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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/109945] Escape analysis hates copy elision: different result with -O1 vs -O2 Date: Tue, 20 Feb 2024 12:33:58 +0000 [thread overview] Message-ID: <bug-109945-4-aJJg04xi85@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-109945-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109945 --- Comment #27 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #25) > > Since it's unspecified, the program cannot rely on any particular behaviour. > The 'global' pointer might point to w, or it might point to a temporary > which has gone out of scope, and in the latter case, dereferencing it in g() > is UB. > > So inconsistent behaviour with different optimization settings and/or noipa > attributes seems fine. Either global == &w or the program has UB. Hmm, so GCC thinks that global != &w does always hold and would optimize an explicit compare that way. Whether or not it actually creates a temporary. Is that invalid optimization? That is, do we need to consider that global _might_ point to w? We currently think it can never point to w. > I think this is INVALID.
next prev parent reply other threads:[~2024-02-20 12:33 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-05-23 14:00 [Bug c++/109945] New: " arthur.j.odwyer at gmail dot com 2023-05-23 16:09 ` [Bug tree-optimization/109945] " rguenth at gcc dot gnu.org 2023-05-23 16:11 ` rguenth at gcc dot gnu.org 2023-05-23 16:19 ` pinskia at gcc dot gnu.org 2023-05-23 16:48 ` rguenth at gcc dot gnu.org 2023-05-23 16:53 ` rguenth at gcc dot gnu.org 2023-05-23 16:53 ` pinskia at gcc dot gnu.org 2023-05-23 17:46 ` arthur.j.odwyer at gmail dot com 2023-05-23 17:49 ` pinskia at gcc dot gnu.org 2023-05-23 17:52 ` pinskia at gcc dot gnu.org 2023-05-23 17:53 ` pinskia at gcc dot gnu.org 2023-05-23 19:38 ` arthur.j.odwyer at gmail dot com 2023-05-24 6:48 ` rguenth at gcc dot gnu.org 2023-05-24 7:59 ` rguenth at gcc dot gnu.org 2023-05-24 8:16 ` jakub at gcc dot gnu.org 2023-05-24 8:42 ` rguenther at suse dot de 2023-05-24 8:51 ` jakub at gcc dot gnu.org 2023-05-24 8:55 ` rguenther at suse dot de 2023-05-24 9:00 ` jakub at gcc dot gnu.org 2023-05-24 10:12 ` rguenth at gcc dot gnu.org 2023-07-01 23:37 ` pinskia at gcc dot gnu.org 2023-07-10 8:52 ` rguenth at gcc dot gnu.org 2024-02-20 9:58 ` rguenth at gcc dot gnu.org 2024-02-20 10:45 ` jakub at gcc dot gnu.org 2024-02-20 11:53 ` jakub at gcc dot gnu.org 2024-02-20 12:07 ` redi at gcc dot gnu.org 2024-02-20 12:15 ` redi at gcc dot gnu.org 2024-02-20 12:33 ` rguenth at gcc dot gnu.org [this message] 2024-02-20 12:41 ` redi at gcc dot gnu.org 2024-02-20 12:48 ` jakub at gcc dot gnu.org 2024-02-20 15:47 ` arthur.j.odwyer at gmail dot com 2024-02-20 15:52 ` arthur.j.odwyer at gmail dot com 2024-02-20 16:49 ` redi at gcc dot gnu.org 2024-03-01 17:20 ` redi at gcc dot gnu.org
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