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=-16.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 62572C43214 for ; Fri, 6 Aug 2021 19:53:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3D36E611B0 for ; Fri, 6 Aug 2021 19:53:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244133AbhHFTxU (ORCPT ); Fri, 6 Aug 2021 15:53:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:37184 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232086AbhHFTxT (ORCPT ); Fri, 6 Aug 2021 15:53:19 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6B09361050; Fri, 6 Aug 2021 19:52:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628279582; bh=BcLDKj7BNKRtjpjR5WcTLxkB9iMSb4PMd3ghgcahvXc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BVzg6QCVo4RumqCV4MtsueL+OHKlz8ZkExb9h5a2zbbm6visuE/f+XcBNWUj7BIcP 2qMMvGvBMnkHNbDqR7qWxBQimBsm1PFgPDrI3/xYckDEILuPZvalxOgWqHKW7vcTun zByk+jQCrO3YLut3VT0AbNbX4Xt8MAwp5i+w3pdlTFH7N1/fVUc/oREBsleEVP/6bU 3U7JuHQj4EHpQN6GVtxHmODxmnjX6CvRInqgZx4hZPrsZ/MuIbYxDAyAkAl06u5Wa+ 41bvylD8pQ4dXoaiTVBcbfwbwbTqy81yTYbSjcemD2fN99yGzafUOAc98k1wOwWiBr SbbhWhs9XLTKg== Date: Fri, 6 Aug 2021 12:52:56 -0700 From: Nathan Chancellor To: Nick Desaulniers Cc: Masahiro Yamada , Khem Raj , Matthew Wilcox , Michal Marek , Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , clang-built-linux@googlegroups.com, linux-kbuild@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Michael Ellerman , linuxppc-dev@lists.ozlabs.org, Heiko Carstens , Vasily Gorbik , Christian Borntraeger , linux-s390@vger.kernel.org Subject: Re: [PATCH v2] scripts/Makefile.clang: default to LLVM_IAS=1 Message-ID: References: <20210806172701.3993843-1-ndesaulniers@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210806172701.3993843-1-ndesaulniers@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 06, 2021 at 10:27:01AM -0700, 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. The powerpc and s390 folks have been testing with clang, I think they should have been on CC for this change (done now). > 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 > > Signed-off-by: Nick Desaulniers I am still not really sure how I feel about this. I would prefer not to break people's builds but I suppose this is inevitabile eventually. A little support matrix that I drafted up where based on ARCH and clang version for LLVM_IAS=1 support: | 10.x | 11.x | 12.x | 13.x | 14.x | ARCH=arm | NO | NO | NO | YES | YES | ARCH=arm64 | NO | YES | YES | YES | YES | ARCH=i386 | YES | YES | YES | YES | YES | ARCH=mips* | YES | YES | YES | YES | YES | ARCH=powerpc | NO | NO | NO | NO | NO | ARCH=s390 | NO | NO | NO | NO | NO | ARCH=x86_64 | NO | YES | YES | YES | YES | The main issue that I have with this change is that all of these architectures work fine with CC=clang and their build commands that used to work fine will not with this change, as they will have to specify LLVM_IAS=0. I think that making this change for LLVM=1 makes sense but changing the default for just CC=clang feels like a bit much at this point in time. I would love to hear from others on this though, I am not going to object much further than this. Regardless of that concern, this patch does what it says so: Reviewed-by: Nathan Chancellor > --- > Changes v1 -> v2: > * Drop "Currently" from Documentation/, as per Matthew. > * Drop Makefile and riscv Makefile, rebase on > https://lore.kernel.org/lkml/20210805150102.131008-1-masahiroy@kernel.org/ > as per Masahiro. > * Base is kbuild/for-next, plus > https://lore.kernel.org/lkml/20210802183910.1802120-1-ndesaulniers@google.com/ > https://lore.kernel.org/lkml/20210805150102.131008-1-masahiroy@kernel.org/. > > Documentation/kbuild/llvm.rst | 14 ++++++++------ > scripts/Makefile.clang | 6 +++--- > 2 files changed, 11 insertions(+), 9 deletions(-) > > diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst > index f8a360958f4c..e87ed5479963 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. > +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/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 > prerequisite-patch-id: 6a0342755115ec459610657edac1075f069faa3d > -- > 2.32.0.605.g8dce9f2422-goog > 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=-14.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, 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 43B4DC4320A for ; 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b=BVzg6QCVo4RumqCV4MtsueL+OHKlz8ZkExb9h5a2zbbm6visuE/f+XcBNWUj7BIcP 2qMMvGvBMnkHNbDqR7qWxBQimBsm1PFgPDrI3/xYckDEILuPZvalxOgWqHKW7vcTun zByk+jQCrO3YLut3VT0AbNbX4Xt8MAwp5i+w3pdlTFH7N1/fVUc/oREBsleEVP/6bU 3U7JuHQj4EHpQN6GVtxHmODxmnjX6CvRInqgZx4hZPrsZ/MuIbYxDAyAkAl06u5Wa+ 41bvylD8pQ4dXoaiTVBcbfwbwbTqy81yTYbSjcemD2fN99yGzafUOAc98k1wOwWiBr SbbhWhs9XLTKg== Date: Fri, 6 Aug 2021 12:52:56 -0700 From: Nathan Chancellor To: Nick Desaulniers Cc: Masahiro Yamada , Khem Raj , Matthew Wilcox , Michal Marek , Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , clang-built-linux@googlegroups.com, linux-kbuild@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Michael Ellerman , linuxppc-dev@lists.ozlabs.org, Heiko Carstens , Vasily Gorbik , Christian Borntraeger , linux-s390@vger.kernel.org Subject: Re: [PATCH v2] scripts/Makefile.clang: default to LLVM_IAS=1 Message-ID: References: <20210806172701.3993843-1-ndesaulniers@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210806172701.3993843-1-ndesaulniers@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210806_125303_537700_8322F9DD X-CRM114-Status: GOOD ( 30.14 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Fri, Aug 06, 2021 at 10:27:01AM -0700, 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. The powerpc and s390 folks have been testing with clang, I think they should have been on CC for this change (done now). > 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 > > Signed-off-by: Nick Desaulniers I am still not really sure how I feel about this. I would prefer not to break people's builds but I suppose this is inevitabile eventually. A little support matrix that I drafted up where based on ARCH and clang version for LLVM_IAS=1 support: | 10.x | 11.x | 12.x | 13.x | 14.x | ARCH=arm | NO | NO | NO | YES | YES | ARCH=arm64 | NO | YES | YES | YES | YES | ARCH=i386 | YES | YES | YES | YES | YES | ARCH=mips* | YES | YES | YES | YES | YES | ARCH=powerpc | NO | NO | NO | NO | NO | ARCH=s390 | NO | NO | NO | NO | NO | ARCH=x86_64 | NO | YES | YES | YES | YES | The main issue that I have with this change is that all of these architectures work fine with CC=clang and their build commands that used to work fine will not with this change, as they will have to specify LLVM_IAS=0. I think that making this change for LLVM=1 makes sense but changing the default for just CC=clang feels like a bit much at this point in time. I would love to hear from others on this though, I am not going to object much further than this. Regardless of that concern, this patch does what it says so: Reviewed-by: Nathan Chancellor > --- > Changes v1 -> v2: > * Drop "Currently" from Documentation/, as per Matthew. > * Drop Makefile and riscv Makefile, rebase on > https://lore.kernel.org/lkml/20210805150102.131008-1-masahiroy@kernel.org/ > as per Masahiro. > * Base is kbuild/for-next, plus > https://lore.kernel.org/lkml/20210802183910.1802120-1-ndesaulniers@google.com/ > https://lore.kernel.org/lkml/20210805150102.131008-1-masahiroy@kernel.org/. > > Documentation/kbuild/llvm.rst | 14 ++++++++------ > scripts/Makefile.clang | 6 +++--- > 2 files changed, 11 insertions(+), 9 deletions(-) > > diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst > index f8a360958f4c..e87ed5479963 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. > +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/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 > prerequisite-patch-id: 6a0342755115ec459610657edac1075f069faa3d > -- > 2.32.0.605.g8dce9f2422-goog > _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv 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=-13.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, 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 5CEA7C4338F for ; Fri, 6 Aug 2021 19:53:37 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 86E8A611C5 for ; Fri, 6 Aug 2021 19:53:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 86E8A611C5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4GhGPV6s7zz3dHJ for ; Sat, 7 Aug 2021 05:53:34 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=BVzg6QCV; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=198.145.29.99; helo=mail.kernel.org; envelope-from=nathan@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=BVzg6QCV; dkim-atps=neutral Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4GhGNy3T5yz30HN for ; Sat, 7 Aug 2021 05:53:06 +1000 (AEST) Received: by mail.kernel.org (Postfix) with ESMTPSA id 6B09361050; Fri, 6 Aug 2021 19:52:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628279582; bh=BcLDKj7BNKRtjpjR5WcTLxkB9iMSb4PMd3ghgcahvXc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BVzg6QCVo4RumqCV4MtsueL+OHKlz8ZkExb9h5a2zbbm6visuE/f+XcBNWUj7BIcP 2qMMvGvBMnkHNbDqR7qWxBQimBsm1PFgPDrI3/xYckDEILuPZvalxOgWqHKW7vcTun zByk+jQCrO3YLut3VT0AbNbX4Xt8MAwp5i+w3pdlTFH7N1/fVUc/oREBsleEVP/6bU 3U7JuHQj4EHpQN6GVtxHmODxmnjX6CvRInqgZx4hZPrsZ/MuIbYxDAyAkAl06u5Wa+ 41bvylD8pQ4dXoaiTVBcbfwbwbTqy81yTYbSjcemD2fN99yGzafUOAc98k1wOwWiBr SbbhWhs9XLTKg== Date: Fri, 6 Aug 2021 12:52:56 -0700 From: Nathan Chancellor To: Nick Desaulniers Subject: Re: [PATCH v2] scripts/Makefile.clang: default to LLVM_IAS=1 Message-ID: References: <20210806172701.3993843-1-ndesaulniers@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210806172701.3993843-1-ndesaulniers@google.com> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-s390@vger.kernel.org, Michal Marek , Vasily Gorbik , Jonathan Corbet , Masahiro Yamada , linux-kbuild@vger.kernel.org, linux-doc@vger.kernel.org, Khem Raj , Matthew Wilcox , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Christian Borntraeger , Albert Ou , Palmer Dabbelt , Paul Walmsley , linux-riscv@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, Heiko Carstens Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, Aug 06, 2021 at 10:27:01AM -0700, 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. The powerpc and s390 folks have been testing with clang, I think they should have been on CC for this change (done now). > 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 > > Signed-off-by: Nick Desaulniers I am still not really sure how I feel about this. I would prefer not to break people's builds but I suppose this is inevitabile eventually. A little support matrix that I drafted up where based on ARCH and clang version for LLVM_IAS=1 support: | 10.x | 11.x | 12.x | 13.x | 14.x | ARCH=arm | NO | NO | NO | YES | YES | ARCH=arm64 | NO | YES | YES | YES | YES | ARCH=i386 | YES | YES | YES | YES | YES | ARCH=mips* | YES | YES | YES | YES | YES | ARCH=powerpc | NO | NO | NO | NO | NO | ARCH=s390 | NO | NO | NO | NO | NO | ARCH=x86_64 | NO | YES | YES | YES | YES | The main issue that I have with this change is that all of these architectures work fine with CC=clang and their build commands that used to work fine will not with this change, as they will have to specify LLVM_IAS=0. I think that making this change for LLVM=1 makes sense but changing the default for just CC=clang feels like a bit much at this point in time. I would love to hear from others on this though, I am not going to object much further than this. Regardless of that concern, this patch does what it says so: Reviewed-by: Nathan Chancellor > --- > Changes v1 -> v2: > * Drop "Currently" from Documentation/, as per Matthew. > * Drop Makefile and riscv Makefile, rebase on > https://lore.kernel.org/lkml/20210805150102.131008-1-masahiroy@kernel.org/ > as per Masahiro. > * Base is kbuild/for-next, plus > https://lore.kernel.org/lkml/20210802183910.1802120-1-ndesaulniers@google.com/ > https://lore.kernel.org/lkml/20210805150102.131008-1-masahiroy@kernel.org/. > > Documentation/kbuild/llvm.rst | 14 ++++++++------ > scripts/Makefile.clang | 6 +++--- > 2 files changed, 11 insertions(+), 9 deletions(-) > > diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst > index f8a360958f4c..e87ed5479963 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. > +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/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 > prerequisite-patch-id: 6a0342755115ec459610657edac1075f069faa3d > -- > 2.32.0.605.g8dce9f2422-goog >