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gcc/libgcc/config/libbid/bid64_rem.c
H.J. Lu 200359e888 Merged with libbbid branch at revision 126349. 
From-SVN: r126353
2007-07-04 22:36:50 -07:00

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/* Copyright (C) 2007 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 2, or (at your option) any later
version.
In addition to the permissions in the GNU General Public License, the
Free Software Foundation gives you unlimited permission to link the
compiled version of this file into combinations with other programs,
and to distribute those combinations without any restriction coming
from the use of this file. (The General Public License restrictions
do apply in other respects; for example, they cover modification of
the file, and distribution when not linked into a combine
executable.)
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.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING. If not, write to the Free
Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA. */
/*****************************************************************************
* BID64 remainder
*****************************************************************************
*
* Algorithm description:
*
* if(exponent_x < exponent_y)
* scale coefficient_y so exponents are aligned
* perform coefficient divide (64-bit integer divide), unless
* coefficient_y is longer than 64 bits (clearly larger
* than coefficient_x)
* else // exponent_x > exponent_y
* use a loop to scale coefficient_x to 18_digits, divide by
* coefficient_y (64-bit integer divide), calculate remainder
* as new_coefficient_x and repeat until final remainder is obtained
* (when new_exponent_x < exponent_y)
*
****************************************************************************/
#include "bid_internal.h"
#define MAX_FORMAT_DIGITS 16
#define DECIMAL_EXPONENT_BIAS 398
#define MASK_BINARY_EXPONENT 0x7ff0000000000000ull
#define BINARY_EXPONENT_BIAS 0x3ff
#define UPPER_EXPON_LIMIT 51
#if DECIMAL_CALL_BY_REFERENCE
void
__bid64_rem (UINT64 * pres, UINT64 * px,
UINT64 *
py _RND_MODE_PARAM _EXC_FLAGS_PARAM _EXC_MASKS_PARAM
_EXC_INFO_PARAM) {
UINT64 x, y;
#else
UINT64
__bid64_rem (UINT64 x,
UINT64 y _RND_MODE_PARAM _EXC_FLAGS_PARAM
_EXC_MASKS_PARAM _EXC_INFO_PARAM) {
#endif
UINT128 CY;
UINT64 sign_x, sign_y, coefficient_x, coefficient_y, res;
UINT64 Q, R, R2, T;
int_float tempx;
int exponent_x = 0, exponent_y, bin_expon, e_scale;
int digits_x, diff_expon;
#if DECIMAL_CALL_BY_REFERENCE
x = *px;
y = *py;
#endif
// unpack arguments, check for NaN or Infinity
if (!unpack_BID64 (&sign_x, &exponent_x, &coefficient_x, x)) {
// x is Inf. or NaN or 0
#ifdef SET_STATUS_FLAGS
if ((y & SNAN_MASK64) == SNAN_MASK64) // y is sNaN
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
// test if x is NaN
if ((x & 0x7c00000000000000ull) == 0x7c00000000000000ull) {
#ifdef SET_STATUS_FLAGS
if (((x & SNAN_MASK64) == SNAN_MASK64))
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
res = x & QUIET_MASK64;;
BID_RETURN (res);
}
// x is Infinity?
if ((x & 0x7800000000000000ull) == 0x7800000000000000ull) {
#ifdef SET_STATUS_FLAGS
if (((y & NAN_MASK64) != NAN_MASK64))
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
// return NaN
res = 0x7c00000000000000ull;
BID_RETURN (res);
}
// x is 0
// return x if y != 0
if (((y & 0x7800000000000000ull) < 0x7800000000000000ull) &&
(((y & 0x6000000000000000ull) == 0x6000000000000000ull)
|| (y << (64 - 53)))) {
if ((y & 0x6000000000000000ull) == 0x6000000000000000ull)
exponent_y = (y >> 51) & 0x3ff;
else
exponent_y = (y >> 53) & 0x3ff;
if (exponent_y < exponent_x)
exponent_x = exponent_y;
x = exponent_x;
x <<= 53;
res = x | sign_x;
BID_RETURN (res);
}
}
if (!unpack_BID64 (&sign_y, &exponent_y, &coefficient_y, y)) {
// y is Inf. or NaN
// test if y is NaN
if ((y & 0x7c00000000000000ull) == 0x7c00000000000000ull) {
#ifdef SET_STATUS_FLAGS
if (((y & SNAN_MASK64) == SNAN_MASK64))
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
res = y & QUIET_MASK64;;
BID_RETURN (res);
}
// y is Infinity?
if ((y & 0x7800000000000000ull) == 0x7800000000000000ull) {
res = x;
BID_RETURN (res);
}
// y is 0, return NaN
{
#ifdef SET_STATUS_FLAGS
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
res = 0x7c00000000000000ull;
BID_RETURN (res);
}
}
diff_expon = exponent_x - exponent_y;
if (diff_expon <= 0) {
diff_expon = -diff_expon;
if (diff_expon > 16) {
// |x|<|y| in this case
res = x;
BID_RETURN (res);
}
// set exponent of y to exponent_x, scale coefficient_y
T = __bid_power10_table_128[diff_expon].w[0];
__mul_64x64_to_128 (CY, coefficient_y, T);
if (CY.w[1] || CY.w[0] > (coefficient_x << 1)) {
res = x;
BID_RETURN (res);
}
Q = coefficient_x / CY.w[0];
R = coefficient_x - Q * CY.w[0];
R2 = R + R;
if (R2 > CY.w[0] || (R2 == CY.w[0] && (Q & 1))) {
R = CY.w[0] - R;
sign_x ^= 0x8000000000000000ull;
}
res = very_fast_get_BID64 (sign_x, exponent_x, R);
BID_RETURN (res);
}
while (diff_expon > 0) {
// get number of digits in coeff_x
tempx.d = (float) coefficient_x;
bin_expon = ((tempx.i >> 23) & 0xff) - 0x7f;
digits_x = __bid_estimate_decimal_digits[bin_expon];
// will not use this test, dividend will have 18 or 19 digits
//if(coefficient_x >= __bid_power10_table_128[digits_x].w[0])
// digits_x++;
e_scale = 18 - digits_x;
if (diff_expon >= e_scale) {
diff_expon -= e_scale;
} else {
e_scale = diff_expon;
diff_expon = 0;
}
// scale dividend to 18 or 19 digits
coefficient_x *= __bid_power10_table_128[e_scale].w[0];
// quotient
Q = coefficient_x / coefficient_y;
// remainder
coefficient_x -= Q * coefficient_y;
// check for remainder == 0
if (!coefficient_x) {
res = very_fast_get_BID64_small_mantissa (sign_x, exponent_y, 0);
BID_RETURN (res);
}
}
R2 = coefficient_x + coefficient_x;
if (R2 > coefficient_y || (R2 == coefficient_y && (Q & 1))) {
coefficient_x = coefficient_y - coefficient_x;
sign_x ^= 0x8000000000000000ull;
}
res = very_fast_get_BID64 (sign_x, exponent_y, coefficient_x);
BID_RETURN (res);
}
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