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Date:   Sat, 11 Jan 2020 05:33:28 -0600
From:   Segher Boessenkool <segher@kernel.crashing.org>
To:     Christophe Leroy <christophe.leroy@c-s.fr>
Cc:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>, arnd@arndb.de,
        tglx@linutronix.de, vincenzo.frascino@arm.com, luto@kernel.org,
        x86@kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mips@vger.kernel.org
Subject: Re: Surprising code generated for vdso_read_begin()
Message-ID: <20200111113328.GX3191@gate.crashing.org>
References: <cover.1577111363.git.christophe.leroy@c-s.fr> <bd4557a7-9715-59aa-5d8e-488c5e516a98@c-s.fr> <20200109200733.GS3191@gate.crashing.org> <77a8bf25-6615-6c0a-56d4-eae7aa8a8f09@c-s.fr>
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On Fri, Jan 10, 2020 at 07:45:44AM +0100, Christophe Leroy wrote:
> Le 09/01/2020 ? 21:07, Segher Boessenkool a ?crit?:
> >It looks like the compiler did loop peeling.  What GCC version is this?
> >Please try current trunk (to become GCC 10), or at least GCC 9?
> 
> It is with GCC 5.5
> 
> https://mirrors.edge.kernel.org/pub/tools/crosstool/ doesn't have more 
> recent than 8.1

Arnd, can you update the tools?  We are at 8.3 and 9.2 now :-)  Or is
this hard and/or painful to do?

> With 8.1, the problem doesn't show up.

Good to hear that.  Hrm, I wonder when it was fixed...


Segher