1 /* e_atan2f.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 #include "math.h" 17 #include "math_private.h" 18 19 static volatile float 20 tiny = 1.0e-30; 21 static const float 22 zero = 0.0, 23 pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */ 24 pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */ 25 pi = 3.1415927410e+00; /* 0x40490fdb */ 26 static volatile float 27 pi_lo = -8.7422776573e-08; /* 0xb3bbbd2e */ 28 29 float 30 atan2f(float y, float x) 31 { 32 float z; 33 int32_t k,m,hx,hy,ix,iy; 34 35 GET_FLOAT_WORD(hx,x); 36 ix = hx&0x7fffffff; 37 GET_FLOAT_WORD(hy,y); 38 iy = hy&0x7fffffff; 39 if((ix>0x7f800000)|| 40 (iy>0x7f800000)) /* x or y is NaN */ 41 return nan_mix(x, y); 42 if(hx==0x3f800000) return atanf(y); /* x=1.0 */ 43 m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */ 44 45 /* when y = 0 */ 46 if(iy==0) { 47 switch(m) { 48 case 0: 49 case 1: return y; /* atan(+-0,+anything)=+-0 */ 50 case 2: return pi+tiny;/* atan(+0,-anything) = pi */ 51 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */ 52 } 53 } 54 /* when x = 0 */ 55 if(ix==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 56 57 /* when x is INF */ 58 if(ix==0x7f800000) { 59 if(iy==0x7f800000) { 60 switch(m) { 61 case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */ 62 case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */ 63 case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/ 64 case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/ 65 } 66 } else { 67 switch(m) { 68 case 0: return zero ; /* atan(+...,+INF) */ 69 case 1: return -zero ; /* atan(-...,+INF) */ 70 case 2: return pi+tiny ; /* atan(+...,-INF) */ 71 case 3: return -pi-tiny ; /* atan(-...,-INF) */ 72 } 73 } 74 } 75 /* when y is INF */ 76 if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 77 78 /* compute y/x */ 79 k = (iy-ix)>>23; 80 if(k > 26) { /* |y/x| > 2**26 */ 81 z=pi_o_2+(float)0.5*pi_lo; 82 m&=1; 83 } 84 else if(k<-26&&hx<0) z=0.0; /* 0 > |y|/x > -2**-26 */ 85 else z=atanf(fabsf(y/x)); /* safe to do y/x */ 86 switch (m) { 87 case 0: return z ; /* atan(+,+) */ 88 case 1: return -z ; /* atan(-,+) */ 89 case 2: return pi-(z-pi_lo);/* atan(+,-) */ 90 default: /* case 3 */ 91 return (z-pi_lo)-pi;/* atan(-,-) */ 92 } 93 } 94