Root/lib/div64.c

Source at commit b386be689295730688885552666ea40b2e639b14 created 8 years 11 months ago.
By Maarten ter Huurne, Revert "MIPS: JZ4740: reset: Initialize hibernate wakeup counters."
1/*
2 * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
3 *
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>
7 *
8 *
9 * Generic C version of 64bit/32bit division and modulo, with
10 * 64bit result and 32bit remainder.
11 *
12 * The fast case for (n>>32 == 0) is handled inline by do_div().
13 *
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.
17 */
18
19#include <linux/module.h>
20#include <linux/math64.h>
21
22/* Not needed on 64bit architectures */
23#if BITS_PER_LONG == 32
24
25uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
26{
27    uint64_t rem = *n;
28    uint64_t b = base;
29    uint64_t res, d = 1;
30    uint32_t high = rem >> 32;
31
32    /* Reduce the thing a bit first */
33    res = 0;
34    if (high >= base) {
35        high /= base;
36        res = (uint64_t) high << 32;
37        rem -= (uint64_t) (high*base) << 32;
38    }
39
40    while ((int64_t)b > 0 && b < rem) {
41        b = b+b;
42        d = d+d;
43    }
44
45    do {
46        if (rem >= b) {
47            rem -= b;
48            res += d;
49        }
50        b >>= 1;
51        d >>= 1;
52    } while (d);
53
54    *n = res;
55    return rem;
56}
57
58EXPORT_SYMBOL(__div64_32);
59
60#ifndef div_s64_rem
61s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
62{
63    u64 quotient;
64
65    if (dividend < 0) {
66        quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
67        *remainder = -*remainder;
68        if (divisor > 0)
69            quotient = -quotient;
70    } else {
71        quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
72        if (divisor < 0)
73            quotient = -quotient;
74    }
75    return quotient;
76}
77EXPORT_SYMBOL(div_s64_rem);
78#endif
79
80/**
81 * div64_u64 - unsigned 64bit divide with 64bit divisor
82 * @dividend: 64bit dividend
83 * @divisor: 64bit divisor
84 *
85 * This implementation is a modified version of the algorithm proposed
86 * by the book 'Hacker's Delight'. The original source and full proof
87 * can be found here and is available for use without restriction.
88 *
89 * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c'
90 */
91#ifndef div64_u64
92u64 div64_u64(u64 dividend, u64 divisor)
93{
94    u32 high = divisor >> 32;
95    u64 quot;
96
97    if (high == 0) {
98        quot = div_u64(dividend, divisor);
99    } else {
100        int n = 1 + fls(high);
101        quot = div_u64(dividend >> n, divisor >> n);
102
103        if (quot != 0)
104            quot--;
105        if ((dividend - quot * divisor) >= divisor)
106            quot++;
107    }
108
109    return quot;
110}
111EXPORT_SYMBOL(div64_u64);
112#endif
113
114/**
115 * div64_s64 - signed 64bit divide with 64bit divisor
116 * @dividend: 64bit dividend
117 * @divisor: 64bit divisor
118 */
119#ifndef div64_s64
120s64 div64_s64(s64 dividend, s64 divisor)
121{
122    s64 quot, t;
123
124    quot = div64_u64(abs64(dividend), abs64(divisor));
125    t = (dividend ^ divisor) >> 63;
126
127    return (quot ^ t) - t;
128}
129EXPORT_SYMBOL(div64_s64);
130#endif
131
132#endif /* BITS_PER_LONG == 32 */
133
134/*
135 * Iterative div/mod for use when dividend is not expected to be much
136 * bigger than divisor.
137 */
138u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
139{
140    return __iter_div_u64_rem(dividend, divisor, remainder);
141}
142EXPORT_SYMBOL(iter_div_u64_rem);
143

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