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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/51049] A regression caused by "Improve handling of conditional-branches on targets with high branch costs" Date: Thu, 03 Aug 2023 05:12:55 +0000 [thread overview] Message-ID: <bug-51049-4-jukPjhoTwz@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-51049-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51049 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- So at -O1 we get what we expect: ``` _1 = *i_4(D); _7 = j_5(D) != 2; _8 = _1 != 0; _9 = _7 & _8; if (_9 != 0) goto <bb 3>; [43.56%] else goto <bb 4>; [56.44%] <bb 3> [local count: 467721933]: _6 = (int) _1; <bb 4> [local count: 1073741824]: # _2 = PHI <_6(3), j_5(D)(2)> ``` But at -O2 we get: ``` if (_1 != 0) goto <bb 3>; [66.00%] else goto <bb 5>; [34.00%] <bb 3> [local count: 708669599]: if (j_5(D) != 2) goto <bb 4>; [66.00%] else goto <bb 5>; [34.00%] <bb 4> [local count: 467721933]: _6 = (int) _1; <bb 5> [local count: 1073741824]: # _2 = PHI <_6(4), j_5(D)(3), j_5(D)(2)> ``` Because VRP comes along and replaces j_5(D) with 2 along the edge `3->5` and ifcombine does not do handle that as the phi entries are different (but maybe can be proved as the same).
prev parent reply other threads:[~2023-08-03 5:12 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-11-09 7:49 [Bug tree-optimization/51049] New: " liujiangning at gcc dot gnu.org 2011-11-09 7:52 ` [Bug tree-optimization/51049] " liujiangning at gcc dot gnu.org 2011-11-09 9:23 ` rguenth at gcc dot gnu.org 2023-08-03 5:12 ` pinskia at gcc dot gnu.org [this message]
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