github.com/aergoio/aergo@v1.3.1/libtool/src/gmp-6.1.2/mpn/cray/ieee/addmul_1.c (about)

     1  /* Cray PVP/IEEE mpn_addmul_1 -- multiply a limb vector with a limb and add the
     2     result to a second limb vector.
     3  
     4  Copyright 2000-2002 Free Software Foundation, Inc.
     5  
     6  This file is part of the GNU MP Library.
     7  
     8  The GNU MP Library is free software; you can redistribute it and/or modify
     9  it under the terms of either:
    10  
    11    * the GNU Lesser General Public License as published by the Free
    12      Software Foundation; either version 3 of the License, or (at your
    13      option) any later version.
    14  
    15  or
    16  
    17    * the GNU General Public License as published by the Free Software
    18      Foundation; either version 2 of the License, or (at your option) any
    19      later version.
    20  
    21  or both in parallel, as here.
    22  
    23  The GNU MP Library is distributed in the hope that it will be useful, but
    24  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    25  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    26  for more details.
    27  
    28  You should have received copies of the GNU General Public License and the
    29  GNU Lesser General Public License along with the GNU MP Library.  If not,
    30  see https://www.gnu.org/licenses/.  */
    31  
    32  /* This code runs at just under 9 cycles/limb on a T90.  That is not perfect,
    33     mainly due to vector register shortage in the main loop.  Assembly code
    34     should bring it down to perhaps 7 cycles/limb.  */
    35  
    36  #include <intrinsics.h>
    37  #include "gmp.h"
    38  #include "gmp-impl.h"
    39  
    40  mp_limb_t
    41  mpn_addmul_1 (mp_ptr rp, mp_srcptr up, mp_size_t n, mp_limb_t vl)
    42  {
    43    mp_limb_t cy[n];
    44    mp_limb_t a, b, r, s0, s1, c0, c1;
    45    mp_size_t i;
    46    int more_carries;
    47  
    48    if (up == rp)
    49      {
    50        /* The algorithm used below cannot handle overlap.  Handle it here by
    51  	 making a temporary copy of the source vector, then call ourselves.  */
    52        mp_limb_t xp[n];
    53        MPN_COPY (xp, up, n);
    54        return mpn_addmul_1 (rp, xp, n, vl);
    55      }
    56  
    57    a = up[0] * vl;
    58    r = rp[0];
    59    s0 = a + r;
    60    rp[0] = s0;
    61    c0 = ((a & r) | ((a | r) & ~s0)) >> 63;
    62    cy[0] = c0;
    63  
    64    /* Main multiply loop.  Generate a raw accumulated output product in rp[]
    65       and a carry vector in cy[].  */
    66  #pragma _CRI ivdep
    67    for (i = 1; i < n; i++)
    68      {
    69        a = up[i] * vl;
    70        b = _int_mult_upper (up[i - 1], vl);
    71        s0 = a + b;
    72        c0 = ((a & b) | ((a | b) & ~s0)) >> 63;
    73        r = rp[i];
    74        s1 = s0 + r;
    75        rp[i] = s1;
    76        c1 = ((s0 & r) | ((s0 | r) & ~s1)) >> 63;
    77        cy[i] = c0 + c1;
    78      }
    79    /* Carry add loop.  Add the carry vector cy[] to the raw result rp[] and
    80       store the new result back to rp[].  */
    81    more_carries = 0;
    82  #pragma _CRI ivdep
    83    for (i = 1; i < n; i++)
    84      {
    85        r = rp[i];
    86        c0 = cy[i - 1];
    87        s0 = r + c0;
    88        rp[i] = s0;
    89        c0 = (r & ~s0) >> 63;
    90        more_carries += c0;
    91      }
    92    /* If that second loop generated carry, handle that in scalar loop.  */
    93    if (more_carries)
    94      {
    95        mp_limb_t cyrec = 0;
    96        /* Look for places where rp[k] == 0 and cy[k-1] == 1 or
    97  	 rp[k] == 1 and cy[k-1] == 2.
    98  	 These are where we got a recurrency carry.  */
    99        for (i = 1; i < n; i++)
   100  	{
   101  	  r = rp[i];
   102  	  c0 = r < cy[i - 1];
   103  	  s0 = r + cyrec;
   104  	  rp[i] = s0;
   105  	  c1 = (r & ~s0) >> 63;
   106  	  cyrec = c0 | c1;
   107  	}
   108        return _int_mult_upper (up[n - 1], vl) + cyrec + cy[n - 1];
   109      }
   110  
   111    return _int_mult_upper (up[n - 1], vl) + cy[n - 1];
   112  }