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81 lines
2.0 KiB
81 lines
2.0 KiB
20 years ago
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/* IEEE754 floating point arithmetic
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* double precision: common utilities
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*/
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/*
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* MIPS floating point support
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* Copyright (C) 1994-2000 Algorithmics Ltd.
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* http://www.algor.co.uk
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*
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* ########################################################################
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*
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* This program is free software; you can distribute it and/or modify it
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* under the terms of the GNU General Public License (Version 2) as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
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*
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* ########################################################################
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*/
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#include "ieee754dp.h"
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/* modf function is always exact for a finite number
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*/
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ieee754dp ieee754dp_modf(ieee754dp x, ieee754dp * ip)
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{
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COMPXDP;
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CLEARCX;
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EXPLODEXDP;
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switch (xc) {
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case IEEE754_CLASS_SNAN:
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case IEEE754_CLASS_QNAN:
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case IEEE754_CLASS_INF:
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case IEEE754_CLASS_ZERO:
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*ip = x;
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return x;
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case IEEE754_CLASS_DNORM:
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/* far to small */
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*ip = ieee754dp_zero(xs);
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return x;
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case IEEE754_CLASS_NORM:
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break;
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}
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if (xe < 0) {
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*ip = ieee754dp_zero(xs);
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return x;
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}
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if (xe >= DP_MBITS) {
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*ip = x;
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return ieee754dp_zero(xs);
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}
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/* generate ipart mantissa by clearing bottom bits
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*/
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*ip = builddp(xs, xe + DP_EBIAS,
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((xm >> (DP_MBITS - xe)) << (DP_MBITS - xe)) &
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~DP_HIDDEN_BIT);
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/* generate fpart mantissa by clearing top bits
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* and normalizing (must be able to normalize)
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*/
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xm = (xm << (64 - (DP_MBITS - xe))) >> (64 - (DP_MBITS - xe));
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if (xm == 0)
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return ieee754dp_zero(xs);
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while ((xm >> DP_MBITS) == 0) {
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xm <<= 1;
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xe--;
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}
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return builddp(xs, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT);
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}
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