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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 CF773C43381 for ; Mon, 18 Mar 2019 20:44:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9314120872 for ; Mon, 18 Mar 2019 20:44:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="XkZcuK+T" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727532AbfCRUoh (ORCPT ); Mon, 18 Mar 2019 16:44:37 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:37987 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726980AbfCRUoh (ORCPT ); Mon, 18 Mar 2019 16:44:37 -0400 Received: by mail-pg1-f193.google.com with SMTP id v1so7501831pgi.5 for ; Mon, 18 Mar 2019 13:44:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=QEM+jCPNC49PZRZiVaqYm+WpQE4LEimTilZJ8sg1mCo=; b=XkZcuK+TrDAQ6JZobv7wI/S52f//O3rCkNQBr+RBTF5xqnDdvn/2hwqs6qMVXb1vQq qhC+CFKfYx2VlteH7Fzi66bY1+2YlWp0Ib/8SkvKNsmI9TZ+dEHWG7LnRwBLPCBLSuwi bVwVdWplrbzBfxEHKq6OEbdh5ZOQnCZif6LQg= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=QEM+jCPNC49PZRZiVaqYm+WpQE4LEimTilZJ8sg1mCo=; b=F00VGjwnsl2NWoaU0sEHf+iRV/gEBqTgr3RkNfDXiCRnpMCeBhdkAxxouo3QIJo7dR 4BmV0euf6pMgCVoJMDVdprulGA47kogWzu2IbdKgEMZW38GJQODHxaLKzVtBhGVW/0zI MekUWEu/ABfKt0GjF3mRlzF0roDJiptcVuzr7iBZOh/LRQJyLzESXg5TNxPnI0oQ6hGX pzpqTeL39NHZtFscAcJRjkb/rGi8RVecHGLsCRLCKwEChqLKXB+SYqckZF/LsSrDQAHK /YacO4FsjerII8aQ9OA99DYcwXNLDnmW0ql7NUx/w1WR3z74lYlydbQHuNa69lNy17vN ZxZw== X-Gm-Message-State: APjAAAW6t4i91VWVFALcrhp/96IHbJdAF4S+SFvC5EzUiZkUyHR6pMwu 29loedL8lLmJeMCjVgeSbP4LhQ== X-Google-Smtp-Source: APXvYqzyy50/RWGfFpYtsg/UBI40gLYbjjenhyM3c+gsa8SzTwXAnit8wTXUlP9dmbpKKVXjj0iM4w== X-Received: by 2002:aa7:8d01:: with SMTP id j1mr21567197pfe.122.1552941876424; Mon, 18 Mar 2019 13:44:36 -0700 (PDT) Received: from localhost ([2620:15c:202:1:75a:3f6e:21d:9374]) by smtp.gmail.com with ESMTPSA id e184sm16593470pfc.143.2019.03.18.13.44.35 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 18 Mar 2019 13:44:35 -0700 (PDT) Date: Mon, 18 Mar 2019 13:44:35 -0700 From: Matthias Kaehlcke To: Peter Zijlstra Cc: Nick Desaulniers , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , x86@kernel.org, LKML , Manoj Gupta , Tiancong Wang , Stephen Hines , clang-built-linux@googlegroups.com, Masahiro Yamada Subject: Re: [PATCH] x86/vdso: include generic __lshrdi3 in 32-bit vDSO Message-ID: <20190318204435.GH112750@google.com> References: <20190315222906.GC112750@google.com> <20190318171604.GU6058@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190318171604.GU6058@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, On Mon, Mar 18, 2019 at 06:16:04PM +0100, Peter Zijlstra wrote: > On Mon, Mar 18, 2019 at 10:09:37AM -0700, Nick Desaulniers wrote: > > On Fri, Mar 15, 2019 at 3:29 PM Matthias Kaehlcke wrote: > > > On Fri, Mar 15, 2019 at 02:31:09PM -0700, 'Nick Desaulniers' via Clang Built Linux wrote: > > > > Is there a config I can set to reproduce this, in order to help > > > > test? > > > > > > I encountered it with a Chrome OS specific configuration, but a > > > defconfig should do. > > > > defconfig selects CONFIG_OPTIMIZE_FOR_PERFORMANCE=y. I needed to > > select CONFIG_CC_OPTIMIZE_FOR_SIZE=y to repro. My CI is simply > > running defconfigs, which is why I didn't catch this. > > I suspect the right fix is to make clang use -Os and abolish that -Oz > madness. You have a point, enabling -Oz (aggressive optimization for size) doesn't seem a good choice for the entire kernel. I'll send a patch to change it (back) to -Os. Matthias