On Fri, Mar 4, 2022 at 9:14 AM Nathan Chancellor nathan@kernel.org wrote:
diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst index d32616891dcf..68b74416ec48 100644 --- a/Documentation/kbuild/llvm.rst +++ b/Documentation/kbuild/llvm.rst @@ -49,17 +49,36 @@ example: :: LLVM Utilities
-LLVM has substitutes for GNU binutils utilities. Kbuild supports ``LLVM=1`` -to enable them. ::
make LLVM=1-They can be enabled individually. The full list of the parameters: :: +LLVM has substitutes for GNU binutils utilities. They can be enabled individually. +The full list of supported make variables: ::
make CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \ OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump READELF=llvm-readelf \ HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar HOSTLD=ld.lld+To simplify the above command, Kbuild supports the ``LLVM`` variable: ::
make LLVM=1+If your LLVM tools are not available in your PATH, you can supply their +location using the LLVM variable with a trailing slash: ::
make LLVM=/path/to/llvm/+which will use ``/path/to/llvm/clang``, ``/path/to/llvm/ld.lld``, etc.
I don't think we should do this; `PATH=/path/to/llvm/ make LLVM=1` works and (my interpretation of what) Masahiro said "if anyone asks for this, here's how we could do that." I don't think I've seen an explicit ask for that. I'd rather LLVM= have 2 behaviors than 3, but I won't hold this patch up over that. Either way:
Reviewed-by: Nick Desaulniers ndesaulniers@google.com
+If your LLVM tools have a version suffix and you want to test with that +explicit version rather than the unsuffixed executables like ``LLVM=1``, you +can pass the suffix using the ``LLVM`` variable: ::
make LLVM=-14+which will use ``clang-14``, ``ld.lld-14``, etc.
+``LLVM=0`` is not the same as omitting ``LLVM`` altogether, it will behave like +``LLVM=1``.
Hmm... I can see someone's build wrappers setting LLVM=1, then them being surprised that appending LLVM=0 doesn't disable LLVM=1 as they might expect. But Masahiro says let's fix this later which is fine.
-- Thanks, ~Nick Desaulniers