[linux.git] / lib / div64.c

/*
 * Copyright (C) 2003 Bernardo Innocenti <[email protected]>
 *
 * Based on former do_div() implementation from asm-parisc/div64.h:
 *	Copyright (C) 1999 Hewlett-Packard Co
 *	Copyright (C) 1999 David Mosberger-Tang <[email protected]>
 *
 *
 * 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
 * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S.
 */

#include <linux/types.h>
#include <linux/module.h>
#include <asm/div64.h>

/* Not needed on 64bit architectures */
#if BITS_PER_LONG == 32

uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
{
	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;
}

EXPORT_SYMBOL(__div64_32);

/* 64bit divisor, dividend and result. dynamic precision */
uint64_t div64_64(uint64_t dividend, uint64_t divisor)
{
	uint32_t high, d;

	high = divisor >> 32;
	if (high) {
		unsigned int shift = fls(high);

		d = divisor >> shift;
		dividend >>= shift;
	} else
		d = divisor;

	do_div(dividend, d);

	return dividend;
}
EXPORT_SYMBOL(div64_64);

#endif /* BITS_PER_LONG == 32 */
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Copyright (C) 2003 Bernardo Innocenti <[email protected]>
	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 <[email protected]>
	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
	16	* assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S.
	17	*/
	18
	19	#include <linux/types.h>
	20	#include <linux/module.h>
	21	#include <asm/div64.h>
	22
	23	/* Not needed on 64bit architectures */
	24	#if BITS_PER_LONG == 32
	25
cb8c181f	26	uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
1da177e4 LT	27	{
	28	uint64_t rem = *n;
	29	uint64_t b = base;
	30	uint64_t res, d = 1;
	31	uint32_t high = rem >> 32;
	32
	33	/* Reduce the thing a bit first */
	34	res = 0;
	35	if (high >= base) {
	36	high /= base;
	37	res = (uint64_t) high << 32;
	38	rem -= (uint64_t) (high*base) << 32;
	39	}
	40
	41	while ((int64_t)b > 0 && b < rem) {
	42	b = b+b;
	43	d = d+d;
	44	}
	45
	46	do {
	47	if (rem >= b) {
	48	rem -= b;
	49	res += d;
	50	}
	51	b >>= 1;
	52	d >>= 1;
	53	} while (d);
	54
	55	*n = res;
	56	return rem;
	57	}
	58
	59	EXPORT_SYMBOL(__div64_32);
	60
3927f2e8 SH	61	/* 64bit divisor, dividend and result. dynamic precision */
	62	uint64_t div64_64(uint64_t dividend, uint64_t divisor)
	63	{
22b9a0a3	64	uint32_t high, d;
3927f2e8	65
22b9a0a3 SH	66	high = divisor >> 32;
	67	if (high) {
	68	unsigned int shift = fls(high);
3927f2e8 SH	69
	70	d = divisor >> shift;
	71	dividend >>= shift;
22b9a0a3 SH	72	} else
22b9a0a3 SH	73	d = divisor;
3927f2e8	74
22b9a0a3	75	do_div(dividend, d);
3927f2e8 SH	76
	77	return dividend;
	78	}
	79	EXPORT_SYMBOL(div64_64);
	80
1da177e4	81	#endif /* BITS_PER_LONG == 32 */