1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
5 * Based on former do_div() implementation from asm-parisc/div64.h:
6 * Copyright (C) 1999 Hewlett-Packard Co
7 * Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
10 * Generic C version of 64bit/32bit division and modulo, with
11 * 64bit result and 32bit remainder.
13 * The fast case for (n>>32 == 0) is handled inline by do_div().
15 * Code generated for this function might be very inefficient
16 * for some CPUs. __div64_32() can be overridden by linking arch-specific
17 * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S
18 * or by defining a preprocessor macro in arch/include/asm/div64.h.
21 #include <linux/export.h>
22 #include <linux/kernel.h>
23 #include <linux/math64.h>
25 /* Not needed on 64bit architectures */
26 #if BITS_PER_LONG == 32
29 uint32_t __attribute__((weak
)) __div64_32(uint64_t *n
, uint32_t base
)
34 uint32_t high
= rem
>> 32;
36 /* Reduce the thing a bit first */
40 res
= (uint64_t) high
<< 32;
41 rem
-= (uint64_t) (high
*base
) << 32;
44 while ((int64_t)b
> 0 && b
< rem
) {
61 EXPORT_SYMBOL(__div64_32
);
65 * div_s64_rem - signed 64bit divide with 64bit divisor and remainder
66 * @dividend: 64bit dividend
67 * @divisor: 64bit divisor
68 * @remainder: 64bit remainder
71 s64
div_s64_rem(s64 dividend
, s32 divisor
, s32
*remainder
)
76 quotient
= div_u64_rem(-dividend
, abs(divisor
), (u32
*)remainder
);
77 *remainder
= -*remainder
;
81 quotient
= div_u64_rem(dividend
, abs(divisor
), (u32
*)remainder
);
87 EXPORT_SYMBOL(div_s64_rem
);
91 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
92 * @dividend: 64bit dividend
93 * @divisor: 64bit divisor
94 * @remainder: 64bit remainder
96 * This implementation is a comparable to algorithm used by div64_u64.
97 * But this operation, which includes math for calculating the remainder,
98 * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
101 #ifndef div64_u64_rem
102 u64
div64_u64_rem(u64 dividend
, u64 divisor
, u64
*remainder
)
104 u32 high
= divisor
>> 32;
109 quot
= div_u64_rem(dividend
, divisor
, &rem32
);
113 quot
= div_u64(dividend
>> n
, divisor
>> n
);
118 *remainder
= dividend
- quot
* divisor
;
119 if (*remainder
>= divisor
) {
121 *remainder
-= divisor
;
127 EXPORT_SYMBOL(div64_u64_rem
);
131 * div64_u64 - unsigned 64bit divide with 64bit divisor
132 * @dividend: 64bit dividend
133 * @divisor: 64bit divisor
135 * This implementation is a modified version of the algorithm proposed
136 * by the book 'Hacker's Delight'. The original source and full proof
137 * can be found here and is available for use without restriction.
139 * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
142 u64
div64_u64(u64 dividend
, u64 divisor
)
144 u32 high
= divisor
>> 32;
148 quot
= div_u64(dividend
, divisor
);
151 quot
= div_u64(dividend
>> n
, divisor
>> n
);
155 if ((dividend
- quot
* divisor
) >= divisor
)
161 EXPORT_SYMBOL(div64_u64
);
165 * div64_s64 - signed 64bit divide with 64bit divisor
166 * @dividend: 64bit dividend
167 * @divisor: 64bit divisor
170 s64
div64_s64(s64 dividend
, s64 divisor
)
174 quot
= div64_u64(abs(dividend
), abs(divisor
));
175 t
= (dividend
^ divisor
) >> 63;
177 return (quot
^ t
) - t
;
179 EXPORT_SYMBOL(div64_s64
);
182 #endif /* BITS_PER_LONG == 32 */
185 * Iterative div/mod for use when dividend is not expected to be much
186 * bigger than divisor.
188 u32
iter_div_u64_rem(u64 dividend
, u32 divisor
, u64
*remainder
)
190 return __iter_div_u64_rem(dividend
, divisor
, remainder
);
192 EXPORT_SYMBOL(iter_div_u64_rem
);