linux-kernel - Re: [PATCH] init/Kconfig: fix CC_HAS_ASM_GOTO_TIED

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Message-ID: <CAKwvOdmYfr0yWAEBesA4D6E68qwhO46m6O90Rt1wvGr7_8mnVw@mail.gmail.com>
Date:   Fri, 19 Aug 2022 09:31:38 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     alexandre.belloni@...tlin.com,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] init/Kconfig: fix CC_HAS_ASM_GOTO_TIED_OUTPUT test with dash

On Thu, Aug 18, 2022 at 7:29 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> On Thu, Aug 18, 2022 at 8:47 AM Nick Desaulniers
> <ndesaulniers@...gle.com> wrote:
> >
> > On Thu, Aug 4, 2022 at 12:03 PM <alexandre.belloni@...tlin.com> wrote:
> > >
> > > From: Alexandre Belloni <alexandre.belloni@...tlin.com>
> > >
> > > When using dash as /bin/sh, the CC_HAS_ASM_GOTO_TIED_OUTPUT test fails
> > > with a syntax error which is not the one we are looking for:
> >
> > Thanks for the patch, though I think I'd rather see `/bin/bash`
> > hardcoded. Bash is a non-optional requirement as of
> > commit da4288b95baa ("scripts/check-local-export: avoid 'wait $!' for
> > process substitution")
> > scripts/ is kind of a mess...
>
>
>
> As for scripts/ mess,
> perhaps we can remove scripts/gcc-goto.sh?

Good idea, I think we can.

>
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48637
> seems like a bug for GCC 4.x at least...
>
>
> If we can revert the following two commits:
> f3c003f72dfb2497056bcbb864885837a1968ed5
> a9468f30b5eac6957c86aea97954553bfb7c1f18
>
> ... the asm-goto test will become simple enough
> to fit into init/Kconfig.
>
>
> If we know all GCC 5.1+ and Clang 11+ support asm-goto,
> we can remove CC_HAS_ASM_GOTO, but I am not so sure.

Yeah, asm goto has been supported for many releases of either compiler
at this point; here's versions we don't support anymore for kbuild yet
demonstrate asm goto support: https://godbolt.org/z/dr3zzn98e.

I'll send a patch with your suggested-by tag.

-- 
Thanks,
~Nick Desaulniers