| /* Cray PVP/IEEE mpn_submul_1 -- multiply a limb vector with a limb and |
| subtract the result from a second limb vector. |
| |
| Copyright 2000, 2001, 2002 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 just under 9 cycles/limb on a T90. That is not perfect, |
| mainly due to vector register shortage in the main loop. Assembly code |
| should bring it down to perhaps 7 cycles/limb. */ |
| |
| #include <intrinsics.h> |
| #include "gmp.h" |
| #include "gmp-impl.h" |
| |
| mp_limb_t |
| mpn_submul_1 (mp_ptr rp, mp_srcptr up, mp_size_t n, mp_limb_t vl) |
| { |
| mp_limb_t cy[n]; |
| mp_limb_t a, b, r, s0, s1, c0, c1; |
| mp_size_t i; |
| int more_carries; |
| |
| if (up == rp) |
| { |
| /* The algorithm used below cannot handle overlap. Handle it here by |
| making a temporary copy of the source vector, then call ourselves. */ |
| mp_limb_t xp[n]; |
| MPN_COPY (xp, up, n); |
| return mpn_submul_1 (rp, xp, n, vl); |
| } |
| |
| a = up[0] * vl; |
| r = rp[0]; |
| s0 = r - a; |
| rp[0] = s0; |
| c1 = ((s0 & a) | ((s0 | a) & ~r)) >> 63; |
| cy[0] = c1; |
| |
| /* Main multiply loop. Generate a raw accumulated output product in rp[] |
| and a carry vector in cy[]. */ |
| #pragma _CRI ivdep |
| for (i = 1; i < n; i++) |
| { |
| a = up[i] * vl; |
| b = _int_mult_upper (up[i - 1], vl); |
| s0 = a + b; |
| c0 = ((a & b) | ((a | b) & ~s0)) >> 63; |
| r = rp[i]; |
| s1 = r - s0; |
| rp[i] = s1; |
| c1 = ((s1 & s0) | ((s1 | s0) & ~r)) >> 63; |
| cy[i] = c0 + c1; |
| } |
| /* Carry subtract loop. Subtract the carry vector cy[] from the raw result |
| rp[] and store the new result back to rp[]. */ |
| 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 = (s0 & ~r) >> 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] == ~0 and cy[k-1] == 1 or |
| rp[k] == ~1 and cy[k-1] == 2. |
| These are where we got a recurrency carry. */ |
| for (i = 1; i < n; i++) |
| { |
| r = rp[i]; |
| c0 = ~r < cy[i - 1]; |
| s0 = r - cyrec; |
| rp[i] = s0; |
| c1 = (s0 & ~r) >> 63; |
| cyrec = c0 | c1; |
| } |
| return _int_mult_upper (up[n - 1], vl) + cyrec + cy[n - 1]; |
| } |
| |
| return _int_mult_upper (up[n - 1], vl) + cy[n - 1]; |
| } |