1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
|
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
*
* Based on former do_div() implementation from asm-parisc/div64.h:
* Copyright (C) 1999 Hewlett-Packard Co
* Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
*
*
* Generic C version of 64bit/32bit division and modulo, with
* 64bit result and 32bit remainder.
*
* The fast case for (n>>32 == 0) is handled inline by do_div().
*
* Code generated for this function might be very inefficient
* for some CPUs. __div64_32() can be overridden by linking arch-specific
* assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S
* or by defining a preprocessor macro in arch/include/asm/div64.h.
*/
#include <linux/bitops.h>
#include <linux/export.h>
#include <linux/math.h>
#include <linux/math64.h>
#include <linux/log2.h>
/* Not needed on 64bit architectures */
#if BITS_PER_LONG == 32
#ifndef __div64_32
uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
{
uint64_t rem = *n;
uint64_t b = base;
uint64_t res, d = 1;
uint32_t high = rem >> 32;
/* Reduce the thing a bit first */
res = 0;
if (high >= base) {
high /= base;
res = (uint64_t) high << 32;
rem -= (uint64_t) (high*base) << 32;
}
while ((int64_t)b > 0 && b < rem) {
b = b+b;
d = d+d;
}
do {
if (rem >= b) {
rem -= b;
res += d;
}
b >>= 1;
d >>= 1;
} while (d);
*n = res;
return rem;
}
EXPORT_SYMBOL(__div64_32);
#endif
#ifndef div_s64_rem
s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
{
u64 quotient;
if (dividend < 0) {
quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
*remainder = -*remainder;
if (divisor > 0)
quotient = -quotient;
} else {
quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
if (divisor < 0)
quotient = -quotient;
}
return quotient;
}
EXPORT_SYMBOL(div_s64_rem);
#endif
/*
* div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
* @dividend: 64bit dividend
* @divisor: 64bit divisor
* @remainder: 64bit remainder
*
* This implementation is a comparable to algorithm used by div64_u64.
* But this operation, which includes math for calculating the remainder,
* is kept distinct to avoid slowing down the div64_u64 operation on 32bit
* systems.
*/
#ifndef div64_u64_rem
u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
{
u32 high = divisor >> 32;
u64 quot;
if (high == 0) {
u32 rem32;
quot = div_u64_rem(dividend, divisor, &rem32);
*remainder = rem32;
} else {
int n = fls(high);
quot = div_u64(dividend >> n, divisor >> n);
if (quot != 0)
quot--;
*remainder = dividend - quot * divisor;
if (*remainder >= divisor) {
quot++;
*remainder -= divisor;
}
}
return quot;
}
EXPORT_SYMBOL(div64_u64_rem);
#endif
/*
* div64_u64 - unsigned 64bit divide with 64bit divisor
* @dividend: 64bit dividend
* @divisor: 64bit divisor
*
* This implementation is a modified version of the algorithm proposed
* by the book 'Hacker's Delight'. The original source and full proof
* can be found here and is available for use without restriction.
*
* 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
*/
#ifndef div64_u64
u64 div64_u64(u64 dividend, u64 divisor)
{
u32 high = divisor >> 32;
u64 quot;
if (high == 0) {
quot = div_u64(dividend, divisor);
} else {
int n = fls(high);
quot = div_u64(dividend >> n, divisor >> n);
if (quot != 0)
quot--;
if ((dividend - quot * divisor) >= divisor)
quot++;
}
return quot;
}
EXPORT_SYMBOL(div64_u64);
#endif
#ifndef div64_s64
s64 div64_s64(s64 dividend, s64 divisor)
{
s64 quot, t;
quot = div64_u64(abs(dividend), abs(divisor));
t = (dividend ^ divisor) >> 63;
return (quot ^ t) - t;
}
EXPORT_SYMBOL(div64_s64);
#endif
#endif /* BITS_PER_LONG == 32 */
/*
* Iterative div/mod for use when dividend is not expected to be much
* bigger than divisor.
*/
u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
{
return __iter_div_u64_rem(dividend, divisor, remainder);
}
EXPORT_SYMBOL(iter_div_u64_rem);
#ifndef mul_u64_u64_div_u64
u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c)
{
u64 res = 0, div, rem;
int shift;
/* can a * b overflow ? */
if (ilog2(a) + ilog2(b) > 62) {
/*
* (b * a) / c is equal to
*
* (b / c) * a +
* (b % c) * a / c
*
* if nothing overflows. Can the 1st multiplication
* overflow? Yes, but we do not care: this can only
* happen if the end result can't fit in u64 anyway.
*
* So the code below does
*
* res = (b / c) * a;
* b = b % c;
*/
div = div64_u64_rem(b, c, &rem);
res = div * a;
b = rem;
shift = ilog2(a) + ilog2(b) - 62;
if (shift > 0) {
/* drop precision */
b >>= shift;
c >>= shift;
if (!c)
return res;
}
}
return res + div64_u64(a * b, c);
}
EXPORT_SYMBOL(mul_u64_u64_div_u64);
#endif
|
