From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 8874 invoked by alias); 7 Dec 2003 17:14:55 -0000 Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org Received: (qmail 8867 invoked from network); 7 Dec 2003 17:14:54 -0000 Received: from unknown (HELO atrey.karlin.mff.cuni.cz) (195.113.31.123) by sources.redhat.com with SMTP; 7 Dec 2003 17:14:54 -0000 Received: by atrey.karlin.mff.cuni.cz (Postfix, from userid 29025) id 43CBE4C02D2; Sun, 7 Dec 2003 18:14:54 +0100 (CET) Date: Sun, 07 Dec 2003 17:28:00 -0000 From: Zdenek Dvorak To: Diego Novillo Cc: "gcc@gcc.gnu.org" Subject: Re: [tree-ssa] Lazy updating of stmt operands Message-ID: <20031207171454.GA12827@atrey.karlin.mff.cuni.cz> References: <20031207161929.GA10638@atrey.karlin.mff.cuni.cz> <1070816155.7334.13.camel@frodo.toronto.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1070816155.7334.13.camel@frodo.toronto.redhat.com> User-Agent: Mutt/1.5.4i X-SW-Source: 2003-12/txt/msg00472.txt.bz2 Hello, > > what is the purpose of having lists of stmt operands updated on demand? > > > Performance. If the statement hasn't changed, no point re-scanning it. right. But this would as well be the case if the information was always kept up-to-date. > > I thought that it is for performance reasons, but this seems not to be > > the case as all the statements are anyway scanned in the final dce pass, > > so they end up in updated forms and we cannot gain anything elsewhere. > > > The call to get_stmt_operands doesn't necessarily mean that the > statement will be re-scanned. > > > Why I am interested in this is that it prevents us from having also > > def-use edges (immediate uses) provided explicitly, which would be > > convenient in two cases I have encountered recently. > > > tree-dfa.c:compute_immediate_uses() Which needs to pass through every single statement in the program. Not really terribly efficient. Zdenek