k_expf.c revision 284810 
1/*-
2 * Copyright (c) 2011 David Schultz <das@FreeBSD.ORG>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: stable/10/lib/msun/src/k_expf.c 284810 2015-06-25 13:01:10Z tijl $");
29
30#include <complex.h>
31
32#include "math.h"
33#include "math_private.h"
34
35static const uint32_t k = 235;			/* constant for reduction */
36static const float kln2 =  162.88958740F;	/* k * ln2 */
37
38/*
39 * See k_exp.c for details.
40 *
41 * Input:  ln(FLT_MAX) <= x < ln(2 * FLT_MAX / FLT_MIN_DENORM) ~= 192.7
42 * Output: 2**127 <= y < 2**128
43 */
44static float
45__frexp_expf(float x, int *expt)
46{
47	float exp_x;
48	uint32_t hx;
49
50	exp_x = expf(x - kln2);
51	GET_FLOAT_WORD(hx, exp_x);
52	*expt = (hx >> 23) - (0x7f + 127) + k;
53	SET_FLOAT_WORD(exp_x, (hx & 0x7fffff) | ((0x7f + 127) << 23));
54	return (exp_x);
55}
56
57float
58__ldexp_expf(float x, int expt)
59{
60	float exp_x, scale;
61	int ex_expt;
62
63	exp_x = __frexp_expf(x, &ex_expt);
64	expt += ex_expt;
65	SET_FLOAT_WORD(scale, (0x7f + expt) << 23);
66	return (exp_x * scale);
67}
68
69float complex
70__ldexp_cexpf(float complex z, int expt)
71{
72	float x, y, exp_x, scale1, scale2;
73	int ex_expt, half_expt;
74
75	x = crealf(z);
76	y = cimagf(z);
77	exp_x = __frexp_expf(x, &ex_expt);
78	expt += ex_expt;
79
80	half_expt = expt / 2;
81	SET_FLOAT_WORD(scale1, (0x7f + half_expt) << 23);
82	half_expt = expt - half_expt;
83	SET_FLOAT_WORD(scale2, (0x7f + half_expt) << 23);
84
85	return (CMPLXF(cosf(y) * exp_x * scale1 * scale2,
86	    sinf(y) * exp_x * scale1 * scale2));
87}
88