linux-kernel - Re: [PATCH] coccinelle: misc: add minmax script

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Date:   Wed, 17 Feb 2021 22:17:56 +0100 (CET)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Denis Efremov <efremov@...ux.com>
cc:     Julia Lawall <julia.lawall@...ia.fr>, cocci@...teme.lip6.fr,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coccinelle: misc: add minmax script



On Tue, 16 Feb 2021, Denis Efremov wrote:

> Check for opencoded min(), max() implementations.

Some cases that could be improved:

diff -u -p a/drivers/platform/x86/asus-laptop.c
b/drivers/platform/x86/asus-laptop.c
--- a/drivers/platform/x86/asus-laptop.c
+++ b/drivers/platform/x86/asus-laptop.c
@@ -1195,7 +1195,7 @@ static ssize_t ls_level_store(struct dev
        if (rv < 0)
                return rv;

-       value = (0 < value) ? ((15 < value) ? 15 : value) : 0;
+       value = (0 < value) ? (min(15, value)) : 0;
        /* 0 <= value <= 15 */
        asus_als_level(asus, value);


diff -u -p a/sound/pci/ctxfi/ctatc.c b/sound/pci/ctxfi/ctatc.c
--- a/sound/pci/ctxfi/ctatc.c
+++ b/sound/pci/ctxfi/ctatc.c
@@ -382,7 +382,7 @@ static int atc_pcm_playback_start(struct
	apcm->started = 1;

        max_cisz = src->multi * src->rsc.msr;
-       max_cisz = 0x80 * (max_cisz < 8 ? max_cisz : 8);
+       max_cisz = 0x80 * (min(max_cisz, 8));


> +func(...)
> +{
> +	... when any
> +*	(x cmp y) ?@p x : y
> +	... when any
> +}

In all cases, this would be more efficient as:

func(...)
{
 <...
* (x cmp y) ?@p x : y
 ...>
}

There is an optimization that causes this to be just a search through the
nodes of the control-flow graph, rather than following the actual control
flow from the beginning of the function to the end.

> +@...ipt:python depends on report@
> +p << rmax.p;
> +@@
> +
> +coccilib.report.print_report(p[0], "WARNING opportunity for max()")
> +
> +@...ipt:python depends on org@
> +p << rmax.p;
> +@@
> +
> +coccilib.report.print_todo(p[0], "WARNING opportunity for max()")

All of the org cases should be coccilib.org, not coccilib.report.

julia