linux-kernel - Re: [PATCH v6 1/3] Makefile: move initial clang flag handling into scripts/Makefile.clang

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Date:   Mon, 2 Aug 2021 14:06:13 -0700
From:   Fāng-ruì Sòng <maskray@...gle.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Arnd Bergmann <arnd@...nel.org>, linux-kernel@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Christoph Hellwig <hch@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Nathan Chancellor <nathan@...nel.org>
Subject: Re: [PATCH v6 1/3] Makefile: move initial clang flag handling into scripts/Makefile.clang

On Mon, Aug 2, 2021 at 11:39 AM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> With some of the changes we'd like to make to CROSS_COMPILE, the initial
> block of clang flag handling which controls things like the target triple,
> whether or not to use the integrated assembler and how to find GAS,
> and erroring on unknown warnings is becoming unwieldy. Move it into its
> own file under scripts/.
>
> Reviewed-by: Nathan Chancellor <nathan@...nel.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
>  MAINTAINERS            |  1 +
>  Makefile               | 15 +--------------
>  scripts/Makefile.clang | 14 ++++++++++++++
>  3 files changed, 16 insertions(+), 14 deletions(-)
>  create mode 100644 scripts/Makefile.clang
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 19135a9d778e..3af8d39f43ef 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -4501,6 +4501,7 @@ B:        https://github.com/ClangBuiltLinux/linux/issues
>  C:     irc://chat.freenode.net/clangbuiltlinux
>  F:     Documentation/kbuild/llvm.rst
>  F:     include/linux/compiler-clang.h
> +F:     scripts/Makefile.clang
>  F:     scripts/clang-tools/
>  K:     \b(?i:clang|llvm)\b
>
> diff --git a/Makefile b/Makefile
> index 6b555f64df06..444558e62cbc 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -586,20 +586,7 @@ endif
>  CC_VERSION_TEXT = $(subst $(pound),,$(shell $(CC) --version 2>/dev/null | head -n 1))
>
>  ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
> -ifneq ($(CROSS_COMPILE),)
> -CLANG_FLAGS    += --target=$(notdir $(CROSS_COMPILE:%-=%))
> -endif
> -ifeq ($(LLVM_IAS),1)
> -CLANG_FLAGS    += -integrated-as
> -else
> -CLANG_FLAGS    += -no-integrated-as
> -GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
> -CLANG_FLAGS    += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
> -endif
> -CLANG_FLAGS    += -Werror=unknown-warning-option
> -KBUILD_CFLAGS  += $(CLANG_FLAGS)
> -KBUILD_AFLAGS  += $(CLANG_FLAGS)
> -export CLANG_FLAGS
> +include $(srctree)/scripts/Makefile.clang
>  endif
>
>  # Include this also for config targets because some architectures need
> diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
> new file mode 100644
> index 000000000000..297932e973d4
> --- /dev/null
> +++ b/scripts/Makefile.clang
> @@ -0,0 +1,14 @@
> +ifneq ($(CROSS_COMPILE),)
> +CLANG_FLAGS    += --target=$(notdir $(CROSS_COMPILE:%-=%))
> +endif
> +ifeq ($(LLVM_IAS),1)
> +CLANG_FLAGS    += -integrated-as

-i* options are for includes. -fintegrated-as is the canonical spelling.
Since -fintegrated-as is the default (for most llvm/lib/Target/
targets and the ones clang builds actually support),
it can even be deleted.

> +else
> +CLANG_FLAGS    += -no-integrated-as
> +GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
> +CLANG_FLAGS    += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
> +endif
> +CLANG_FLAGS    += -Werror=unknown-warning-option
> +KBUILD_CFLAGS  += $(CLANG_FLAGS)
> +KBUILD_AFLAGS  += $(CLANG_FLAGS)
> +export CLANG_FLAGS
> --
> 2.32.0.554.ge1b32706d8-goog
>