[gcc r11-3569] libstdc++: Use __is_same instead of __is_same_as

[Jonathan Wakely]

https://gcc.gnu.org/g:73ae6eb572515ad627b575a7fbdfdd47a4368e1c

commit r11-3569-g73ae6eb572515ad627b575a7fbdfdd47a4368e1c
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Sep 30 18:24:48 2020 +0100

    libstdc++: Use __is_same instead of __is_same_as
    
    PR 92271 added __is_same as another spelling of __is_same_as. Since
    Clang also spells it __is_same, let's just use that consistently.
    
    It appears that Intel icc sets __GNUC__ to 10, but only supports
    __is_same_as. If we only use __is_same for __GNUC__ >= 11 then we won't
    break icc again (it looks like we broke previous versions of icc when we
    started using __is_same_as).
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/c++config (_GLIBCXX_HAVE_BUILTIN_IS_SAME):
            Define for GCC 11 or when !__is_identifier(__is_same).
            (_GLIBCXX_BUILTIN_IS_SAME_AS): Remove.
            * include/std/type_traits (is_same, is_same_v): Replace uses
            of _GLIBCXX_BUILTIN_IS_SAME_AS.

Diff:
---
 libstdc++-v3/include/bits/c++config  |  6 ++++--
 libstdc++-v3/include/std/type_traits | 10 +++++-----
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index 860bf6dbcb3..2e6c880ad95 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -658,10 +658,12 @@ namespace std
 # define _GLIBCXX_HAVE_BUILTIN_HAS_UNIQ_OBJ_REP 1
 # define _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE 1
 # define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
-# define _GLIBCXX_BUILTIN_IS_SAME_AS(T, U) __is_same_as(T, U)
 # if __GNUC__ >= 9
 #  define _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED 1
 # endif
+# if __GNUC__ >= 11
+#  define _GLIBCXX_HAVE_BUILTIN_IS_SAME 1
+# endif
 #elif defined(__is_identifier) && defined(__has_builtin)
 // For non-GNU compilers:
 # if ! __is_identifier(__has_unique_object_representations)
@@ -677,7 +679,7 @@ namespace std
 #  define _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED 1
 # endif
 # if ! __is_identifier(__is_same)
-#  define _GLIBCXX_BUILTIN_IS_SAME_AS(T, U) __is_same(T, U)
+#  define _GLIBCXX_HAVE_BUILTIN_IS_SAME 1
 # endif
 #endif // GCC
 
diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index b7bb63bbc74..9994c9ae3d7 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -1394,14 +1394,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   /// is_same
   template<typename _Tp, typename _Up>
     struct is_same
-#ifdef _GLIBCXX_BUILTIN_IS_SAME_AS
-    : public integral_constant<bool, _GLIBCXX_BUILTIN_IS_SAME_AS(_Tp, _Up)>
+#ifdef _GLIBCXX_HAVE_BUILTIN_IS_SAME
+    : public integral_constant<bool, __is_same(_Tp, _Up)>
 #else
     : public false_type
 #endif
     { };
 
-#ifndef _GLIBCXX_BUILTIN_IS_SAME_AS
+#ifndef _GLIBCXX_HAVE_BUILTIN_IS_SAME
   template<typename _Tp>
     struct is_same<_Tp, _Tp>
     : public true_type
@@ -3215,9 +3215,9 @@ template <typename _Tp>
   inline constexpr size_t rank_v = rank<_Tp>::value;
 template <typename _Tp, unsigned _Idx = 0>
   inline constexpr size_t extent_v = extent<_Tp, _Idx>::value;
-#ifdef _GLIBCXX_BUILTIN_IS_SAME_AS
+#ifdef _GLIBCXX_HAVE_BUILTIN_IS_SAME
 template <typename _Tp, typename _Up>
-  inline constexpr bool is_same_v = _GLIBCXX_BUILTIN_IS_SAME_AS(_Tp, _Up);
+  inline constexpr bool is_same_v = __is_same(_Tp, _Up);
 #else
 template <typename _Tp, typename _Up>
   inline constexpr bool is_same_v = std::is_same<_Tp, _Up>::value;