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* [Bug c++/102015] New: [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break)
@ 2021-08-22 17:36 kamkaz at windowslive dot com
2021-08-22 19:17 ` [Bug libstdc++/102015] " pinskia at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: kamkaz at windowslive dot com @ 2021-08-22 17:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102015
Bug ID: 102015
Summary: [missed optimization] Small memory overhead in
_Rb_tree_impl (fix would require ABI break)
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: kamkaz at windowslive dot com
Target Milestone: ---
Current definition of _Rb_tree_key_compare causes size overhead for all
std::(multi)set/map-s:
template<typename _Key_compare>
struct _Rb_tree_key_compare
{
_Key_compare _M_key_compare;
...
};
If it were possible to change the ABI in the future, I think it can be improved
by empty-base-optimization for comparators that are not final classes - or by
adding [[no_unique_address]] to _M_key_compare.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug libstdc++/102015] [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break) 2021-08-22 17:36 [Bug c++/102015] New: [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break) kamkaz at windowslive dot com @ 2021-08-22 19:17 ` pinskia at gcc dot gnu.org 2021-08-22 21:08 ` kamkaz at windowslive dot com ` (3 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-08-22 19:17 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102015 --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- https://stackoverflow.com/questions/66573773/is-there-a-reason-for-8-bytes-of-size-overhead-in-libstdc-stdmultiset-map ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug libstdc++/102015] [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break) 2021-08-22 17:36 [Bug c++/102015] New: [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break) kamkaz at windowslive dot com 2021-08-22 19:17 ` [Bug libstdc++/102015] " pinskia at gcc dot gnu.org @ 2021-08-22 21:08 ` kamkaz at windowslive dot com 2021-08-23 9:45 ` redi at gcc dot gnu.org ` (2 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: kamkaz at windowslive dot com @ 2021-08-22 21:08 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102015 --- Comment #2 from Kamil Kaznowski <kamkaz at windowslive dot com> --- (In reply to Andrew Pinski from comment #1) > https://stackoverflow.com/questions/66573773/is-there-a-reason-for-8-bytes- > of-size-overhead-in-libstdc-stdmultiset-map This is my post, I forgot to post a bug that day. There is also a mistake by me in the comments - MSVC _Compressed_pair works by template specialization, not SFINAE. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug libstdc++/102015] [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break) 2021-08-22 17:36 [Bug c++/102015] New: [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break) kamkaz at windowslive dot com 2021-08-22 19:17 ` [Bug libstdc++/102015] " pinskia at gcc dot gnu.org 2021-08-22 21:08 ` kamkaz at windowslive dot com @ 2021-08-23 9:45 ` redi at gcc dot gnu.org 2021-08-31 18:27 ` redi at gcc dot gnu.org 2021-08-31 18:28 ` redi at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: redi at gcc dot gnu.org @ 2021-08-23 9:45 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102015 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Severity|normal |enhancement Last reconfirmed| |2021-08-23 Ever confirmed|0 |1 Status|UNCONFIRMED |NEW --- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- There's no way to use [[no_unique_address]] in C++98 mode, and making it use EBO would be a pain. Confirmed as a possible future enhancement. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug libstdc++/102015] [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break) 2021-08-22 17:36 [Bug c++/102015] New: [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break) kamkaz at windowslive dot com ` (2 preceding siblings ...) 2021-08-23 9:45 ` redi at gcc dot gnu.org @ 2021-08-31 18:27 ` redi at gcc dot gnu.org 2021-08-31 18:28 ` redi at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: redi at gcc dot gnu.org @ 2021-08-31 18:27 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102015 --- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- In https://gcc.gnu.org/pipermail/libstdc++/2021-August/053108.html I proposed dropping C++98 support for the gnu-versioned-namespace, which would allow us to fix this by using [[__no_unique_address__]]. N.B. I reported this same issue as PR 77402 five years ago. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug libstdc++/102015] [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break) 2021-08-22 17:36 [Bug c++/102015] New: [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break) kamkaz at windowslive dot com ` (3 preceding siblings ...) 2021-08-31 18:27 ` redi at gcc dot gnu.org @ 2021-08-31 18:28 ` redi at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: redi at gcc dot gnu.org @ 2021-08-31 18:28 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102015 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |redi at gcc dot gnu.org --- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- *** Bug 77402 has been marked as a duplicate of this bug. *** ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-08-31 18:28 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-08-22 17:36 [Bug c++/102015] New: [missed optimization] Small memory overhead in _Rb_tree_impl (fix would require ABI break) kamkaz at windowslive dot com 2021-08-22 19:17 ` [Bug libstdc++/102015] " pinskia at gcc dot gnu.org 2021-08-22 21:08 ` kamkaz at windowslive dot com 2021-08-23 9:45 ` redi at gcc dot gnu.org 2021-08-31 18:27 ` redi at gcc dot gnu.org 2021-08-31 18:28 ` redi at gcc dot gnu.org
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