1 /* e_log10f.c -- float version of e_log10.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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
13 * ====================================================
17 static char rcsid[] = "$FreeBSD$";
21 #include "math_private.h"
24 two25 = 3.3554432000e+07, /* 0x4c000000 */
25 ivln10 = 4.3429449201e-01, /* 0x3ede5bd9 */
26 log10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */
27 log10_2lo = 7.9034151668e-07; /* 0x355427db */
29 static const float zero = 0.0;
32 __ieee754_log10f(float x)
40 if (hx < 0x00800000) { /* x < 2**-126 */
41 if ((hx&0x7fffffff)==0)
42 return -two25/zero; /* log(+-0)=-inf */
43 if (hx<0) return (x-x)/zero; /* log(-#) = NaN */
44 k -= 25; x *= two25; /* subnormal number, scale up x */
47 if (hx >= 0x7f800000) return x+x;
49 i = ((u_int32_t)k&0x80000000)>>31;
50 hx = (hx&0x007fffff)|((0x7f-i)<<23);
53 z = y*log10_2lo + ivln10*__ieee754_logf(x);