1 | /* ef_atan2.c -- float version of e_atan2.c. |
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2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
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3 | */ |
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4 | |
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5 | /* |
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6 | * ==================================================== |
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7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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8 | * |
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9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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10 | * Permission to use, copy, modify, and distribute this |
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11 | * software is freely granted, provided that this notice |
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12 | * is preserved. |
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13 | * ==================================================== |
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14 | * |
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15 | */ |
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16 | |
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17 | #include "fdlibm.h" |
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18 | |
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19 | #ifdef __STDC__ |
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20 | static const float |
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21 | #else |
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22 | static float |
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23 | #endif |
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24 | tiny = 1.0e-30, |
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25 | zero = 0.0, |
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26 | pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */ |
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27 | pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */ |
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28 | pi = 3.1415927410e+00, /* 0x40490fdb */ |
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29 | pi_lo = -8.7422776573e-08; /* 0xb3bbbd2e */ |
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30 | |
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31 | #ifdef __STDC__ |
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32 | float __ieee754_atan2f(float y, float x) |
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33 | #else |
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34 | float __ieee754_atan2f(y,x) |
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35 | float y,x; |
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36 | #endif |
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37 | { |
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38 | float z; |
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39 | __int32_t k,m,hx,hy,ix,iy; |
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40 | |
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41 | GET_FLOAT_WORD(hx,x); |
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42 | ix = hx&0x7fffffff; |
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43 | GET_FLOAT_WORD(hy,y); |
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44 | iy = hy&0x7fffffff; |
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45 | if(FLT_UWORD_IS_NAN(ix)|| |
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46 | FLT_UWORD_IS_NAN(iy)) /* x or y is NaN */ |
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47 | return x+y; |
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48 | if(hx==0x3f800000) return atanf(y); /* x=1.0 */ |
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49 | m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */ |
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50 | |
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51 | /* when y = 0 */ |
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52 | if(FLT_UWORD_IS_ZERO(iy)) { |
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53 | switch(m) { |
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54 | case 0: |
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55 | case 1: return y; /* atan(+-0,+anything)=+-0 */ |
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56 | case 2: return pi+tiny;/* atan(+0,-anything) = pi */ |
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57 | case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */ |
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58 | } |
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59 | } |
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60 | /* when x = 0 */ |
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61 | if(FLT_UWORD_IS_ZERO(ix)) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; |
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62 | |
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63 | /* when x is INF */ |
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64 | if(FLT_UWORD_IS_INFINITE(ix)) { |
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65 | if(FLT_UWORD_IS_INFINITE(iy)) { |
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66 | switch(m) { |
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67 | case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */ |
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68 | case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */ |
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69 | case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/ |
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70 | case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/ |
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71 | } |
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72 | } else { |
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73 | switch(m) { |
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74 | case 0: return zero ; /* atan(+...,+INF) */ |
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75 | case 1: return -zero ; /* atan(-...,+INF) */ |
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76 | case 2: return pi+tiny ; /* atan(+...,-INF) */ |
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77 | case 3: return -pi-tiny ; /* atan(-...,-INF) */ |
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78 | } |
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79 | } |
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80 | } |
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81 | /* when y is INF */ |
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82 | if(FLT_UWORD_IS_INFINITE(iy)) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; |
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83 | |
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84 | /* compute y/x */ |
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85 | k = (iy-ix)>>23; |
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86 | if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */ |
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87 | else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */ |
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88 | else z=atanf(fabsf(y/x)); /* safe to do y/x */ |
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89 | switch (m) { |
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90 | case 0: return z ; /* atan(+,+) */ |
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91 | case 1: { |
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92 | __uint32_t zh; |
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93 | GET_FLOAT_WORD(zh,z); |
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94 | SET_FLOAT_WORD(z,zh ^ 0x80000000); |
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95 | } |
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96 | return z ; /* atan(-,+) */ |
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97 | case 2: return pi-(z-pi_lo);/* atan(+,-) */ |
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98 | default: /* case 3 */ |
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99 | return (z-pi_lo)-pi;/* atan(-,-) */ |
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100 | } |
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101 | } |
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