math/multc3.c

   1 /* Copyright (C) 2005, 2006, 2011 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Richard Henderson <rth@redhat.com>, 2005.
   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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <stdbool.h>
  21 #include <math.h>
  22 #include <complex.h>
  23
  24 attribute_hidden
  25 long double _Complex
  26 __multc3 (long double a, long double b, long double c, long double d)
  27 {
  28   long double ac, bd, ad, bc, x, y;
  29
  30   ac = a * c;
  31   bd = b * d;
  32   ad = a * d;
  33   bc = b * c;
  34
  35   x = ac - bd;
  36   y = ad + bc;
  37
  38   if (isnan (x) && isnan (y))
  39     {
  40       /* Recover infinities that computed as NaN + iNaN.  */
  41       bool recalc = 0;
  42       if (__isinf_nsl (a) || __isinf_nsl (b))
  43         {
  44           /* z is infinite.  "Box" the infinity and change NaNs in
  45              the other factor to 0.  */
  46           a = __copysignl (__isinf_nsl (a) ? 1 : 0, a);
  47           b = __copysignl (__isinf_nsl (b) ? 1 : 0, b);
  48           if (isnan (c)) c = __copysignl (0, c);
  49           if (isnan (d)) d = __copysignl (0, d);
  50           recalc = 1;
  51         }
  52      if (__isinf_nsl (c) || __isinf_nsl (d))
  53         {
  54           /* w is infinite.  "Box" the infinity and change NaNs in
  55              the other factor to 0.  */
  56           c = __copysignl (__isinf_nsl (c) ? 1 : 0, c);
  57           d = __copysignl (__isinf_nsl (d) ? 1 : 0, d);
  58           if (isnan (a)) a = __copysignl (0, a);
  59           if (isnan (b)) b = __copysignl (0, b);
  60           recalc = 1;
  61         }
  62      if (!recalc
  63           && (__isinf_nsl (ac) || __isinf_nsl (bd)
  64               || __isinf_nsl (ad) || __isinf_nsl (bc)))
  65         {
  66           /* Recover infinities from overflow by changing NaNs to 0.  */
  67           if (isnan (a)) a = __copysignl (0, a);
  68           if (isnan (b)) b = __copysignl (0, b);
  69           if (isnan (c)) c = __copysignl (0, c);
  70           if (isnan (d)) d = __copysignl (0, d);
  71           recalc = 1;
  72         }
  73       if (recalc)
  74         {
  75           x = INFINITY * (a * c - b * d);
  76           y = INFINITY * (a * d + b * c);
  77         }
  78     }
  79
  80   return x + I * y;
  81 }