From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 10697 invoked by alias); 19 Jan 2004 18:09:29 -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 10641 invoked from network); 19 Jan 2004 18:09:28 -0000 Received: from unknown (HELO nile.gnat.com) (205.232.38.5) by sources.redhat.com with SMTP; 19 Jan 2004 18:09:28 -0000 Received: from [205.232.38.124] (potomac.gnat.com [205.232.38.124]) by nile.gnat.com (Postfix) with ESMTP id B2791F29F2; Mon, 19 Jan 2004 13:09:27 -0500 (EST) In-Reply-To: <1074534670.25137.101.camel@frodo.toronto.redhat.com> References: <10401191226.AA27734@vlsi1.ultra.nyu.edu> <1074516514.5368.191.camel@frodo.toronto.redhat.com> <1074534670.25137.101.camel@frodo.toronto.redhat.com> Mime-Version: 1.0 (Apple Message framework v609) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: Content-Transfer-Encoding: 7bit Cc: Jan Hubicka , "gcc@gcc.gnu.org" , Richard Kenner From: Geert Bosch Subject: Re: [RFC] Contributing tree-ssa to mainline Date: Mon, 19 Jan 2004 18:09:00 -0000 To: Diego Novillo X-SW-Source: 2004-01/txt/msg01331.txt.bz2 On Jan 19, 2004, at 12:51, Diego Novillo wrote: > Instead of emitting runtime calls, would it be possible to emit tree > codes with well defined semantics? On finding them, the optimizers > would know that it's not just an arbitrary function call for instance > (perhaps adding attributes to the libcall). > > But I'm oversimplifying. We would have to talk about specific cases. There are definitely cases where we should do this. For example, for overflow checks in integer addition and multiplication, we now use a wider type for the arithmetic (or library routines for wide types) and check the result against bounds. Having tree codes with language-defined overflow semantics would allow the back end to expand to proper instructions with trap-on-overflow or jump on condition code. How does Java deal with this issue? -Geert