From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id CD28B3861893; Thu, 15 Apr 2021 07:35:50 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org CD28B3861893 From: "rguenth at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/100076] eembc/automotive/basefp01 has 30.3% regression compare -O2 -ftree-vectorize with -O2 on CLX/Znver3 Date: Thu, 15 Apr 2021 07:35:50 +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: 11.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: rguenth 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 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: Thu, 15 Apr 2021 07:35:50 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100076 Richard Biener changed: What |Removed |Added ---------------------------------------------------------------------------- Ever confirmed|0 |1 Last reconfirmed| |2021-04-15 Status|UNCONFIRMED |NEW --- Comment #5 from Richard Biener --- Note even when avoiding the STLF hit the vectorized version is slower. You can use -mtune-ctl=3D^sse_unaligned_load_optimal to force loading the lower/upper half of vectors separately. The reason is that without -ffast-math we are using an in-order reduction which doesn't save us much but instead just combines dependence chains here. We do have a related bug for this somewhere. With -ffast-math the version with/without -mtune-ctl=3D^sse_unaligned_load_optimal is about the same speed, so STLF is a red herring here (on Zen2). Still not vectorizing is a lot faster. Can you check if -mtune-ctl=3D^sse_unaligned_load_optimal helps on CLX?=