constexpr bool is_array_v<_Tp[]> = true;
 template <typename _Tp, size_t _Num>
   inline constexpr bool is_array_v<_Tp[_Num]> = true;
+#endif
 
 template <typename _Tp>
   inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;
-- 
2.11.4.GIT