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PR libstdc++/86127 avoid unnecessary allocator conversions 

There is no need to use an allocator of the correct value_type when
calling allocator_traits::construct and allocator_traits::destroy. The
existing node allocator can be used, instead of constructing a new
allocator object every time.

There's also no benefit to using __gnu_cxx::__alloc_traits instead of
std::allocator_traits to get the pointer and const_pointer types.
std::forward_list is only available for C++11 and later, when
std::allocator_traits is available too.

	PR libstdc++/86127
	* include/bits/forward_list.h (_Fwd_list_base::_Tp_alloc_type): Remove
	unused typedef.
	(_Fwd_list_base::_Node_alloc_traits): Use allocator_traits instead of
	__gnu_cxx::__alloc_traits.
	(_Fwd_list_base::_M_create_node, _Fwd_list_base::_M_erase_after):
	Use node allocator to create and destroy elements.
	(forward_list::_Tp_alloc_type): Remove unused typedef.
	(forward_list::_Alloc_traits): Use allocator_traits instead of
	__gnu_cxx::__alloc_traits.

From-SVN: r261554
This commit is contained in:
Jonathan Wakely 2018-06-13 16:14:48 +01:00 committed by Jonathan Wakely
parent 7b76867b21
commit 1cc56f079e
3 changed files with 21 additions and 11 deletions
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13
libstdc++-v3/ChangeLog
View File

@ -1,3 +1,16 @@
2018-06-13 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/86127
* include/bits/forward_list.h (_Fwd_list_base::_Tp_alloc_type): Remove
unused typedef.
(_Fwd_list_base::_Node_alloc_traits): Use allocator_traits instead of
__gnu_cxx::__alloc_traits.
(_Fwd_list_base::_M_create_node, _Fwd_list_base::_M_erase_after):
Use node allocator to create and destroy elements.
(forward_list::_Tp_alloc_type): Remove unused typedef.
(forward_list::_Alloc_traits): Use allocator_traits instead of
__gnu_cxx::__alloc_traits.
2018-06-13 François Dumont <fdumont@gcc.gnu.org>
* include/debug/debug.h (__glibcxx_requires_can_increment_range): New.

11
libstdc++-v3/include/bits/forward_list.h
View File

@ -289,7 +289,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
struct _Fwd_list_base
{
protected:
typedef __alloc_rebind<_Alloc, _Tp> _Tp_alloc_type;
typedef __alloc_rebind<_Alloc, _Fwd_list_node<_Tp>> _Node_alloc_type;
typedef __gnu_cxx::__alloc_traits<_Node_alloc_type> _Node_alloc_traits;
@ -363,11 +362,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_Node* __node = this->_M_get_node();
__try
{
_Tp_alloc_type __a(_M_get_Node_allocator());
typedef allocator_traits<_Tp_alloc_type> _Alloc_traits;
::new ((void*)__node) _Node;
_Alloc_traits::construct(__a, __node->_M_valptr(),
std::forward<_Args>(__args)...);
_Node_alloc_traits::construct(_M_get_Node_allocator(),
__node->_M_valptr(),
std::forward<_Args>(__args)...);
}
__catch(...)
{
@ -437,10 +435,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
typedef _Fwd_list_base<_Tp, _Alloc> _Base;
typedef _Fwd_list_node<_Tp> _Node;
typedef _Fwd_list_node_base _Node_base;
typedef typename _Base::_Tp_alloc_type _Tp_alloc_type;
typedef typename _Base::_Node_alloc_type _Node_alloc_type;
typedef typename _Base::_Node_alloc_traits _Node_alloc_traits;
typedef __gnu_cxx::__alloc_traits<_Tp_alloc_type> _Alloc_traits;
typedef allocator_traits<__alloc_rebind<_Alloc, _Tp>> _Alloc_traits;
public:
// types:

8
libstdc++-v3/include/bits/forward_list.tcc
View File

@ -65,8 +65,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
{
_Node* __curr = static_cast<_Node*>(__pos->_M_next);
__pos->_M_next = __curr->_M_next;
_Tp_alloc_type __a(_M_get_Node_allocator());
allocator_traits<_Tp_alloc_type>::destroy(__a, __curr->_M_valptr());
_Node_alloc_traits::destroy(_M_get_Node_allocator(),
__curr->_M_valptr());
__curr->~_Node();
_M_put_node(__curr);
return __pos->_M_next;
@ -83,8 +83,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
{
_Node* __temp = __curr;
__curr = static_cast<_Node*>(__curr->_M_next);
_Tp_alloc_type __a(_M_get_Node_allocator());
allocator_traits<_Tp_alloc_type>::destroy(__a, __temp->_M_valptr());
_Node_alloc_traits::destroy(_M_get_Node_allocator(),
__temp->_M_valptr());
__temp->~_Node();
_M_put_node(__temp);
}