linux-kernel - Re: [PATCH] Makefile: remove stale cc-option checks

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Date:   Mon, 16 Aug 2021 11:35:49 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Nathan Chancellor <nathan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Vitor Massaru Iha <vitor@...saru.org>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Daniel Latypov <dlatypov@...gle.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Naresh Kamboju <naresh.kamboju@...aro.org>
Subject: Re: [PATCH] Makefile: remove stale cc-option checks

On Fri, Aug 13, 2021 at 6:43 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> On Wed, Aug 11, 2021 at 5:42 AM Nick Desaulniers
> <ndesaulniers@...gle.com> wrote:
> >
> > --param=allow-store-data-races=0 was renamed to --allow-store-data-races
> > in the GCC 10 release.
> >
> > diff --git a/Makefile b/Makefile
> > index 027fdf2a14fe..3e3fb4affba1 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -844,17 +847,17 @@ KBUILD_RUSTFLAGS += -Copt-level=z
> >  endif
> >
> >  # Tell gcc to never replace conditional load with a non-conditional one
> > -KBUILD_CFLAGS  += $(call cc-option,--param=allow-store-data-races=0)
> > +ifdef CONFIG_CC_IS_GCC
>
>
> Can you insert a comment here?
>
> # GCC 10 renamed --param=allow-store-data-races=0 to --allow-store-data-races
>
>
> It will remind us of dropping this conditional
> in the (long long distant) future.
>
>
>
>
> > +KBUILD_CFLAGS  += $(call cc-option,--allow-store-data-races,--param=allow-store-data-races=0)
> >  KBUILD_CFLAGS  += $(call cc-option,-fno-allow-store-data-races)
> > +endif

This report is confusing:
https://lore.kernel.org/linux-mm/202108160729.Lx0IJzq3-lkp@intel.com/
(csky gcc-11)

>> csky-linux-gcc: error: unrecognized command-line option '--param=allow-store-data-races=0'; did you mean '--allow-store-data-races'?

I wonder if cc-option detection for these is broken?  Perhaps I should
not touch these other than to wrap them in the CONFIG_CC_IS_GCC guard?

(Either way, I need to send a v2 in response to Naresh's report as
well. https://lore.kernel.org/lkml/CA+G9fYtPBp_-Ko_P7NuOX6vN9-66rjJuBt21h3arrLqEaQQn6w@mail.gmail.com/
It seems that -mfentry wasn't implemented for s390-linux-gnu-gcc until
gcc-9; so rather than remove top level support, perhaps a comment
about gcc-9+ s390 having support will make grepping for it easier in
the future).
-- 
Thanks,
~Nick Desaulniers