toolchain/gcc/newlib/libm/math/ef_atan2.c

   1 /* ef_atan2.c -- float version of e_atan2.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  *
  15  */
  16
  17 #include "fdlibm.h"
  18
  19 #ifdef __STDC__
  20 static const float
  21 #else
  22 static float
  23 #endif
  24 tiny  = 1.0e-30,
  25 zero  = 0.0,
  26 pi_o_4  = 7.8539818525e-01, /* 0x3f490fdb */
  27 pi_o_2  = 1.5707963705e+00, /* 0x3fc90fdb */
  28 pi      = 3.1415925026e+00, /* 0x40490fda */
  29 pi_lo   = 1.5099578832e-07; /* 0x34222168 */
  30
  31 #ifdef __STDC__
  32         float __ieee754_atan2f(float y, float x)
  33 #else
  34         float __ieee754_atan2f(y,x)
  35         float  y,x;
  36 #endif
  37 {
  38         float z;
  39         __int32_t k,m,hx,hy,ix,iy;
  40
  41         GET_FLOAT_WORD(hx,x);
  42         ix = hx&0x7fffffff;
  43         GET_FLOAT_WORD(hy,y);
  44         iy = hy&0x7fffffff;
  45         if(FLT_UWORD_IS_NAN(ix)||
  46            FLT_UWORD_IS_NAN(iy))        /* x or y is NaN */
  47            return x+y;
  48         if(hx==0x3f800000) return atanf(y);   /* x=1.0 */
  49         m = ((hy>>31)&1)|((hx>>30)&2);  /* 2*sign(x)+sign(y) */
  50
  51     /* when y = 0 */
  52         if(FLT_UWORD_IS_ZERO(iy)) {
  53             switch(m) {
  54                 case 0:
  55                 case 1: return y;       /* atan(+-0,+anything)=+-0 */
  56                 case 2: return  pi+tiny;/* atan(+0,-anything) = pi */
  57                 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
  58             }
  59         }
  60     /* when x = 0 */
  61         if(FLT_UWORD_IS_ZERO(ix)) return (hy<0)?  -pi_o_2-tiny: pi_o_2+tiny;
  62
  63     /* when x is INF */
  64         if(FLT_UWORD_IS_INFINITE(ix)) {
  65             if(FLT_UWORD_IS_INFINITE(iy)) {
  66                 switch(m) {
  67                     case 0: return  pi_o_4+tiny;/* atan(+INF,+INF) */
  68                     case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
  69                     case 2: return  (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
  70                     case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
  71                 }
  72             } else {
  73                 switch(m) {
  74                     case 0: return  zero  ;     /* atan(+...,+INF) */
  75                     case 1: return -zero  ;     /* atan(-...,+INF) */
  76                     case 2: return  pi+tiny  ;  /* atan(+...,-INF) */
  77                     case 3: return -pi-tiny  ;  /* atan(-...,-INF) */
  78                 }
  79             }
  80         }
  81     /* when y is INF */
  82         if(FLT_UWORD_IS_INFINITE(iy)) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
  83
  84     /* compute y/x */
  85         k = (iy-ix)>>23;
  86         if(k > 60) z=pi_o_2+(float)0.5*pi_lo;   /* |y/x| >  2**60 */
  87         else if(hx<0&&k<-60) z=0.0;     /* |y|/x < -2**60 */
  88         else z=atanf(fabsf(y/x));       /* safe to do y/x */
  89         switch (m) {
  90             case 0: return       z  ;   /* atan(+,+) */
  91             case 1: {
  92                       __uint32_t zh;
  93                       GET_FLOAT_WORD(zh,z);
  94                       SET_FLOAT_WORD(z,zh ^ 0x80000000);
  95                     }
  96                     return       z  ;   /* atan(-,+) */
  97             case 2: return  pi-(z-pi_lo);/* atan(+,-) */
  98             default: /* case 3 */
  99                     return  (z-pi_lo)-pi;/* atan(-,-) */
 100         }
 101 }