From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id E07F63857806; Fri, 6 Nov 2020 13:00:15 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E07F63857806 From: "rguenth at gcc dot 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: Fri, 06 Nov 2020 13:00:15 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: tree-optimization X-Bugzilla-Version: 9.3.1 X-Bugzilla-Keywords: compile-time-hog, needs-bisection X-Bugzilla-Severity: normal X-Bugzilla-Who: rguenth at gcc dot gnu.org X-Bugzilla-Status: ASSIGNED X-Bugzilla-Resolution: X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: rguenth at gcc dot gnu.org X-Bugzilla-Target-Milestone: 9.4 X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: keywords Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: gcc-bugs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-bugs mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 06 Nov 2020 13:00:16 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97623 Richard Biener changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |needs-bisection --- Comment #13 from Richard Biener --- OK, on that testcase the good news is that GCC 10 is much better than GCC 9 resulting in -O2 -fno-code-hoisting tree PRE : 2.25 ( 50%) 0.05 ( 20%) 2.32 ( = 49%) 31794 kB ( 20%) TOTAL : 4.47 0.25 4.72=20= =20=20=20=20=20=20 161356 kB compared to GCC 9 where I can indeed reproduce tree PRE : 37.81 ( 95%) 0.04 ( 13%) 37.96 ( = 95%) 32604 kB ( 20%) TOTAL : 39.63 0.30 39.99=20= =20=20=20=20=20=20 161584 kB suspicious are diffs in insertions and insert iterations: Insertions: 1258 insert iterations =3D=3D 3: 1 Eliminated: 1553 vs bad: Insertions: 8616 insert iterations =3D=3D 128: 1 Eliminated: 8955 I wonder what triggered this change ... On patched trunk we're in the same ballpark as GCC 10 but without requiring -fno-code-hoisting. The testcase is still an interesting one for PRE (50% of the compile spent there is a bit much, even if just 2 seconds).=