lib/math/div64.c

1 // SPDX-License-Identifier: GPL-2.0
5  * Based on former do_div() implementation from asm-parisc/div64.h:
6  *	Copyright (C) 1999 Hewlett-Packard Co
7  *	Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
10  * Generic C version of 64bit/32bit division and modulo, with
11  * 64bit result and 32bit remainder.
13  * The fast case for (n>>32 == 0) is handled inline by do_div().
16  * for some CPUs. __div64_32() can be overridden by linking arch-specific
25 /* Not needed on 64bit architectures */
26 #if BITS_PER_LONG == 32
34 	uint32_t high = rem >> 32;  in __div64_32()
36 	/* Reduce the thing a bit first */  in __div64_32()
40 		res = (uint64_t) high << 32;  in __div64_32()
41 		rem -= (uint64_t) (high*base) << 32;  in __div64_32()
51 			rem -= b;  in __div64_32()
65  * div_s64_rem - signed 64bit divide with 64bit divisor and remainder
66  * @dividend:	64bit dividend
67  * @divisor:	64bit divisor
68  * @remainder:  64bit remainder
76 		quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);  in div_s64_rem()
77 		*remainder = -*remainder;  in div_s64_rem()
79 			quotient = -quotient;  in div_s64_rem()
83 			quotient = -quotient;  in div_s64_rem()
91  * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
92  * @dividend:	64bit dividend
93  * @divisor:	64bit divisor
94  * @remainder:  64bit remainder
98  * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
104 	u32 high = divisor >> 32;  in div64_u64_rem()
116 			quot--;  in div64_u64_rem()
118 		*remainder = dividend - quot * divisor;  in div64_u64_rem()
121 			*remainder -= divisor;  in div64_u64_rem()
131  * div64_u64 - unsigned 64bit divide with 64bit divisor
132  * @dividend:	64bit dividend
133  * @divisor:	64bit divisor
144 	u32 high = divisor >> 32;  in div64_u64()
154 			quot--;  in div64_u64()
155 		if ((dividend - quot * divisor) >= divisor)  in div64_u64()
165  * div64_s64 - signed 64bit divide with 64bit divisor
166  * @dividend:	64bit dividend
167  * @divisor:	64bit divisor
177 	return (quot ^ t) - t;  in div64_s64()
182 #endif /* BITS_PER_LONG == 32 */
221 		shift = ilog2(a) + ilog2(b) - 62;  in mul_u64_u64_div_u64()