/* mpn_add_err3_n -- add_n with three error terms

   Contributed by David Harvey.

   THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.  IT IS ONLY

   SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.  IN FACT, IT IS ALMOST

   GUARANTEED THAT IT'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.

Copyright 2011 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"

/*

  Computes:

  (1) {rp,n} := {up,n} + {vp,n} (just like mpn_add_n) with incoming carry cy,

  return value is carry out.

  (2) Let c[i+1] = carry from i-th limb addition (c[0] = cy).

  Computes c[1]*yp1[n-1] + ... + c[n]*yp1[0],

           c[1]*yp2[n-1] + ... + c[n]*yp2[0],

           c[1]*yp3[n-1] + ... + c[n]*yp3[0],

  stores two-limb results at {ep,2}, {ep+2,2} and {ep+4,2} respectively.

  Requires n >= 1.

  None of the outputs may overlap each other or any of the inputs, except

  that {rp,n} may be equal to {up,n} or {vp,n}.

*/

mp_limb_t

mpn_add_err3_n (mp_ptr rp, mp_srcptr up, mp_srcptr vp,

                mp_ptr ep, mp_srcptr yp1, mp_srcptr yp2, mp_srcptr yp3,

                mp_size_t n, mp_limb_t cy)

{

  mp_limb_t el1, eh1, el2, eh2, el3, eh3, ul, vl, yl1, yl2, yl3, zl1, zl2, zl3, rl, sl, cy1, cy2;

  ASSERT (n >= 1);

  ASSERT (MPN_SAME_OR_SEPARATE_P (rp, up, n));

  ASSERT (MPN_SAME_OR_SEPARATE_P (rp, vp, n));

  ASSERT (! MPN_OVERLAP_P (rp, n, yp1, n));

  ASSERT (! MPN_OVERLAP_P (rp, n, yp2, n));

  ASSERT (! MPN_OVERLAP_P (rp, n, yp3, n));

  ASSERT (! MPN_OVERLAP_P (ep, 6, up, n));

  ASSERT (! MPN_OVERLAP_P (ep, 6, vp, n));

  ASSERT (! MPN_OVERLAP_P (ep, 6, yp1, n));

  ASSERT (! MPN_OVERLAP_P (ep, 6, yp2, n));

  ASSERT (! MPN_OVERLAP_P (ep, 6, yp3, n));

  ASSERT (! MPN_OVERLAP_P (ep, 6, rp, n));

  yp1 += n - 1;

  yp2 += n - 1;

  yp3 += n - 1;

  el1 = eh1 = 0;

  el2 = eh2 = 0;

  el3 = eh3 = 0;

  do

    {

      yl1 = *yp1--;

      yl2 = *yp2--;

      yl3 = *yp3--;

      ul = *up++;

      vl = *vp++;

      /* ordinary add_n */

      ADDC_LIMB (cy1, sl, ul, vl);

      ADDC_LIMB (cy2, rl, sl, cy);

      cy = cy1 | cy2;

      *rp++ = rl;

      /* update (eh1:el1) */

      zl1 = (-cy) & yl1;

      el1 += zl1;

      eh1 += el1 < zl1;

      /* update (eh2:el2) */

      zl2 = (-cy) & yl2;

      el2 += zl2;

      eh2 += el2 < zl2;

      /* update (eh3:el3) */

      zl3 = (-cy) & yl3;

      el3 += zl3;

      eh3 += el3 < zl3;

    }

  while (--n);

#if GMP_NAIL_BITS != 0

  eh1 = (eh1 << GMP_NAIL_BITS) + (el1 >> GMP_NUMB_BITS);

  el1 &= GMP_NUMB_MASK;

  eh2 = (eh2 << GMP_NAIL_BITS) + (el2 >> GMP_NUMB_BITS);

  el2 &= GMP_NUMB_MASK;

  eh3 = (eh3 << GMP_NAIL_BITS) + (el3 >> GMP_NUMB_BITS);

  el3 &= GMP_NUMB_MASK;

#endif

  ep[0] = el1;

  ep[1] = eh1;

  ep[2] = el2;

  ep[3] = eh2;

  ep[4] = el3;

  ep[5] = eh3;

  return cy;

}