From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17356 invoked by alias); 30 Aug 2004 01:12:06 -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 17349 invoked from network); 30 Aug 2004 01:12:05 -0000 Received: from unknown (HELO mail.codesourcery.com) (65.74.133.10) by sourceware.org with SMTP; 30 Aug 2004 01:12:05 -0000 Received: (qmail 7119 invoked from network); 30 Aug 2004 01:12:04 -0000 Received: from localhost (HELO ?192.168.0.105?) (mitchell@127.0.0.1) by mail.codesourcery.com with SMTP; 30 Aug 2004 01:12:05 -0000 Message-ID: <41327EE6.4010300@codesourcery.com> Date: Mon, 30 Aug 2004 01:53:00 -0000 From: Mark Mitchell Organization: CodeSourcery, LLC User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7) Gecko/20040616 MIME-Version: 1.0 To: Daniel Berlin CC: Steven Bosscher , gcc@gcc.gnu.org Subject: Re: GCC 3.5 Status (2004-08-29) References: <4132641E.3030206@codesourcery.com> <200408300148.54421.stevenb@suse.de> <41326EBF.9020501@codesourcery.com> <200408300229.13652.stevenb@suse.de> <1093827433.29639.20.camel@dberlin.org> In-Reply-To: <1093827433.29639.20.camel@dberlin.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-SW-Source: 2004-08/txt/msg01435.txt.bz2 Daniel Berlin wrote: >>> I am confident that there >>>are alternatives that, while perhaps less comprehensive, get enough of >>>the common cases to achieve most of the benefits. >>> >>> >>What is your confidence based on? What common cases? Did Dan tell you >>about the issues that he's fighting? No "less comprehensive" solution >>exists that will not run into the exact same problems. >> >> >> > >I didn't tell him about the issues i'm fighting, so he's probably just >stating the typical result, ie "It takes less time to get the common >cases than it does to get all the cases". > >Of course, the issues i'm dealing with are things that were punted on >earlier in the design of tree-ssa, because they were either hard to get >right, we didn't have time then, etc. > >Let me give an example issue from an email i sent to diego and richard, >as a motivating example. > > Yes, there's some design work to be done. That's why I believed your estimate about how long it will take, and why parallelizing the work will only help so much: you still have to agree on a design up front. I still think there are likely to be expedient hacks that get you a lot of the win. Note that the RTL optimizers didn't know about fields at all until recently (3.4?). So, perhaps we can deal with the compile-time issue by accepting somewhat inferior generated code. Perhaps you can wait until SRA runs, and then just DTRT for objects that get SRA'd. I don't have the answer; I'm just saying that there's likely to be one out there somewhere. GCC got by for years with exactly this kind of solution, and actually managed to generate relatively decent code relatively often. -- Mark Mitchell CodeSourcery, LLC (916) 791-8304 mark@codesourcery.com