e_atan2f.c revision 2116
1193326Sed/* e_atan2f.c -- float version of e_atan2.c. 2193326Sed * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3193326Sed */ 4193326Sed 5193326Sed/* 6193326Sed * ==================================================== 7193326Sed * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 8193326Sed * 9193326Sed * Developed at SunPro, a Sun Microsystems, Inc. business. 10193326Sed * Permission to use, copy, modify, and distribute this 11193326Sed * software is freely granted, provided that this notice 12193326Sed * is preserved. 13193326Sed * ==================================================== 14193326Sed */ 15193326Sed 16193326Sed#ifndef lint 17193326Sedstatic char rcsid[] = "$Id: e_atan2f.c,v 1.2 1994/08/18 23:05:11 jtc Exp $"; 18193326Sed#endif 19198092Srdivacky 20193326Sed#include "math.h" 21193326Sed#include "math_private.h" 22193326Sed 23193326Sed#ifdef __STDC__ 24193326Sedstatic const float 25193326Sed#else 26193326Sedstatic float 27193326Sed#endif 28193326Sedtiny = 1.0e-30, 29193326Sedzero = 0.0, 30193326Sedpi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */ 31193326Sedpi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */ 32193326Sedpi = 3.1415925026e+00, /* 0x40490fda */ 33193326Sedpi_lo = 1.5099578832e-07; /* 0x34222168 */ 34193326Sed 35193326Sed#ifdef __STDC__ 36218893Sdim float __ieee754_atan2f(float y, float x) 37218893Sdim#else 38193326Sed float __ieee754_atan2f(y,x) 39193326Sed float y,x; 40193326Sed#endif 41193326Sed{ 42193326Sed float z; 43193326Sed int32_t k,m,hx,hy,ix,iy; 44193326Sed 45193326Sed GET_FLOAT_WORD(hx,x); 46193326Sed ix = hx&0x7fffffff; 47198092Srdivacky GET_FLOAT_WORD(hy,y); 48193326Sed iy = hy&0x7fffffff; 49193326Sed if((ix>0x7f800000)|| 50193326Sed (iy>0x7f800000)) /* x or y is NaN */ 51193326Sed return x+y; 52193326Sed if(hx==0x3f800000) return atanf(y); /* x=1.0 */ 53193326Sed m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */ 54193326Sed 55193326Sed /* when y = 0 */ 56193326Sed if(iy==0) { 57218893Sdim switch(m) { 58218893Sdim case 0: 59193326Sed case 1: return y; /* atan(+-0,+anything)=+-0 */ 60193326Sed case 2: return pi+tiny;/* atan(+0,-anything) = pi */ 61194179Sed case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */ 62218893Sdim } 63218893Sdim } 64194179Sed /* when x = 0 */ 65194179Sed if(ix==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 66193326Sed 67193326Sed /* when x is INF */ 68193326Sed if(ix==0x7f800000) { 69193326Sed if(iy==0x7f800000) { 70193326Sed switch(m) { 71193326Sed case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */ 72193326Sed case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */ 73193326Sed case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/ 74193326Sed case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/ 75193326Sed } 76193326Sed } else { 77193326Sed switch(m) { 78193326Sed case 0: return zero ; /* atan(+...,+INF) */ 79193326Sed case 1: return -zero ; /* atan(-...,+INF) */ 80193326Sed case 2: return pi+tiny ; /* atan(+...,-INF) */ 81193326Sed case 3: return -pi-tiny ; /* atan(-...,-INF) */ 82193326Sed } 83193326Sed } 84218893Sdim } 85218893Sdim /* when y is INF */ 86193326Sed if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 87193326Sed 88193326Sed /* compute y/x */ 89198092Srdivacky k = (iy-ix)>>23; 90193326Sed if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */ 91193326Sed else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */ 92193326Sed else z=atanf(fabsf(y/x)); /* safe to do y/x */ 93193326Sed switch (m) { 94193326Sed case 0: return z ; /* atan(+,+) */ 95193326Sed case 1: { 96193326Sed u_int32_t zh; 97193326Sed GET_FLOAT_WORD(zh,z); 98193326Sed SET_FLOAT_WORD(z,zh ^ 0x80000000); 99193326Sed } 100193326Sed return z ; /* atan(-,+) */ 101193326Sed case 2: return pi-(z-pi_lo);/* atan(+,-) */ 102218893Sdim default: /* case 3 */ 103218893Sdim return (z-pi_lo)-pi;/* atan(-,-) */ 104198092Srdivacky } 105193326Sed} 106193326Sed