linux-mips
[Top] [All Lists]

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

To: Akinobu Mita <mita@miraclelinux.com>
Subject: Re: [patch 14/44] generic hweight{64,32,16,8}()
From: Ulrich Eckhardt <eckhardt@satorlaser.com>
Date: Fri, 3 Feb 2006 09:31:42 +0100
Cc: linux-kernel@vger.kernel.org, Richard Henderson <rth@twiddle.net>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Russell King <rmk@arm.linux.org.uk>, Ian Molton <spyro@f2s.com>, dev-etrax@axis.com, David Howells <dhowells@redhat.com>, Yoshinori Sato <ysato@users.sourceforge.jp>, Linus Torvalds <torvalds@osdl.org>, linux-ia64@vger.kernel.org, Hirokazu Takata <takata@linux-m32r.org>, linux-m68k@lists.linux-m68k.org, Greg Ungerer <gerg@uclinux.org>, linux-mips@linux-mips.org, parisc-linux@parisc-linux.org, linuxppc-dev@ozlabs.org, linux390@de.ibm.com, linuxsh-dev@lists.sourceforge.net, linuxsh-shmedia-dev@lists.sourceforge.net, sparclinux@vger.kernel.org, ultralinux@vger.kernel.org, Miles Bader <uclinux-v850@lsi.nec.co.jp>, Andi Kleen <ak@suse.de>, Chris Zankel <chris@zankel.net>
In-reply-to: <20060201090325.905071000@localhost.localdomain>
Organization: Sator Laser GmbH
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20060201090224.536581000@localhost.localdomain> <20060201090325.905071000@localhost.localdomain>
Sender: linux-mips-bounce@linux-mips.org
User-agent: KMail/1.8.3
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

<Prev in Thread] Current Thread [Next in Thread>