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Masahiro Yamada 5bcc7d3a32 BACKPORT: kbuild: support LLVM=1 to switch the default tools to Clang/LLVM ... commit a0d1c951ef08ed24f35129267e3595d86f57f5d3 upstream. As Documentation/kbuild/llvm.rst implies, building the kernel with a full set of LLVM tools gets very verbose and unwieldy. Provide a single switch LLVM=1 to use Clang and LLVM tools instead of GCC and Binutils. You can pass it from the command line or as an environment variable. Please note LLVM=1 does not turn on the integrated assembler. You need to pass LLVM_IAS=1 to use it. When the upstream kernel is ready for the integrated assembler, I think we can make it default. We discussed what we need, and we agreed to go with a simple boolean flag that switches both target and host tools: https://lkml.org/lkml/2020/3/28/494 https://lkml.org/lkml/2020/4/3/43 Some items discussed, but not adopted: - LLVM_DIR When multiple versions of LLVM are installed, I just thought supporting LLVM_DIR=/path/to/my/llvm/bin/ might be useful. CC = $(LLVM_DIR)clang LD = $(LLVM_DIR)ld.lld ... However, we can handle this by modifying PATH. So, we decided to not do this. - LLVM_SUFFIX Some distributions (e.g. Debian) package specific versions of LLVM with naming conventions that use the version as a suffix. CC = clang$(LLVM_SUFFIX) LD = ld.lld(LLVM_SUFFIX) ... will allow a user to pass LLVM_SUFFIX=-11 to use clang-11 etc., but the suffixed versions in /usr/bin/ are symlinks to binaries in /usr/lib/llvm-#/bin/, so this can also be handled by PATH. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Tested-by: Nathan Chancellor <natechancellor@gmail.com> # build Tested-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Change-Id: I8e0a6f5a8f240752e6f49b31d92669821a2d6e4a		2 years ago
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00-INDEX	Import A525FXXU3AUG4	3 years ago
Kconfig.recursion-issue-01	Import A525FXXU3AUG4	3 years ago
Kconfig.recursion-issue-02	Import A525FXXU3AUG4	3 years ago
Kconfig.select-break	Import A525FXXU3AUG4	3 years ago
headers_install.txt	Import A525FXXU3AUG4	3 years ago
kbuild.txt	BACKPORT: kbuild: support LLVM=1 to switch the default tools to Clang/LLVM	2 years ago
kconfig-language.txt	Import A525FXXU3AUG4	3 years ago
kconfig.txt	Import A525FXXU3AUG4	3 years ago
llvm.rst	BACKPORT: kbuild: support LLVM=1 to switch the default tools to Clang/LLVM	2 years ago
makefiles.txt	Import A525FXXU3AUG4	3 years ago
modules.txt	Import A525FXXU3AUG4	3 years ago