From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 16227 invoked by alias); 20 Oct 2004 22:26:02 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 16179 invoked from network); 20 Oct 2004 22:26:00 -0000 Received: from unknown (HELO atrey.karlin.mff.cuni.cz) (195.113.31.123) by sourceware.org with SMTP; 20 Oct 2004 22:26:00 -0000 Received: by atrey.karlin.mff.cuni.cz (Postfix, from userid 29025) id DF5214B4525; Thu, 21 Oct 2004 00:25:59 +0200 (CEST) Date: Wed, 20 Oct 2004 22:54:00 -0000 From: Zdenek Dvorak To: Andrew MacLeod Cc: gcc-patches Subject: Re: [ssaupdate] Local dominance info Message-ID: <20041020222559.GA602@atrey.karlin.mff.cuni.cz> References: <20041019215129.GA29721@atrey.karlin.mff.cuni.cz> <1098279112.5695.3918.camel@pain> <20041020192719.GA20919@atrey.karlin.mff.cuni.cz> <1098310966.20227.24.camel@pain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1098310966.20227.24.camel@pain> User-Agent: Mutt/1.5.6i X-SW-Source: 2004-10/txt/msg01783.txt.bz2 Hello, > > > > this patch adds dominance information to statements, i.e. it makes it > > > > possible to decide whether a statement precedes other one inside a basic > > > > block without need to scan the whole block. > > > > > > > > To enable this, statements inside basic block are numbered (the > > > > numbering contains holes, so that new statements may be inserted). This > > > > seems to work good enough (no measurable impact on compile time). > > > > > > You want to keep and maintain this information all the time? > > > > yes. Given that it costs nothing, it seems to be the best choice to me. > > > > > This strikes me *much* more as a local thing that an individual pass > > > might be interested in, and so should number the stmt's itself for the > > > duration of its interest. > > > > Still you would need some mechanism to update things when statements are > > inserted, so this would make things only more complicated. > > and what wrong with the local_dom_insert_after() and > local_dom_insert_before() which call the bsi routines? It looks pretty > trivial to do that, then the info only exists and is maintained when > you want it. > > I don't see any reason why it should be kept up to date all the time > when virtually no-one else cares about it. now. I think this might be useful for SSA form updating (which is why I comitted this to the branch), in which case it will be useful on large number of places. > It seems like its a cheap to > calculate on the fly, and if its a big deal to you, then its not > difficult to keep up to date locally if you use local dominator aware > insert routines which call the BSI ones. I would tend agree with your argumentation if there were any problems (compile time or whatever) with the solution I am using now. There is not, so I do not see a reason why to change it to something more complicated. Zdenek