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lib/div64.c
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// SPDX-License-Identifier: GPL-2.0 |
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/* * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com> * * Based on former do_div() implementation from asm-parisc/div64.h: * Copyright (C) 1999 Hewlett-Packard Co * Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com> * * * Generic C version of 64bit/32bit division and modulo, with * 64bit result and 32bit remainder. * * The fast case for (n>>32 == 0) is handled inline by do_div(). * * Code generated for this function might be very inefficient * 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 * or by defining a preprocessor macro in arch/include/asm/div64.h. |
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*/ |
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#include <linux/export.h> #include <linux/kernel.h> |
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#include <linux/math64.h> |
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/* Not needed on 64bit architectures */ #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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{ uint64_t rem = *n; uint64_t b = base; uint64_t res, d = 1; uint32_t high = rem >> 32; /* Reduce the thing a bit first */ res = 0; if (high >= base) { high /= base; res = (uint64_t) high << 32; rem -= (uint64_t) (high*base) << 32; } while ((int64_t)b > 0 && b < rem) { b = b+b; d = d+d; } do { if (rem >= b) { rem -= b; res += d; } b >>= 1; d >>= 1; } while (d); *n = res; return rem; } |
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EXPORT_SYMBOL(__div64_32); |
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#endif |
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/** * div_s64_rem - signed 64bit divide with 64bit divisor and remainder * @dividend: 64bit dividend * @divisor: 64bit divisor * @remainder: 64bit remainder */ |
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#ifndef div_s64_rem s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) { u64 quotient; if (dividend < 0) { quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder); *remainder = -*remainder; if (divisor > 0) quotient = -quotient; } else { quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder); if (divisor < 0) quotient = -quotient; } return quotient; } EXPORT_SYMBOL(div_s64_rem); #endif |
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/** |
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* div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder * @dividend: 64bit dividend * @divisor: 64bit divisor * @remainder: 64bit remainder * * This implementation is a comparable to algorithm used by div64_u64. * But this operation, which includes math for calculating the remainder, * is kept distinct to avoid slowing down the div64_u64 operation on 32bit * systems. */ #ifndef div64_u64_rem u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder) { u32 high = divisor >> 32; u64 quot; if (high == 0) { u32 rem32; quot = div_u64_rem(dividend, divisor, &rem32); *remainder = rem32; } else { int n = 1 + fls(high); quot = div_u64(dividend >> n, divisor >> n); if (quot != 0) quot--; *remainder = dividend - quot * divisor; if (*remainder >= divisor) { quot++; *remainder -= divisor; } } return quot; } EXPORT_SYMBOL(div64_u64_rem); #endif /** |
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* div64_u64 - unsigned 64bit divide with 64bit divisor |
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* @dividend: 64bit dividend * @divisor: 64bit divisor * * This implementation is a modified version of the algorithm proposed * by the book 'Hacker's Delight'. The original source and full proof * can be found here and is available for use without restriction. * |
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* 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt' |
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*/ |
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#ifndef div64_u64 u64 div64_u64(u64 dividend, u64 divisor) |
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{ |
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u32 high = divisor >> 32; u64 quot; |
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if (high == 0) { |
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quot = div_u64(dividend, divisor); |
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} else { int n = 1 + fls(high); quot = div_u64(dividend >> n, divisor >> n); |
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if (quot != 0) quot--; |
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if ((dividend - quot * divisor) >= divisor) |
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quot++; } |
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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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/** * div64_s64 - signed 64bit divide with 64bit divisor * @dividend: 64bit dividend * @divisor: 64bit divisor */ #ifndef div64_s64 s64 div64_s64(s64 dividend, s64 divisor) { s64 quot, t; |
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quot = div64_u64(abs(dividend), abs(divisor)); |
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t = (dividend ^ divisor) >> 63; return (quot ^ t) - t; } EXPORT_SYMBOL(div64_s64); #endif |
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#endif /* BITS_PER_LONG == 32 */ |
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/* * Iterative div/mod for use when dividend is not expected to be much * bigger than divisor. */ u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) { |
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return __iter_div_u64_rem(dividend, divisor, remainder); |
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} EXPORT_SYMBOL(iter_div_u64_rem); |