linux-kernel - Re: [PATCH] scripts: coccinelle: check for !(un)?likely usage

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Message-ID: <e48665b3-eeb6-a258-18bb-779e09313e40@linux.com>
Date:   Wed, 28 Aug 2019 16:57:26 +0300
From:   Denis Efremov <efremov@...ux.com>
To:     Julia Lawall <julia.lawall@...6.fr>
Cc:     Joe Perches <joe@...ches.com>, cocci@...teme.lip6.fr,
        linux-kernel@...r.kernel.org,
        Gilles Muller <Gilles.Muller@...6.fr>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Michal Marek <michal.lkml@...kovi.net>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [PATCH] scripts: coccinelle: check for !(un)?likely usage

On 8/28/19 3:41 PM, Denis Efremov wrote:
> 
>>
>> As a human I am confused. Is !likely(x) equivalent to x or !x?
>>
>> Julia
>>
> 
> As far as I could understand it:
> 
> # define likely(x)	__builtin_expect(!!(x), 1)
> !likely(x)
> !__builtin_expect(!!(x), 1)
> !((!!(x)) == 1)
> (!!(x)) != 1, since !! could result in 0 or 1
> (!!(x)) == 0
> !(!!(x))
> !!!(x)
> !(x)
> 

Thanks Rasmus for the explanation, this should be:
!likely(x)
!__builtin_expect(!!(x), 1)
!(!!(x))
!!!(x)
!(x)

Denis