Re: [PATCH] bitops: add 8-bit and 16-bit rotation functions

[Segher Boessenkool]

> > > +/**
> > > + * rol16 - rotate a 16-bit value left
> > > + * @word: value to rotate
> > > + * @shift: bits to roll
> > > + */
> > > +static inline __u16 rol16(__u16 word, unsigned int shift)
> > > +{
> > > +	return (word << shift) | (word >> (16 - shift));
> > > +}
> >
> > This doesn't work for shift values of 0: you get word >> 16, and
> > shifts greater than or equal to the word size aren't valid C.  GCC
> > will warn about this, too.
>
> On the other hand, a value narrower than int will always be promoted
> first,

Erm, yes of course.  It is promoted to _signed_ int though, but
that works okay here.

> so this is not a problem in this case.

It still needs documentation for the valid values of "shift".


Segher

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