From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30695 invoked by alias); 19 Jun 2011 15:30:17 -0000 Received: (qmail 30683 invoked by uid 22791); 19 Jun 2011 15:30:17 -0000 X-SWARE-Spam-Status: No, hits=-2.7 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Sun, 19 Jun 2011 15:30:03 +0000 From: "oleg.endo@t-online.de" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/49468] SH Target: inefficient integer abs code X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: oleg.endo@t-online.de X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- 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 Date: Sun, 19 Jun 2011 15:30:00 -0000 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: 2011-06/txt/msg01681.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49468 --- Comment #1 from Oleg Endo 2011-06-19 15:29:45 UTC --- Created attachment 24560 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24560 Proposed patch The patch adds explicit handling of abs:SI and abs:DI to the machine description instead of relying on the default abs handling. On SH4 the zero-offset branch way is definitely faster. It reduces pressure on EX group instructions and improves parallel instruction execution. On other than SH4 zero-offset branches are not as fast, but the resulting code should still be faster than the default branch-free abs code, at least it is more compact. The patch also handles the case of neg (abs (...)) by simply inverting the branch condition. Feedback appreciated.