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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/103281] [9/12 Regression] Dead Code Elimination Regression at -O3 (trunk vs 11.2.0) Date: Tue, 16 Nov 2021 20:51:29 +0000 [thread overview] Message-ID: <bug-103281-4-ggZex9EG5w@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-103281-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103281 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Target Milestone|--- |12.0 Keywords| |missed-optimization Ever confirmed|0 |1 Known to fail| |10.1.0, 12.0, 4.7.1, 4.8.1, | |9.1.0 Summary|[12 Regression] Dead Code |[9/12 Regression] Dead Code |Elimination Regression at |Elimination Regression at |-O3 (trunk vs 11.2.0) |-O3 (trunk vs 11.2.0) Last reconfirmed| |2021-11-16 Known to work| |11.1.0, 4.9.0, 4.9.4, | |5.1.0, 6.1.0, 7.1.0, 8.1.0 Status|UNCONFIRMED |NEW --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- The only thing which PHIOPT does is change: if (c_15 == 0) goto <bb 4>; [INV] else goto <bb 5>; [INV] <bb 4> : <bb 5> : # iftmp.1_10 = PHI <0(4), c_15(3)> to be: iftmp.1_10 = c_15; This is a missed VRP: # RANGE [0, 2] NONZERO 3 c_9 = (charD.10) b.4_5; _1 = c_9 <= 0; # RANGE [0, 1] NONZERO 1 _2 = (unsigned intD.14) _1; if (_2 == b.4_5) _1/_2 is true/1 only when c_9 is 0 and only when b.4_5 is 0. ----- CUT ----- We should be able to optimize: void foo(void); static unsigned b; int main() { for (; b < 3; b++) { char c = b; char a = c; if (!((a < 1) ^ b)) foo(); } } Too. We also miss: void foo(void); static unsigned b; int main() { for (; b < 3; b++) { if (!((b < 1) ^ b)) foo(); } } _1 = b.2_6 == 0; _2 = (unsigned int) _1; if (_2 == b.2_6) I want to say we should defer this until after GCC 12 because this was only being optimized on accident. phiopt1
next prev parent reply other threads:[~2021-11-16 20:51 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-11-16 18:31 [Bug tree-optimization/103281] New: [12 " theodort at inf dot ethz.ch 2021-11-16 20:51 ` pinskia at gcc dot gnu.org [this message] 2021-11-16 20:52 ` [Bug tree-optimization/103281] [9/10/12 " pinskia at gcc dot gnu.org 2021-11-16 21:03 ` pinskia at gcc dot gnu.org 2021-11-16 21:16 ` pinskia at gcc dot gnu.org 2021-11-18 10:31 ` marxin at gcc dot gnu.org 2022-01-18 14:28 ` rguenth at gcc dot gnu.org 2022-05-27 9:46 ` [Bug tree-optimization/103281] [10/12/13 " rguenth at gcc dot gnu.org 2022-06-28 10:46 ` jakub at gcc dot gnu.org 2023-05-01 23:49 ` [Bug tree-optimization/103281] [10/12/13/14 " pinskia at gcc dot gnu.org 2023-08-07 5:47 ` [Bug tree-optimization/103281] [12/13/14 " pinskia at gcc dot gnu.org 2023-08-07 6:34 ` pinskia at gcc dot gnu.org 2023-08-07 6:34 ` pinskia at gcc dot gnu.org 2023-08-08 15:42 ` cvs-commit at gcc dot gnu.org 2023-08-08 15:43 ` pinskia at gcc dot gnu.org 2023-08-08 15:46 ` pinskia at gcc dot gnu.org
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