| /* ef_atan2.c -- float version of e_atan2.c. |
| * Conversion to float by Ian Lance Taylor, Cygnus Support, [email protected]. |
| */ |
| |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| * |
| */ |
| |
| #include "fdlibm.h" |
| |
| #ifdef __STDC__ |
| static const float |
| #else |
| static float |
| #endif |
| tiny = 1.0e-30, |
| zero = 0.0, |
| pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */ |
| pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */ |
| pi = 3.1415927410e+00, /* 0x40490fdb */ |
| pi_lo = -8.7422776573e-08; /* 0xb3bbbd2e */ |
| |
| #ifdef __STDC__ |
| float __ieee754_atan2f(float y, float x) |
| #else |
| float __ieee754_atan2f(y,x) |
| float y,x; |
| #endif |
| { |
| float z; |
| __int32_t k,m,hx,hy,ix,iy; |
| |
| GET_FLOAT_WORD(hx,x); |
| ix = hx&0x7fffffff; |
| GET_FLOAT_WORD(hy,y); |
| iy = hy&0x7fffffff; |
| if(FLT_UWORD_IS_NAN(ix)|| |
| FLT_UWORD_IS_NAN(iy)) /* x or y is NaN */ |
| return x+y; |
| if(hx==0x3f800000) return atanf(y); /* x=1.0 */ |
| m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */ |
| |
| /* when y = 0 */ |
| if(FLT_UWORD_IS_ZERO(iy)) { |
| switch(m) { |
| case 0: |
| case 1: return y; /* atan(+-0,+anything)=+-0 */ |
| case 2: return pi+tiny;/* atan(+0,-anything) = pi */ |
| case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */ |
| } |
| } |
| /* when x = 0 */ |
| if(FLT_UWORD_IS_ZERO(ix)) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; |
| |
| /* when x is INF */ |
| if(FLT_UWORD_IS_INFINITE(ix)) { |
| if(FLT_UWORD_IS_INFINITE(iy)) { |
| switch(m) { |
| case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */ |
| case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */ |
| case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/ |
| case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/ |
| } |
| } else { |
| switch(m) { |
| case 0: return zero ; /* atan(+...,+INF) */ |
| case 1: return -zero ; /* atan(-...,+INF) */ |
| case 2: return pi+tiny ; /* atan(+...,-INF) */ |
| case 3: return -pi-tiny ; /* atan(-...,-INF) */ |
| } |
| } |
| } |
| /* when y is INF */ |
| if(FLT_UWORD_IS_INFINITE(iy)) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; |
| |
| /* compute y/x */ |
| k = (iy-ix)>>23; |
| if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */ |
| else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */ |
| else z=atanf(fabsf(y/x)); /* safe to do y/x */ |
| switch (m) { |
| case 0: return z ; /* atan(+,+) */ |
| case 1: { |
| __uint32_t zh; |
| GET_FLOAT_WORD(zh,z); |
| SET_FLOAT_WORD(z,zh ^ 0x80000000); |
| } |
| return z ; /* atan(-,+) */ |
| case 2: return pi-(z-pi_lo);/* atan(+,-) */ |
| default: /* case 3 */ |
| return (z-pi_lo)-pi;/* atan(-,-) */ |
| } |
| } |
