From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 113993 invoked by alias); 24 Jun 2019 12:12:30 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 113978 invoked by uid 89); 24 Jun 2019 12:12:30 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-4.2 required=5.0 tests=AWL,BAYES_00,SPF_PASS autolearn=ham version=3.3.1 spammy=H*i:sk:CAFiYyc, H*f:RSM3s, H*f:sk:DQ@mail, H*i:RSM3s X-HELO: mx1.suse.de Received: from mx2.suse.de (HELO mx1.suse.de) (195.135.220.15) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 24 Jun 2019 12:12:29 +0000 Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id AC2F5AEB3; Mon, 24 Jun 2019 12:12:26 +0000 (UTC) Subject: Re: [PATCH] Add .gnu.lto_.meta section. To: Richard Biener Cc: Jan Hubicka , Thomas Koenig , Andrew Pinski , Jeff Law , GCC Development , GCC Patches References: <20190619192954.edwdfxns3gx2gt5m@kam.mff.cuni.cz> <122f53d2-5ae0-b801-81ab-36ce69f9efda@netcologne.de> <9417a329-c71c-4682-872c-60ff3524c47e@suse.cz> <20190620120225.s7ouywid2mntmhlm@kam.mff.cuni.cz> <20190621125718.qv2m5iygqj2b43fe@kam.mff.cuni.cz> From: =?UTF-8?Q?Martin_Li=c5=a1ka?= Message-ID: <498ec44b-60ad-6f70-3c7a-b521f9fb6c56@suse.cz> Date: Mon, 24 Jun 2019 12:12:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-IsSubscribed: yes X-SW-Source: 2019-06/txt/msg01437.txt.bz2 On 6/24/19 2:02 PM, Richard Biener wrote: > On Fri, Jun 21, 2019 at 4:01 PM Martin Liška wrote: >> >> On 6/21/19 2:57 PM, Jan Hubicka wrote: >>> This looks like good step (and please stream it in host independent >>> way). I suppose all these issues can be done one-by-one. >> >> So there's a working patch for that. However one will see following errors >> when using an older compiler or older LTO bytecode: >> >> $ gcc main9.o -flto >> lto1: fatal error: bytecode stream in file ‘main9.o’ generated with LTO version -25480.4493 instead of the expected 9.0 >> >> $ gcc main.o >> lto1: internal compiler error: compressed stream: data error > > This is because of your change to bitfields or because with the old > scheme the header with the > version is compressed (is it?). Because currently also the header is compressed. > I'd simply avoid any layout changes > in the version check range. Well, then we have to find out how to distinguish between compression algorithms. > >> To be honest, I would prefer the new .gnu.lto_.meta section. >> Richi why is that so ugly? > > Because it's a change in the wrong direction and doesn't solve the > issue we already > have (cannot determine if a section is compressed or not). That's not true, the .gnu.lto_.meta section will be always uncompressed and we can also backport changes to older compiler that can read it and print a proper error message about LTO bytecode version mismatch. > ELF section overhead > is quite big if you have lots of small functions. My patch is actually shrinking space as I'm suggesting to add _one_ extra ELF section and remove the section header from all other LTO sections. That will save space for all function sections. Martin > > Richard. > >> >> Martin