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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/67196] [10/11/12/13 Regression] loop-induced false positive from -Wmaybe-uninitialized Date: Tue, 30 Aug 2022 09:40:38 +0000 [thread overview] Message-ID: <bug-67196-4-bZFAoSigdv@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-67196-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67196 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot gnu.org --- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> --- The issue is that the code supposed to deal with this, uninit_analysis::overlap, does not handle the case of chained PHIs very well, that is, <bb 5> [local count: 955630225]: # num_captions_in_row_5 = PHI <num_captions_in_row_25(11), num_captions_in_row_18(4)> # first_caption_7 = PHI <first_caption_27(11), 1(4)> # first_caption_idx_9 = PHI <first_caption_idx_29(11), i_31(4)> i_19 = i_31 + 1; if (n_16(D) != i_19) goto <bb 12>; [89.00%] else goto <bb 6>; [11.00%] ... <bb 6> [local count: 105119324]: _2 = first_caption_7 != 0; _3 = num_captions_in_row_5 == 1; _4 = _2 & _3; if (_4 != 0) goto <bb 7>; [38.20%] else goto <bb 13>; [61.80%] ... <bb 8> [local count: 118111600]: # _12 = PHI <first_caption_idx_9(7), 0(13), 0(10)> return _12; the code searchess for a PHI definition of num_captions_in_row_5 in the same block as the _12 = PHI <>, not realizing that uninit analysis also includes edges from the _9 = PHI <> in BB5 where the definition ultimatively resides. Then there's the issue that use predicates are not yet normalized at this point so there's still the _4 != 0 test instead of the two ANDed ones. With both fixed the diagnostic is gone.
next prev parent reply other threads:[~2022-08-30 9:40 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-08-12 19:03 [Bug tree-optimization/67196] New: Another " dmalcolm at gcc dot gnu.org 2015-08-12 20:26 ` [Bug tree-optimization/67196] " manu at gcc dot gnu.org 2021-03-31 19:44 ` [Bug tree-optimization/67196] [9/10/11 Regression] loop-induced " msebor at gcc dot gnu.org 2021-04-08 14:24 ` rguenth at gcc dot gnu.org 2021-06-01 8:06 ` [Bug tree-optimization/67196] [9/10/11/12 " rguenth at gcc dot gnu.org 2022-01-21 13:53 ` rguenth at gcc dot gnu.org 2022-05-27 9:35 ` [Bug tree-optimization/67196] [10/11/12/13 " rguenth at gcc dot gnu.org 2022-06-28 10:31 ` jakub at gcc dot gnu.org 2022-08-30 9:40 ` rguenth at gcc dot gnu.org [this message] 2022-08-30 11:15 ` cvs-commit at gcc dot gnu.org 2022-11-20 3:56 ` [Bug tree-optimization/67196] [10/11/12 " law at gcc dot gnu.org 2022-11-21 6:47 ` rguenth at gcc dot gnu.org 2023-07-07 7:28 ` [Bug tree-optimization/67196] [11/12 " rguenth at gcc dot gnu.org
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