From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 18230 invoked by alias); 13 Nov 2012 15:14:20 -0000 Received: (qmail 18125 invoked by uid 48); 13 Nov 2012 15:13:59 -0000 From: "ubizjak at gmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/54073] [4.7/4.8 Regression] SciMark Monte Carlo test performance has seriously decreased in recent GCC releases Date: Tue, 13 Nov 2012 15:14:00 -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-Keywords: missed-optimization X-Bugzilla-Severity: normal X-Bugzilla-Who: ubizjak at gmail dot com X-Bugzilla-Status: NEW X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.7.3 X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2012-11/txt/msg01167.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54073 --- Comment #10 from Uros Bizjak 2012-11-13 15:13:56 UTC --- (In reply to comment #8) > The attached proof of concept patch attempts to just restore the 4.6 and > earlier behavior by allowing in all comparisons. Of course perhaps it might be > possible it needs better tuning than that, I meant it just as a start for > discussions. Please see PR53346, from comment 14 onwards, especially H.J.'s comment: -quote- I was told that cmov wins if branch is mispredicted, otherwise cmov loses. We will investigate if we can improve cmov in GCC. -/quote-