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gcc/libgcc/config/libbid/bid128_quantize.c

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/* Copyright (C) 2007, 2009 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/>. */
#define BID_128RES
#include "bid_internal.h"
BID128_FUNCTION_ARG2 (bid128_quantize, x, y)
UINT256 CT;
UINT128 CX, CY, T, CX2, CR, Stemp, res, REM_H, C2N;
UINT64 sign_x, sign_y, remainder_h, carry, CY64, valid_x;
int_float tempx;
int exponent_x, exponent_y, digits_x, extra_digits, amount;
int expon_diff, total_digits, bin_expon_cx, rmode, status;
valid_x = unpack_BID128_value (&sign_x, &exponent_x, &CX, x);
// unpack arguments, check for NaN or Infinity
if (!unpack_BID128_value (&sign_y, &exponent_y, &CY, y)) {
// y is Inf. or NaN
#ifdef SET_STATUS_FLAGS
if ((x.w[1] & SNAN_MASK64) == SNAN_MASK64) // y is sNaN
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
// test if y is NaN
if ((y.w[1] & 0x7c00000000000000ull) == 0x7c00000000000000ull) {
#ifdef SET_STATUS_FLAGS
if ((y.w[1] & 0x7e00000000000000ull) == 0x7e00000000000000ull) {
// set status flags
__set_status_flags (pfpsf, INVALID_EXCEPTION);
}
#endif
if ((x.w[1] & 0x7c00000000000000ull) != 0x7c00000000000000ull) {
res.w[1] = CY.w[1] & QUIET_MASK64;
res.w[0] = CY.w[0];
} else {
res.w[1] = CX.w[1] & QUIET_MASK64;
res.w[0] = CX.w[0];
}
BID_RETURN (res);
}
// y is Infinity?
if ((y.w[1] & 0x7800000000000000ull) == 0x7800000000000000ull) {
// check if x is not Inf.
if (((x.w[1] & 0x7c00000000000000ull) < 0x7800000000000000ull)) {
// return NaN
#ifdef SET_STATUS_FLAGS
// set status flags
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
res.w[1] = 0x7c00000000000000ull;
res.w[0] = 0;
BID_RETURN (res);
} else
if (((x.w[1] & 0x7c00000000000000ull) <= 0x7800000000000000ull)) {
res.w[1] = CX.w[1] & QUIET_MASK64;
res.w[0] = CX.w[0];
BID_RETURN (res);
}
}
}
if (!valid_x) {
// test if x is NaN or Inf
if ((x.w[1] & 0x7c00000000000000ull) == 0x7800000000000000ull) {
#ifdef SET_STATUS_FLAGS
// set status flags
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
res.w[1] = 0x7c00000000000000ull;
res.w[0] = 0;
BID_RETURN (res);
} else if ((x.w[1] & 0x7c00000000000000ull) == 0x7c00000000000000ull) {
if ((x.w[1] & 0x7e00000000000000ull) == 0x7e00000000000000ull) {
#ifdef SET_STATUS_FLAGS
// set status flags
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
}
res.w[1] = CX.w[1] & QUIET_MASK64;
res.w[0] = CX.w[0];
BID_RETURN (res);
}
if (!CX.w[1] && !CX.w[0]) {
get_BID128_very_fast (&res, sign_x, exponent_y, CX);
BID_RETURN (res);
}
}
// get number of decimal digits in coefficient_x
if (CX.w[1]) {
tempx.d = (float) CX.w[1];
bin_expon_cx = ((tempx.i >> 23) & 0xff) - 0x7f + 64;
} else {
tempx.d = (float) CX.w[0];
bin_expon_cx = ((tempx.i >> 23) & 0xff) - 0x7f;
}
digits_x = estimate_decimal_digits[bin_expon_cx];
if (CX.w[1] > power10_table_128[digits_x].w[1]
|| (CX.w[1] == power10_table_128[digits_x].w[1]
&& CX.w[0] >= power10_table_128[digits_x].w[0]))
digits_x++;
expon_diff = exponent_x - exponent_y;
total_digits = digits_x + expon_diff;
if ((UINT32) total_digits <= 34) {
if (expon_diff >= 0) {
T = power10_table_128[expon_diff];
__mul_128x128_low (CX2, T, CX);
get_BID128_very_fast (&res, sign_x, exponent_y, CX2);
BID_RETURN (res);
}
#ifndef IEEE_ROUND_NEAREST_TIES_AWAY
#ifndef IEEE_ROUND_NEAREST
rmode = rnd_mode;
if (sign_x && (unsigned) (rmode - 1) < 2)
rmode = 3 - rmode;
#else
rmode = 0;
#endif
#else
rmode = 0;
#endif
// must round off -expon_diff digits
extra_digits = -expon_diff;
__add_128_128 (CX, CX, round_const_table_128[rmode][extra_digits]);
// get P*(2^M[extra_digits])/10^extra_digits
__mul_128x128_to_256 (CT, CX, reciprocals10_128[extra_digits]);
// now get P/10^extra_digits: shift C64 right by M[extra_digits]-128
amount = recip_scale[extra_digits];
CX2.w[0] = CT.w[2];
CX2.w[1] = CT.w[3];
if (amount >= 64) {
CR.w[1] = 0;
CR.w[0] = CX2.w[1] >> (amount - 64);
} else {
__shr_128 (CR, CX2, amount);
}
#ifndef IEEE_ROUND_NEAREST_TIES_AWAY
#ifndef IEEE_ROUND_NEAREST
if (rnd_mode == 0)
#endif
if (CR.w[0] & 1) {
// check whether fractional part of initial_P/10^extra_digits is
// exactly .5 this is the same as fractional part of
// (initial_P + 0.5*10^extra_digits)/10^extra_digits is exactly zero
// get remainder
if (amount >= 64) {
remainder_h = CX2.w[0] | (CX2.w[1] << (128 - amount));
} else
remainder_h = CX2.w[0] << (64 - amount);
// test whether fractional part is 0
if (!remainder_h
&& (CT.w[1] < reciprocals10_128[extra_digits].w[1]
|| (CT.w[1] == reciprocals10_128[extra_digits].w[1]
&& CT.w[0] < reciprocals10_128[extra_digits].w[0]))) {
CR.w[0]--;
}
}
#endif
#ifdef SET_STATUS_FLAGS
status = INEXACT_EXCEPTION;
// get remainder
if (amount >= 64) {
REM_H.w[1] = (CX2.w[1] << (128 - amount));
REM_H.w[0] = CX2.w[0];
} else {
REM_H.w[1] = CX2.w[0] << (64 - amount);
REM_H.w[0] = 0;
}
switch (rmode) {
case ROUNDING_TO_NEAREST:
case ROUNDING_TIES_AWAY:
// test whether fractional part is 0
if (REM_H.w[1] == 0x8000000000000000ull && !REM_H.w[0]
&& (CT.w[1] < reciprocals10_128[extra_digits].w[1]
|| (CT.w[1] == reciprocals10_128[extra_digits].w[1]
&& CT.w[0] < reciprocals10_128[extra_digits].w[0])))
status = EXACT_STATUS;
break;
case ROUNDING_DOWN:
case ROUNDING_TO_ZERO:
if (!(REM_H.w[1] | REM_H.w[0])
&& (CT.w[1] < reciprocals10_128[extra_digits].w[1]
|| (CT.w[1] == reciprocals10_128[extra_digits].w[1]
&& CT.w[0] < reciprocals10_128[extra_digits].w[0])))
status = EXACT_STATUS;
break;
default:
// round up
__add_carry_out (Stemp.w[0], CY64, CT.w[0],
reciprocals10_128[extra_digits].w[0]);
__add_carry_in_out (Stemp.w[1], carry, CT.w[1],
reciprocals10_128[extra_digits].w[1], CY64);
if (amount < 64) {
C2N.w[1] = 0;
C2N.w[0] = ((UINT64) 1) << amount;
REM_H.w[0] = REM_H.w[1] >> (64 - amount);
REM_H.w[1] = 0;
} else {
C2N.w[1] = ((UINT64) 1) << (amount - 64);
C2N.w[0] = 0;
REM_H.w[1] >>= (128 - amount);
}
REM_H.w[0] += carry;
if (REM_H.w[0] < carry)
REM_H.w[1]++;
if (__unsigned_compare_ge_128 (REM_H, C2N))
status = EXACT_STATUS;
}
__set_status_flags (pfpsf, status);
#endif
get_BID128_very_fast (&res, sign_x, exponent_y, CR);
BID_RETURN (res);
}
if (total_digits < 0) {
CR.w[1] = CR.w[0] = 0;
#ifndef IEEE_ROUND_NEAREST_TIES_AWAY
#ifndef IEEE_ROUND_NEAREST
rmode = rnd_mode;
if (sign_x && (unsigned) (rmode - 1) < 2)
rmode = 3 - rmode;
if (rmode == ROUNDING_UP)
CR.w[0] = 1;
#endif
#endif
#ifdef SET_STATUS_FLAGS
__set_status_flags (pfpsf, INEXACT_EXCEPTION);
#endif
get_BID128_very_fast (&res, sign_x, exponent_y, CR);
BID_RETURN (res);
}
// else more than 34 digits in coefficient
#ifdef SET_STATUS_FLAGS
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
res.w[1] = 0x7c00000000000000ull;
res.w[0] = 0;
BID_RETURN (res);
}
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