1 // SPDX-License-Identifier: GPL-2.0 1
2 /*
3 * Copyright (C) 2003 Bernardo Innocenti <bern
4 *
5 * Based on former do_div() implementation fro
6 * Copyright (C) 1999 Hewlett-Packard Co
7 * Copyright (C) 1999 David Mosberger-Tan
8 *
9 *
10 * Generic C version of 64bit/32bit division a
11 * 64bit result and 32bit remainder.
12 *
13 * The fast case for (n>>32 == 0) is handled i
14 *
15 * Code generated for this function might be v
16 * for some CPUs. __div64_32() can be overridd
17 * assembly versions such as arch/ppc/lib/div6
18 * or by defining a preprocessor macro in arch
19 */
20
21 #include <linux/bitops.h>
22 #include <linux/export.h>
23 #include <linux/math.h>
24 #include <linux/math64.h>
25 #include <linux/minmax.h>
26 #include <linux/log2.h>
27
28 /* Not needed on 64bit architectures */
29 #if BITS_PER_LONG == 32
30
31 #ifndef __div64_32
32 uint32_t __attribute__((weak)) __div64_32(uint
33 {
34 uint64_t rem = *n;
35 uint64_t b = base;
36 uint64_t res, d = 1;
37 uint32_t high = rem >> 32;
38
39 /* Reduce the thing a bit first */
40 res = 0;
41 if (high >= base) {
42 high /= base;
43 res = (uint64_t) high << 32;
44 rem -= (uint64_t) (high*base)
45 }
46
47 while ((int64_t)b > 0 && b < rem) {
48 b = b+b;
49 d = d+d;
50 }
51
52 do {
53 if (rem >= b) {
54 rem -= b;
55 res += d;
56 }
57 b >>= 1;
58 d >>= 1;
59 } while (d);
60
61 *n = res;
62 return rem;
63 }
64 EXPORT_SYMBOL(__div64_32);
65 #endif
66
67 #ifndef div_s64_rem
68 s64 div_s64_rem(s64 dividend, s32 divisor, s32
69 {
70 u64 quotient;
71
72 if (dividend < 0) {
73 quotient = div_u64_rem(-divide
74 *remainder = -*remainder;
75 if (divisor > 0)
76 quotient = -quotient;
77 } else {
78 quotient = div_u64_rem(dividen
79 if (divisor < 0)
80 quotient = -quotient;
81 }
82 return quotient;
83 }
84 EXPORT_SYMBOL(div_s64_rem);
85 #endif
86
87 /*
88 * div64_u64_rem - unsigned 64bit divide with
89 * @dividend: 64bit dividend
90 * @divisor: 64bit divisor
91 * @remainder: 64bit remainder
92 *
93 * This implementation is a comparable to algo
94 * But this operation, which includes math for
95 * is kept distinct to avoid slowing down the
96 * systems.
97 */
98 #ifndef div64_u64_rem
99 u64 div64_u64_rem(u64 dividend, u64 divisor, u
100 {
101 u32 high = divisor >> 32;
102 u64 quot;
103
104 if (high == 0) {
105 u32 rem32;
106 quot = div_u64_rem(dividend, d
107 *remainder = rem32;
108 } else {
109 int n = fls(high);
110 quot = div_u64(dividend >> n,
111
112 if (quot != 0)
113 quot--;
114
115 *remainder = dividend - quot *
116 if (*remainder >= divisor) {
117 quot++;
118 *remainder -= divisor;
119 }
120 }
121
122 return quot;
123 }
124 EXPORT_SYMBOL(div64_u64_rem);
125 #endif
126
127 /*
128 * div64_u64 - unsigned 64bit divide with 64bi
129 * @dividend: 64bit dividend
130 * @divisor: 64bit divisor
131 *
132 * This implementation is a modified version o
133 * by the book 'Hacker's Delight'. The origin
134 * can be found here and is available for use
135 *
136 * 'http://www.hackersdelight.org/hdcodetxt/di
137 */
138 #ifndef div64_u64
139 u64 div64_u64(u64 dividend, u64 divisor)
140 {
141 u32 high = divisor >> 32;
142 u64 quot;
143
144 if (high == 0) {
145 quot = div_u64(dividend, divis
146 } else {
147 int n = fls(high);
148 quot = div_u64(dividend >> n,
149
150 if (quot != 0)
151 quot--;
152 if ((dividend - quot * divisor
153 quot++;
154 }
155
156 return quot;
157 }
158 EXPORT_SYMBOL(div64_u64);
159 #endif
160
161 #ifndef div64_s64
162 s64 div64_s64(s64 dividend, s64 divisor)
163 {
164 s64 quot, t;
165
166 quot = div64_u64(abs(dividend), abs(di
167 t = (dividend ^ divisor) >> 63;
168
169 return (quot ^ t) - t;
170 }
171 EXPORT_SYMBOL(div64_s64);
172 #endif
173
174 #endif /* BITS_PER_LONG == 32 */
175
176 /*
177 * Iterative div/mod for use when dividend is
178 * bigger than divisor.
179 */
180 u32 iter_div_u64_rem(u64 dividend, u32 divisor
181 {
182 return __iter_div_u64_rem(dividend, di
183 }
184 EXPORT_SYMBOL(iter_div_u64_rem);
185
186 #ifndef mul_u64_u64_div_u64
187 u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c)
188 {
189 if (ilog2(a) + ilog2(b) <= 62)
190 return div64_u64(a * b, c);
191
192 #if defined(__SIZEOF_INT128__)
193
194 /* native 64x64=128 bits multiplicatio
195 u128 prod = (u128)a * b;
196 u64 n_lo = prod, n_hi = prod >> 64;
197
198 #else
199
200 /* perform a 64x64=128 bits multiplica
201 u32 a_lo = a, a_hi = a >> 32, b_lo = b
202 u64 x, y, z;
203
204 x = (u64)a_lo * b_lo;
205 y = (u64)a_lo * b_hi + (u32)(x >> 32);
206 z = (u64)a_hi * b_hi + (u32)(y >> 32);
207 y = (u64)a_hi * b_lo + (u32)y;
208 z += (u32)(y >> 32);
209 x = (y << 32) + (u32)x;
210
211 u64 n_lo = x, n_hi = z;
212
213 #endif
214
215 /* make sure c is not zero, trigger ex
216 #pragma GCC diagnostic push
217 #pragma GCC diagnostic ignored "-Wdiv-by-zero"
218 if (unlikely(c == 0))
219 return 1/0;
220 #pragma GCC diagnostic pop
221
222 int shift = __builtin_ctzll(c);
223
224 /* try reducing the fraction in case t
225 if ((n_hi >> shift) == 0) {
226 u64 n = shift ? (n_lo >> shift
227
228 return div64_u64(n, c >> shift
229 /*
230 * The remainder value if need
231 * res = div64_u64_rem(n, c
232 * rem = (rem << shift) + (n
233 */
234 }
235
236 if (n_hi >= c) {
237 /* overflow: result is unrepre
238 return -1;
239 }
240
241 /* Do the full 128 by 64 bits division
242
243 shift = __builtin_clzll(c);
244 c <<= shift;
245
246 int p = 64 + shift;
247 u64 res = 0;
248 bool carry;
249
250 do {
251 carry = n_hi >> 63;
252 shift = carry ? 1 : __builtin_
253 if (p < shift)
254 break;
255 p -= shift;
256 n_hi <<= shift;
257 n_hi |= n_lo >> (64 - shift);
258 n_lo <<= shift;
259 if (carry || (n_hi >= c)) {
260 n_hi -= c;
261 res |= 1ULL << p;
262 }
263 } while (n_hi);
264 /* The remainder value if needed would
265
266 return res;
267 }
268 EXPORT_SYMBOL(mul_u64_u64_div_u64);
269 #endif
270
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