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Subject[PATCH v3 1/2] kbuild: replace AS=clang with LLVM_IAS=1
Date
The 'AS' variable is unused for building the kernel. Only the remaining
usage is to turn on the integrated assembler. A boolean flag is a better
fit for this purpose.

AS=clang was added for experts. So, I replaced it with LLVM_IAS=1,
breaking the backward compatibility.

Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---

Changes in v3:
- rename LLVM_IA to LLVM_IAS (per Fangrui Song)

Changes in v2:
- new patch

Documentation/kbuild/llvm.rst | 5 ++++-
Makefile | 2 +-
2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst
index eefbdfa3e4d9..0fefdf1737e9 100644
--- a/Documentation/kbuild/llvm.rst
+++ b/Documentation/kbuild/llvm.rst
@@ -50,11 +50,14 @@ LLVM Utilities
LLVM has substitutes for GNU binutils utilities. These can be invoked as
additional parameters to `make`.

- make CC=clang AS=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\
+ make CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\
OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-size \\
READELF=llvm-readelf HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar \\
HOSTLD=ld.lld

+Currently, the integrated assembler is disabled by default. You can pass
+LLVM_IAS=1 to enable it.
+
Getting Help
------------

diff --git a/Makefile b/Makefile
index 1b2691057cb5..a2aadcf8a36c 100644
--- a/Makefile
+++ b/Makefile
@@ -538,7 +538,7 @@ endif
ifneq ($(GCC_TOOLCHAIN),)
CLANG_FLAGS += --gcc-toolchain=$(GCC_TOOLCHAIN)
endif
-ifeq ($(if $(AS),$(shell $(AS) --version 2>&1 | head -n 1 | grep clang)),)
+ifneq ($(LLVM_IAS),1)
CLANG_FLAGS += -no-integrated-as
endif
CLANG_FLAGS += -Werror=unknown-warning-option
--
2.17.1
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