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 const float 20 tiny = 1.0e-30, 21 zero = 0.0, 22 pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */ 23 pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */ 24 pi = 3.1415925026e+00, /* 0x40490fda */ 25 pi_lo = 1.5099578832e-07; /* 0x34222168 */ 26 27 float 28 atan2f(float y, float x) 29 { 30 float z; 31 int32_t k,m,hx,hy,ix,iy; 32 33 GET_FLOAT_WORD(hx,x); 34 ix = hx&0x7fffffff; 35 GET_FLOAT_WORD(hy,y); 36 iy = hy&0x7fffffff; 37 if((ix>0x7f800000)|| 38 (iy>0x7f800000)) /* x or y is NaN */ 39 return x+y; 40 if(hx==0x3f800000) return atanf(y); /* x=1.0 */ 41 m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */ 42 43 /* when y = 0 */ 44 if(iy==0) { 45 switch(m) { 46 case 0: 47 case 1: return y; /* atan(+-0,+anything)=+-0 */ 48 case 2: return pi+tiny;/* atan(+0,-anything) = pi */ 49 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */ 50 } 51 } 52 /* when x = 0 */ 53 if(ix==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 54 55 /* when x is INF */ 56 if(ix==0x7f800000) { 57 if(iy==0x7f800000) { 58 switch(m) { 59 case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */ 60 case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */ 61 case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/ 62 case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/ 63 } 64 } else { 65 switch(m) { 66 case 0: return zero ; /* atan(+...,+INF) */ 67 case 1: return -zero ; /* atan(-...,+INF) */ 68 case 2: return pi+tiny ; /* atan(+...,-INF) */ 69 case 3: return -pi-tiny ; /* atan(-...,-INF) */ 70 } 71 } 72 } 73 /* when y is INF */ 74 if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 75 76 /* compute y/x */ 77 k = (iy-ix)>>23; 78 if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */ 79 else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */ 80 else z=atanf(fabsf(y/x)); /* safe to do y/x */ 81 switch (m) { 82 case 0: return z ; /* atan(+,+) */ 83 case 1: { 84 u_int32_t zh; 85 GET_FLOAT_WORD(zh,z); 86 SET_FLOAT_WORD(z,zh ^ 0x80000000); 87 } 88 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