1 /* Round to nearest integer value, rounding halfway cases to even.
2 ldbl-96 version.
3 Copyright (C) 2016-2021 Free Software Foundation, Inc.
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 <https://www.gnu.org/licenses/>. */
19
20 #define NO_MATH_REDIRECT
21 #include <math.h>
22 #include <math_private.h>
23 #include <libm-alias-ldouble.h>
24 #include <stdint.h>
25
26 #define BIAS 0x3fff
27 #define MANT_DIG 64
28 #define MAX_EXP (2 * BIAS + 1)
29
30 long double
__roundevenl(long double x)31 __roundevenl (long double x)
32 {
33 uint16_t se;
34 uint32_t hx, lx;
35 GET_LDOUBLE_WORDS (se, hx, lx, x);
36 int exponent = se & 0x7fff;
37 if (exponent >= BIAS + MANT_DIG - 1)
38 {
39 /* Integer, infinity or NaN. */
40 if (exponent == MAX_EXP)
41 /* Infinity or NaN; quiet signaling NaNs. */
42 return x + x;
43 else
44 return x;
45 }
46 else if (exponent >= BIAS + MANT_DIG - 32)
47 {
48 /* Not necessarily an integer; integer bit is in low word.
49 Locate the bits with exponents 0 and -1. */
50 int int_pos = (BIAS + MANT_DIG - 1) - exponent;
51 int half_pos = int_pos - 1;
52 uint32_t half_bit = 1U << half_pos;
53 uint32_t int_bit = 1U << int_pos;
54 if ((lx & (int_bit | (half_bit - 1))) != 0)
55 {
56 /* No need to test whether HALF_BIT is set. */
57 lx += half_bit;
58 if (lx < half_bit)
59 {
60 hx++;
61 if (hx == 0)
62 {
63 hx = 0x80000000;
64 se++;
65 }
66 }
67 }
68 lx &= ~(int_bit - 1);
69 }
70 else if (exponent == BIAS + MANT_DIG - 33)
71 {
72 /* Not necessarily an integer; integer bit is bottom of high
73 word, half bit is top of low word. */
74 if (((hx & 1) | (lx & 0x7fffffff)) != 0)
75 {
76 lx += 0x80000000;
77 if (lx < 0x80000000)
78 {
79 hx++;
80 if (hx == 0)
81 {
82 hx = 0x80000000;
83 se++;
84 }
85 }
86 }
87 lx = 0;
88 }
89 else if (exponent >= BIAS)
90 {
91 /* At least 1; not necessarily an integer, integer bit and half
92 bit are in the high word. Locate the bits with exponents 0
93 and -1. */
94 int int_pos = (BIAS + MANT_DIG - 33) - exponent;
95 int half_pos = int_pos - 1;
96 uint32_t half_bit = 1U << half_pos;
97 uint32_t int_bit = 1U << int_pos;
98 if (((hx & (int_bit | (half_bit - 1))) | lx) != 0)
99 {
100 hx += half_bit;
101 if (hx < half_bit)
102 {
103 hx = 0x80000000;
104 se++;
105 }
106 }
107 hx &= ~(int_bit - 1);
108 lx = 0;
109 }
110 else if (exponent == BIAS - 1 && (hx > 0x80000000 || lx != 0))
111 {
112 /* Interval (0.5, 1). */
113 se = (se & 0x8000) | 0x3fff;
114 hx = 0x80000000;
115 lx = 0;
116 }
117 else
118 {
119 /* Rounds to 0. */
120 se &= 0x8000;
121 hx = 0;
122 lx = 0;
123 }
124 SET_LDOUBLE_WORDS (x, se, hx, lx);
125 return x;
126 }
127 libm_alias_ldouble (__roundeven, roundeven)
128