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From: "pinskia 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: Fri, 01 Jul 2022 02:32:45 +0000 [thread overview] Message-ID: <bug-106155-4-16xDPwqPxg@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 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2022-07-01 Keywords| |missed-optimization Status|UNCONFIRMED |NEW Target Milestone|--- |12.2 Ever confirmed|0 |1 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- init_from_control_deps {{0 -> 3}}: i_44 != 2 (expanded) NOT (i_44 == 2) After normalization [DEF]: i_44 != 2 (expanded) NOT (i_44 == 2) After normalization [USE]: f2 (emax_8); is conditional on: ivtmp.7_37 == 2 (expanded) ivtmp.7_37 == 2 Which is funny we get: # ivtmp.7_37 = PHI <ivtmp.7_38(9), 0(2)> i_44 = (int) ivtmp.7_37; if (i_44 == 2) goto <bb 4>; [12.49%] else goto <bb 10>; [87.51%] .... if (ivtmp.7_37 == 2) goto <bb 8>; [12.49%] else goto <bb 9>; [87.51%] <bb 8> [local count: 268435456]: f2 (emax_8); I don't know why ivopts only changed the second if and not the first. Oh because the second is the exit check: Replacing exit test: if (ivtmp_39 != 0) Replacing exit test: if (i_40 == 2) If we change the size to 4 and keep the 2 as 2, there would be no warning. And if then change 2 to 3, the warning is back. So there is a missed optimization of changing the internal comparison for the IV to the new type if the right side is a constant.
next prev parent reply other threads:[~2022-07-01 2:32 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 [this message] 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 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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