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 "complex_impl.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 }
69