src/complex/__cexpf.c

   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 }