From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 661113858433; Fri, 15 Oct 2021 00:29:27 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 661113858433 From: "pinskia at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/102756] [12 Regression] Complete unrolling is too senative to PRE; c-c++-common/torture/vector-compare-2.c Date: Fri, 15 Oct 2021 00:29:27 +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: 12.0 X-Bugzilla-Keywords: missed-optimization X-Bugzilla-Severity: normal X-Bugzilla-Who: pinskia at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: everconfirmed cf_reconfirmed_on keywords short_desc bug_status 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, 15 Oct 2021 00:29:27 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102756 Andrew Pinski changed: What |Removed |Added ---------------------------------------------------------------------------- Ever confirmed|0 |1 Last reconfirmed| |2021-10-15 Keywords| |missed-optimization Summary|[12 Regression] Vectorizer |[12 Regression] Complete |change creates poor code |unrolling is too senative |for |to PRE; |c-c++-common/torture/vector |c-c++-common/torture/vector |-compare-2.c |-compare-2.c Status|UNCONFIRMED |NEW --- Comment #1 from Andrew Pinski --- With -ftree-vectorize size: 7-4, last_iteration: 7-4 Loop size: 7 Estimated size after unrolling: 8 _1 =3D VIEW_CONVERT_EXPR(r)[i_10]; With -fno-tree-vectorize size: 7-4, last_iteration: 6-4 Loop size: 7 Estimated size after unrolling: 7 pretmp_2 =3D MEM[(vector(4) int *)&r][i_7]; Also -O2 -fno-tree-vectorize -fno-tree-pre produces the same as the -O2 -ftree-vectorize case. ------------------- CUT ---------------------------- Loop 1 iterates 3 times. Loop 1 iterates at most 3 times. Loop 1 likely iterates at most 3 times. Estimating sizes for loop 1 BB: 3, after_exit: 0 size: 1 _1 =3D VIEW_CONVERT_EXPR(r)[i_10]; size: 2 if (_1 !=3D -3) BB: 7, after_exit: 1 BB: 5, after_exit: 0 size: 1 i_7 =3D i_10 + 1; Induction variable computation will be folded away. size: 1 ivtmp_9 =3D ivtmp_2 - 1; Induction variable computation will be folded away. size: 2 if (ivtmp_9 !=3D 0) Exit condition will be eliminated in peeled copies. Exit condition will be eliminated in last copy. Constant conditional. size: 7-4, last_iteration: 7-4 Loop size: 7 Estimated size after unrolling: 8 Not unrolling loop 1: size would grow. vs: Estimating sizes for loop 1 BB: 3, after_exit: 0 size: 2 if (prephitmp_9 !=3D -3) BB: 6, after_exit: 1 size: 1 pretmp_2 =3D MEM[(vector(4) int *)&r][i_7]; BB: 5, after_exit: 0 size: 1 i_7 =3D i_10 + 1; Induction variable computation will be folded away. size: 1 ivtmp_11 =3D ivtmp_1 - 1; Induction variable computation will be folded away. size: 2 if (ivtmp_11 !=3D 0) Exit condition will be eliminated in peeled copies. Exit condition will be eliminated in last copy. Constant conditional. size: 7-4, last_iteration: 6-4 Loop size: 7 Estimated size after unrolling: 7 PRE decides to do the load for MEM[(vector(4) int *)&r][0] which is why the last iteration is 6-4 rather than 7-4.=