vx32

Local 9vx git repository for patches.
git clone git://r-36.net/vx32
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e_logf.c (2442B)


      1 /* e_logf.c -- float version of e_log.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 #ifndef lint
     17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_logf.c,v 1.7 2002/05/28 18:15:04 alfred Exp $";
     18 #endif
     19 
     20 #include "math.h"
     21 #include "math_private.h"
     22 
     23 static const float
     24 ln2_hi =   6.9313812256e-01,	/* 0x3f317180 */
     25 ln2_lo =   9.0580006145e-06,	/* 0x3717f7d1 */
     26 two25 =    3.355443200e+07,	/* 0x4c000000 */
     27 Lg1 = 6.6666668653e-01,	/* 3F2AAAAB */
     28 Lg2 = 4.0000000596e-01,	/* 3ECCCCCD */
     29 Lg3 = 2.8571429849e-01, /* 3E924925 */
     30 Lg4 = 2.2222198546e-01, /* 3E638E29 */
     31 Lg5 = 1.8183572590e-01, /* 3E3A3325 */
     32 Lg6 = 1.5313838422e-01, /* 3E1CD04F */
     33 Lg7 = 1.4798198640e-01; /* 3E178897 */
     34 
     35 static const float zero   =  0.0;
     36 
     37 float
     38 __ieee754_logf(float x)
     39 {
     40 	float hfsq,f,s,z,R,w,t1,t2,dk;
     41 	int32_t k,ix,i,j;
     42 
     43 	GET_FLOAT_WORD(ix,x);
     44 
     45 	k=0;
     46 	if (ix < 0x00800000) {			/* x < 2**-126  */
     47 	    if ((ix&0x7fffffff)==0)
     48 		return -two25/zero;		/* log(+-0)=-inf */
     49 	    if (ix<0) return (x-x)/zero;	/* log(-#) = NaN */
     50 	    k -= 25; x *= two25; /* subnormal number, scale up x */
     51 	    GET_FLOAT_WORD(ix,x);
     52 	}
     53 	if (ix >= 0x7f800000) return x+x;
     54 	k += (ix>>23)-127;
     55 	ix &= 0x007fffff;
     56 	i = (ix+(0x95f64<<3))&0x800000;
     57 	SET_FLOAT_WORD(x,ix|(i^0x3f800000));	/* normalize x or x/2 */
     58 	k += (i>>23);
     59 	f = x-(float)1.0;
     60 	if((0x007fffff&(15+ix))<16) {	/* |f| < 2**-20 */
     61 	    if(f==zero) if(k==0) return zero;  else {dk=(float)k;
     62 				 return dk*ln2_hi+dk*ln2_lo;}
     63 	    R = f*f*((float)0.5-(float)0.33333333333333333*f);
     64 	    if(k==0) return f-R; else {dk=(float)k;
     65 	    	     return dk*ln2_hi-((R-dk*ln2_lo)-f);}
     66 	}
     67  	s = f/((float)2.0+f);
     68 	dk = (float)k;
     69 	z = s*s;
     70 	i = ix-(0x6147a<<3);
     71 	w = z*z;
     72 	j = (0x6b851<<3)-ix;
     73 	t1= w*(Lg2+w*(Lg4+w*Lg6));
     74 	t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));
     75 	i |= j;
     76 	R = t2+t1;
     77 	if(i>0) {
     78 	    hfsq=(float)0.5*f*f;
     79 	    if(k==0) return f-(hfsq-s*(hfsq+R)); else
     80 		     return dk*ln2_hi-((hfsq-(s*(hfsq+R)+dk*ln2_lo))-f);
     81 	} else {
     82 	    if(k==0) return f-s*(f-R); else
     83 		     return dk*ln2_hi-((s*(f-R)-dk*ln2_lo)-f);
     84 	}
     85 }