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/* ef_log.c -- float version of e_log.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 "fdlibm.h"

#ifdef __STDC__

static const float

#else

static float

#endif

ln2_hi =   6.9313812256e-01,    /* 0x3f317180 */

ln2_lo =   9.0580006145e-06,    /* 0x3717f7d1 */

two25 =    3.355443200e+07,     /* 0x4c000000 */

Lg1 = 6.6666668653e-01, /* 3F2AAAAB */

Lg2 = 4.0000000596e-01, /* 3ECCCCCD */

Lg3 = 2.8571429849e-01, /* 3E924925 */

Lg4 = 2.2222198546e-01, /* 3E638E29 */

Lg5 = 1.8183572590e-01, /* 3E3A3325 */

Lg6 = 1.5313838422e-01, /* 3E1CD04F */

Lg7 = 1.4798198640e-01; /* 3E178897 */

#ifdef __STDC__

static const float zero   =  0.0;

#else

static float zero   =  0.0;

#endif

#ifdef __STDC__

        float __ieee754_logf(float x)

#else

        float __ieee754_logf(x)

        float x;

#endif

{

        float hfsq,f,s,z,R,w,t1,t2,dk;

        __int32_t k,ix,i,j;

        GET_FLOAT_WORD(ix,x);

        k=0;

        if (FLT_UWORD_IS_ZERO(ix&0x7fffffff))

            return -two25/zero;         /* log(+-0)=-inf */

        if (ix<0) return (x-x)/zero;     /* log(-#) = NaN */

        if (!FLT_UWORD_IS_FINITE(ix)) return x+x;

        if (FLT_UWORD_IS_SUBNORMAL(ix)) {

            k -= 25; x *= two25; /* subnormal number, scale up x */

            GET_FLOAT_WORD(ix,x);

        }

        k += (ix>>23)-127;

        ix &= 0x007fffff;

        i = (ix+(0x95f64<<3))&0x800000;

        SET_FLOAT_WORD(x,ix|(i^0x3f800000));    /* normalize x or x/2 */

        k += (i>>23);

        f = x-(float)1.0;

        if((0x007fffff&(15+ix))<16) {   /* |f| < 2**-20 */

           if(f==zero) { if(k==0) return zero;  else {dk=(float)k;

                                return dk*ln2_hi+dk*ln2_lo;}}

            R = f*f*((float)0.5-(float)0.33333333333333333*f);

            if(k==0) return f-R; else {dk=(float)k;

                     return dk*ln2_hi-((R-dk*ln2_lo)-f);}

        }

        s = f/((float)2.0+f);

        dk = (float)k;

        z = s*s;

        i = ix-(0x6147a<<3);

        w = z*z;

        j = (0x6b851<<3)-ix;

        t1= w*(Lg2+w*(Lg4+w*Lg6));

        t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));

        i |= j;

        R = t2+t1;

        if(i>0) {

            hfsq=(float)0.5*f*f;

            if(k==0) return f-(hfsq-s*(hfsq+R)); else

                     return dk*ln2_hi-((hfsq-(s*(hfsq+R)+dk*ln2_lo))-f);

        } else {

            if(k==0) return f-s*(f-R); else

                     return dk*ln2_hi-((s*(f-R)-dk*ln2_lo)-f);

        }

}