1/* Round to nearest integer value, rounding halfway cases to even.
2 ldbl-128 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 <math-use-builtins.h>
25#include <stdint.h>
26
27#define BIAS 0x3fff
28#define MANT_DIG 113
29#define MAX_EXP (2 * BIAS + 1)
30
31_Float128
32__roundevenl (_Float128 x)
33{
34#if USE_ROUNDEVENL_BUILTIN
35 return __builtin_roundevenl (x);
36#else
37 uint64_t hx, lx, uhx;
38 GET_LDOUBLE_WORDS64 (hx, lx, x);
39 uhx = hx & 0x7fffffffffffffffULL;
40 int exponent = uhx >> (MANT_DIG - 1 - 64);
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 + MANT_DIG - 64)
51 {
52 /* Not necessarily an integer; integer bit is in low word.
53 Locate the bits with exponents 0 and -1. */
54 int int_pos = (BIAS + MANT_DIG - 1) - exponent;
55 int half_pos = int_pos - 1;
56 uint64_t half_bit = 1ULL << half_pos;
57 uint64_t int_bit = 1ULL << int_pos;
58 if ((lx & (int_bit | (half_bit - 1))) != 0)
59 {
60 /* Carry into the exponent works correctly. No need to test
61 whether HALF_BIT is set. */
62 lx += half_bit;
63 hx += lx < half_bit;
64 }
65 lx &= ~(int_bit - 1);
66 }
67 else if (exponent == BIAS + MANT_DIG - 65)
68 {
69 /* Not necessarily an integer; integer bit is bottom of high
70 word, half bit is top of low word. */
71 if (((hx & 1) | (lx & 0x7fffffffffffffffULL)) != 0)
72 {
73 lx += 0x8000000000000000ULL;
74 hx += lx < 0x8000000000000000ULL;
75 }
76 lx = 0;
77 }
78 else if (exponent >= BIAS)
79 {
80 /* At least 1; not necessarily an integer, integer bit and half
81 bit are in the high word. Locate the bits with exponents 0
82 and -1 (when the unbiased exponent is 0, the bit with
83 exponent 0 is implicit, but as the bias is odd it is OK to
84 take it from the low bit of the exponent). */
85 int int_pos = (BIAS + MANT_DIG - 65) - exponent;
86 int half_pos = int_pos - 1;
87 uint64_t half_bit = 1ULL << half_pos;
88 uint64_t int_bit = 1ULL << int_pos;
89 if (((hx & (int_bit | (half_bit - 1))) | lx) != 0)
90 hx += half_bit;
91 hx &= ~(int_bit - 1);
92 lx = 0;
93 }
94 else if (exponent == BIAS - 1 && (uhx > 0x3ffe000000000000ULL || lx != 0))
95 {
96 /* Interval (0.5, 1). */
97 hx = (hx & 0x8000000000000000ULL) | 0x3fff000000000000ULL;
98 lx = 0;
99 }
100 else
101 {
102 /* Rounds to 0. */
103 hx &= 0x8000000000000000ULL;
104 lx = 0;
105 }
106 SET_LDOUBLE_WORDS64 (x, hx, lx);
107 return x;
108#endif /* ! USE_ROUNDEVENL_BUILTIN */
109}
110libm_alias_ldouble (__roundeven, roundeven)
111