From owner-svn-src-all@FreeBSD.ORG Tue Nov 22 19:24:32 2011 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 0D254106566B; Tue, 22 Nov 2011 19:24:32 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id D904E8FC19; Tue, 22 Nov 2011 19:24:31 +0000 (UTC) Received: from bigwig.baldwin.cx (bigwig.baldwin.cx [96.47.65.170]) by cyrus.watson.org (Postfix) with ESMTPSA id 79AA046B42; Tue, 22 Nov 2011 14:24:31 -0500 (EST) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 01EE7B914; Tue, 22 Nov 2011 14:24:31 -0500 (EST) From: John Baldwin To: David Schultz Date: Tue, 22 Nov 2011 12:09:19 -0500 User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110714-p8; KDE/4.5.5; amd64; ; ) References: <201111220250.pAM2oPWC070856@svn.freebsd.org> <20111122153332.GA20145@zim.MIT.EDU> In-Reply-To: <20111122153332.GA20145@zim.MIT.EDU> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201111221209.19728.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Tue, 22 Nov 2011 14:24:31 -0500 (EST) Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Eitan Adler Subject: Re: svn commit: r227812 - head/lib/libc/string X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 22 Nov 2011 19:24:32 -0000 On Tuesday, November 22, 2011 10:33:32 am David Schultz wrote: > On Tue, Nov 22, 2011, Eitan Adler wrote: > > + /* use a bitwise or to avoid an additional branch instruction */ > > + if ((s1 == s2) | (n == 0)) > > + return (0); > > I think there are three issues with this. > > First, the comment suggesting that using '|' instead of '||' isn't > correct; any reasonable compiler knows how to optimize > side-effect-free expressions like these. (The reverse > transformation, from the arithmetic expression to the boolean one, > is actually harder for the compiler in general.) > > Second, the overwhelming precedent in FreeBSD is to use boolean > operators to combine boolean expressions, so you might try to get > some consensus on the issue before you go around replacing them > with bitwise operators. I for one don't find the bitwise > operators clearer, but I don't speak for everyone else. I concur, it should just use boolean logic since it is doing a boolean test. -- John Baldwin