From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 19456 invoked by alias); 4 Sep 2014 09:52:13 -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 Received: (qmail 19393 invoked by uid 48); 4 Sep 2014 09:52:09 -0000 From: "jakub at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/61559] FAIL: gcc.dg/builtin-bswap-8.c on i686 with -mmovbe Date: Thu, 04 Sep 2014 09:52:00 -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-Version: 5.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: jakub at gcc dot gnu.org X-Bugzilla-Status: ASSIGNED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: rguenth at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: cc Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2014-09/txt/msg01024.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61559 Jakub Jelinek changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jakub at gcc dot gnu.org --- Comment #9 from Jakub Jelinek --- Aren't these optimizations actually a pessimization for -mmovbe if the inner bswap is on a read from memory? Assuming the load and bswap instruction is cheap, then e.g. loading two values with bswap on them and doing say xor on them afterwards might be cheaper than load the two values, xor them and then bswap them (because for that bswap you don't have a load+bswap instruction).