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optimize std::vector move assignment

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2018-07-26  Marc Glisse  <marc.glisse@inria.fr>

	* include/bits/stl_vector.h (_Vector_impl_data::_M_copy_data): New.
	(_Vector_impl_data::_M_swap_data): Use _M_copy_data.
	(vector::_M_move_assign): Reorder the swaps.

From-SVN: r262998
This commit is contained in:
Marc Glisse 2018-07-26 14:01:14 +02:00 • committed by Marc Glisse
parent 88a4654d03
commit e98edc20cd
2 changed files with 21 additions and 4 deletions
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6
libstdc++-v3/ChangeLog
View file

@ -1,3 +1,9 @@
2018-07-26 Marc Glisse <marc.glisse@inria.fr>
* include/bits/stl_vector.h (_Vector_impl_data::_M_copy_data): New.
(_Vector_impl_data::_M_swap_data): Use _M_copy_data.
(vector::_M_move_assign): Reorder the swaps.
2018-07-26 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/86676

19
libstdc++-v3/include/bits/stl_vector.h
View file

@ -102,12 +102,23 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
{ __x._M_start = __x._M_finish = __x._M_end_of_storage = pointer(); }
#endif
void
_M_copy_data(_Vector_impl_data const& __x) _GLIBCXX_NOEXCEPT
{
_M_start = __x._M_start;
_M_finish = __x._M_finish;
_M_end_of_storage = __x._M_end_of_storage;
}
void
_M_swap_data(_Vector_impl_data& __x) _GLIBCXX_NOEXCEPT
{
std::swap(_M_start, __x._M_start);
std::swap(_M_finish, __x._M_finish);
std::swap(_M_end_of_storage, __x._M_end_of_storage);
// Do not use std::swap(_M_start, __x._M_start), etc as it loses
// information used by TBAA.
_Vector_impl_data __tmp;
__tmp._M_copy_data(*this);
_M_copy_data(__x);
__x._M_copy_data(__tmp);
}
};
@ -1731,8 +1742,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_move_assign(vector&& __x, true_type) noexcept
{
vector __tmp(get_allocator());
this->_M_impl._M_swap_data(__tmp._M_impl);
this->_M_impl._M_swap_data(__x._M_impl);
__tmp._M_impl._M_swap_data(__x._M_impl);
std::__alloc_on_move(_M_get_Tp_allocator(), __x._M_get_Tp_allocator());
}