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.
16  * for some CPUs. __div64_32() can be overridden by linking arch-specific
28 /* Not needed on 64bit architectures */
39 	/* Reduce the thing a bit first */  in __div64_32()
44 		rem -= (uint64_t) (high*base) << 32;  in __div64_32()
54 			rem -= b;  in __div64_32()
73 		quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);  in div_s64_rem()
74 		*remainder = -*remainder;  in div_s64_rem()
76 			quotient = -quotient;  in div_s64_rem()
80 			quotient = -quotient;  in div_s64_rem()
88  * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
89  * @dividend:	64bit dividend
90  * @divisor:	64bit divisor
91  * @remainder:  64bit remainder
95  * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
113 			quot--;  in div64_u64_rem()
115 		*remainder = dividend - quot * divisor;  in div64_u64_rem()
118 			*remainder -= divisor;  in div64_u64_rem()
128  * div64_u64 - unsigned 64bit divide with 64bit divisor
129  * @dividend:	64bit dividend
130  * @divisor:	64bit divisor
151 			quot--;  in div64_u64()
152 		if ((dividend - quot * divisor) >= divisor)  in div64_u64()
169 	return (quot ^ t) - t;  in div64_s64()
194 	/* native 64x64=128 bits multiplication */  in mul_u64_u64_div_u64()
196 	u64 n_lo = prod, n_hi = prod >> 64;  in mul_u64_u64_div_u64()
200 	/* perform a 64x64=128 bits multiplication manually */  in mul_u64_u64_div_u64()
217 #pragma GCC diagnostic ignored "-Wdiv-by-zero"  in mul_u64_u64_div_u64()
224 	/* try reducing the fraction in case the dividend becomes <= 64 bits */  in mul_u64_u64_div_u64()
226 		u64 n = shift ? (n_lo >> shift) | (n_hi << (64 - shift)) : n_lo;  in mul_u64_u64_div_u64()
232 		 *   rem = (rem << shift) + (n_lo - (n << shift));  in mul_u64_u64_div_u64()
238 		return -1;  in mul_u64_u64_div_u64()
241 	/* Do the full 128 by 64 bits division */  in mul_u64_u64_div_u64()
246 	int p = 64 + shift;  in mul_u64_u64_div_u64()
255 		p -= shift;  in mul_u64_u64_div_u64()
257 		n_hi |= n_lo >> (64 - shift);  in mul_u64_u64_div_u64()
260 			n_hi -= c;  in mul_u64_u64_div_u64()