1  /* mpn_mullo_basecase -- Internal routine to multiply two natural
       2     numbers of length n and return the low part.
       3  
       4     THIS IS AN INTERNAL FUNCTION WITH A MUTABLE INTERFACE.  IT IS ONLY
       5     SAFE TO REACH THIS FUNCTION THROUGH DOCUMENTED INTERFACES.
       6  
       7  
       8  Copyright (C) 2000, 2002, 2004, 2015 Free Software Foundation, Inc.
       9  
      10  This file is part of the GNU MP Library.
      11  
      12  The GNU MP Library is free software; you can redistribute it and/or modify
      13  it under the terms of either:
      14  
      15    * the GNU Lesser General Public License as published by the Free
      16      Software Foundation; either version 3 of the License, or (at your
      17      option) any later version.
      18  
      19  or
      20  
      21    * the GNU General Public License as published by the Free Software
      22      Foundation; either version 2 of the License, or (at your option) any
      23      later version.
      24  
      25  or both in parallel, as here.
      26  
      27  The GNU MP Library is distributed in the hope that it will be useful, but
      28  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      29  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      30  for more details.
      31  
      32  You should have received copies of the GNU General Public License and the
      33  GNU Lesser General Public License along with the GNU MP Library.  If not,
      34  see https://www.gnu.org/licenses/.  */
      35  
      36  #include "gmp-impl.h"
      37  
      38  /* FIXME: Should optionally use mpn_mul_2/mpn_addmul_2.  */
      39  
      40  #ifndef MULLO_VARIANT
      41  #define MULLO_VARIANT 2
      42  #endif
      43  
      44  
      45  #if MULLO_VARIANT == 1
      46  void
      47  mpn_mullo_basecase (mp_ptr rp, mp_srcptr up, mp_srcptr vp, mp_size_t n)
      48  {
      49    mp_size_t i;
      50  
      51    mpn_mul_1 (rp, up, n, vp[0]);
      52  
      53    for (i = n - 1; i > 0; i--)
      54      {
      55        vp++;
      56        rp++;
      57        mpn_addmul_1 (rp, up, i, vp[0]);
      58      }
      59  }
      60  #endif
      61  
      62  
      63  #if MULLO_VARIANT == 2
      64  void
      65  mpn_mullo_basecase (mp_ptr rp, mp_srcptr up, mp_srcptr vp, mp_size_t n)
      66  {
      67    mp_limb_t h;
      68  
      69    h = up[0] * vp[n - 1];
      70  
      71    if (n != 1)
      72      {
      73        mp_size_t i;
      74        mp_limb_t v0;
      75  
      76        v0 = *vp++;
      77        h += up[n - 1] * v0 + mpn_mul_1 (rp, up, n - 1, v0);
      78        rp++;
      79  
      80        for (i = n - 2; i > 0; i--)
      81  	{
      82  	  v0 = *vp++;
      83  	  h += up[i] * v0 + mpn_addmul_1 (rp, up, i, v0);
      84  	  rp++;
      85  	}
      86      }
      87  
      88    rp[0] = h;
      89  }
      90  #endif