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Change-Id: Iae65e95cfa0d92091b8b0a424ae36d88efa76aa9 Reviewed-on: https://review.haiku-os.org/c/buildtools/+/3020 Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>
119 lines
3.2 KiB
C
119 lines
3.2 KiB
C
/* mpn_divrem_2 -- Divide natural numbers, producing both remainder and
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quotient. The divisor is two limbs.
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THIS FILE CONTAINS INTERNAL FUNCTIONS WITH MUTABLE INTERFACES. IT IS ONLY
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SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
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GUARANTEED THAT THEY'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
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Copyright 1993-1996, 1999-2002 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of either:
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* the GNU Lesser General Public License as published by the Free
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Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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or
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* the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any
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later version.
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or both in parallel, as here.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received copies of the GNU General Public License and the
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GNU Lesser General Public License along with the GNU MP Library. If not,
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see https://www.gnu.org/licenses/. */
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#include "gmp-impl.h"
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#include "longlong.h"
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/* Divide num {np,nn} by den {dp,2} and write the nn-2 least significant
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quotient limbs at qp and the 2 long remainder at np. If qxn is non-zero,
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generate that many fraction bits and append them after the other quotient
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limbs. Return the most significant limb of the quotient, this is always 0
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or 1.
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Preconditions:
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1. The most significant bit of the divisor must be set.
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2. qp must either not overlap with the input operands at all, or
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qp >= np + 2 must hold true. (This means that it's possible to put
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the quotient in the high part of {np,nn}, right above the remainder.
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3. nn >= 2, even if qxn is non-zero. */
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mp_limb_t
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mpn_divrem_2 (mp_ptr qp, mp_size_t qxn,
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mp_ptr np, mp_size_t nn,
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mp_srcptr dp)
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{
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mp_limb_t most_significant_q_limb;
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mp_size_t i;
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mp_limb_t r1, r0, d1, d0;
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gmp_pi1_t di;
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ASSERT (nn >= 2);
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ASSERT (qxn >= 0);
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ASSERT (dp[1] & GMP_NUMB_HIGHBIT);
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ASSERT (! MPN_OVERLAP_P (qp, nn-2+qxn, np, nn) || qp >= np+2);
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ASSERT_MPN (np, nn);
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ASSERT_MPN (dp, 2);
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np += nn - 2;
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d1 = dp[1];
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d0 = dp[0];
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r1 = np[1];
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r0 = np[0];
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most_significant_q_limb = 0;
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if (r1 >= d1 && (r1 > d1 || r0 >= d0))
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{
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#if GMP_NAIL_BITS == 0
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sub_ddmmss (r1, r0, r1, r0, d1, d0);
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#else
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r0 = r0 - d0;
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r1 = r1 - d1 - (r0 >> GMP_LIMB_BITS - 1);
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r0 &= GMP_NUMB_MASK;
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#endif
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most_significant_q_limb = 1;
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}
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invert_pi1 (di, d1, d0);
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qp += qxn;
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for (i = nn - 2 - 1; i >= 0; i--)
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{
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mp_limb_t n0, q;
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n0 = np[-1];
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udiv_qr_3by2 (q, r1, r0, r1, r0, n0, d1, d0, di.inv32);
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np--;
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qp[i] = q;
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}
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if (UNLIKELY (qxn != 0))
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{
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qp -= qxn;
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for (i = qxn - 1; i >= 0; i--)
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{
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mp_limb_t q;
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udiv_qr_3by2 (q, r1, r0, r1, r0, CNST_LIMB(0), d1, d0, di.inv32);
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qp[i] = q;
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}
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}
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np[1] = r1;
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np[0] = r0;
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return most_significant_q_limb;
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}
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