1/* Copyright (C) 2011-2020 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
4
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.
9
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.
14
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/>. */
18
19#include <inttypes.h>
20#include <math.h>
21#include <math_private.h>
22#include <libm-alias-double.h>
23
24/*
25 * for non-zero, finite x
26 * x = frexp(arg,&exp);
27 * return a double fp quantity x such that 0.5 <= |x| <1.0
28 * and the corresponding binary exponent "exp". That is
29 * arg = x*2^exp.
30 * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
31 * with *exp=0.
32 */
33
34
35double
36__frexp (double x, int *eptr)
37{
38 int64_t ix;
39 EXTRACT_WORDS64 (ix, x);
40 int32_t ex = 0x7ff & (ix >> 52);
41 int e = 0;
42
43 if (__glibc_likely (ex != 0x7ff && x != 0.0))
44 {
45 /* Not zero and finite. */
46 e = ex - 1022;
47 if (__glibc_unlikely (ex == 0))
48 {
49 /* Subnormal. */
50 x *= 0x1p54;
51 EXTRACT_WORDS64 (ix, x);
52 ex = 0x7ff & (ix >> 52);
53 e = ex - 1022 - 54;
54 }
55
56 ix = (ix & INT64_C (0x800fffffffffffff)) | INT64_C (0x3fe0000000000000);
57 INSERT_WORDS64 (x, ix);
58 }
59 else
60 /* Quiet signaling NaNs. */
61 x += x;
62
63 *eptr = e;
64 return x;
65}
66libm_alias_double (__frexp, frexp)
67