| 1 | |
| 2 | * Copyright (C) 2003 Bernardo Innocenti <[email protected]>
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| 3 | *
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| 4 | * Based on former do_div() implementation from asm-parisc/div64.h:
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| 5 | * Copyright (C) 1999 Hewlett-Packard Co
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| 6 | * Copyright (C) 1999 David Mosberger-Tang <[email protected]>
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| 7 | *
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| 8 | *
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| 9 | * Generic C version of 64bit/32bit division and modulo, with
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| 10 | * 64bit result and 32bit remainder.
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| 11 | *
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| 12 | * The fast case for (n>>32 == 0) is handled inline by do_div().
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| 13 | *
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| 14 | * Code generated for this function might be very inefficient
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| 15 | * for some CPUs. __div64_32() can be overridden by linking arch-specific
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| 16 | * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S.
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| 17 |
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| 18 |
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| 19 | #include <linux/export.h>
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| 20 | #include <linux/kernel.h>
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| 21 | #include <linux/math64.h>
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| 22 |
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| 23 |
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| 24 | #if BITS_PER_LONG == 32
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| 25 |
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| 26 | uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
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| 27 | {
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| 28 | uint64_t rem = *n;
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| 29 | uint64_t b = base;
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| 30 | uint64_t res, d = 1;
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| 31 | uint32_t high = rem >> 32;
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| 32 |
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| 33 |
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| 34 | res = 0;
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| 35 | if (high >= base) {
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| 36 | high /= base;
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| 37 | res = (uint64_t) high << 32;
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| 38 | rem -= (uint64_t) (high*base) << 32;
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| 39 | }
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| 40 |
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| 41 | while ((int64_t)b > 0 && b < rem) {
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| 42 | b = b+b;
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| 43 | d = d+d;
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| 44 | }
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| 45 |
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| 46 | do {
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| 47 | if (rem >= b) {
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| 48 | rem -= b;
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| 49 | res += d;
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| 50 | }
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| 51 | b >>= 1;
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| 52 | d >>= 1;
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| 53 | } while (d);
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| 54 |
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| 55 | *n = res;
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| 56 | return rem;
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| 57 | }
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| 58 |
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| 59 | EXPORT_SYMBOL(__div64_32);
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| 60 |
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| 61 | #ifndef div_s64_rem
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| 62 | s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
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| 63 | {
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| 64 | u64 quotient;
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| 65 |
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| 66 | if (dividend < 0) {
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| 67 | quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
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| 68 | *remainder = -*remainder;
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| 69 | if (divisor > 0)
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| 70 | quotient = -quotient;
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| 71 | } else {
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| 72 | quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
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| 73 | if (divisor < 0)
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| 74 | quotient = -quotient;
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| 75 | }
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| 76 | return quotient;
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| 77 | }
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| 78 | EXPORT_SYMBOL(div_s64_rem);
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| 79 | #endif
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| 80 |
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| 81 | |
| 82 | * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
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| 83 | * @dividend: 64bit dividend
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| 84 | * @divisor: 64bit divisor
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| 85 | * @remainder: 64bit remainder
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| 86 | *
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| 87 | * This implementation is a comparable to algorithm used by div64_u64.
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| 88 | * But this operation, which includes math for calculating the remainder,
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| 89 | * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
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| 90 | * systems.
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| 91 |
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| 92 | #ifndef div64_u64_rem
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| 93 | u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
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| 94 | {
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| 95 | u32 high = divisor >> 32;
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| 96 | u64 quot;
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| 97 |
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| 98 | if (high == 0) {
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| 99 | u32 rem32;
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| 100 | quot = div_u64_rem(dividend, divisor, &rem32);
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| 101 | *remainder = rem32;
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| 102 | } else {
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| 103 | int n = 1 + fls(high);
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| 104 | quot = div_u64(dividend >> n, divisor >> n);
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| 105 |
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| 106 | if (quot != 0)
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| 107 | quot--;
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| 108 |
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| 109 | *remainder = dividend - quot * divisor;
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| 110 | if (*remainder >= divisor) {
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| 111 | quot++;
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| 112 | *remainder -= divisor;
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| 113 | }
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| 114 | }
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| 115 |
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| 116 | return quot;
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| 117 | }
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| 118 | EXPORT_SYMBOL(div64_u64_rem);
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| 119 | #endif
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| 120 |
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| 121 | |
| 122 | * div64_u64 - unsigned 64bit divide with 64bit divisor
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| 123 | * @dividend: 64bit dividend
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| 124 | * @divisor: 64bit divisor
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| 125 | *
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| 126 | * This implementation is a modified version of the algorithm proposed
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| 127 | * by the book 'Hacker's Delight'. The original source and full proof
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| 128 | * can be found here and is available for use without restriction.
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| 129 | *
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| 130 | * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c.txt'
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| 131 |
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| 132 | #ifndef div64_u64
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| 133 | u64 div64_u64(u64 dividend, u64 divisor)
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| 134 | {
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| 135 | u32 high = divisor >> 32;
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| 136 | u64 quot;
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| 137 |
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| 138 | if (high == 0) {
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| 139 | quot = div_u64(dividend, divisor);
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| 140 | } else {
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| 141 | int n = 1 + fls(high);
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| 142 | quot = div_u64(dividend >> n, divisor >> n);
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| 143 |
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| 144 | if (quot != 0)
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| 145 | quot--;
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| 146 | if ((dividend - quot * divisor) >= divisor)
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| 147 | quot++;
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| 148 | }
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| 149 |
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| 150 | return quot;
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| 151 | }
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| 152 | EXPORT_SYMBOL(div64_u64);
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| 153 | #endif
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| 154 |
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| 155 | |
| 156 | * div64_s64 - signed 64bit divide with 64bit divisor
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| 157 | * @dividend: 64bit dividend
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| 158 | * @divisor: 64bit divisor
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| 159 |
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| 160 | #ifndef div64_s64
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| 161 | s64 div64_s64(s64 dividend, s64 divisor)
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| 162 | {
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| 163 | s64 quot, t;
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| 164 |
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| 165 | quot = div64_u64(abs64(dividend), abs64(divisor));
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| 166 | t = (dividend ^ divisor) >> 63;
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| 167 |
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| 168 | return (quot ^ t) - t;
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| 169 | }
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| 170 | EXPORT_SYMBOL(div64_s64);
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| 171 | #endif
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| 172 |
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| 173 | #endif
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| 174 |
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| 175 | |
| 176 | * Iterative div/mod for use when dividend is not expected to be much
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| 177 | * bigger than divisor.
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| 178 |
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| 179 | u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
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| 180 | {
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| 181 | return __iter_div_u64_rem(dividend, divisor, remainder);
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| 182 | }
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| 183 | EXPORT_SYMBOL(iter_div_u64_rem);
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