From: Matt Sealey <matt@genesi-usa.com>
To: Scott Wood <scottwood@freescale.com>
Cc: linuxppc-dev@ozlabs.org, Kevin Diggs <kevdig@hypersurf.com>
Subject: Re: cntlzw
Date: Fri, 06 Jun 2008 10:53:13 +0100 [thread overview]
Message-ID: <48490909.4020901@genesi-usa.com> (raw)
In-Reply-To: <4845A55E.2030503@freescale.com>
It's in the Compiler Writer's Guide with explanation; section 5-10.
http://www-01.ibm.com/chips/techlib/techlib.nsf/techdocs/852569B20050FF7785256996007558C6
There are lots of clever examples in there, it's definitely recommended
reading (I should make a cheat sheet of chapter 5 though so I can pin it
to my wall)
--
Matt Sealey <matt@genesi-usa.com>
Genesi, Manager, Developer Relations
Scott Wood wrote:
> Kevin Diggs wrote:
>> Hi,
>>
>> x86 has bsf and bsr. PPC has cntlzw which I think is equivalent to
>> bsr. Anyone know of a sneaky algorithm to do bsf?
>
> wordsize - 1 - cntlzw(x & ~(x - 1));
>
> -Scott
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-dev
prev parent reply other threads:[~2008-06-06 9:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-03 20:06 cntlzw Kevin Diggs
2008-06-03 20:11 ` cntlzw Scott Wood
2008-06-06 9:53 ` Matt Sealey [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=48490909.4020901@genesi-usa.com \
--to=matt@genesi-usa.com \
--cc=kevdig@hypersurf.com \
--cc=linuxppc-dev@ozlabs.org \
--cc=scottwood@freescale.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.