1/* e_log10f.c -- float version of e_log10.c.
2 */
3
4/*
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 *
8 * Developed at SunPro, a Sun Microsystems, Inc. business.
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
11 * is preserved.
12 * ====================================================
13 */
14
15#include <math.h>
16#include <math_private.h>
17#include <fix-int-fp-convert-zero.h>
18#include <libm-alias-finite.h>
19
20static const float
21two25 = 3.3554432000e+07, /* 0x4c000000 */
22ivln10 = 4.3429449201e-01, /* 0x3ede5bd9 */
23log10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */
24log10_2lo = 7.9034151668e-07; /* 0x355427db */
25
26float
27__ieee754_log10f(float x)
28{
29 float y,z;
30 int32_t i,k,hx;
31
32 GET_FLOAT_WORD(hx,x);
33
34 k=0;
35 if (hx < 0x00800000) { /* x < 2**-126 */
36 if (__builtin_expect((hx&0x7fffffff)==0, 0))
37 return -two25/fabsf (x); /* log(+-0)=-inf */
38 if (__builtin_expect(hx<0, 0))
39 return (x-x)/(x-x); /* log(-#) = NaN */
40 k -= 25; x *= two25; /* subnormal number, scale up x */
41 GET_FLOAT_WORD(hx,x);
42 }
43 if (__builtin_expect(hx >= 0x7f800000, 0)) return x+x;
44 k += (hx>>23)-127;
45 i = ((uint32_t)k&0x80000000)>>31;
46 hx = (hx&0x007fffff)|((0x7f-i)<<23);
47 y = (float)(k+i);
48 if (FIX_INT_FP_CONVERT_ZERO && y == 0.0f)
49 y = 0.0f;
50 SET_FLOAT_WORD(x,hx);
51 z = y*log10_2lo + ivln10*__ieee754_logf(x);
52 return z+y*log10_2hi;
53}
54libm_alias_finite (__ieee754_log10f, __log10f)
55