/* UltraSparc 64 mpn_divrem_1 -- mpn by limb division.

Copyright 1991, 1993, 1994, 1996, 1998-2001, 2003 Free Software Foundation,

Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify

it under the terms of either:

  * the GNU Lesser General Public License as published by the Free

    Software Foundation; either version 3 of the License, or (at your

    option) any later version.

or

  * the GNU General Public License as published by the Free Software

    Foundation; either version 2 of the License, or (at your option) any

    later version.

or both in parallel, as here.

The GNU MP Library is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

for more details.

You should have received copies of the GNU General Public License and the

GNU Lesser General Public License along with the GNU MP Library.  If not,

see https://www.gnu.org/licenses/.  */

#include "gmp.h"

#include "gmp-impl.h"

#include "longlong.h"

#include "mpn/sparc64/sparc64.h"

/*                   64-bit divisor       32-bit divisor

                       cycles/limb          cycles/limb

                        (approx)             (approx)

                   integer  fraction    integer  fraction

   Ultrasparc 2i:    160      160          122      96

*/

/* 32-bit divisors are treated in special case code.  This requires 4 mulx

   per limb instead of 8 in the general case.

   For big endian systems we need HALF_ENDIAN_ADJ included in the src[i]

   addressing, to get the two halves of each limb read in the correct order.

   This is kept in an adj variable.  Doing that measures about 4 c/l faster

   than just writing HALF_ENDIAN_ADJ(i) in the integer loop.  The latter

   shouldn't be 6 cycles worth of work, but perhaps it doesn't schedule well

   (on gcc 3.2.1 at least).  The fraction loop doesn't seem affected, but we

   still use a variable since that ought to work out best.  */

mp_limb_t

mpn_divrem_1 (mp_ptr qp_limbptr, mp_size_t xsize_limbs,

              mp_srcptr ap_limbptr, mp_size_t size_limbs, mp_limb_t d_limb)

{

  mp_size_t  total_size_limbs;

  mp_size_t  i;

  ASSERT (xsize_limbs >= 0);

  ASSERT (size_limbs >= 0);

  ASSERT (d_limb != 0);

  /* FIXME: What's the correct overlap rule when xsize!=0? */

  ASSERT (MPN_SAME_OR_SEPARATE_P (qp_limbptr + xsize_limbs,

                                  ap_limbptr, size_limbs));

  total_size_limbs = size_limbs + xsize_limbs;

  if (UNLIKELY (total_size_limbs == 0))

    return 0;

  /* udivx is good for total_size==1, and no need to bother checking

     limb

  if (UNLIKELY (total_size_limbs == 1))

    {

      mp_limb_t  a, q;

      a = (LIKELY (size_limbs != 0) ? ap_limbptr[0] : 0);

      q = a / d_limb;

      qp_limbptr[0] = q;

      return a - q*d_limb;

    }

  if (d_limb <= CNST_LIMB(0xFFFFFFFF))

    {

      mp_size_t  size, xsize, total_size, adj;

      unsigned   *qp, n1, n0, q, r, nshift, norm_rmask;

      mp_limb_t  dinv_limb;

      const unsigned *ap;

      int        norm, norm_rshift;

      size = 2 * size_limbs;

      xsize = 2 * xsize_limbs;

      total_size = size + xsize;

      ap = (unsigned *) ap_limbptr;

      qp = (unsigned *) qp_limbptr;

      qp += xsize;

      r = 0;        /* initial remainder */

      if (LIKELY (size != 0))

        {

          n1 = ap[size-1 + HALF_ENDIAN_ADJ(1)];

          /* If the length of the source is uniformly distributed, then

             there's a 50% chance of the high 32-bits being zero, which we

             can skip.  */

          if (n1 == 0)

            {

              n1 = ap[size-2 + HALF_ENDIAN_ADJ(0)];

              total_size--;

              size--;

              ASSERT (size > 0);  /* because always even */

              qp[size + HALF_ENDIAN_ADJ(1)] = 0;

            }

          /* Skip a division if high < divisor (high quotient 0).  Testing

             here before before normalizing will still skip as often as

             possible.  */

          if (n1 < d_limb)

            {

              r = n1;

              size--;

              qp[size + HALF_ENDIAN_ADJ(size)] = 0;

              total_size--;

              if (total_size == 0)

                return r;

            }

        }

      count_leading_zeros_32 (norm, d_limb);

      norm -= 32;

      d_limb <<= norm;

      r <<= norm;

      norm_rshift = 32 - norm;

      norm_rmask = (norm == 0 ? 0 : 0xFFFFFFFF);

      invert_half_limb (dinv_limb, d_limb);

      if (LIKELY (size != 0))

        {

          i = size - 1;

          adj = HALF_ENDIAN_ADJ (i);

          n1 = ap[i + adj];

          adj = -adj;

          r |= ((n1 >> norm_rshift) & norm_rmask);

          for ( ; i > 0; i--)

            {

              n0 = ap[i-1 + adj];

              adj = -adj;

              nshift = (n1 << norm) | ((n0 >> norm_rshift) & norm_rmask);

              udiv_qrnnd_half_preinv (q, r, r, nshift, d_limb, dinv_limb);

              qp[i + adj] = q;

              n1 = n0;

            }

          nshift = n1 << norm;

          udiv_qrnnd_half_preinv (q, r, r, nshift, d_limb, dinv_limb);

          qp[0 + HALF_ENDIAN_ADJ(0)] = q;

        }

      qp -= xsize;

      adj = HALF_ENDIAN_ADJ (0);

      for (i = xsize-1; i >= 0; i--)

        {

          udiv_qrnnd_half_preinv (q, r, r, 0, d_limb, dinv_limb);

          adj = -adj;

          qp[i + adj] = q;

        }

      return r >> norm;

    }

  else

    {

      mp_srcptr  ap;

      mp_ptr     qp;

      mp_size_t  size, xsize, total_size;

      mp_limb_t  d, n1, n0, q, r, dinv, nshift, norm_rmask;

      int        norm, norm_rshift;

      ap = ap_limbptr;

      qp = qp_limbptr;

      size = size_limbs;

      xsize = xsize_limbs;

      total_size = total_size_limbs;

      d = d_limb;

      qp += total_size;   /* above high limb */

      r = 0;              /* initial remainder */

      if (LIKELY (size != 0))

        {

          /* Skip a division if high < divisor (high quotient 0).  Testing

             here before before normalizing will still skip as often as

             possible.  */

          n1 = ap[size-1];

          if (n1 < d)

            {

              r = n1;

              *--qp = 0;

              total_size--;

              if (total_size == 0)

                return r;

              size--;

            }

        }

      count_leading_zeros (norm, d);

      d <<= norm;

      r <<= norm;

      norm_rshift = GMP_LIMB_BITS - norm;

      norm_rmask = (norm == 0 ? 0 : ~CNST_LIMB(0));

      invert_limb (dinv, d);

      if (LIKELY (size != 0))

        {

          n1 = ap[size-1];

          r |= ((n1 >> norm_rshift) & norm_rmask);

          for (i = size-2; i >= 0; i--)

            {

              n0 = ap[i];

              nshift = (n1 << norm) | ((n0 >> norm_rshift) & norm_rmask);

              udiv_qrnnd_preinv (q, r, r, nshift, d, dinv);

              *--qp = q;

              n1 = n0;

            }

          nshift = n1 << norm;

          udiv_qrnnd_preinv (q, r, r, nshift, d, dinv);

          *--qp = q;

        }

      for (i = 0; i < xsize; i++)

        {

          udiv_qrnnd_preinv (q, r, r, CNST_LIMB(0), d, dinv);

          *--qp = q;

        }

      return r >> norm;

    }

}