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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/106155] [12/13 Regression] spurious "may be used uninitialized" warning Date: Wed, 31 Aug 2022 14:04:11 +0000 [thread overview] Message-ID: <bug-106155-4-tOtuwdKj0D@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-106155-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106155 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot gnu.org Status|NEW |ASSIGNED --- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> --- The issue here is that we see <bb 3> [local count: 805306369]: # emax_41 = PHI <emax_9(9), emax_22(D)(2)> # ivtmp.7_44 = PHI <ivtmp.7_45(9), 0(2)> i_46 = (int) ivtmp.7_44; if (i_46 == 2) goto <bb 4>; [12.49%] // init else goto <bb 10>; [87.51%] ... <bb 7> [local count: 805306369]: fh.1_6 = fh; f4 (fh.1_6); e.2_7 = e; *e.2_7 = 0; f1 (); if (ivtmp.7_44 == 2) goto <bb 8>; [12.49%] // use else goto <bb 9>; [87.51%] and the predicates i_46 == 2 and ivtmp.7_44 == 2 do not match up. Oh, and my r13-2149-g200baf7698a100 change made us run into if (dominated_by_p (CDI_POST_DOMINATORS, def_bb, use_bb)) /* The use is not guarded. */ return false; for this use on the loop exit because post-dominance doesn't cover loop exit conditions. I will think about this a bit more. I'll also note it is a missed optimization to not replace the i_46 == 2 check. -fno-ivopts makes the warning disappear (when the above is fixed). For some reason we do not optimize the i_46 = (int) ivtmp.7_44; if (i_46 == 2) stmt, likely because ivtmp is 64bit while i is 32bit and we don't check ivtmps value range here.
next prev parent reply other threads:[~2022-08-31 14:04 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-07-01 1:49 [Bug tree-optimization/106155] New: " vincent-gcc at vinc17 dot net 2022-07-01 2:05 ` [Bug tree-optimization/106155] " vincent-gcc at vinc17 dot net 2022-07-01 2:32 ` pinskia at gcc dot gnu.org 2022-07-01 2:43 ` pinskia at gcc dot gnu.org 2022-07-04 12:09 ` marxin at gcc dot gnu.org 2022-07-25 15:27 ` rguenth at gcc dot gnu.org 2022-08-31 14:04 ` rguenth at gcc dot gnu.org [this message] 2022-09-06 12:57 ` rguenth at gcc dot gnu.org 2022-09-06 13:17 ` rguenth at gcc dot gnu.org 2022-09-06 13:21 ` rguenth at gcc dot gnu.org 2022-10-17 12:30 ` rguenth at gcc dot gnu.org 2022-11-23 16:44 ` vincent-gcc at vinc17 dot net 2023-05-08 12:24 ` [Bug tree-optimization/106155] [12/13/14 " rguenth at gcc dot gnu.org 2023-06-13 2:03 ` vincent-gcc at vinc17 dot net
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