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2aa62f2b | 1 | \r |
2 | /* @(#)e_log.c 1.3 95/01/18 */\r | |
3 | /*\r | |
4 | * ====================================================\r | |
5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.\r | |
6 | *\r | |
7 | * Developed at SunSoft, a Sun Microsystems, Inc. business.\r | |
8 | * Permission to use, copy, modify, and distribute this\r | |
9 | * software is freely granted, provided that this notice\r | |
10 | * is preserved.\r | |
11 | * ====================================================\r | |
12 | */\r | |
13 | #include <LibConfig.h>\r | |
14 | #include <sys/EfiCdefs.h>\r | |
15 | #if defined(LIBM_SCCS) && !defined(lint)\r | |
16 | __RCSID("$NetBSD: e_log2.c,v 1.1 2005/07/21 12:55:58 christos Exp $");\r | |
17 | #endif\r | |
18 | \r | |
19 | #include "math.h"\r | |
20 | #include "math_private.h"\r | |
21 | \r | |
22 | #if defined(_MSC_VER) /* Handle Microsoft VC++ compiler specifics. */\r | |
23 | // potential divide by 0 -- near line 53, (x-x)/zero is on purpose\r | |
24 | #pragma warning ( disable : 4723 )\r | |
25 | #endif\r | |
26 | \r | |
27 | static const double\r | |
28 | ln2 = 0.6931471805599452862268,\r | |
29 | two54 = 1.80143985094819840000e+16, /* 43500000 00000000 */\r | |
30 | Lg1 = 6.666666666666735130e-01, /* 3FE55555 55555593 */\r | |
31 | Lg2 = 3.999999999940941908e-01, /* 3FD99999 9997FA04 */\r | |
32 | Lg3 = 2.857142874366239149e-01, /* 3FD24924 94229359 */\r | |
33 | Lg4 = 2.222219843214978396e-01, /* 3FCC71C5 1D8E78AF */\r | |
34 | Lg5 = 1.818357216161805012e-01, /* 3FC74664 96CB03DE */\r | |
35 | Lg6 = 1.531383769920937332e-01, /* 3FC39A09 D078C69F */\r | |
36 | Lg7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */\r | |
37 | \r | |
38 | static const double zero = 0.0;\r | |
39 | \r | |
40 | double\r | |
41 | __ieee754_log2(double x)\r | |
42 | {\r | |
43 | double hfsq,f,s,z,R,w,t1,t2,dk;\r | |
44 | int32_t k,hx,i,j;\r | |
45 | u_int32_t lx;\r | |
46 | \r | |
47 | EXTRACT_WORDS(hx,lx,x);\r | |
48 | \r | |
49 | k=0;\r | |
50 | if (hx < 0x00100000) { /* x < 2**-1022 */\r | |
51 | if (((hx&0x7fffffff)|lx)==0)\r | |
52 | return -two54/zero; /* log(+-0)=-inf */\r | |
53 | if (hx<0) return (x-x)/zero; /* log(-#) = NaN */\r | |
54 | k -= 54; x *= two54; /* subnormal number, scale up x */\r | |
55 | GET_HIGH_WORD(hx,x);\r | |
56 | }\r | |
57 | if (hx >= 0x7ff00000) return x+x;\r | |
58 | k += (hx>>20)-1023;\r | |
59 | hx &= 0x000fffff;\r | |
60 | i = (hx+0x95f64)&0x100000;\r | |
61 | SET_HIGH_WORD(x,hx|(i^0x3ff00000)); /* normalize x or x/2 */\r | |
62 | k += (i>>20);\r | |
63 | f = x-1.0;\r | |
64 | dk = (double)k;\r | |
65 | if((0x000fffff&(2+hx))<3) { /* |f| < 2**-20 */\r | |
66 | if (f==zero)\r | |
67 | return (dk);\r | |
68 | R = f*f*(0.5-0.33333333333333333*f);\r | |
69 | return (dk-(R-f)/ln2);\r | |
70 | }\r | |
71 | s = f/(2.0+f);\r | |
72 | z = s*s;\r | |
73 | i = hx-0x6147a;\r | |
74 | w = z*z;\r | |
75 | j = 0x6b851-hx;\r | |
76 | t1= w*(Lg2+w*(Lg4+w*Lg6));\r | |
77 | t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));\r | |
78 | i |= j;\r | |
79 | R = t2+t1;\r | |
80 | if(i>0) {\r | |
81 | hfsq=0.5*f*f;\r | |
82 | return (dk-(hfsq-s*(hfsq+R)-f)/ln2);\r | |
83 | } else\r | |
84 | return (dk-((s*(f-R))-f)/ln2);\r | |
85 | }\r |