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#include <math.h>
17#include <math_private.h>
18
19static const float
20ln2_hi = 6.9313812256e-01, /* 0x3f317180 */
21ln2_lo = 9.0580006145e-06, /* 0x3717f7d1 */
22two25 = 3.355443200e+07, /* 0x4c000000 */
23Lg1 = 6.6666668653e-01, /* 3F2AAAAB */
24Lg2 = 4.0000000596e-01, /* 3ECCCCCD */
25Lg3 = 2.8571429849e-01, /* 3E924925 */
26Lg4 = 2.2222198546e-01, /* 3E638E29 */
27Lg5 = 1.8183572590e-01, /* 3E3A3325 */
28Lg6 = 1.5313838422e-01, /* 3E1CD04F */
29Lg7 = 1.4798198640e-01; /* 3E178897 */
30
31static const float zero = 0.0;
32
33float
34__ieee754_logf(float x)
35{
36 float hfsq,f,s,z,R,w,t1,t2,dk;
37 int32_t k,ix,i,j;
38
39 GET_FLOAT_WORD(ix,x);
40
41 k=0;
42 if (ix < 0x00800000) { /* x < 2**-126 */
43 if (__builtin_expect((ix&0x7fffffff)==0, 0))
44 return -two25/zero; /* log(+-0)=-inf */
45 if (__builtin_expect(ix<0, 0))
46 return (x-x)/(x-x); /* log(-#) = NaN */
47 k -= 25; x *= two25; /* subnormal number, scale up x */
48 GET_FLOAT_WORD(ix,x);
49 }
50 if (__builtin_expect(ix >= 0x7f800000, 0)) return x+x;
51 k += (ix>>23)-127;
52 ix &= 0x007fffff;
53 i = (ix+(0x95f64<<3))&0x800000;
54 SET_FLOAT_WORD(x,ix|(i^0x3f800000)); /* normalize x or x/2 */
55 k += (i>>23);
56 f = x-(float)1.0;
57 if((0x007fffff&(15+ix))<16) { /* |f| < 2**-20 */
58 if(f==zero) {
59 if(k==0) return zero; else {dk=(float)k;
60 return dk*ln2_hi+dk*ln2_lo;}
61 }
62 R = f*f*((float)0.5-(float)0.33333333333333333*f);
63 if(k==0) return f-R; else {dk=(float)k;
64 return dk*ln2_hi-((R-dk*ln2_lo)-f);}
65 }
66 s = f/((float)2.0+f);
67 dk = (float)k;
68 z = s*s;
69 i = ix-(0x6147a<<3);
70 w = z*z;
71 j = (0x6b851<<3)-ix;
72 t1= w*(Lg2+w*(Lg4+w*Lg6));
73 t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));
74 i |= j;
75 R = t2+t1;
76 if(i>0) {
77 hfsq=(float)0.5*f*f;
78 if(k==0) return f-(hfsq-s*(hfsq+R)); else
79 return dk*ln2_hi-((hfsq-(s*(hfsq+R)+dk*ln2_lo))-f);
80 } else {
81 if(k==0) return f-s*(f-R); else
82 return dk*ln2_hi-((s*(f-R)-dk*ln2_lo)-f);
83 }
84}
85strong_alias (__ieee754_logf, __logf_finite)
86