public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
* [Bug c++/66364] New: poor optimization of packed structs containing bitfields
@ 2015-06-01 15:35 rogero at howzatt dot demon.co.uk
2020-05-11 5:32 ` [Bug middle-end/66364] " egallager at gcc dot gnu.org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: rogero at howzatt dot demon.co.uk @ 2015-06-01 15:35 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66364
Bug ID: 66364
Summary: poor optimization of packed structs containing
bitfields
Product: gcc
Version: 5.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: rogero at howzatt dot demon.co.uk
Target Milestone: ---
Target: x86_64-redhat-linux
Created attachment 35667
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35667&action=edit
Simple program demonstrating the issue
Code accessing bitfields in packed structures seem to load the value a byte at
a time and build the value up using shifts and ors even with -O3.
On x64 it could load the value using a single mov instruction as it does when
the struct is not packed or when the field is not a bitfield.
^ permalink raw reply [flat|nested] 7+ messages in thread* [Bug middle-end/66364] poor optimization of packed structs containing bitfields 2015-06-01 15:35 [Bug c++/66364] New: poor optimization of packed structs containing bitfields rogero at howzatt dot demon.co.uk @ 2020-05-11 5:32 ` egallager at gcc dot gnu.org 2021-08-11 0:31 ` pinskia at gcc dot gnu.org ` (4 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: egallager at gcc dot gnu.org @ 2020-05-11 5:32 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66364 Eric Gallager <egallager at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |egallager at gcc dot gnu.org --- Comment #1 from Eric Gallager <egallager at gcc dot gnu.org> --- there are some other bugs open that are similar to this; I am tired though so I'll pull their numbers back up later... ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug middle-end/66364] poor optimization of packed structs containing bitfields 2015-06-01 15:35 [Bug c++/66364] New: poor optimization of packed structs containing bitfields rogero at howzatt dot demon.co.uk 2020-05-11 5:32 ` [Bug middle-end/66364] " egallager at gcc dot gnu.org @ 2021-08-11 0:31 ` pinskia at gcc dot gnu.org 2023-02-25 6:44 ` [Bug tree-optimization/66364] " pinskia at gcc dot gnu.org ` (3 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-08-11 0:31 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66364 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |ASSIGNED Severity|normal |enhancement Ever confirmed|0 |1 Last reconfirmed| |2021-08-11 Assignee|unassigned at gcc dot gnu.org |pinskia at gcc dot gnu.org --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Mine for GCC 13. ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/66364] poor optimization of packed structs containing bitfields 2015-06-01 15:35 [Bug c++/66364] New: poor optimization of packed structs containing bitfields rogero at howzatt dot demon.co.uk 2020-05-11 5:32 ` [Bug middle-end/66364] " egallager at gcc dot gnu.org 2021-08-11 0:31 ` pinskia at gcc dot gnu.org @ 2023-02-25 6:44 ` pinskia at gcc dot gnu.org 2023-02-26 1:34 ` pinskia at gcc dot gnu.org ` (2 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-02-25 6:44 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66364 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |DUPLICATE Status|ASSIGNED |RESOLVED --- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Dup of bug 55658. *** This bug has been marked as a duplicate of bug 55658 *** ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/66364] poor optimization of packed structs containing bitfields 2015-06-01 15:35 [Bug c++/66364] New: poor optimization of packed structs containing bitfields rogero at howzatt dot demon.co.uk ` (2 preceding siblings ...) 2023-02-25 6:44 ` [Bug tree-optimization/66364] " pinskia at gcc dot gnu.org @ 2023-02-26 1:34 ` pinskia at gcc dot gnu.org 2023-02-26 2:19 ` pinskia at gcc dot gnu.org 2024-03-08 22:12 ` pinskia at gcc dot gnu.org 5 siblings, 0 replies; 7+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-02-26 1:34 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66364 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |NEW Resolution|DUPLICATE |--- See Also| |https://gcc.gnu.org/bugzill | |a/show_bug.cgi?id=55658 --- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> --- So in the end this is not an exact dup of bug 55658 as the patch I did does not change the code here but does fix PR 55658 . ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/66364] poor optimization of packed structs containing bitfields 2015-06-01 15:35 [Bug c++/66364] New: poor optimization of packed structs containing bitfields rogero at howzatt dot demon.co.uk ` (3 preceding siblings ...) 2023-02-26 1:34 ` pinskia at gcc dot gnu.org @ 2023-02-26 2:19 ` pinskia at gcc dot gnu.org 2024-03-08 22:12 ` pinskia at gcc dot gnu.org 5 siblings, 0 replies; 7+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-02-26 2:19 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66364 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |ASSIGNED --- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> --- The reason why the patch for PR 55658 didn't have any effect here is because by the time get_best_mode is called, bitregion_start and bitregion_end are set to 0 because they don't get passed down. So if we do lowering of the bitfield early on, then we should be able to get the correct behavior ... Double checking that. ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/66364] poor optimization of packed structs containing bitfields 2015-06-01 15:35 [Bug c++/66364] New: poor optimization of packed structs containing bitfields rogero at howzatt dot demon.co.uk ` (4 preceding siblings ...) 2023-02-26 2:19 ` pinskia at gcc dot gnu.org @ 2024-03-08 22:12 ` pinskia at gcc dot gnu.org 5 siblings, 0 replies; 7+ messages in thread From: pinskia at gcc dot gnu.org @ 2024-03-08 22:12 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66364 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |dan at stahlke dot org --- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> --- *** Bug 114289 has been marked as a duplicate of this bug. *** ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2024-03-08 22:12 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2015-06-01 15:35 [Bug c++/66364] New: poor optimization of packed structs containing bitfields rogero at howzatt dot demon.co.uk 2020-05-11 5:32 ` [Bug middle-end/66364] " egallager at gcc dot gnu.org 2021-08-11 0:31 ` pinskia at gcc dot gnu.org 2023-02-25 6:44 ` [Bug tree-optimization/66364] " pinskia at gcc dot gnu.org 2023-02-26 1:34 ` pinskia at gcc dot gnu.org 2023-02-26 2:19 ` pinskia at gcc dot gnu.org 2024-03-08 22:12 ` pinskia at gcc dot gnu.org
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).