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Date:   Thu, 1 Sep 2022 12:48:58 -0500
From:   Segher Boessenkool <segher@kernel.crashing.org>
To:     Christophe Leroy <christophe.leroy@csgroup.eu>
Cc:     Gabriel Paubert <paubert@iram.es>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Zhouyi Zhou <zhouzhouyi@gmail.com>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH v2] powerpc: Fix irq_soft_mask_set() and irq_soft_mask_return() with sanitizer
Message-ID: <20220901174858.GG25951@gate.crashing.org>
References: <c0b486e782b6695092dcdb2cd340a3d44c8c266d.1661272738.git.christophe.leroy@csgroup.eu> <CMJ3VICKD1CI.SVFJOKYJPKZQ@bobo> <e022754d-b4d3-bc9f-cc79-2cf556180459@csgroup.eu> <CMJ8P06JA9OY.1S8VDV2XRU3W5@bobo> <7c11b659-5b8e-256c-508e-39395041fccb@csgroup.eu> <20220831224522.GX25951@gate.crashing.org> <ad5ebb37-6b6f-372c-dd07-fc4cfc5f5fe5@csgroup.eu> <YxBhRtTuJ4Ut7wUt@lt-gp.iram.es> <24253442-9878-c5ed-cbaa-05a5c4851a6e@csgroup.eu>
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On Thu, Sep 01, 2022 at 07:47:10AM +0000, Christophe Leroy wrote:
> Le 01/09/2022 ? 09:37, Gabriel Paubert a ?crit?:
> > Agree, but there is one thing which escapes me: why is r3 listed in the
> > outputs section (actually as a read write operand with the "+"
> > constraint modifier) but is not used after the asm which is the last
> > statement of function returning void?
> > 
> > Do I miss something?
> 
> As far as I remember, that's to tell GCC that r3 register is modified by 
> the callee. As it is an input, it couldn't be listed in the clobber list.

Inputs can be clobbered just fine, in general.  But here the operand
is tied to a register variable, and that causes the error ("'asm'
specifier for variable 'r3' conflicts with 'asm' clobber list").

Marking it in/out here is more appropriate anyway :-)


Segher