]>
Commit | Line | Data |
---|---|---|
41c67149 JM |
1 | /* Round to nearest integer value, rounding halfway cases to even. |
2 | dbl-64/wordsize-64 version. | |
688903eb | 3 | Copyright (C) 2016-2018 Free Software Foundation, Inc. |
41c67149 JM |
4 | This file is part of the GNU C Library. |
5 | ||
6 | The GNU C Library is free software; you can redistribute it and/or | |
7 | modify it under the terms of the GNU Lesser General Public | |
8 | License as published by the Free Software Foundation; either | |
9 | version 2.1 of the License, or (at your option) any later version. | |
10 | ||
11 | The GNU C Library is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Lesser General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public | |
17 | License along with the GNU C Library; if not, see | |
18 | <http://www.gnu.org/licenses/>. */ | |
19 | ||
20 | #include <math.h> | |
21 | #include <math_private.h> | |
1e2bffd0 | 22 | #include <libm-alias-double.h> |
41c67149 JM |
23 | #include <stdint.h> |
24 | ||
25 | #define BIAS 0x3ff | |
26 | #define MANT_DIG 53 | |
27 | #define MAX_EXP (2 * BIAS + 1) | |
28 | ||
29 | double | |
01f28812 | 30 | __roundeven (double x) |
41c67149 JM |
31 | { |
32 | uint64_t ix, ux; | |
33 | EXTRACT_WORDS64 (ix, x); | |
34 | ux = ix & 0x7fffffffffffffffULL; | |
35 | int exponent = ux >> (MANT_DIG - 1); | |
36 | if (exponent >= BIAS + MANT_DIG - 1) | |
37 | { | |
38 | /* Integer, infinity or NaN. */ | |
39 | if (exponent == MAX_EXP) | |
40 | /* Infinity or NaN; quiet signaling NaNs. */ | |
41 | return x + x; | |
42 | else | |
43 | return x; | |
44 | } | |
45 | else if (exponent >= BIAS) | |
46 | { | |
47 | /* At least 1; not necessarily an integer. Locate the bits with | |
48 | exponents 0 and -1 (when the unbiased exponent is 0, the bit | |
49 | with exponent 0 is implicit, but as the bias is odd it is OK | |
50 | to take it from the low bit of the exponent). */ | |
51 | int int_pos = (BIAS + MANT_DIG - 1) - exponent; | |
52 | int half_pos = int_pos - 1; | |
53 | uint64_t half_bit = 1ULL << half_pos; | |
54 | uint64_t int_bit = 1ULL << int_pos; | |
55 | if ((ix & (int_bit | (half_bit - 1))) != 0) | |
56 | /* Carry into the exponent works correctly. No need to test | |
57 | whether HALF_BIT is set. */ | |
58 | ix += half_bit; | |
59 | ix &= ~(int_bit - 1); | |
60 | } | |
61 | else if (exponent == BIAS - 1 && ux > 0x3fe0000000000000ULL) | |
62 | /* Interval (0.5, 1). */ | |
63 | ix = (ix & 0x8000000000000000ULL) | 0x3ff0000000000000ULL; | |
64 | else | |
65 | /* Rounds to 0. */ | |
66 | ix &= 0x8000000000000000ULL; | |
67 | INSERT_WORDS64 (x, ix); | |
68 | return x; | |
69 | } | |
01f28812 | 70 | hidden_def (__roundeven) |
1e2bffd0 | 71 | libm_alias_double (__roundeven, roundeven) |