1/* mpn_toom_eval_dgr3_pm1 -- Evaluate a degree 3 polynomial in +1 and -1
2
3   Contributed to the GNU project by Niels M��ller
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
9Copyright 2009 Free Software Foundation, Inc.
10
11This file is part of the GNU MP Library.
12
13The GNU MP Library is free software; you can redistribute it and/or modify
14it 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
20or
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
26or both in parallel, as here.
27
28The GNU MP Library is distributed in the hope that it will be useful, but
29WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
30or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
31for more details.
32
33You should have received copies of the GNU General Public License and the
34GNU Lesser General Public License along with the GNU MP Library.  If not,
35see https://www.gnu.org/licenses/.  */
36
37
38#include "gmp-impl.h"
39
40int
41mpn_toom_eval_dgr3_pm1 (mp_ptr xp1, mp_ptr xm1,
42			mp_srcptr xp, mp_size_t n, mp_size_t x3n, mp_ptr tp)
43{
44  int neg;
45
46  ASSERT (x3n > 0);
47  ASSERT (x3n <= n);
48
49  xp1[n] = mpn_add_n (xp1, xp, xp + 2*n, n);
50  tp[n] = mpn_add (tp, xp + n, n, xp + 3*n, x3n);
51
52  neg = (mpn_cmp (xp1, tp, n + 1) < 0) ? ~0 : 0;
53
54#if HAVE_NATIVE_mpn_add_n_sub_n
55  if (neg)
56    mpn_add_n_sub_n (xp1, xm1, tp, xp1, n + 1);
57  else
58    mpn_add_n_sub_n (xp1, xm1, xp1, tp, n + 1);
59#else
60  if (neg)
61    mpn_sub_n (xm1, tp, xp1, n + 1);
62  else
63    mpn_sub_n (xm1, xp1, tp, n + 1);
64
65  mpn_add_n (xp1, xp1, tp, n + 1);
66#endif
67
68  ASSERT (xp1[n] <= 3);
69  ASSERT (xm1[n] <= 1);
70
71  return neg;
72}
73