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 <sys/cdefs.h> 17 #if defined(LIBM_SCCS) && !defined(lint) 18 __RCSID("$NetBSD: e_atan2f.c,v 1.7 2002/05/26 22:01:49 wiz Exp $"); 19 #endif 20 21 #include "math.h" 22 #include "math_private.h" 23 24 static const float 25 tiny = 1.0e-30, 26 zero = 0.0, 27 pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */ 28 pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */ 29 pi = 3.1415925026e+00, /* 0x40490fda */ 30 pi_lo = 1.5099578832e-07; /* 0x34222168 */ 31 32 float 33 __ieee754_atan2f(float y, float x) 34 { 35 float z; 36 int32_t k,m,hx,hy,ix,iy; 37 38 GET_FLOAT_WORD(hx,x); 39 ix = hx&0x7fffffff; 40 GET_FLOAT_WORD(hy,y); 41 iy = hy&0x7fffffff; 42 if((ix>0x7f800000)|| 43 (iy>0x7f800000)) /* x or y is NaN */ 44 return x+y; 45 if(hx==0x3f800000) return atanf(y); /* x=1.0 */ 46 m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */ 47 48 /* when y = 0 */ 49 if(iy==0) { 50 switch(m) { 51 case 0: 52 case 1: return y; /* atan(+-0,+anything)=+-0 */ 53 case 2: return pi+tiny;/* atan(+0,-anything) = pi */ 54 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */ 55 } 56 } 57 /* when x = 0 */ 58 if(ix==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 59 60 /* when x is INF */ 61 if(ix==0x7f800000) { 62 if(iy==0x7f800000) { 63 switch(m) { 64 case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */ 65 case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */ 66 case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/ 67 case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/ 68 } 69 } else { 70 switch(m) { 71 case 0: return zero ; /* atan(+...,+INF) */ 72 case 1: return -zero ; /* atan(-...,+INF) */ 73 case 2: return pi+tiny ; /* atan(+...,-INF) */ 74 case 3: return -pi-tiny ; /* atan(-...,-INF) */ 75 } 76 } 77 } 78 /* when y is INF */ 79 if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 80 81 /* compute y/x */ 82 k = (iy-ix)>>23; 83 if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */ 84 else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */ 85 else z=atanf(fabsf(y/x)); /* safe to do y/x */ 86 switch (m) { 87 case 0: return z ; /* atan(+,+) */ 88 case 1: { 89 u_int32_t zh; 90 GET_FLOAT_WORD(zh,z); 91 SET_FLOAT_WORD(z,zh ^ 0x80000000); 92 } 93 return z ; /* atan(-,+) */ 94 case 2: return pi-(z-pi_lo);/* atan(+,-) */ 95 default: /* case 3 */ 96 return (z-pi_lo)-pi;/* atan(-,-) */ 97 } 98 } 99