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41c67149 JM |
1 | /* Round to nearest integer value, rounding halfway cases to even. |
2 | flt-32 version. | |
6d7e8eda | 3 | Copyright (C) 2016-2023 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 | |
5a82c748 | 18 | <https://www.gnu.org/licenses/>. */ |
41c67149 | 19 | |
447954a2 | 20 | #define NO_MATH_REDIRECT |
41c67149 JM |
21 | #include <math.h> |
22 | #include <math_private.h> | |
2f49ce7d | 23 | #include <libm-alias-float.h> |
eb906620 | 24 | #include <math-use-builtins.h> |
41c67149 JM |
25 | #include <stdint.h> |
26 | ||
27 | #define BIAS 0x7f | |
28 | #define MANT_DIG 24 | |
29 | #define MAX_EXP (2 * BIAS + 1) | |
30 | ||
31 | float | |
01f28812 | 32 | __roundevenf (float x) |
41c67149 | 33 | { |
eb906620 STH |
34 | #if USE_ROUNDEVENF_BUILTIN |
35 | return __builtin_roundevenf (x); | |
36 | #else | |
41c67149 JM |
37 | uint32_t ix, ux; |
38 | GET_FLOAT_WORD (ix, x); | |
39 | ux = ix & 0x7fffffff; | |
40 | int exponent = ux >> (MANT_DIG - 1); | |
41 | if (exponent >= BIAS + MANT_DIG - 1) | |
42 | { | |
43 | /* Integer, infinity or NaN. */ | |
44 | if (exponent == MAX_EXP) | |
45 | /* Infinity or NaN; quiet signaling NaNs. */ | |
46 | return x + x; | |
47 | else | |
48 | return x; | |
49 | } | |
50 | else if (exponent >= BIAS) | |
51 | { | |
52 | /* At least 1; not necessarily an integer. Locate the bits with | |
53 | exponents 0 and -1 (when the unbiased exponent is 0, the bit | |
54 | with exponent 0 is implicit, but as the bias is odd it is OK | |
55 | to take it from the low bit of the exponent). */ | |
56 | int int_pos = (BIAS + MANT_DIG - 1) - exponent; | |
57 | int half_pos = int_pos - 1; | |
58 | uint32_t half_bit = 1U << half_pos; | |
59 | uint32_t int_bit = 1U << int_pos; | |
60 | if ((ix & (int_bit | (half_bit - 1))) != 0) | |
61 | /* Carry into the exponent works correctly. No need to test | |
62 | whether HALF_BIT is set. */ | |
63 | ix += half_bit; | |
64 | ix &= ~(int_bit - 1); | |
65 | } | |
66 | else if (exponent == BIAS - 1 && ux > 0x3f000000) | |
67 | /* Interval (0.5, 1). */ | |
68 | ix = (ix & 0x80000000) | 0x3f800000; | |
69 | else | |
70 | /* Rounds to 0. */ | |
71 | ix &= 0x80000000; | |
72 | SET_FLOAT_WORD (x, ix); | |
73 | return x; | |
eb906620 | 74 | #endif /* ! USE_ROUNDEVENF_BUILTIN */ |
41c67149 | 75 | } |
447954a2 | 76 | #ifndef __roundevenf |
2f49ce7d | 77 | libm_alias_float (__roundeven, roundeven) |
447954a2 | 78 | #endif |