From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 110791 invoked by alias); 22 Jul 2019 14:31:53 -0000 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 Received: (qmail 110783 invoked by uid 89); 22 Jul 2019 14:31:52 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS autolearn=ham version=3.3.1 spammy=distributor, discussing, HX-Languages-Length:1433 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 22 Jul 2019 14:31:42 +0000 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0BA1B30BA078; Mon, 22 Jul 2019 14:31:41 +0000 (UTC) Received: from localhost.localdomain (ovpn-112-9.rdu2.redhat.com [10.10.112.9]) by smtp.corp.redhat.com (Postfix) with ESMTP id CCEEB60A9F; Mon, 22 Jul 2019 14:31:39 +0000 (UTC) Subject: Re: Can LTO minor version be updated in backward compatible way ? To: =?UTF-8?Q?Martin_Li=c5=a1ka?= , Andi Kleen , Romain Geissler Cc: gcc@gcc.gnu.org References: <87ftn4in6x.fsf@linux.intel.com> <71c86eab-4178-e841-f968-b4425f851dd3@redhat.com> <3535d8a9-8fed-baa9-be7e-9eecada5a9e8@suse.cz> From: Jeff Law Openpgp: preference=signencrypt Message-ID: <0c98ab44-fabd-fa46-267d-2710cbc21938@redhat.com> Date: Mon, 22 Jul 2019 14:31:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <3535d8a9-8fed-baa9-be7e-9eecada5a9e8@suse.cz> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-IsSubscribed: yes X-SW-Source: 2019-07/txt/msg00150.txt.bz2 On 7/22/19 8:25 AM, Martin Liška wrote: > On 7/17/19 8:10 PM, Jeff Law wrote: >> On 7/17/19 11:29 AM, Andi Kleen wrote: >>> Romain Geissler writes: >>>> >>>> I have no idea of the LTO format and if indeed it can easily be updated >>>> in a backward compatible way. But I would say it would be nice if it >>>> could, and would allow adoption for projects spread on many teams >>>> depending on each others and unable to re-build everything at each >>>> toolchain update. >>> >>> Right now any change to an compiler option breaks the LTO format >>> in subtle ways. In fact even the minor changes that are currently >>> done are not frequent enough to catch all such cases. >>> >>> So it's unlikely to really work. >> Right and stable LTO bytecode really isn't on the radar at this time. >> >> IMHO it's more important right now to start pushing LTO into the >> mainstream for the binaries shipped by the vendors (and stripping the >> LTO bits out of any static libraries/.o's shipped by the vendors). >> >> >> SuSE's announcement today is quite ironic. > > Why and what is ironic about it? Sorry, you'd have to have internal context -- we'd been discussing it within the Red Hat team for Fedora 32 the previous day. One of the questions that came up was whether or not any other major distributor was shipping with LTO enabled :-) Jeff