From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 112464 invoked by alias); 8 Jun 2016 11:20:27 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 112454 invoked by uid 89); 8 Jun 2016 11:20:26 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.3 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=ist X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Wed, 08 Jun 2016 11:20:16 +0000 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E1544C049D5C; Wed, 8 Jun 2016 11:20:14 +0000 (UTC) Received: from localhost.localdomain (vpn1-4-158.ams2.redhat.com [10.36.4.158]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u58BKCHT016497; Wed, 8 Jun 2016 07:20:13 -0400 Subject: Re: [PATCH 1/2][v3] Drop excess size used for run time allocated stack variables. To: vogt@linux.vnet.ibm.com, Jeff Law , gcc-patches@gcc.gnu.org, Andreas Krebbel , Eric Botcazou References: <20160429221242.GA2205@linux.vnet.ibm.com> <20160503141753.GA17351@linux.vnet.ibm.com> <20160525133054.GA6938@linux.vnet.ibm.com> From: Bernd Schmidt Message-ID: <244457fe-3237-f0f3-da08-0bbab5c5e0e7@redhat.com> Date: Wed, 08 Jun 2016 11:20:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.0 MIME-Version: 1.0 In-Reply-To: <20160525133054.GA6938@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2016-06/txt/msg00570.txt.bz2 On 05/25/2016 03:30 PM, Dominik Vogt wrote: > * explow.c (allocate_dynamic_stack_space): Simplify knowing that > MUST_ALIGN was always true and extra_align ist always BITS_PER_UNIT. I tried to do some archaeology to find out how the code came to look the way it currently does. A relevant message appears to be https://gcc.gnu.org/ml/gcc-patches/2011-01/msg00836.html There's some discussion about how STACK_POINT_OFFSET shouldn't cause us to have to align, and postponing that optimization to gcc-4.7. Since STACK_POINTER_OFFSET should be constant, it ought to be easy enough to take it into account. So, I'm undecided. Your cleanup is valid as the code stands right now, but I'm undecided whether we shouldn't fix the potentially unnecessary extra alignment instead. Bernd