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41c67149 JM |
1 | /* Round to nearest integer value, rounding halfway cases to even. |
2 | ldbl-96 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> | |
86f9568a | 22 | #include <libm-alias-ldouble.h> |
41c67149 JM |
23 | #include <stdint.h> |
24 | ||
25 | #define BIAS 0x3fff | |
26 | #define MANT_DIG 64 | |
27 | #define MAX_EXP (2 * BIAS + 1) | |
28 | ||
29 | long double | |
01f28812 | 30 | __roundevenl (long double x) |
41c67149 JM |
31 | { |
32 | uint16_t se; | |
33 | uint32_t hx, lx; | |
34 | GET_LDOUBLE_WORDS (se, hx, lx, x); | |
35 | int exponent = se & 0x7fff; | |
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 + MANT_DIG - 32) | |
46 | { | |
47 | /* Not necessarily an integer; integer bit is in low word. | |
48 | Locate the bits with exponents 0 and -1. */ | |
49 | int int_pos = (BIAS + MANT_DIG - 1) - exponent; | |
50 | int half_pos = int_pos - 1; | |
51 | uint32_t half_bit = 1U << half_pos; | |
52 | uint32_t int_bit = 1U << int_pos; | |
53 | if ((lx & (int_bit | (half_bit - 1))) != 0) | |
54 | { | |
55 | /* No need to test whether HALF_BIT is set. */ | |
56 | lx += half_bit; | |
57 | if (lx < half_bit) | |
58 | { | |
59 | hx++; | |
60 | if (hx == 0) | |
61 | { | |
62 | hx = 0x80000000; | |
63 | se++; | |
64 | } | |
65 | } | |
66 | } | |
67 | lx &= ~(int_bit - 1); | |
68 | } | |
69 | else if (exponent == BIAS + MANT_DIG - 33) | |
70 | { | |
71 | /* Not necessarily an integer; integer bit is bottom of high | |
72 | word, half bit is top of low word. */ | |
73 | if (((hx & 1) | (lx & 0x7fffffff)) != 0) | |
74 | { | |
75 | lx += 0x80000000; | |
76 | if (lx < 0x80000000) | |
77 | { | |
78 | hx++; | |
79 | if (hx == 0) | |
80 | { | |
81 | hx = 0x80000000; | |
82 | se++; | |
83 | } | |
84 | } | |
85 | } | |
86 | lx = 0; | |
87 | } | |
88 | else if (exponent >= BIAS) | |
89 | { | |
90 | /* At least 1; not necessarily an integer, integer bit and half | |
91 | bit are in the high word. Locate the bits with exponents 0 | |
92 | and -1. */ | |
93 | int int_pos = (BIAS + MANT_DIG - 33) - exponent; | |
94 | int half_pos = int_pos - 1; | |
95 | uint32_t half_bit = 1U << half_pos; | |
96 | uint32_t int_bit = 1U << int_pos; | |
97 | if (((hx & (int_bit | (half_bit - 1))) | lx) != 0) | |
98 | { | |
99 | hx += half_bit; | |
100 | if (hx < half_bit) | |
101 | { | |
102 | hx = 0x80000000; | |
103 | se++; | |
104 | } | |
105 | } | |
106 | hx &= ~(int_bit - 1); | |
107 | lx = 0; | |
108 | } | |
109 | else if (exponent == BIAS - 1 && (hx > 0x80000000 || lx != 0)) | |
110 | { | |
111 | /* Interval (0.5, 1). */ | |
112 | se = (se & 0x8000) | 0x3fff; | |
113 | hx = 0x80000000; | |
114 | lx = 0; | |
115 | } | |
116 | else | |
117 | { | |
118 | /* Rounds to 0. */ | |
119 | se &= 0x8000; | |
120 | hx = 0; | |
121 | lx = 0; | |
122 | } | |
123 | SET_LDOUBLE_WORDS (x, se, hx, lx); | |
124 | return x; | |
125 | } | |
86f9568a | 126 | libm_alias_ldouble (__roundeven, roundeven) |