1 /*
2 * Copyright (c) 2008-2020 Stefan Krah. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28
29 #ifndef LIBMPDEC_BITS_H_
30 #define LIBMPDEC_BITS_H_
31
32
33 #include "mpdecimal.h"
34
35
36 /* Check if n is a power of 2. */
37 static inline int
38 ispower2(mpd_size_t n)
39 {
40 return n != 0 && (n & (n-1)) == 0;
41 }
42
43 #if defined(ANSI)
44 /*
45 * Return the most significant bit position of n from 0 to 31 (63).
46 * Assumptions: n != 0.
47 */
48 static inline int
49 mpd_bsr(mpd_size_t n)
50 {
51 int pos = 0;
52 mpd_size_t tmp;
53
54 #ifdef CONFIG_64
55 tmp = n >> 32;
56 if (tmp != 0) { n = tmp; pos += 32; }
57 #endif
58 tmp = n >> 16;
59 if (tmp != 0) { n = tmp; pos += 16; }
60 tmp = n >> 8;
61 if (tmp != 0) { n = tmp; pos += 8; }
62 tmp = n >> 4;
63 if (tmp != 0) { n = tmp; pos += 4; }
64 tmp = n >> 2;
65 if (tmp != 0) { n = tmp; pos += 2; }
66 tmp = n >> 1;
67 if (tmp != 0) { n = tmp; pos += 1; }
68
69 return pos + (int)n - 1;
70 }
71
72 /*
73 * Return the least significant bit position of n from 0 to 31 (63).
74 * Assumptions: n != 0.
75 */
76 static inline int
77 mpd_bsf(mpd_size_t n)
78 {
79 int pos;
80
81 #ifdef CONFIG_64
82 pos = 63;
83 if (n & 0x00000000FFFFFFFFULL) { pos -= 32; } else { n >>= 32; }
84 if (n & 0x000000000000FFFFULL) { pos -= 16; } else { n >>= 16; }
85 if (n & 0x00000000000000FFULL) { pos -= 8; } else { n >>= 8; }
86 if (n & 0x000000000000000FULL) { pos -= 4; } else { n >>= 4; }
87 if (n & 0x0000000000000003ULL) { pos -= 2; } else { n >>= 2; }
88 if (n & 0x0000000000000001ULL) { pos -= 1; }
89 #else
90 pos = 31;
91 if (n & 0x000000000000FFFFUL) { pos -= 16; } else { n >>= 16; }
92 if (n & 0x00000000000000FFUL) { pos -= 8; } else { n >>= 8; }
93 if (n & 0x000000000000000FUL) { pos -= 4; } else { n >>= 4; }
94 if (n & 0x0000000000000003UL) { pos -= 2; } else { n >>= 2; }
95 if (n & 0x0000000000000001UL) { pos -= 1; }
96 #endif
97 return pos;
98 }
99 /* END ANSI */
100
101 #elif defined(ASM)
102 /*
103 * Bit scan reverse. Assumptions: a != 0.
104 */
105 static inline int
106 mpd_bsr(mpd_size_t a)
107 {
108 mpd_size_t retval;
109
110 __asm__ (
111 #ifdef CONFIG_64
112 "bsrq %1, %0\n\t"
113 #else
114 "bsr %1, %0\n\t"
115 #endif
116 :"=r" (retval)
117 :"r" (a)
118 :"cc"
119 );
120
121 return (int)retval;
122 }
123
124 /*
125 * Bit scan forward. Assumptions: a != 0.
126 */
127 static inline int
128 mpd_bsf(mpd_size_t a)
129 {
130 mpd_size_t retval;
131
132 __asm__ (
133 #ifdef CONFIG_64
134 "bsfq %1, %0\n\t"
135 #else
136 "bsf %1, %0\n\t"
137 #endif
138 :"=r" (retval)
139 :"r" (a)
140 :"cc"
141 );
142
143 return (int)retval;
144 }
145 /* END ASM */
146
147 #elif defined(MASM)
148 #include <intrin.h>
149 /*
150 * Bit scan reverse. Assumptions: a != 0.
151 */
152 static inline int __cdecl
153 mpd_bsr(mpd_size_t a)
154 {
155 unsigned long retval;
156
157 #ifdef CONFIG_64
158 _BitScanReverse64(&retval, a);
159 #else
160 _BitScanReverse(&retval, a);
161 #endif
162
163 return (int)retval;
164 }
165
166 /*
167 * Bit scan forward. Assumptions: a != 0.
168 */
169 static inline int __cdecl
170 mpd_bsf(mpd_size_t a)
171 {
172 unsigned long retval;
173
174 #ifdef CONFIG_64
175 _BitScanForward64(&retval, a);
176 #else
177 _BitScanForward(&retval, a);
178 #endif
179
180 return (int)retval;
181 }
182 /* END MASM (_MSC_VER) */
183 #else
184 #error "missing preprocessor definitions"
185 #endif /* BSR/BSF */
186
187
188 #endif /* LIBMPDEC_BITS_H_ */