src/math/atan2l.c

   1 /* origin: FreeBSD /usr/src/lib/msun/src/e_atan2l.c */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunSoft, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  *
  12  */
  13 /*
  14  * See comments in atan2.c.
  15  * Converted to long double by David Schultz <das@FreeBSD.ORG>.
  16  */
  17
  18 #include "libm.h"
  19
  20 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
  21 long double atan2l(long double y, long double x)
  22 {
  23         return atan2(y, x);
  24 }
  25 #elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
  26 #include "__invtrigl.h"
  27
  28 long double atan2l(long double y, long double x)
  29 {
  30         union ldshape ux, uy;
  31         long double z;
  32         int m, ex, ey;
  33
  34         if (isnan(x) || isnan(y))
  35                 return x+y;
  36         if (x == 1)
  37                 return atanl(y);
  38         ux.f = x;
  39         uy.f = y;
  40         ex = ux.i.se & 0x7fff;
  41         ey = uy.i.se & 0x7fff;
  42         m = 2*(ux.i.se>>15) | uy.i.se>>15;
  43         if (y == 0) {
  44                 switch(m) {
  45                 case 0:
  46                 case 1: return y;           /* atan(+-0,+anything)=+-0 */
  47                 case 2: return  2*pio2_hi;  /* atan(+0,-anything) = pi */
  48                 case 3: return -2*pio2_hi;  /* atan(-0,-anything) =-pi */
  49                 }
  50         }
  51         if (x == 0)
  52                 return m&1 ? -pio2_hi : pio2_hi;
  53         if (ex == 0x7fff) {
  54                 if (ey == 0x7fff) {
  55                         switch(m) {
  56                         case 0: return  pio2_hi/2;   /* atan(+INF,+INF) */
  57                         case 1: return -pio2_hi/2;   /* atan(-INF,+INF) */
  58                         case 2: return  1.5*pio2_hi; /* atan(+INF,-INF) */
  59                         case 3: return -1.5*pio2_hi; /* atan(-INF,-INF) */
  60                         }
  61                 } else {
  62                         switch(m) {
  63                         case 0: return  0.0;        /* atan(+...,+INF) */
  64                         case 1: return -0.0;        /* atan(-...,+INF) */
  65                         case 2: return  2*pio2_hi;  /* atan(+...,-INF) */
  66                         case 3: return -2*pio2_hi;  /* atan(-...,-INF) */
  67                         }
  68                 }
  69         }
  70         if (ex+120 < ey || ey == 0x7fff)
  71                 return m&1 ? -pio2_hi : pio2_hi;
  72         /* z = atan(|y/x|) without spurious underflow */
  73         if ((m&2) && ey+120 < ex)  /* |y/x| < 0x1p-120, x<0 */
  74                 z = 0.0;
  75         else
  76                 z = atanl(fabsl(y/x));
  77         switch (m) {
  78         case 0: return z;               /* atan(+,+) */
  79         case 1: return -z;              /* atan(-,+) */
  80         case 2: return 2*pio2_hi-(z-2*pio2_lo); /* atan(+,-) */
  81         default: /* case 3 */
  82                 return (z-2*pio2_lo)-2*pio2_hi; /* atan(-,-) */
  83         }
  84 }
  85 #endif