mul_1.c
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上传日期:2022-08-06
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- /* Cray PVP/IEEE mpn_mul_1 -- multiply a limb vector with a limb and store the
- result in a second limb vector.
- Copyright 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 5 cycles/limb on a T90. That would probably
- be hard to improve upon, even with assembly code. */
- #include <intrinsics.h>
- #include "gmp.h"
- #include "gmp-impl.h"
- mp_limb_t
- mpn_mul_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_mul_1 (rp, xp, n, vl);
- }
- a = up[0] * vl;
- rp[0] = a;
- cy[0] = 0;
- /* 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;
- rp[i] = s0;
- 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]. */
- more_carries = 0;
- #pragma _CRI ivdep
- for (i = 2; 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 = 2; 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 _int_mult_upper (up[n - 1], vl) + cyrec + cy[n - 1];
- }
- return _int_mult_upper (up[n - 1], vl) + cy[n - 1];
- }