sysdeps/m68k/fpu/atan2.c

   1 /* Copyright (C) 1991, 1992, 1994 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <math.h>
  21
  22 #ifdef  __GNUC__
  23
  24 __CONSTVALUE double
  25 DEFUN(atan2, (y, x), double y AND double x)
  26 {
  27   static CONST double one = 1.0, zero = 0.0;
  28   double signx, signy;
  29   double pi, PIo4, PIo2;
  30
  31   if (__isnan(x))
  32     return x;
  33   if (__isnan(y))
  34     return y;
  35
  36   signy = __copysign(one, y);
  37   signx = __copysign(one, x);
  38
  39   asm("fmovecr%.x %1, %0" : "=f" (pi) : "i" (0));
  40   PIo2 = pi / 2;
  41   PIo4 = pi / 4;
  42
  43   if (y == zero)
  44     return signx == one ? y : __copysign(pi, signy);
  45
  46   if (x == zero)
  47     return __copysign(PIo2, signy);
  48
  49   if (__isinf(x))
  50     {
  51       if (__isinf(y))
  52         return __copysign(signx == one ? PIo4 : 3 * PIo4, signy);
  53       else
  54         return __copysign(signx == one ? zero : pi, signy);
  55     }
  56
  57   if (__isinf(y))
  58     return __copysign(PIo2, signy);
  59
  60   y = fabs(y);
  61
  62   if (x < 0.0)
  63     /* X is negative.  */
  64     return __copysign(pi - atan(y / -x), signy);
  65
  66   return __copysign(atan(y / x), signy);
  67 }
  68
  69 #else
  70 #include <sysdeps/generic/atan2.c>
  71 #endif