/* SPDX-License-Identifier: GPL-2.0 */#ifndef _ASM_GENERIC_DIV64_H#define _ASM_GENERIC_DIV64_H/* * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com> * 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() are: * * 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 <linux/types.h>#include <linux/compiler.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 <linux/log2.h> /* * 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. And yet only if compiling * with a sufficiently recent gcc version to perform proper 64-bit constant * propagation. * * (It is unfortunate that gcc doesn't perform all this internally.) */ #ifndef __div64_const32_is_OK#define __div64_const32_is_OK (__GNUC__ >= 4)#endif #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_32extern 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 (__div64_const32_is_OK &&		\		   __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 */