text: /* 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;
  }
  