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authorNick Desaulniers <ndesaulniers@google.com>2021-08-06 10:27:01 -0700
committerMasahiro Yamada <masahiroy@kernel.org>2021-08-10 09:13:25 +0900
commitf12b034afeb3a977bbb1c6584dedc0f3dc666f14 (patch)
tree3f3a5d488e333bbde7c8b8a00caf05aad1163fb0 /Documentation/kbuild
parent52cc02b910284d6bddba46cce402044ab775f314 (diff)
scripts/Makefile.clang: default to LLVM_IAS=1
LLVM_IAS=1 controls enabling clang's integrated assembler via -integrated-as. This was an explicit opt in until we could enable assembler support in Clang for more architecures. Now we have support and CI coverage of LLVM_IAS=1 for all architecures except a few more bugs affecting s390 and powerpc. This commit flips the default from opt in via LLVM_IAS=1 to opt out via LLVM_IAS=0. CI systems or developers that were previously doing builds with CC=clang or LLVM=1 without explicitly setting LLVM_IAS must now explicitly opt out via LLVM_IAS=0, otherwise they will be implicitly opted-in. This finally shortens the command line invocation when cross compiling with LLVM to simply: $ make ARCH=arm64 LLVM=1 Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'Documentation/kbuild')
-rw-r--r--Documentation/kbuild/llvm.rst14
1 files changed, 8 insertions, 6 deletions
diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst
index f8a360958f4c..e87ed5479963 100644
--- a/Documentation/kbuild/llvm.rst
+++ b/Documentation/kbuild/llvm.rst
@@ -60,17 +60,14 @@ They can be enabled individually. The full list of the parameters: ::
OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump 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.
+The integrated assembler is enabled by default. You can pass ``LLVM_IAS=0`` to
+disable it.
Omitting CROSS_COMPILE
----------------------
As explained above, ``CROSS_COMPILE`` is used to set ``--target=<triple>``.
-Unless ``LLVM_IAS=1`` is specified, ``CROSS_COMPILE`` is also used to derive
-``--prefix=<path>`` to search for the GNU assembler and linker.
-
If ``CROSS_COMPILE`` is not specified, the ``--target=<triple>`` is inferred
from ``ARCH``.
@@ -78,7 +75,12 @@ That means if you use only LLVM tools, ``CROSS_COMPILE`` becomes unnecessary.
For example, to cross-compile the arm64 kernel::
- make ARCH=arm64 LLVM=1 LLVM_IAS=1
+ make ARCH=arm64 LLVM=1
+
+If ``LLVM_IAS=0`` is specified, ``CROSS_COMPILE`` is also used to derive
+``--prefix=<path>`` to search for the GNU assembler and linker. ::
+
+ make ARCH=arm64 LLVM=1 LLVM_IAS=0 CROSS_COMPILE=aarch64-linux-gnu-
Supported Architectures
-----------------------