12116Sjkh/* s_atanf.c -- float version of s_atan.c.
22116Sjkh * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
32116Sjkh */
42116Sjkh
52116Sjkh/*
62116Sjkh * ====================================================
72116Sjkh * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
82116Sjkh *
92116Sjkh * Developed at SunPro, a Sun Microsystems, Inc. business.
102116Sjkh * Permission to use, copy, modify, and distribute this
118870Srgrimes * software is freely granted, provided that this notice
122116Sjkh * is preserved.
132116Sjkh * ====================================================
142116Sjkh */
152116Sjkh
16176451Sdas#include <sys/cdefs.h>
17176451Sdas__FBSDID("$FreeBSD$");
182116Sjkh
192116Sjkh#include "math.h"
202116Sjkh#include "math_private.h"
212116Sjkh
222116Sjkhstatic const float atanhi[] = {
232116Sjkh  4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
242116Sjkh  7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
252116Sjkh  9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
262116Sjkh  1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
272116Sjkh};
282116Sjkh
292116Sjkhstatic const float atanlo[] = {
302116Sjkh  5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
312116Sjkh  3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
322116Sjkh  3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
332116Sjkh  7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
342116Sjkh};
352116Sjkh
362116Sjkhstatic const float aT[] = {
37181100Sdas  3.3333328366e-01,
38181100Sdas -1.9999158382e-01,
39181100Sdas  1.4253635705e-01,
40181100Sdas -1.0648017377e-01,
41181100Sdas  6.1687607318e-02,
422116Sjkh};
432116Sjkh
44181100Sdasstatic const float
452116Sjkhone   = 1.0,
462116Sjkhhuge   = 1.0e30;
472116Sjkh
4897413Salfredfloat
4997413Salfredatanf(float x)
502116Sjkh{
512116Sjkh	float w,s1,s2,z;
522116Sjkh	int32_t ix,hx,id;
532116Sjkh
542116Sjkh	GET_FLOAT_WORD(hx,x);
552116Sjkh	ix = hx&0x7fffffff;
56181100Sdas	if(ix>=0x4c800000) {	/* if |x| >= 2**26 */
572116Sjkh	    if(ix>0x7f800000)
582116Sjkh		return x+x;		/* NaN */
59181062Sdas	    if(hx>0) return  atanhi[3]+*(volatile float *)&atanlo[3];
60181062Sdas	    else     return -atanhi[3]-*(volatile float *)&atanlo[3];
612116Sjkh	} if (ix < 0x3ee00000) {	/* |x| < 0.4375 */
62181100Sdas	    if (ix < 0x39800000) {	/* |x| < 2**-12 */
632116Sjkh		if(huge+x>one) return x;	/* raise inexact */
642116Sjkh	    }
652116Sjkh	    id = -1;
662116Sjkh	} else {
672116Sjkh	x = fabsf(x);
682116Sjkh	if (ix < 0x3f980000) {		/* |x| < 1.1875 */
692116Sjkh	    if (ix < 0x3f300000) {	/* 7/16 <=|x|<11/16 */
708870Srgrimes		id = 0; x = ((float)2.0*x-one)/((float)2.0+x);
712116Sjkh	    } else {			/* 11/16<=|x|< 19/16 */
728870Srgrimes		id = 1; x  = (x-one)/(x+one);
732116Sjkh	    }
742116Sjkh	} else {
752116Sjkh	    if (ix < 0x401c0000) {	/* |x| < 2.4375 */
762116Sjkh		id = 2; x  = (x-(float)1.5)/(one+(float)1.5*x);
77181100Sdas	    } else {			/* 2.4375 <= |x| < 2**26 */
782116Sjkh		id = 3; x  = -(float)1.0/x;
792116Sjkh	    }
802116Sjkh	}}
812116Sjkh    /* end of argument reduction */
822116Sjkh	z = x*x;
832116Sjkh	w = z*z;
842116Sjkh    /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
85181100Sdas	s1 = z*(aT[0]+w*(aT[2]+w*aT[4]));
86181100Sdas	s2 = w*(aT[1]+w*aT[3]);
872116Sjkh	if (id<0) return x - x*(s1+s2);
882116Sjkh	else {
892116Sjkh	    z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
902116Sjkh	    return (hx<0)? -z:z;
912116Sjkh	}
922116Sjkh}
93