[352] | 1 | /* origin: FreeBSD /usr/src/lib/msun/src/k_expf.c */
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| 2 | /*-
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| 3 | * Copyright (c) 2011 David Schultz <das@FreeBSD.ORG>
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| 4 | * All rights reserved.
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| 5 | *
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| 6 | * Redistribution and use in source and binary forms, with or without
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| 7 | * modification, are permitted provided that the following conditions
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| 8 | * are met:
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| 9 | * 1. Redistributions of source code must retain the above copyright
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| 10 | * notice, this list of conditions and the following disclaimer.
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| 11 | * 2. Redistributions in binary form must reproduce the above copyright
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| 12 | * notice, this list of conditions and the following disclaimer in the
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| 13 | * documentation and/or other materials provided with the distribution.
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| 14 | *
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| 15 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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| 16 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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| 17 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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| 18 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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| 19 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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| 20 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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| 21 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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| 22 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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| 23 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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| 24 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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| 25 | * SUCH DAMAGE.
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| 26 | */
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| 27 |
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| 28 | #include "libm.h"
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| 29 |
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| 30 | static const uint32_t k = 235; /* constant for reduction */
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| 31 | static const float kln2 = 162.88958740F; /* k * ln2 */
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| 32 |
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| 33 | /*
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| 34 | * See __cexp.c for details.
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| 35 | *
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| 36 | * Input: ln(FLT_MAX) <= x < ln(2 * FLT_MAX / FLT_MIN_DENORM) ~= 192.7
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| 37 | * Output: 2**127 <= y < 2**128
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| 38 | */
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| 39 | static float __frexp_expf(float x, int *expt)
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| 40 | {
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| 41 | float exp_x;
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| 42 | uint32_t hx;
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| 43 |
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| 44 | exp_x = expf(x - kln2);
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| 45 | GET_FLOAT_WORD(hx, exp_x);
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| 46 | *expt = (hx >> 23) - (0x7f + 127) + k;
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| 47 | SET_FLOAT_WORD(exp_x, (hx & 0x7fffff) | ((0x7f + 127) << 23));
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| 48 | return exp_x;
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| 49 | }
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| 50 |
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| 51 | float complex __ldexp_cexpf(float complex z, int expt)
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| 52 | {
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| 53 | float x, y, exp_x, scale1, scale2;
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| 54 | int ex_expt, half_expt;
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| 55 |
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| 56 | x = crealf(z);
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| 57 | y = cimagf(z);
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| 58 | exp_x = __frexp_expf(x, &ex_expt);
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| 59 | expt += ex_expt;
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| 60 |
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| 61 | half_expt = expt / 2;
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| 62 | SET_FLOAT_WORD(scale1, (0x7f + half_expt) << 23);
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| 63 | half_expt = expt - half_expt;
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| 64 | SET_FLOAT_WORD(scale2, (0x7f + half_expt) << 23);
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| 65 |
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| 66 | return CMPLXF(cosf(y) * exp_x * scale1 * scale2,
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| 67 | sinf(y) * exp_x * scale1 * scale2);
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| 68 | }
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