Date: Fri, 28 Jan 2005 13:11:20 +0100 From: des@des.no (=?iso-8859-1?q?Dag-Erling_Sm=F8rgrav?=) To: Jacques Fourie <jf@trispen.com> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: kernel vm question Message-ID: <xzppszpzrbr.fsf@dwp.des.no> In-Reply-To: <xzpsm4l281b.fsf@dwp.des.no> (Dag-Erling =?iso-8859-1?q?Sm=F8rgrav's?= message of "Fri, 28 Jan 2005 10:54:24 %2B0100") References: <41F90140.3020705@trispen.com> <20050127160914.GA72454@VARK.MIT.EDU> <xzpsm4l281b.fsf@dwp.des.no>
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des@des.no (Dag-Erling Sm=F8rgrav) writes: > David Schultz <das@FreeBSD.ORG> writes: > > When the line is there, the compiler is probably smart enough to > > realize that 'x=3Dy; y=3Dx' is (usually) a no-op, so it optimizes away > > both statements. > Wrong. The compiler is free to optimize away the second statement > provided that neither x nor y is declared volatile, but it cannot > optimize away the first statement. I should add: unless it can determine with absolute certainty that x is not referenced later. DES --=20 Dag-Erling Sm=F8rgrav - des@des.no
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