contrib/gmp/mpn/generic/mul_basecase.c

   1 /* mpn_mul_basecase -- Internal routine to multiply two natural numbers
   2    of length m and n.
   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 1991, 1992, 1993, 1994, 1996, 1997, 2000, 2001, 2002 Free Software
   9 Foundation, Inc.
  10
  11 This file is part of the GNU MP Library.
  12
  13 The GNU MP Library is free software; you can redistribute it and/or modify
  14 it under the terms of the GNU Lesser General Public License as published by
  15 the Free Software Foundation; either version 3 of the License, or (at your
  16 option) any later version.
  17
  18 The GNU MP Library is distributed in the hope that it will be useful, but
  19 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  20 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  21 License for more details.
  22
  23 You should have received a copy of the GNU Lesser General Public License
  24 along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
  25
  26 #include "gmp.h"
  27 #include "gmp-impl.h"
  28
  29
  30 /* Multiply {up,usize} by {vp,vsize} and write the result to
  31    {prodp,usize+vsize}.  Must have usize>=vsize.
  32
  33    Note that prodp gets usize+vsize limbs stored, even if the actual result
  34    only needs usize+vsize-1.
  35
  36    There's no good reason to call here with vsize>=MUL_KARATSUBA_THRESHOLD.
  37    Currently this is allowed, but it might not be in the future.
  38
  39    This is the most critical code for multiplication.  All multiplies rely
  40    on this, both small and huge.  Small ones arrive here immediately, huge
  41    ones arrive here as this is the base case for Karatsuba's recursive
  42    algorithm.  */
  43
  44 void
  45 mpn_mul_basecase (mp_ptr rp,
  46                   mp_srcptr up, mp_size_t un,
  47                   mp_srcptr vp, mp_size_t vn)
  48 {
  49   ASSERT (un >= vn);
  50   ASSERT (vn >= 1);
  51   ASSERT (! MPN_OVERLAP_P (rp, un+vn, up, un));
  52   ASSERT (! MPN_OVERLAP_P (rp, un+vn, vp, vn));
  53
  54   /* We first multiply by the low order limb (or depending on optional function
  55      availability, limbs).  This result can be stored, not added, to rp.  We
  56      also avoid a loop for zeroing this way.  */
  57
  58 #if HAVE_NATIVE_mpn_mul_2
  59   if (vn >= 2)
  60     {
  61       rp[un + 1] = mpn_mul_2 (rp, up, un, vp);
  62       rp += 2, vp += 2, vn -= 2;
  63     }
  64   else
  65     {
  66       rp[un] = mpn_mul_1 (rp, up, un, vp[0]);
  67       return;
  68     }
  69 #else
  70   rp[un] = mpn_mul_1 (rp, up, un, vp[0]);
  71   rp += 1, vp += 1, vn -= 1;
  72 #endif
  73
  74   /* Now accumulate the product of up[] and the next higher limb (or depending
  75      on optional function availability, limbs) from vp[].  */
  76
  77 #define MAX_LEFT MP_SIZE_T_MAX  /* Used to simplify loops into if statements */
  78
  79
  80 #if HAVE_NATIVE_mpn_addmul_6
  81   while (vn >= 6)
  82     {
  83       rp[un + 6 - 1] = mpn_addmul_6 (rp, up, un, vp);
  84       if (MAX_LEFT == 6)
  85         return;
  86       rp += 6, vp += 6, vn -= 6;
  87       if (MAX_LEFT < 2 * 6)
  88         break;
  89     }
  90 #undef MAX_LEFT
  91 #define MAX_LEFT (6 - 1)
  92 #endif
  93
  94 #if HAVE_NATIVE_mpn_addmul_5
  95   while (vn >= 5)
  96     {
  97       rp[un + 5 - 1] = mpn_addmul_5 (rp, up, un, vp);
  98       if (MAX_LEFT == 5)
  99         return;
 100       rp += 5, vp += 5, vn -= 5;
 101       if (MAX_LEFT < 2 * 5)
 102         break;
 103     }
 104 #undef MAX_LEFT
 105 #define MAX_LEFT (5 - 1)
 106 #endif
 107
 108 #if HAVE_NATIVE_mpn_addmul_4
 109   while (vn >= 4)
 110     {
 111       rp[un + 4 - 1] = mpn_addmul_4 (rp, up, un, vp);
 112       if (MAX_LEFT == 4)
 113         return;
 114       rp += 4, vp += 4, vn -= 4;
 115       if (MAX_LEFT < 2 * 4)
 116         break;
 117     }
 118 #undef MAX_LEFT
 119 #define MAX_LEFT (4 - 1)
 120 #endif
 121
 122 #if HAVE_NATIVE_mpn_addmul_3
 123   while (vn >= 3)
 124     {
 125       rp[un + 3 - 1] = mpn_addmul_3 (rp, up, un, vp);
 126       if (MAX_LEFT == 3)
 127         return;
 128       rp += 3, vp += 3, vn -= 3;
 129       if (MAX_LEFT < 2 * 3)
 130         break;
 131     }
 132 #undef MAX_LEFT
 133 #define MAX_LEFT (3 - 1)
 134 #endif
 135
 136 #if HAVE_NATIVE_mpn_addmul_2
 137   while (vn >= 2)
 138     {
 139       rp[un + 2 - 1] = mpn_addmul_2 (rp, up, un, vp);
 140       if (MAX_LEFT == 2)
 141         return;
 142       rp += 2, vp += 2, vn -= 2;
 143       if (MAX_LEFT < 2 * 2)
 144         break;
 145     }
 146 #undef MAX_LEFT
 147 #define MAX_LEFT (2 - 1)
 148 #endif
 149
 150   while (vn >= 1)
 151     {
 152       rp[un] = mpn_addmul_1 (rp, up, un, vp[0]);
 153       if (MAX_LEFT == 1)
 154         return;
 155       rp += 1, vp += 1, vn -= 1;
 156     }
 157 }