Re: [PATCH v7 7/7] Add Propeller configuration for kernel build

[Rong Xu <xur@google.com>]

Thanks Nathan for finding this out!

We changed the propeller option with this patch:
https://github.com/llvm/llvm-project/pull/110039

Currently, this patch is only in the ToT clang (v20) and not yet
released in v19.
I'll add a compiler version check to the patch: if the clang version >= 20,
use the new option.

If this patch is later released in v19.x clang, I'll have to update the check
accordingly.

If I don't hear objections, I'll send a fixup on top of Masahiro's branch.

Thanks,

-Rong

On Thu, Nov 7, 2024 at 12:45 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Rong,
>
> On Sat, Nov 02, 2024 at 10:51:14AM -0700, Rong Xu wrote:
> > diff --git a/scripts/Makefile.propeller b/scripts/Makefile.propeller
> > new file mode 100644
> > index 0000000000000..344190717e471
> > --- /dev/null
> > +++ b/scripts/Makefile.propeller
> > @@ -0,0 +1,28 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +# Enable available and selected Clang Propeller features.
> > +ifdef CLANG_PROPELLER_PROFILE_PREFIX
> > +  CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=list=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt -ffunction-sections
> > +  KBUILD_LDFLAGS += --symbol-ordering-file=$(CLANG_PROPELLER_PROFILE_PREFIX)_ld_profile.txt --no-warn-symbol-ordering
> > +else
> > +  CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=labels
> > +endif
>
> It appears that '-fbasic-block-sections=labels' has been deprecated in
> the main branch of LLVM, as I see a warning repeated over and over when
> building allmodconfig:
>
>   clang: warning: argument '-fbasic-block-sections=labels' is deprecated, use '-fbasic-block-address-map' instead [-Wdeprecated]
>
> https://github.com/llvm/llvm-project/commit/7b7747dc1d3da1a829503ea9505b4cecce4f5bda
>
> Sorry that I missed this during testing, as I was only using clang-19 at
> the time.
>
> I think you can send a fixup on top of Masahiro's branch:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/log/?h=kbuild
>
> > +# Propeller requires debug information to embed module names in the profiles.
> > +# If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. Skip this for AutoFDO,
> > +# as the option should already be set.
> > +ifndef CONFIG_DEBUG_INFO
> > +  ifndef CONFIG_AUTOFDO_CLANG
> > +    CFLAGS_PROPELLER_CLANG += -gmlt
> > +  endif
> > +endif
> > +
> > +ifdef CONFIG_LTO_CLANG_THIN
> > +  ifdef CLANG_PROPELLER_PROFILE_PREFIX
> > +    KBUILD_LDFLAGS += --lto-basic-block-sections=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt
> > +  else
> > +    KBUILD_LDFLAGS += --lto-basic-block-sections=labels
>
> I think this might have a similar problem but I have not tested.
>
> > +  endif
> > +endif
> > +
> > +export CFLAGS_PROPELLER_CLANG
>
> Cheers,
> Nathan