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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/97623] [9/10/11 Regression] Extremely slow O2 compile (>>O(n^2)) Date: Tue, 03 Nov 2020 14:16:17 +0000 [thread overview] Message-ID: <bug-97623-4-ap6g87nKQ2@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-97623-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97623 --- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to Wilson Snyder from comment #7) > Thanks for the quick service. I can't easily try GCC trunk, but: > > -O2 > compile 98.61s > runtime 25.76s > > -O2 -fno-code-hoisting > compile 40.13s > runtime 26.40s (+2.5%) Hmm, OK. Can you provide the output of -O2 -fno-code-hoisting -ftime-report? I have a patch limiting hoist insertions to 3 and that makes the reduced testcase drop from 13s to 2.5s and drop PRE into reasonable territory: tree PRE : 0.44 ( 18%) 0.00 ( 0%) 0.45 ( 18%) 1177k ( 5%) and with -fno-code-hoisting tree PRE : 0.37 ( 15%) 0.00 ( 0%) 0.38 ( 15%) 477k ( 2%) where it takes only two insert iterations (the last iteration is always a no-op, so that's perfect). Before limiting but after the already committed patch it was tree PRE : 10.41 ( 81%) 0.01 ( 33%) 10.48 ( 81%) 11M ( 33%) The function is quite big and ANTIC_IN compute is costly and more importantly AVAIL_OUT is quadratic in size (ugh). > -Os > compile 4.25s > runtime 23.42s (-10%) > > That -Os runs faster is expected as this program is generally > instruction-fetch limited. I'd have expected -fno-code-hoisting to help > more, compile time wise. Me, too. > Am I correct in understanding that the slowdown is roughly correlated to the > number of "if" or "?:" statements? Yeah, that's the case.
next prev parent reply other threads:[~2020-11-03 14:16 UTC|newest] Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-29 2:02 [Bug c++/97623] New: " wsnyder at wsnyder dot org 2020-10-29 2:03 ` [Bug c++/97623] " wsnyder at wsnyder dot org 2020-10-29 7:17 ` [Bug tree-optimization/97623] [9/10/11 Regression] " rguenth at gcc dot gnu.org 2020-10-29 7:18 ` rguenth at gcc dot gnu.org 2020-10-30 12:35 ` rguenth at gcc dot gnu.org 2020-10-30 12:35 ` rguenth at gcc dot gnu.org 2020-10-30 13:25 ` cvs-commit at gcc dot gnu.org 2020-10-30 13:28 ` rguenth at gcc dot gnu.org 2020-10-30 13:55 ` wsnyder at wsnyder dot org 2020-11-03 14:16 ` rguenth at gcc dot gnu.org [this message] 2020-11-03 15:23 ` cvs-commit at gcc dot gnu.org 2020-11-06 1:50 ` wsnyder at wsnyder dot org 2020-11-06 9:52 ` rguenther at suse dot de 2020-11-06 12:37 ` wsnyder at wsnyder dot org 2020-11-06 13:00 ` rguenth at gcc dot gnu.org 2020-11-06 13:19 ` marxin at gcc dot gnu.org 2020-11-06 13:28 ` rguenth at gcc dot gnu.org 2020-11-06 13:45 ` rguenth at gcc dot gnu.org 2020-11-11 11:51 ` cvs-commit at gcc dot gnu.org 2020-11-11 16:11 ` tschwinge at gcc dot gnu.org 2020-11-11 17:17 ` cvs-commit at gcc dot gnu.org 2020-12-07 13:03 ` [Bug tree-optimization/97623] [9/10 " rguenth at gcc dot gnu.org 2021-01-11 13:37 ` cvs-commit at gcc dot gnu.org 2021-01-11 13:37 ` cvs-commit at gcc dot gnu.org 2021-01-11 13:39 ` [Bug tree-optimization/97623] [9 " rguenth at gcc dot gnu.org 2021-06-01 8:18 ` rguenth at gcc dot gnu.org 2022-05-27 8:56 ` rguenth at gcc dot gnu.org
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