Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!ubvax!vsi1!wyse!mips!mark
From: mark@mips.COM (Mark G. Johnson)
Newsgroups: comp.arch
Subject: Re: 88k trick for FP abs/neg
Message-ID: <2553@obiwan.mips.COM>
Date: 6 Jul 88 15:50:07 GMT
References: <10136@tekecs.TEK.COM>
Reply-To: mark@mips.COM (Mark Johnson)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 18


 
In article <10136@tekecs.TEK.COM>, andrew@frip.gwd.tek.com (Andrew Klossner)
writes
	> To clear up a question: on the 88k, floating point values are
	> kept in general registers, so "abs" is done by ANDing to 0 the
	> sign bit, "neg" is done by XORing the sign bit, and "mov" is
	> done with conventional register-to-register move instructions.

Oughtn't the operand be first tested for "IEEE-ness"?  Specifically,
what if the operand of  neg  is a Signaling NaN?  Oughtn't this cause
an invalid operation exception?

Or perhaps this a case of "should" versus "shall" in the IEEE spec.....
-- 
 -- Mark Johnson	
 	MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086
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