From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Julia Lawall <julia.lawall@lip6.fr>, Denis Efremov <efremov@linux.com>
Cc: Joe Perches <joe@perches.com>,
cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org,
Gilles Muller <Gilles.Muller@lip6.fr>,
Nicolas Palix <nicolas.palix@imag.fr>,
Michal Marek <michal.lkml@markovi.net>
Subject: Re: [PATCH] scripts: coccinelle: check for !(un)?likely usage
Date: Wed, 28 Aug 2019 13:33:31 +0200 [thread overview]
Message-ID: <95c32d19-eb4d-a214-6332-038610ec3dbd@rasmusvillemoes.dk> (raw)
In-Reply-To: <4E9DDF9E-C883-44F0-A3F4-CD49284DB60D@lip6.fr>
On 25/08/2019 21.19, Julia Lawall wrote:
>
>
>> On 26 Aug 2019, at 02:59, Denis Efremov <efremov@linux.com> wrote:
>>
>>
>>
>>> On 25.08.2019 19:37, Joe Perches wrote:
>>>> On Sun, 2019-08-25 at 16:05 +0300, Denis Efremov wrote:
>>>> This patch adds coccinelle script for detecting !likely and !unlikely
>>>> usage. It's better to use unlikely instead of !likely and vice versa.
>>>
>>> Please explain _why_ is it better in the changelog.
>>>
>>
>> In my naive understanding the negation (!) before the likely/unlikely
>> could confuse the compiler
>
> As a human I am confused. Is !likely(x) equivalent to x or !x?
#undef likely
#undef unlikely
#define likely(x) (x)
#define unlikely(x) (x)
should be a semantic no-op. So changing !likely(x) to unlikely(x) is
completely wrong. If anything, !likely(x) can be transformed to
unlikely(!x).
Rasmus
next prev parent reply other threads:[~2019-08-28 11:33 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-25 13:05 [PATCH] scripts: coccinelle: check for !(un)?likely usage Denis Efremov
2019-08-25 15:30 ` Markus Elfring
2019-08-25 21:06 ` Denis Efremov
2019-08-25 15:30 ` Markus Elfring
2019-08-25 16:37 ` Joe Perches
2019-08-25 18:59 ` Denis Efremov
2019-08-25 19:19 ` Julia Lawall
2019-08-28 11:33 ` Rasmus Villemoes [this message]
2019-08-28 11:59 ` Joe Perches
2019-08-28 12:33 ` Denis Efremov
2019-08-28 13:05 ` Rasmus Villemoes
2019-08-28 13:14 ` Denis Efremov
2019-08-28 12:33 ` Julia Lawall
2019-08-28 12:41 ` Denis Efremov
2019-08-28 13:57 ` Denis Efremov
2019-08-25 21:19 ` Denis Efremov
2019-09-01 17:24 ` Pavel Machek
2019-09-01 17:39 ` Denis Efremov
2019-08-29 17:10 ` [PATCH v2] " Denis Efremov
2019-08-29 17:13 ` Denis Efremov
2019-08-30 0:42 ` Julia Lawall
2019-08-30 6:56 ` Denis Efremov
2019-08-30 8:06 ` Rasmus Villemoes
2019-08-29 20:07 ` Markus Elfring
2019-08-30 7:55 ` Markus Elfring
2019-09-06 20:19 ` Julia Lawall
2019-09-06 20:55 ` Denis Efremov
2019-09-07 8:05 ` [v2] " Markus Elfring
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