1  /* mpn_toom_eval_pm2rexp -- Evaluate a polynomial in +2^-k and -2^-k
       2  
       3     Contributed to the GNU project by Marco Bodrato
       4  
       5     THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.  IT IS ONLY
       6     SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.  IN FACT, IT IS ALMOST
       7     GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
       8  
       9  Copyright 2009 Free Software Foundation, Inc.
      10  
      11  This file is part of the GNU MP Library.
      12  
      13  The GNU MP Library is free software; you can redistribute it and/or modify
      14  it under the terms of either:
      15  
      16    * the GNU Lesser General Public License as published by the Free
      17      Software Foundation; either version 3 of the License, or (at your
      18      option) any later version.
      19  
      20  or
      21  
      22    * the GNU General Public License as published by the Free Software
      23      Foundation; either version 2 of the License, or (at your option) any
      24      later version.
      25  
      26  or both in parallel, as here.
      27  
      28  The GNU MP Library is distributed in the hope that it will be useful, but
      29  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      30  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      31  for more details.
      32  
      33  You should have received copies of the GNU General Public License and the
      34  GNU Lesser General Public License along with the GNU MP Library.  If not,
      35  see https://www.gnu.org/licenses/.  */
      36  
      37  
      38  #include "gmp-impl.h"
      39  
      40  #if HAVE_NATIVE_mpn_addlsh_n
      41  #define DO_mpn_addlsh_n(dst,src,n,s,ws) mpn_addlsh_n(dst,dst,src,n,s)
      42  #else
      43  static mp_limb_t
      44  DO_mpn_addlsh_n(mp_ptr dst, mp_srcptr src, mp_size_t n, unsigned int s, mp_ptr ws)
      45  {
      46  #if USE_MUL_1 && 0
      47    return mpn_addmul_1(dst,src,n,CNST_LIMB(1) <<(s));
      48  #else
      49    mp_limb_t __cy;
      50    __cy = mpn_lshift(ws,src,n,s);
      51    return    __cy + mpn_add_n(dst,dst,ws,n);
      52  #endif
      53  }
      54  #endif
      55  
      56  /* Evaluates a polynomial of degree k >= 3. */
      57  int
      58  mpn_toom_eval_pm2rexp (mp_ptr rp, mp_ptr rm,
      59  		      unsigned int q, mp_srcptr ap, mp_size_t n, mp_size_t t,
      60  		      unsigned int s, mp_ptr ws)
      61  {
      62    unsigned int i;
      63    int neg;
      64    /* {ap,q*n+t} -> {rp,n+1} {rm,n+1} , with {ws, n+1}*/
      65    ASSERT (n >= t);
      66    ASSERT (s != 0); /* or _eval_pm1 should be used */
      67    ASSERT (q > 1);
      68    ASSERT (s*q < GMP_NUMB_BITS);
      69    rp[n] = mpn_lshift(rp, ap, n, s*q);
      70    ws[n] = mpn_lshift(ws, ap+n, n, s*(q-1));
      71    if( (q & 1) != 0) {
      72      ASSERT_NOCARRY(mpn_add(ws,ws,n+1,ap+n*q,t));
      73      rp[n] += DO_mpn_addlsh_n(rp, ap+n*(q-1), n, s, rm);
      74    } else {
      75      ASSERT_NOCARRY(mpn_add(rp,rp,n+1,ap+n*q,t));
      76    }
      77    for(i=2; i<q-1; i++)
      78    {
      79      rp[n] += DO_mpn_addlsh_n(rp, ap+n*i, n, s*(q-i), rm);
      80      i++;
      81      ws[n] += DO_mpn_addlsh_n(ws, ap+n*i, n, s*(q-i), rm);
      82    };
      83  
      84    neg = (mpn_cmp (rp, ws, n + 1) < 0) ? ~0 : 0;
      85  
      86  #if HAVE_NATIVE_mpn_add_n_sub_n
      87    if (neg)
      88      mpn_add_n_sub_n (rp, rm, ws, rp, n + 1);
      89    else
      90      mpn_add_n_sub_n (rp, rm, rp, ws, n + 1);
      91  #else /* !HAVE_NATIVE_mpn_add_n_sub_n */
      92    if (neg)
      93      mpn_sub_n (rm, ws, rp, n + 1);
      94    else
      95      mpn_sub_n (rm, rp, ws, n + 1);
      96  
      97    ASSERT_NOCARRY (mpn_add_n (rp, rp, ws, n + 1));
      98  #endif /* !HAVE_NATIVE_mpn_add_n_sub_n */
      99  
     100    return neg;
     101  }