1/* IEEE754 floating point arithmetic 2 * double precision: common utilities 3 */ 4/* 5 * MIPS floating point support 6 * Copyright (C) 1994-2000 Algorithmics Ltd. 7 * http://www.algor.co.uk 8 * 9 * ######################################################################## 10 * 11 * This program is free software; you can distribute it and/or modify it 12 * under the terms of the GNU General Public License (Version 2) as 13 * published by the Free Software Foundation. 14 * 15 * This program is distributed in the hope it will be useful, but WITHOUT 16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 17 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 18 * for more details. 19 * 20 * You should have received a copy of the GNU General Public License along 21 * with this program; if not, write to the Free Software Foundation, Inc., 22 * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA. 23 * 24 * ######################################################################## 25 */ 26 27 28#include "ieee754dp.h" 29 30/* modf function is always exact for a finite number 31*/ 32ieee754dp ieee754dp_modf(ieee754dp x, ieee754dp * ip) 33{ 34 COMPXDP; 35 36 CLEARCX; 37 38 EXPLODEXDP; 39 40 switch (xc) { 41 case IEEE754_CLASS_SNAN: 42 case IEEE754_CLASS_QNAN: 43 case IEEE754_CLASS_INF: 44 case IEEE754_CLASS_ZERO: 45 *ip = x; 46 return x; 47 case IEEE754_CLASS_DNORM: 48 /* far to small */ 49 *ip = ieee754dp_zero(xs); 50 return x; 51 case IEEE754_CLASS_NORM: 52 break; 53 } 54 if (xe < 0) { 55 *ip = ieee754dp_zero(xs); 56 return x; 57 } 58 if (xe >= DP_MBITS) { 59 *ip = x; 60 return ieee754dp_zero(xs); 61 } 62 /* generate ipart mantissa by clearing bottom bits 63 */ 64 *ip = builddp(xs, xe + DP_EBIAS, 65 ((xm >> (DP_MBITS - xe)) << (DP_MBITS - xe)) & 66 ~DP_HIDDEN_BIT); 67 68 /* generate fpart mantissa by clearing top bits 69 * and normalizing (must be able to normalize) 70 */ 71 xm = (xm << (64 - (DP_MBITS - xe))) >> (64 - (DP_MBITS - xe)); 72 if (xm == 0) 73 return ieee754dp_zero(xs); 74 75 while ((xm >> DP_MBITS) == 0) { 76 xm <<= 1; 77 xe--; 78 } 79 return builddp(xs, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT); 80} 81