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,URIBL_RED 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 D54D6C432BE for ; Thu, 5 Aug 2021 13:59:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B6BE36113B for ; Thu, 5 Aug 2021 13:59:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241414AbhHEN7r (ORCPT ); Thu, 5 Aug 2021 09:59:47 -0400 Received: from conssluserg-03.nifty.com ([210.131.2.82]:58446 "EHLO conssluserg-03.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240412AbhHEN7q (ORCPT ); Thu, 5 Aug 2021 09:59:46 -0400 Received: from mail-pj1-f52.google.com (mail-pj1-f52.google.com [209.85.216.52]) (authenticated) by conssluserg-03.nifty.com with ESMTP id 175DxJWi003798; Thu, 5 Aug 2021 22:59:20 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-03.nifty.com 175DxJWi003798 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1628171960; bh=MkSCffZ2FCUUtcooB4heJtTkmzuuejT3xGrOt7x1cAA=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=iCajhmo40OkihncfjVEtcet2ltpY21QoQoMe2glAN2eNHaze9sMggGWmI+Co24TuK SDrOczVHIkrYXfuqXa/X3zwecFVtSzOzrZoD5WAA0rwtSZHxoDpm+2Ts+7vZY/7SBT XSn24Kym+dkx5qvXsgP+ShwIjyMeNIrJDD2gW7L36XEcB6JxQajQcme5g7iGQgpp85 +MF7QYpe0eWrnuVt/dVelrA7nTWAwQv4bBrvKPfnpZIV2wYJIpfyQg0+WbfqOSaNg6 ObuRbdyl7SfJqeDBEypbHtgwPUlkg+no0sgBdDAgpzEa9420Ef4nZNyJwRq/9Z9TQt Io/zsuI3TGEfQ== X-Nifty-SrcIP: [209.85.216.52] Received: by mail-pj1-f52.google.com with SMTP id u13-20020a17090abb0db0290177e1d9b3f7so14998906pjr.1; Thu, 05 Aug 2021 06:59:20 -0700 (PDT) X-Gm-Message-State: AOAM531TZ2mqnBs33PdqABq80J/R034GXpi1RGWXvGgAxwVY2nqXN8iR /d1v6vgxK1Wnpk5KcRxp1QGQiL1WpEW7J46obYc= X-Google-Smtp-Source: ABdhPJxCsspIjv0BLuWLByxOzuSFxh1DUpAzcMHY2XGUempgsI0UeWvbevn5fwM0XLWpeN5CvxXCyLMYFkf5/ct/MeY= X-Received: by 2002:a62:8896:0:b029:3c3:7c34:6527 with SMTP id l144-20020a6288960000b02903c37c346527mr5225762pfd.80.1628171959400; Thu, 05 Aug 2021 06:59:19 -0700 (PDT) MIME-Version: 1.0 References: <20210802183910.1802120-1-ndesaulniers@google.com> <20210802183910.1802120-3-ndesaulniers@google.com> In-Reply-To: <20210802183910.1802120-3-ndesaulniers@google.com> From: Masahiro Yamada Date: Thu, 5 Aug 2021 22:58:42 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v6 2/3] Makefile: infer --target from ARCH for CC=clang To: Nick Desaulniers Cc: Miguel Ojeda , Fangrui Song , Michal Marek , Arnd Bergmann , Linux Kernel Mailing List , Linux Kbuild mailing list , clang-built-linux , Geert Uytterhoeven , Christoph Hellwig , Linus Torvalds , Nathan Chancellor 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 3:39 AM Nick Desaulniers wrote: > > We get constant feedback that the command line invocation of make is too > long when compiling with LLVM. CROSS_COMPILE is helpful when a toolchain > has a prefix of the target triple, or is an absolute path outside of > $PATH. > > Since a Clang binary is generally multi-targeted, we can infer a given > target from SRCARCH/ARCH. If CROSS_COMPILE is not set, simply set > --target= for CLANG_FLAGS, KBUILD_CFLAGS, and KBUILD_AFLAGS based on > $SRCARCH. > > Previously, we'd cross compile via: > $ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make LLVM=1 LLVM_IAS=1 > Now: > $ ARCH=arm64 make LLVM=1 LLVM_IAS=1 > > For native builds (not involving cross compilation) we now explicitly > specify a target triple rather than rely on the implicit host triple. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1399 > Suggested-by: Arnd Bergmann > Suggested-by: Linus Torvalds > Suggested-by: Masahiro Yamada > Suggested-by: Nathan Chancellor > Acked-by: Arnd Bergmann > Reviewed-by: Nathan Chancellor > Signed-off-by: Nick Desaulniers > --- > Changes v5 -> v6: > * Use indirection as per Linus. We now have CLANG_TARGET_FLAGS and a > few variables suffixed with $SRCARCH. > * Add Linus' SB tag. > * Change hexagon target triple from -gnu to -musl. > > Changes v3 -> v4: > * Reword commit message and oneline, as per Nathan. > * Drop documentation change (it's the next patch, could be squashed in, > I guess). > * Drop LLVM_IAS=1 requirement, as per Masahiro. > * Carry Arnd's and Nathan's AB/RB/TB tags, confirmed OK on IRC+Discord. > > Changes v2 -> v3: > * Drop check/requirement for LLVM=1, as per Masahiro. > * Change oneliner from LLVM=1 LLVM_IAS=1 to CC=clang LLVM_IAS=1. > * Don't carry forward Nathan's RB/TB tags. :( Sorry Nathan, but thank > you for testing+reviewing v2. > * Update wording of docs slightly. > > Changes v1 -> v2: > * Fix typos in commit message as per Geert and Masahiro. > * Use SRCARCH instead of ARCH, simplifying x86 handling, as per > Masahiro. Add his sugguested by tag. > * change commit oneline from 'drop' to 'infer.' > * Add detail about explicit host --target and relationship of ARCH to > SRCARCH, as per Masahiro. > > Changes RFC -> v1: > * Rebase onto linux-kbuild/for-next > * Keep full target triples since missing the gnueabi suffix messes up > 32b ARM. Drop Fangrui's sugguested by tag. Update commit message to > drop references to arm64. > * Flush out TODOS. > * Add note about -EL/-EB, -m32/-m64. > * Add note to Documentation/. > > scripts/Makefile.clang | 25 +++++++++++++++++++++++-- > 1 file changed, 23 insertions(+), 2 deletions(-) > > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang > index 297932e973d4..1f4e3eb70f88 100644 > --- a/scripts/Makefile.clang > +++ b/scripts/Makefile.clang > @@ -1,6 +1,27 @@ > -ifneq ($(CROSS_COMPILE),) > +# Individual arch/{arch}/Makefiles should use -EL/-EB to set intended > +# endianness and -m32/-m64 to set word size based on Kconfigs instead of > +# relying on the target triple. > +CLANG_TARGET_FLAGS_arm := arm-linux-gnueabi > +CLANG_TARGET_FLAGS_arm64 := aarch64-linux-gnu > +CLANG_TARGET_FLAGS_hexagon := hexagon-linux-musl > +CLANG_TARGET_FLAGS_m68k := m68k-linux-gnu > +CLANG_TARGET_FLAGS_mips := mipsel-linux-gnu > +CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu > +CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu > +CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu > +CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu > +CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH)) > + > +ifeq ($(CROSS_COMPILE),) > +ifeq ($(CLANG_TARGET_FLAGS),) > +$(error Specify CROSS_COMPILE or add '--target=' option to scripts/Makefile.clang) When I was browsing the code, I noticed a nit. I believe non-build targets such as 'make help', 'make clean' etc. should succeed without any correct CROSS_COMPILE set since they do not use the compiler at all. The remaining architectures may fail to clean. $ export LLVM=1 $ make ARCH=csky clean scripts/Makefile.clang:17: *** Specify CROSS_COMPILE or add '--target=' option to scripts/Makefile.clang. Stop. I decided to not be worried about it because it is fixable later. I will pick it up unless a significant issue is found. > +else > +CLANG_FLAGS += --target=$(CLANG_TARGET_FLAGS) > +endif # CLANG_TARGET_FLAGS > +else > CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > -endif > +endif # CROSS_COMPILE > + > ifeq ($(LLVM_IAS),1) > CLANG_FLAGS += -integrated-as > else > -- > 2.32.0.554.ge1b32706d8-goog > -- Best Regards Masahiro Yamada