include/asm-generic/div64.h - arm/linux - Git at Google

 /* 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

 # 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, 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;
 		tmp = (res < m) ? (1ULL << 32) : 0;
 		res = (res >> 32) + tmp;
 	}

 	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 {
 		tmp = res += (uint64_t)m_lo * n_hi;
 		res += (uint64_t)m_hi * n_lo;
 		tmp = (res < tmp) ? (1ULL << 32) : 0;
 		res = (res >> 32) + tmp;
 	}

 	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 (__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 */
	/* 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

	# 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, 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;
	tmp = (res < m) ? (1ULL << 32) : 0;
	res = (res >> 32) + tmp;
	}

	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 {
	tmp = res += (uint64_t)m_lo * n_hi;
	res += (uint64_t)m_hi * n_lo;
	tmp = (res < tmp) ? (1ULL << 32) : 0;
	res = (res >> 32) + tmp;
	}

	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 (__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 */