mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-25 14:30:06 +00:00
78 lines
2.5 KiB
C
78 lines
2.5 KiB
C
/* Round to nearest integer value, rounding halfway cases to even.
|
|
Copyright (C) 2016-2024 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library 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
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, see
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#define NO_MATH_REDIRECT
|
|
#include <math.h>
|
|
#include <math_private.h>
|
|
#include <libm-alias-double.h>
|
|
#include <stdint.h>
|
|
#include <math-use-builtins.h>
|
|
|
|
#define BIAS 0x3ff
|
|
#define MANT_DIG 53
|
|
#define MAX_EXP (2 * BIAS + 1)
|
|
|
|
double
|
|
__roundeven (double x)
|
|
{
|
|
#if USE_ROUNDEVEN_BUILTIN
|
|
return __builtin_roundeven (x);
|
|
#else
|
|
uint64_t ix, ux;
|
|
EXTRACT_WORDS64 (ix, x);
|
|
ux = ix & 0x7fffffffffffffffULL;
|
|
int exponent = ux >> (MANT_DIG - 1);
|
|
if (exponent >= BIAS + MANT_DIG - 1)
|
|
{
|
|
/* Integer, infinity or NaN. */
|
|
if (exponent == MAX_EXP)
|
|
/* Infinity or NaN; quiet signaling NaNs. */
|
|
return x + x;
|
|
else
|
|
return x;
|
|
}
|
|
else if (exponent >= BIAS)
|
|
{
|
|
/* At least 1; not necessarily an integer. Locate the bits with
|
|
exponents 0 and -1 (when the unbiased exponent is 0, the bit
|
|
with exponent 0 is implicit, but as the bias is odd it is OK
|
|
to take it from the low bit of the exponent). */
|
|
int int_pos = (BIAS + MANT_DIG - 1) - exponent;
|
|
int half_pos = int_pos - 1;
|
|
uint64_t half_bit = 1ULL << half_pos;
|
|
uint64_t int_bit = 1ULL << int_pos;
|
|
if ((ix & (int_bit | (half_bit - 1))) != 0)
|
|
/* Carry into the exponent works correctly. No need to test
|
|
whether HALF_BIT is set. */
|
|
ix += half_bit;
|
|
ix &= ~(int_bit - 1);
|
|
}
|
|
else if (exponent == BIAS - 1 && ux > 0x3fe0000000000000ULL)
|
|
/* Interval (0.5, 1). */
|
|
ix = (ix & 0x8000000000000000ULL) | 0x3ff0000000000000ULL;
|
|
else
|
|
/* Rounds to 0. */
|
|
ix &= 0x8000000000000000ULL;
|
|
INSERT_WORDS64 (x, ix);
|
|
return x;
|
|
#endif /* ! USE_ROUNDEVEN_BUILTIN */
|
|
}
|
|
#ifndef __roundeven
|
|
libm_alias_double (__roundeven, roundeven)
|
|
#endif
|