From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 15021 invoked by alias); 25 Feb 2014 02:59:37 -0000 Mailing-List: contact crossgcc-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: crossgcc-owner@sourceware.org Received: (qmail 15006 invoked by uid 89); 25 Feb 2014 02:59:35 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.6 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.2 X-HELO: mout3.freenet.de Received: from mout3.freenet.de (HELO mout3.freenet.de) (195.4.92.93) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Tue, 25 Feb 2014 02:59:34 +0000 Received: from [195.4.92.140] (helo=mjail0.freenet.de) by mout3.freenet.de with esmtpa (ID ralf.corsepius@freenet.de) (port 25) (Exim 4.80.1 #4) id 1WI8F0-0002Bb-Dv for crossgcc@sourceware.org; Tue, 25 Feb 2014 03:59:30 +0100 Received: from localhost ([::1]:58151 helo=mjail0.freenet.de) by mjail0.freenet.de with esmtpa (ID ralf.corsepius@freenet.de) (Exim 4.80.1 #4) id 1WI8F0-00004t-8O for crossgcc@sourceware.org; Tue, 25 Feb 2014 03:59:30 +0100 Received: from mx14.freenet.de ([195.4.92.24]:47782) by mjail0.freenet.de with esmtpa (ID ralf.corsepius@freenet.de) (Exim 4.80.1 #4) id 1WI8CU-0007RX-QQ for crossgcc@sourceware.org; Tue, 25 Feb 2014 03:56:54 +0100 Received: from hsi-kbw-37-49-64-110.hsi14.kabel-badenwuerttemberg.de ([37.49.64.110]:54167 helo=[192.168.1.102]) by mx14.freenet.de with esmtpsa (ID ralf.corsepius@freenet.de) (TLSv1:DHE-RSA-AES128-SHA:128) (port 587) (Exim 4.80.1 #4) id 1WI8CU-0001LW-N6 for crossgcc@sourceware.org; Tue, 25 Feb 2014 03:56:54 +0100 Message-ID: <530C0675.4040005@rtems.org> Date: Tue, 25 Feb 2014 02:59:00 -0000 From: Ralf Corsepius User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: crossgcc@sourceware.org Subject: Re: 32-bit host vs 64-bit host References: In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Originated-At: 37.49.64.110!54167 X-SW-Source: 2014-02/txt/msg00061.txt.bz2 On 02/24/2014 10:26 PM, Grant Edwards wrote: > Let's say I build two copies of the "same" toolchain: one on a 32-bit > (i686) host and the other on a 64-bit (amd64) host: both are using the > same configuration, same sources files, for the same target (e.g. ARM). > > Would you expect the two toolchains to produce identical code when > given identical sources? Theoretically, yes. > Or are there certain optimizations or transformations that differ > depend on the _host_ machine word-size or architecture? Theoretically, this should not happen, but it's thinkable. What I've occasionally seen in the past, is bugs (not design limitations) related to using 32bit/64bit hosts (in GCC or binutils) showing effect on target binaries. However, these occasion were rare. > For example: for the past few years you've been building an embedded > linux linux system for an ARM9 target using a 32-bit hosted toolchain. > How much of a risk is there if you move development to a 64-bit host > and rebuild your toolchains as 64-bit apps? There is a risk, but it's fairly small. Negligible, IMHO, in comparison to other factors contributing to potential differences (Host-libraries, host-OS-toolchain bugs/incompatiblities, target-toolchain bugs, etc.). > [Yes, I know that if you have 32-bit compatibility libraries you can > continue to use the existing 32-bit toolchain binaries.] It you're really scared, this feature would enable you to check yourself. Build a 32bit and a 64bit-hosted toolchain, install them in parallel and compare the resulting target files. Ralf -- For unsubscribe information see http://sourceware.org/lists.html#faq