sp_modf.c
1.97 KB
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/* IEEE754 floating point arithmetic
* single precision
*/
/*
* 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.,
* 59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
*
* ########################################################################
*/
#include "ieee754sp.h"
/* modf function is always exact for a finite number
*/
ieee754sp ieee754sp_modf(ieee754sp x, ieee754sp *ip)
{
COMPXSP;
CLEARCX;
EXPLODEXSP;
switch (xc) {
case IEEE754_CLASS_SNAN:
case IEEE754_CLASS_QNAN:
case IEEE754_CLASS_INF:
case IEEE754_CLASS_ZERO:
*ip = x;
return x;
case IEEE754_CLASS_DNORM:
/* far to small */
*ip = ieee754sp_zero(xs);
return x;
case IEEE754_CLASS_NORM:
break;
}
if (xe < 0) {
*ip = ieee754sp_zero(xs);
return x;
}
if (xe >= SP_MBITS) {
*ip = x;
return ieee754sp_zero(xs);
}
/* generate ipart mantissa by clearing bottom bits
*/
*ip = buildsp(xs, xe + SP_EBIAS,
((xm >> (SP_MBITS - xe)) << (SP_MBITS - xe)) &
~SP_HIDDEN_BIT);
/* generate fpart mantissa by clearing top bits
* and normalizing (must be able to normalize)
*/
xm = (xm << (32 - (SP_MBITS - xe))) >> (32 - (SP_MBITS - xe));
if (xm == 0)
return ieee754sp_zero(xs);
while ((xm >> SP_MBITS) == 0) {
xm <<= 1;
xe--;
}
return buildsp(xs, xe + SP_EBIAS, xm & ~SP_HIDDEN_BIT);
}