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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.,
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <linux/compiler.h>
#include "ieee754sp.h"
int ieee754sp_class(union ieee754sp x)
{
COMPXSP;
EXPLODEXSP;
return xc;
}
int ieee754sp_isnan(union ieee754sp x)
{
return ieee754sp_class(x) >= IEEE754_CLASS_SNAN;
}
static inline int ieee754sp_issnan(union ieee754sp x)
{
assert(ieee754sp_isnan(x));
return SPMANT(x) & SP_MBIT(SP_FBITS - 1);
}
union ieee754sp __cold ieee754sp_nanxcpt(union ieee754sp r)
{
assert(ieee754sp_isnan(r));
if (!ieee754sp_issnan(r)) /* QNAN does not cause invalid op !! */
return r;
if (!ieee754_setandtestcx(IEEE754_INVALID_OPERATION)) {
/* not enabled convert to a quiet NaN */
SPMANT(r) &= (~SP_MBIT(SP_FBITS-1));
if (ieee754sp_isnan(r))
return r;
else
return ieee754sp_indef();
}
return r;
}
static unsigned ieee754sp_get_rounding(int sn, unsigned xm)
{
/* inexact must round of 3 bits
*/
if (xm & (SP_MBIT(3) - 1)) {
switch (ieee754_csr.rm) {
case FPU_CSR_RZ:
break;
case FPU_CSR_RN:
xm += 0x3 + ((xm >> 3) & 1);
/* xm += (xm&0x8)?0x4:0x3 */
break;
case FPU_CSR_RU: /* toward +Infinity */
if (!sn) /* ?? */
xm += 0x8;
break;
case FPU_CSR_RD: /* toward -Infinity */
if (sn) /* ?? */
xm += 0x8;
break;
}
}
return xm;
}
/* generate a normal/denormal number with over,under handling
* sn is sign
* xe is an unbiased exponent
* xm is 3bit extended precision value.
*/
union ieee754sp ieee754sp_format(int sn, int xe, unsigned xm)
{
assert(xm); /* we don't gen exact zeros (probably should) */
assert((xm >> (SP_FBITS + 1 + 3)) == 0); /* no execess */
assert(xm & (SP_HIDDEN_BIT << 3));
if (xe < SP_EMIN) {
/* strip lower bits */
int es = SP_EMIN - xe;
if (ieee754_csr.nod) {
ieee754_setcx(IEEE754_UNDERFLOW);
ieee754_setcx(IEEE754_INEXACT);
switch(ieee754_csr.rm) {
case FPU_CSR_RN:
case FPU_CSR_RZ:
return ieee754sp_zero(sn);
case FPU_CSR_RU: /* toward +Infinity */
if (sn == 0)
return ieee754sp_min(0);
else
return ieee754sp_zero(1);
case FPU_CSR_RD: /* toward -Infinity */
if (sn == 0)
return ieee754sp_zero(0);
else
return ieee754sp_min(1);
}
}
if (xe == SP_EMIN - 1 &&
ieee754sp_get_rounding(sn, xm) >> (SP_FBITS + 1 + 3))
{
/* Not tiny after rounding */
ieee754_setcx(IEEE754_INEXACT);
xm = ieee754sp_get_rounding(sn, xm);
xm >>= 1;
/* Clear grs bits */
xm &= ~(SP_MBIT(3) - 1);
xe++;
} else {
/* sticky right shift es bits
*/
SPXSRSXn(es);
assert((xm & (SP_HIDDEN_BIT << 3)) == 0);
assert(xe == SP_EMIN);
}
}
if (xm & (SP_MBIT(3) - 1)) {
ieee754_setcx(IEEE754_INEXACT);
if ((xm & (SP_HIDDEN_BIT << 3)) == 0) {
ieee754_setcx(IEEE754_UNDERFLOW);
}
/* inexact must round of 3 bits
*/
xm = ieee754sp_get_rounding(sn, xm);
/* adjust exponent for rounding add overflowing
*/
if (xm >> (SP_FBITS + 1 + 3)) {
/* add causes mantissa overflow */
xm >>= 1;
xe++;
}
}
/* strip grs bits */
xm >>= 3;
assert((xm >> (SP_FBITS + 1)) == 0); /* no execess */
assert(xe >= SP_EMIN);
if (xe > SP_EMAX) {
ieee754_setcx(IEEE754_OVERFLOW);
ieee754_setcx(IEEE754_INEXACT);
/* -O can be table indexed by (rm,sn) */
switch (ieee754_csr.rm) {
case FPU_CSR_RN:
return ieee754sp_inf(sn);
case FPU_CSR_RZ:
return ieee754sp_max(sn);
case FPU_CSR_RU: /* toward +Infinity */
if (sn == 0)
return ieee754sp_inf(0);
else
return ieee754sp_max(1);
case FPU_CSR_RD: /* toward -Infinity */
if (sn == 0)
return ieee754sp_max(0);
else
return ieee754sp_inf(1);
}
}
/* gen norm/denorm/zero */
if ((xm & SP_HIDDEN_BIT) == 0) {
/* we underflow (tiny/zero) */
assert(xe == SP_EMIN);
if (ieee754_csr.mx & IEEE754_UNDERFLOW)
ieee754_setcx(IEEE754_UNDERFLOW);
return buildsp(sn, SP_EMIN - 1 + SP_EBIAS, xm);
} else {
assert((xm >> (SP_FBITS + 1)) == 0); /* no execess */
assert(xm & SP_HIDDEN_BIT);
return buildsp(sn, xe + SP_EBIAS, xm & ~SP_HIDDEN_BIT);
}
}
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