1 /* Round to nearest integer value, rounding halfway cases to even.
2 Copyright (C) 2016-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
19 #define NO_MATH_REDIRECT
21 #include <math_private.h>
22 #include <libm-alias-double.h>
24 #include <math-use-builtins.h>
28 #define MAX_EXP (2 * BIAS + 1)
31 __roundeven (double x
)
33 #if USE_ROUNDEVEN_BUILTIN
34 return __builtin_roundeven (x
);
37 EXTRACT_WORDS64 (ix
, x
);
38 ux
= ix
& 0x7fffffffffffffffULL
;
39 int exponent
= ux
>> (MANT_DIG
- 1);
40 if (exponent
>= BIAS
+ MANT_DIG
- 1)
42 /* Integer, infinity or NaN. */
43 if (exponent
== MAX_EXP
)
44 /* Infinity or NaN; quiet signaling NaNs. */
49 else if (exponent
>= BIAS
)
51 /* At least 1; not necessarily an integer. Locate the bits with
52 exponents 0 and -1 (when the unbiased exponent is 0, the bit
53 with exponent 0 is implicit, but as the bias is odd it is OK
54 to take it from the low bit of the exponent). */
55 int int_pos
= (BIAS
+ MANT_DIG
- 1) - exponent
;
56 int half_pos
= int_pos
- 1;
57 uint64_t half_bit
= 1ULL << half_pos
;
58 uint64_t int_bit
= 1ULL << int_pos
;
59 if ((ix
& (int_bit
| (half_bit
- 1))) != 0)
60 /* Carry into the exponent works correctly. No need to test
61 whether HALF_BIT is set. */
65 else if (exponent
== BIAS
- 1 && ux
> 0x3fe0000000000000ULL
)
66 /* Interval (0.5, 1). */
67 ix
= (ix
& 0x8000000000000000ULL
) | 0x3ff0000000000000ULL
;
70 ix
&= 0x8000000000000000ULL
;
71 INSERT_WORDS64 (x
, ix
);
73 #endif /* ! USE_ROUNDEVEN_BUILTIN */
76 libm_alias_double (__roundeven
, roundeven
)