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/* Copyright (C) 2007-2022 Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.
GCC is distributed in the hope that 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.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
/*****************************************************************************
*
* BID128 fma x * y + z
*
****************************************************************************/
#include "bid_internal.h"
static void
rounding_correction (unsigned int rnd_mode,
unsigned int is_inexact_lt_midpoint,
unsigned int is_inexact_gt_midpoint,
unsigned int is_midpoint_lt_even,
unsigned int is_midpoint_gt_even,
int unbexp,
UINT128 * ptrres, _IDEC_flags * ptrfpsf) {
// unbiased true exponent unbexp may be larger than emax
UINT128 res = *ptrres; // expected to have the correct sign and coefficient
// (the exponent field is ignored, as unbexp is used instead)
UINT64 sign, exp;
UINT64 C_hi, C_lo;
// general correction from RN to RA, RM, RP, RZ
// Note: if the result is negative, then is_inexact_lt_midpoint,
// is_inexact_gt_midpoint, is_midpoint_lt_even, and is_midpoint_gt_even
// have to be considered as if determined for the absolute value of the
// result (so they seem to be reversed)
if (is_inexact_lt_midpoint || is_inexact_gt_midpoint ||
is_midpoint_lt_even || is_midpoint_gt_even) {
*ptrfpsf |= INEXACT_EXCEPTION;
}
// apply correction to result calculated with unbounded exponent
sign = res.w[1] & MASK_SIGN;
exp = (UINT64) (unbexp + 6176) << 49; // valid only if expmin<=unbexp<=expmax
C_hi = res.w[1] & MASK_COEFF;
C_lo = res.w[0];
if ((!sign && ((rnd_mode == ROUNDING_UP && is_inexact_lt_midpoint) ||
((rnd_mode == ROUNDING_TIES_AWAY || rnd_mode == ROUNDING_UP) &&
is_midpoint_gt_even))) ||
(sign && ((rnd_mode == ROUNDING_DOWN && is_inexact_lt_midpoint) ||
((rnd_mode == ROUNDING_TIES_AWAY || rnd_mode == ROUNDING_DOWN) &&
is_midpoint_gt_even)))) {
// C = C + 1
C_lo = C_lo + 1;
if (C_lo == 0)
C_hi = C_hi + 1;
if (C_hi == 0x0001ed09bead87c0ull && C_lo == 0x378d8e6400000000ull) {
// C = 10^34 => rounding overflow
C_hi = 0x0000314dc6448d93ull;
C_lo = 0x38c15b0a00000000ull; // 10^33
// exp = exp + EXP_P1;
unbexp = unbexp + 1;
exp = (UINT64) (unbexp + 6176) << 49;
}
} else if ((is_midpoint_lt_even || is_inexact_gt_midpoint) &&
((sign && (rnd_mode == ROUNDING_UP || rnd_mode == ROUNDING_TO_ZERO)) ||
(!sign && (rnd_mode == ROUNDING_DOWN || rnd_mode == ROUNDING_TO_ZERO)))) {
// C = C - 1
C_lo = C_lo - 1;
if (C_lo == 0xffffffffffffffffull)
C_hi--;
// check if we crossed into the lower decade
if (C_hi == 0x0000314dc6448d93ull && C_lo == 0x38c15b09ffffffffull) {
// C = 10^33 - 1
if (exp > 0) {
C_hi = 0x0001ed09bead87c0ull; // 10^34 - 1
C_lo = 0x378d8e63ffffffffull;
// exp = exp - EXP_P1;
unbexp = unbexp - 1;
exp = (UINT64) (unbexp + 6176) << 49;
} else { // if exp = 0 the result is tiny & inexact
*ptrfpsf |= UNDERFLOW_EXCEPTION;
}
}
} else {
; // the result is already correct
}
if (unbexp > expmax) { // 6111
*ptrfpsf |= (INEXACT_EXCEPTION | OVERFLOW_EXCEPTION);
exp = 0;
if (!sign) { // result is positive
if (rnd_mode == ROUNDING_UP || rnd_mode == ROUNDING_TIES_AWAY) { // +inf
C_hi = 0x7800000000000000ull;
C_lo = 0x0000000000000000ull;
} else { // res = +MAXFP = (10^34-1) * 10^emax
C_hi = 0x5fffed09bead87c0ull;
C_lo = 0x378d8e63ffffffffull;
}
} else { // result is negative
if (rnd_mode == ROUNDING_DOWN || rnd_mode == ROUNDING_TIES_AWAY) { // -inf
C_hi = 0xf800000000000000ull;
C_lo = 0x0000000000000000ull;
} else { // res = -MAXFP = -(10^34-1) * 10^emax
C_hi = 0xdfffed09bead87c0ull;
C_lo = 0x378d8e63ffffffffull;
}
}
}
// assemble the result
res.w[1] = sign | exp | C_hi;
res.w[0] = C_lo;
*ptrres = res;
}
static void
add256 (UINT256 x, UINT256 y, UINT256 * pz) {
// *z = x + yl assume the sum fits in 256 bits
UINT256 z;
z.w[0] = x.w[0] + y.w[0];
if (z.w[0] < x.w[0]) {
x.w[1]++;
if (x.w[1] == 0x0000000000000000ull) {
x.w[2]++;
if (x.w[2] == 0x0000000000000000ull) {
x.w[3]++;
}
}
}
z.w[1] = x.w[1] + y.w[1];
if (z.w[1] < x.w[1]) {
x.w[2]++;
if (x.w[2] == 0x0000000000000000ull) {
x.w[3]++;
}
}
z.w[2] = x.w[2] + y.w[2];
if (z.w[2] < x.w[2]) {
x.w[3]++;
}
z.w[3] = x.w[3] + y.w[3]; // it was assumed that no carry is possible
*pz = z;
}
static void
sub256 (UINT256 x, UINT256 y, UINT256 * pz) {
// *z = x - y; assume x >= y
UINT256 z;
z.w[0] = x.w[0] - y.w[0];
if (z.w[0] > x.w[0]) {
x.w[1]--;
if (x.w[1] == 0xffffffffffffffffull) {
x.w[2]--;
if (x.w[2] == 0xffffffffffffffffull) {
x.w[3]--;
}
}
}
z.w[1] = x.w[1] - y.w[1];
if (z.w[1] > x.w[1]) {
x.w[2]--;
if (x.w[2] == 0xffffffffffffffffull) {
x.w[3]--;
}
}
z.w[2] = x.w[2] - y.w[2];
if (z.w[2] > x.w[2]) {
x.w[3]--;
}
z.w[3] = x.w[3] - y.w[3]; // no borrow possible, because x >= y
*pz = z;
}
static int
nr_digits256 (UINT256 R256) {
int ind;
// determine the number of decimal digits in R256
if (R256.w[3] == 0x0 && R256.w[2] == 0x0 && R256.w[1] == 0x0) {
// between 1 and 19 digits
for (ind = 1; ind <= 19; ind++) {
if (R256.w[0] < ten2k64[ind]) {
break;
}
}
// ind digits
} else if (R256.w[3] == 0x0 && R256.w[2] == 0x0 &&
(R256.w[1] < ten2k128[0].w[1] ||
(R256.w[1] == ten2k128[0].w[1]
&& R256.w[0] < ten2k128[0].w[0]))) {
// 20 digits
ind = 20;
} else if (R256.w[3] == 0x0 && R256.w[2] == 0x0) {
// between 21 and 38 digits
for (ind = 1; ind <= 18; ind++) {
if (R256.w[1] < ten2k128[ind].w[1] ||
(R256.w[1] == ten2k128[ind].w[1] &&
R256.w[0] < ten2k128[ind].w[0])) {
break;
}
}
// ind + 20 digits
ind = ind + 20;
} else if (R256.w[3] == 0x0 &&
(R256.w[2] < ten2k256[0].w[2] ||
(R256.w[2] == ten2k256[0].w[2] &&
R256.w[1] < ten2k256[0].w[1]) ||
(R256.w[2] == ten2k256[0].w[2] &&
R256.w[1] == ten2k256[0].w[1] &&
R256.w[0] < ten2k256[0].w[0]))) {
// 39 digits
ind = 39;
} else {
// between 40 and 68 digits
for (ind = 1; ind <= 29; ind++) {
if (R256.w[3] < ten2k256[ind].w[3] ||
(R256.w[3] == ten2k256[ind].w[3] &&
R256.w[2] < ten2k256[ind].w[2]) ||
(R256.w[3] == ten2k256[ind].w[3] &&
R256.w[2] == ten2k256[ind].w[2] &&
R256.w[1] < ten2k256[ind].w[1]) ||
(R256.w[3] == ten2k256[ind].w[3] &&
R256.w[2] == ten2k256[ind].w[2] &&
R256.w[1] == ten2k256[ind].w[1] &&
R256.w[0] < ten2k256[ind].w[0])) {
break;
}
}
// ind + 39 digits
ind = ind + 39;
}
return (ind);
}
// add/subtract C4 and C3 * 10^scale; this may follow a previous rounding, so
// use the rounding information from ptr_is_* to avoid a double rounding error
static void
add_and_round (int q3,
int q4,
int e4,
int delta,
int p34,
UINT64 z_sign,
UINT64 p_sign,
UINT128 C3,
UINT256 C4,
int rnd_mode,
int *ptr_is_midpoint_lt_even,
int *ptr_is_midpoint_gt_even,
int *ptr_is_inexact_lt_midpoint,
int *ptr_is_inexact_gt_midpoint,
_IDEC_flags * ptrfpsf, UINT128 * ptrres) {
int scale;
int x0;
int ind;
UINT64 R64;
UINT128 P128, R128;
UINT192 P192, R192;
UINT256 R256;
int is_midpoint_lt_even = 0;
int is_midpoint_gt_even = 0;
int is_inexact_lt_midpoint = 0;
int is_inexact_gt_midpoint = 0;
int is_midpoint_lt_even0 = 0;
int is_midpoint_gt_even0 = 0;
int is_inexact_lt_midpoint0 = 0;
int is_inexact_gt_midpoint0 = 0;
int incr_exp = 0;
int is_tiny = 0;
int lt_half_ulp = 0;
int eq_half_ulp = 0;
// int gt_half_ulp = 0;
UINT128 res = *ptrres;
// scale C3 up by 10^(q4-delta-q3), 0 <= q4-delta-q3 <= 2*P34-2 = 66
scale = q4 - delta - q3; // 0 <= scale <= 66 (or 0 <= scale <= 68 if this
// comes from Cases (2), (3), (4), (5), (6), with 0 <= |delta| <= 1
// calculate C3 * 10^scale in R256 (it has at most 67 decimal digits for
// Cases (15),(16),(17) and at most 69 for Cases (2),(3),(4),(5),(6))
if (scale == 0) {
R256.w[3] = 0x0ull;
R256.w[2] = 0x0ull;
R256.w[1] = C3.w[1];
R256.w[0] = C3.w[0];
} else if (scale <= 19) { // 10^scale fits in 64 bits
P128.w[1] = 0;
P128.w[0] = ten2k64[scale];
__mul_128x128_to_256 (R256, P128, C3);
} else if (scale <= 38) { // 10^scale fits in 128 bits
__mul_128x128_to_256 (R256, ten2k128[scale - 20], C3);
} else if (scale <= 57) { // 39 <= scale <= 57
// 10^scale fits in 192 bits but C3 * 10^scale fits in 223 or 230 bits
// (10^67 has 223 bits; 10^69 has 230 bits);
// must split the computation:
// 10^scale * C3 = 10*38 * 10^(scale-38) * C3 where 10^38 takes 127
// bits and so 10^(scale-38) * C3 fits in 128 bits with certainty
// Note that 1 <= scale - 38 <= 19 => 10^(scale-38) fits in 64 bits
__mul_64x128_to_128 (R128, ten2k64[scale - 38], C3);
// now multiply R128 by 10^38
__mul_128x128_to_256 (R256, R128, ten2k128[18]);
} else { // 58 <= scale <= 66
// 10^scale takes between 193 and 220 bits,
// and C3 * 10^scale fits in 223 bits (10^67/10^69 has 223/230 bits)
// must split the computation:
// 10^scale * C3 = 10*38 * 10^(scale-38) * C3 where 10^38 takes 127
// bits and so 10^(scale-38) * C3 fits in 128 bits with certainty
// Note that 20 <= scale - 38 <= 30 => 10^(scale-38) fits in 128 bits
// Calculate first 10^(scale-38) * C3, which fits in 128 bits; because
// 10^(scale-38) takes more than 64 bits, C3 will take less than 64
__mul_64x128_to_128 (R128, C3.w[0], ten2k128[scale - 58]);
// now calculate 10*38 * 10^(scale-38) * C3
__mul_128x128_to_256 (R256, R128, ten2k128[18]);
}
// C3 * 10^scale is now in R256
// for Cases (15), (16), (17) C4 > C3 * 10^scale because C4 has at least
// one extra digit; for Cases (2), (3), (4), (5), or (6) any order is
// possible
// add/subtract C4 and C3 * 10^scale; the exponent is e4
if (p_sign == z_sign) { // R256 = C4 + R256
// calculate R256 = C4 + C3 * 10^scale = C4 + R256 which is exact,
// but may require rounding
add256 (C4, R256, &R256);
} else { // if (p_sign != z_sign) { // R256 = C4 - R256
// calculate R256 = C4 - C3 * 10^scale = C4 - R256 or
// R256 = C3 * 10^scale - C4 = R256 - C4 which is exact,
// but may require rounding
// compare first R256 = C3 * 10^scale and C4
if (R256.w[3] > C4.w[3] || (R256.w[3] == C4.w[3] && R256.w[2] > C4.w[2]) ||
(R256.w[3] == C4.w[3] && R256.w[2] == C4.w[2] && R256.w[1] > C4.w[1]) ||
(R256.w[3] == C4.w[3] && R256.w[2] == C4.w[2] && R256.w[1] == C4.w[1] &&
R256.w[0] >= C4.w[0])) { // C3 * 10^scale >= C4
// calculate R256 = C3 * 10^scale - C4 = R256 - C4, which is exact,
// but may require rounding
sub256 (R256, C4, &R256);
// flip p_sign too, because the result has the sign of z
p_sign = z_sign;
} else { // if C4 > C3 * 10^scale
// calculate R256 = C4 - C3 * 10^scale = C4 - R256, which is exact,
// but may require rounding
sub256 (C4, R256, &R256);
}
// if the result is pure zero, the sign depends on the rounding mode
// (x*y and z had opposite signs)
if (R256.w[3] == 0x0ull && R256.w[2] == 0x0ull &&
R256.w[1] == 0x0ull && R256.w[0] == 0x0ull) {
if (rnd_mode != ROUNDING_DOWN)
p_sign = 0x0000000000000000ull;
else
p_sign = 0x8000000000000000ull;
// the exponent is max (e4, expmin)
if (e4 < -6176)
e4 = expmin;
// assemble result
res.w[1] = p_sign | ((UINT64) (e4 + 6176) << 49);
res.w[0] = 0x0;
*ptrres = res;
return;
}
}
// determine the number of decimal digits in R256
ind = nr_digits256 (R256);
// the exact result is (-1)^p_sign * R256 * 10^e4 where q (R256) = ind;
// round to the destination precision, with unbounded exponent
if (ind <= p34) {
// result rounded to the destination precision with unbounded exponent
// is exact
if (ind + e4 < p34 + expmin) {
is_tiny = 1; // applies to all rounding modes
}
res.w[1] = p_sign | ((UINT64) (e4 + 6176) << 49) | R256.w[1];
res.w[0] = R256.w[0];
// Note: res is correct only if expmin <= e4 <= expmax
} else { // if (ind > p34)
// if more than P digits, round to nearest to P digits
// round R256 to p34 digits
x0 = ind - p34; // 1 <= x0 <= 34 as 35 <= ind <= 68
if (ind <= 38) {
P128.w[1] = R256.w[1];
P128.w[0] = R256.w[0];
round128_19_38 (ind, x0, P128, &R128, &incr_exp,
&is_midpoint_lt_even, &is_midpoint_gt_even,
&is_inexact_lt_midpoint, &is_inexact_gt_midpoint);
} else if (ind <= 57) {
P192.w[2] = R256.w[2];
P192.w[1] = R256.w[1];
P192.w[0] = R256.w[0];
round192_39_57 (ind, x0, P192, &R192, &incr_exp,
&is_midpoint_lt_even, &is_midpoint_gt_even,
&is_inexact_lt_midpoint, &is_inexact_gt_midpoint);
R128.w[1] = R192.w[1];
R128.w[0] = R192.w[0];
} else { // if (ind <= 68)
round256_58_76 (ind, x0, R256, &R256, &incr_exp,
&is_midpoint_lt_even, &is_midpoint_gt_even,
&is_inexact_lt_midpoint, &is_inexact_gt_midpoint);
R128.w[1] = R256.w[1];
R128.w[0] = R256.w[0];
}
// the rounded result has p34 = 34 digits
e4 = e4 + x0 + incr_exp;
if (rnd_mode == ROUNDING_TO_NEAREST) {
if (e4 < expmin) {
is_tiny = 1; // for other rounding modes apply correction
}
} else {
// for RM, RP, RZ, RA apply correction in order to determine tininess
// but do not save the result; apply the correction to
// (-1)^p_sign * significand * 10^0
P128.w[1] = p_sign | 0x3040000000000000ull | R128.w[1];
P128.w[0] = R128.w[0];
rounding_correction (rnd_mode,
is_inexact_lt_midpoint,
is_inexact_gt_midpoint, is_midpoint_lt_even,
is_midpoint_gt_even, 0, &P128, ptrfpsf);
scale = ((P128.w[1] & MASK_EXP) >> 49) - 6176; // -1, 0, or +1
// the number of digits in the significand is p34 = 34
if (e4 + scale < expmin) {
is_tiny = 1;
}
}
ind = p34; // the number of decimal digits in the signifcand of res
res.w[1] = p_sign | ((UINT64) (e4 + 6176) << 49) | R128.w[1]; // RN
res.w[0] = R128.w[0];
// Note: res is correct only if expmin <= e4 <= expmax
// set the inexact flag after rounding with bounded exponent, if any
}
// at this point we have the result rounded with unbounded exponent in
// res and we know its tininess:
// res = (-1)^p_sign * significand * 10^e4,
// where q (significand) = ind <= p34
// Note: res is correct only if expmin <= e4 <= expmax
// check for overflow if RN
if (rnd_mode == ROUNDING_TO_NEAREST && (ind + e4) > (p34 + expmax)) {
res.w[1] = p_sign | 0x7800000000000000ull;
res.w[0] = 0x0000000000000000ull;
*ptrres = res;
*ptrfpsf |= (INEXACT_EXCEPTION | OVERFLOW_EXCEPTION);
return; // BID_RETURN (res)
} // else not overflow or not RN, so continue
// if (e4 >= expmin) we have the result rounded with bounded exponent
if (e4 < expmin) {
x0 = expmin - e4; // x0 >= 1; the number of digits to chop off of res
// where the result rounded [at most] once is
// (-1)^p_sign * significand_res * 10^e4
// avoid double rounding error
is_inexact_lt_midpoint0 = is_inexact_lt_midpoint;
is_inexact_gt_midpoint0 = is_inexact_gt_midpoint;
is_midpoint_lt_even0 = is_midpoint_lt_even;
is_midpoint_gt_even0 = is_midpoint_gt_even;
is_inexact_lt_midpoint = 0;
is_inexact_gt_midpoint = 0;
is_midpoint_lt_even = 0;
is_midpoint_gt_even = 0;
if (x0 > ind) {
// nothing is left of res when moving the decimal point left x0 digits
is_inexact_lt_midpoint = 1;
res.w[1] = p_sign | 0x0000000000000000ull;
res.w[0] = 0x0000000000000000ull;
e4 = expmin;
} else if (x0 == ind) { // 1 <= x0 = ind <= p34 = 34
// this is <, =, or > 1/2 ulp
// compare the ind-digit value in the significand of res with
// 1/2 ulp = 5*10^(ind-1), i.e. determine whether it is
// less than, equal to, or greater than 1/2 ulp (significand of res)
R128.w[1] = res.w[1] & MASK_COEFF;
R128.w[0] = res.w[0];
if (ind <= 19) {
if (R128.w[0] < midpoint64[ind - 1]) { // < 1/2 ulp
lt_half_ulp = 1;
is_inexact_lt_midpoint = 1;
} else if (R128.w[0] == midpoint64[ind - 1]) { // = 1/2 ulp
eq_half_ulp = 1;
is_midpoint_gt_even = 1;
} else { // > 1/2 ulp
// gt_half_ulp = 1;
is_inexact_gt_midpoint = 1;
}
} else { // if (ind <= 38) {
if (R128.w[1] < midpoint128[ind - 20].w[1] ||
(R128.w[1] == midpoint128[ind - 20].w[1] &&
R128.w[0] < midpoint128[ind - 20].w[0])) { // < 1/2 ulp
lt_half_ulp = 1;
is_inexact_lt_midpoint = 1;
} else if (R128.w[1] == midpoint128[ind - 20].w[1] &&
R128.w[0] == midpoint128[ind - 20].w[0]) { // = 1/2 ulp
eq_half_ulp = 1;
is_midpoint_gt_even = 1;
} else { // > 1/2 ulp
// gt_half_ulp = 1;
is_inexact_gt_midpoint = 1;
}
}
if (lt_half_ulp || eq_half_ulp) {
// res = +0.0 * 10^expmin
res.w[1] = 0x0000000000000000ull;
res.w[0] = 0x0000000000000000ull;
} else { // if (gt_half_ulp)
// res = +1 * 10^expmin
res.w[1] = 0x0000000000000000ull;
res.w[0] = 0x0000000000000001ull;
}
res.w[1] = p_sign | res.w[1];
e4 = expmin;
} else { // if (1 <= x0 <= ind - 1 <= 33)
// round the ind-digit result to ind - x0 digits
if (ind <= 18) { // 2 <= ind <= 18
round64_2_18 (ind, x0, res.w[0], &R64, &incr_exp,
&is_midpoint_lt_even, &is_midpoint_gt_even,
&is_inexact_lt_midpoint, &is_inexact_gt_midpoint);
res.w[1] = 0x0;
res.w[0] = R64;
} else if (ind <= 38) {
P128.w[1] = res.w[1] & MASK_COEFF;
P128.w[0] = res.w[0];
round128_19_38 (ind, x0, P128, &res, &incr_exp,
&is_midpoint_lt_even, &is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
}
e4 = e4 + x0; // expmin
// we want the exponent to be expmin, so if incr_exp = 1 then
// multiply the rounded result by 10 - it will still fit in 113 bits
if (incr_exp) {
// 64 x 128 -> 128
P128.w[1] = res.w[1] & MASK_COEFF;
P128.w[0] = res.w[0];
__mul_64x128_to_128 (res, ten2k64[1], P128);
}
res.w[1] =
p_sign | ((UINT64) (e4 + 6176) << 49) | (res.w[1] & MASK_COEFF);
// avoid a double rounding error
if ((is_inexact_gt_midpoint0 || is_midpoint_lt_even0) &&
is_midpoint_lt_even) { // double rounding error upward
// res = res - 1
res.w[0]--;
if (res.w[0] == 0xffffffffffffffffull)
res.w[1]--;
// Note: a double rounding error upward is not possible; for this
// the result after the first rounding would have to be 99...95
// (35 digits in all), possibly followed by a number of zeros; this
// is not possible in Cases (2)-(6) or (15)-(17) which may get here
is_midpoint_lt_even = 0;
is_inexact_lt_midpoint = 1;
} else if ((is_inexact_lt_midpoint0 || is_midpoint_gt_even0) &&
is_midpoint_gt_even) { // double rounding error downward
// res = res + 1
res.w[0]++;
if (res.w[0] == 0)
res.w[1]++;
is_midpoint_gt_even = 0;
is_inexact_gt_midpoint = 1;
} else if (!is_midpoint_lt_even && !is_midpoint_gt_even &&
!is_inexact_lt_midpoint && !is_inexact_gt_midpoint) {
// if this second rounding was exact the result may still be
// inexact because of the first rounding
if (is_inexact_gt_midpoint0 || is_midpoint_lt_even0) {
is_inexact_gt_midpoint = 1;
}
if (is_inexact_lt_midpoint0 || is_midpoint_gt_even0) {
is_inexact_lt_midpoint = 1;
}
} else if (is_midpoint_gt_even &&
(is_inexact_gt_midpoint0 || is_midpoint_lt_even0)) {
// pulled up to a midpoint
is_inexact_lt_midpoint = 1;
is_inexact_gt_midpoint = 0;
is_midpoint_lt_even = 0;
is_midpoint_gt_even = 0;
} else if (is_midpoint_lt_even &&
(is_inexact_lt_midpoint0 || is_midpoint_gt_even0)) {
// pulled down to a midpoint
is_inexact_lt_midpoint = 0;
is_inexact_gt_midpoint = 1;
is_midpoint_lt_even = 0;
is_midpoint_gt_even = 0;
} else {
;
}
}
}
// res contains the correct result
// apply correction if not rounding to nearest
if (rnd_mode != ROUNDING_TO_NEAREST) {
rounding_correction (rnd_mode,
is_inexact_lt_midpoint, is_inexact_gt_midpoint,
is_midpoint_lt_even, is_midpoint_gt_even,
e4, &res, ptrfpsf);
}
if (is_midpoint_lt_even || is_midpoint_gt_even ||
is_inexact_lt_midpoint || is_inexact_gt_midpoint) {
// set the inexact flag
*ptrfpsf |= INEXACT_EXCEPTION;
if (is_tiny)
*ptrfpsf |= UNDERFLOW_EXCEPTION;
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
*ptrres = res;
return;
}
#if DECIMAL_CALL_BY_REFERENCE
static void
bid128_ext_fma (int *ptr_is_midpoint_lt_even,
int *ptr_is_midpoint_gt_even,
int *ptr_is_inexact_lt_midpoint,
int *ptr_is_inexact_gt_midpoint, UINT128 * pres,
UINT128 * px, UINT128 * py,
UINT128 *
pz _RND_MODE_PARAM _EXC_FLAGS_PARAM _EXC_MASKS_PARAM
_EXC_INFO_PARAM) {
UINT128 x = *px, y = *py, z = *pz;
#if !DECIMAL_GLOBAL_ROUNDING
unsigned int rnd_mode = *prnd_mode;
#endif
#else
static UINT128
bid128_ext_fma (int *ptr_is_midpoint_lt_even,
int *ptr_is_midpoint_gt_even,
int *ptr_is_inexact_lt_midpoint,
int *ptr_is_inexact_gt_midpoint, UINT128 x, UINT128 y,
UINT128 z _RND_MODE_PARAM _EXC_FLAGS_PARAM
_EXC_MASKS_PARAM _EXC_INFO_PARAM) {
#endif
UINT128 res = { {0xbaddbaddbaddbaddull, 0xbaddbaddbaddbaddull} };
UINT64 x_sign, y_sign, z_sign, p_sign, tmp_sign;
UINT64 x_exp = 0, y_exp = 0, z_exp = 0, p_exp;
int true_p_exp;
UINT128 C1, C2, C3;
UINT256 C4;
int q1 = 0, q2 = 0, q3 = 0, q4;
int e1, e2, e3, e4;
int scale, ind, delta, x0;
int p34 = P34; // used to modify the limit on the number of digits
BID_UI64DOUBLE tmp;
int x_nr_bits, y_nr_bits, z_nr_bits;
unsigned int save_fpsf;
int is_midpoint_lt_even = 0, is_midpoint_gt_even = 0;
int is_inexact_lt_midpoint = 0, is_inexact_gt_midpoint = 0;
int is_midpoint_lt_even0 = 0, is_midpoint_gt_even0 = 0;
int is_inexact_lt_midpoint0 = 0, is_inexact_gt_midpoint0 = 0;
int incr_exp = 0;
int lsb;
int lt_half_ulp = 0;
int eq_half_ulp = 0;
int gt_half_ulp = 0;
int is_tiny = 0;
UINT64 R64, tmp64;
UINT128 P128, R128;
UINT192 P192, R192;
UINT256 R256;
// the following are based on the table of special cases for fma; the NaN
// behavior is similar to that of the IA-64 Architecture fma
// identify cases where at least one operand is NaN
BID_SWAP128 (x);
BID_SWAP128 (y);
BID_SWAP128 (z);
if ((y.w[1] & MASK_NAN) == MASK_NAN) { // y is NAN
// if x = {0, f, inf, NaN}, y = NaN, z = {0, f, inf, NaN} then res = Q (y)
// check first for non-canonical NaN payload
if (((y.w[1] & 0x00003fffffffffffull) > 0x0000314dc6448d93ull) ||
(((y.w[1] & 0x00003fffffffffffull) == 0x0000314dc6448d93ull) &&
(y.w[0] > 0x38c15b09ffffffffull))) {
y.w[1] = y.w[1] & 0xffffc00000000000ull;
y.w[0] = 0x0ull;
}
if ((y.w[1] & MASK_SNAN) == MASK_SNAN) { // y is SNAN
// set invalid flag
*pfpsf |= INVALID_EXCEPTION;
// return quiet (y)
res.w[1] = y.w[1] & 0xfc003fffffffffffull; // clear out also G[6]-G[16]
res.w[0] = y.w[0];
} else { // y is QNaN
// return y
res.w[1] = y.w[1] & 0xfc003fffffffffffull; // clear out G[6]-G[16]
res.w[0] = y.w[0];
// if z = SNaN or x = SNaN signal invalid exception
if ((z.w[1] & MASK_SNAN) == MASK_SNAN ||
(x.w[1] & MASK_SNAN) == MASK_SNAN) {
// set invalid flag
*pfpsf |= INVALID_EXCEPTION;
}
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
} else if ((z.w[1] & MASK_NAN) == MASK_NAN) { // z is NAN
// if x = {0, f, inf, NaN}, y = {0, f, inf}, z = NaN then res = Q (z)
// check first for non-canonical NaN payload
if (((z.w[1] & 0x00003fffffffffffull) > 0x0000314dc6448d93ull) ||
(((z.w[1] & 0x00003fffffffffffull) == 0x0000314dc6448d93ull) &&
(z.w[0] > 0x38c15b09ffffffffull))) {
z.w[1] = z.w[1] & 0xffffc00000000000ull;
z.w[0] = 0x0ull;
}
if ((z.w[1] & MASK_SNAN) == MASK_SNAN) { // z is SNAN
// set invalid flag
*pfpsf |= INVALID_EXCEPTION;
// return quiet (z)
res.w[1] = z.w[1] & 0xfc003fffffffffffull; // clear out also G[6]-G[16]
res.w[0] = z.w[0];
} else { // z is QNaN
// return z
res.w[1] = z.w[1] & 0xfc003fffffffffffull; // clear out G[6]-G[16]
res.w[0] = z.w[0];
// if x = SNaN signal invalid exception
if ((x.w[1] & MASK_SNAN) == MASK_SNAN) {
// set invalid flag
*pfpsf |= INVALID_EXCEPTION;
}
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
} else if ((x.w[1] & MASK_NAN) == MASK_NAN) { // x is NAN
// if x = NaN, y = {0, f, inf}, z = {0, f, inf} then res = Q (x)
// check first for non-canonical NaN payload
if (((x.w[1] & 0x00003fffffffffffull) > 0x0000314dc6448d93ull) ||
(((x.w[1] & 0x00003fffffffffffull) == 0x0000314dc6448d93ull) &&
(x.w[0] > 0x38c15b09ffffffffull))) {
x.w[1] = x.w[1] & 0xffffc00000000000ull;
x.w[0] = 0x0ull;
}
if ((x.w[1] & MASK_SNAN) == MASK_SNAN) { // x is SNAN
// set invalid flag
*pfpsf |= INVALID_EXCEPTION;
// return quiet (x)
res.w[1] = x.w[1] & 0xfc003fffffffffffull; // clear out also G[6]-G[16]
res.w[0] = x.w[0];
} else { // x is QNaN
// return x
res.w[1] = x.w[1] & 0xfc003fffffffffffull; // clear out G[6]-G[16]
res.w[0] = x.w[0];
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
}
// x, y, z are 0, f, or inf but not NaN => unpack the arguments and check
// for non-canonical values
x_sign = x.w[1] & MASK_SIGN; // 0 for positive, MASK_SIGN for negative
C1.w[1] = x.w[1] & MASK_COEFF;
C1.w[0] = x.w[0];
if ((x.w[1] & MASK_ANY_INF) != MASK_INF) { // x != inf
// if x is not infinity check for non-canonical values - treated as zero
if ((x.w[1] & 0x6000000000000000ull) == 0x6000000000000000ull) { // G0_G1=11
// non-canonical
x_exp = (x.w[1] << 2) & MASK_EXP; // biased and shifted left 49 bits
C1.w[1] = 0; // significand high
C1.w[0] = 0; // significand low
} else { // G0_G1 != 11
x_exp = x.w[1] & MASK_EXP; // biased and shifted left 49 bits
if (C1.w[1] > 0x0001ed09bead87c0ull ||
(C1.w[1] == 0x0001ed09bead87c0ull &&
C1.w[0] > 0x378d8e63ffffffffull)) {
// x is non-canonical if coefficient is larger than 10^34 -1
C1.w[1] = 0;
C1.w[0] = 0;
} else { // canonical
;
}
}
}
y_sign = y.w[1] & MASK_SIGN; // 0 for positive, MASK_SIGN for negative
C2.w[1] = y.w[1] & MASK_COEFF;
C2.w[0] = y.w[0];
if ((y.w[1] & MASK_ANY_INF) != MASK_INF) { // y != inf
// if y is not infinity check for non-canonical values - treated as zero
if ((y.w[1] & 0x6000000000000000ull) == 0x6000000000000000ull) { // G0_G1=11
// non-canonical
y_exp = (y.w[1] << 2) & MASK_EXP; // biased and shifted left 49 bits
C2.w[1] = 0; // significand high
C2.w[0] = 0; // significand low
} else { // G0_G1 != 11
y_exp = y.w[1] & MASK_EXP; // biased and shifted left 49 bits
if (C2.w[1] > 0x0001ed09bead87c0ull ||
(C2.w[1] == 0x0001ed09bead87c0ull &&
C2.w[0] > 0x378d8e63ffffffffull)) {
// y is non-canonical if coefficient is larger than 10^34 -1
C2.w[1] = 0;
C2.w[0] = 0;
} else { // canonical
;
}
}
}
z_sign = z.w[1] & MASK_SIGN; // 0 for positive, MASK_SIGN for negative
C3.w[1] = z.w[1] & MASK_COEFF;
C3.w[0] = z.w[0];
if ((z.w[1] & MASK_ANY_INF) != MASK_INF) { // z != inf
// if z is not infinity check for non-canonical values - treated as zero
if ((z.w[1] & 0x6000000000000000ull) == 0x6000000000000000ull) { // G0_G1=11
// non-canonical
z_exp = (z.w[1] << 2) & MASK_EXP; // biased and shifted left 49 bits
C3.w[1] = 0; // significand high
C3.w[0] = 0; // significand low
} else { // G0_G1 != 11
z_exp = z.w[1] & MASK_EXP; // biased and shifted left 49 bits
if (C3.w[1] > 0x0001ed09bead87c0ull ||
(C3.w[1] == 0x0001ed09bead87c0ull &&
C3.w[0] > 0x378d8e63ffffffffull)) {
// z is non-canonical if coefficient is larger than 10^34 -1
C3.w[1] = 0;
C3.w[0] = 0;
} else { // canonical
;
}
}
}
p_sign = x_sign ^ y_sign; // sign of the product
// identify cases where at least one operand is infinity
if ((x.w[1] & MASK_ANY_INF) == MASK_INF) { // x = inf
if ((y.w[1] & MASK_ANY_INF) == MASK_INF) { // y = inf
if ((z.w[1] & MASK_ANY_INF) == MASK_INF) { // z = inf
if (p_sign == z_sign) {
res.w[1] = z_sign | MASK_INF;
res.w[0] = 0x0;
} else {
// return QNaN Indefinite
res.w[1] = 0x7c00000000000000ull;
res.w[0] = 0x0000000000000000ull;
// set invalid flag
*pfpsf |= INVALID_EXCEPTION;
}
} else { // z = 0 or z = f
res.w[1] = p_sign | MASK_INF;
res.w[0] = 0x0;
}
} else if (C2.w[1] != 0 || C2.w[0] != 0) { // y = f
if ((z.w[1] & MASK_ANY_INF) == MASK_INF) { // z = inf
if (p_sign == z_sign) {
res.w[1] = z_sign | MASK_INF;
res.w[0] = 0x0;
} else {
// return QNaN Indefinite
res.w[1] = 0x7c00000000000000ull;
res.w[0] = 0x0000000000000000ull;
// set invalid flag
*pfpsf |= INVALID_EXCEPTION;
}
} else { // z = 0 or z = f
res.w[1] = p_sign | MASK_INF;
res.w[0] = 0x0;
}
} else { // y = 0
// return QNaN Indefinite
res.w[1] = 0x7c00000000000000ull;
res.w[0] = 0x0000000000000000ull;
// set invalid flag
*pfpsf |= INVALID_EXCEPTION;
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
} else if ((y.w[1] & MASK_ANY_INF) == MASK_INF) { // y = inf
if ((z.w[1] & MASK_ANY_INF) == MASK_INF) { // z = inf
// x = f, necessarily
if ((p_sign != z_sign)
|| (C1.w[1] == 0x0ull && C1.w[0] == 0x0ull)) {
// return QNaN Indefinite
res.w[1] = 0x7c00000000000000ull;
res.w[0] = 0x0000000000000000ull;
// set invalid flag
*pfpsf |= INVALID_EXCEPTION;
} else {
res.w[1] = z_sign | MASK_INF;
res.w[0] = 0x0;
}
} else if (C1.w[1] == 0x0 && C1.w[0] == 0x0) { // x = 0
// z = 0, f, inf
// return QNaN Indefinite
res.w[1] = 0x7c00000000000000ull;
res.w[0] = 0x0000000000000000ull;
// set invalid flag
*pfpsf |= INVALID_EXCEPTION;
} else {
// x = f and z = 0, f, necessarily
res.w[1] = p_sign | MASK_INF;
res.w[0] = 0x0;
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
} else if ((z.w[1] & MASK_ANY_INF) == MASK_INF) { // z = inf
// x = 0, f and y = 0, f, necessarily
res.w[1] = z_sign | MASK_INF;
res.w[0] = 0x0;
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
}
true_p_exp = (x_exp >> 49) - 6176 + (y_exp >> 49) - 6176;
if (true_p_exp < -6176)
p_exp = 0; // cannot be less than EXP_MIN
else
p_exp = (UINT64) (true_p_exp + 6176) << 49;
if (((C1.w[1] == 0x0 && C1.w[0] == 0x0) || (C2.w[1] == 0x0 && C2.w[0] == 0x0)) && C3.w[1] == 0x0 && C3.w[0] == 0x0) { // (x = 0 or y = 0) and z = 0
// the result is 0
if (p_exp < z_exp)
res.w[1] = p_exp; // preferred exponent
else
res.w[1] = z_exp; // preferred exponent
if (p_sign == z_sign) {
res.w[1] |= z_sign;
res.w[0] = 0x0;
} else { // x * y and z have opposite signs
if (rnd_mode == ROUNDING_DOWN) {
// res = -0.0
res.w[1] |= MASK_SIGN;
res.w[0] = 0x0;
} else {
// res = +0.0
// res.w[1] |= 0x0;
res.w[0] = 0x0;
}
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
}
// from this point on, we may need to know the number of decimal digits
// in the significands of x, y, z when x, y, z != 0
if (C1.w[1] != 0 || C1.w[0] != 0) { // x = f (non-zero finite)
// q1 = nr. of decimal digits in x
// determine first the nr. of bits in x
if (C1.w[1] == 0) {
if (C1.w[0] >= 0x0020000000000000ull) { // x >= 2^53
// split the 64-bit value in two 32-bit halves to avoid rounding errors
if (C1.w[0] >= 0x0000000100000000ull) { // x >= 2^32
tmp.d = (double) (C1.w[0] >> 32); // exact conversion
x_nr_bits =
33 + ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
} else { // x < 2^32
tmp.d = (double) (C1.w[0]); // exact conversion
x_nr_bits =
1 + ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
}
} else { // if x < 2^53
tmp.d = (double) C1.w[0]; // exact conversion
x_nr_bits =
1 + ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
}
} else { // C1.w[1] != 0 => nr. bits = 64 + nr_bits (C1.w[1])
tmp.d = (double) C1.w[1]; // exact conversion
x_nr_bits =
65 + ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
}
q1 = nr_digits[x_nr_bits - 1].digits;
if (q1 == 0) {
q1 = nr_digits[x_nr_bits - 1].digits1;
if (C1.w[1] > nr_digits[x_nr_bits - 1].threshold_hi ||
(C1.w[1] == nr_digits[x_nr_bits - 1].threshold_hi &&
C1.w[0] >= nr_digits[x_nr_bits - 1].threshold_lo))
q1++;
}
}
if (C2.w[1] != 0 || C2.w[0] != 0) { // y = f (non-zero finite)
if (C2.w[1] == 0) {
if (C2.w[0] >= 0x0020000000000000ull) { // y >= 2^53
// split the 64-bit value in two 32-bit halves to avoid rounding errors
if (C2.w[0] >= 0x0000000100000000ull) { // y >= 2^32
tmp.d = (double) (C2.w[0] >> 32); // exact conversion
y_nr_bits =
32 + ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
} else { // y < 2^32
tmp.d = (double) C2.w[0]; // exact conversion
y_nr_bits =
((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
}
} else { // if y < 2^53
tmp.d = (double) C2.w[0]; // exact conversion
y_nr_bits =
((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
}
} else { // C2.w[1] != 0 => nr. bits = 64 + nr_bits (C2.w[1])
tmp.d = (double) C2.w[1]; // exact conversion
y_nr_bits =
64 + ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
}
q2 = nr_digits[y_nr_bits].digits;
if (q2 == 0) {
q2 = nr_digits[y_nr_bits].digits1;
if (C2.w[1] > nr_digits[y_nr_bits].threshold_hi ||
(C2.w[1] == nr_digits[y_nr_bits].threshold_hi &&
C2.w[0] >= nr_digits[y_nr_bits].threshold_lo))
q2++;
}
}
if (C3.w[1] != 0 || C3.w[0] != 0) { // z = f (non-zero finite)
if (C3.w[1] == 0) {
if (C3.w[0] >= 0x0020000000000000ull) { // z >= 2^53
// split the 64-bit value in two 32-bit halves to avoid rounding errors
if (C3.w[0] >= 0x0000000100000000ull) { // z >= 2^32
tmp.d = (double) (C3.w[0] >> 32); // exact conversion
z_nr_bits =
32 + ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
} else { // z < 2^32
tmp.d = (double) C3.w[0]; // exact conversion
z_nr_bits =
((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
}
} else { // if z < 2^53
tmp.d = (double) C3.w[0]; // exact conversion
z_nr_bits =
((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
}
} else { // C3.w[1] != 0 => nr. bits = 64 + nr_bits (C3.w[1])
tmp.d = (double) C3.w[1]; // exact conversion
z_nr_bits =
64 + ((((unsigned int) (tmp.ui64 >> 52)) & 0x7ff) - 0x3ff);
}
q3 = nr_digits[z_nr_bits].digits;
if (q3 == 0) {
q3 = nr_digits[z_nr_bits].digits1;
if (C3.w[1] > nr_digits[z_nr_bits].threshold_hi ||
(C3.w[1] == nr_digits[z_nr_bits].threshold_hi &&
C3.w[0] >= nr_digits[z_nr_bits].threshold_lo))
q3++;
}
}
if ((C1.w[1] == 0x0 && C1.w[0] == 0x0) ||
(C2.w[1] == 0x0 && C2.w[0] == 0x0)) {
// x = 0 or y = 0
// z = f, necessarily; for 0 + z return z, with the preferred exponent
// the result is z, but need to get the preferred exponent
if (z_exp <= p_exp) { // the preferred exponent is z_exp
res.w[1] = z_sign | (z_exp & MASK_EXP) | C3.w[1];
res.w[0] = C3.w[0];
} else { // if (p_exp < z_exp) the preferred exponent is p_exp
// return (C3 * 10^scale) * 10^(z_exp - scale)
// where scale = min (p34-q3, (z_exp-p_exp) >> 49)
scale = p34 - q3;
ind = (z_exp - p_exp) >> 49;
if (ind < scale)
scale = ind;
if (scale == 0) {
res.w[1] = z.w[1]; // & MASK_COEFF, which is redundant
res.w[0] = z.w[0];
} else if (q3 <= 19) { // z fits in 64 bits
if (scale <= 19) { // 10^scale fits in 64 bits
// 64 x 64 C3.w[0] * ten2k64[scale]
__mul_64x64_to_128MACH (res, C3.w[0], ten2k64[scale]);
} else { // 10^scale fits in 128 bits
// 64 x 128 C3.w[0] * ten2k128[scale - 20]
__mul_128x64_to_128 (res, C3.w[0], ten2k128[scale - 20]);
}
} else { // z fits in 128 bits, but 10^scale must fit in 64 bits
// 64 x 128 ten2k64[scale] * C3
__mul_128x64_to_128 (res, ten2k64[scale], C3);
}
// subtract scale from the exponent
z_exp = z_exp - ((UINT64) scale << 49);
res.w[1] = z_sign | (z_exp & MASK_EXP) | res.w[1];
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
} else {
; // continue with x = f, y = f, z = 0 or x = f, y = f, z = f
}
e1 = (x_exp >> 49) - 6176; // unbiased exponent of x
e2 = (y_exp >> 49) - 6176; // unbiased exponent of y
e3 = (z_exp >> 49) - 6176; // unbiased exponent of z
e4 = e1 + e2; // unbiased exponent of the exact x * y
// calculate C1 * C2 and its number of decimal digits, q4
// the exact product has either q1 + q2 - 1 or q1 + q2 decimal digits
// where 2 <= q1 + q2 <= 68
// calculate C4 = C1 * C2 and determine q
C4.w[3] = C4.w[2] = C4.w[1] = C4.w[0] = 0;
if (q1 + q2 <= 19) { // if 2 <= q1 + q2 <= 19, C4 = C1 * C2 fits in 64 bits
C4.w[0] = C1.w[0] * C2.w[0];
// if C4 < 10^(q1+q2-1) then q4 = q1 + q2 - 1 else q4 = q1 + q2
if (C4.w[0] < ten2k64[q1 + q2 - 1])
q4 = q1 + q2 - 1; // q4 in [1, 18]
else
q4 = q1 + q2; // q4 in [2, 19]
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 64;
} else if (q1 + q2 == 20) { // C4 = C1 * C2 fits in 64 or 128 bits
// q1 <= 19 and q2 <= 19 so both C1 and C2 fit in 64 bits
__mul_64x64_to_128MACH (C4, C1.w[0], C2.w[0]);
// if C4 < 10^(q1+q2-1) = 10^19 then q4 = q1+q2-1 = 19 else q4 = q1+q2 = 20
if (C4.w[1] == 0 && C4.w[0] < ten2k64[19]) { // 19 = q1+q2-1
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 64;
q4 = 19; // 19 = q1 + q2 - 1
} else {
// if (C4.w[1] == 0)
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 64;
// else
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 128;
q4 = 20; // 20 = q1 + q2
}
} else if (q1 + q2 <= 38) { // 21 <= q1 + q2 <= 38
// C4 = C1 * C2 fits in 64 or 128 bits
// (64 bits possibly, but only when q1 + q2 = 21 and C4 has 20 digits)
// at least one of C1, C2 has at most 19 decimal digits & fits in 64 bits
if (q1 <= 19) {
__mul_128x64_to_128 (C4, C1.w[0], C2);
} else { // q2 <= 19
__mul_128x64_to_128 (C4, C2.w[0], C1);
}
// if C4 < 10^(q1+q2-1) then q4 = q1 + q2 - 1 else q4 = q1 + q2
if (C4.w[1] < ten2k128[q1 + q2 - 21].w[1] ||
(C4.w[1] == ten2k128[q1 + q2 - 21].w[1] &&
C4.w[0] < ten2k128[q1 + q2 - 21].w[0])) {
// if (C4.w[1] == 0) // q4 = 20, necessarily
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 64;
// else
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 128;
q4 = q1 + q2 - 1; // q4 in [20, 37]
} else {
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 128;
q4 = q1 + q2; // q4 in [21, 38]
}
} else if (q1 + q2 == 39) { // C4 = C1 * C2 fits in 128 or 192 bits
// both C1 and C2 fit in 128 bits (actually in 113 bits)
// may replace this by 128x128_to192
__mul_128x128_to_256 (C4, C1, C2); // C4.w[3] is 0
// if C4 < 10^(q1+q2-1) = 10^38 then q4 = q1+q2-1 = 38 else q4 = q1+q2 = 39
if (C4.w[2] == 0 && (C4.w[1] < ten2k128[18].w[1] ||
(C4.w[1] == ten2k128[18].w[1]
&& C4.w[0] < ten2k128[18].w[0]))) {
// 18 = 38 - 20 = q1+q2-1 - 20
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 128;
q4 = 38; // 38 = q1 + q2 - 1
} else {
// if (C4.w[2] == 0)
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 128;
// else
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 192;
q4 = 39; // 39 = q1 + q2
}
} else if (q1 + q2 <= 57) { // 40 <= q1 + q2 <= 57
// C4 = C1 * C2 fits in 128 or 192 bits
// (128 bits possibly, but only when q1 + q2 = 40 and C4 has 39 digits)
// both C1 and C2 fit in 128 bits (actually in 113 bits); at most one
// may fit in 64 bits
if (C1.w[1] == 0) { // C1 fits in 64 bits
// __mul_64x128_full (REShi64, RESlo128, A64, B128)
__mul_64x128_full (C4.w[2], C4, C1.w[0], C2);
} else if (C2.w[1] == 0) { // C2 fits in 64 bits
// __mul_64x128_full (REShi64, RESlo128, A64, B128)
__mul_64x128_full (C4.w[2], C4, C2.w[0], C1);
} else { // both C1 and C2 require 128 bits
// may use __mul_128x128_to_192 (C4.w[2], C4.w[0], C2.w[0], C1);
__mul_128x128_to_256 (C4, C1, C2); // C4.w[3] = 0
}
// if C4 < 10^(q1+q2-1) then q4 = q1 + q2 - 1 else q4 = q1 + q2
if (C4.w[2] < ten2k256[q1 + q2 - 40].w[2] ||
(C4.w[2] == ten2k256[q1 + q2 - 40].w[2] &&
(C4.w[1] < ten2k256[q1 + q2 - 40].w[1] ||
(C4.w[1] == ten2k256[q1 + q2 - 40].w[1] &&
C4.w[0] < ten2k256[q1 + q2 - 40].w[0])))) {
// if (C4.w[2] == 0) // q4 = 39, necessarily
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 128;
// else
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 192;
q4 = q1 + q2 - 1; // q4 in [39, 56]
} else {
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 192;
q4 = q1 + q2; // q4 in [40, 57]
}
} else if (q1 + q2 == 58) { // C4 = C1 * C2 fits in 192 or 256 bits
// both C1 and C2 fit in 128 bits (actually in 113 bits); at most one
// may fit in 64 bits
if (C1.w[1] == 0) { // C1 * C2 will fit in 192 bits
__mul_64x128_full (C4.w[2], C4, C1.w[0], C2); // may use 64x128_to_192
} else if (C2.w[1] == 0) { // C1 * C2 will fit in 192 bits
__mul_64x128_full (C4.w[2], C4, C2.w[0], C1); // may use 64x128_to_192
} else { // C1 * C2 will fit in 192 bits or in 256 bits
__mul_128x128_to_256 (C4, C1, C2);
}
// if C4 < 10^(q1+q2-1) = 10^57 then q4 = q1+q2-1 = 57 else q4 = q1+q2 = 58
if (C4.w[3] == 0 && (C4.w[2] < ten2k256[18].w[2] ||
(C4.w[2] == ten2k256[18].w[2]
&& (C4.w[1] < ten2k256[18].w[1]
|| (C4.w[1] == ten2k256[18].w[1]
&& C4.w[0] < ten2k256[18].w[0]))))) {
// 18 = 57 - 39 = q1+q2-1 - 39
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 192;
q4 = 57; // 57 = q1 + q2 - 1
} else {
// if (C4.w[3] == 0)
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 192;
// else
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 256;
q4 = 58; // 58 = q1 + q2
}
} else { // if 59 <= q1 + q2 <= 68
// C4 = C1 * C2 fits in 192 or 256 bits
// (192 bits possibly, but only when q1 + q2 = 59 and C4 has 58 digits)
// both C1 and C2 fit in 128 bits (actually in 113 bits); none fits in
// 64 bits
// may use __mul_128x128_to_192 (C4.w[2], C4.w[0], C2.w[0], C1);
__mul_128x128_to_256 (C4, C1, C2); // C4.w[3] = 0
// if C4 < 10^(q1+q2-1) then q4 = q1 + q2 - 1 else q4 = q1 + q2
if (C4.w[3] < ten2k256[q1 + q2 - 40].w[3] ||
(C4.w[3] == ten2k256[q1 + q2 - 40].w[3] &&
(C4.w[2] < ten2k256[q1 + q2 - 40].w[2] ||
(C4.w[2] == ten2k256[q1 + q2 - 40].w[2] &&
(C4.w[1] < ten2k256[q1 + q2 - 40].w[1] ||
(C4.w[1] == ten2k256[q1 + q2 - 40].w[1] &&
C4.w[0] < ten2k256[q1 + q2 - 40].w[0])))))) {
// if (C4.w[3] == 0) // q4 = 58, necessarily
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 192;
// else
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 256;
q4 = q1 + q2 - 1; // q4 in [58, 67]
} else {
// length of C1 * C2 rounded up to a multiple of 64 bits is len = 256;
q4 = q1 + q2; // q4 in [59, 68]
}
}
if (C3.w[1] == 0x0 && C3.w[0] == 0x0) { // x = f, y = f, z = 0
save_fpsf = *pfpsf; // sticky bits - caller value must be preserved
*pfpsf = 0;
if (q4 > p34) {
// truncate C4 to p34 digits into res
// x = q4-p34, 1 <= x <= 34 because 35 <= q4 <= 68
x0 = q4 - p34;
if (q4 <= 38) {
P128.w[1] = C4.w[1];
P128.w[0] = C4.w[0];
round128_19_38 (q4, x0, P128, &res, &incr_exp,
&is_midpoint_lt_even, &is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
} else if (q4 <= 57) { // 35 <= q4 <= 57
P192.w[2] = C4.w[2];
P192.w[1] = C4.w[1];
P192.w[0] = C4.w[0];
round192_39_57 (q4, x0, P192, &R192, &incr_exp,
&is_midpoint_lt_even, &is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
res.w[0] = R192.w[0];
res.w[1] = R192.w[1];
} else { // if (q4 <= 68)
round256_58_76 (q4, x0, C4, &R256, &incr_exp,
&is_midpoint_lt_even, &is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
res.w[0] = R256.w[0];
res.w[1] = R256.w[1];
}
e4 = e4 + x0;
if (incr_exp) {
e4 = e4 + 1;
}
q4 = p34;
// res is now the coefficient of the result rounded to the destination
// precision, with unbounded exponent; the exponent is e4; q4=digits(res)
} else { // if (q4 <= p34)
// C4 * 10^e4 is the result rounded to the destination precision, with
// unbounded exponent (which is exact)
if ((q4 + e4 <= p34 + expmax) && (e4 > expmax)) {
// e4 is too large, but can be brought within range by scaling up C4
scale = e4 - expmax; // 1 <= scale < P-q4 <= P-1 => 1 <= scale <= P-2
// res = (C4 * 10^scale) * 10^expmax
if (q4 <= 19) { // C4 fits in 64 bits
if (scale <= 19) { // 10^scale fits in 64 bits
// 64 x 64 C4.w[0] * ten2k64[scale]
__mul_64x64_to_128MACH (res, C4.w[0], ten2k64[scale]);
} else { // 10^scale fits in 128 bits
// 64 x 128 C4.w[0] * ten2k128[scale - 20]
__mul_128x64_to_128 (res, C4.w[0], ten2k128[scale - 20]);
}
} else { // C4 fits in 128 bits, but 10^scale must fit in 64 bits
// 64 x 128 ten2k64[scale] * CC43
__mul_128x64_to_128 (res, ten2k64[scale], C4);
}
e4 = e4 - scale; // expmax
q4 = q4 + scale;
} else {
res.w[1] = C4.w[1];
res.w[0] = C4.w[0];
}
// res is the coefficient of the result rounded to the destination
// precision, with unbounded exponent (it has q4 digits); the exponent
// is e4 (exact result)
}
// check for overflow
if (q4 + e4 > p34 + expmax) {
if (rnd_mode == ROUNDING_TO_NEAREST) {
res.w[1] = p_sign | 0x7800000000000000ull; // +/-inf
res.w[0] = 0x0000000000000000ull;
*pfpsf |= (INEXACT_EXCEPTION | OVERFLOW_EXCEPTION);
} else {
res.w[1] = p_sign | res.w[1];
rounding_correction (rnd_mode,
is_inexact_lt_midpoint,
is_inexact_gt_midpoint,
is_midpoint_lt_even, is_midpoint_gt_even,
e4, &res, pfpsf);
}
*pfpsf |= save_fpsf;
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
}
// check for underflow
if (q4 + e4 < expmin + P34) {
is_tiny = 1; // the result is tiny
if (e4 < expmin) {
// if e4 < expmin, we must truncate more of res
x0 = expmin - e4; // x0 >= 1
is_inexact_lt_midpoint0 = is_inexact_lt_midpoint;
is_inexact_gt_midpoint0 = is_inexact_gt_midpoint;
is_midpoint_lt_even0 = is_midpoint_lt_even;
is_midpoint_gt_even0 = is_midpoint_gt_even;
is_inexact_lt_midpoint = 0;
is_inexact_gt_midpoint = 0;
is_midpoint_lt_even = 0;
is_midpoint_gt_even = 0;
// the number of decimal digits in res is q4
if (x0 < q4) { // 1 <= x0 <= q4-1 => round res to q4 - x0 digits
if (q4 <= 18) { // 2 <= q4 <= 18, 1 <= x0 <= 17
round64_2_18 (q4, x0, res.w[0], &R64, &incr_exp,
&is_midpoint_lt_even, &is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
if (incr_exp) {
// R64 = 10^(q4-x0), 1 <= q4 - x0 <= q4 - 1, 1 <= q4 - x0 <= 17
R64 = ten2k64[q4 - x0];
}
// res.w[1] = 0; (from above)
res.w[0] = R64;
} else { // if (q4 <= 34)
// 19 <= q4 <= 38
P128.w[1] = res.w[1];
P128.w[0] = res.w[0];
round128_19_38 (q4, x0, P128, &res, &incr_exp,
&is_midpoint_lt_even, &is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
if (incr_exp) {
// increase coefficient by a factor of 10; this will be <= 10^33
// R128 = 10^(q4-x0), 1 <= q4 - x0 <= q4 - 1, 1 <= q4 - x0 <= 37
if (q4 - x0 <= 19) { // 1 <= q4 - x0 <= 19
// res.w[1] = 0;
res.w[0] = ten2k64[q4 - x0];
} else { // 20 <= q4 - x0 <= 37
res.w[0] = ten2k128[q4 - x0 - 20].w[0];
res.w[1] = ten2k128[q4 - x0 - 20].w[1];
}
}
}
e4 = e4 + x0; // expmin
} else if (x0 == q4) {
// the second rounding is for 0.d(0)d(1)...d(q4-1) * 10^emin
// determine relationship with 1/2 ulp
if (q4 <= 19) {
if (res.w[0] < midpoint64[q4 - 1]) { // < 1/2 ulp
lt_half_ulp = 1;
is_inexact_lt_midpoint = 1;
} else if (res.w[0] == midpoint64[q4 - 1]) { // = 1/2 ulp
eq_half_ulp = 1;
is_midpoint_gt_even = 1;
} else { // > 1/2 ulp
// gt_half_ulp = 1;
is_inexact_gt_midpoint = 1;
}
} else { // if (q4 <= 34)
if (res.w[1] < midpoint128[q4 - 20].w[1] ||
(res.w[1] == midpoint128[q4 - 20].w[1] &&
res.w[0] < midpoint128[q4 - 20].w[0])) { // < 1/2 ulp
lt_half_ulp = 1;
is_inexact_lt_midpoint = 1;
} else if (res.w[1] == midpoint128[q4 - 20].w[1] &&
res.w[0] == midpoint128[q4 - 20].w[0]) { // = 1/2 ulp
eq_half_ulp = 1;
is_midpoint_gt_even = 1;
} else { // > 1/2 ulp
// gt_half_ulp = 1;
is_inexact_gt_midpoint = 1;
}
}
if (lt_half_ulp || eq_half_ulp) {
// res = +0.0 * 10^expmin
res.w[1] = 0x0000000000000000ull;
res.w[0] = 0x0000000000000000ull;
} else { // if (gt_half_ulp)
// res = +1 * 10^expmin
res.w[1] = 0x0000000000000000ull;
res.w[0] = 0x0000000000000001ull;
}
e4 = expmin;
} else { // if (x0 > q4)
// the second rounding is for 0.0...d(0)d(1)...d(q4-1) * 10^emin
res.w[1] = 0;
res.w[0] = 0;
e4 = expmin;
is_inexact_lt_midpoint = 1;
}
// avoid a double rounding error
if ((is_inexact_gt_midpoint0 || is_midpoint_lt_even0) &&
is_midpoint_lt_even) { // double rounding error upward
// res = res - 1
res.w[0]--;
if (res.w[0] == 0xffffffffffffffffull)
res.w[1]--;
// Note: a double rounding error upward is not possible; for this
// the result after the first rounding would have to be 99...95
// (35 digits in all), possibly followed by a number of zeros; this
// not possible for f * f + 0
is_midpoint_lt_even = 0;
is_inexact_lt_midpoint = 1;
} else if ((is_inexact_lt_midpoint0 || is_midpoint_gt_even0) &&
is_midpoint_gt_even) { // double rounding error downward
// res = res + 1
res.w[0]++;
if (res.w[0] == 0)
res.w[1]++;
is_midpoint_gt_even = 0;
is_inexact_gt_midpoint = 1;
} else if (!is_midpoint_lt_even && !is_midpoint_gt_even &&
!is_inexact_lt_midpoint && !is_inexact_gt_midpoint) {
// if this second rounding was exact the result may still be
// inexact because of the first rounding
if (is_inexact_gt_midpoint0 || is_midpoint_lt_even0) {
is_inexact_gt_midpoint = 1;
}
if (is_inexact_lt_midpoint0 || is_midpoint_gt_even0) {
is_inexact_lt_midpoint = 1;
}
} else if (is_midpoint_gt_even &&
(is_inexact_gt_midpoint0 || is_midpoint_lt_even0)) {
// pulled up to a midpoint
is_inexact_lt_midpoint = 1;
is_inexact_gt_midpoint = 0;
is_midpoint_lt_even = 0;
is_midpoint_gt_even = 0;
} else if (is_midpoint_lt_even &&
(is_inexact_lt_midpoint0 || is_midpoint_gt_even0)) {
// pulled down to a midpoint
is_inexact_lt_midpoint = 0;
is_inexact_gt_midpoint = 1;
is_midpoint_lt_even = 0;
is_midpoint_gt_even = 0;
} else {
;
}
} else { // if e4 >= emin then q4 < P and the result is tiny and exact
if (e3 < e4) {
// if (e3 < e4) the preferred exponent is e3
// return (C4 * 10^scale) * 10^(e4 - scale)
// where scale = min (p34-q4, (e4 - e3))
scale = p34 - q4;
ind = e4 - e3;
if (ind < scale)
scale = ind;
if (scale == 0) {
; // res and e4 are unchanged
} else if (q4 <= 19) { // C4 fits in 64 bits
if (scale <= 19) { // 10^scale fits in 64 bits
// 64 x 64 res.w[0] * ten2k64[scale]
__mul_64x64_to_128MACH (res, res.w[0], ten2k64[scale]);
} else { // 10^scale fits in 128 bits
// 64 x 128 res.w[0] * ten2k128[scale - 20]
__mul_128x64_to_128 (res, res.w[0], ten2k128[scale - 20]);
}
} else { // res fits in 128 bits, but 10^scale must fit in 64 bits
// 64 x 128 ten2k64[scale] * C3
__mul_128x64_to_128 (res, ten2k64[scale], res);
}
// subtract scale from the exponent
e4 = e4 - scale;
}
}
// check for inexact result
if (is_inexact_lt_midpoint || is_inexact_gt_midpoint ||
is_midpoint_lt_even || is_midpoint_gt_even) {
// set the inexact flag and the underflow flag
*pfpsf |= INEXACT_EXCEPTION;
*pfpsf |= UNDERFLOW_EXCEPTION;
}
res.w[1] = p_sign | ((UINT64) (e4 + 6176) << 49) | res.w[1];
if (rnd_mode != ROUNDING_TO_NEAREST) {
rounding_correction (rnd_mode,
is_inexact_lt_midpoint,
is_inexact_gt_midpoint,
is_midpoint_lt_even, is_midpoint_gt_even,
e4, &res, pfpsf);
}
*pfpsf |= save_fpsf;
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
}
// no overflow, and no underflow for rounding to nearest
res.w[1] = p_sign | ((UINT64) (e4 + 6176) << 49) | res.w[1];
if (rnd_mode != ROUNDING_TO_NEAREST) {
rounding_correction (rnd_mode,
is_inexact_lt_midpoint,
is_inexact_gt_midpoint,
is_midpoint_lt_even, is_midpoint_gt_even,
e4, &res, pfpsf);
// if e4 = expmin && significand < 10^33 => result is tiny (for RD, RZ)
if (e4 == expmin) {
if ((res.w[1] & MASK_COEFF) < 0x0000314dc6448d93ull ||
((res.w[1] & MASK_COEFF) == 0x0000314dc6448d93ull &&
res.w[0] < 0x38c15b0a00000000ull)) {
is_tiny = 1;
}
}
}
if (is_inexact_lt_midpoint || is_inexact_gt_midpoint ||
is_midpoint_lt_even || is_midpoint_gt_even) {
// set the inexact flag
*pfpsf |= INEXACT_EXCEPTION;
if (is_tiny)
*pfpsf |= UNDERFLOW_EXCEPTION;
}
if ((*pfpsf & INEXACT_EXCEPTION) == 0) { // x * y is exact
// need to ensure that the result has the preferred exponent
p_exp = res.w[1] & MASK_EXP;
if (z_exp < p_exp) { // the preferred exponent is z_exp
// signficand of res in C3
C3.w[1] = res.w[1] & MASK_COEFF;
C3.w[0] = res.w[0];
// the number of decimal digits of x * y is q4 <= 34
// Note: the coefficient fits in 128 bits
// return (C3 * 10^scale) * 10^(p_exp - scale)
// where scale = min (p34-q4, (p_exp-z_exp) >> 49)
scale = p34 - q4;
ind = (p_exp - z_exp) >> 49;
if (ind < scale)
scale = ind;
// subtract scale from the exponent
p_exp = p_exp - ((UINT64) scale << 49);
if (scale == 0) {
; // leave res unchanged
} else if (q4 <= 19) { // x * y fits in 64 bits
if (scale <= 19) { // 10^scale fits in 64 bits
// 64 x 64 C3.w[0] * ten2k64[scale]
__mul_64x64_to_128MACH (res, C3.w[0], ten2k64[scale]);
} else { // 10^scale fits in 128 bits
// 64 x 128 C3.w[0] * ten2k128[scale - 20]
__mul_128x64_to_128 (res, C3.w[0], ten2k128[scale - 20]);
}
res.w[1] = p_sign | (p_exp & MASK_EXP) | res.w[1];
} else { // x * y fits in 128 bits, but 10^scale must fit in 64 bits
// 64 x 128 ten2k64[scale] * C3
__mul_128x64_to_128 (res, ten2k64[scale], C3);
res.w[1] = p_sign | (p_exp & MASK_EXP) | res.w[1];
}
} // else leave the result as it is, because p_exp <= z_exp
}
*pfpsf |= save_fpsf;
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
} // else we have f * f + f
// continue with x = f, y = f, z = f
delta = q3 + e3 - q4 - e4;
delta_ge_zero:
if (delta >= 0) {
if (p34 <= delta - 1 || // Case (1')
(p34 == delta && e3 + 6176 < p34 - q3)) { // Case (1''A)
// check for overflow, which can occur only in Case (1')
if ((q3 + e3) > (p34 + expmax) && p34 <= delta - 1) {
// e3 > expmax implies p34 <= delta-1 and e3 > expmax is a necessary
// condition for (q3 + e3) > (p34 + expmax)
if (rnd_mode == ROUNDING_TO_NEAREST) {
res.w[1] = z_sign | 0x7800000000000000ull; // +/-inf
res.w[0] = 0x0000000000000000ull;
*pfpsf |= (INEXACT_EXCEPTION | OVERFLOW_EXCEPTION);
} else {
if (p_sign == z_sign) {
is_inexact_lt_midpoint = 1;
} else {
is_inexact_gt_midpoint = 1;
}
// q3 <= p34; if (q3 < p34) scale C3 up by 10^(p34-q3)
scale = p34 - q3;
if (scale == 0) {
res.w[1] = z_sign | C3.w[1];
res.w[0] = C3.w[0];
} else {
if (q3 <= 19) { // C3 fits in 64 bits
if (scale <= 19) { // 10^scale fits in 64 bits
// 64 x 64 C3.w[0] * ten2k64[scale]
__mul_64x64_to_128MACH (res, C3.w[0], ten2k64[scale]);
} else { // 10^scale fits in 128 bits
// 64 x 128 C3.w[0] * ten2k128[scale - 20]
__mul_128x64_to_128 (res, C3.w[0],
ten2k128[scale - 20]);
}
} else { // C3 fits in 128 bits, but 10^scale must fit in 64 bits
// 64 x 128 ten2k64[scale] * C3
__mul_128x64_to_128 (res, ten2k64[scale], C3);
}
// the coefficient in res has q3 + scale = p34 digits
}
e3 = e3 - scale;
res.w[1] = z_sign | res.w[1];
rounding_correction (rnd_mode,
is_inexact_lt_midpoint,
is_inexact_gt_midpoint,
is_midpoint_lt_even, is_midpoint_gt_even,
e3, &res, pfpsf);
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
}
// res = z
if (q3 < p34) { // the preferred exponent is z_exp - (p34 - q3)
// return (C3 * 10^scale) * 10^(z_exp - scale)
// where scale = min (p34-q3, z_exp-EMIN)
scale = p34 - q3;
ind = e3 + 6176;
if (ind < scale)
scale = ind;
if (scale == 0) {
res.w[1] = C3.w[1];
res.w[0] = C3.w[0];
} else if (q3 <= 19) { // z fits in 64 bits
if (scale <= 19) { // 10^scale fits in 64 bits
// 64 x 64 C3.w[0] * ten2k64[scale]
__mul_64x64_to_128MACH (res, C3.w[0], ten2k64[scale]);
} else { // 10^scale fits in 128 bits
// 64 x 128 C3.w[0] * ten2k128[scale - 20]
__mul_128x64_to_128 (res, C3.w[0], ten2k128[scale - 20]);
}
} else { // z fits in 128 bits, but 10^scale must fit in 64 bits
// 64 x 128 ten2k64[scale] * C3
__mul_128x64_to_128 (res, ten2k64[scale], C3);
}
// the coefficient in res has q3 + scale digits
// subtract scale from the exponent
z_exp = z_exp - ((UINT64) scale << 49);
e3 = e3 - scale;
res.w[1] = z_sign | (z_exp & MASK_EXP) | res.w[1];
if (scale + q3 < p34)
*pfpsf |= UNDERFLOW_EXCEPTION;
} else {
scale = 0;
res.w[1] = z_sign | ((UINT64) (e3 + 6176) << 49) | C3.w[1];
res.w[0] = C3.w[0];
}
// use the following to avoid double rounding errors when operating on
// mixed formats in rounding to nearest, and for correcting the result
// if not rounding to nearest
if ((p_sign != z_sign) && (delta == (q3 + scale + 1))) {
// there is a gap of exactly one digit between the scaled C3 and C4
// C3 * 10^ scale = 10^(q3+scale-1) <=> C3 = 10^(q3-1) is special case
if ((q3 <= 19 && C3.w[0] != ten2k64[q3 - 1]) ||
(q3 == 20 && (C3.w[1] != 0 || C3.w[0] != ten2k64[19])) ||
(q3 >= 21 && (C3.w[1] != ten2k128[q3 - 21].w[1] ||
C3.w[0] != ten2k128[q3 - 21].w[0]))) {
// C3 * 10^ scale != 10^(q3-1)
// if ((res.w[1] & MASK_COEFF) != 0x0000314dc6448d93ull ||
// res.w[0] != 0x38c15b0a00000000ull) { // C3 * 10^scale != 10^33
is_inexact_gt_midpoint = 1; // if (z_sign), set as if for abs. value
} else { // if C3 * 10^scale = 10^(q3+scale-1)
// ok from above e3 = (z_exp >> 49) - 6176;
// the result is always inexact
if (q4 == 1) {
R64 = C4.w[0];
} else {
// if q4 > 1 then truncate C4 from q4 digits to 1 digit;
// x = q4-1, 1 <= x <= 67 and check if this operation is exact
if (q4 <= 18) { // 2 <= q4 <= 18
round64_2_18 (q4, q4 - 1, C4.w[0], &R64, &incr_exp,
&is_midpoint_lt_even, &is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
} else if (q4 <= 38) {
P128.w[1] = C4.w[1];
P128.w[0] = C4.w[0];
round128_19_38 (q4, q4 - 1, P128, &R128, &incr_exp,
&is_midpoint_lt_even,
&is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
R64 = R128.w[0]; // one decimal digit
} else if (q4 <= 57) {
P192.w[2] = C4.w[2];
P192.w[1] = C4.w[1];
P192.w[0] = C4.w[0];
round192_39_57 (q4, q4 - 1, P192, &R192, &incr_exp,
&is_midpoint_lt_even,
&is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
R64 = R192.w[0]; // one decimal digit
} else { // if (q4 <= 68)
round256_58_76 (q4, q4 - 1, C4, &R256, &incr_exp,
&is_midpoint_lt_even,
&is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
R64 = R256.w[0]; // one decimal digit
}
if (incr_exp) {
R64 = 10;
}
}
if (q4 == 1 && C4.w[0] == 5) {
is_inexact_lt_midpoint = 0;
is_inexact_gt_midpoint = 0;
is_midpoint_lt_even = 1;
is_midpoint_gt_even = 0;
} else if ((e3 == expmin) ||
R64 < 5 || (R64 == 5 && is_inexact_gt_midpoint)) {
// result does not change
is_inexact_lt_midpoint = 0;
is_inexact_gt_midpoint = 1;
is_midpoint_lt_even = 0;
is_midpoint_gt_even = 0;
} else {
is_inexact_lt_midpoint = 1;
is_inexact_gt_midpoint = 0;
is_midpoint_lt_even = 0;
is_midpoint_gt_even = 0;
// result decremented is 10^(q3+scale) - 1
if ((q3 + scale) <= 19) {
res.w[1] = 0;
res.w[0] = ten2k64[q3 + scale];
} else { // if ((q3 + scale + 1) <= 35)
res.w[1] = ten2k128[q3 + scale - 20].w[1];
res.w[0] = ten2k128[q3 + scale - 20].w[0];
}
res.w[0] = res.w[0] - 1; // borrow never occurs
z_exp = z_exp - EXP_P1;
e3 = e3 - 1;
res.w[1] = z_sign | ((UINT64) (e3 + 6176) << 49) | res.w[1];
}
if (e3 == expmin) {
if (R64 < 5 || (R64 == 5 && !is_inexact_lt_midpoint)) {
; // result not tiny (in round-to-nearest mode)
} else {
*pfpsf |= UNDERFLOW_EXCEPTION;
}
}
} // end 10^(q3+scale-1)
// set the inexact flag
*pfpsf |= INEXACT_EXCEPTION;
} else {
if (p_sign == z_sign) {
// if (z_sign), set as if for absolute value
is_inexact_lt_midpoint = 1;
} else { // if (p_sign != z_sign)
// if (z_sign), set as if for absolute value
is_inexact_gt_midpoint = 1;
}
*pfpsf |= INEXACT_EXCEPTION;
}
// the result is always inexact => set the inexact flag
// Determine tininess:
// if (exp > expmin)
// the result is not tiny
// else // if exp = emin
// if (q3 + scale < p34)
// the result is tiny
// else // if (q3 + scale = p34)
// if (C3 * 10^scale > 10^33)
// the result is not tiny
// else // if C3 * 10^scale = 10^33
// if (xy * z > 0)
// the result is not tiny
// else // if (xy * z < 0)
// if (z > 0)
// if rnd_mode != RP
// the result is tiny
// else // if RP
// the result is not tiny
// else // if (z < 0)
// if rnd_mode != RM
// the result is tiny
// else // if RM
// the result is not tiny
// endif
// endif
// endif
// endif
// endif
// endif
if ((e3 == expmin && (q3 + scale) < p34) ||
(e3 == expmin && (q3 + scale) == p34 &&
(res.w[1] & MASK_COEFF) == 0x0000314dc6448d93ull && // 10^33_high
res.w[0] == 0x38c15b0a00000000ull && // 10^33_low
z_sign != p_sign && ((!z_sign && rnd_mode != ROUNDING_UP) ||
(z_sign && rnd_mode != ROUNDING_DOWN)))) {
*pfpsf |= UNDERFLOW_EXCEPTION;
}
if (rnd_mode != ROUNDING_TO_NEAREST) {
rounding_correction (rnd_mode,
is_inexact_lt_midpoint,
is_inexact_gt_midpoint,
is_midpoint_lt_even, is_midpoint_gt_even,
e3, &res, pfpsf);
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
} else if (p34 == delta) { // Case (1''B)
// because Case (1''A) was treated above, e3 + 6176 >= p34 - q3
// and C3 can be scaled up to p34 digits if needed
// scale C3 to p34 digits if needed
scale = p34 - q3; // 0 <= scale <= p34 - 1
if (scale == 0) {
res.w[1] = C3.w[1];
res.w[0] = C3.w[0];
} else if (q3 <= 19) { // z fits in 64 bits
if (scale <= 19) { // 10^scale fits in 64 bits
// 64 x 64 C3.w[0] * ten2k64[scale]
__mul_64x64_to_128MACH (res, C3.w[0], ten2k64[scale]);
} else { // 10^scale fits in 128 bits
// 64 x 128 C3.w[0] * ten2k128[scale - 20]
__mul_128x64_to_128 (res, C3.w[0], ten2k128[scale - 20]);
}
} else { // z fits in 128 bits, but 10^scale must fit in 64 bits
// 64 x 128 ten2k64[scale] * C3
__mul_128x64_to_128 (res, ten2k64[scale], C3);
}
// subtract scale from the exponent
z_exp = z_exp - ((UINT64) scale << 49);
e3 = e3 - scale;
// now z_sign, z_exp, and res correspond to a z scaled to p34 = 34 digits
// determine whether x * y is less than, equal to, or greater than
// 1/2 ulp (z)
if (q4 <= 19) {
if (C4.w[0] < midpoint64[q4 - 1]) { // < 1/2 ulp
lt_half_ulp = 1;
} else if (C4.w[0] == midpoint64[q4 - 1]) { // = 1/2 ulp
eq_half_ulp = 1;
} else { // > 1/2 ulp
gt_half_ulp = 1;
}
} else if (q4 <= 38) {
if (C4.w[2] == 0 && (C4.w[1] < midpoint128[q4 - 20].w[1] ||
(C4.w[1] == midpoint128[q4 - 20].w[1] &&
C4.w[0] < midpoint128[q4 - 20].w[0]))) { // < 1/2 ulp
lt_half_ulp = 1;
} else if (C4.w[2] == 0 && C4.w[1] == midpoint128[q4 - 20].w[1] &&
C4.w[0] == midpoint128[q4 - 20].w[0]) { // = 1/2 ulp
eq_half_ulp = 1;
} else { // > 1/2 ulp
gt_half_ulp = 1;
}
} else if (q4 <= 58) {
if (C4.w[3] == 0 && (C4.w[2] < midpoint192[q4 - 39].w[2] ||
(C4.w[2] == midpoint192[q4 - 39].w[2] &&
C4.w[1] < midpoint192[q4 - 39].w[1]) ||
(C4.w[2] == midpoint192[q4 - 39].w[2] &&
C4.w[1] == midpoint192[q4 - 39].w[1] &&
C4.w[0] < midpoint192[q4 - 39].w[0]))) { // < 1/2 ulp
lt_half_ulp = 1;
} else if (C4.w[3] == 0 && C4.w[2] == midpoint192[q4 - 39].w[2] &&
C4.w[1] == midpoint192[q4 - 39].w[1] &&
C4.w[0] == midpoint192[q4 - 39].w[0]) { // = 1/2 ulp
eq_half_ulp = 1;
} else { // > 1/2 ulp
gt_half_ulp = 1;
}
} else {
if (C4.w[3] < midpoint256[q4 - 59].w[3] ||
(C4.w[3] == midpoint256[q4 - 59].w[3] &&
C4.w[2] < midpoint256[q4 - 59].w[2]) ||
(C4.w[3] == midpoint256[q4 - 59].w[3] &&
C4.w[2] == midpoint256[q4 - 59].w[2] &&
C4.w[1] < midpoint256[q4 - 59].w[1]) ||
(C4.w[3] == midpoint256[q4 - 59].w[3] &&
C4.w[2] == midpoint256[q4 - 59].w[2] &&
C4.w[1] == midpoint256[q4 - 59].w[1] &&
C4.w[0] < midpoint256[q4 - 59].w[0])) { // < 1/2 ulp
lt_half_ulp = 1;
} else if (C4.w[3] == midpoint256[q4 - 59].w[3] &&
C4.w[2] == midpoint256[q4 - 59].w[2] &&
C4.w[1] == midpoint256[q4 - 59].w[1] &&
C4.w[0] == midpoint256[q4 - 59].w[0]) { // = 1/2 ulp
eq_half_ulp = 1;
} else { // > 1/2 ulp
gt_half_ulp = 1;
}
}
if (p_sign == z_sign) {
if (lt_half_ulp) {
res.w[1] = z_sign | (z_exp & MASK_EXP) | res.w[1];
// use the following to avoid double rounding errors when operating on
// mixed formats in rounding to nearest
is_inexact_lt_midpoint = 1; // if (z_sign), as if for absolute value
} else if ((eq_half_ulp && (res.w[0] & 0x01)) || gt_half_ulp) {
// add 1 ulp to the significand
res.w[0]++;
if (res.w[0] == 0x0ull)
res.w[1]++;
// check for rounding overflow, when coeff == 10^34
if ((res.w[1] & MASK_COEFF) == 0x0001ed09bead87c0ull &&
res.w[0] == 0x378d8e6400000000ull) { // coefficient = 10^34
e3 = e3 + 1;
// coeff = 10^33
z_exp = ((UINT64) (e3 + 6176) << 49) & MASK_EXP;
res.w[1] = 0x0000314dc6448d93ull;
res.w[0] = 0x38c15b0a00000000ull;
}
// end add 1 ulp
res.w[1] = z_sign | (z_exp & MASK_EXP) | res.w[1];
if (eq_half_ulp) {
is_midpoint_lt_even = 1; // if (z_sign), as if for absolute value
} else {
is_inexact_gt_midpoint = 1; // if (z_sign), as if for absolute value
}
} else { // if (eq_half_ulp && !(res.w[0] & 0x01))
// leave unchanged
res.w[1] = z_sign | (z_exp & MASK_EXP) | res.w[1];
is_midpoint_gt_even = 1; // if (z_sign), as if for absolute value
}
// the result is always inexact, and never tiny
// set the inexact flag
*pfpsf |= INEXACT_EXCEPTION;
// check for overflow
if (e3 > expmax && rnd_mode == ROUNDING_TO_NEAREST) {
res.w[1] = z_sign | 0x7800000000000000ull; // +/-inf
res.w[0] = 0x0000000000000000ull;
*pfpsf |= (INEXACT_EXCEPTION | OVERFLOW_EXCEPTION);
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
}
if (rnd_mode != ROUNDING_TO_NEAREST) {
rounding_correction (rnd_mode,
is_inexact_lt_midpoint,
is_inexact_gt_midpoint,
is_midpoint_lt_even, is_midpoint_gt_even,
e3, &res, pfpsf);
z_exp = res.w[1] & MASK_EXP;
}
} else { // if (p_sign != z_sign)
// consider two cases, because C3 * 10^scale = 10^33 is a special case
if (res.w[1] != 0x0000314dc6448d93ull ||
res.w[0] != 0x38c15b0a00000000ull) { // C3 * 10^scale != 10^33
if (lt_half_ulp) {
res.w[1] = z_sign | (z_exp & MASK_EXP) | res.w[1];
// use the following to avoid double rounding errors when operating
// on mixed formats in rounding to nearest
is_inexact_gt_midpoint = 1; // if (z_sign), as if for absolute value
} else if ((eq_half_ulp && (res.w[0] & 0x01)) || gt_half_ulp) {
// subtract 1 ulp from the significand
res.w[0]--;
if (res.w[0] == 0xffffffffffffffffull)
res.w[1]--;
res.w[1] = z_sign | (z_exp & MASK_EXP) | res.w[1];
if (eq_half_ulp) {
is_midpoint_gt_even = 1; // if (z_sign), as if for absolute value
} else {
is_inexact_lt_midpoint = 1; //if(z_sign), as if for absolute value
}
} else { // if (eq_half_ulp && !(res.w[0] & 0x01))
// leave unchanged
res.w[1] = z_sign | (z_exp & MASK_EXP) | res.w[1];
is_midpoint_lt_even = 1; // if (z_sign), as if for absolute value
}
// the result is always inexact, and never tiny
// check for overflow for RN
if (e3 > expmax) {
if (rnd_mode == ROUNDING_TO_NEAREST) {
res.w[1] = z_sign | 0x7800000000000000ull; // +/-inf
res.w[0] = 0x0000000000000000ull;
*pfpsf |= (INEXACT_EXCEPTION | OVERFLOW_EXCEPTION);
} else {
rounding_correction (rnd_mode,
is_inexact_lt_midpoint,
is_inexact_gt_midpoint,
is_midpoint_lt_even,
is_midpoint_gt_even, e3, &res,
pfpsf);
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
}
// set the inexact flag
*pfpsf |= INEXACT_EXCEPTION;
if (rnd_mode != ROUNDING_TO_NEAREST) {
rounding_correction (rnd_mode,
is_inexact_lt_midpoint,
is_inexact_gt_midpoint,
is_midpoint_lt_even,
is_midpoint_gt_even, e3, &res, pfpsf);
}
z_exp = res.w[1] & MASK_EXP;
} else { // if C3 * 10^scale = 10^33
e3 = (z_exp >> 49) - 6176;
if (e3 > expmin) {
// the result is exact if exp > expmin and C4 = d*10^(q4-1),
// where d = 1, 2, 3, ..., 9; it could be tiny too, but exact
if (q4 == 1) {
// if q4 = 1 the result is exact
// result coefficient = 10^34 - C4
res.w[1] = 0x0001ed09bead87c0ull;
res.w[0] = 0x378d8e6400000000ull - C4.w[0];
z_exp = z_exp - EXP_P1;
e3 = e3 - 1;
res.w[1] = z_sign | (z_exp & MASK_EXP) | res.w[1];
} else {
// if q4 > 1 then truncate C4 from q4 digits to 1 digit;
// x = q4-1, 1 <= x <= 67 and check if this operation is exact
if (q4 <= 18) { // 2 <= q4 <= 18
round64_2_18 (q4, q4 - 1, C4.w[0], &R64, &incr_exp,
&is_midpoint_lt_even,
&is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
} else if (q4 <= 38) {
P128.w[1] = C4.w[1];
P128.w[0] = C4.w[0];
round128_19_38 (q4, q4 - 1, P128, &R128, &incr_exp,
&is_midpoint_lt_even,
&is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
R64 = R128.w[0]; // one decimal digit
} else if (q4 <= 57) {
P192.w[2] = C4.w[2];
P192.w[1] = C4.w[1];
P192.w[0] = C4.w[0];
round192_39_57 (q4, q4 - 1, P192, &R192, &incr_exp,
&is_midpoint_lt_even,
&is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
R64 = R192.w[0]; // one decimal digit
} else { // if (q4 <= 68)
round256_58_76 (q4, q4 - 1, C4, &R256, &incr_exp,
&is_midpoint_lt_even,
&is_midpoint_gt_even,
&is_inexact_lt_midpoint,
&is_inexact_gt_midpoint);
R64 = R256.w[0]; // one decimal digit
}
if (!is_midpoint_lt_even && !is_midpoint_gt_even &&
!is_inexact_lt_midpoint && !is_inexact_gt_midpoint) {
// the result is exact: 10^34 - R64
// incr_exp = 0 with certainty
z_exp = z_exp - EXP_P1;
e3 = e3 - 1;
res.w[1] =
z_sign | (z_exp & MASK_EXP) | 0x0001ed09bead87c0ull;
res.w[0] = 0x378d8e6400000000ull - R64;
} else {
// We want R64 to be the top digit of C4, but we actually
// obtained (C4 * 10^(-q4+1))RN; a correction may be needed,
// because the top digit is (C4 * 10^(-q4+1))RZ
// however, if incr_exp = 1 then R64 = 10 with certainty
if (incr_exp) {
R64 = 10;
}
// the result is inexact as C4 has more than 1 significant digit
// and C3 * 10^scale = 10^33
// example of case that is treated here:
// 100...0 * 10^e3 - 0.41 * 10^e3 =
// 0999...9.59 * 10^e3 -> rounds to 99...96*10^(e3-1)
// note that (e3 > expmin}
// in order to round, subtract R64 from 10^34 and then compare
// C4 - R64 * 10^(q4-1) with 1/2 ulp
// calculate 10^34 - R64
res.w[1] = 0x0001ed09bead87c0ull;
res.w[0] = 0x378d8e6400000000ull - R64;
z_exp = z_exp - EXP_P1; // will be OR-ed with sign & significand
// calculate C4 - R64 * 10^(q4-1); this is a rare case and
// R64 is small, 1 <= R64 <= 9
e3 = e3 - 1;
if (is_inexact_lt_midpoint) {
is_inexact_lt_midpoint = 0;
is_inexact_gt_midpoint = 1;
} else if (is_inexact_gt_midpoint) {
is_inexact_gt_midpoint = 0;
is_inexact_lt_midpoint = 1;
} else if (is_midpoint_lt_even) {
is_midpoint_lt_even = 0;
is_midpoint_gt_even = 1;
} else if (is_midpoint_gt_even) {
is_midpoint_gt_even = 0;
is_midpoint_lt_even = 1;
} else {
;
}
// the result is always inexact, and never tiny
// check for overflow for RN
if (e3 > expmax) {
if (rnd_mode == ROUNDING_TO_NEAREST) {
res.w[1] = z_sign | 0x7800000000000000ull; // +/-inf
res.w[0] = 0x0000000000000000ull;
*pfpsf |= (INEXACT_EXCEPTION | OVERFLOW_EXCEPTION);
} else {
rounding_correction (rnd_mode,
is_inexact_lt_midpoint,
is_inexact_gt_midpoint,
is_midpoint_lt_even,
is_midpoint_gt_even, e3, &res,
pfpsf);
}
*ptr_is_midpoint_lt_even = is_midpoint_lt_even;
*ptr_is_midpoint_gt_even = is_midpoint_gt_even;
*ptr_is_inexact_lt_midpoint = is_inexact_lt_midpoint;
*ptr_is_inexact_gt_midpoint = is_inexact_gt_midpoint;
BID_SWAP128 (res);
BID_RETURN (res)
}
// set the inexact flag
*pfpsf |= INEXACT_EXCEPTION;
res.w[1] =
z_sign | ((UINT64) (e3 + 6176) << 49) | res.w[1];
if (rnd_mode != ROUNDING_TO_NEAREST) {
rounding_correction (rnd_mode,
is_inexact_lt_midpoint,
is_inexact_gt_midpoint,
is_midpoint_lt_even,
is_midpoint_gt_even, e3, &res,
pfpsf);
}
z_exp = res.w[1] & MASK_EXP;
} // end result is inexact
} // end q4 > 1
} else { // if (e3 = emin)
// if e3 = expmin the result is also tiny (the condition for
// tininess is C4 > 050...0 [q4 digits] which is met because
// the msd of C4 is not zero)
// the result is tiny and inexact in all rounding modes;