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// SPDX-License-Identifier: GPL-2.0-only
/* IEEE754 floating point arithmetic
* double precision: common utilities
*/
/*
* MIPS floating point support
* Copyright (C) 1994-2000 Algorithmics Ltd.
*/
#include <linux/compiler.h>
#include "ieee754dp.h"
int ieee754dp_class(union ieee754dp x)
{
COMPXDP;
EXPLODEXDP;
return xc;
}
static inline int ieee754dp_isnan(union ieee754dp x)
{
return ieee754_class_nan(ieee754dp_class(x));
}
static inline int ieee754dp_issnan(union ieee754dp x)
{
int qbit;
assert(ieee754dp_isnan(x));
qbit = (DPMANT(x) & DP_MBIT(DP_FBITS - 1)) == DP_MBIT(DP_FBITS - 1);
return ieee754_csr.nan2008 ^ qbit;
}
/*
* Raise the Invalid Operation IEEE 754 exception
* and convert the signaling NaN supplied to a quiet NaN.
*/
union ieee754dp __cold ieee754dp_nanxcpt(union ieee754dp r)
{
assert(ieee754dp_issnan(r));
ieee754_setcx(IEEE754_INVALID_OPERATION);
if (ieee754_csr.nan2008) {
DPMANT(r) |= DP_MBIT(DP_FBITS - 1);
} else {
DPMANT(r) &= ~DP_MBIT(DP_FBITS - 1);
if (!ieee754dp_isnan(r))
DPMANT(r) |= DP_MBIT(DP_FBITS - 2);
}
return r;
}
static u64 ieee754dp_get_rounding(int sn, u64 xm)
{
/* inexact must round of 3 bits
*/
if (xm & (DP_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 ieee754dp ieee754dp_format(int sn, int xe, u64 xm)
{
assert(xm); /* we don't gen exact zeros (probably should) */
assert((xm >> (DP_FBITS + 1 + 3)) == 0); /* no excess */
assert(xm & (DP_HIDDEN_BIT << 3));
if (xe < DP_EMIN) {
/* strip lower bits */
int es = DP_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 ieee754dp_zero(sn);
case FPU_CSR_RU: /* toward +Infinity */
if (sn == 0)
return ieee754dp_min(0);
else
return ieee754dp_zero(1);
case FPU_CSR_RD: /* toward -Infinity */
if (sn == 0)
return ieee754dp_zero(0);
else
return ieee754dp_min(1);
}
}
if (xe == DP_EMIN - 1 &&
ieee754dp_get_rounding(sn, xm) >> (DP_FBITS + 1 + 3))
{
/* Not tiny after rounding */
ieee754_setcx(IEEE754_INEXACT);
xm = ieee754dp_get_rounding(sn, xm);
xm >>= 1;
/* Clear grs bits */
xm &= ~(DP_MBIT(3) - 1);
xe++;
}
else {
/* sticky right shift es bits
*/
xm = XDPSRS(xm, es);
xe += es;
assert((xm & (DP_HIDDEN_BIT << 3)) == 0);
assert(xe == DP_EMIN);
}
}
if (xm & (DP_MBIT(3) - 1)) {
ieee754_setcx(IEEE754_INEXACT);
if ((xm & (DP_HIDDEN_BIT << 3)) == 0) {
ieee754_setcx(IEEE754_UNDERFLOW);
}
/* inexact must round of 3 bits
*/
xm = ieee754dp_get_rounding(sn, xm);
/* adjust exponent for rounding add overflowing
*/
if (xm >> (DP_FBITS + 3 + 1)) {
/* add causes mantissa overflow */
xm >>= 1;
xe++;
}
}
/* strip grs bits */
xm >>= 3;
assert((xm >> (DP_FBITS + 1)) == 0); /* no excess */
assert(xe >= DP_EMIN);
if (xe > DP_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 ieee754dp_inf(sn);
case FPU_CSR_RZ:
return ieee754dp_max(sn);
case FPU_CSR_RU: /* toward +Infinity */
if (sn == 0)
return ieee754dp_inf(0);
else
return ieee754dp_max(1);
case FPU_CSR_RD: /* toward -Infinity */
if (sn == 0)
return ieee754dp_max(0);
else
return ieee754dp_inf(1);
}
}
/* gen norm/denorm/zero */
if ((xm & DP_HIDDEN_BIT) == 0) {
/* we underflow (tiny/zero) */
assert(xe == DP_EMIN);
if (ieee754_csr.mx & IEEE754_UNDERFLOW)
ieee754_setcx(IEEE754_UNDERFLOW);
return builddp(sn, DP_EMIN - 1 + DP_EBIAS, xm);
} else {
assert((xm >> (DP_FBITS + 1)) == 0); /* no excess */
assert(xm & DP_HIDDEN_BIT);
return builddp(sn, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT);
}
}
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