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From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/102981] [12 Regression] Dead Code Elimination Regression at -O3 (trunk vs 11.2.0) Date: Sat, 30 Oct 2021 07:03:09 +0000 [thread overview] Message-ID: <bug-102981-4-qb0tWAKlvd@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-102981-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102981 Aldy Hernandez <aldyh at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Ever confirmed|0 |1 Last reconfirmed| |2021-10-30 Status|UNCONFIRMED |NEW --- Comment #1 from Aldy Hernandez <aldyh at gcc dot gnu.org> --- In the pre-loop threaders (ethread, thread1, threadfull1), we can't touch anything because it would cross loops, but by threadfull2 we should be able to. There's a threadable path starting at the 2->6 edge here: <bb 6> [local count: 118111600]: # c_21 = PHI <c_30(5), 0(2)> # ivtmp.16_8 = PHI <ivtmp.16_13(5), ivtmp.16_25(2)> a.1_26 = a; if (a.1_26 < 0) goto <bb 12>; [89.00%] else goto <bb 10>; [11.00%] but we don't because doing so would peel off an iteration. Hmmm, this is really old code. I'm going to have to think about this: // This is like path_crosses_loops in profitable_path_p but more // restrictive, since profitable_path_p allows threading the // first block because it would be redirected anyhow. // // If we loosened the restriction and used profitable_path_p() // here instead, we would peel off the first iterations of loops // in places like tree-ssa/pr14341.c.
next prev parent reply other threads:[~2021-10-30 7:03 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-10-28 9:38 [Bug tree-optimization/102981] New: " theodort at inf dot ethz.ch 2021-10-28 11:45 ` [Bug tree-optimization/102981] " rguenth at gcc dot gnu.org 2021-10-30 7:03 ` aldyh at gcc dot gnu.org [this message] 2021-10-30 17:42 ` aldyh at gcc dot gnu.org 2021-10-30 18:08 ` aldyh at gcc dot gnu.org 2021-11-04 18:47 ` law at gcc dot gnu.org 2021-11-16 20:08 ` aldyh at gcc dot gnu.org 2021-11-17 9:49 ` aldyh at gcc dot gnu.org 2021-11-23 19:19 ` aldyh at gcc dot gnu.org 2022-05-06 8:31 ` [Bug tree-optimization/102981] [12/13 " jakub at gcc dot gnu.org 2023-05-08 12:22 ` [Bug tree-optimization/102981] [12/13/14 " rguenth at gcc dot gnu.org
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