sysdeps/ieee754/dbl-64/s_setpayload_main.c

   1 /* Set NaN payload.  dbl-64 version.
   2    Copyright (C) 2016-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <math.h>
  20 #include <math_private.h>
  21 #include <libm-alias-double.h>
  22 #include <nan-high-order-bit.h>
  23 #include <stdint.h>
  24
  25 #define SET_HIGH_BIT (HIGH_ORDER_BIT_IS_SET_FOR_SNAN ? SIG : !SIG)
  26 #define BIAS 0x3ff
  27 #define PAYLOAD_DIG 51
  28 #define EXPLICIT_MANT_DIG 52
  29
  30 int
  31 FUNC (double *x, double payload)
  32 {
  33   uint32_t hx, lx;
  34   EXTRACT_WORDS (hx, lx, payload);
  35   int exponent = hx >> (EXPLICIT_MANT_DIG - 32);
  36   /* Test if argument is (a) negative or too large; (b) too small,
  37      except for 0 when allowed; (c) not an integer.  */
  38   if (exponent >= BIAS + PAYLOAD_DIG
  39       || (exponent < BIAS && !(SET_HIGH_BIT && hx == 0 && lx == 0)))
  40     {
  41       INSERT_WORDS (*x, 0, 0);
  42       return 1;
  43     }
  44   int shift = BIAS + EXPLICIT_MANT_DIG - exponent;
  45   if (shift < 32
  46       ? (lx & ((1U << shift) - 1)) != 0
  47       : (lx != 0 || (hx & ((1U << (shift - 32)) - 1)) != 0))
  48     {
  49       INSERT_WORDS (*x, 0, 0);
  50       return 1;
  51     }
  52   if (exponent != 0)
  53     {
  54       hx &= (1U << (EXPLICIT_MANT_DIG - 32)) - 1;
  55       hx |= 1U << (EXPLICIT_MANT_DIG - 32);
  56       if (shift >= 32)
  57         {
  58           lx = hx >> (shift - 32);
  59           hx = 0;
  60         }
  61       else if (shift != 0)
  62         {
  63           lx = (lx >> shift) | (hx << (32 - shift));
  64           hx >>= shift;
  65         }
  66     }
  67   hx |= 0x7ff00000 | (SET_HIGH_BIT ? 0x80000 : 0);
  68   INSERT_WORDS (*x, hx, lx);
  69   return 0;
  70 }