newlib/libm/ld/s_scalbnl.c

   1 /*
   2  * Copyright (c) 2005-2020 Rich Felker, et al.
   3  *
   4  * SPDX-License-Identifier: MIT
   5  *
   6  * Please see https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
   7  * for all contributors to musl.
   8  */
   9 #include <math.h>
  10 #include <float.h>
  11 #include "math_private.h"
  12 #include "fpmath.h"
  13 /*
  14  * scalbnl (long double x, int n)
  15  * scalbnl(x,n) returns x* 2**n  computed by  exponent
  16  * manipulation rather than by actually performing an
  17  * exponentiation or a multiplication.
  18  */
  19 #if (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
  20 long double scalbnl(long double x, int n)
  21 {
  22         union IEEEl2bits u;
  23
  24         if (n > 16383) {
  25                 x *= 0x1p16383L;
  26                 n -= 16383;
  27                 if (n > 16383) {
  28                         x *= 0x1p16383L;
  29                         n -= 16383;
  30                         if (n > 16383)
  31                                 n = 16383;
  32                 }
  33         } else if (n < -16382) {
  34                 x *= 0x1p-16382L * 0x1p113L;
  35                 n += 16382 - 113;
  36                 if (n < -16382) {
  37                         x *= 0x1p-16382L * 0x1p113L;
  38                         n += 16382 - 113;
  39                         if (n < -16382)
  40                                 n = -16382;
  41                 }
  42         }
  43         u.e = 1.0;
  44         u.xbits.expsign = 0x3fff + n;
  45         return x * u.e;
  46 }
  47 __strong_reference(scalbnl, ldexpl);
  48 #endif