https://github.com/torvalds/linux
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Tip revision: 14ccee78fc82f5512908f4424f541549a5705b89 authored by Linus Torvalds on 20 August 2017, 21:13:52 UTC
Linux 4.13-rc6
Tip revision: 14ccee7
reciprocal_div.c
#include <linux/kernel.h>
#include <asm/div64.h>
#include <linux/reciprocal_div.h>
#include <linux/export.h>

/*
 * For a description of the algorithm please have a look at
 * include/linux/reciprocal_div.h
 */

struct reciprocal_value reciprocal_value(u32 d)
{
	struct reciprocal_value R;
	u64 m;
	int l;

	l = fls(d - 1);
	m = ((1ULL << 32) * ((1ULL << l) - d));
	do_div(m, d);
	++m;
	R.m = (u32)m;
	R.sh1 = min(l, 1);
	R.sh2 = max(l - 1, 0);

	return R;
}
EXPORT_SYMBOL(reciprocal_value);
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