From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 5287 invoked by alias); 20 Oct 2015 13:09:30 -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 5224 invoked by uid 48); 20 Oct 2015 13:09:26 -0000 From: "yann.collet.73 at gmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c/67435] Feature request: Implement align-loops attribute Date: Tue, 20 Oct 2015 13:09:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c X-Bugzilla-Version: 4.8.4 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: yann.collet.73 at gmail dot com 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: 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: 2015-10/txt/msg01609.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67435 --- Comment #10 from Yann Collet --- > there already is an aligned attribute for functions, variables and fields, Sure, but none of them is related to aligning the start of an hot instruction loop. Aligning the function instead looks like a poor proxy. > there are also drawbacks to high alignment values Yes. I could test that using -falign-loops=32 on a larger code base produces drawbacks. Not just larger code size, worse speed speed. This makes it all the more relevant to have the ability to select which loop should be aligned, instead of relying on a unique program-wide compilation flag.