2 * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
4 * Based on former do_div() implementation from asm-parisc/div64.h:
5 * Copyright (C) 1999 Hewlett-Packard Co
6 * Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
9 * Generic C version of 64bit/32bit division and modulo, with
10 * 64bit result and 32bit remainder.
12 * The fast case for (n>>32 == 0) is handled inline by do_div().
14 * Code generated for this function might be very inefficient
15 * for some CPUs. __div64_32() can be overridden by linking arch-specific
16 * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S.
19 #include <linux/export.h>
20 #include <linux/kernel.h>
21 #include <linux/math64.h>
23 /* Not needed on 64bit architectures */
24 #if BITS_PER_LONG == 32
26 uint32_t __attribute__((weak
)) __div64_32(uint64_t *n
, uint32_t base
)
31 uint32_t high
= rem
>> 32;
33 /* Reduce the thing a bit first */
37 res
= (uint64_t) high
<< 32;
38 rem
-= (uint64_t) (high
*base
) << 32;
41 while ((int64_t)b
> 0 && b
< rem
) {
59 EXPORT_SYMBOL(__div64_32
);
62 s64
div_s64_rem(s64 dividend
, s32 divisor
, s32
*remainder
)
67 quotient
= div_u64_rem(-dividend
, abs(divisor
), (u32
*)remainder
);
68 *remainder
= -*remainder
;
72 quotient
= div_u64_rem(dividend
, abs(divisor
), (u32
*)remainder
);
78 EXPORT_SYMBOL(div_s64_rem
);
82 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
83 * @dividend: 64bit dividend
84 * @divisor: 64bit divisor
85 * @remainder: 64bit remainder
87 * This implementation is a comparable to algorithm used by div64_u64.
88 * But this operation, which includes math for calculating the remainder,
89 * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
93 u64
div64_u64_rem(u64 dividend
, u64 divisor
, u64
*remainder
)
95 u32 high
= divisor
>> 32;
100 quot
= div_u64_rem(dividend
, divisor
, &rem32
);
103 int n
= 1 + fls(high
);
104 quot
= div_u64(dividend
>> n
, divisor
>> n
);
109 *remainder
= dividend
- quot
* divisor
;
110 if (*remainder
>= divisor
) {
112 *remainder
-= divisor
;
118 EXPORT_SYMBOL(div64_u64_rem
);
122 * div64_u64 - unsigned 64bit divide with 64bit divisor
123 * @dividend: 64bit dividend
124 * @divisor: 64bit divisor
126 * This implementation is a modified version of the algorithm proposed
127 * by the book 'Hacker's Delight'. The original source and full proof
128 * can be found here and is available for use without restriction.
130 * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c.txt'
133 u64
div64_u64(u64 dividend
, u64 divisor
)
135 u32 high
= divisor
>> 32;
139 quot
= div_u64(dividend
, divisor
);
141 int n
= 1 + fls(high
);
142 quot
= div_u64(dividend
>> n
, divisor
>> n
);
146 if ((dividend
- quot
* divisor
) >= divisor
)
152 EXPORT_SYMBOL(div64_u64
);
156 * div64_s64 - signed 64bit divide with 64bit divisor
157 * @dividend: 64bit dividend
158 * @divisor: 64bit divisor
161 s64
div64_s64(s64 dividend
, s64 divisor
)
165 quot
= div64_u64(abs64(dividend
), abs64(divisor
));
166 t
= (dividend
^ divisor
) >> 63;
168 return (quot
^ t
) - t
;
170 EXPORT_SYMBOL(div64_s64
);
173 #endif /* BITS_PER_LONG == 32 */
176 * Iterative div/mod for use when dividend is not expected to be much
177 * bigger than divisor.
179 u32
iter_div_u64_rem(u64 dividend
, u32 divisor
, u64
*remainder
)
181 return __iter_div_u64_rem(dividend
, divisor
, remainder
);
183 EXPORT_SYMBOL(iter_div_u64_rem
);
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