+++ /dev/null
-/* mpn/bdivmod.c: mpn_bdivmod for computing U/V mod 2^d.
-
-Copyright (C) 1991, 1993, 1994, 1995, 1996, 1999, 2000 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 2.1 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; see the file COPYING.LIB. If not, write to
-the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
-MA 02111-1307, USA. */
-
-/* q_high = mpn_bdivmod (qp, up, usize, vp, vsize, d).
-
- Puts the low d/BITS_PER_MP_LIMB limbs of Q = U / V mod 2^d at qp, and
- returns the high d%BITS_PER_MP_LIMB bits of Q as the result.
-
- Also, U - Q * V mod 2^(usize*BITS_PER_MP_LIMB) is placed at up. Since the
- low d/BITS_PER_MP_LIMB limbs of this difference are zero, the code allows
- the limb vectors at qp to overwrite the low limbs at up, provided qp <= up.
-
- Preconditions:
- 1. V is odd.
- 2. usize * BITS_PER_MP_LIMB >= d.
- 3. If Q and U overlap, qp <= up.
-
- Ken Weber (kweber@mat.ufrgs.br, kweber@mcs.kent.edu)
-
- Funding for this work has been partially provided by Conselho Nacional
- de Desenvolvimento Cienti'fico e Tecnolo'gico (CNPq) do Brazil, Grant
- 301314194-2, and was done while I was a visiting reseacher in the Instituto
- de Matema'tica at Universidade Federal do Rio Grande do Sul (UFRGS).
-
- References:
- T. Jebelean, An algorithm for exact division, Journal of Symbolic
- Computation, v. 15, 1993, pp. 169-180.
-
- K. Weber, The accelerated integer GCD algorithm, ACM Transactions on
- Mathematical Software, v. 21 (March), 1995, pp. 111-122. */
-
-#include "gmp.h"
-#include "gmp-impl.h"
-#include "longlong.h"
-
-mp_limb_t
-#if __STDC__
-mpn_bdivmod (mp_ptr qp, mp_ptr up, mp_size_t usize,
- mp_srcptr vp, mp_size_t vsize, unsigned long int d)
-#else
-mpn_bdivmod (qp, up, usize, vp, vsize, d)
- mp_ptr qp;
- mp_ptr up;
- mp_size_t usize;
- mp_srcptr vp;
- mp_size_t vsize;
- unsigned long int d;
-#endif
-{
- mp_limb_t v_inv;
-
- /* 1/V mod 2^BITS_PER_MP_LIMB. */
- modlimb_invert (v_inv, vp[0]);
-
- /* Fast code for two cases previously used by the accel part of mpn_gcd.
- (Could probably remove this now it's inlined there.) */
- if (usize == 2 && vsize == 2 &&
- (d == BITS_PER_MP_LIMB || d == 2*BITS_PER_MP_LIMB))
- {
- mp_limb_t hi, lo;
- mp_limb_t q = up[0] * v_inv;
- umul_ppmm (hi, lo, q, vp[0]);
- up[0] = 0, up[1] -= hi + q*vp[1], qp[0] = q;
- if (d == 2*BITS_PER_MP_LIMB)
- q = up[1] * v_inv, up[1] = 0, qp[1] = q;
- return 0;
- }
-
- /* Main loop. */
- while (d >= BITS_PER_MP_LIMB)
- {
- mp_limb_t q = up[0] * v_inv;
- mp_limb_t b = mpn_submul_1 (up, vp, MIN (usize, vsize), q);
- if (usize > vsize)
- mpn_sub_1 (up + vsize, up + vsize, usize - vsize, b);
- d -= BITS_PER_MP_LIMB;
- up += 1, usize -= 1;
- *qp++ = q;
- }
-
- if (d)
- {
- mp_limb_t b;
- mp_limb_t q = (up[0] * v_inv) & (((mp_limb_t)1<<d) - 1);
- if (q <= 1)
- {
- if (q == 0)
- return 0;
- else
- b = mpn_sub_n (up, up, vp, MIN (usize, vsize));
- }
- else
- b = mpn_submul_1 (up, vp, MIN (usize, vsize), q);
-
- if (usize > vsize)
- mpn_sub_1 (up + vsize, up + vsize, usize - vsize, b);
- return q;
- }
-
- return 0;
-}
projects / ghc-hetmet.git / blobdiff