From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17427 invoked by alias); 1 Jun 2009 16:11:12 -0000 Received: (qmail 17414 invoked by uid 22791); 1 Jun 2009 16:11:11 -0000 X-SWARE-Spam-Status: No, hits=-2.6 required=5.0 tests=AWL,BAYES_00,SPF_PASS X-Spam-Check-By: sourceware.org Received: from smtp-out.google.com (HELO smtp-out.google.com) (216.239.33.17) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 01 Jun 2009 16:11:04 +0000 Received: from spaceape23.eur.corp.google.com (spaceape23.eur.corp.google.com [172.28.16.75]) by smtp-out.google.com with ESMTP id n51GB025005883 for ; Mon, 1 Jun 2009 17:11:00 +0100 Received: from wf-out-1314.google.com (wfg24.prod.google.com [10.142.7.24]) by spaceape23.eur.corp.google.com with ESMTP id n51GApkg015995 for ; Mon, 1 Jun 2009 09:10:59 -0700 Received: by wf-out-1314.google.com with SMTP id 24so2210059wfg.7 for ; Mon, 01 Jun 2009 09:10:58 -0700 (PDT) Received: by 10.142.90.5 with SMTP id n5mr2058630wfb.39.1243872658582; Mon, 01 Jun 2009 09:10:58 -0700 (PDT) Received: from localhost.localdomain.google.com (adsl-71-133-8-30.dsl.pltn13.pacbell.net [71.133.8.30]) by mx.google.com with ESMTPS id n40sm5822574wag.30.2009.06.01.09.10.57 (version=TLSv1/SSLv3 cipher=RC4-MD5); Mon, 01 Jun 2009 09:10:58 -0700 (PDT) To: Alexandre Oliva Cc: gcc-patches@gcc.gnu.org Subject: Re: [trunk<-vta] Re: [vtab] Permit coalescing of user variables References: <4702B1C0.80807@redhat.com> From: Ian Lance Taylor Date: Mon, 01 Jun 2009 16:11:00 -0000 In-Reply-To: (Alexandre Oliva's message of "Mon\, 01 Jun 2009 04\:38\:46 -0300") Message-ID: User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-System-Of-Record: true X-IsSubscribed: yes 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 X-SW-Source: 2009-06/txt/msg00076.txt.bz2 Alexandre Oliva writes: > +@item -ftree-coalesce-inlined-vars > +Permit the copyrename pass to subject inlined variables to coalescing > +into other variables. This may harm debug information of such inlined > +variables, but it will keep variables of the main function apart from > +each other, such that they are more likely to contain the expected > +values in a debugging session. This option is enabled by default. > + > +@item -ftree-coalesce-vars > +Permit the copyrename pass to subject all variables to SSA coalescing. > +This may severely limit the ability to debug a program. In the negated > +form, this flag prevents SSA coalescing of user variables, including > +inlined ones. If we are going to have these options, the documentation needs to be better. You have written it from the compiler implementor's point of view. You need to rewrite the docs from the user's point of view: what are the user visible effects of these options? Also the option names are from the implementor's point of view rather than the user's point of view. No ordinary user will ever use an option named -ftree-coaelesce-inlined-vars, which raises the question of whether we need the option at all. Ian