On Thu, Mar 4, 2021 at 5:47 AM 'Nick Desaulniers' via Clang Built
Linux [off-list ref] wrote:

+ Sami

On Wed, Mar 3, 2021 at 10:34 AM Masahiro Yamada [off-list ref] wrote:

quoted

This guarding is wrong. As Documentation/kbuild/llvm.rst notes, LLVM=1
switches the default of tools, but you can still override CC, LD, etc.
individually.

BTW, LLVM is not 1/0 flag. If LLVM is not passed in, it is empty.

Do we have the same problem with LLVM_IAS?  LGTM otherwise, but wanted
to check that before signing off.

3/4 will replace this LLVM_IAS check with AS_IS_LLVM.

We do not need to add a noise change.

(Also, the rest of the patches in this series seem more related to
DWARFv5 cleanups; this patch seems orthogonal while those are a
visible progression).

Kind of orthogonal, but I am touching the same code hunk,
which would cause a merge conflict.

quoted

Non-zero return code is all treated as failure anyway.

So, $(success,test $(LLVM) -eq 1) and $(success,test "$(LLVM)" = 1)
works equivalently in the sense that both are expanded to 'n' if LLVM
is not given. The difference is that the former internally fails due
to syntax error.

  $ test ${LLVM} -eq 1
  bash: test: -eq: unary operator expected
  $ echo $?
  2

  $ test "${LLVM}" -eq 1
  bash: test: : integer expression expected
  $ echo $?
  2

  $ test "${LLVM}" = 1
  echo $?
  1

  $ test -n "${LLVM}"
  $ echo $?
  1

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 arch/Kconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 2bb30673d8e6..2af10ebe5ed0 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig

@@ -632,7 +632,6 @@ config HAS_LTO_CLANG
        def_bool y
        # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
        depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD
-       depends on $(success,test $(LLVM) -eq 1)

IIRC, we needed some other LLVM utilities like llvm-nm and llvm-ar,
which are checked below. So I guess we can still support CC=clang
AR=llvm-ar NM=llvm-nm, and this check is redundant.

Yes, I think so.

quoted

        depends on $(success,test $(LLVM_IAS) -eq 1)
        depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
        depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
--
2.27.0

--
Thanks,
~Nick Desaulniers

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-- 
Best Regards
Masahiro Yamada