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 * 8 * ######################################################################## 9 * 10 * This program is free software; you can distribute it and/or modify it 11 * under the terms of the GNU General Public License (Version 2) as 12 * published by the Free Software Foundation. 13 * 14 * This program is distributed in the hope it will be useful, but WITHOUT 15 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 16 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 17 * for more details. 18 * 19 * You should have received a copy of the GNU General Public License along 20 * with this program; if not, write to the Free Software Foundation, Inc., 21 * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA. 22 * 23 * ######################################################################## 24 */ 25 26 27 #include "ieee754sp.h" 28 29 union ieee754sp ieee754sp_sqrt(union ieee754sp x) 30 { 31 int ix, s, q, m, t, i; 32 unsigned int r; 33 COMPXSP; 34 35 /* take care of Inf and NaN */ 36 37 EXPLODEXSP; 38 ieee754_clearcx(); 39 FLUSHXSP; 40 41 /* x == INF or NAN? */ 42 switch (xc) { 43 case IEEE754_CLASS_QNAN: 44 /* sqrt(Nan) = Nan */ 45 return ieee754sp_nanxcpt(x, "sqrt"); 46 case IEEE754_CLASS_SNAN: 47 ieee754_setcx(IEEE754_INVALID_OPERATION); 48 return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt"); 49 case IEEE754_CLASS_ZERO: 50 /* sqrt(0) = 0 */ 51 return x; 52 case IEEE754_CLASS_INF: 53 if (xs) { 54 /* sqrt(-Inf) = Nan */ 55 ieee754_setcx(IEEE754_INVALID_OPERATION); 56 return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt"); 57 } 58 /* sqrt(+Inf) = Inf */ 59 return x; 60 case IEEE754_CLASS_DNORM: 61 case IEEE754_CLASS_NORM: 62 if (xs) { 63 /* sqrt(-x) = Nan */ 64 ieee754_setcx(IEEE754_INVALID_OPERATION); 65 return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt"); 66 } 67 break; 68 } 69 70 ix = x.bits; 71 72 /* normalize x */ 73 m = (ix >> 23); 74 if (m == 0) { /* subnormal x */ 75 for (i = 0; (ix & 0x00800000) == 0; i++) 76 ix <<= 1; 77 m -= i - 1; 78 } 79 m -= 127; /* unbias exponent */ 80 ix = (ix & 0x007fffff) | 0x00800000; 81 if (m & 1) /* odd m, double x to make it even */ 82 ix += ix; 83 m >>= 1; /* m = [m/2] */ 84 85 /* generate sqrt(x) bit by bit */ 86 ix += ix; 87 q = s = 0; /* q = sqrt(x) */ 88 r = 0x01000000; /* r = moving bit from right to left */ 89 90 while (r != 0) { 91 t = s + r; 92 if (t <= ix) { 93 s = t + r; 94 ix -= t; 95 q += r; 96 } 97 ix += ix; 98 r >>= 1; 99 } 100 101 if (ix != 0) { 102 ieee754_setcx(IEEE754_INEXACT); 103 switch (ieee754_csr.rm) { 104 case IEEE754_RP: 105 q += 2; 106 break; 107 case IEEE754_RN: 108 q += (q & 1); 109 break; 110 } 111 } 112 ix = (q >> 1) + 0x3f000000; 113 ix += (m << 23); 114 x.bits = ix; 115 return x; 116 } 117