| /* Cray PVP mpn_add_n -- add two limb vectors and store their sum in a third |
| limb vector. |
| |
| Copyright 1996, 2000, 2001 Free Software Foundation, Inc. |
| |
| This file is part of the GNU MP Library. |
| |
| The GNU MP Library is free software; you can redistribute it and/or modify |
| it under the terms of the GNU Lesser General Public License as published by |
| the Free Software Foundation; either version 3 of the License, or (at your |
| option) any later version. |
| |
| The GNU MP Library is distributed in the hope that it will be useful, but |
| WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
| or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
| License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public License |
| along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ |
| |
| /* This code runs at 4 cycles/limb. It may be possible to bring it down |
| to 3 cycles/limb. */ |
| |
| #include "gmp.h" |
| #include "gmp-impl.h" |
| |
| mp_limb_t |
| mpn_add_n (mp_ptr rp, mp_srcptr up, mp_srcptr vp, mp_size_t n) |
| { |
| mp_limb_t cy[n]; |
| mp_limb_t a, b, r, s0, c0, c1; |
| mp_size_t i; |
| int more_carries; |
| |
| /* Main add loop. Generate a raw output sum in rp[] and a carry vector |
| in cy[]. */ |
| #pragma _CRI ivdep |
| for (i = 0; i < n; i++) |
| { |
| a = up[i]; |
| b = vp[i]; |
| s0 = a + b; |
| rp[i] = s0; |
| c0 = ((a & b) | ((a | b) & ~s0)) >> 63; |
| cy[i] = c0; |
| } |
| /* Carry add loop. Add the carry vector cy[] to the raw sum rp[] and |
| store the new sum back to rp[0]. If this generates further carry, set |
| more_carries. */ |
| more_carries = 0; |
| #pragma _CRI ivdep |
| for (i = 1; i < n; i++) |
| { |
| r = rp[i]; |
| c0 = cy[i - 1]; |
| s0 = r + c0; |
| rp[i] = s0; |
| c0 = (r & ~s0) >> 63; |
| more_carries += c0; |
| } |
| /* If that second loop generated carry, handle that in scalar loop. */ |
| if (more_carries) |
| { |
| mp_limb_t cyrec = 0; |
| /* Look for places where rp[k] is zero and cy[k-1] is non-zero. |
| These are where we got a recurrency carry. */ |
| for (i = 1; i < n; i++) |
| { |
| r = rp[i]; |
| c0 = (r == 0 && cy[i - 1] != 0); |
| s0 = r + cyrec; |
| rp[i] = s0; |
| c1 = (r & ~s0) >> 63; |
| cyrec = c0 | c1; |
| } |
| return cyrec | cy[n - 1]; |
| } |
| |
| return cy[n - 1]; |
| } |