/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _ASM_GENERIC_DIV64_H #define _ASM_GENERIC_DIV64_H /* * Copyright (C) 2003 Bernardo Innocenti * Based on former asm-ppc/div64.h and asm-m68knommu/div64.h * * Optimization for constant divisors on 32-bit machines: * Copyright (C) 2006-2015 Nicolas Pitre * * The semantics of do_div() is, in C++ notation, observing that the name * is a function-like macro and the n parameter has the semantics of a C++ * reference: * * uint32_t do_div(uint64_t &n, uint32_t base) * { * uint32_t remainder = n % base; * n = n / base; * return remainder; * } * * NOTE: macro parameter n is evaluated multiple times, * beware of side effects! */ #include "../types.h" #include "compiler.h" #include "bitsperlong.h" #if BITS_PER_LONG == 64 /** * do_div - returns 2 values: calculate remainder and update new dividend * @n: uint64_t dividend (will be updated) * @base: uint32_t divisor * * Summary: * ``uint32_t remainder = n % base;`` * ``n = n / base;`` * * Return: (uint32_t)remainder * * NOTE: macro parameter @n is evaluated multiple times, * beware of side effects! */ #define do_div(n, base) \ ({ \ uint32_t __base = (base); \ uint32_t __rem; \ __rem = ((uint64_t)(n)) % __base; \ (n) = ((uint64_t)(n)) / __base; \ __rem; \ }) #elif BITS_PER_LONG == 32 // #include // /* // * If the divisor happens to be constant, we determine the appropriate // * inverse at compile time to turn the division into a few inline // * multiplications which ought to be much faster. // * // * (It is unfortunate that gcc doesn't perform all this internally.) // */ // #define __div64_const32(n, ___b) \ // ({ \ // /* \ // * Multiplication by reciprocal of b: n / b = n * (p / b) / p \ // * \ // * We rely on the fact that most of this code gets optimized \ // * away at compile time due to constant propagation and only \ // * a few multiplication instructions should remain. \ // * Hence this monstrous macro (static inline doesn't always \ // * do the trick here). \ // */ \ // uint64_t ___res, ___x, ___t, ___m, ___n = (n); \ // uint32_t ___p, ___bias; \ // \ // /* determine MSB of b */ \ // ___p = 1 << ilog2(___b); \ // \ // /* compute m = ((p << 64) + b - 1) / b */ \ // ___m = (~0ULL / ___b) * ___p; \ // ___m += (((~0ULL % ___b + 1) * ___p) + ___b - 1) / ___b; \ // \ // /* one less than the dividend with highest result */ \ // ___x = ~0ULL / ___b * ___b - 1; \ // \ // /* test our ___m with res = m * x / (p << 64) */ \ // ___res = ((___m & 0xffffffff) * (___x & 0xffffffff)) >> 32; \ // ___t = ___res += (___m & 0xffffffff) * (___x >> 32); \ // ___res += (___x & 0xffffffff) * (___m >> 32); \ // ___t = (___res < ___t) ? (1ULL << 32) : 0; \ // ___res = (___res >> 32) + ___t; \ // ___res += (___m >> 32) * (___x >> 32); \ // ___res /= ___p; \ // \ // /* Now sanitize and optimize what we've got. */ \ // if (~0ULL % (___b / (___b & -___b)) == 0) { \ // /* special case, can be simplified to ... */ \ // ___n /= (___b & -___b); \ // ___m = ~0ULL / (___b / (___b & -___b)); \ // ___p = 1; \ // ___bias = 1; \ // } else if (___res != ___x / ___b) { \ // /* \ // * We can't get away without a bias to compensate \ // * for bit truncation errors. To avoid it we'd need an \ // * additional bit to represent m which would overflow \ // * a 64-bit variable. \ // * \ // * Instead we do m = p / b and n / b = (n * m + m) / p. \ // */ \ // ___bias = 1; \ // /* Compute m = (p << 64) / b */ \ // ___m = (~0ULL / ___b) * ___p; \ // ___m += ((~0ULL % ___b + 1) * ___p) / ___b; \ // } else { \ // /* \ // * Reduce m / p, and try to clear bit 31 of m when \ // * possible, otherwise that'll need extra overflow \ // * handling later. \ // */ \ // uint32_t ___bits = -(___m & -___m); \ // ___bits |= ___m >> 32; \ // ___bits = (~___bits) << 1; \ // /* \ // * If ___bits == 0 then setting bit 31 is unavoidable. \ // * Simply apply the maximum possible reduction in that \ // * case. Otherwise the MSB of ___bits indicates the \ // * best reduction we should apply. \ // */ \ // if (!___bits) { \ // ___p /= (___m & -___m); \ // ___m /= (___m & -___m); \ // } else { \ // ___p >>= ilog2(___bits); \ // ___m >>= ilog2(___bits); \ // } \ // /* No bias needed. */ \ // ___bias = 0; \ // } \ // \ // /* \ // * Now we have a combination of 2 conditions: \ // * \ // * 1) whether or not we need to apply a bias, and \ // * \ // * 2) whether or not there might be an overflow in the cross \ // * product determined by (___m & ((1 << 63) | (1 << 31))). \ // * \ // * Select the best way to do (m_bias + m * n) / (1 << 64). \ // * From now on there will be actual runtime code generated. \ // */ \ // ___res = __arch_xprod_64(___m, ___n, ___bias); \ // \ // ___res /= ___p; \ // }) // #ifndef __arch_xprod_64 // /* // * Default C implementation for __arch_xprod_64() // * // * Prototype: uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias) // * Semantic: retval = ((bias ? m : 0) + m * n) >> 64 // * // * The product is a 128-bit value, scaled down to 64 bits. // * Assuming constant propagation to optimize away unused conditional code. // * Architectures may provide their own optimized assembly implementation. // */ // static inline uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias) // { // uint32_t m_lo = m; // uint32_t m_hi = m >> 32; // uint32_t n_lo = n; // uint32_t n_hi = n >> 32; // uint64_t res; // uint32_t res_lo, res_hi, tmp; // if (!bias) { // res = ((uint64_t)m_lo * n_lo) >> 32; // } else if (!(m & ((1ULL << 63) | (1ULL << 31)))) { // /* there can't be any overflow here */ // res = (m + (uint64_t)m_lo * n_lo) >> 32; // } else { // res = m + (uint64_t)m_lo * n_lo; // res_lo = res >> 32; // res_hi = (res_lo < m_hi); // res = res_lo | ((uint64_t)res_hi << 32); // } // if (!(m & ((1ULL << 63) | (1ULL << 31)))) { // /* there can't be any overflow here */ // res += (uint64_t)m_lo * n_hi; // res += (uint64_t)m_hi * n_lo; // res >>= 32; // } else { // res += (uint64_t)m_lo * n_hi; // tmp = res >> 32; // res += (uint64_t)m_hi * n_lo; // res_lo = res >> 32; // res_hi = (res_lo < tmp); // res = res_lo | ((uint64_t)res_hi << 32); // } // res += (uint64_t)m_hi * n_hi; // return res; // } // #endif // #ifndef __div64_32 // extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor); // #endif // /* The unnecessary pointer compare is there // * to check for type safety (n must be 64bit) // */ // #define do_div(n, base) \ // ({ \ // uint32_t __base = (base); \ // uint32_t __rem; \ // (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \ // if (__builtin_constant_p(__base) && is_power_of_2(__base)) { \ // __rem = (n) & (__base - 1); \ // (n) >>= ilog2(__base); \ // } else if (__builtin_constant_p(__base) && __base != 0) { \ // uint32_t __res_lo, __n_lo = (n); \ // (n) = __div64_const32(n, __base); \ // /* the remainder can be computed with 32-bit regs */ \ // __res_lo = (n); \ // __rem = __n_lo - __res_lo * __base; \ // } else if (likely(((n) >> 32) == 0)) { \ // __rem = (uint32_t)(n) % __base; \ // (n) = (uint32_t)(n) / __base; \ // } else { \ // __rem = __div64_32(&(n), __base); \ // } \ // __rem; \ // }) #else /* BITS_PER_LONG == ?? */ #error do_div() does not yet support the C64 #endif /* BITS_PER_LONG */ #endif /* _ASM_GENERIC_DIV64_H */