linux-kernel - Re: [PATCH v2 2/2] kbuild: consolidate Clang compiler flags

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Date:   Fri, 9 Nov 2018 10:29:35 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Stefan Agner <stefan@...er.ch>,
        Matthias Kaehlcke <mka@...omium.org>, joel@....id.au,
        linuxppc-dev@...ts.ozlabs.org, mpe@...erman.id.au,
        Michal Marek <michal.lkml@...kovi.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>
Subject: Re: [PATCH v2 2/2] kbuild: consolidate Clang compiler flags

On Mon, Nov 5, 2018 at 7:05 PM Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
>
> Collect basic Clang options such as --target, --prefix, --gcc-toolchain,
> -no-integrated-as into a single variable CLANG_FLAGS so that it can be
> easily reused in other parts of Makefile.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
>
> Changes in v2:
>  - Use := flavor instead of = because $(CLANG_FLAGS) is expanded soon anyway
>
>  Makefile | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index da11700..e173a73 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -487,18 +487,17 @@ endif
>
>  ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),)
>  ifneq ($(CROSS_COMPILE),)
> -CLANG_TARGET   := --target=$(notdir $(CROSS_COMPILE:%-=%))
> +CLANG_FLAGS    := --target=$(notdir $(CROSS_COMPILE:%-=%))
>  GCC_TOOLCHAIN_DIR := $(dir $(shell which $(LD)))
> -CLANG_PREFIX   := --prefix=$(GCC_TOOLCHAIN_DIR)
> +CLANG_FLAGS    += --prefix=$(GCC_TOOLCHAIN_DIR)
>  GCC_TOOLCHAIN  := $(realpath $(GCC_TOOLCHAIN_DIR)/..)
>  endif
>  ifneq ($(GCC_TOOLCHAIN),)
> -CLANG_GCC_TC   := --gcc-toolchain=$(GCC_TOOLCHAIN)
> +CLANG_FLAGS    += --gcc-toolchain=$(GCC_TOOLCHAIN)
>  endif
> -KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) $(CLANG_PREFIX)
> -KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) $(CLANG_PREFIX)
> -KBUILD_CFLAGS += -no-integrated-as
> -KBUILD_AFLAGS += -no-integrated-as
> +CLANG_FLAGS    += -no-integrated-as
> +KBUILD_CFLAGS  += $(CLANG_FLAGS)
> +KBUILD_AFLAGS  += $(CLANG_FLAGS)
>  endif
>
>  RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register
> --
> 2.7.4
>

Thanks for this patch, Masahiro, it's a good simplification.
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>

Would you mind waiting for a tested-by from Stefan, and maybe an ack
from Greg (added to cc)?
-- 
Thanks,
~Nick Desaulniers