From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 14994 invoked by alias); 4 Jun 2009 20:49:44 -0000 Received: (qmail 14986 invoked by uid 22791); 4 Jun 2009 20:49:43 -0000 X-SWARE-Spam-Status: No, hits=-1.9 required=5.0 tests=AWL,BAYES_00,SPF_FAIL X-Spam-Check-By: sourceware.org Received: from mx20.gnu.org (HELO mx20.gnu.org) (199.232.41.8) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 04 Jun 2009 20:49:37 +0000 Received: from mail.codesourcery.com ([65.74.133.4]) by mx20.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MCJsU-0001Y4-QG for gcc@gcc.gnu.org; Thu, 04 Jun 2009 16:49:35 -0400 Received: (qmail 23245 invoked from network); 4 Jun 2009 20:49:33 -0000 Received: from unknown (HELO digraph.polyomino.org.uk) (joseph@127.0.0.2) by mail.codesourcery.com with ESMTPA; 4 Jun 2009 20:49:33 -0000 Received: from jsm28 (helo=localhost) by digraph.polyomino.org.uk with local-esmtp (Exim 4.69) (envelope-from ) id 1MCJsR-0003Ik-VY; Thu, 04 Jun 2009 20:49:31 +0000 Date: Thu, 04 Jun 2009 20:49:00 -0000 From: "Joseph S. Myers" To: Adam Nemet cc: gcc@gcc.gnu.org Subject: Re: STRIP_NOPS and lower-precision/bit-field types In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Detected-Operating-System: by mx20.gnu.org: GNU/Linux 2.6, seldom 2.4 (older, 4) Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org X-SW-Source: 2009-06/txt/msg00073.txt.bz2 On Thu, 4 Jun 2009, Adam Nemet wrote: > 1. Change STRIP_NOPS not to remove the cast if it's changing the precision > (not just when it changes machine modes). And then audit code quality where > we need to and are allowed to look through these casts. As I said in and , I think such references to the mode are as a proxy for precision and machine modes are an inappropriate level of abstraction for the tree optimizers. So I favour checking for precision here - but I also favour having a good look at anything using STRIP_NOPS etc. and considering whether it should use some better defined function for removing redundant conversions instead. -- Joseph S. Myers joseph@codesourcery.com