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Subject: Re: [PATCH v2 1/2] Makefile: move initial clang flag handling into
 scripts/Makefile.clang
To:     Nick Desaulniers <ndesaulniers@google.com>,
        Masahiro Yamada <masahiroy@kernel.org>
Cc:     Miguel Ojeda <ojeda@kernel.org>, Fangrui Song <maskray@google.com>,
        Michal Marek <michal.lkml@markovi.net>,
        Arnd Bergmann <arnd@kernel.org>, linux-kernel@vger.kernel.org,
        linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Christoph Hellwig <hch@infradead.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
References: <20210708232522.3118208-1-ndesaulniers@google.com>
 <20210708232522.3118208-2-ndesaulniers@google.com>
From:   Nathan Chancellor <nathan@kernel.org>
Message-ID: <9f66019d-6207-1d4b-0a80-30f09b819ff4@kernel.org>
Date:   Fri, 9 Jul 2021 13:12:08 -0700
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On 7/8/2021 4:25 PM, 'Nick Desaulniers' via Clang Built Linux 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/.
> 
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
>   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 81e1edeceae4..9c1205c258c7 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -4433,6 +4433,7 @@ 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 cbab0dc53065..010e3a4e770b 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
> +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
>