/* mpn_toom_eval_pm2rexp -- Evaluate a polynomial in +2^-k and -2^-k

   Contributed to the GNU project by Marco Bodrato

   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 WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.

Copyright 2009 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-impl.h"

#if HAVE_NATIVE_mpn_addlsh_n

#define DO_mpn_addlsh_n(dst,src,n,s,ws) mpn_addlsh_n(dst,dst,src,n,s)

#else

static mp_limb_t

DO_mpn_addlsh_n(mp_ptr dst, mp_srcptr src, mp_size_t n, unsigned int s, mp_ptr ws)

{

#if USE_MUL_1 && 0

  return mpn_addmul_1(dst,src,n,CNST_LIMB(1) <<(s));

#else

  mp_limb_t __cy;

  __cy = mpn_lshift(ws,src,n,s);

  return    __cy + mpn_add_n(dst,dst,ws,n);

#endif

}

#endif

/* Evaluates a polynomial of degree k >= 3. */

/* It returns 0 or ~0, depending on the sign of the result rm. */

unsigned

mpn_toom_eval_pm2rexp (mp_ptr rp, mp_ptr rm,

          unsigned int q, mp_srcptr ap, mp_size_t n, mp_size_t t,

          unsigned int s, mp_ptr ws)

{

  unsigned int i;

  unsigned neg;

  /* {ap,q*n+t} -> {rp,n+1} {rm,n+1} , with {ws, n+1}*/

  ASSERT (n >= t);

  ASSERT (s != 0); /* or _eval_pm1 should be used */

  ASSERT (q > 1);

  ASSERT (s*q < GMP_NUMB_BITS);

  rp[n] = mpn_lshift(rp, ap, n, s*q);

  ws[n] = mpn_lshift(ws, ap+n, n, s*(q-1));

  if( (q & 1) != 0) {

    ASSERT_NOCARRY(mpn_add(ws,ws,n+1,ap+n*q,t));

    rp[n] += DO_mpn_addlsh_n(rp, ap+n*(q-1), n, s, rm);

  } else {

    ASSERT_NOCARRY(mpn_add(rp,rp,n+1,ap+n*q,t));

  }

  for(i=2; i<q-1; i++)

  {

    rp[n] += DO_mpn_addlsh_n(rp, ap+n*i, n, s*(q-i), rm);

    i++;

    ws[n] += DO_mpn_addlsh_n(ws, ap+n*i, n, s*(q-i), rm);

  };

  neg = - (unsigned) (mpn_cmp (rp, ws, n + 1) < 0);

#if HAVE_NATIVE_mpn_add_n_sub_n

  if (neg)

    mpn_add_n_sub_n (rp, rm, ws, rp, n + 1);

  else

    mpn_add_n_sub_n (rp, rm, rp, ws, n + 1);

#else /* !HAVE_NATIVE_mpn_add_n_sub_n */

  if (neg)

    mpn_sub_n (rm, ws, rp, n + 1);

  else

    mpn_sub_n (rm, rp, ws, n + 1);

  ASSERT_NOCARRY (mpn_add_n (rp, rp, ws, n + 1));

#endif /* !HAVE_NATIVE_mpn_add_n_sub_n */

  return neg;

}