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=-19.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 20374C432BE for ; Thu, 5 Aug 2021 15:16:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBCDC6104F for ; Thu, 5 Aug 2021 15:16:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241901AbhHEPQl (ORCPT ); Thu, 5 Aug 2021 11:16:41 -0400 Received: from conssluserg-02.nifty.com ([210.131.2.81]:37685 "EHLO conssluserg-02.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241095AbhHEPQj (ORCPT ); Thu, 5 Aug 2021 11:16:39 -0400 Received: from mail-pj1-f42.google.com (mail-pj1-f42.google.com [209.85.216.42]) (authenticated) by conssluserg-02.nifty.com with ESMTP id 175FG7g9008798; Fri, 6 Aug 2021 00:16:07 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-02.nifty.com 175FG7g9008798 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1628176567; bh=7JKVqdhk3wDgxUpgLrRBBJjC3akBTBo6VvDVu+02hPk=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=NbSRuTWtsSoUCcitllxBuHGpjcs6wQH82TDnRhc4ee4feibkzphqAG4g+oz9wjs19 yXGbH+/lxlX7LcVj5qD7PWjOPp8SPSS6atZ8zwE12jPRB6cm4JDSFjJ+bnJf7n8NJL CfPdjzGZYmpx0Hh3Q7/oNswTtpy4pl0PsqJLrg09ug/7l02k8nv8Mf3Zrg7DQPPc8Y n3/y1P0QDDGu8KvDSgZ1jbXm9MHjLntCJ17k3YvjJhglCGn/5Fa4dqTKNxgacm5M+Q 7BIN9NiNf9xU5fzZfK1SHHDiegYxKoWYCJDhvFzOuN0m/gltYCaCZv07fitMGNw9m7 mcZqmH64jgqnA== X-Nifty-SrcIP: [209.85.216.42] Received: by mail-pj1-f42.google.com with SMTP id j1so9599388pjv.3; Thu, 05 Aug 2021 08:16:07 -0700 (PDT) X-Gm-Message-State: AOAM531dgxOuAZtb8QEiiCio9XNOyzfdAUe+/GLXFAjwJT8KW5MGt/8g 3/Gdc+YGPoHxPxlU+qHumVLPVtXhuhTs+L7Kw7k= X-Google-Smtp-Source: ABdhPJwrhP5GxxiXyQoPTJ4HbkL2DpweB++rWVgwsahs6nVzqpqSNzY6uS/hh/EvSpVap/wB8NFnoDkci8pzupkBsb8= X-Received: by 2002:a63:1b5c:: with SMTP id b28mr203382pgm.175.1628176566664; Thu, 05 Aug 2021 08:16:06 -0700 (PDT) MIME-Version: 1.0 References: <20210802234304.3519577-1-ndesaulniers@google.com> In-Reply-To: <20210802234304.3519577-1-ndesaulniers@google.com> From: Masahiro Yamada Date: Fri, 6 Aug 2021 00:15:29 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] scripts/Makefile.clang: default to LLVM_IAS=1 To: Nick Desaulniers Cc: Nathan Chancellor , Khem Raj , Michal Marek , Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , clang-built-linux , Linux Kbuild mailing list , "open list:DOCUMENTATION" , Linux Kernel Mailing List , "open list:SIFIVE DRIVERS" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 3, 2021 at 8:43 AM Nick Desaulniers wrote: > > LLVM_IAS=1 controls enabling clang's integrated assembler via > -integrated-as. This was an explicit opt in until we could enable > assembler support in Clang for more architecures. Now we have support > and CI coverage of LLVM_IAS=1 for all architecures except a few more > bugs affecting s390 and powerpc. > > This commit flips the default from opt in via LLVM_IAS=1 to opt out via > LLVM_IAS=0. CI systems or developers that were previously doing builds > with CC=clang or LLVM=1 without explicitly setting LLVM_IAS must now > explicitly opt out via LLVM_IAS=0, otherwise they will be implicitly > opted-in. > > This finally shortens the command line invocation when cross compiling > with LLVM to simply: > > $ make ARCH=arm64 LLVM=1 > > Link: https://github.com/ClangBuiltLinux/linux/issues/1434 > Signed-off-by: Nick Desaulniers > --- > Note: base is: > https://lore.kernel.org/lkml/20210802183910.1802120-1-ndesaulniers@google.com/ > > Documentation/kbuild/llvm.rst | 14 ++++++++------ > Makefile | 2 +- > arch/riscv/Makefile | 2 +- > scripts/Makefile.clang | 6 +++--- > 4 files changed, 13 insertions(+), 11 deletions(-) > > diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst > index f8a360958f4c..16712fab4d3a 100644 > --- a/Documentation/kbuild/llvm.rst > +++ b/Documentation/kbuild/llvm.rst > @@ -60,17 +60,14 @@ They can be enabled individually. The full list of the parameters: :: > OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump READELF=llvm-readelf \ > HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar HOSTLD=ld.lld > > -Currently, the integrated assembler is disabled by default. You can pass > -``LLVM_IAS=1`` to enable it. > +Currently, the integrated assembler is enabled by default. You can pass > +``LLVM_IAS=0`` to disable it. > > Omitting CROSS_COMPILE > ---------------------- > > As explained above, ``CROSS_COMPILE`` is used to set ``--target=``. > > -Unless ``LLVM_IAS=1`` is specified, ``CROSS_COMPILE`` is also used to derive > -``--prefix=`` to search for the GNU assembler and linker. > - > If ``CROSS_COMPILE`` is not specified, the ``--target=`` is inferred > from ``ARCH``. > > @@ -78,7 +75,12 @@ That means if you use only LLVM tools, ``CROSS_COMPILE`` becomes unnecessary. > > For example, to cross-compile the arm64 kernel:: > > - make ARCH=arm64 LLVM=1 LLVM_IAS=1 > + make ARCH=arm64 LLVM=1 > + > +If ``LLVM_IAS=0`` is specified, ``CROSS_COMPILE`` is also used to derive > +``--prefix=`` to search for the GNU assembler and linker. :: > + > + make ARCH=arm64 LLVM=1 LLVM_IAS=0 CROSS_COMPILE=aarch64-linux-gnu- > > Supported Architectures > ----------------------- > diff --git a/Makefile b/Makefile > index 444558e62cbc..b24b48c9ebb7 100644 > --- a/Makefile > +++ b/Makefile > @@ -845,7 +845,7 @@ else > DEBUG_CFLAGS += -g > endif > > -ifneq ($(LLVM_IAS),1) > +ifeq ($(LLVM_IAS),0) > KBUILD_AFLAGS += -Wa,-gdwarf-2 > endif > > diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile > index bc74afdbf31e..807f7c94bc6f 100644 > --- a/arch/riscv/Makefile > +++ b/arch/riscv/Makefile > @@ -41,7 +41,7 @@ endif > ifeq ($(CONFIG_LD_IS_LLD),y) > KBUILD_CFLAGS += -mno-relax > KBUILD_AFLAGS += -mno-relax > -ifneq ($(LLVM_IAS),1) > +ifeq ($(LLVM_IAS),0) > KBUILD_CFLAGS += -Wa,-mno-relax > KBUILD_AFLAGS += -Wa,-mno-relax > endif Please drop these two hunks. I will apply my patch instead. https://lore.kernel.org/patchwork/patch/1472580/ > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang > index 1f4e3eb70f88..3ae63bd35582 100644 > --- a/scripts/Makefile.clang > +++ b/scripts/Makefile.clang > @@ -22,12 +22,12 @@ else > CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > endif # CROSS_COMPILE > > -ifeq ($(LLVM_IAS),1) > -CLANG_FLAGS += -integrated-as > -else > +ifeq ($(LLVM_IAS),0) > CLANG_FLAGS += -no-integrated-as > GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit)) > CLANG_FLAGS += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE)) > +else > +CLANG_FLAGS += -integrated-as > endif > CLANG_FLAGS += -Werror=unknown-warning-option > KBUILD_CFLAGS += $(CLANG_FLAGS) > > base-commit: d7a86429dbc691bf540688fcc8542cc20246a85b > prerequisite-patch-id: 0d3072ecb5fd06ff6fd6ea81fe601f6c54c23910 > prerequisite-patch-id: 2654829756eb8a094a0ffad1679caa75a4d86619 > prerequisite-patch-id: a51e7885ca2376d008bbf146a5589da247806f7b > -- > 2.32.0.554.ge1b32706d8-goog > When we negate a flag that is enabled by default, which is a common way? - set it to '0' - set is to empty So, I was wondering if we should support not only LLVM_IAS=0 but also LLVM_IAS=. What do you think? -- Best Regards Masahiro Yamada