+++ /dev/null
-/* __mpn_divmod -- Divide natural numbers, producing both remainder and
- quotient.
-
-Copyright (C) 1993, 1994 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 Library General Public License as published by
-the Free Software Foundation; either version 2 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 Library General Public
-License for more details.
-
-You should have received a copy of the GNU Library General Public License
-along with the GNU MP Library; see the file COPYING.LIB. If not, write to
-the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
-
-#include "gmp.h"
-#include "gmp-impl.h"
-#include "longlong.h"
-
-/* Divide num (NUM_PTR/NUM_SIZE) by den (DEN_PTR/DEN_SIZE) and write
- the NUM_SIZE-DEN_SIZE least significant quotient limbs at QUOT_PTR
- and the DEN_SIZE long remainder at NUM_PTR.
- Return the most significant limb of the quotient, this is always 0 or 1.
-
- Argument constraints:
- 1. The most significant bit of the divisor must be set.
- 2. QUOT_PTR must either not overlap with the input operands at all, or
- QUOT_PTR + DEN_SIZE >= NUM_PTR 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. */
-
-mp_limb
-#if __STDC__
-__mpn_divmod (mp_ptr quot_ptr,
- mp_ptr num_ptr, mp_size_t num_size,
- mp_srcptr den_ptr, mp_size_t den_size)
-#else
-__mpn_divmod (quot_ptr, num_ptr, num_size, den_ptr, den_size)
- mp_ptr quot_ptr;
- mp_ptr num_ptr;
- mp_size_t num_size;
- mp_srcptr den_ptr;
- mp_size_t den_size;
-#endif
-{
- mp_limb most_significant_q_limb = 0;
-
- switch (den_size)
- {
- case 0:
- /* We are asked to divide by zero, so go ahead and do it! (To make
- the compiler not remove this statement, return the value.) */
- return 1 / den_size;
-
- case 1:
- {
- mp_size_t i;
- mp_limb n1, n0;
- mp_limb d;
-
- d = den_ptr[0];
- n1 = num_ptr[num_size - 1];
-
- if (n1 >= d)
- {
- most_significant_q_limb = 1;
- n1 -= d;
- }
-
- for (i = num_size - 2; i >= 0; i--)
- {
- n0 = num_ptr[i];
- udiv_qrnnd (quot_ptr[i], n1, n1, n0, d);
- }
-
- num_ptr[0] = n1;
- }
- break;
-
- case 2:
- {
- mp_size_t i;
- mp_limb n1, n0, n2;
- mp_limb d1, d0;
-
- num_ptr += num_size - 2;
- d1 = den_ptr[1];
- d0 = den_ptr[0];
- n1 = num_ptr[1];
- n0 = num_ptr[0];
-
- if (n1 >= d1 && (n1 > d1 || n0 >= d0))
- {
- most_significant_q_limb = 1;
- sub_ddmmss (n1, n0, n1, n0, d1, d0);
- }
-
- for (i = num_size - den_size - 1; i >= 0; i--)
- {
- mp_limb q;
- mp_limb r;
-
- num_ptr--;
- 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) 0;
-
- r = n0 + d1;
- if (r < d1) /* Carry in the addition? */
- {
- add_ssaaaa (n1, n0, r - d0, num_ptr[0], 0, d0);
- quot_ptr[i] = q;
- continue;
- }
- n1 = d0 - (d0 != 0);
- n0 = -d0;
- }
- else
- {
- udiv_qrnnd (q, r, n1, n0, d1);
- umul_ppmm (n1, n0, d0, q);
- }
-
- n2 = num_ptr[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;
- }
-
- quot_ptr[i] = q;
- sub_ddmmss (n1, n0, r, n2, n1, n0);
- }
- num_ptr[1] = n1;
- num_ptr[0] = n0;
- }
- break;
-
- default:
- {
- mp_size_t i;
- mp_limb dX, d1, n0;
-
- num_ptr += num_size;
- den_ptr += den_size;
- dX = den_ptr[-1];
- d1 = den_ptr[-2];
- n0 = num_ptr[-1];
-
- if (n0 >= dX)
- {
- if (n0 > dX
- || __mpn_cmp (num_ptr - den_size, den_ptr - den_size,
- den_size - 1) >= 0)
- {
- __mpn_sub_n (num_ptr - den_size,
- num_ptr - den_size, den_ptr - den_size,
- den_size);
- most_significant_q_limb = 1;
- }
-
- n0 = num_ptr[-1];
- }
-
- for (i = num_size - den_size - 1; i >= 0; i--)
- {
- mp_limb q;
- mp_limb n1;
- mp_limb cy_limb;
-
- num_ptr--;
- if (n0 == dX)
- /* This might over-estimate q, but it's probably not worth
- the extra code here to find out. */
- q = ~(mp_limb) 0;
- else
- {
- mp_limb r;
-
- udiv_qrnnd (q, r, n0, num_ptr[-1], dX);
- umul_ppmm (n1, n0, d1, q);
-
- while (n1 > r || (n1 == r && n0 > num_ptr[-2]))
- {
- q--;
- r += dX;
- if (r < dX) /* I.e. "carry in previous addition?" */
- break;
- n1 -= n0 < d1;
- n0 -= d1;
- }
- }
-
- /* Possible optimization: We already have (q * n0) and (1 * n1)
- after the calculation of q. Taking advantage of that, we
- could make this loop make two iterations less. */
-
- cy_limb = __mpn_submul_1 (num_ptr - den_size,
- den_ptr - den_size, den_size, q);
-
- if (num_ptr[0] != cy_limb)
- {
- mp_limb cy;
- cy = __mpn_add_n (num_ptr - den_size,
- num_ptr - den_size,
- den_ptr - den_size, den_size);
- if (cy == 0)
- abort ();
- q--;
- }
-
- quot_ptr[i] = q;
- n0 = num_ptr[-1];
- }
- }
- }
-
- return most_significant_q_limb;
-}
projects / platform / upstream / glibc.git / commitdiff