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Message-ID: <6B84B1FF221BD011B0AC08002BE69206683E78@excmso.mso.dec.com>
From: Bob Supnik <Bob.Supnik@digital.com>
To: pups@minnie.cs.adfa.oz.au
Subject: RE: Bug in Bob Supnik's Emulator?
Date: Mon, 6 Apr 1998 17:25:57 -0400 
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There is indeed a bug in the floating point emulator: MODf was setting
the condition codes off the integer result, not the fractional result.

To fix the bug, look for this code fragment in source module pdp11_fp.c

case 3:							/* MODf */
	ReadFP (&fsrc, GeteaFP (dstspec, lenf), dstspec, lenf);
	F_LOAD (qdouble, FR[ac], fac);
	newV = modfp11 (&fac, &fsrc, &modfrac);
	F_STORE (qdouble, fac, FR[ac | 1]);
	F_STORE (qdouble, modfrac, FR[ac]);
==>	FPS = setfcc (FPS, fac.h, newV);
	break;

Change the indicated code line to be:

==>	FPS = setfcc (FPS, modfrac.h, newV);

and recompile.

Thanks to Warren Toomey for getting me the source to FACTOR, which
showed the bug.

(I can't believe this is the problem with vi, but who knows?  A bug in
MODf could affect the binary to decimal conversion routines in the run
time libraries.)