From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 16343 invoked by alias); 19 Aug 2010 18:18:20 -0000 Received: (qmail 16330 invoked by uid 22791); 19 Aug 2010 18:18:19 -0000 X-SWARE-Spam-Status: No, hits=-5.5 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_HI,SPF_HELO_PASS,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 19 Aug 2010 18:18:14 +0000 Received: from int-mx03.intmail.prod.int.phx2.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.16]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o7JII7Xd019635 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 19 Aug 2010 14:18:07 -0400 Received: from anchor.twiddle.home (ovpn-113-26.phx2.redhat.com [10.3.113.26]) by int-mx03.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o7JII6K9008820; Thu, 19 Aug 2010 14:18:06 -0400 Message-ID: <4C6D755E.9030903@redhat.com> Date: Thu, 19 Aug 2010 18:28:00 -0000 From: Richard Henderson User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.7) Gecko/20100720 Fedora/3.1.1-1.fc13 Thunderbird/3.1.1 MIME-Version: 1.0 To: Andrew Stubbs CC: gcc-patches@gcc.gnu.org Subject: Re: [PATCH 1/3] SH-2A FDPIC: New pattern: use_initial_val References: <4C6D56F2.3060204@codesourcery.com> In-Reply-To: <4C6D56F2.3060204@codesourcery.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit 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: 2010-08/txt/msg01490.txt.bz2 On 08/19/2010 09:08 AM, Andrew Stubbs wrote: > This patch creates a new instruction pattern "use_initial_val". > > The purpose of this patch is to allow late optimization passes to use > re-use existing pseudo-registers, even if the use of the register has > been optimized away in earlier passes. What is a target intended to do in this use_initial_val pattern? Looking forward to 3/3, it seems you emit a fancy USE insn, whose purpose appears to be simply to extend the lifetime of the pseudo, without actually using it in a specific pattern. Without looking deeper, it seems this is a mistake. Can you explain further when and why this is required? r~