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From: "law at redhat dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/94734] [10 Regression] Program crashes when compiled with -O2 since r10-1892-gb9ef6a2e04bfd013 Date: Fri, 24 Apr 2020 00:48:18 +0000 [thread overview] Message-ID: <bug-94734-4-1INmCb3uWR@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-94734-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94734 --- Comment #6 from Jeffrey A. Law <law at redhat dot com> --- THe whole point of that change is to not require a dominating load if the object comes from the stack. We conditionally load from the same location, then have a PHI which selects that loaded value or "1" and we store the result. That's precisely what is supposed to be happening. The loop in question looks like: ;; basic block 3, loop depth 1 ;; pred: 2 ;; 6 # ivtmp.13_9 = PHI <0(2), ivtmp.13_7(6)> _4 = MEM[base: in_21(D), index: ivtmp.13_9, step: 8, offset: 0B]; if (_4 == 0B) goto <bb 13>; [5.50%] else goto <bb 4>; [94.50%] ;; succ: 13 ;; 4 ;; basic block 4, loop depth 1 ;; pred: 3 if (ivtmp.13_9 != 2) goto <bb 6>; [28.10%] else goto <bb 5>; [71.90%] ;; succ: 6 ;; 5 ;; basic block 5, loop depth 1 ;; pred: 4 cstore_32 = MEM[symbol: arr, index: ivtmp.13_9, step: 4, offset: 0B]; ;; succ: 6 ;; basic block 6, loop depth 1 ;; pred: 5 ;; 4 # cstore_31 = PHI <cstore_32(5), 1(4)> MEM[symbol: arr, index: ivtmp.13_9, step: 4, offset: 0B] = cstore_31; _40 = (unsigned int) ivtmp.13_9; _38 = _40 + 1; _37 = (int) _38; ivtmp.13_7 = ivtmp.13_9 + 1; sum_a_27 = (int) ivtmp.13_7; if (n_16(D) > sum_a_27) goto <bb 3>; [94.50%] else goto <bb 7>; [5.50%] ;; succ: 3 ;; 7 You can see the load from the same stock slot in bb5, the selecting PHI in bb6 and the store in bb6. THe test in bb4 looks weird and is the source of the problem I believe.
next prev parent reply other threads:[~2020-04-24 0:48 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-04-23 17:17 [Bug c/94734] New: Program crashes when compiled with GCC 10 john+gcc at hogberg dot online 2020-04-23 18:12 ` [Bug c/94734] " john+gcc at hogberg dot online 2020-04-23 19:19 ` [Bug tree-optimization/94734] [10 Regression] Program crashes when compiled with -O2 since r10-1892-gb9ef6a2e04bfd013 marxin at gcc dot gnu.org 2020-04-23 21:24 ` law at redhat dot com 2020-04-23 23:24 ` jakub at gcc dot gnu.org 2020-04-23 23:25 ` jakub at gcc dot gnu.org 2020-04-24 0:48 ` law at redhat dot com [this message] 2020-04-24 5:20 ` jakub at gcc dot gnu.org 2020-04-24 7:52 ` rguenth at gcc dot gnu.org 2020-04-24 7:55 ` rguenth at gcc dot gnu.org 2020-04-24 8:34 ` jakub at gcc dot gnu.org 2020-04-24 8:59 ` jakub at gcc dot gnu.org 2020-04-24 9:03 ` rguenther at suse dot de 2020-04-24 9:09 ` jakub at gcc dot gnu.org 2020-04-24 9:19 ` jakub at gcc dot gnu.org 2020-04-24 9:22 ` rguenth at gcc dot gnu.org 2020-04-24 9:29 ` jakub at gcc dot gnu.org 2020-04-24 10:37 ` jakub at gcc dot gnu.org 2020-04-24 22:10 ` cvs-commit at gcc dot gnu.org 2020-04-24 22:24 ` jakub at gcc dot gnu.org
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