158 строки
4.3 KiB
C
158 строки
4.3 KiB
C
/* 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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ieee754dp ieee754dp_div(ieee754dp x, ieee754dp y)
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{
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COMPXDP;
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COMPYDP;
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EXPLODEXDP;
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EXPLODEYDP;
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CLEARCX;
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FLUSHXDP;
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FLUSHYDP;
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switch (CLPAIR(xc, yc)) {
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
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case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
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SETCX(IEEE754_INVALID_OPERATION);
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return ieee754dp_nanxcpt(ieee754dp_indef(), "div", x, y);
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
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return y;
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
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case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
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return x;
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/* Infinity handling
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*/
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
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SETCX(IEEE754_INVALID_OPERATION);
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return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
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return ieee754dp_zero(xs ^ ys);
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
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case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
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return ieee754dp_inf(xs ^ ys);
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/* Zero handling
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*/
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
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SETCX(IEEE754_INVALID_OPERATION);
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return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
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SETCX(IEEE754_ZERO_DIVIDE);
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return ieee754dp_xcpt(ieee754dp_inf(xs ^ ys), "div", x, y);
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
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case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
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return ieee754dp_zero(xs == ys ? 0 : 1);
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
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DPDNORMX;
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
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DPDNORMY;
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break;
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case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
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DPDNORMX;
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break;
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case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
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break;
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}
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assert(xm & DP_HIDDEN_BIT);
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assert(ym & DP_HIDDEN_BIT);
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/* provide rounding space */
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xm <<= 3;
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ym <<= 3;
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{
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/* now the dirty work */
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u64 rm = 0;
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int re = xe - ye;
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u64 bm;
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for (bm = DP_MBIT(DP_MBITS + 2); bm; bm >>= 1) {
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if (xm >= ym) {
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xm -= ym;
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rm |= bm;
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if (xm == 0)
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break;
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}
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xm <<= 1;
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}
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rm <<= 1;
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if (xm)
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rm |= 1; /* have remainder, set sticky */
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assert(rm);
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/* normalise rm to rounding precision ?
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*/
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while ((rm >> (DP_MBITS + 3)) == 0) {
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rm <<= 1;
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re--;
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}
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DPNORMRET2(xs == ys ? 0 : 1, re, rm, "div", x, y);
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}
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}
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