kbuild: replace AS=clang with LLVM_IAS=1
authorMasahiro Yamada <masahiroy@kernel.org>
Wed, 8 Apr 2020 01:36:22 +0000 (10:36 +0900)
committerMasahiro Yamada <masahiroy@kernel.org>
Wed, 8 Apr 2020 18:18:09 +0000 (03:18 +0900)
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>
Documentation/kbuild/llvm.rst
Makefile

index eefbdfa..4507085 100644 (file)
@@ -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
 ------------
 
index 1b26910..a2aadcf 100644 (file)
--- 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