Date: Tue, 10 Jan 2012 11:16:27 -0800 (PST) From: Pedro Giffuni <pfg@freebsd.org> To: Eitan Adler <lists@eitanadler.com>, John-Mark Gurney <jmg@funkthat.com> Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org Subject: Re: svn commit: r229415 - head/lib/libvgl Message-ID: <1326222987.8062.YahooMailClassic@web113516.mail.gq1.yahoo.com> In-Reply-To: <20120110180703.GF52468@funkthat.com>
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--- Mar 10/1/12, John-Mark Gurney <jmg@funkthat.com> ha scritto: > Eitan Adler wrote this message on > Mon, Jan 09, 2012 at 23:48 -0500: > > On Mon, Jan 9, 2012 at 11:02 PM, John-Mark Gurney > <jmg@funkthat.com> > wrote: > > > Last time I did benchmarking on this ~10 years > > > ago, it was slower to use xor instead of > > > using assignments... > > > > I'd be shocked if the compiler didn't optimize this > > away to an XCHG. > > As someone else mentioned, it did... But it's still > an obfuscation of the code... > Not everyone knows this "trick" to swap two vars... > If it isn't timing critical, it's better to be > maintainable... > The code was taken from a book and it's pretty much ubiquitous as-is. If not everyone knows this "trick", then I guess it simply proves that there is a lot of value in reading books after all ;-). cheers, Pedro.
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