From: Igor Stoppa <igor.stoppa@gmail.com>
To: Paul Burton <paul.burton@mips.com>
Cc: David Daney <ddaney@caviumnetworks.com>,
Igor Stoppa <igor.stoppa@huawei.com>,
Ralf Baechle <ralf@linux-mips.org>,
James Hogan <jhogan@kernel.org>,
linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mips: bug: add unlikely() to BUG_ON()
Date: Mon, 10 Sep 2018 12:45:03 +0300 [thread overview]
Message-ID: <d702acea-0aac-abc3-c48e-21f0e44d5870@gmail.com> (raw)
In-Reply-To: <20180907220208.nqucxycxsxmyxt4m@pburton-laptop>
Hi Paul,
On 08/09/18 01:02, Paul Burton wrote:
> I'm not sure this will actually do anything.
>
> __BUG_ON() doesn't use the value of its condition argument for regular
> control flow unless it's compile-time constant anyway, in which case
> unlikely() should be redundant because the compiler knows the value
> already.
>
> If the condition isn't compile-time constant then we just emit a tne
> (trap-if-not-equal) instruction using inline asm. That will generate an
> exception if the value is non-zero at runtime. I don't see how adding
> unlikely() is going to help the compiler do anything differently with
> that.
Thank you for the explanation. Please discard this patch.
--
igor
prev parent reply other threads:[~2018-09-10 9:45 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-07 18:03 [PATCH] mips: bug: add unlikely() to BUG_ON() Igor Stoppa
2018-09-07 22:02 ` Paul Burton
2018-09-10 9:45 ` Igor Stoppa [this message]
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