Re: [PATCH kbuild] kbuild: Allow to reduce the number of suffixes for clang thin-lto build

[Nathan Chancellor <nathan@kernel.org>]

On Fri, Mar 06, 2026 at 02:12:44PM -0800, Yonghong Song wrote:
> So you mean we do not need a new config. Should just check clang and
> clang versionn like below?
> 
> diff --git a/Makefile b/Makefile
> index e944c6e71e81..9bd3990024c5 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1034,6 +1034,11 @@ endif
>  ifdef CONFIG_LTO_CLANG
>  ifdef CONFIG_LTO_CLANG_THIN
>  CC_FLAGS_LTO   := -flto=thin -fsplit-lto-unit
> +ifdef CONFIG_CC_IS_CLANG
> +ifeq ($(shell test $(CONFIG_CLANG_VERSION) -ge 230000; echo $$?),0)

This is the same as

  ifeq ($(call clang-min-version,230000),y)

That being said, could we not just do a dynamic check so that it always
works when these flags are supported?

> +KBUILD_LDFLAGS += --lto-whole-program-visibility -mllvm -always-rename-promoted-locals=false

  KBUILD_LDFLAGS += $(call ld-option,--lto-whole-program-visibility -mllvm -always-rename-promoted-locals=false)

> +endif
> +endif
>  else
>  CC_FLAGS_LTO   := -flto
>  endif
> 
> I think this should work. In rare case, renaming the function should
> solve the problem.

I agree with Josh that having this be the default behavior with the
workarounds that we have available to us to avoid problems from it is
worth it. Thanks for chasing this after the discussions at LPC.

Cheers,
Nathan