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libstdc++: Review unordered_map insert_or_assign/try_emplace (PR 95079)

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Those methods are making a double lookup in case of insertion, they can
perform only one.

	PR libstdc++/95079
	* include/bits/hashtable_policy.h (_Insert_base<>::try_emplace): New.
	* include/bits/unordered_map.h (unordered_map<>::try_emplace): Adapt.
	(unordered_map<>::insert_or_assign): Adapt.
This commit is contained in:
François Dumont 2020-05-24 12:04:38 +02:00
parent c735929a25
commit 7688e5e8c4
2 changed files with 82 additions and 112 deletions
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22
libstdc++-v3/include/bits/hashtable_policy.h
View File

@ -848,6 +848,28 @@ namespace __detail
return __h._M_insert(__hint, __v, __node_gen, __unique_keys());
}
template<typename _KType, typename... _Args>
std::pair<iterator, bool>
try_emplace(const_iterator, _KType&& __k, _Args&&... __args)
{
__hashtable& __h = _M_conjure_hashtable();
auto __code = __h._M_hash_code(__k);
std::size_t __bkt = __h._M_bucket_index(__k, __code);
if (__node_type* __node = __h._M_find_node(__bkt, __k, __code))
return { iterator(__node), false };
typename __hashtable::_Scoped_node __node {
&__h,
std::piecewise_construct,
std::forward_as_tuple(std::forward<_KType>(__k)),
std::forward_as_tuple(std::forward<_Args>(__args)...)
};
auto __it
= __h._M_insert_unique_node(__k, __bkt, __code, __node._M_node);
__node._M_node = nullptr;
return { __it, true };
}
void
insert(initializer_list<value_type> __l)
{ this->insert(__l.begin(), __l.end()); }

172
libstdc++-v3/include/bits/unordered_map.h
View File

@ -466,39 +466,20 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
* Insertion requires amortized constant time.
*/
template <typename... _Args>
pair<iterator, bool>
try_emplace(const key_type& __k, _Args&&... __args)
{
iterator __i = find(__k);
if (__i == end())
{
__i = emplace(std::piecewise_construct,
std::forward_as_tuple(__k),
std::forward_as_tuple(
std::forward<_Args>(__args)...))
.first;
return {__i, true};
}
return {__i, false};
}
pair<iterator, bool>
try_emplace(const key_type& __k, _Args&&... __args)
{
return _M_h.try_emplace(cend(), __k, std::forward<_Args>(__args)...);
}
// move-capable overload
template <typename... _Args>
pair<iterator, bool>
try_emplace(key_type&& __k, _Args&&... __args)
{
iterator __i = find(__k);
if (__i == end())
{
__i = emplace(std::piecewise_construct,
std::forward_as_tuple(std::move(__k)),
std::forward_as_tuple(
std::forward<_Args>(__args)...))
.first;
return {__i, true};
}
return {__i, false};
}
pair<iterator, bool>
try_emplace(key_type&& __k, _Args&&... __args)
{
return _M_h.try_emplace(cend(), std::move(__k),
std::forward<_Args>(__args)...);
}
/**
* @brief Attempts to build and insert a std::pair into the
@ -529,32 +510,22 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
* Insertion requires amortized constant time.
*/
template <typename... _Args>
iterator
try_emplace(const_iterator __hint, const key_type& __k,
_Args&&... __args)
{
iterator __i = find(__k);
if (__i == end())
__i = emplace_hint(__hint, std::piecewise_construct,
std::forward_as_tuple(__k),
std::forward_as_tuple(
std::forward<_Args>(__args)...));
return __i;
}
iterator
try_emplace(const_iterator __hint, const key_type& __k,
_Args&&... __args)
{
return _M_h.try_emplace(__hint, __k,
std::forward<_Args>(__args)...).first;
}
// move-capable overload
template <typename... _Args>
iterator
try_emplace(const_iterator __hint, key_type&& __k, _Args&&... __args)
{
iterator __i = find(__k);
if (__i == end())
__i = emplace_hint(__hint, std::piecewise_construct,
std::forward_as_tuple(std::move(__k)),
std::forward_as_tuple(
std::forward<_Args>(__args)...));
return __i;
}
iterator
try_emplace(const_iterator __hint, key_type&& __k, _Args&&... __args)
{
return _M_h.try_emplace(__hint, std::move(__k),
std::forward<_Args>(__args)...).first;
}
#endif // C++17
//@{
@ -678,39 +649,27 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
* Insertion requires amortized constant time.
*/
template <typename _Obj>
pair<iterator, bool>
insert_or_assign(const key_type& __k, _Obj&& __obj)
{
iterator __i = find(__k);
if (__i == end())
{
__i = emplace(std::piecewise_construct,
std::forward_as_tuple(__k),
std::forward_as_tuple(std::forward<_Obj>(__obj)))
.first;
return {__i, true};
}
(*__i).second = std::forward<_Obj>(__obj);
return {__i, false};
}
pair<iterator, bool>
insert_or_assign(const key_type& __k, _Obj&& __obj)
{
auto __ret = _M_h.try_emplace(cend(), __k,
std::forward<_Obj>(__obj));
if (!__ret.second)
__ret.first->second = std::forward<_Obj>(__obj);
return __ret;
}
// move-capable overload
template <typename _Obj>
pair<iterator, bool>
insert_or_assign(key_type&& __k, _Obj&& __obj)
{
iterator __i = find(__k);
if (__i == end())
{
__i = emplace(std::piecewise_construct,
std::forward_as_tuple(std::move(__k)),
std::forward_as_tuple(std::forward<_Obj>(__obj)))
.first;
return {__i, true};
}
(*__i).second = std::forward<_Obj>(__obj);
return {__i, false};
}
pair<iterator, bool>
insert_or_assign(key_type&& __k, _Obj&& __obj)
{
auto __ret = _M_h.try_emplace(cend(), std::move(__k),
std::forward<_Obj>(__obj));
if (!__ret.second)
__ret.first->second = std::forward<_Obj>(__obj);
return __ret;
}
/**
* @brief Attempts to insert a std::pair into the %unordered_map.
@ -739,38 +698,27 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
* Insertion requires amortized constant time.
*/
template <typename _Obj>
iterator
insert_or_assign(const_iterator __hint, const key_type& __k,
_Obj&& __obj)
{
iterator __i = find(__k);
if (__i == end())
{
return emplace_hint(__hint, std::piecewise_construct,
std::forward_as_tuple(__k),
std::forward_as_tuple(
std::forward<_Obj>(__obj)));
}
(*__i).second = std::forward<_Obj>(__obj);
return __i;
}
iterator
insert_or_assign(const_iterator __hint, const key_type& __k,
_Obj&& __obj)
{
auto __ret = _M_h.try_emplace(__hint, __k, std::forward<_Obj>(__obj));
if (!__ret.second)
__ret.first->second = std::forward<_Obj>(__obj);
return __ret.first;
}
// move-capable overload
template <typename _Obj>
iterator
insert_or_assign(const_iterator __hint, key_type&& __k, _Obj&& __obj)
{
iterator __i = find(__k);
if (__i == end())
{
return emplace_hint(__hint, std::piecewise_construct,
std::forward_as_tuple(std::move(__k)),
std::forward_as_tuple(
std::forward<_Obj>(__obj)));
}
(*__i).second = std::forward<_Obj>(__obj);
return __i;
}
iterator
insert_or_assign(const_iterator __hint, key_type&& __k, _Obj&& __obj)
{
auto __ret = _M_h.try_emplace(__hint, std::move(__k),
std::forward<_Obj>(__obj));
if (!__ret.second)
__ret.first->second = std::forward<_Obj>(__obj);
return __ret.first;
}
#endif
//@{