2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
9 * ====================================================
13 * Float version of e_log10.c. See the latter for most comments.
17 #include "math_private.h"
21 two25 = 3.3554432000e+07, /* 0x4c000000 */
22 ivln10hi = 4.3432617188e-01, /* 0x3ede6000 */
23 ivln10lo = -3.1689971365e-05, /* 0xb804ead9 */
24 log10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */
25 log10_2lo = 7.9034151668e-07; /* 0x355427db */
27 static const float zero = 0.0;
28 static volatile float vzero = 0.0;
33 float f,hfsq,hi,lo,r,y;
39 if (hx < 0x00800000) { /* x < 2**-126 */
40 if ((hx&0x7fffffff)==0)
41 return -two25/vzero; /* log(+-0)=-inf */
42 if (hx<0) return (x-x)/zero; /* log(-#) = NaN */
43 k -= 25; x *= two25; /* subnormal number, scale up x */
46 if (hx >= 0x7f800000) return x+x;
48 return zero; /* log(1) = +0 */
51 i = (hx+(0x4afb0d))&0x800000;
52 SET_FLOAT_WORD(x,hx|(i^0x3f800000)); /* normalize x or x/2 */
56 hfsq = (float)0.5*f*f;
59 /* See e_log2f.c and e_log2.c for details. */
60 if (sizeof(float_t) > sizeof(float))
61 return (r - hfsq + f) * ((float_t)ivln10lo + ivln10hi) +
62 y * ((float_t)log10_2lo + log10_2hi);
64 GET_FLOAT_WORD(hx,hi);
65 SET_FLOAT_WORD(hi,hx&0xfffff000);
66 lo = (f - hi) - hfsq + r;
67 return y*log10_2lo + (lo+hi)*ivln10lo + lo*ivln10hi + hi*ivln10hi +