1 | /* origin: FreeBSD /usr/src/lib/msun/src/k_expf.c */
|
---|
2 | /*-
|
---|
3 | * Copyright (c) 2011 David Schultz <das@FreeBSD.ORG>
|
---|
4 | * All rights reserved.
|
---|
5 | *
|
---|
6 | * Redistribution and use in source and binary forms, with or without
|
---|
7 | * modification, are permitted provided that the following conditions
|
---|
8 | * are met:
|
---|
9 | * 1. Redistributions of source code must retain the above copyright
|
---|
10 | * notice, this list of conditions and the following disclaimer.
|
---|
11 | * 2. Redistributions in binary form must reproduce the above copyright
|
---|
12 | * notice, this list of conditions and the following disclaimer in the
|
---|
13 | * documentation and/or other materials provided with the distribution.
|
---|
14 | *
|
---|
15 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
---|
16 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
---|
17 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
---|
18 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
---|
19 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
---|
20 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
---|
21 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
---|
22 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
---|
23 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
---|
24 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
---|
25 | * SUCH DAMAGE.
|
---|
26 | */
|
---|
27 |
|
---|
28 | #include "libm.h"
|
---|
29 |
|
---|
30 | static const uint32_t k = 235; /* constant for reduction */
|
---|
31 | static const float kln2 = 162.88958740F; /* k * ln2 */
|
---|
32 |
|
---|
33 | /*
|
---|
34 | * See __cexp.c for details.
|
---|
35 | *
|
---|
36 | * Input: ln(FLT_MAX) <= x < ln(2 * FLT_MAX / FLT_MIN_DENORM) ~= 192.7
|
---|
37 | * Output: 2**127 <= y < 2**128
|
---|
38 | */
|
---|
39 | static float __frexp_expf(float x, int *expt)
|
---|
40 | {
|
---|
41 | float exp_x;
|
---|
42 | uint32_t hx;
|
---|
43 |
|
---|
44 | exp_x = expf(x - kln2);
|
---|
45 | GET_FLOAT_WORD(hx, exp_x);
|
---|
46 | *expt = (hx >> 23) - (0x7f + 127) + k;
|
---|
47 | SET_FLOAT_WORD(exp_x, (hx & 0x7fffff) | ((0x7f + 127) << 23));
|
---|
48 | return exp_x;
|
---|
49 | }
|
---|
50 |
|
---|
51 | float complex __ldexp_cexpf(float complex z, int expt)
|
---|
52 | {
|
---|
53 | float x, y, exp_x, scale1, scale2;
|
---|
54 | int ex_expt, half_expt;
|
---|
55 |
|
---|
56 | x = crealf(z);
|
---|
57 | y = cimagf(z);
|
---|
58 | exp_x = __frexp_expf(x, &ex_expt);
|
---|
59 | expt += ex_expt;
|
---|
60 |
|
---|
61 | half_expt = expt / 2;
|
---|
62 | SET_FLOAT_WORD(scale1, (0x7f + half_expt) << 23);
|
---|
63 | half_expt = expt - half_expt;
|
---|
64 | SET_FLOAT_WORD(scale2, (0x7f + half_expt) << 23);
|
---|
65 |
|
---|
66 | return CMPLXF(cosf(y) * exp_x * scale1 * scale2,
|
---|
67 | sinf(y) * exp_x * scale1 * scale2);
|
---|
68 | }
|
---|