text: /* s_log1pf.c -- float version of s_log1p.c.
   * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   */
  
  /*
   * ====================================================
   * 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 <sys/cdefs.h>
  #if defined(LIBM_SCCS) && !defined(lint)
  __RCSID("$NetBSD: s_log1pf.c,v 1.8 2002/05/26 22:01:57 wiz Exp $");
  #endif
  
  #include "math.h"
  #include "math_private.h"
  
  static const float
  ln2_hi =   6.9313812256e-01,	/* 0x3f317180 */
  ln2_lo =   9.0580006145e-06,	/* 0x3717f7d1 */
  two25 =    3.355443200e+07,	/* 0x4c000000 */
  Lp1 = 6.6666668653e-01,	/* 3F2AAAAB */
  Lp2 = 4.0000000596e-01,	/* 3ECCCCCD */
  Lp3 = 2.8571429849e-01, /* 3E924925 */
  Lp4 = 2.2222198546e-01, /* 3E638E29 */
  Lp5 = 1.8183572590e-01, /* 3E3A3325 */
  Lp6 = 1.5313838422e-01, /* 3E1CD04F */
  Lp7 = 1.4798198640e-01; /* 3E178897 */
  
  static const float zero = 0.0;
  
  float
  log1pf(float x)
  {
  	float hfsq,f,c,s,z,R,u;
  	int32_t k,hx,hu,ax;
  
  	f = c = 0;
  	hu = 0;
  	GET_FLOAT_WORD(hx,x);
  	ax = hx&0x7fffffff;
  
  	k = 1;
  	if (hx < 0x3ed413d7) {			/* x < 0.41422  */
  	    if(ax>=0x3f800000) {		/* x <= -1.0 */
  		if(x==(float)-1.0) return -two25/zero; /* log1p(-1)=+inf */
  		else return (x-x)/(x-x);	/* log1p(x<-1)=NaN */
  	    }
  	    if(ax<0x31000000) {			/* |x| < 2**-29 */
  		if(two25+x>zero			/* raise inexact */
  	            &&ax<0x24800000) 		/* |x| < 2**-54 */
  		    return x;
  		else
  		    return x - x*x*(float)0.5;
  	    }
  	    if(hx>0||hx<=((int32_t)0xbe95f61f)) {
  		k=0;f=x;hu=1;}	/* -0.2929<x<0.41422 */
  	}
  	if (hx >= 0x7f800000) return x+x;
  	if(k!=0) {
  	    if(hx<0x5a000000) {
  		u  = (float)1.0+x;
  		GET_FLOAT_WORD(hu,u);
  	        k  = (hu>>23)-127;
  		/* correction term */
  	        c  = (k>0)? (float)1.0-(u-x):x-(u-(float)1.0);
  		c /= u;
  	    } else {
  		u  = x;
  		GET_FLOAT_WORD(hu,u);
  	        k  = (hu>>23)-127;
  		c  = 0;
  	    }
  	    hu &= 0x007fffff;
  	    if(hu<0x3504f7) {
  	        SET_FLOAT_WORD(u,hu|0x3f800000);/* normalize u */
  	    } else {
  	        k += 1;
  		SET_FLOAT_WORD(u,hu|0x3f000000);	/* normalize u/2 */
  	        hu = (0x00800000-hu)>>2;
  	    }
  	    f = u-(float)1.0;
  	}
  	hfsq=(float)0.5*f*f;
  	if(hu==0) {	/* |f| < 2**-20 */
  	    if(f==zero) { if(k==0) return zero;
  			  else {c += k*ln2_lo; return k*ln2_hi+c;}
  	    }
  	    R = hfsq*((float)1.0-(float)0.66666666666666666*f);
  	    if(k==0) return f-R; else
  	    	     return k*ln2_hi-((R-(k*ln2_lo+c))-f);
  	}
   	s = f/((float)2.0+f);
  	z = s*s;
  	R = z*(Lp1+z*(Lp2+z*(Lp3+z*(Lp4+z*(Lp5+z*(Lp6+z*Lp7))))));
  	if(k==0) return f-(hfsq-s*(hfsq+R)); else
  		 return k*ln2_hi-((hfsq-(s*(hfsq+R)+(k*ln2_lo+c)))-f);
  }
  