1/* Copyright (C) 1997-2024 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library. If not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <math.h>
19#include <math_private.h>
20#include "mathimpl.h"
21#include <libm-alias-finite.h>
22
23#ifndef SUFF
24#define SUFF
25#endif
26#ifndef float_type
27#define float_type double
28#endif
29
30#define CONCATX(a,b) __CONCAT(a,b)
31#define s(name) CONCATX(name,SUFF)
32#define m81(func) __m81_u(s(func))
33
34float_type
35s(__ieee754_pow) (float_type x, float_type y)
36{
37 float_type z;
38 float_type ax;
39 unsigned long x_cond, y_cond;
40
41 y_cond = __m81_test (val: y);
42 if (y_cond & __M81_COND_ZERO)
43 return 1.0;
44 if (y_cond & __M81_COND_NAN)
45 return x == 1.0 ? x : x + y;
46
47 x_cond = __m81_test (val: x);
48 if (x_cond & __M81_COND_NAN)
49 return x + y;
50
51 if (y_cond & __M81_COND_INF)
52 {
53 ax = s(fabs) (x: x);
54 if (ax == 1.0)
55 return ax;
56 if (ax > 1.0)
57 return y_cond & __M81_COND_NEG ? 0 : y;
58 else
59 return y_cond & __M81_COND_NEG ? -y : 0;
60 }
61
62 if (s(fabs) (x: y) == 1.0)
63 return y_cond & __M81_COND_NEG ? 1 / x : x;
64
65 if (y == 2)
66 return x * x;
67 if (y == 0.5 && !(x_cond & __M81_COND_NEG))
68 return m81(sqrt) (x: x);
69
70 if (x == 10.0)
71 {
72 __asm ("ftentox%.x %1, %0" : "=f" (z) : "f" (y));
73 return z;
74 }
75 if (x == 2.0)
76 {
77 __asm ("ftwotox%.x %1, %0" : "=f" (z) : "f" (y));
78 return z;
79 }
80
81 ax = s(fabs) (x: x);
82 if (x_cond & (__M81_COND_INF | __M81_COND_ZERO) || ax == 1.0)
83 {
84 z = ax;
85 if (y_cond & __M81_COND_NEG)
86 z = 1 / z;
87 if (x_cond & __M81_COND_NEG)
88 {
89 if (y != m81(__rint) (mathop_x: y))
90 {
91 if (x == -1)
92 z = (z - z) / (z - z);
93 }
94 else
95 goto maybe_negate;
96 }
97 return z;
98 }
99
100 if (x_cond & __M81_COND_NEG)
101 {
102 if (y == m81(__rint) (mathop_x: y))
103 {
104 z = m81(__ieee754_exp) (mathop_x: y * m81(__ieee754_log) (mathop_x: -x));
105 maybe_negate:
106 /* We always use the long double format, since y is already in
107 this format and rounding won't change the result. */
108 {
109 int32_t exponent;
110 uint32_t i0, i1;
111 GET_LDOUBLE_WORDS (exponent, i0, i1, y);
112 exponent = (exponent & 0x7fff) - 0x3fff;
113 if (exponent <= 31
114 ? i0 & (1 << (31 - exponent))
115 : (exponent <= 63
116 && i1 & (1 << (63 - exponent))))
117 z = -z;
118 }
119 }
120 else
121 z = (y - y) / (y - y);
122 }
123 else
124 z = m81(__ieee754_exp) (mathop_x: y * m81(__ieee754_log) (mathop_x: x));
125 return z;
126}
127libm_alias_finite (s(__ieee754_pow), s (__pow))
128

source code of glibc/sysdeps/m68k/m680x0/fpu/e_pow.c