github.com/aergoio/aergo@v1.3.1/libtool/src/gmp-6.1.2/mpn/generic/add_err3_n.c (about)

     1  /* mpn_add_err3_n -- add_n with three error terms
     2  
     3     Contributed by David Harvey.
     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'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
     8  
     9  Copyright 2011 Free Software 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 either:
    15  
    16    * the GNU Lesser General Public License as published by the Free
    17      Software Foundation; either version 3 of the License, or (at your
    18      option) any later version.
    19  
    20  or
    21  
    22    * the GNU General Public License as published by the Free Software
    23      Foundation; either version 2 of the License, or (at your option) any
    24      later version.
    25  
    26  or both in parallel, as here.
    27  
    28  The GNU MP Library is distributed in the hope that it will be useful, but
    29  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    30  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    31  for more details.
    32  
    33  You should have received copies of the GNU General Public License and the
    34  GNU Lesser General Public License along with the GNU MP Library.  If not,
    35  see https://www.gnu.org/licenses/.  */
    36  
    37  #include "gmp.h"
    38  #include "gmp-impl.h"
    39  
    40  /*
    41    Computes:
    42  
    43    (1) {rp,n} := {up,n} + {vp,n} (just like mpn_add_n) with incoming carry cy,
    44    return value is carry out.
    45  
    46    (2) Let c[i+1] = carry from i-th limb addition (c[0] = cy).
    47    Computes c[1]*yp1[n-1] + ... + c[n]*yp1[0],
    48             c[1]*yp2[n-1] + ... + c[n]*yp2[0],
    49             c[1]*yp3[n-1] + ... + c[n]*yp3[0],
    50    stores two-limb results at {ep,2}, {ep+2,2} and {ep+4,2} respectively.
    51  
    52    Requires n >= 1.
    53  
    54    None of the outputs may overlap each other or any of the inputs, except
    55    that {rp,n} may be equal to {up,n} or {vp,n}.
    56  */
    57  mp_limb_t
    58  mpn_add_err3_n (mp_ptr rp, mp_srcptr up, mp_srcptr vp,
    59                  mp_ptr ep, mp_srcptr yp1, mp_srcptr yp2, mp_srcptr yp3,
    60                  mp_size_t n, mp_limb_t cy)
    61  {
    62    mp_limb_t el1, eh1, el2, eh2, el3, eh3, ul, vl, yl1, yl2, yl3, zl1, zl2, zl3, rl, sl, cy1, cy2;
    63  
    64    ASSERT (n >= 1);
    65    ASSERT (MPN_SAME_OR_SEPARATE_P (rp, up, n));
    66    ASSERT (MPN_SAME_OR_SEPARATE_P (rp, vp, n));
    67    ASSERT (! MPN_OVERLAP_P (rp, n, yp1, n));
    68    ASSERT (! MPN_OVERLAP_P (rp, n, yp2, n));
    69    ASSERT (! MPN_OVERLAP_P (rp, n, yp3, n));
    70    ASSERT (! MPN_OVERLAP_P (ep, 6, up, n));
    71    ASSERT (! MPN_OVERLAP_P (ep, 6, vp, n));
    72    ASSERT (! MPN_OVERLAP_P (ep, 6, yp1, n));
    73    ASSERT (! MPN_OVERLAP_P (ep, 6, yp2, n));
    74    ASSERT (! MPN_OVERLAP_P (ep, 6, yp3, n));
    75    ASSERT (! MPN_OVERLAP_P (ep, 6, rp, n));
    76  
    77    yp1 += n - 1;
    78    yp2 += n - 1;
    79    yp3 += n - 1;
    80    el1 = eh1 = 0;
    81    el2 = eh2 = 0;
    82    el3 = eh3 = 0;
    83  
    84    do
    85      {
    86        yl1 = *yp1--;
    87        yl2 = *yp2--;
    88        yl3 = *yp3--;
    89        ul = *up++;
    90        vl = *vp++;
    91  
    92        /* ordinary add_n */
    93        ADDC_LIMB (cy1, sl, ul, vl);
    94        ADDC_LIMB (cy2, rl, sl, cy);
    95        cy = cy1 | cy2;
    96        *rp++ = rl;
    97  
    98        /* update (eh1:el1) */
    99        zl1 = (-cy) & yl1;
   100        el1 += zl1;
   101        eh1 += el1 < zl1;
   102  
   103        /* update (eh2:el2) */
   104        zl2 = (-cy) & yl2;
   105        el2 += zl2;
   106        eh2 += el2 < zl2;
   107  
   108        /* update (eh3:el3) */
   109        zl3 = (-cy) & yl3;
   110        el3 += zl3;
   111        eh3 += el3 < zl3;
   112      }
   113    while (--n);
   114  
   115  #if GMP_NAIL_BITS != 0
   116    eh1 = (eh1 << GMP_NAIL_BITS) + (el1 >> GMP_NUMB_BITS);
   117    el1 &= GMP_NUMB_MASK;
   118    eh2 = (eh2 << GMP_NAIL_BITS) + (el2 >> GMP_NUMB_BITS);
   119    el2 &= GMP_NUMB_MASK;
   120    eh3 = (eh3 << GMP_NAIL_BITS) + (el3 >> GMP_NUMB_BITS);
   121    el3 &= GMP_NUMB_MASK;
   122  #endif
   123  
   124    ep[0] = el1;
   125    ep[1] = eh1;
   126    ep[2] = el2;
   127    ep[3] = eh2;
   128    ep[4] = el3;
   129    ep[5] = eh3;
   130  
   131    return cy;
   132  }