![Linus Torvalds](/assets/img/avatar_default.png)
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
192 lines
4.9 KiB
C
192 lines
4.9 KiB
C
/* IEEE754 floating point arithmetic
|
|
* double precision: common utilities
|
|
*/
|
|
/*
|
|
* 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 "ieee754dp.h"
|
|
|
|
ieee754dp ieee754dp_sub(ieee754dp x, ieee754dp y)
|
|
{
|
|
COMPXDP;
|
|
COMPYDP;
|
|
|
|
EXPLODEXDP;
|
|
EXPLODEYDP;
|
|
|
|
CLEARCX;
|
|
|
|
FLUSHXDP;
|
|
FLUSHYDP;
|
|
|
|
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):
|
|
SETCX(IEEE754_INVALID_OPERATION);
|
|
return ieee754dp_nanxcpt(ieee754dp_indef(), "sub", x, y);
|
|
|
|
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;
|
|
SETCX(IEEE754_INVALID_OPERATION);
|
|
return ieee754dp_xcpt(ieee754dp_indef(), "sub", x, y);
|
|
|
|
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 ieee754dp_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 ieee754dp_zero(ieee754_csr.rm ==
|
|
IEEE754_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 */
|
|
DPSIGN(y) ^= 1;
|
|
return y;
|
|
|
|
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
|
|
DPDNORMX;
|
|
/* FAAL THOROUGH */
|
|
|
|
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
|
|
/* normalize ym,ye */
|
|
DPDNORMY;
|
|
break;
|
|
|
|
case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
|
|
/* normalize xm,xe */
|
|
DPDNORMX;
|
|
break;
|
|
|
|
case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
|
|
break;
|
|
}
|
|
/* flip sign of y and handle as add */
|
|
ys ^= 1;
|
|
|
|
assert(xm & DP_HIDDEN_BIT);
|
|
assert(ym & DP_HIDDEN_BIT);
|
|
|
|
|
|
/* provide guard,round and stick bit dpace */
|
|
xm <<= 3;
|
|
ym <<= 3;
|
|
|
|
if (xe > ye) {
|
|
/* have to shift y fraction right to align
|
|
*/
|
|
int s = xe - ye;
|
|
ym = XDPSRS(ym, s);
|
|
ye += s;
|
|
} else if (ye > xe) {
|
|
/* have to shift x fraction right to align
|
|
*/
|
|
int s = ye - xe;
|
|
xm = XDPSRS(xm, s);
|
|
xe += s;
|
|
}
|
|
assert(xe == ye);
|
|
assert(xe <= DP_EMAX);
|
|
|
|
if (xs == ys) {
|
|
/* generate 28 bit result of adding two 27 bit numbers
|
|
*/
|
|
xm = xm + ym;
|
|
xe = xe;
|
|
xs = xs;
|
|
|
|
if (xm >> (DP_MBITS + 1 + 3)) { /* carry out */
|
|
xm = XDPSRS1(xm); /* shift preserving sticky */
|
|
xe++;
|
|
}
|
|
} 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 == IEEE754_RD)
|
|
return ieee754dp_zero(1); /* round negative inf. => sign = -1 */
|
|
else
|
|
return ieee754dp_zero(0); /* other round modes => sign = 1 */
|
|
}
|
|
|
|
/* normalize to rounding precision
|
|
*/
|
|
while ((xm >> (DP_MBITS + 3)) == 0) {
|
|
xm <<= 1;
|
|
xe--;
|
|
}
|
|
}
|
|
DPNORMRET2(xs, xe, xm, "sub", x, y);
|
|
}
|