Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 |
Nicolas Pitre | dce1eb9 | 2015-11-02 13:02:46 -0500 | [diff] [blame] | 16 | * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S |
| 17 | * or by defining a preprocessor macro in arch/include/asm/div64.h. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 18 | */ |
| 19 | |
Paul Gortmaker | 8bc3bcc | 2011-11-16 21:29:17 -0500 | [diff] [blame] | 20 | #include <linux/export.h> |
| 21 | #include <linux/kernel.h> |
Roman Zippel | 2418f4f | 2008-05-01 04:34:25 -0700 | [diff] [blame] | 22 | #include <linux/math64.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 23 | |
| 24 | /* Not needed on 64bit architectures */ |
| 25 | #if BITS_PER_LONG == 32 |
| 26 | |
Nicolas Pitre | dce1eb9 | 2015-11-02 13:02:46 -0500 | [diff] [blame] | 27 | #ifndef __div64_32 |
David S. Miller | cb8c181 | 2007-04-10 22:10:39 -0700 | [diff] [blame] | 28 | uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 29 | { |
| 30 | uint64_t rem = *n; |
| 31 | uint64_t b = base; |
| 32 | uint64_t res, d = 1; |
| 33 | uint32_t high = rem >> 32; |
| 34 | |
| 35 | /* Reduce the thing a bit first */ |
| 36 | res = 0; |
| 37 | if (high >= base) { |
| 38 | high /= base; |
| 39 | res = (uint64_t) high << 32; |
| 40 | rem -= (uint64_t) (high*base) << 32; |
| 41 | } |
| 42 | |
| 43 | while ((int64_t)b > 0 && b < rem) { |
| 44 | b = b+b; |
| 45 | d = d+d; |
| 46 | } |
| 47 | |
| 48 | do { |
| 49 | if (rem >= b) { |
| 50 | rem -= b; |
| 51 | res += d; |
| 52 | } |
| 53 | b >>= 1; |
| 54 | d >>= 1; |
| 55 | } while (d); |
| 56 | |
| 57 | *n = res; |
| 58 | return rem; |
| 59 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 60 | EXPORT_SYMBOL(__div64_32); |
Nicolas Pitre | dce1eb9 | 2015-11-02 13:02:46 -0500 | [diff] [blame] | 61 | #endif |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 62 | |
Roman Zippel | 2418f4f | 2008-05-01 04:34:25 -0700 | [diff] [blame] | 63 | #ifndef div_s64_rem |
| 64 | s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) |
| 65 | { |
| 66 | u64 quotient; |
| 67 | |
| 68 | if (dividend < 0) { |
| 69 | quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder); |
| 70 | *remainder = -*remainder; |
| 71 | if (divisor > 0) |
| 72 | quotient = -quotient; |
| 73 | } else { |
| 74 | quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder); |
| 75 | if (divisor < 0) |
| 76 | quotient = -quotient; |
| 77 | } |
| 78 | return quotient; |
| 79 | } |
| 80 | EXPORT_SYMBOL(div_s64_rem); |
| 81 | #endif |
| 82 | |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 83 | /** |
Mike Snitzer | eb18cba | 2013-08-20 15:05:17 -0400 | [diff] [blame] | 84 | * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder |
| 85 | * @dividend: 64bit dividend |
| 86 | * @divisor: 64bit divisor |
| 87 | * @remainder: 64bit remainder |
| 88 | * |
| 89 | * This implementation is a comparable to algorithm used by div64_u64. |
| 90 | * But this operation, which includes math for calculating the remainder, |
| 91 | * is kept distinct to avoid slowing down the div64_u64 operation on 32bit |
| 92 | * systems. |
| 93 | */ |
| 94 | #ifndef div64_u64_rem |
| 95 | u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder) |
| 96 | { |
| 97 | u32 high = divisor >> 32; |
| 98 | u64 quot; |
| 99 | |
| 100 | if (high == 0) { |
| 101 | u32 rem32; |
| 102 | quot = div_u64_rem(dividend, divisor, &rem32); |
| 103 | *remainder = rem32; |
| 104 | } else { |
Stanislaw Gruszka | afac7da | 2019-03-07 16:28:18 -0800 | [diff] [blame] | 105 | int n = fls(high); |
Mike Snitzer | eb18cba | 2013-08-20 15:05:17 -0400 | [diff] [blame] | 106 | quot = div_u64(dividend >> n, divisor >> n); |
| 107 | |
| 108 | if (quot != 0) |
| 109 | quot--; |
| 110 | |
| 111 | *remainder = dividend - quot * divisor; |
| 112 | if (*remainder >= divisor) { |
| 113 | quot++; |
| 114 | *remainder -= divisor; |
| 115 | } |
| 116 | } |
| 117 | |
| 118 | return quot; |
| 119 | } |
| 120 | EXPORT_SYMBOL(div64_u64_rem); |
| 121 | #endif |
| 122 | |
| 123 | /** |
Stanislaw Gruszka | f300213 | 2013-04-30 11:35:07 +0200 | [diff] [blame] | 124 | * div64_u64 - unsigned 64bit divide with 64bit divisor |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 125 | * @dividend: 64bit dividend |
| 126 | * @divisor: 64bit divisor |
| 127 | * |
| 128 | * This implementation is a modified version of the algorithm proposed |
| 129 | * by the book 'Hacker's Delight'. The original source and full proof |
| 130 | * can be found here and is available for use without restriction. |
| 131 | * |
Heinrich Schuchardt | 28ca84e | 2015-02-26 20:19:03 +0100 | [diff] [blame] | 132 | * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt' |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 133 | */ |
Stanislaw Gruszka | f300213 | 2013-04-30 11:35:07 +0200 | [diff] [blame] | 134 | #ifndef div64_u64 |
| 135 | u64 div64_u64(u64 dividend, u64 divisor) |
Stephen Hemminger | 3927f2e | 2007-03-25 19:54:23 -0700 | [diff] [blame] | 136 | { |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 137 | u32 high = divisor >> 32; |
| 138 | u64 quot; |
Stephen Hemminger | 3927f2e | 2007-03-25 19:54:23 -0700 | [diff] [blame] | 139 | |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 140 | if (high == 0) { |
Stanislaw Gruszka | f300213 | 2013-04-30 11:35:07 +0200 | [diff] [blame] | 141 | quot = div_u64(dividend, divisor); |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 142 | } else { |
Stanislaw Gruszka | afac7da | 2019-03-07 16:28:18 -0800 | [diff] [blame] | 143 | int n = fls(high); |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 144 | quot = div_u64(dividend >> n, divisor >> n); |
Stephen Hemminger | 3927f2e | 2007-03-25 19:54:23 -0700 | [diff] [blame] | 145 | |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 146 | if (quot != 0) |
| 147 | quot--; |
Stanislaw Gruszka | f300213 | 2013-04-30 11:35:07 +0200 | [diff] [blame] | 148 | if ((dividend - quot * divisor) >= divisor) |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 149 | quot++; |
| 150 | } |
Stephen Hemminger | 3927f2e | 2007-03-25 19:54:23 -0700 | [diff] [blame] | 151 | |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 152 | return quot; |
Stephen Hemminger | 3927f2e | 2007-03-25 19:54:23 -0700 | [diff] [blame] | 153 | } |
Stanislaw Gruszka | f300213 | 2013-04-30 11:35:07 +0200 | [diff] [blame] | 154 | EXPORT_SYMBOL(div64_u64); |
Roman Zippel | 6f6d6a1 | 2008-05-01 04:34:28 -0700 | [diff] [blame] | 155 | #endif |
Stephen Hemminger | 3927f2e | 2007-03-25 19:54:23 -0700 | [diff] [blame] | 156 | |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 157 | /** |
| 158 | * div64_s64 - signed 64bit divide with 64bit divisor |
| 159 | * @dividend: 64bit dividend |
| 160 | * @divisor: 64bit divisor |
| 161 | */ |
| 162 | #ifndef div64_s64 |
| 163 | s64 div64_s64(s64 dividend, s64 divisor) |
| 164 | { |
| 165 | s64 quot, t; |
| 166 | |
Andrew Morton | 79211c8 | 2015-11-09 14:58:13 -0800 | [diff] [blame] | 167 | quot = div64_u64(abs(dividend), abs(divisor)); |
Brian Behlendorf | 658716d | 2010-10-26 14:23:10 -0700 | [diff] [blame] | 168 | t = (dividend ^ divisor) >> 63; |
| 169 | |
| 170 | return (quot ^ t) - t; |
| 171 | } |
| 172 | EXPORT_SYMBOL(div64_s64); |
| 173 | #endif |
| 174 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 175 | #endif /* BITS_PER_LONG == 32 */ |
Jeremy Fitzhardinge | f595ec9 | 2008-06-12 10:47:56 +0200 | [diff] [blame] | 176 | |
| 177 | /* |
| 178 | * Iterative div/mod for use when dividend is not expected to be much |
| 179 | * bigger than divisor. |
| 180 | */ |
| 181 | u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) |
| 182 | { |
Jeremy Fitzhardinge | d5e181f | 2008-06-12 10:47:58 +0200 | [diff] [blame] | 183 | return __iter_div_u64_rem(dividend, divisor, remainder); |
Jeremy Fitzhardinge | f595ec9 | 2008-06-12 10:47:56 +0200 | [diff] [blame] | 184 | } |
| 185 | EXPORT_SYMBOL(iter_div_u64_rem); |