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From:   Michael Ellerman <patch-notifications@ellerman.id.au>
To:     Michael Ellerman <mpe@ellerman.id.au>,
        Paul Mackerras <paulus@samba.org>, jakub@redhat.com,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        segher@kernel.crashing.org
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
In-Reply-To: <348c2d3f19ffcff8abe50d52513f989c4581d000.1603375524.git.christophe.leroy@csgroup.eu>
References: <348c2d3f19ffcff8abe50d52513f989c4581d000.1603375524.git.christophe.leroy@csgroup.eu>
Subject: Re: [PATCH] powerpc/bitops: Fix possible undefined behaviour with fls() and fls64()
Message-Id: <160630540248.2174375.3049361746995827520.b4-ty@ellerman.id.au>
Date:   Wed, 25 Nov 2020 22:57:41 +1100 (AEDT)
Precedence: bulk

On Thu, 22 Oct 2020 14:05:46 +0000 (UTC), Christophe Leroy wrote:
> fls() and fls64() are using __builtin_ctz() and _builtin_ctzll().
> On powerpc, those builtins trivially use ctlzw and ctlzd power
> instructions.
> 
> Allthough those instructions provide the expected result with
> input argument 0, __builtin_ctz() and __builtin_ctzll() are
> documented as undefined for value 0.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/bitops: Fix possible undefined behaviour with fls() and fls64()
      https://git.kernel.org/powerpc/c/1891ef21d92c4801ea082ee8ed478e304ddc6749

cheers