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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Mon, 18 Mar 2019 10:09:37 -0700
Message-ID: <CAKwvOdkXobdu74Fo0fiS4xkikqZdKS=gWN61pVAFBbXRPoenRw@mail.gmail.com>
Subject: Re: [PATCH] x86/vdso: include generic __lshrdi3 in 32-bit vDSO
To:     Matthias Kaehlcke <mka@chromium.org>
Cc:     Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Manoj Gupta <manojgupta@chromium.org>,
        Tiancong Wang <tcwang@chromium.org>,
        Stephen Hines <srhines@google.com>,
        clang-built-linux@googlegroups.com,
        Masahiro Yamada <yamada.masahiro@socionext.com>
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On Fri, Mar 15, 2019 at 3:29 PM Matthias Kaehlcke <mka@chromium.org> wrote:
> On Fri, Mar 15, 2019 at 02:31:09PM -0700, 'Nick Desaulniers' via Clang Built Linux wrote:
> > Is there a config I can set to reproduce this, in order to help
> > test?
>
> I encountered it with a Chrome OS specific configuration, but a
> defconfig should do.

defconfig selects CONFIG_OPTIMIZE_FOR_PERFORMANCE=y.  I needed to
select CONFIG_CC_OPTIMIZE_FOR_SIZE=y to repro.  My CI is simply
running defconfigs, which is why I didn't catch this.

> Note that you probably need a development version
> of clang to reproduce this.

Yep.  Thanks for the patch.

Tested-by: Nick Desaulniers <ndesaulniers@google.com>
-- 
Thanks,
~Nick Desaulniers