1 /* ef_atan2.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 17 #include "fdlibm.h" 18 19 #ifdef __STDC__ 20 static const float 21 #else 22 static float 23 #endif 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 #ifdef __STDC__ __ieee754_atan2f(float y,float x)32 float __ieee754_atan2f(float y, float x) 33 #else 34 float __ieee754_atan2f(y,x) 35 float y,x; 36 #endif 37 { 38 float z; 39 __int32_t k,m,hx,hy,ix,iy; 40 41 GET_FLOAT_WORD(hx,x); 42 ix = hx&0x7fffffff; 43 GET_FLOAT_WORD(hy,y); 44 iy = hy&0x7fffffff; 45 if(FLT_UWORD_IS_NAN(ix)|| 46 FLT_UWORD_IS_NAN(iy)) /* x or y is NaN */ 47 return x+y; 48 if(hx==0x3f800000) return atanf(y); /* x=1.0 */ 49 m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */ 50 51 /* when y = 0 */ 52 if(FLT_UWORD_IS_ZERO(iy)) { 53 switch(m) { 54 case 0: 55 case 1: return y; /* atan(+-0,+anything)=+-0 */ 56 case 2: return pi+tiny;/* atan(+0,-anything) = pi */ 57 case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */ 58 } 59 } 60 /* when x = 0 */ 61 if(FLT_UWORD_IS_ZERO(ix)) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 62 63 /* when x is INF */ 64 if(FLT_UWORD_IS_INFINITE(ix)) { 65 if(FLT_UWORD_IS_INFINITE(iy)) { 66 switch(m) { 67 case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */ 68 case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */ 69 case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/ 70 case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/ 71 } 72 } else { 73 switch(m) { 74 case 0: return zero ; /* atan(+...,+INF) */ 75 case 1: return -zero ; /* atan(-...,+INF) */ 76 case 2: return pi+tiny ; /* atan(+...,-INF) */ 77 case 3: return -pi-tiny ; /* atan(-...,-INF) */ 78 } 79 } 80 } 81 /* when y is INF */ 82 if(FLT_UWORD_IS_INFINITE(iy)) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 83 84 /* compute y/x */ 85 k = (iy-ix)>>23; 86 if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */ 87 else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */ 88 else z=atanf(fabsf(y/x)); /* safe to do y/x */ 89 switch (m) { 90 case 0: return z ; /* atan(+,+) */ 91 case 1: { 92 __uint32_t zh; 93 GET_FLOAT_WORD(zh,z); 94 SET_FLOAT_WORD(z,zh ^ 0x80000000); 95 } 96 return z ; /* atan(-,+) */ 97 case 2: return pi-(z-pi_lo);/* atan(+,-) */ 98 default: /* case 3 */ 99 return (z-pi_lo)-pi;/* atan(-,-) */ 100 } 101 } 102