From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7ADEC433E2 for ; Thu, 10 Sep 2020 18:11:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E0FF207EA for ; Thu, 10 Sep 2020 18:11:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599761517; bh=+0kW6y6eIVbyH07Kmbn2O1HBfCtw/IaGgJ8BEPeDfi8=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=GqhpZI7OT7nw391vzYtdtepf8njpuv/8lASAJmMURF7laUvJZGXFo1p6aT0csV/Cj 4TBgyXn6pCErekaSVqydhP0npJ3/jrYQJHl2Mx0ZdsL1LzjnNZ0XOMnFHnj8rT5YW2 79/QduyESsijd1aZci2q17LWhW3CZkrsOiyJh5UY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726896AbgIJSLv (ORCPT ); Thu, 10 Sep 2020 14:11:51 -0400 Received: from conssluserg-02.nifty.com ([210.131.2.81]:44720 "EHLO conssluserg-02.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725807AbgIJSJl (ORCPT ); Thu, 10 Sep 2020 14:09:41 -0400 Received: from mail-pj1-f44.google.com (mail-pj1-f44.google.com [209.85.216.44]) (authenticated) by conssluserg-02.nifty.com with ESMTP id 08AI8SYc026504 for ; Fri, 11 Sep 2020 03:08:28 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-02.nifty.com 08AI8SYc026504 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1599761308; bh=vpW3QPcHXr6bjmCLt74cvbbZngeiHu+cInhD9vnp9CU=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=k4cPC+75bD8QxOzFwBtlF22o1MuucYq8hG2qjpMbr4Uaozob3CpxHw5T2tFu1u2iV SIs80qHbEE1rz0wRG8Hh9sN9qFeXw95OgbNTJzmZvd2biIPBr+AcdfkeUusW/lAvSW WR+VkkHG9xTbmkqJHNEEoacJF0H86hnpk89y1u8CZqfU8czQ0PXiqwPaLLoToK6idZ n4DdRnlqIn3dX8wSJdup4l6nGPrtkRWfio2a/IHQD+7a4fIQMD9zMyE/BxL4mpGmh7 80NtwpEOv5FjzQxB24h+ao5TUvyfgHX+alYS6GvPwn8lhA8pOo2Pn4KfRJavdSl4FN dDfERf0VooX/w== X-Nifty-SrcIP: [209.85.216.44] Received: by mail-pj1-f44.google.com with SMTP id u3so409768pjr.3 for ; Thu, 10 Sep 2020 11:08:28 -0700 (PDT) X-Gm-Message-State: AOAM533F/BZlVpgJUNu3O6QI1qPaXCiwi5x/C9SToAV3bwk4o5QJhOTN LKLLt0oKxNmuk/Z16gkjPWnM4X0oWt3osb1OuEM= X-Google-Smtp-Source: ABdhPJxCn359oZVq73QCn35/MyIufOYyLNeY6iVxRtS9FRAUrGy1w8LE6tH2u/r8M4SN6ydviNHbQfeb4pb6SoVext8= X-Received: by 2002:a17:902:ac8b:b029:d0:89f4:6220 with SMTP id h11-20020a170902ac8bb02900d089f46220mr6888021plr.8.1599761307850; Thu, 10 Sep 2020 11:08:27 -0700 (PDT) MIME-Version: 1.0 References: <20200624203200.78870-1-samitolvanen@google.com> <20200903203053.3411268-1-samitolvanen@google.com> In-Reply-To: From: Masahiro Yamada Date: Fri, 11 Sep 2020 03:07:49 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 00/28] Add support for Clang LTO To: Nick Desaulniers Cc: ian.bearman@microsoft.com, clang-built-linux , LKML , Sami Tolvanen Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 11, 2020 at 2:46 AM 'Nick Desaulniers' via Clang Built Linux wrote: > > Hey Ian, > It was nice to meet you at Linux plumbers. You might want to take a > look at this series. It implements builds of the Linux kernel with > LTO. It would be good to get eyes on it and help review it from folks > working on this from the GCC angle. The series has some configs that > split where Clang specific changes need to be made; it might be of > interest to think about what would the similar changes be needed for > GCC. Also, congrats on your LWN article! > https://lwn.net/Articles/830300/ FYI. Some people may remember GCC LTO was posted in 2014 (and rejected by Linus). https://lore.kernel.org/linux-kbuild/20140407201919.GA15838@sepie.suse.cz/ In my understanding, GCC LTO does not work for relocatable objects because GNU linker is agnostic about LTO. GCC LTO was implemented in the final link stage (i.e. vmlinux) by using $(CC) as a linker driver. On the other hand, Clang LTO, in this series implementation, works in the pre-mospost stage (i.e. vmlinux.o). -- Best Regards Masahiro Yamada