Re: [PATCH v26 09/13] libstdc++: Optimize std::add_rvalue_reference compilation performance

[Jonathan Wakely]

On 11/05/24 02:01 -0700, Ken Matsui wrote:

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

libstdc++-v3/ChangeLog:

        * include/std/type_traits (add_rvalue_reference): Use
        __add_rvalue_reference built-in trait.
        (__add_rvalue_reference_helper): Likewise.

Signed-off-by: Ken Matsui <kmat...@gcc.gnu.org>
---
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 effa3fbcb75..824cad90a25 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -1185,6 +1185,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    };

  /// @cond undocumented
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__add_rvalue_reference)
+  template<typename _Tp>
+    struct __add_rvalue_reference_helper
+    { using type = __add_rvalue_reference(_Tp); };
+#else
  template<typename _Tp, typename = void>
    struct __add_rvalue_reference_helper
    { using type = _Tp; };
@@ -1192,6 +1197,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
  template<typename _Tp>
    struct __add_rvalue_reference_helper<_Tp, __void_t<_Tp&&>>
    { using type = _Tp&&; };
+#endif

  template<typename _Tp>
    using __add_rval_ref_t = typename __add_rvalue_reference_helper<_Tp>::type;

Same comment as for add_lvalue_reference.

@@ -1748,9 +1754,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif

  /// add_rvalue_reference
+#if _GLIBCXX_USE_BUILTIN_TRAIT(__add_rvalue_reference)
+  template<typename _Tp>
+    struct add_rvalue_reference
+    { using type = __add_rvalue_reference(_Tp); };
+#else
  template<typename _Tp>
    struct add_rvalue_reference
    { using type = __add_rval_ref_t<_Tp>; };
+#endif

#if __cplusplus > 201103L
  /// Alias template for remove_reference
--
2.44.0