re PR libstdc++/54075 ([4.7.1] unordered_map insert still slower than 4.6.2)

2012-11-08  François Dumont  <fdumont@gcc.gnu.org>

	PR libstdc++/54075
	* include/bits/hashtable.h (_Hashtable<>::rehash): Reset hash
	policy state if no rehash.
	* testsuite/23_containers/unordered_set/modifiers/reserve.cc
	(test02): New.

From-SVN: r193339

libstdc++-v3/ChangeLog

+2012-11-08  François Dumont  <fdumont@gcc.gnu.org>
+
+	PR libstdc++/54075
+	* include/bits/hashtable.h (_Hashtable<>::rehash): Reset hash
+	policy state if no rehash.
+	* testsuite/23_containers/unordered_set/modifiers/reserve.cc
+	(test02): New.
+
 2012-11-08  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* testsuite/23_containers/unordered_multimap/insert/55028-debug.cc:

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

@@ -1654,6 +1654,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  // level.
 	  _M_rehash_policy._M_prev_resize = 0;
 	}
+      else
+	// No rehash, restore previous state to keep a consistent state.
+	_M_rehash_policy._M_reset(__saved_state);
     }
 
   template<typename _Key, typename _Value,

libstdc++-v3/testsuite/23_containers/unordered_set/modifiers/reserve.cc

@@ -40,8 +40,28 @@ void test01()
     }
 }
 
+void test02()
+{
+  const int N = 1000;
+
+  typedef std::unordered_set<int> Set;
+  Set s;
+  s.reserve(N);
+  s.reserve(N);
+
+  std::size_t bkts = s.bucket_count();
+  for (int i = 0; i != N; ++i)
+    {
+      s.insert(i);
+      // As long as we insert less than the reserved number of elements we
+      // shouldn't experiment any rehash.
+      VERIFY( s.bucket_count() == bkts );
+    }
+}
+
 int main()
 {
   test01();
+  test02();
   return 0;
 }