RE: [PATCH 1/4] bitops: Add single_bit_set()

[David Laight]

From: Vaittinen, Matti
> Sent: 22 November 2021 13:19
> 
> On 11/22/21 14:57, Andy Shevchenko wrote:
> > On Mon, Nov 22, 2021 at 12:42:21PM +0000, Vaittinen, Matti wrote:
> >> On 11/22/21 13:28, Andy Shevchenko wrote:
> >>> On Mon, Nov 22, 2021 at 01:03:25PM +0200, Matti Vaittinen wrote:
> >
> > What do you mean by this?
> >
> > hweight() will return you the number of the non-zero elements in the set.
> 
> Exactly. The function I added did only check if given set of bits had
> only one bit set.

Checking for exactly one bit can use the (x & (x - 1)) check on
non-zero values - which may even be better on some cpus with a
popcnt instruction.

	David

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