![Ralf Baechle](/assets/img/avatar_default.png)
Previously math-emu was using the IEEE-754 constants internally. These were differing by having the constants for rounding to +/- infinity switched, so a conversion was necessary. This would be entirely avoidable if the MIPS constants were used throughout, so get rid of the bloat. Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
183 lines
4.5 KiB
C
183 lines
4.5 KiB
C
/* 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.,
|
|
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
|
|
*/
|
|
|
|
#include "ieee754sp.h"
|
|
|
|
union ieee754sp ieee754sp_sub(union ieee754sp x, union ieee754sp y)
|
|
{
|
|
int s;
|
|
|
|
COMPXSP;
|
|
COMPYSP;
|
|
|
|
EXPLODEXSP;
|
|
EXPLODEYSP;
|
|
|
|
ieee754_clearcx();
|
|
|
|
FLUSHXSP;
|
|
FLUSHYSP;
|
|
|
|
switch (CLPAIR(xc, yc)) {
|
|
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
|
|
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
|
|
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
|
|
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
|
|
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
|
|
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
|
|
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
|
|
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
|
|
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
|
|
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
|
|
case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
|
|
ieee754_setcx(IEEE754_INVALID_OPERATION);
|
|
return ieee754sp_nanxcpt(ieee754sp_indef());
|
|
|
|
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
|
|
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
|
|
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
|
|
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
|
|
return y;
|
|
|
|
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
|
|
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
|
|
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
|
|
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
|
|
case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
|
|
return x;
|
|
|
|
|
|
/*
|
|
* Infinity handling
|
|
*/
|
|
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
|
|
if (xs != ys)
|
|
return x;
|
|
ieee754_setcx(IEEE754_INVALID_OPERATION);
|
|
return ieee754sp_indef();
|
|
|
|
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
|
|
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
|
|
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
|
|
return ieee754sp_inf(ys ^ 1);
|
|
|
|
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
|
|
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
|
|
case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
|
|
return x;
|
|
|
|
/*
|
|
* Zero handling
|
|
*/
|
|
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
|
|
if (xs != ys)
|
|
return x;
|
|
else
|
|
return ieee754sp_zero(ieee754_csr.rm == FPU_CSR_RD);
|
|
|
|
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
|
|
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
|
|
return x;
|
|
|
|
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
|
|
case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
|
|
/* quick fix up */
|
|
SPSIGN(y) ^= 1;
|
|
return y;
|
|
|
|
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
|
|
SPDNORMX;
|
|
|
|
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
|
|
SPDNORMY;
|
|
break;
|
|
|
|
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
|
|
SPDNORMX;
|
|
break;
|
|
|
|
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
|
|
break;
|
|
}
|
|
/* flip sign of y and handle as add */
|
|
ys ^= 1;
|
|
|
|
assert(xm & SP_HIDDEN_BIT);
|
|
assert(ym & SP_HIDDEN_BIT);
|
|
|
|
|
|
/* provide guard,round and stick bit space */
|
|
xm <<= 3;
|
|
ym <<= 3;
|
|
|
|
if (xe > ye) {
|
|
/*
|
|
* have to shift y fraction right to align
|
|
*/
|
|
s = xe - ye;
|
|
SPXSRSYn(s);
|
|
} else if (ye > xe) {
|
|
/*
|
|
* have to shift x fraction right to align
|
|
*/
|
|
s = ye - xe;
|
|
SPXSRSXn(s);
|
|
}
|
|
assert(xe == ye);
|
|
assert(xe <= SP_EMAX);
|
|
|
|
if (xs == ys) {
|
|
/* generate 28 bit result of adding two 27 bit numbers
|
|
*/
|
|
xm = xm + ym;
|
|
xe = xe;
|
|
xs = xs;
|
|
|
|
if (xm >> (SP_FBITS + 1 + 3)) { /* carry out */
|
|
SPXSRSX1(); /* shift preserving sticky */
|
|
}
|
|
} else {
|
|
if (xm >= ym) {
|
|
xm = xm - ym;
|
|
xe = xe;
|
|
xs = xs;
|
|
} else {
|
|
xm = ym - xm;
|
|
xe = xe;
|
|
xs = ys;
|
|
}
|
|
if (xm == 0) {
|
|
if (ieee754_csr.rm == FPU_CSR_RD)
|
|
return ieee754sp_zero(1); /* round negative inf. => sign = -1 */
|
|
else
|
|
return ieee754sp_zero(0); /* other round modes => sign = 1 */
|
|
}
|
|
/* normalize to rounding precision
|
|
*/
|
|
while ((xm >> (SP_FBITS + 3)) == 0) {
|
|
xm <<= 1;
|
|
xe--;
|
|
}
|
|
}
|
|
|
|
return ieee754sp_format(xs, xe, xm);
|
|
}
|