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-rw-r--r--stdlib/divrem.c245
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diff --git a/stdlib/divrem.c b/stdlib/divrem.c
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--- a/stdlib/divrem.c
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-/* mpn_divrem -- Divide natural numbers, producing both remainder and
- quotient.
-
-Copyright (C) 1993, 1994, 1995, 1996 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/DSIZE) and write
- the NSIZE-DSIZE least significant quotient limbs at QP
- and the DSIZE 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 >= DSIZE.
- 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 + DSIZE >= 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 >= DSIZE, even if QEXTRA_LIMBS is non-zero. */
-
-mp_limb_t
-#if __STDC__
-mpn_divrem (mp_ptr qp, mp_size_t qextra_limbs,
- mp_ptr np, mp_size_t nsize,
- mp_srcptr dp, mp_size_t dsize)
-#else
-mpn_divrem (qp, qextra_limbs, np, nsize, dp, dsize)
- mp_ptr qp;
- mp_size_t qextra_limbs;
- mp_ptr np;
- mp_size_t nsize;
- mp_srcptr dp;
- mp_size_t dsize;
-#endif
-{
- mp_limb_t most_significant_q_limb = 0;
-
- switch (dsize)
- {
- 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 / dsize;
-
- case 1:
- {
- mp_size_t i;
- mp_limb_t n1;
- mp_limb_t d;
-
- d = dp[0];
- n1 = np[nsize - 1];
-
- if (n1 >= d)
- {
- n1 -= d;
- most_significant_q_limb = 1;
- }
-
- qp += qextra_limbs;
- for (i = nsize - 2; i >= 0; i--)
- udiv_qrnnd (qp[i], n1, n1, np[i], d);
- qp -= qextra_limbs;
-
- for (i = qextra_limbs - 1; i >= 0; i--)
- udiv_qrnnd (qp[i], n1, n1, 0, d);
-
- np[0] = n1;
- }
- break;
-
- case 2:
- {
- mp_size_t i;
- mp_limb_t n1, n0, n2;
- mp_limb_t d1, d0;
-
- 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;
- }
-
- for (i = qextra_limbs + nsize - 2 - 1; i >= 0; i--)
- {
- mp_limb_t q;
- mp_limb_t r;
-
- if (i >= qextra_limbs)
- 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
- {
- 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;
- }
- break;
-
- default:
- {
- mp_size_t i;
- mp_limb_t dX, d1, n0;
-
- np += nsize - dsize;
- dX = dp[dsize - 1];
- d1 = dp[dsize - 2];
- n0 = np[dsize - 1];
-
- if (n0 >= dX)
- {
- if (n0 > dX || mpn_cmp (np, dp, dsize - 1) >= 0)
- {
- mpn_sub_n (np, np, dp, dsize);
- n0 = np[dsize - 1];
- most_significant_q_limb = 1;
- }
- }
-
- for (i = qextra_limbs + nsize - dsize - 1; i >= 0; i--)
- {
- mp_limb_t q;
- mp_limb_t n1, n2;
- mp_limb_t cy_limb;
-
- if (i >= qextra_limbs)
- {
- np--;
- n2 = np[dsize];
- }
- else
- {
- n2 = np[dsize - 1];
- MPN_COPY_DECR (np + 1, np, dsize);
- np[0] = 0;
- }
-
- if (n0 == dX)
- /* This might over-estimate q, but it's probably not worth
- the extra code here to find out. */
- q = ~(mp_limb_t) 0;
- else
- {
- mp_limb_t r;
-
- udiv_qrnnd (q, r, n0, np[dsize - 1], dX);
- umul_ppmm (n1, n0, d1, q);
-
- while (n1 > r || (n1 == r && n0 > np[dsize - 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 (np, dp, dsize, q);
-
- if (n2 != cy_limb)
- {
- mpn_add_n (np, np, dp, dsize);
- q--;
- }
-
- qp[i] = q;
- n0 = np[dsize - 1];
- }
- }
- }
-
- return most_significant_q_limb;
-}