1/* mpn_toom_eval_dgr3_pm2 -- Evaluate a degree 3 polynomial in +2 and -2 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 the GNU Lesser General Public License as published by 15the Free Software Foundation; either version 3 of the License, or (at your 16option) any later version. 17 18The GNU MP Library is distributed in the hope that it will be useful, but 19WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 20or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 21License for more details. 22 23You should have received a copy of the GNU Lesser General Public License 24along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ 25 26 27#include "gmp.h" 28#include "gmp-impl.h" 29 30/* Needs n+1 limbs of temporary storage. */ 31int 32mpn_toom_eval_dgr3_pm2 (mp_ptr xp2, mp_ptr xm2, 33 mp_srcptr xp, mp_size_t n, mp_size_t x3n, mp_ptr tp) 34{ 35 mp_limb_t cy; 36 int neg; 37 38 ASSERT (x3n > 0); 39 ASSERT (x3n <= n); 40 41 /* (x0 + 4 * x2) +/- (2 x1 + 8 x_3) */ 42#if HAVE_NATIVE_mpn_addlsh_n || HAVE_NATIVE_mpn_addlsh2_n 43#if HAVE_NATIVE_mpn_addlsh2_n 44 xp2[n] = mpn_addlsh2_n (xp2, xp, xp + 2*n, n); 45 46 cy = mpn_addlsh2_n (tp, xp + n, xp + 3*n, x3n); 47#else /* HAVE_NATIVE_mpn_addlsh_n */ 48 xp2[n] = mpn_addlsh_n (xp2, xp, xp + 2*n, n, 2); 49 50 cy = mpn_addlsh_n (tp, xp + n, xp + 3*n, x3n, 2); 51#endif 52 if (x3n < n) 53 cy = mpn_add_1 (tp + x3n, xp + n + x3n, n - x3n, cy); 54 tp[n] = cy; 55#else 56 cy = mpn_lshift (tp, xp + 2*n, n, 2); 57 xp2[n] = cy + mpn_add_n (xp2, tp, xp, n); 58 59 tp[x3n] = mpn_lshift (tp, xp + 3*n, x3n, 2); 60 if (x3n < n) 61 tp[n] = mpn_add (tp, xp + n, n, tp, x3n + 1); 62 else 63 tp[n] += mpn_add_n (tp, xp + n, tp, n); 64#endif 65 mpn_lshift (tp, tp, n+1, 1); 66 67 neg = (mpn_cmp (xp2, tp, n + 1) < 0) ? ~0 : 0; 68 69#if HAVE_NATIVE_mpn_add_n_sub_n 70 if (neg) 71 mpn_add_n_sub_n (xp2, xm2, tp, xp2, n + 1); 72 else 73 mpn_add_n_sub_n (xp2, xm2, xp2, tp, n + 1); 74#else 75 if (neg) 76 mpn_sub_n (xm2, tp, xp2, n + 1); 77 else 78 mpn_sub_n (xm2, xp2, tp, n + 1); 79 80 mpn_add_n (xp2, xp2, tp, n + 1); 81#endif 82 83 ASSERT (xp2[n] < 15); 84 ASSERT (xm2[n] < 10); 85 86 return neg; 87} 88