1 /* IEEE754 floating point arithmetic 2 * single precision square root 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 "ieee754sp.h" 29 30 ieee754sp ieee754sp_sqrt(ieee754sp x) 31 { 32 int ix, s, q, m, t, i; 33 unsigned int r; 34 COMPXSP; 35 36 /* take care of Inf and NaN */ 37 38 EXPLODEXSP; 39 CLEARCX; 40 FLUSHXSP; 41 42 /* x == INF or NAN? */ 43 switch (xc) { 44 case IEEE754_CLASS_QNAN: 45 /* sqrt(Nan) = Nan */ 46 return ieee754sp_nanxcpt(x, "sqrt"); 47 case IEEE754_CLASS_SNAN: 48 SETCX(IEEE754_INVALID_OPERATION); 49 return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt"); 50 case IEEE754_CLASS_ZERO: 51 /* sqrt(0) = 0 */ 52 return x; 53 case IEEE754_CLASS_INF: 54 if (xs) { 55 /* sqrt(-Inf) = Nan */ 56 SETCX(IEEE754_INVALID_OPERATION); 57 return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt"); 58 } 59 /* sqrt(+Inf) = Inf */ 60 return x; 61 case IEEE754_CLASS_DNORM: 62 case IEEE754_CLASS_NORM: 63 if (xs) { 64 /* sqrt(-x) = Nan */ 65 SETCX(IEEE754_INVALID_OPERATION); 66 return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt"); 67 } 68 break; 69 } 70 71 ix = x.bits; 72 73 /* normalize x */ 74 m = (ix >> 23); 75 if (m == 0) { /* subnormal x */ 76 for (i = 0; (ix & 0x00800000) == 0; i++) 77 ix <<= 1; 78 m -= i - 1; 79 } 80 m -= 127; /* unbias exponent */ 81 ix = (ix & 0x007fffff) | 0x00800000; 82 if (m & 1) /* odd m, double x to make it even */ 83 ix += ix; 84 m >>= 1; /* m = [m/2] */ 85 86 /* generate sqrt(x) bit by bit */ 87 ix += ix; 88 q = s = 0; /* q = sqrt(x) */ 89 r = 0x01000000; /* r = moving bit from right to left */ 90 91 while (r != 0) { 92 t = s + r; 93 if (t <= ix) { 94 s = t + r; 95 ix -= t; 96 q += r; 97 } 98 ix += ix; 99 r >>= 1; 100 } 101 102 if (ix != 0) { 103 SETCX(IEEE754_INEXACT); 104 switch (ieee754_csr.rm) { 105 case IEEE754_RP: 106 q += 2; 107 break; 108 case IEEE754_RN: 109 q += (q & 1); 110 break; 111 } 112 } 113 ix = (q >> 1) + 0x3f000000; 114 ix += (m << 23); 115 x.bits = ix; 116 return x; 117 } 118