source/libs/gmp/gmp-src/mpn/cray/ieee/addmul_1.c

   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 }