| /* Round to nearest integer value, rounding halfway cases to even. |
| dbl-64/wordsize-64 version. |
| Copyright (C) 2016-2018 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 |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <math.h> |
| #include <math_private.h> |
| #include <libm-alias-double.h> |
| #include <stdint.h> |
| |
| #define BIAS 0x3ff |
| #define MANT_DIG 53 |
| #define MAX_EXP (2 * BIAS + 1) |
| |
| double |
| __roundeven (double x) |
| { |
| 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; |
| } |
| hidden_def (__roundeven) |
| libm_alias_double (__roundeven, roundeven) |
