Coverage Report

Created: 2024-11-21 07:03

/src/libgmp/mpn/toom_eval_dgr3_pm2.c
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/* mpn_toom_eval_dgr3_pm2 -- Evaluate a degree 3 polynomial in +2 and -2
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   Contributed to the GNU project by Niels Möller
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   THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.  IT IS ONLY
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   SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.  IN FACT, IT IS ALMOST
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   GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
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Copyright 2009 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of either:
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  * the GNU Lesser General Public License as published by the Free
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    Software Foundation; either version 3 of the License, or (at your
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    option) any later version.
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or
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  * the GNU General Public License as published by the Free Software
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    Foundation; either version 2 of the License, or (at your option) any
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    later version.
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or both in parallel, as here.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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for more details.
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You should have received copies of the GNU General Public License and the
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GNU Lesser General Public License along with the GNU MP Library.  If not,
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see https://www.gnu.org/licenses/.  */
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#include "gmp-impl.h"
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/* Evaluates a polynomial of degree 3, in the points +2 and -2. */
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/* Needs n+1 limbs of temporary storage. */
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/* It returns 0 or ~0, depending on the sign of the result xm2. */
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unsigned
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mpn_toom_eval_dgr3_pm2 (mp_ptr xp2, mp_ptr xm2,
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      mp_srcptr xp, mp_size_t n, mp_size_t x3n, mp_ptr tp)
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{
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  mp_limb_t cy;
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  unsigned neg;
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  ASSERT (x3n > 0);
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  ASSERT (x3n <= n);
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  /* (x0 + 4 * x2) +/- (2 x1 + 8 x_3) */
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#if HAVE_NATIVE_mpn_addlsh_n || HAVE_NATIVE_mpn_addlsh2_n
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#if HAVE_NATIVE_mpn_addlsh2_n
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  xp2[n] = mpn_addlsh2_n (xp2, xp, xp + 2*n, n);
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  cy = mpn_addlsh2_n (tp, xp + n, xp + 3*n, x3n);
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#else /* HAVE_NATIVE_mpn_addlsh_n */
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  xp2[n] = mpn_addlsh_n (xp2, xp, xp + 2*n, n, 2);
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  cy = mpn_addlsh_n (tp, xp + n, xp + 3*n, x3n, 2);
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#endif
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  if (x3n < n)
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    cy = mpn_add_1 (tp + x3n, xp + n + x3n, n - x3n, cy);
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  tp[n] = cy;
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#else
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  cy = mpn_lshift (tp, xp + 2*n, n, 2);
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  xp2[n] = cy + mpn_add_n (xp2, tp, xp, n);
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  tp[x3n] = mpn_lshift (tp, xp + 3*n, x3n, 2);
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  if (x3n < n)
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    tp[n] = mpn_add (tp, xp + n, n, tp, x3n + 1);
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  else
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    tp[n] += mpn_add_n (tp, xp + n, tp, n);
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#endif
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  mpn_lshift (tp, tp, n+1, 1);
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  neg = - (unsigned) (mpn_cmp (xp2, tp, n + 1) < 0);
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#if HAVE_NATIVE_mpn_add_n_sub_n
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  if (neg)
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    mpn_add_n_sub_n (xp2, xm2, tp, xp2, n + 1);
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  else
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    mpn_add_n_sub_n (xp2, xm2, xp2, tp, n + 1);
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#else
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  if (neg)
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    mpn_sub_n (xm2, tp, xp2, n + 1);
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  else
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    mpn_sub_n (xm2, xp2, tp, n + 1);
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  mpn_add_n (xp2, xp2, tp, n + 1);
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#endif
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  ASSERT (xp2[n] < 15);
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  ASSERT (xm2[n] < 10);
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  return neg;
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}