From: Julia Lawall <julia.lawall@lip6.fr>
To: Denis Efremov <efremov@linux.com>
Cc: Michal Marek <michal.lkml@markovi.net>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Nicolas Palix <nicolas.palix@imag.fr>,
linux-kernel@vger.kernel.org,
Markus Elfring <Markus.Elfring@web.de>,
Joe Perches <joe@perches.com>,
cocci@systeme.lip6.fr
Subject: Re: [Cocci] [PATCH v2] scripts: coccinelle: check for !(un)?likely usage
Date: Fri, 6 Sep 2019 22:19:21 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1909062217240.2643@hadrien> (raw)
In-Reply-To: <20190829171013.22956-1-efremov@linux.com>
On Thu, 29 Aug 2019, Denis Efremov wrote:
> This patch adds coccinelle script for detecting !likely and
> !unlikely usage. These notations are confusing. It's better
> to replace !likely(x) with unlikely(!x) and !unlikely(x) with
> likely(!x) for readability.
>
> The rule transforms !likely(x) to unlikely(!x) based on this logic:
> !likely(x) iff
> !__builtin_expect(!!(x), 1) iff
> __builtin_expect(!!!(x), 0) iff
> unlikely(!x)
>
> For !unlikely(x) to likely(!x):
> !unlikely(x) iff
> !__builtin_expect(!!(x), 0) iff
> __builtin_expect(!!!(x), 1) iff
> likely(!x)
>
> Signed-off-by: Denis Efremov <efremov@linux.com>
> Cc: Julia Lawall <Julia.Lawall@lip6.fr>
> Cc: Gilles Muller <Gilles.Muller@lip6.fr>
> Cc: Nicolas Palix <nicolas.palix@imag.fr>
> Cc: Michal Marek <michal.lkml@markovi.net>
> Cc: Markus Elfring <Markus.Elfring@web.de>
> Cc: Joe Perches <joe@perches.com>
> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
A small improvement though would be to improve the explicit dependency of
the last four python rules on r1 and r2. Those rules won't execute unless
the inherited metavariable has a value, which makes the same dependency.
julia
> ---
> scripts/coccinelle/misc/neg_unlikely.cocci | 89 ++++++++++++++++++++++
> 1 file changed, 89 insertions(+)
> create mode 100644 scripts/coccinelle/misc/neg_unlikely.cocci
>
> diff --git a/scripts/coccinelle/misc/neg_unlikely.cocci b/scripts/coccinelle/misc/neg_unlikely.cocci
> new file mode 100644
> index 000000000000..9aac0a7ff042
> --- /dev/null
> +++ b/scripts/coccinelle/misc/neg_unlikely.cocci
> @@ -0,0 +1,89 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/// Use unlikely(!x) instead of !likely(x) and vice versa.
> +/// Notations !unlikely(x) and !likely(x) are confusing.
> +//
> +// Confidence: High
> +// Copyright: (C) 2019 Denis Efremov, ISPRAS.
> +// Options: --no-includes --include-headers
> +
> +virtual patch
> +virtual context
> +virtual org
> +virtual report
> +
> +//----------------------------------------------------------
> +// For context mode
> +//----------------------------------------------------------
> +
> +@depends on context disable unlikely@
> +expression E;
> +@@
> +
> +*! \( likely \| unlikely \) (E)
> +
> +//----------------------------------------------------------
> +// For patch mode
> +//----------------------------------------------------------
> +
> +@depends on patch disable unlikely@
> +expression E;
> +@@
> +
> +(
> +-!likely(!E)
> ++unlikely(E)
> +|
> +-!likely(E)
> ++unlikely(!E)
> +|
> +-!unlikely(!E)
> ++likely(E)
> +|
> +-!unlikely(E)
> ++likely(!E)
> +)
> +
> +//----------------------------------------------------------
> +// For org and report mode
> +//----------------------------------------------------------
> +
> +@r1 depends on (org || report) disable unlikely@
> +expression E;
> +position p;
> +@@
> +
> +!likely@p(E)
> +
> +@r2 depends on (org || report) disable unlikely@
> +expression E;
> +position p;
> +@@
> +
> +!unlikely@p(E)
> +
> +@script:python depends on org && r1@
> +p << r1.p;
> +@@
> +
> +coccilib.org.print_todo(p[0], "unlikely(!x) is more readable than !likely(x)")
> +
> +@script:python depends on org && r2@
> +p << r2.p;
> +@@
> +
> +coccilib.org.print_todo(p[0], "likely(!x) is more readable than !unlikely(x)")
> +
> +@script:python depends on report && r1@
> +p << r1.p;
> +@@
> +
> +coccilib.report.print_report(p[0],
> + "unlikely(!x) is more readable than !likely(x)")
> +
> +@script:python depends on report && r2@
> +p << r2.p;
> +@@
> +
> +coccilib.report.print_report(p[0],
> + "likely(!x) is more readable than !unlikely(x)")
> +
> --
> 2.21.0
>
>
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next prev parent reply other threads:[~2019-09-06 20:20 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-25 13:05 [Cocci] [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
2019-08-28 11:59 ` Joe Perches
2019-08-28 12:33 ` 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
[not found] ` <20190901172403.GA1047@bug>
2019-09-01 17:39 ` Denis Efremov
2019-08-29 17:10 ` [Cocci] [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 [this message]
2019-09-06 20:55 ` Denis Efremov
2019-09-07 8:05 ` [Cocci] [v2] " Markus Elfring
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