+++ /dev/null
-/* mpn_divrem_2 -- Divide natural numbers, producing both remainder and
- quotient. The divisor is two limbs.
-
- THIS FILE CONTAINS INTERNAL FUNCTIONS WITH MUTABLE INTERFACES. IT IS
- ONLY SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS
- ALMOST GUARANTEED THAT THEY'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP
- RELEASE.
-
-
-Copyright (C) 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. */
-
-#include "gmp.h"
-#include "gmp-impl.h"
-#include "longlong.h"
-
-/* Divide num (NP/NSIZE) by den (DP/2) and write
- the NSIZE-2 least significant quotient limbs at QP
- and the 2 long remainder at NP. If QEXTRA_LIMBS is
- non-zero, generate that many fraction bits and append them after the
- other quotient limbs.
- Return the most significant limb of the quotient, this is always 0 or 1.
-
- Preconditions:
- 0. NSIZE >= 2.
- 1. The most significant bit of the divisor must be set.
- 2. QP must either not overlap with the input operands at all, or
- QP + 2 >= NP must hold true. (This means that it's
- possible to put the quotient in the high part of NUM, right after the
- remainder in NUM.
- 3. NSIZE >= 2, even if QEXTRA_LIMBS is non-zero. */
-
-mp_limb_t
-#if __STDC__
-mpn_divrem_2 (mp_ptr qp, mp_size_t qxn,
- mp_ptr np, mp_size_t nsize,
- mp_srcptr dp)
-#else
-mpn_divrem_2 (qp, qxn, np, nsize, dp)
- mp_ptr qp;
- mp_size_t qxn;
- mp_ptr np;
- mp_size_t nsize;
- mp_srcptr dp;
-#endif
-{
- mp_limb_t most_significant_q_limb = 0;
- mp_size_t i;
- mp_limb_t n1, n0, n2;
- mp_limb_t d1, d0;
- mp_limb_t d1inv;
- int have_preinv;
-
- np += nsize - 2;
- d1 = dp[1];
- d0 = dp[0];
- n1 = np[1];
- n0 = np[0];
-
- if (n1 >= d1 && (n1 > d1 || n0 >= d0))
- {
- sub_ddmmss (n1, n0, n1, n0, d1, d0);
- most_significant_q_limb = 1;
- }
-
- /* If multiplication is much faster than division, preinvert the most
- significant divisor limb before entering the loop. */
- if (UDIV_TIME > 2 * UMUL_TIME + 6)
- {
- have_preinv = 0;
- if ((UDIV_TIME - (2 * UMUL_TIME + 6)) * (nsize - 2) > UDIV_TIME)
- {
- invert_limb (d1inv, d1);
- have_preinv = 1;
- }
- }
-
- for (i = qxn + nsize - 2 - 1; i >= 0; i--)
- {
- mp_limb_t q;
- mp_limb_t r;
-
- if (i >= qxn)
- np--;
- else
- np[0] = 0;
-
- if (n1 == d1)
- {
- /* Q should be either 111..111 or 111..110. Need special treatment
- of this rare case as normal division would give overflow. */
- q = ~(mp_limb_t) 0;
-
- r = n0 + d1;
- if (r < d1) /* Carry in the addition? */
- {
- add_ssaaaa (n1, n0, r - d0, np[0], 0, d0);
- qp[i] = q;
- continue;
- }
- n1 = d0 - (d0 != 0);
- n0 = -d0;
- }
- else
- {
- if (UDIV_TIME > 2 * UMUL_TIME + 6 && have_preinv)
- udiv_qrnnd_preinv (q, r, n1, n0, d1, d1inv);
- else
- udiv_qrnnd (q, r, n1, n0, d1);
- umul_ppmm (n1, n0, d0, q);
- }
-
- n2 = np[0];
-
- q_test:
- if (n1 > r || (n1 == r && n0 > n2))
- {
- /* The estimated Q was too large. */
- q--;
-
- sub_ddmmss (n1, n0, n1, n0, 0, d0);
- r += d1;
- if (r >= d1) /* If not carry, test Q again. */
- goto q_test;
- }
-
- qp[i] = q;
- sub_ddmmss (n1, n0, r, n2, n1, n0);
- }
- np[1] = n1;
- np[0] = n0;
-
- return most_significant_q_limb;
-}
projects / ghc-hetmet.git / blobdiff