OpenCores
URL https://opencores.org/ocsvn/or1k/or1k/trunk

Subversion Repositories or1k

[/] [or1k/] [trunk/] [newlib/] [newlib/] [libm/] [math/] [ef_log.c] - Blame information for rev 39

Go to most recent revision | Details | Compare with Previous | View Log

Line No. Rev Author Line
1 39 lampret 
/* ef_log.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 
#include "fdlibm.h"
17 
 
18 
#ifdef __STDC__
19 
static const float
20 
#else
21 
static float
22 
#endif
23 
ln2_hi =   6.9313812256e-01,    /* 0x3f317180 */
24 
ln2_lo =   9.0580006145e-06,    /* 0x3717f7d1 */
25 
two25 =    3.355443200e+07,     /* 0x4c000000 */
26 
Lg1 = 6.6666668653e-01, /* 3F2AAAAB */
27 
Lg2 = 4.0000000596e-01, /* 3ECCCCCD */
28 
Lg3 = 2.8571429849e-01, /* 3E924925 */
29 
Lg4 = 2.2222198546e-01, /* 3E638E29 */
30 
Lg5 = 1.8183572590e-01, /* 3E3A3325 */
31 
Lg6 = 1.5313838422e-01, /* 3E1CD04F */
32 
Lg7 = 1.4798198640e-01; /* 3E178897 */
33 
 
34 
#ifdef __STDC__
35 
static const float zero   =  0.0;
36 
#else
37 
static float zero   =  0.0;
38 
#endif
39 
 
40 
#ifdef __STDC__
41 
        float __ieee754_logf(float x)
42 
#else
43 
        float __ieee754_logf(x)
44 
        float x;
45 
#endif
46 
{
47 
        float hfsq,f,s,z,R,w,t1,t2,dk;
48 
        __int32_t k,ix,i,j;
49 
 
50 
        GET_FLOAT_WORD(ix,x);
51 
 
52 
        k=0;
53 
        if (ix < 0x00800000) {                  /* x < 2**-126  */
54 
            if ((ix&0x7fffffff)==0)
55 
                return -two25/zero;             /* log(+-0)=-inf */
56 
            if (ix<0) return (x-x)/zero; /* log(-#) = NaN */
57 
            k -= 25; x *= two25; /* subnormal number, scale up x */
58 
            GET_FLOAT_WORD(ix,x);
59 
        }
60 
        if (ix >= 0x7f800000) return x+x;
61 
        k += (ix>>23)-127;
62 
        ix &= 0x007fffff;
63 
        i = (ix+(0x95f64<<3))&0x800000;
64 
        SET_FLOAT_WORD(x,ix|(i^0x3f800000));    /* normalize x or x/2 */
65 
        k += (i>>23);
66 
        f = x-(float)1.0;
67 
        if((0x007fffff&(15+ix))<16) {   /* |f| < 2**-20 */
68 
            if(f==zero) if(k==0) return zero;  else {dk=(float)k;
69 
                                 return dk*ln2_hi+dk*ln2_lo;}
70 
            R = f*f*((float)0.5-(float)0.33333333333333333*f);
71 
            if(k==0) return f-R; else {dk=(float)k;
72 
                     return dk*ln2_hi-((R-dk*ln2_lo)-f);}
73 
        }
74 
        s = f/((float)2.0+f);
75 
        dk = (float)k;
76 
        z = s*s;
77 
        i = ix-(0x6147a<<3);
78 
        w = z*z;
79 
        j = (0x6b851<<3)-ix;
80 
        t1= w*(Lg2+w*(Lg4+w*Lg6));
81 
        t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));
82 
        i |= j;
83 
        R = t2+t1;
84 
        if(i>0) {
85 
            hfsq=(float)0.5*f*f;
86 
            if(k==0) return f-(hfsq-s*(hfsq+R)); else
87 
                     return dk*ln2_hi-((hfsq-(s*(hfsq+R)+dk*ln2_lo))-f);
88 
        } else {
89 
            if(k==0) return f-s*(f-R); else
90 
                     return dk*ln2_hi-((s*(f-R)-dk*ln2_lo)-f);
91 
        }
92 
}

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.