[PATCH] media: atomisp: silence "dubious: !x | !y" warning

Luc Van Oostenryck luc.vanoostenryck at gmail.com
Sun Apr 18 21:59:31 UTC 2021


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


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