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e_log2.c (226376) e_log2.c (251024)
1
2/* @(#)e_log10.c 1.3 95/01/18 */
3/*
4 * ====================================================
5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 *
7 * Developed at SunSoft, a Sun Microsystems, Inc. business.
8 * Permission to use, copy, modify, and distribute this
9 * software is freely granted, provided that this notice
10 * is preserved.
11 * ====================================================
12 */
13
14#include <sys/cdefs.h>
1
2/* @(#)e_log10.c 1.3 95/01/18 */
3/*
4 * ====================================================
5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 *
7 * Developed at SunSoft, a Sun Microsystems, Inc. business.
8 * Permission to use, copy, modify, and distribute this
9 * software is freely granted, provided that this notice
10 * is preserved.
11 * ====================================================
12 */
13
14#include <sys/cdefs.h>
15__FBSDID("$FreeBSD: head/lib/msun/src/e_log2.c 226376 2011-10-15 05:23:28Z das $");
15__FBSDID("$FreeBSD: head/lib/msun/src/e_log2.c 251024 2013-05-27 08:50:10Z das $");
16
17/*
18 * Return the base 2 logarithm of x. See e_log.c and k_log.h for most
19 * comments.
20 *
21 * This reduces x to {k, 1+f} exactly as in e_log.c, then calls the kernel,
22 * then does the combining and scaling steps
23 * log2(x) = (f - 0.5*f*f + k_log1p(f)) / ln2 + k

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29#include "k_log.h"
30
31static const double
32two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
33ivln2hi = 1.44269504072144627571e+00, /* 0x3ff71547, 0x65200000 */
34ivln2lo = 1.67517131648865118353e-10; /* 0x3de705fc, 0x2eefa200 */
35
36static const double zero = 0.0;
16
17/*
18 * Return the base 2 logarithm of x. See e_log.c and k_log.h for most
19 * comments.
20 *
21 * This reduces x to {k, 1+f} exactly as in e_log.c, then calls the kernel,
22 * then does the combining and scaling steps
23 * log2(x) = (f - 0.5*f*f + k_log1p(f)) / ln2 + k

--- 5 unchanged lines hidden (view full) ---

29#include "k_log.h"
30
31static const double
32two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
33ivln2hi = 1.44269504072144627571e+00, /* 0x3ff71547, 0x65200000 */
34ivln2lo = 1.67517131648865118353e-10; /* 0x3de705fc, 0x2eefa200 */
35
36static const double zero = 0.0;
37static volatile double vzero = 0.0;
37
38double
39__ieee754_log2(double x)
40{
41 double f,hfsq,hi,lo,r,val_hi,val_lo,w,y;
42 int32_t i,k,hx;
43 u_int32_t lx;
44
45 EXTRACT_WORDS(hx,lx,x);
46
47 k=0;
48 if (hx < 0x00100000) { /* x < 2**-1022 */
49 if (((hx&0x7fffffff)|lx)==0)
38
39double
40__ieee754_log2(double x)
41{
42 double f,hfsq,hi,lo,r,val_hi,val_lo,w,y;
43 int32_t i,k,hx;
44 u_int32_t lx;
45
46 EXTRACT_WORDS(hx,lx,x);
47
48 k=0;
49 if (hx < 0x00100000) { /* x < 2**-1022 */
50 if (((hx&0x7fffffff)|lx)==0)
50 return -two54/zero; /* log(+-0)=-inf */
51 return -two54/vzero; /* log(+-0)=-inf */
51 if (hx<0) return (x-x)/zero; /* log(-#) = NaN */
52 k -= 54; x *= two54; /* subnormal number, scale up x */
53 GET_HIGH_WORD(hx,x);
54 }
55 if (hx >= 0x7ff00000) return x+x;
56 if (hx == 0x3ff00000 && lx == 0)
57 return zero; /* log(1) = +0 */
58 k += (hx>>20)-1023;

--- 52 unchanged lines hidden --- 		52 if (hx<0) return (x-x)/zero; /* log(-#) = NaN */
53 k -= 54; x *= two54; /* subnormal number, scale up x */
54 GET_HIGH_WORD(hx,x);
55 }
56 if (hx >= 0x7ff00000) return x+x;
57 if (hx == 0x3ff00000 && lx == 0)
58 return zero; /* log(1) = +0 */
59 k += (hx>>20)-1023;

--- 52 unchanged lines hidden ---