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 ...!decwrl!mips!mark (408) 991-0208