d098efe9225ca88a1cd625e97c00a7b80b93cb99
[reactos.git] / reactos / lib / crt / math / pow.c
1 /* Math functions for i387.
2 Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by John C. Bowman <bowman@ipp-garching.mpg.de>, 1995.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Library General Public License as
8 published by the Free Software Foundation; either version 2 of the
9 License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Library General Public License for more details.
15
16 You should have received a copy of the GNU Library General Public
17 License along with the GNU C Library; see the file COPYING.LIB. If not,
18 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
20
21 #include <math.h>
22
23 double pow (double __x, double __y);
24
25 double __log2 (double __x);
26
27 double __log2 (double __x)
28 {
29 register double __value;
30 #ifdef __GNUC__
31 __asm __volatile__
32 ("fld1\n\t"
33 "fxch\n\t"
34 "fyl2x"
35 : "=t" (__value) : "0" (__x));
36 #else
37 //__value = linkme_log2(__x);
38 __value = 0;
39 #endif /*__GNUC__*/
40 return __value;
41 }
42
43 /*
44 * @implemented
45 */
46 double pow (double __x, double __y)
47 {
48 register double __value;
49 #ifdef __GNUC__
50 register double __exponent;
51 long __p = (long) __y;
52
53 if (__x == 0.0 && __y > 0.0)
54 return 0.0;
55 if (__y == (double) __p)
56 {
57 double __r = 1.0;
58 if (__p == 0)
59 return 1.0;
60 if (__p < 0)
61 {
62 __p = -__p;
63 __x = 1.0 / __x;
64 }
65 while (1)
66 {
67 if (__p & 1)
68 __r *= __x;
69 __p >>= 1;
70 if (__p == 0)
71 return __r;
72 __x *= __x;
73 }
74 /* NOTREACHED */
75 }
76 __asm __volatile__
77 ("fmul %%st(1) # y * log2(x)\n\t"
78 "fst %%st(1)\n\t"
79 "frndint # int(y * log2(x))\n\t"
80 "fxch\n\t"
81 "fsub %%st(1) # fract(y * log2(x))\n\t"
82 "f2xm1 # 2^(fract(y * log2(x))) - 1\n\t"
83 : "=t" (__value), "=u" (__exponent) : "0" (__log2 (__x)), "1" (__y));
84 __value += 1.0;
85 __asm __volatile__
86 ("fscale"
87 : "=t" (__value) : "0" (__value), "u" (__exponent));
88 #else
89 __value = linkme_pow(__x, __y);
90 #endif /*__GNUC__*/
91 return __value;
92 }
93
94 long double powl (long double __x,long double __y)
95 {
96 return pow(__x,__y/2)*pow(__x,__y/2);
97 }