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

[Julia Lawall]

On Wed, 28 Aug 2019, Rasmus Villemoes wrote:

> On 25/08/2019 21.19, Julia Lawall wrote:
> >
> >
> >> On 26 Aug 2019, at 02:59, Denis Efremov <efre...@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).

Thanks.  Making the change seems like a good idea.

julia