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From: "fdumont at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug libstdc++/96088] Range insertion into unordered_map is less effective than a loop with insertion Date: Tue, 25 May 2021 19:27:47 +0000 [thread overview] Message-ID: <bug-96088-4-CzGYqKxzIx@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-96088-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96088 François Dumont <fdumont at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Target Milestone|--- |12.0 Resolution|--- |FIXED Status|ASSIGNED |RESOLVED --- Comment #6 from François Dumont <fdumont at gcc dot gnu.org> --- Fix with this commit: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=2c43f5ec9db163696de8691eb529df06c4999bcc libstdc++: Limit allocation on iterator insertion in Hashtable [PR 96088] When inserting into unordered_multiset or unordered_multimap first instantiate the node to store and compute the hash code from it to avoid a potential intermediate key_type instantiation. When inserting into unordered_set or unordered_map check if invoking the hash functor with container key_type is noexcept and invoking the same hash functor with key part of the iterator value_type can throw. In this case create a temporary key_type instance at Hashtable level and use it to compute the hash code. This temporary instance is moved to the final storage location if needed. libstdc++-v3/ChangeLog: PR libstdc++/96088 * include/bits/hashtable_policy.h (_Select2nd): New. (_NodeBuilder<>): New. (_ReuseOrAllocNode<>::operator()): Use variadic template args. (_AllocNode<>::operator()): Likewise. * include/bits/hashtable.h (_Hashtable<>::__node_builder_t): New. (_Hashtable<>::_M_insert_unique<>(_Kt&&, _Arg&&, const _NodeGenerator&)): New. (_Hashtable<>::_S_forward_key): New. (_Hashtable<>::_M_insert): Use latter. (_Hashtable<>::_M_insert(const_iterator, _Arg&&, const _NodeGenerator&, false_type)): Instantiate node first, compute hash code second. * testsuite/23_containers/unordered_map/96088.cc: New test. * testsuite/23_containers/unordered_multimap/96088.cc: New test. * testsuite/23_containers/unordered_multiset/96088.cc: New test. * testsuite/23_containers/unordered_set/96088.cc: New test. * testsuite/util/replacement_memory_operators.h (counter::_M_increment): New. (counter::_M_decrement): New. (counter::reset()): New.
next prev parent reply other threads:[~2021-05-25 19:27 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-07-06 18:37 [Bug libstdc++/96088] New: " antoshkka at gmail dot com 2020-07-09 6:23 ` [Bug libstdc++/96088] " fdumont at gcc dot gnu.org 2020-07-09 8:31 ` redi at gcc dot gnu.org 2020-07-09 10:50 ` glisse at gcc dot gnu.org 2020-07-09 14:46 ` redi at gcc dot gnu.org 2020-08-04 17:36 ` fdumont at gcc dot gnu.org 2021-05-25 19:27 ` fdumont at gcc dot gnu.org [this message] 2021-06-02 12:33 ` cvs-commit at gcc dot gnu.org
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