[gcc r15-1249] libstdc++: Optimize std::remove_extent compilation performance

[Ken Matsui]

https://gcc.gnu.org/g:d5e994f44653b913e24753351e713befffbf1a01

commit r15-1249-gd5e994f44653b913e24753351e713befffbf1a01
Author: Ken Matsui <kmatsui@gcc.gnu.org>
Date:   Wed Feb 14 05:50:49 2024 -0800

    libstdc++: Optimize std::remove_extent compilation performance
    
    This patch optimizes the compilation performance of std::remove_extent
    by dispatching to the new __remove_extent built-in trait.
    
    libstdc++-v3/ChangeLog:
    
            * include/std/type_traits (remove_extent): Use __remove_extent
            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:
---
 libstdc++-v3/include/std/type_traits | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index e179015be934..02d7a3e50171 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -2078,6 +2078,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // Array modifications.
 
   /// remove_extent
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__remove_extent)
+  template<typename _Tp>
+    struct remove_extent
+    { using type = __remove_extent(_Tp); };
+#else
   template<typename _Tp>
     struct remove_extent
     { using type = _Tp; };
@@ -2089,6 +2094,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct remove_extent<_Tp[]>
     { using type = _Tp; };
+#endif
 
   /// remove_all_extents
   template<typename _Tp>