[gcc r15-9752] libstdc++: Compare keys and values separately in flat_map::operator==

[Patrick Palka]

https://gcc.gnu.org/g:771fcb9fe9b3fce8336a797c03c399a63e11eb21

commit r15-9752-g771fcb9fe9b3fce8336a797c03c399a63e11eb21
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu May 29 10:12:23 2025 -0400

    libstdc++: Compare keys and values separately in flat_map::operator==
    
    Instead of effectively doing a zipped comparison of the keys and values,
    compare them separately to leverage the underlying containers' optimized
    equality implementations.
    
    libstdc++-v3/ChangeLog:
    
            * include/std/flat_map (_Flat_map_impl::operator==): Compare
            keys and values separately.
    
    Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
    (cherry picked from commit ad96f0344adfc847874b34b43f30371979ae9963)

Diff:
---
 libstdc++-v3/include/std/flat_map | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/flat_map b/libstdc++-v3/include/std/flat_map
index cec7f36cff9f..4bd4963c2ad7 100644
--- a/libstdc++-v3/include/std/flat_map
+++ b/libstdc++-v3/include/std/flat_map
@@ -873,7 +873,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       [[nodiscard]]
       friend bool
       operator==(const _Derived& __x, const _Derived& __y)
-      { return std::equal(__x.begin(), __x.end(), __y.begin(), __y.end()); }
+      {
+	return __x._M_cont.keys == __y._M_cont.keys
+	  && __x._M_cont.values == __y._M_cont.values;
+      }
 
       template<typename _Up = value_type>
 	[[nodiscard]]