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 30static const uint32_t k = 235; /* constant for reduction */ 31static 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 */ 39static 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 51float 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