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* [Bug c++/108920] New: Condition falsely optimized out @ 2023-02-24 10:25 agner at agner dot org 2023-02-24 13:06 ` [Bug c++/108920] " rguenth at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: agner at agner dot org @ 2023-02-24 10:25 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108920 Bug ID: 108920 Summary: Condition falsely optimized out Product: gcc Version: 9.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: agner at agner dot org Target Milestone: --- Created attachment 54526 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54526&action=edit code to reproduce error The attached file test.cpp gives wrong code when optimized with -O2 or higher. To reproduce error, do: g++ -O2 -m64 -S -o t1.s test.cpp g++ -O2 -m64 -S -DFIX -o t2.s test.cpp The condition in line 104 in test.cpp is optimized away in t1.s The workaround on line 73 is preventing this false optimization with -DFIX to generate correct code in t2.s See t2.s line 252-255 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/108920] Condition falsely optimized out 2023-02-24 10:25 [Bug c++/108920] New: Condition falsely optimized out agner at agner dot org @ 2023-02-24 13:06 ` rguenth at gcc dot gnu.org 2023-02-25 0:32 ` [Bug middle-end/108920] " pinskia at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: rguenth at gcc dot gnu.org @ 2023-02-24 13:06 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108920 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2023-02-24 Status|UNCONFIRMED |WAITING Ever confirmed|0 |1 Keywords| |wrong-code --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- I wonder if you can test a newer GCC release since we are no longer maintaining GCC 9.3. In particular there's also the GCC 9.5 release (the last release from the GCC 9 series), and GCC 10.4, GCC 11.3 and GCC 12.2 (the last releases from the three maintained release series). Is there a way to observe the issue at runtime? That would facilitate bisecting. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/108920] Condition falsely optimized out 2023-02-24 10:25 [Bug c++/108920] New: Condition falsely optimized out agner at agner dot org 2023-02-24 13:06 ` [Bug c++/108920] " rguenth at gcc dot gnu.org @ 2023-02-25 0:32 ` pinskia at gcc dot gnu.org 2023-02-25 6:34 ` agner at agner dot org 2023-02-25 8:50 ` agner at agner dot org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-02-25 0:32 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108920 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- See Also| |https://gcc.gnu.org/bugzill | |a/show_bug.cgi?id=97009, | |https://gcc.gnu.org/bugzill | |a/show_bug.cgi?id=97255 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- I linked a few bugs which might be the same issue here (I have not looked into the code otherwise) and they were both fixed in GCC 9.4.0 even. So yes please try out GCC 9.5.0 or 10.x even. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/108920] Condition falsely optimized out 2023-02-24 10:25 [Bug c++/108920] New: Condition falsely optimized out agner at agner dot org 2023-02-24 13:06 ` [Bug c++/108920] " rguenth at gcc dot gnu.org 2023-02-25 0:32 ` [Bug middle-end/108920] " pinskia at gcc dot gnu.org @ 2023-02-25 6:34 ` agner at agner dot org 2023-02-25 8:50 ` agner at agner dot org 3 siblings, 0 replies; 5+ messages in thread From: agner at agner dot org @ 2023-02-25 6:34 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108920 --- Comment #3 from Agner Fog <agner at agner dot org> --- It seems to work with gcc 9.4.0. Thank you ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/108920] Condition falsely optimized out 2023-02-24 10:25 [Bug c++/108920] New: Condition falsely optimized out agner at agner dot org ` (2 preceding siblings ...) 2023-02-25 6:34 ` agner at agner dot org @ 2023-02-25 8:50 ` agner at agner dot org 3 siblings, 0 replies; 5+ messages in thread From: agner at agner dot org @ 2023-02-25 8:50 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108920 Agner Fog <agner at agner dot org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|WAITING |RESOLVED Resolution|--- |FIXED --- Comment #4 from Agner Fog <agner at agner dot org> --- I am not sure I have identified the problem correctly, but there is no need to spend more time on it since the problem disappears with version 9.4.0. You may close this issue. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-02-25 8:50 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2023-02-24 10:25 [Bug c++/108920] New: Condition falsely optimized out agner at agner dot org 2023-02-24 13:06 ` [Bug c++/108920] " rguenth at gcc dot gnu.org 2023-02-25 0:32 ` [Bug middle-end/108920] " pinskia at gcc dot gnu.org 2023-02-25 6:34 ` agner at agner dot org 2023-02-25 8:50 ` agner at agner dot org
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