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236 lines
5.1 KiB
236 lines
5.1 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Copyright (C) 2003 Bernardo Innocenti <[email protected]> |
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* |
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* Based on former do_div() implementation from asm-parisc/div64.h: |
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* Copyright (C) 1999 Hewlett-Packard Co |
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* Copyright (C) 1999 David Mosberger-Tang <[email protected]> |
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* |
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* |
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* Generic C version of 64bit/32bit division and modulo, with |
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* 64bit result and 32bit remainder. |
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* |
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* The fast case for (n>>32 == 0) is handled inline by do_div(). |
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* |
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* Code generated for this function might be very inefficient |
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* for some CPUs. __div64_32() can be overridden by linking arch-specific |
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* assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S |
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* or by defining a preprocessor macro in arch/include/asm/div64.h. |
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*/ |
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#include <linux/bitops.h> |
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#include <linux/export.h> |
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#include <linux/math.h> |
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#include <linux/math64.h> |
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#include <linux/log2.h> |
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/* Not needed on 64bit architectures */ |
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#if BITS_PER_LONG == 32 |
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#ifndef __div64_32 |
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uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base) |
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{ |
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uint64_t rem = *n; |
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uint64_t b = base; |
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uint64_t res, d = 1; |
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uint32_t high = rem >> 32; |
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/* Reduce the thing a bit first */ |
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res = 0; |
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if (high >= base) { |
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high /= base; |
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res = (uint64_t) high << 32; |
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rem -= (uint64_t) (high*base) << 32; |
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} |
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while ((int64_t)b > 0 && b < rem) { |
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b = b+b; |
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d = d+d; |
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} |
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do { |
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if (rem >= b) { |
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rem -= b; |
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res += d; |
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} |
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b >>= 1; |
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d >>= 1; |
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} while (d); |
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*n = res; |
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return rem; |
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} |
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EXPORT_SYMBOL(__div64_32); |
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#endif |
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/** |
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* div_s64_rem - signed 64bit divide with 64bit divisor and remainder |
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* @dividend: 64bit dividend |
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* @divisor: 64bit divisor |
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* @remainder: 64bit remainder |
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*/ |
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#ifndef div_s64_rem |
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s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) |
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{ |
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u64 quotient; |
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if (dividend < 0) { |
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quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder); |
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*remainder = -*remainder; |
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if (divisor > 0) |
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quotient = -quotient; |
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} else { |
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quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder); |
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if (divisor < 0) |
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quotient = -quotient; |
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} |
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return quotient; |
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} |
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EXPORT_SYMBOL(div_s64_rem); |
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#endif |
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/** |
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* div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder |
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* @dividend: 64bit dividend |
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* @divisor: 64bit divisor |
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* @remainder: 64bit remainder |
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* |
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* This implementation is a comparable to algorithm used by div64_u64. |
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* But this operation, which includes math for calculating the remainder, |
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* is kept distinct to avoid slowing down the div64_u64 operation on 32bit |
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* systems. |
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*/ |
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#ifndef div64_u64_rem |
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u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder) |
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{ |
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u32 high = divisor >> 32; |
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u64 quot; |
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if (high == 0) { |
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u32 rem32; |
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quot = div_u64_rem(dividend, divisor, &rem32); |
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*remainder = rem32; |
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} else { |
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int n = fls(high); |
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quot = div_u64(dividend >> n, divisor >> n); |
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if (quot != 0) |
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quot--; |
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*remainder = dividend - quot * divisor; |
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if (*remainder >= divisor) { |
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quot++; |
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*remainder -= divisor; |
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} |
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} |
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return quot; |
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} |
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EXPORT_SYMBOL(div64_u64_rem); |
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#endif |
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/** |
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* div64_u64 - unsigned 64bit divide with 64bit divisor |
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* @dividend: 64bit dividend |
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* @divisor: 64bit divisor |
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* |
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* This implementation is a modified version of the algorithm proposed |
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* by the book 'Hacker's Delight'. The original source and full proof |
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* can be found here and is available for use without restriction. |
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* |
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* 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt' |
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*/ |
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#ifndef div64_u64 |
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u64 div64_u64(u64 dividend, u64 divisor) |
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{ |
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u32 high = divisor >> 32; |
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u64 quot; |
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if (high == 0) { |
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quot = div_u64(dividend, divisor); |
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} else { |
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int n = fls(high); |
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quot = div_u64(dividend >> n, divisor >> n); |
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if (quot != 0) |
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quot--; |
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if ((dividend - quot * divisor) >= divisor) |
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quot++; |
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} |
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return quot; |
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} |
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EXPORT_SYMBOL(div64_u64); |
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#endif |
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/** |
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* div64_s64 - signed 64bit divide with 64bit divisor |
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* @dividend: 64bit dividend |
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* @divisor: 64bit divisor |
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*/ |
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#ifndef div64_s64 |
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s64 div64_s64(s64 dividend, s64 divisor) |
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{ |
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s64 quot, t; |
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quot = div64_u64(abs(dividend), abs(divisor)); |
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t = (dividend ^ divisor) >> 63; |
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return (quot ^ t) - t; |
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} |
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EXPORT_SYMBOL(div64_s64); |
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#endif |
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#endif /* BITS_PER_LONG == 32 */ |
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/* |
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* Iterative div/mod for use when dividend is not expected to be much |
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* bigger than divisor. |
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*/ |
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u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) |
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{ |
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return __iter_div_u64_rem(dividend, divisor, remainder); |
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} |
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EXPORT_SYMBOL(iter_div_u64_rem); |
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#ifndef mul_u64_u64_div_u64 |
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u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c) |
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{ |
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u64 res = 0, div, rem; |
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int shift; |
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/* can a * b overflow ? */ |
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if (ilog2(a) + ilog2(b) > 62) { |
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/* |
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* (b * a) / c is equal to |
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* |
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* (b / c) * a + |
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* (b % c) * a / c |
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* |
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* if nothing overflows. Can the 1st multiplication |
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* overflow? Yes, but we do not care: this can only |
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* happen if the end result can't fit in u64 anyway. |
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* |
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* So the code below does |
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* |
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* res = (b / c) * a; |
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* b = b % c; |
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*/ |
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div = div64_u64_rem(b, c, &rem); |
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res = div * a; |
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b = rem; |
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shift = ilog2(a) + ilog2(b) - 62; |
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if (shift > 0) { |
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/* drop precision */ |
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b >>= shift; |
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c >>= shift; |
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if (!c) |
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return res; |
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} |
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} |
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return res + div64_u64(a * b, c); |
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} |
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EXPORT_SYMBOL(mul_u64_u64_div_u64); |
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#endif
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