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gcc/libgcc/config/libbid/bid64_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/>. */
#include "bid_internal.h"
#define MAX_FORMAT_DIGITS 16
#define DECIMAL_EXPONENT_BIAS 398
#define MAX_DECIMAL_EXPONENT 767
#if DECIMAL_CALL_BY_REFERENCE
void
bid64_quantize (UINT64 * pres, UINT64 * px,
UINT64 *
py _RND_MODE_PARAM _EXC_FLAGS_PARAM _EXC_MASKS_PARAM
_EXC_INFO_PARAM) {
UINT64 x, y;
#else
UINT64
bid64_quantize (UINT64 x,
UINT64 y _RND_MODE_PARAM _EXC_FLAGS_PARAM
_EXC_MASKS_PARAM _EXC_INFO_PARAM) {
#endif
UINT128 CT;
UINT64 sign_x, sign_y, coefficient_x, coefficient_y, remainder_h, C64,
valid_x;
UINT64 tmp, carry, res;
int_float tempx;
int exponent_x, exponent_y, digits_x, extra_digits, amount, amount2;
int expon_diff, total_digits, bin_expon_cx;
unsigned rmode, status;
#if DECIMAL_CALL_BY_REFERENCE
#if !DECIMAL_GLOBAL_ROUNDING
_IDEC_round rnd_mode = *prnd_mode;
#endif
x = *px;
y = *py;
#endif
valid_x = unpack_BID64 (&sign_x, &exponent_x, &coefficient_x, x);
// unpack arguments, check for NaN or Infinity
if (!unpack_BID64 (&sign_y, &exponent_y, &coefficient_y, y)) {
// Inf. or NaN or 0
#ifdef SET_STATUS_FLAGS
if ((x & SNAN_MASK64) == SNAN_MASK64) // y is sNaN
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
// x=Inf, y=Inf?
if (((coefficient_x << 1) == 0xf000000000000000ull)
&& ((coefficient_y << 1) == 0xf000000000000000ull)) {
res = coefficient_x;
BID_RETURN (res);
}
// Inf or NaN?
if ((y & 0x7800000000000000ull) == 0x7800000000000000ull) {
#ifdef SET_STATUS_FLAGS
if (((y & 0x7e00000000000000ull) == 0x7e00000000000000ull) // sNaN
|| (((y & 0x7c00000000000000ull) == 0x7800000000000000ull) && //Inf
((x & 0x7c00000000000000ull) < 0x7800000000000000ull)))
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
if ((y & NAN_MASK64) != NAN_MASK64)
coefficient_y = 0;
if ((x & NAN_MASK64) != NAN_MASK64) {
res = 0x7c00000000000000ull | (coefficient_y & QUIET_MASK64);
if (((y & NAN_MASK64) != NAN_MASK64) && ((x & NAN_MASK64) == 0x7800000000000000ull))
res = x;
BID_RETURN (res);
}
}
}
// unpack arguments, check for NaN or Infinity
if (!valid_x) {
// x is Inf. or NaN or 0
// Inf or NaN?
if ((x & 0x7800000000000000ull) == 0x7800000000000000ull) {
#ifdef SET_STATUS_FLAGS
if (((x & 0x7e00000000000000ull) == 0x7e00000000000000ull) // sNaN
|| ((x & 0x7c00000000000000ull) == 0x7800000000000000ull)) //Inf
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
if ((x & NAN_MASK64) != NAN_MASK64)
coefficient_x = 0;
res = 0x7c00000000000000ull | (coefficient_x & QUIET_MASK64);
BID_RETURN (res);
}
res = very_fast_get_BID64_small_mantissa (sign_x, exponent_y, 0);
BID_RETURN (res);
}
// get number of decimal digits in coefficient_x
tempx.d = (float) coefficient_x;
bin_expon_cx = ((tempx.i >> 23) & 0xff) - 0x7f;
digits_x = estimate_decimal_digits[bin_expon_cx];
if (coefficient_x >= power10_table_128[digits_x].w[0])
digits_x++;
expon_diff = exponent_x - exponent_y;
total_digits = digits_x + expon_diff;
// check range of scaled coefficient
if ((UINT32) (total_digits + 1) <= 17) {
if (expon_diff >= 0) {
coefficient_x *= power10_table_128[expon_diff].w[0];
res = very_fast_get_BID64 (sign_x, exponent_y, coefficient_x);
BID_RETURN (res);
}
// must round off -expon_diff digits
extra_digits = -expon_diff;
#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
coefficient_x += round_const_table[rmode][extra_digits];
// get P*(2^M[extra_digits])/10^extra_digits
__mul_64x64_to_128 (CT, coefficient_x,
reciprocals10_64[extra_digits]);
// now get P/10^extra_digits: shift C64 right by M[extra_digits]-128
amount = short_recip_scale[extra_digits];
C64 = CT.w[1] >> amount;
#ifndef IEEE_ROUND_NEAREST_TIES_AWAY
#ifndef IEEE_ROUND_NEAREST
if (rnd_mode == 0)
#endif
if (C64 & 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
amount2 = 64 - amount;
remainder_h = 0;
remainder_h--;
remainder_h >>= amount2;
remainder_h = remainder_h & CT.w[1];
// test whether fractional part is 0
if (!remainder_h && (CT.w[0] < reciprocals10_64[extra_digits])) {
C64--;
}
}
#endif
#ifdef SET_STATUS_FLAGS
status = INEXACT_EXCEPTION;
// get remainder
remainder_h = CT.w[1] << (64 - amount);
switch (rmode) {
case ROUNDING_TO_NEAREST:
case ROUNDING_TIES_AWAY:
// test whether fractional part is 0
if ((remainder_h == 0x8000000000000000ull)
&& (CT.w[0] < reciprocals10_64[extra_digits]))
status = EXACT_STATUS;
break;
case ROUNDING_DOWN:
case ROUNDING_TO_ZERO:
if (!remainder_h && (CT.w[0] < reciprocals10_64[extra_digits]))
status = EXACT_STATUS;
//if(!C64 && rmode==ROUNDING_DOWN) sign_s=sign_y;
break;
default:
// round up
__add_carry_out (tmp, carry, CT.w[0],
reciprocals10_64[extra_digits]);
if ((remainder_h >> (64 - amount)) + carry >=
(((UINT64) 1) << amount))
status = EXACT_STATUS;
break;
}
__set_status_flags (pfpsf, status);
#endif
res = very_fast_get_BID64_small_mantissa (sign_x, exponent_y, C64);
BID_RETURN (res);
}
if (total_digits < 0) {
#ifdef SET_STATUS_FLAGS
__set_status_flags (pfpsf, INEXACT_EXCEPTION);
#endif
C64 = 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)
C64 = 1;
#endif
#endif
res = very_fast_get_BID64_small_mantissa (sign_x, exponent_y, C64);
BID_RETURN (res);
}
// else more than 16 digits in coefficient
#ifdef SET_STATUS_FLAGS
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
res = 0x7c00000000000000ull;
BID_RETURN (res);
}
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