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From:   =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>
To:     "liaochang (A)" <liaochang1@huawei.com>,
        Xim <chenguokai17@mails.ucas.ac.cn>
Cc:     paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, rostedt@goodmis.org, mingo@redhat.com,
        sfr@canb.auug.org.au, linux-riscv@lists.infradead.org,
        linux-kernel@vger.kernel.org, Liao Chang <liaoclark@163.com>
Subject: Re: [PATCH v4 0/8] Add OPTPROBES feature on RISCV
In-Reply-To: <598bc40d-e826-f9cc-14fd-f4570051f4c6@huawei.com>
References: <20221106100316.2803176-1-chenguokai17@mails.ucas.ac.cn>
 <87y1sm1z8j.fsf@all.your.base.are.belong.to.us>
 <9A705974-A007-45E2-BC5D-A7E90821A258@mails.ucas.ac.cn>
 <598bc40d-e826-f9cc-14fd-f4570051f4c6@huawei.com>
Date:   Tue, 08 Nov 2022 14:12:14 +0100
Message-ID: <87bkphr3o1.fsf@all.your.base.are.belong.to.us>
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"liaochang (A)" <liaochang1@huawei.com> writes:

>>>> +	*rd =3D ((kw | ow) =3D=3D 1UL) ? 0 : __builtin_ctzl((kw | ow) & ~1UL=
);
>>>> +	*ra =3D (kw =3D=3D 1UL) ? 0 : __builtin_ctzl(kw & ~1UL);
>>>
>>> Hmm, __builtin_ctzl is undefined for 0, right? Can that be triggered
>>> here?
>
> This corner case has been taken into account, look these condition parts,
> if kw =3D=3D 1UL this expression will return 0 directly, no chance to inv=
oke __builtin_ctzl.

Indeed! Thanks for making that clear! Looking forward to the next
revision!


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