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Optimization of std::deque implementation
- From: François Dumont <frs dot dumont at gmail dot com>
- To: "libstdc++ at gcc dot gnu dot org" <libstdc++ at gcc dot gnu dot org>, gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 6 Nov 2018 10:42:39 +0100
- Subject: Optimization of std::deque implementation
Here is a patch similar to what has been done to other containers like
std::vector.
It optimizes the swap operation, the allocator extended move constructor
and some other methods where I just bypass intermediate calls.
I reproduced the noexcept qualification on _Deque_impl_data/_Deque_impl
even if they are not necessary as long as the std:deque always allocate
on instantiation.
I also removed some _M_map checks as, once again, it can't be null for
the moment. I just kept the one in the destructor as I'd like to commit
a patch after this one to avoid allocations on move which will make this
check necessary.
Tested under Linux x86_64 Default and C++98 modes, w/o version namespace.
Still time to commit ?
François
diff --git a/libstdc++-v3/include/bits/stl_deque.h b/libstdc++-v3/include/bits/stl_deque.h
index 8e4defbcf26..c49b6852324 100644
--- a/libstdc++-v3/include/bits/stl_deque.h
+++ b/libstdc++-v3/include/bits/stl_deque.h
@@ -398,7 +398,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_Map_alloc_type;
typedef __gnu_cxx::__alloc_traits<_Map_alloc_type> _Map_alloc_traits;
- public:
typedef _Alloc allocator_type;
allocator_type
@@ -409,11 +408,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
typedef _Deque_iterator<_Tp, const _Tp&, _Ptr_const> const_iterator;
_Deque_base()
- : _M_impl()
{ _M_initialize_map(0); }
_Deque_base(size_t __num_elements)
- : _M_impl()
{ _M_initialize_map(__num_elements); }
_Deque_base(const allocator_type& __a, size_t __num_elements)
@@ -425,6 +422,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
{ /* Caller must initialize map. */ }
#if __cplusplus >= 201103L
+ private:
_Deque_base(_Deque_base&& __x, false_type)
: _M_impl(__x._M_move_impl())
{ }
@@ -433,84 +431,100 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
: _M_impl(std::move(__x._M_get_Tp_allocator()))
{
_M_initialize_map(0);
- if (__x._M_impl._M_map)
this->_M_impl._M_swap_data(__x._M_impl);
}
+ protected:
_Deque_base(_Deque_base&& __x)
: _Deque_base(std::move(__x), typename _Alloc_traits::is_always_equal{})
{ }
+ _Deque_base(_Deque_base&& __x, const allocator_type& __a)
+ : _M_impl(std::move(__x._M_impl), _Tp_alloc_type(__a))
+ { __x._M_initialize_map(0); }
+
_Deque_base(_Deque_base&& __x, const allocator_type& __a, size_t __n)
: _M_impl(__a)
{
if (__x.get_allocator() == __a)
- {
- if (__x._M_impl._M_map)
{
_M_initialize_map(0);
this->_M_impl._M_swap_data(__x._M_impl);
}
- }
else
- {
_M_initialize_map(__n);
}
- }
#endif
~_Deque_base() _GLIBCXX_NOEXCEPT;
- protected:
typedef typename iterator::_Map_pointer _Map_pointer;
- //This struct encapsulates the implementation of the std::deque
- //standard container and at the same time makes use of the EBO
- //for empty allocators.
- struct _Deque_impl
- : public _Tp_alloc_type
+ struct _Deque_impl_data
{
_Map_pointer _M_map;
size_t _M_map_size;
iterator _M_start;
iterator _M_finish;
- _Deque_impl()
- : _Tp_alloc_type(), _M_map(), _M_map_size(0),
- _M_start(), _M_finish()
+ _Deque_impl_data() _GLIBCXX_NOEXCEPT
+ : _M_map(), _M_map_size(), _M_start(), _M_finish()
+ { }
+
+#if __cplusplus >= 201103L
+ _Deque_impl_data(const _Deque_impl_data&) = default;
+ _Deque_impl_data&
+ operator=(const _Deque_impl_data&) = default;
+
+ _Deque_impl_data(_Deque_impl_data&& __x) noexcept
+ : _Deque_impl_data(__x)
+ { __x = _Deque_impl_data(); }
+#endif
+
+ void
+ _M_swap_data(_Deque_impl_data& __x) _GLIBCXX_NOEXCEPT
+ {
+ // Do not use std::swap(_M_start, __x._M_start), etc as it loses
+ // information used by TBAA.
+ std::swap(*this, __x);
+ }
+ };
+
+ // This struct encapsulates the implementation of the std::deque
+ // standard container and at the same time makes use of the EBO
+ // for empty allocators.
+ struct _Deque_impl
+ : public _Tp_alloc_type, public _Deque_impl_data
+ {
+ _Deque_impl() _GLIBCXX_NOEXCEPT_IF(
+ is_nothrow_default_constructible<_Tp_alloc_type>::value)
+ : _Tp_alloc_type()
{ }
_Deque_impl(const _Tp_alloc_type& __a) _GLIBCXX_NOEXCEPT
- : _Tp_alloc_type(__a), _M_map(), _M_map_size(0),
- _M_start(), _M_finish()
+ : _Tp_alloc_type(__a)
{ }
#if __cplusplus >= 201103L
_Deque_impl(_Deque_impl&&) = default;
_Deque_impl(_Tp_alloc_type&& __a) noexcept
- : _Tp_alloc_type(std::move(__a)), _M_map(), _M_map_size(0),
- _M_start(), _M_finish()
+ : _Tp_alloc_type(std::move(__a))
{ }
-#endif
- void _M_swap_data(_Deque_impl& __x) _GLIBCXX_NOEXCEPT
- {
- using std::swap;
- swap(this->_M_start, __x._M_start);
- swap(this->_M_finish, __x._M_finish);
- swap(this->_M_map, __x._M_map);
- swap(this->_M_map_size, __x._M_map_size);
- }
+ _Deque_impl(_Deque_impl&& __d, _Tp_alloc_type&& __a)
+ : _Tp_alloc_type(std::move(__a)), _Deque_impl_data(std::move(__d))
+ { }
+#endif
};
_Tp_alloc_type&
_M_get_Tp_allocator() _GLIBCXX_NOEXCEPT
- { return *static_cast<_Tp_alloc_type*>(&this->_M_impl); }
+ { return this->_M_impl; }
const _Tp_alloc_type&
_M_get_Tp_allocator() const _GLIBCXX_NOEXCEPT
- { return *static_cast<const _Tp_alloc_type*>(&this->_M_impl); }
+ { return this->_M_impl; }
_Map_alloc_type
_M_get_map_allocator() const _GLIBCXX_NOEXCEPT
@@ -544,7 +558,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_Map_alloc_traits::deallocate(__map_alloc, __p, __n);
}
- protected:
void _M_initialize_map(size_t);
void _M_create_nodes(_Map_pointer __nstart, _Map_pointer __nfinish);
void _M_destroy_nodes(_Map_pointer __nstart,
@@ -558,9 +571,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_Deque_impl
_M_move_impl()
{
- if (!_M_impl._M_map)
- return std::move(_M_impl);
-
// Create a copy of the current allocator.
_Tp_alloc_type __alloc{_M_get_Tp_allocator()};
// Put that copy in a moved-from state.
@@ -788,7 +798,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
typedef ptrdiff_t difference_type;
typedef _Alloc allocator_type;
- protected:
+ private:
static size_t _S_buffer_size() _GLIBCXX_NOEXCEPT
{ return __deque_buf_size(sizeof(_Tp)); }
@@ -815,7 +825,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
/**
* @brief Creates a %deque with no elements.
*/
- deque() : _Base() { }
+#if __cplusplus >= 201103L
+ deque() = default;
+#else
+ deque() { }
+#endif
/**
* @brief Creates a %deque with no elements.
@@ -884,13 +898,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
#if __cplusplus >= 201103L
/**
* @brief %Deque move constructor.
- * @param __x A %deque of identical element and allocator types.
*
- * The newly-created %deque contains the exact contents of @a __x.
- * The contents of @a __x are a valid, but unspecified %deque.
+ * The newly-created %deque contains the exact contents of the
+ * moved instance.
+ * The contents of the moved instance are a valid, but unspecified
+ * %deque.
*/
- deque(deque&& __x)
- : _Base(std::move(__x)) { }
+ deque(deque&&) = default;
/// Copy constructor with alternative allocator
deque(const deque& __x, const allocator_type& __a)
@@ -901,9 +915,18 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
/// Move constructor with alternative allocator
deque(deque&& __x, const allocator_type& __a)
+ : deque(std::move(__x), __a, typename _Alloc_traits::is_always_equal{})
+ { }
+
+ private:
+ deque(deque&& __x, const allocator_type& __a, true_type)
+ : _Base(std::move(__x), __a)
+ { }
+
+ deque(deque&& __x, const allocator_type& __a, false_type)
: _Base(std::move(__x), __a, __x.size())
{
- if (__x.get_allocator() != __a)
+ if (__x.get_allocator() != __a && !__x.empty())
{
std::__uninitialized_move_a(__x.begin(), __x.end(),
this->_M_impl._M_start,
@@ -912,6 +935,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
}
}
+ public:
/**
* @brief Builds a %deque from an initializer list.
* @param __l An initializer_list.
@@ -953,7 +977,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
deque(_InputIterator __first, _InputIterator __last,
const allocator_type& __a = allocator_type())
: _Base(__a)
- { _M_initialize_dispatch(__first, __last, __false_type()); }
+ {
+ _M_range_initialize(__first, __last,
+ std::__iterator_category(__first));
+ }
#else
template<typename _InputIterator>
deque(_InputIterator __first, _InputIterator __last,
@@ -1054,7 +1081,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
typename = std::_RequireInputIter<_InputIterator>>
void
assign(_InputIterator __first, _InputIterator __last)
- { _M_assign_dispatch(__first, __last, __false_type()); }
+ { _M_assign_aux(__first, __last, std::__iterator_category(__first)); }
#else
template<typename _InputIterator>
void
@@ -1240,14 +1267,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
*/
void
resize(size_type __new_size, const value_type& __x)
- {
- const size_type __len = size();
- if (__new_size > __len)
- _M_fill_insert(this->_M_impl._M_finish, __new_size - __len, __x);
- else if (__new_size < __len)
- _M_erase_at_end(this->_M_impl._M_start
- + difference_type(__new_size));
- }
#else
/**
* @brief Resizes the %deque to the specified number of elements.
@@ -1262,6 +1281,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
*/
void
resize(size_type __new_size, value_type __x = value_type())
+#endif
{
const size_type __len = size();
if (__new_size > __len)
@@ -1270,7 +1290,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_erase_at_end(this->_M_impl._M_start
+ difference_type(__new_size));
}
-#endif
#if __cplusplus >= 201103L
/** A non-binding request to reduce memory use. */
@@ -1599,6 +1618,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
* @brief Inserts an initializer list into the %deque.
* @param __p An iterator into the %deque.
* @param __l An initializer_list.
+ * @return An iterator that points to the inserted data.
*
* This function will insert copies of the data in the
* initializer_list @a __l into the %deque before the location
@@ -1612,9 +1632,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
std::random_access_iterator_tag());
return begin() + __offset;
}
-#endif
-#if __cplusplus >= 201103L
/**
* @brief Inserts a number of copies of given data into the %deque.
* @param __position A const_iterator into the %deque.
@@ -1666,8 +1684,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_InputIterator __last)
{
difference_type __offset = __position - cbegin();
- _M_insert_dispatch(__position._M_const_cast(),
- __first, __last, __false_type());
+ _M_range_insert_aux(__position._M_const_cast(), __first, __last,
+ std::__iterator_category(__first));
return begin() + __offset;
}
#else
@@ -1773,6 +1791,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
protected:
// Internal constructor functions follow.
+#if __cplusplus < 201103L || !_GLIBCXX_INLINE_VERSION
// called by the range constructor to implement [23.1.1]/9
// _GLIBCXX_RESOLVE_LIB_DEFECTS
@@ -1786,6 +1805,17 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_fill_initialize(__x);
}
+ // called by the range constructor to implement [23.1.1]/9
+ template<typename _InputIterator>
+ void
+ _M_initialize_dispatch(_InputIterator __first, _InputIterator __last,
+ __false_type)
+ {
+ _M_range_initialize(__first, __last,
+ std::__iterator_category(__first));
+ }
+#endif
+
static size_t
_S_check_init_len(size_t __n, const allocator_type& __a)
{
@@ -1803,16 +1833,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
return (std::min)(__diffmax, __allocmax);
}
- // called by the range constructor to implement [23.1.1]/9
- template<typename _InputIterator>
- void
- _M_initialize_dispatch(_InputIterator __first, _InputIterator __last,
- __false_type)
- {
- _M_range_initialize(__first, __last,
- std::__iterator_category(__first));
- }
-
// called by the second initialize_dispatch above
//@{
/**
@@ -1859,6 +1879,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
// Internal assign functions follow. The *_aux functions do the actual
// assignment work for the range versions.
+#if __cplusplus < 201103L || !_GLIBCXX_INLINE_VERSION
// called by the range assign to implement [23.1.1]/9
// _GLIBCXX_RESOLVE_LIB_DEFECTS
@@ -1874,6 +1895,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_assign_dispatch(_InputIterator __first, _InputIterator __last,
__false_type)
{ _M_assign_aux(__first, __last, std::__iterator_category(__first)); }
+#endif
// called by the second assign_dispatch above
template<typename _InputIterator>
@@ -1939,6 +1961,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
// Internal insert functions follow. The *_aux functions do the actual
// insertion work when all shortcuts fail.
+#if __cplusplus < 201103L || !_GLIBCXX_INLINE_VERSION
// called by the range insert to implement [23.1.1]/9
// _GLIBCXX_RESOLVE_LIB_DEFECTS
@@ -1959,6 +1982,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_range_insert_aux(__pos, __first, __last,
std::__iterator_category(__first));
}
+#endif
// called by the second insert_dispatch above
template<typename _InputIterator>
diff --git a/libstdc++-v3/testsuite/23_containers/deque/allocator/default_init.cc b/libstdc++-v3/testsuite/23_containers/deque/allocator/default_init.cc
new file mode 100644
index 00000000000..5cb58865faa
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/deque/allocator/default_init.cc
@@ -0,0 +1,67 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run { target c++11 } }
+// { dg-options "-O0" }
+// { dg-xfail-run-if "PR c++/65816" { *-*-* } }
+
+#include <deque>
+#include <testsuite_hooks.h>
+#include <testsuite_allocator.h>
+
+#include <ext/aligned_buffer.h>
+
+using T = int;
+
+using __gnu_test::default_init_allocator;
+
+void test01()
+{
+ typedef default_init_allocator<T> alloc_type;
+ typedef std::deque<T, alloc_type> test_type;
+
+ __gnu_cxx::__aligned_buffer<test_type> buf;
+ __builtin_memset(buf._M_addr(), ~0, sizeof(test_type));
+
+ test_type *tmp = ::new(buf._M_addr()) test_type;
+
+ VERIFY( tmp->get_allocator().state == 0 );
+
+ tmp->~test_type();
+}
+
+void test02()
+{
+ typedef default_init_allocator<T> alloc_type;
+ typedef std::deque<T, alloc_type> test_type;
+
+ __gnu_cxx::__aligned_buffer<test_type> buf;
+ __builtin_memset(buf._M_addr(), ~0, sizeof(test_type));
+
+ test_type *tmp = ::new(buf._M_addr()) test_type();
+
+ VERIFY( tmp->get_allocator().state == 0 );
+
+ tmp->~test_type();
+}
+
+int main()
+{
+ test01();
+ test02();
+ return 0;
+}