Remove unnecessary non-const accessors in hash table bases

The const accessors are OK (and arguably more correct) for most callers
to use. The _M_swap functions that use the non-const overloads can just
directly use the _S_get members of the EBO helpers.

	* include/bits/hashtable_policy.h (_Hash_code_base::_M_swap): Use
	_S_get accessors for members in EBO helpers.
	(_Hash_code_base::_M_extract(), _Hash_code_base::_M_ranged_hash())
	(_Hash_code_base::_M_h1(), _Hash_code_base::_M_h2()): Remove non-const
	overloads.
	(_Hashtable_base::_M_swap): Use _S_get accessors for members in EBO
	helpers.
	(_Hashtable_base::_M_eq()): Remove non-const overload.

From-SVN: r271286

libstdc++-v3/ChangeLog

+2019-05-16  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/bits/hashtable_policy.h (_Hash_code_base::_M_swap): Use
+	_S_get accessors for members in EBO helpers.
+	(_Hash_code_base::_M_extract(), _Hash_code_base::_M_ranged_hash())
+	(_Hash_code_base::_M_h1(), _Hash_code_base::_M_h2()): Remove non-const
+	overloads.
+	(_Hashtable_base::_M_swap): Use _S_get accessors for members in EBO
+	helpers.
+	(_Hashtable_base::_M_eq()): Remove non-const overload.
+
 2019-05-15  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/std/variant (visit, visit<R>): Qualify calls to __do_visit.

libstdc++-v3/include/bits/hashtable_policy.h

@@ -1229,21 +1229,16 @@ namespace __detail
       void
       _M_swap(_Hash_code_base& __x)
       {
-	std::swap(_M_extract(), __x._M_extract());
-	std::swap(_M_ranged_hash(), __x._M_ranged_hash());
+	std::swap(__ebo_extract_key::_S_get(*this),
+		  __ebo_extract_key::_S_get(__x));
+	std::swap(__ebo_hash::_S_get(*this), __ebo_hash::_S_get(__x));
       }
 
       const _ExtractKey&
       _M_extract() const { return __ebo_extract_key::_S_cget(*this); }
 
-      _ExtractKey&
-      _M_extract() { return __ebo_extract_key::_S_get(*this); }
-
       const _Hash&
       _M_ranged_hash() const { return __ebo_hash::_S_cget(*this); }
-
-      _Hash&
-      _M_ranged_hash() { return __ebo_hash::_S_get(*this); }
     };
 
   // No specialization for ranged hash function while caching hash codes.
@@ -1322,28 +1317,20 @@ namespace __detail
       void
       _M_swap(_Hash_code_base& __x)
       {
-	std::swap(_M_extract(), __x._M_extract());
-	std::swap(_M_h1(), __x._M_h1());
-	std::swap(_M_h2(), __x._M_h2());
+	std::swap(__ebo_extract_key::_S_get(*this),
+		  __ebo_extract_key::_S_get(__x));
+	std::swap(__ebo_h1::_S_get(*this), __ebo_h1::_S_get(__x));
+	std::swap(__ebo_h2::_S_get(*this), __ebo_h2::_S_get(__x));
       }
 
       const _ExtractKey&
       _M_extract() const { return __ebo_extract_key::_S_cget(*this); }
 
-      _ExtractKey&
-      _M_extract() { return __ebo_extract_key::_S_get(*this); }
-
       const _H1&
       _M_h1() const { return __ebo_h1::_S_cget(*this); }
 
-      _H1&
-      _M_h1() { return __ebo_h1::_S_get(*this); }
-
       const _H2&
       _M_h2() const { return __ebo_h2::_S_cget(*this); }
-
-      _H2&
-      _M_h2() { return __ebo_h2::_S_get(*this); }
     };
 
   /// Specialization: hash function and range-hashing function,
@@ -1410,28 +1397,20 @@ namespace __detail
       void
       _M_swap(_Hash_code_base& __x)
       {
-	std::swap(_M_extract(), __x._M_extract());
-	std::swap(_M_h1(), __x._M_h1());
-	std::swap(_M_h2(), __x._M_h2());
+	std::swap(__ebo_extract_key::_S_get(*this),
+		  __ebo_extract_key::_S_get(__x));
+	std::swap(__ebo_h1::_S_get(*this), __ebo_h1::_S_get(__x));
+	std::swap(__ebo_h2::_S_get(*this), __ebo_h2::_S_get(__x));
       }
 
       const _ExtractKey&
       _M_extract() const { return __ebo_extract_key::_S_cget(*this); }
 
-      _ExtractKey&
-      _M_extract() { return __ebo_extract_key::_S_get(*this); }
-
       const _H1&
       _M_h1() const { return __ebo_h1::_S_cget(*this); }
 
-      _H1&
-      _M_h1() { return __ebo_h1::_S_get(*this); }
-
       const _H2&
       _M_h2() const { return __ebo_h2::_S_cget(*this); }
-
-      _H2&
-      _M_h2() { return __ebo_h2::_S_get(*this); }
     };
 
   /**
@@ -1840,14 +1819,11 @@ namespace __detail
     _M_swap(_Hashtable_base& __x)
     {
       __hash_code_base::_M_swap(__x);
-      std::swap(_M_eq(), __x._M_eq());
+      std::swap(_EqualEBO::_S_get(*this), _EqualEBO::_S_get(__x));
     }
 
     const _Equal&
     _M_eq() const { return _EqualEBO::_S_cget(*this); }
-
-    _Equal&
-    _M_eq() { return _EqualEBO::_S_get(*this); }
   };
 
   /**