1/* e_log10f.c -- float version of e_log10.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#include <fix-int-fp-convert-zero.h>
19#include <libm-alias-finite.h>
20
21static const float
22two25 = 3.3554432000e+07, /* 0x4c000000 */
23ivln10 = 4.3429449201e-01, /* 0x3ede5bd9 */
24log10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */
25log10_2lo = 7.9034151668e-07; /* 0x355427db */
26
27float
28__ieee754_log10f(float x)
29{
30 float y,z;
31 int32_t i,k,hx;
32
33 GET_FLOAT_WORD(hx,x);
34
35 k=0;
36 if (hx < 0x00800000) { /* x < 2**-126 */
37 if (__builtin_expect((hx&0x7fffffff)==0, 0))
38 return -two25/fabsf (x); /* log(+-0)=-inf */
39 if (__builtin_expect(hx<0, 0))
40 return (x-x)/(x-x); /* log(-#) = NaN */
41 k -= 25; x *= two25; /* subnormal number, scale up x */
42 GET_FLOAT_WORD(hx,x);
43 }
44 if (__builtin_expect(hx >= 0x7f800000, 0)) return x+x;
45 k += (hx>>23)-127;
46 i = ((uint32_t)k&0x80000000)>>31;
47 hx = (hx&0x007fffff)|((0x7f-i)<<23);
48 y = (float)(k+i);
49 if (FIX_INT_FP_CONVERT_ZERO && y == 0.0f)
50 y = 0.0f;
51 SET_FLOAT_WORD(x,hx);
52 z = y*log10_2lo + ivln10*__ieee754_logf(x);
53 return z+y*log10_2hi;
54}
55libm_alias_finite (__ieee754_log10f, __log10f)
56