e_atan2f.c (2795B)
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 #ifndef lint 17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_atan2f.c,v 1.7 2004/06/02 17:09:05 bde Exp $"; 18 #endif 19 20 #include "math.h" 21 #include "math_private.h" 22 23 static const float 24 tiny = 1.0e-30, 25 zero = 0.0, 26 pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */ 27 pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */ 28 pi = 3.1415927410e+00, /* 0x40490fdb */ 29 pi_lo = -8.7422776573e-08; /* 0xb3bbbd2e */ 30 31 float 32 __ieee754_atan2f(float y, float x) 33 { 34 float z; 35 int32_t k,m,hx,hy,ix,iy; 36 37 GET_FLOAT_WORD(hx,x); 38 ix = hx&0x7fffffff; 39 GET_FLOAT_WORD(hy,y); 40 iy = hy&0x7fffffff; 41 if((ix>0x7f800000)|| 42 (iy>0x7f800000)) /* x or y is NaN */ 43 return x+y; 44 if(hx==0x3f800000) return atanf(y); /* x=1.0 */ 45 m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */ 46 47 /* when y = 0 */ 48 if(iy==0) { 49 switch(m) { 50 case 0: 51 case 1: return y; /* atan(+-0,+anything)=+-0 */ 52 case 2: return pi+tiny;/* atan(+0,-anything) = pi */ 53 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */ 54 } 55 } 56 /* when x = 0 */ 57 if(ix==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 58 59 /* when x is INF */ 60 if(ix==0x7f800000) { 61 if(iy==0x7f800000) { 62 switch(m) { 63 case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */ 64 case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */ 65 case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/ 66 case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/ 67 } 68 } else { 69 switch(m) { 70 case 0: return zero ; /* atan(+...,+INF) */ 71 case 1: return -zero ; /* atan(-...,+INF) */ 72 case 2: return pi+tiny ; /* atan(+...,-INF) */ 73 case 3: return -pi-tiny ; /* atan(-...,-INF) */ 74 } 75 } 76 } 77 /* when y is INF */ 78 if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 79 80 /* compute y/x */ 81 k = (iy-ix)>>23; 82 if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */ 83 else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */ 84 else z=atanf(fabsf(y/x)); /* safe to do y/x */ 85 switch (m) { 86 case 0: return z ; /* atan(+,+) */ 87 case 1: { 88 u_int32_t zh; 89 GET_FLOAT_WORD(zh,z); 90 SET_FLOAT_WORD(z,zh ^ 0x80000000); 91 } 92 return z ; /* atan(-,+) */ 93 case 2: return pi-(z-pi_lo);/* atan(+,-) */ 94 default: /* case 3 */ 95 return (z-pi_lo)-pi;/* atan(-,-) */ 96 } 97 }