115 lines
2.4 KiB
C
115 lines
2.4 KiB
C
/* 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_SNAN:
|
|
return ieee754sp_nanxcpt(x);
|
|
|
|
case IEEE754_CLASS_QNAN:
|
|
/* sqrt(Nan) = Nan */
|
|
return x;
|
|
|
|
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_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_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 FPU_CSR_RU:
|
|
q += 2;
|
|
break;
|
|
case FPU_CSR_RN:
|
|
q += (q & 1);
|
|
break;
|
|
}
|
|
}
|
|
ix = (q >> 1) + 0x3f000000;
|
|
ix += (m << 23);
|
|
x.bits = ix;
|
|
return x;
|
|
}
|