#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:
   *

   * u32 do_div(u64 *n, u32 base)

   * {

   *	u32 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) ({					\

  	u32 __base = (base);				\
  	u32 __rem;						\
  	__rem = ((u64)(n)) % __base;			\
  	(n) = ((u64)(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).						\
  	 */								\

  	u64 ___res, ___x, ___t, ___m, ___n = (n);			\
  	u32 ___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.					\
  		 */							\

  		u32 ___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: u64 __arch_xprod_64(const u64 m, u64 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 u64 __arch_xprod_64(const u64 m, u64 n, bool bias)

  {

  	u32 m_lo = m;
  	u32 m_hi = m >> 32;
  	u32 n_lo = n;
  	u32 n_hi = n >> 32;
  	u64 res, tmp;

  
  	if (!bias) {

  		res = ((u64)m_lo * n_lo) >> 32;

  	} else if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
  		/* there can't be any overflow here */

  		res = (m + (u64)m_lo * n_lo) >> 32;

  	} else {

  		res = m + (u64)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 += (u64)m_lo * n_hi;
  		res += (u64)m_hi * n_lo;

  		res >>= 32;
  	} else {

  		tmp = res += (u64)m_lo * n_hi;
  		res += (u64)m_hi * n_lo;

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

  	res += (u64)m_hi * n_hi;

  
  	return res;
  }
  #endif
  
  #ifndef __div64_32

  extern u32 __div64_32(u64 *dividend, u32 divisor);

  #endif

  
  /* The unnecessary pointer compare is there
   * to check for type safety (n must be 64bit)
   */
  # define do_div(n,base) ({				\

  	u32 __base = (base);			\
  	u32 __rem;					\
  	(void)(((typeof((n)) *)0) == ((u64 *)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) {			\

  		u32 __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 = (u32)(n) % __base;		\
  		(n) = (u32)(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 */

  /* Wrapper for do_div(). Doesn't modify dividend and returns

   * the result, not remainder.

   */

  static inline u64 lldiv(u64 dividend, u32 divisor)

  {

  	u64 __res = dividend;

  	do_div(__res, divisor);
  	return(__res);
  }

  #endif /* _ASM_GENERIC_DIV64_H */