| 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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