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=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 B2426C04A6B for ; Mon, 13 May 2019 02:24:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8057620C01 for ; Mon, 13 May 2019 02:24:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nifty.com header.i=@nifty.com header.b="SYFYhFdB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727404AbfEMCYc (ORCPT ); Sun, 12 May 2019 22:24:32 -0400 Received: from conssluserg-01.nifty.com ([210.131.2.80]:27992 "EHLO conssluserg-01.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727054AbfEMCYc (ORCPT ); Sun, 12 May 2019 22:24:32 -0400 Received: from mail-ua1-f43.google.com (mail-ua1-f43.google.com [209.85.222.43]) (authenticated) by conssluserg-01.nifty.com with ESMTP id x4D2ORAM010526; Mon, 13 May 2019 11:24:27 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-01.nifty.com x4D2ORAM010526 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1557714268; bh=EjdlPoSEz//GSOzFbKG40Hv0vI25bYnqXLD2D/sxgIU=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=SYFYhFdBXDv+jwms5kpIy7Ezs5LGXwoQXyPhL2Ht/TI3udC7OcCqENtR+OKpwfKv/ /mdPuPtrKN5wBN1iLUpaGzA1JVhNTrKWMDvZBa/lTs1lDq++m0YVuYty68jqYh4wtV Fta7ATCv5LSiMgihsQegd/Qw61EzSgDTTo3eaI0dgr/xY5BjIvgkIKT6VfWy2Ymt7q Wt4NOsfFrOyplI1DF7UKYBzQypjWWIh8mB36NvQ8C7yKbaRkz99zQYMId2dvNHdHKh U8+WQ58sszbrzeJcQ0f2246ACOfbosmmQtrFsK53f8Q3/4QpY/htOqXbbKwYrqQSEV ZPJOGDnkH9YZQ== X-Nifty-SrcIP: [209.85.222.43] Received: by mail-ua1-f43.google.com with SMTP id s30so4212654uas.8; Sun, 12 May 2019 19:24:27 -0700 (PDT) X-Gm-Message-State: APjAAAVGI7vIr+UVU4SVCOVC1+8quejwVwXiFZTjD2tTydhmK2tiYq87 rfAEBsmFJ/TbgtNTgUQxpN5/NdXMk9ngm8hl7p4= X-Google-Smtp-Source: APXvYqzRqZvOMRNJIsSJC6YBJA5OafXqidmDyHeDPeNQ53TrOpcHDAYCYUlDWNPXg3pPtH1TcQa5AOIMR3fXD2M0+G4= X-Received: by 2002:ab0:3058:: with SMTP id x24mr9143479ual.95.1557714266828; Sun, 12 May 2019 19:24:26 -0700 (PDT) MIME-Version: 1.0 References: <20190509064635.1445-1-yamada.masahiro@socionext.com> In-Reply-To: From: Masahiro Yamada Date: Mon, 13 May 2019 11:23:51 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] kbuild: add some extra warning flags unconditionally To: Nick Desaulniers Cc: Sedat Dilek , Linux Kbuild mailing list , Nathan Chancellor , Arnd Bergmann , Clang-Built-Linux ML , Michal Marek , Linux Kernel Mailing List , chromeos-toolchain , Android-LLVM 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, May 10, 2019 at 1:47 AM Nick Desaulniers wrote: > > From: Masahiro Yamada > > On Thu, May 9, 2019 at 4:11 PM Sedat Dilek wrote: > > > BTW, is this a speedup when doing CC/LD FLAGS etc checks unconditionally? > > > > Yes. > > cc-option is somewhat costly because it invoked the compiler to > > check if the given flag is supported. > > > > So, I want to get rid of as many cc-option calls as possible. > > > > > > > Asking in general - do you have any numbers :-)? > > > > Removing a couple of cc-options does not make > > a measurable difference in general use-cases. > > > > But, this might be more beneficial for chrome OS > > because $(CC) is a wrapper and invoking it is much more expensive. > > Android does too, which we plan on removing as we recently measured > the performance cost of 5% for having a Python wrapper to aid in > bisection. > > Anyways, I checked these options with clang 4 and gcc 4.6.4 in godbolt. > Tested-by: Nick Desaulniers > -- > Thanks, > ~Nick Desaulniers Applied to linux-kbuild. -- Best Regards Masahiro Yamada