lkml.org 
[lkml]   [2021]   [Apr]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] media: atomisp: silence "dubious: !x | !y" warning
On Sat, Apr 17, 2021 at 09:31:32PM +0000, David Laight wrote:
> > > Upon running sparse, "warning: dubious: !x | !y" is brought to notice
> > > for this file. Logical and bitwise OR are basically the same in this
> > > context so it doesn't cause a runtime bug. But let's change it to
> > > logical OR to make it cleaner and silence the Sparse warning.
>
> The old code is very likely to by slightly more efficient.
>
> It may not matter here, but it might in a really hot path.
>
> Since !x | !y and !x || !y always have the same value
> why is sparse complaining at all.

They both will have the same value here and any half-decent
compiler know that and thus generate the same code, so no
worries about efficiency.

Sparse complains because the programmer's intention is not clear.
Was a boolean context or a bitwise context that was meant?
Maybe '||' was meant and the RHS had to be short cut?
Maybe what was meant was '~x | ~y'?

-- Luc

\
 
 \ /
  Last update: 2021-04-19 00:02    [W:0.057 / U:0.660 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site