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1// SPDX-License-Identifier: GPL-2.02/*3 * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>4 *5 * Based on former do_div() implementation from asm-parisc/div64.h:6 * Copyright (C) 1999 Hewlett-Packard Co7 * Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>8 *9 *10 * Generic C version of 64bit/32bit division and modulo, with11 * 64bit result and 32bit remainder.12 *13 * The fast case for (n>>32 == 0) is handled inline by do_div().14 *15 * Code generated for this function might be very inefficient16 * for some CPUs. __div64_32() can be overridden by linking arch-specific17 * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S18 * or by defining a preprocessor macro in arch/include/asm/div64.h.19 */20 21#include <linux/bitops.h>22#include <linux/export.h>23#include <linux/math.h>24#include <linux/math64.h>25#include <linux/minmax.h>26#include <linux/log2.h>27 28/* Not needed on 64bit architectures */29#if BITS_PER_LONG == 3230 31#ifndef __div64_3232uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)33{34 uint64_t rem = *n;35 uint64_t b = base;36 uint64_t res, d = 1;37 uint32_t high = rem >> 32;38 39 /* Reduce the thing a bit first */40 res = 0;41 if (high >= base) {42 high /= base;43 res = (uint64_t) high << 32;44 rem -= (uint64_t) (high*base) << 32;45 }46 47 while ((int64_t)b > 0 && b < rem) {48 b = b+b;49 d = d+d;50 }51 52 do {53 if (rem >= b) {54 rem -= b;55 res += d;56 }57 b >>= 1;58 d >>= 1;59 } while (d);60 61 *n = res;62 return rem;63}64EXPORT_SYMBOL(__div64_32);65#endif66 67#ifndef div_s64_rem68s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)69{70 u64 quotient;71 72 if (dividend < 0) {73 quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);74 *remainder = -*remainder;75 if (divisor > 0)76 quotient = -quotient;77 } else {78 quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);79 if (divisor < 0)80 quotient = -quotient;81 }82 return quotient;83}84EXPORT_SYMBOL(div_s64_rem);85#endif86 87/*88 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder89 * @dividend: 64bit dividend90 * @divisor: 64bit divisor91 * @remainder: 64bit remainder92 *93 * This implementation is a comparable to algorithm used by div64_u64.94 * But this operation, which includes math for calculating the remainder,95 * is kept distinct to avoid slowing down the div64_u64 operation on 32bit96 * systems.97 */98#ifndef div64_u64_rem99u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)100{101 u32 high = divisor >> 32;102 u64 quot;103 104 if (high == 0) {105 u32 rem32;106 quot = div_u64_rem(dividend, divisor, &rem32);107 *remainder = rem32;108 } else {109 int n = fls(high);110 quot = div_u64(dividend >> n, divisor >> n);111 112 if (quot != 0)113 quot--;114 115 *remainder = dividend - quot * divisor;116 if (*remainder >= divisor) {117 quot++;118 *remainder -= divisor;119 }120 }121 122 return quot;123}124EXPORT_SYMBOL(div64_u64_rem);125#endif126 127/*128 * div64_u64 - unsigned 64bit divide with 64bit divisor129 * @dividend: 64bit dividend130 * @divisor: 64bit divisor131 *132 * This implementation is a modified version of the algorithm proposed133 * by the book 'Hacker's Delight'. The original source and full proof134 * can be found here and is available for use without restriction.135 *136 * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'137 */138#ifndef div64_u64139u64 div64_u64(u64 dividend, u64 divisor)140{141 u32 high = divisor >> 32;142 u64 quot;143 144 if (high == 0) {145 quot = div_u64(dividend, divisor);146 } else {147 int n = fls(high);148 quot = div_u64(dividend >> n, divisor >> n);149 150 if (quot != 0)151 quot--;152 if ((dividend - quot * divisor) >= divisor)153 quot++;154 }155 156 return quot;157}158EXPORT_SYMBOL(div64_u64);159#endif160 161#ifndef div64_s64162s64 div64_s64(s64 dividend, s64 divisor)163{164 s64 quot, t;165 166 quot = div64_u64(abs(dividend), abs(divisor));167 t = (dividend ^ divisor) >> 63;168 169 return (quot ^ t) - t;170}171EXPORT_SYMBOL(div64_s64);172#endif173 174#endif /* BITS_PER_LONG == 32 */175 176/*177 * Iterative div/mod for use when dividend is not expected to be much178 * bigger than divisor.179 */180u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)181{182 return __iter_div_u64_rem(dividend, divisor, remainder);183}184EXPORT_SYMBOL(iter_div_u64_rem);185 186#ifndef mul_u64_u64_div_u64187u64 mul_u64_u64_div_u64(u64 a, u64 b, u64 c)188{189 if (ilog2(a) + ilog2(b) <= 62)190 return div64_u64(a * b, c);191 192#if defined(__SIZEOF_INT128__)193 194 /* native 64x64=128 bits multiplication */195 u128 prod = (u128)a * b;196 u64 n_lo = prod, n_hi = prod >> 64;197 198#else199 200 /* perform a 64x64=128 bits multiplication manually */201 u32 a_lo = a, a_hi = a >> 32, b_lo = b, b_hi = b >> 32;202 u64 x, y, z;203 204 x = (u64)a_lo * b_lo;205 y = (u64)a_lo * b_hi + (u32)(x >> 32);206 z = (u64)a_hi * b_hi + (u32)(y >> 32);207 y = (u64)a_hi * b_lo + (u32)y;208 z += (u32)(y >> 32);209 x = (y << 32) + (u32)x;210 211 u64 n_lo = x, n_hi = z;212 213#endif214 215 /* make sure c is not zero, trigger exception otherwise */216#pragma GCC diagnostic push217#pragma GCC diagnostic ignored "-Wdiv-by-zero"218 if (unlikely(c == 0))219 return 1/0;220#pragma GCC diagnostic pop221 222 int shift = __builtin_ctzll(c);223 224 /* try reducing the fraction in case the dividend becomes <= 64 bits */225 if ((n_hi >> shift) == 0) {226 u64 n = shift ? (n_lo >> shift) | (n_hi << (64 - shift)) : n_lo;227 228 return div64_u64(n, c >> shift);229 /*230 * The remainder value if needed would be:231 * res = div64_u64_rem(n, c >> shift, &rem);232 * rem = (rem << shift) + (n_lo - (n << shift));233 */234 }235 236 if (n_hi >= c) {237 /* overflow: result is unrepresentable in a u64 */238 return -1;239 }240 241 /* Do the full 128 by 64 bits division */242 243 shift = __builtin_clzll(c);244 c <<= shift;245 246 int p = 64 + shift;247 u64 res = 0;248 bool carry;249 250 do {251 carry = n_hi >> 63;252 shift = carry ? 1 : __builtin_clzll(n_hi);253 if (p < shift)254 break;255 p -= shift;256 n_hi <<= shift;257 n_hi |= n_lo >> (64 - shift);258 n_lo <<= shift;259 if (carry || (n_hi >= c)) {260 n_hi -= c;261 res |= 1ULL << p;262 }263 } while (n_hi);264 /* The remainder value if needed would be n_hi << p */265 266 return res;267}268EXPORT_SYMBOL(mul_u64_u64_div_u64);269#endif270