e_atan2f.c revision 2117
10SN/A/* e_atan2f.c -- float version of e_atan2.c. 211928Sserb * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 30SN/A */ 40SN/A 50SN/A/* 60SN/A * ==================================================== 72362SN/A * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 80SN/A * 92362SN/A * Developed at SunPro, a Sun Microsystems, Inc. business. 100SN/A * Permission to use, copy, modify, and distribute this 110SN/A * software is freely granted, provided that this notice 120SN/A * is preserved. 130SN/A * ==================================================== 140SN/A */ 150SN/A 160SN/A#ifndef lint 170SN/Astatic char rcsid[] = "$Id: e_atan2f.c,v 1.2 1994/08/18 23:05:11 jtc Exp $"; 180SN/A#endif 190SN/A 200SN/A#include "math.h" 212362SN/A#include "math_private.h" 222362SN/A 232362SN/A#ifdef __STDC__ 240SN/Astatic const float 250SN/A#else 260SN/Astatic float 270SN/A#endif 280SN/Atiny = 1.0e-30, 290SN/Azero = 0.0, 300SN/Api_o_4 = 7.8539818525e-01, /* 0x3f490fdb */ 310SN/Api_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */ 320SN/Api = 3.1415925026e+00, /* 0x40490fda */ 330SN/Api_lo = 1.5099578832e-07; /* 0x34222168 */ 340SN/A 350SN/A#ifdef __STDC__ 360SN/A float __ieee754_atan2f(float y, float x) 375428SN/A#else 380SN/A float __ieee754_atan2f(y,x) 3913629Savstepan float y,x; 400SN/A#endif 410SN/A{ 420SN/A float z; 438926SN/A int32_t k,m,hx,hy,ix,iy; 440SN/A 450SN/A GET_FLOAT_WORD(hx,x); 460SN/A ix = hx&0x7fffffff; 470SN/A GET_FLOAT_WORD(hy,y); 480SN/A iy = hy&0x7fffffff; 490SN/A if((ix>0x7f800000)|| 500SN/A (iy>0x7f800000)) /* x or y is NaN */ 510SN/A return x+y; 520SN/A if(hx==0x3f800000) return atanf(y); /* x=1.0 */ 530SN/A m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */ 540SN/A 558234SN/A /* when y = 0 */ 560SN/A if(iy==0) { 5713629Savstepan switch(m) { 580SN/A case 0: 590SN/A case 1: return y; /* atan(+-0,+anything)=+-0 */ 600SN/A case 2: return pi+tiny;/* atan(+0,-anything) = pi */ 610SN/A case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */ 6213629Savstepan } 6313629Savstepan } 640SN/A /* when x = 0 */ 6513629Savstepan if(ix==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 660SN/A 6713629Savstepan /* when x is INF */ 689680SN/A if(ix==0x7f800000) { 690SN/A if(iy==0x7f800000) { 700SN/A switch(m) { 7110071SN/A case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */ 720SN/A case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */ 730SN/A case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/ 740SN/A case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/ 7513629Savstepan } 7613629Savstepan } else { 770SN/A switch(m) { 780SN/A case 0: return zero ; /* atan(+...,+INF) */ 790SN/A case 1: return -zero ; /* atan(-...,+INF) */ 800SN/A case 2: return pi+tiny ; /* atan(+...,-INF) */ 810SN/A case 3: return -pi-tiny ; /* atan(-...,-INF) */ 820SN/A } 830SN/A } 840SN/A } 856447SN/A /* when y is INF */ 860SN/A if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny; 870SN/A 8813629Savstepan /* compute y/x */ 890SN/A k = (iy-ix)>>23; 900SN/A if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */ 910SN/A else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */ 920SN/A else z=atanf(fabsf(y/x)); /* safe to do y/x */ 930SN/A switch (m) { 940SN/A case 0: return z ; /* atan(+,+) */ 950SN/A case 1: { 960SN/A u_int32_t zh; 970SN/A GET_FLOAT_WORD(zh,z); 980SN/A SET_FLOAT_WORD(z,zh ^ 0x80000000); 990SN/A } 1000SN/A return z ; /* atan(-,+) */ 1010SN/A case 2: return pi-(z-pi_lo);/* atan(+,-) */ 1020SN/A default: /* case 3 */ 1030SN/A return (z-pi_lo)-pi;/* atan(-,-) */ 1045906SN/A } 1055906SN/A} 1065906SN/A