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Date:   Sat, 24 Sep 2022 13:30:50 -0500
From:   Segher Boessenkool <segher@kernel.crashing.org>
To:     Nicholas Piggin <npiggin@gmail.com>
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/irq: Modernise inline assembly in irq_soft_mask_{set,return}
Message-ID: <20220924183050.GP25951@gate.crashing.org>
References: <178f30ff62c0317061f019b3dbbc079073f104c3.1663656058.git.christophe.leroy@csgroup.eu> <CN3LB8F3D9LM.3W1RQRVS64UXU@bobo> <20220923121829.GL25951@gate.crashing.org> <CN3X6YN1FRQ3.1Z9BVD6WYQY3M@bobo> <20220923221543.GN25951@gate.crashing.org>
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On Fri, Sep 23, 2022 at 05:15:43PM -0500, Segher Boessenkool wrote:
> On Sat, Sep 24, 2022 at 02:26:52AM +1000, Nicholas Piggin wrote:
> > I still don't see what clauses guarantees asm("%0" ::"r"(foo)) to give
> > 13. It doesn't say access via inline assembly is special,
> 
> But it is.  It is for all register variables, local and global.  I agree
> this isn't documented clearly.  For local register variables this is the
> *only* thing guaranteed; for global register vars there is more (it
> changes the ABI, there are safe/restore effects, that kind of thing).

I filed <https://gcc.gnu.org/PR107027> to improve the docs.  Thanks for
bringing this to our attention!


Segher