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+/* 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 1993-1996, 1999-2002 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 either:
+
+ * the GNU Lesser General Public License as published by the Free
+ Software Foundation; either version 3 of the License, or (at your
+ option) any later version.
+
+or
+
+ * the GNU General Public License as published by the Free Software
+ Foundation; either version 2 of the License, or (at your option) any
+ later version.
+
+or both in parallel, as here.
+
+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 General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library. If not,
+see https://www.gnu.org/licenses/. */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+
+/* Divide num {np,nn} by den {dp,2} and write the nn-2 least significant
+ quotient limbs at qp and the 2 long remainder at np. If qxn 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:
+ 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 >= np + 2 must hold true. (This means that it's possible to put
+ the quotient in the high part of {np,nn}, right above the remainder.
+ 3. nn >= 2, even if qxn is non-zero. */
+
+mp_limb_t
+mpn_divrem_2 (mp_ptr qp, mp_size_t qxn,
+ mp_ptr np, mp_size_t nn,
+ mp_srcptr dp)
+{
+ mp_limb_t most_significant_q_limb;
+ mp_size_t i;
+ mp_limb_t r1, r0, d1, d0;
+ gmp_pi1_t di;
+
+ ASSERT (nn >= 2);
+ ASSERT (qxn >= 0);
+ ASSERT (dp[1] & GMP_NUMB_HIGHBIT);
+ ASSERT (! MPN_OVERLAP_P (qp, nn-2+qxn, np, nn) || qp >= np+2);
+ ASSERT_MPN (np, nn);
+ ASSERT_MPN (dp, 2);
+
+ np += nn - 2;
+ d1 = dp[1];
+ d0 = dp[0];
+ r1 = np[1];
+ r0 = np[0];
+
+ most_significant_q_limb = 0;
+ if (r1 >= d1 && (r1 > d1 || r0 >= d0))
+ {
+#if GMP_NAIL_BITS == 0
+ sub_ddmmss (r1, r0, r1, r0, d1, d0);
+#else
+ r0 = r0 - d0;
+ r1 = r1 - d1 - (r0 >> GMP_LIMB_BITS - 1);
+ r0 &= GMP_NUMB_MASK;
+#endif
+ most_significant_q_limb = 1;
+ }
+
+ invert_pi1 (di, d1, d0);
+
+ qp += qxn;
+
+ for (i = nn - 2 - 1; i >= 0; i--)
+ {
+ mp_limb_t n0, q;
+ n0 = np[-1];
+ udiv_qr_3by2 (q, r1, r0, r1, r0, n0, d1, d0, di.inv32);
+ np--;
+ qp[i] = q;
+ }
+
+ if (UNLIKELY (qxn != 0))
+ {
+ qp -= qxn;
+ for (i = qxn - 1; i >= 0; i--)
+ {
+ mp_limb_t q;
+ udiv_qr_3by2 (q, r1, r0, r1, r0, CNST_LIMB(0), d1, d0, di.inv32);
+ qp[i] = q;
+ }
+ }
+
+ np[1] = r1;
+ np[0] = r0;
+
+ return most_significant_q_limb;
+}