source/libs/gmp/gmp-src/mpn/generic/mullo_basecase.c

   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.h"
  37 #include "gmp-impl.h"
  38
  39 /* FIXME: Should optionally use mpn_mul_2/mpn_addmul_2.  */
  40
  41 #ifndef MULLO_VARIANT
  42 #define MULLO_VARIANT 2
  43 #endif
  44
  45
  46 #if MULLO_VARIANT == 1
  47 void
  48 mpn_mullo_basecase (mp_ptr rp, mp_srcptr up, mp_srcptr vp, mp_size_t n)
  49 {
  50   mp_size_t i;
  51
  52   mpn_mul_1 (rp, up, n, vp[0]);
  53
  54   for (i = n - 1; i > 0; i--)
  55     {
  56       vp++;
  57       rp++;
  58       mpn_addmul_1 (rp, up, i, vp[0]);
  59     }
  60 }
  61 #endif
  62
  63
  64 #if MULLO_VARIANT == 2
  65 void
  66 mpn_mullo_basecase (mp_ptr rp, mp_srcptr up, mp_srcptr vp, mp_size_t n)
  67 {
  68   mp_limb_t h;
  69
  70   h = up[0] * vp[n - 1];
  71
  72   if (n != 1)
  73     {
  74       mp_size_t i;
  75       mp_limb_t v0;
  76
  77       v0 = *vp++;
  78       h += up[n - 1] * v0 + mpn_mul_1 (rp, up, n - 1, v0);
  79       rp++;
  80
  81       for (i = n - 2; i > 0; i--)
  82         {
  83           v0 = *vp++;
  84           h += up[i] * v0 + mpn_addmul_1 (rp, up, i, v0);
  85           rp++;
  86         }
  87     }
  88
  89   rp[0] = h;
  90 }
  91 #endif