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[/] [or1k_soc_on_altera_embedded_dev_kit/] [trunk/] [linux-2.6/] [linux-2.6.24/] [arch/] [mips/] [math-emu/] [sp_sqrt.c] - Rev 3
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/* IEEE754 floating point arithmetic * single precision square root */ /* * MIPS floating point support * Copyright (C) 1994-2000 Algorithmics Ltd. * http://www.algor.co.uk * * ######################################################################## * * 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., * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA. * * ######################################################################## */ #include "ieee754sp.h" ieee754sp ieee754sp_sqrt(ieee754sp x) { int ix, s, q, m, t, i; unsigned int r; COMPXSP; /* take care of Inf and NaN */ EXPLODEXSP; CLEARCX; FLUSHXSP; /* x == INF or NAN? */ switch (xc) { case IEEE754_CLASS_QNAN: /* sqrt(Nan) = Nan */ return ieee754sp_nanxcpt(x, "sqrt"); case IEEE754_CLASS_SNAN: SETCX(IEEE754_INVALID_OPERATION); return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt"); case IEEE754_CLASS_ZERO: /* sqrt(0) = 0 */ return x; case IEEE754_CLASS_INF: if (xs) { /* sqrt(-Inf) = Nan */ SETCX(IEEE754_INVALID_OPERATION); return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt"); } /* sqrt(+Inf) = Inf */ return x; case IEEE754_CLASS_DNORM: case IEEE754_CLASS_NORM: if (xs) { /* sqrt(-x) = Nan */ SETCX(IEEE754_INVALID_OPERATION); return ieee754sp_nanxcpt(ieee754sp_indef(), "sqrt"); } 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) { 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; }