| /* IEEE754 floating point arithmetic |
| * single precision square root |
| */ |
| /* |
| * MIPS floating point support |
| * Copyright (C) 1994-2000 Algorithmics Ltd. |
| * |
| * This program is free software; you can distribute it and/or modify it |
| * under the terms of the GNU General Public License (Version 2) as |
| * published by the Free Software Foundation. |
| * |
| * This program is distributed in the hope it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * for more details. |
| * |
| * You should have received a copy of the GNU General Public License along |
| * with this program; if not, write to the Free Software Foundation, Inc., |
| * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| */ |
| |
| #include "ieee754sp.h" |
| |
| union ieee754sp ieee754sp_sqrt(union ieee754sp x) |
| { |
| int ix, s, q, m, t, i; |
| unsigned int r; |
| COMPXSP; |
| |
| /* take care of Inf and NaN */ |
| |
| EXPLODEXSP; |
| ieee754_clearcx(); |
| FLUSHXSP; |
| |
| /* x == INF or NAN? */ |
| switch (xc) { |
| case IEEE754_CLASS_QNAN: |
| /* sqrt(Nan) = Nan */ |
| return ieee754sp_nanxcpt(x); |
| |
| case IEEE754_CLASS_SNAN: |
| ieee754_setcx(IEEE754_INVALID_OPERATION); |
| return ieee754sp_nanxcpt(ieee754sp_indef()); |
| |
| case IEEE754_CLASS_ZERO: |
| /* sqrt(0) = 0 */ |
| return x; |
| |
| case IEEE754_CLASS_INF: |
| if (xs) { |
| /* sqrt(-Inf) = Nan */ |
| ieee754_setcx(IEEE754_INVALID_OPERATION); |
| return ieee754sp_nanxcpt(ieee754sp_indef()); |
| } |
| /* sqrt(+Inf) = Inf */ |
| return x; |
| |
| case IEEE754_CLASS_DNORM: |
| case IEEE754_CLASS_NORM: |
| if (xs) { |
| /* sqrt(-x) = Nan */ |
| ieee754_setcx(IEEE754_INVALID_OPERATION); |
| return ieee754sp_nanxcpt(ieee754sp_indef()); |
| } |
| break; |
| } |
| |
| ix = x.bits; |
| |
| /* normalize x */ |
| m = (ix >> 23); |
| if (m == 0) { /* subnormal x */ |
| for (i = 0; (ix & 0x00800000) == 0; i++) |
| ix <<= 1; |
| m -= i - 1; |
| } |
| m -= 127; /* unbias exponent */ |
| ix = (ix & 0x007fffff) | 0x00800000; |
| if (m & 1) /* odd m, double x to make it even */ |
| ix += ix; |
| m >>= 1; /* m = [m/2] */ |
| |
| /* generate sqrt(x) bit by bit */ |
| ix += ix; |
| q = s = 0; /* q = sqrt(x) */ |
| r = 0x01000000; /* r = moving bit from right to left */ |
| |
| while (r != 0) { |
| t = s + r; |
| if (t <= ix) { |
| s = t + r; |
| ix -= t; |
| q += r; |
| } |
| ix += ix; |
| r >>= 1; |
| } |
| |
| if (ix != 0) { |
| ieee754_setcx(IEEE754_INEXACT); |
| switch (ieee754_csr.rm) { |
| case IEEE754_RP: |
| q += 2; |
| break; |
| case IEEE754_RN: |
| q += (q & 1); |
| break; |
| } |
| } |
| ix = (q >> 1) + 0x3f000000; |
| ix += (m << 23); |
| x.bits = ix; |
| return x; |
| } |