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/hdcodetxt/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);