Subject: Re: [patch 14/44] generic hweight{64,32,16,8}()

From: Ulrich Eckhardt <[email-masked]>
Date: Fri, 3 Feb 2006 09:31:42 +0100

On Wednesday 01 February 2006 10:02, Akinobu Mita wrote:
> unsigned int hweight32(unsigned int w);
> unsigned int hweight16(unsigned int w);
> unsigned int hweight8(unsigned int w);
> unsigned long hweight64(__u64 w);

IMHO, this should use explicitly sized integers like __u8, __u16 etc, unless 
there are stringent reasons like better register use - which is hard to tell 
for generic C code. Also, why on earth is the returntype for hweight64 a 
long?

> +static inline unsigned int hweight32(unsigned int w)
> +{
> +        unsigned int res = (w & 0x55555555) + ((w >> 1) & 0x55555555);
> +        res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
[...]

Why not use unsigned constants here?

> +static inline unsigned long hweight64(__u64 w)
> +{
[..]
> +	u64 res;
> +	res = (w & 0x5555555555555555ul) + ((w >> 1) & 0x5555555555555555ul);

Why not use initialisation here, too?

just my 2c

Uli