libstdc++: Improve unordered containers == operator (PR 91263)

Avoid comparing elements with operator== multiple times by replacing
uses of find and equal_range with equivalent inlined code that uses
operator== instead of the container's equality comparison predicate.
This is valid because the standard requires that operator== is a
refinement of the equality predicate.

Also replace the _S_is_permutation function with std::is_permutation,
which wasn't yet implemented when this code was first written.

	PR libstdc++/91263
	* include/bits/hashtable.h (_Hashtable<>): Make _Equality<> friend.
	* include/bits/hashtable_policy.h: Include <bits/stl_algo.h>.
	(_Equality_base): Remove.
	(_Equality<>::_M_equal): Review implementation. Use
	std::is_permutation.
	* testsuite/23_containers/unordered_multiset/operators/1.cc
	(Hash, Equal, test02, test03): New.
	* testsuite/23_containers/unordered_set/operators/1.cc
	(Hash, Equal, test02, test03): New.

1 files changed, 7 insertions, 0 deletions

diff --git a/libstdc++-v3/include/bits/hashtable.h b/libstdc++-v3/include/bits/hashtable.h
index 8fac385..9e721aa 100644
--- a/libstdc++-v3/include/bits/hashtable.h
+++ b/libstdc++-v3/include/bits/hashtable.h
@@ -337,6 +337,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	       bool _Constant_iteratorsa>
 	friend struct __detail::_Insert;
 
+      template<typename _Keya, typename _Valuea, typename _Alloca,
+	       typename _ExtractKeya, typename _Equala,
+	       typename _H1a, typename _H2a, typename _Hasha,
+	       typename _RehashPolicya, typename _Traitsa,
+	       bool _Unique_keysa>
+	friend struct __detail::_Equality;
+
     public:
       using size_type = typename __hashtable_base::size_type;
       using difference_type = typename __hashtable_base::difference_type;