1 /* s_atanf.c -- float version of s_atan.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 #include "cdefs-compat.h" 17 //__FBSDID("$FreeBSD: src/lib/msun/src/s_atanf.c,v 1.10 2008/08/01 01:24:25 das Exp $"); 18 19 #include <openlibm_math.h> 20 21 #include "math_private.h" 22 23 static const float atanhi[] = { 24 4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */ 25 7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */ 26 9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */ 27 1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */ 28 }; 29 30 static const float atanlo[] = { 31 5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */ 32 3.7748947079e-08, /* atan(1.0)lo 0x33222168 */ 33 3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */ 34 7.5497894159e-08, /* atan(inf)lo 0x33a22168 */ 35 }; 36 37 static const float aT[] = { 38 3.3333328366e-01, 39 -1.9999158382e-01, 40 1.4253635705e-01, 41 -1.0648017377e-01, 42 6.1687607318e-02, 43 }; 44 45 static const float 46 one = 1.0, 47 huge = 1.0e30; 48 49 OLM_DLLEXPORT float 50 atanf(float x) 51 { 52 float w,s1,s2,z; 53 int32_t ix,hx,id; 54 55 GET_FLOAT_WORD(hx,x); 56 ix = hx&0x7fffffff; 57 if(ix>=0x4c800000) { /* if |x| >= 2**26 */ 58 if(ix>0x7f800000) 59 return x+x; /* NaN */ 60 if(hx>0) return atanhi[3]+*(volatile float *)&atanlo[3]; 61 else return -atanhi[3]-*(volatile float *)&atanlo[3]; 62 } if (ix < 0x3ee00000) { /* |x| < 0.4375 */ 63 if (ix < 0x39800000) { /* |x| < 2**-12 */ 64 if(huge+x>one) return x; /* raise inexact */ 65 } 66 id = -1; 67 } else { 68 x = fabsf(x); 69 if (ix < 0x3f980000) { /* |x| < 1.1875 */ 70 if (ix < 0x3f300000) { /* 7/16 <=|x|<11/16 */ 71 id = 0; x = ((float)2.0*x-one)/((float)2.0+x); 72 } else { /* 11/16<=|x|< 19/16 */ 73 id = 1; x = (x-one)/(x+one); 74 } 75 } else { 76 if (ix < 0x401c0000) { /* |x| < 2.4375 */ 77 id = 2; x = (x-(float)1.5)/(one+(float)1.5*x); 78 } else { /* 2.4375 <= |x| < 2**26 */ 79 id = 3; x = -(float)1.0/x; 80 } 81 }} 82 /* end of argument reduction */ 83 z = x*x; 84 w = z*z; 85 /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */ 86 s1 = z*(aT[0]+w*(aT[2]+w*aT[4])); 87 s2 = w*(aT[1]+w*aT[3]); 88 if (id<0) return x - x*(s1+s2); 89 else { 90 z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x); 91 return (hx<0)? -z:z; 92 } 93 } 94