Optimize inserting value_type into std::vector

	* include/bits/stl_vector.h (vector::_S_insert_aux_assign): Define
	new overloaded functions.
	* include/bits/vector.tcc (vector::_M_insert_aux): Use new functions
	to avoid creating a redundant temporary.
	* testsuite/23_containers/vector/modifiers/insert_vs_emplace.cc: New
	test.

From-SVN: r237526

libstdc++-v3/ChangeLog

+2016-06-16  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/bits/stl_vector.h (vector::_S_insert_aux_assign): Define
+	new overloaded functions.
+	* include/bits/vector.tcc (vector::_M_insert_aux): Use new functions
+	to avoid creating a redundant temporary.
+	* testsuite/23_containers/vector/modifiers/insert_vs_emplace.cc: New
+	test.
+
 2016-06-15  François Dumont  <fdumont@gcc.gnu.org>
 
 	* include/bits/stl_deque.h

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

@@ -1412,6 +1412,15 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       _M_insert_aux(iterator __position, const value_type& __x);
 #else
       template<typename... _Args>
+	static void
+	_S_insert_aux_assign(iterator __pos, _Args&&... __args)
+	{ *__pos =  _Tp(std::forward<_Args>(__args)...); }
+
+      static void
+      _S_insert_aux_assign(iterator __pos, _Tp&& __arg)
+      { *__pos = std::move(__arg); }
+
+      template<typename... _Args>
 	void
 	_M_insert_aux(iterator __position, _Args&&... __args);
 

libstdc++-v3/include/bits/vector.tcc

@@ -343,7 +343,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 #if __cplusplus < 201103L
 	  *__position = __x_copy;
 #else
-	  *__position = _Tp(std::forward<_Args>(__args)...);
+	  _S_insert_aux_assign(__position, std::forward<_Args>(__args)...);
 #endif
 	}
       else