Imported gcc-4.4.3

[msp430-gcc.git] / gmp / mpn / generic / bdivmod.c

diff --git a/gmp/mpn/generic/bdivmod.c b/gmp/mpn/generic/bdivmod.c
new file mode 100644 (file)
index 0000000..783b594
--- /dev/null
+++ b/gmp/mpn/generic/bdivmod.c
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+/* mpn/bdivmod.c: mpn_bdivmod for computing U/V mod 2^d.
+
+Copyright 1991, 1993, 1994, 1995, 1996, 1999, 2000, 2001, 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 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.
+
+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.  If not, see http://www.gnu.org/licenses/.  */
+
+/* q_high = mpn_bdivmod (qp, up, usize, vp, vsize, d).
+
+   Puts the low d/BITS_PER_MP_LIMB limbs of Q = U / V mod 2^d at qp, and
+   returns the high d%BITS_PER_MP_LIMB bits of Q as the result.
+
+   Also, U - Q * V mod 2^(usize*BITS_PER_MP_LIMB) is placed at up.  Since the
+   low d/BITS_PER_MP_LIMB limbs of this difference are zero, the code allows
+   the limb vectors at qp to overwrite the low limbs at up, provided qp <= up.
+
+   Preconditions:
+   1.  V is odd.
+   2.  usize * BITS_PER_MP_LIMB >= d.
+   3.  If Q and U overlap, qp <= up.
+
+   Ken Weber (kweber@mat.ufrgs.br, kweber@mcs.kent.edu)
+
+   Funding for this work has been partially provided by Conselho Nacional
+   de Desenvolvimento Cienti'fico e Tecnolo'gico (CNPq) do Brazil, Grant
+   301314194-2, and was done while I was a visiting reseacher in the Instituto
+   de Matema'tica at Universidade Federal do Rio Grande do Sul (UFRGS).
+
+   References:
+       T. Jebelean, An algorithm for exact division, Journal of Symbolic
+       Computation, v. 15, 1993, pp. 169-180.
+
+       K. Weber, The accelerated integer GCD algorithm, ACM Transactions on
+       Mathematical Software, v. 21 (March), 1995, pp. 111-122.  */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+
+mp_limb_t
+mpn_bdivmod (mp_ptr qp, mp_ptr up, mp_size_t usize,
+            mp_srcptr vp, mp_size_t vsize, unsigned long int d)
+{
+  mp_limb_t v_inv;
+
+  ASSERT (usize >= 1);
+  ASSERT (vsize >= 1);
+  ASSERT (usize * GMP_NUMB_BITS >= d);
+  ASSERT (! MPN_OVERLAP_P (up, usize, vp, vsize));
+  ASSERT (! MPN_OVERLAP_P (qp, d/GMP_NUMB_BITS, vp, vsize));
+  ASSERT (MPN_SAME_OR_INCR2_P (qp, d/GMP_NUMB_BITS, up, usize));
+  ASSERT_MPN (up, usize);
+  ASSERT_MPN (vp, vsize);
+
+  /* 1/V mod 2^GMP_NUMB_BITS. */
+  binvert_limb (v_inv, vp[0]);
+
+  /* Fast code for two cases previously used by the accel part of mpn_gcd.
+     (Could probably remove this now it's inlined there.) */
+  if (usize == 2 && vsize == 2 &&
+      (d == GMP_NUMB_BITS || d == 2*GMP_NUMB_BITS))
+    {
+      mp_limb_t hi, lo;
+      mp_limb_t q = (up[0] * v_inv) & GMP_NUMB_MASK;
+      umul_ppmm (hi, lo, q, vp[0] << GMP_NAIL_BITS);
+      up[0] = 0;
+      up[1] -= hi + q*vp[1];
+      qp[0] = q;
+      if (d == 2*GMP_NUMB_BITS)
+        {
+          q = (up[1] * v_inv) & GMP_NUMB_MASK;
+          up[1] = 0;
+          qp[1] = q;
+        }
+      return 0;
+    }
+
+  /* Main loop.  */
+  while (d >= GMP_NUMB_BITS)
+    {
+      mp_limb_t q = (up[0] * v_inv) & GMP_NUMB_MASK;
+      mp_limb_t b = mpn_submul_1 (up, vp, MIN (usize, vsize), q);
+      if (usize > vsize)
+       mpn_sub_1 (up + vsize, up + vsize, usize - vsize, b);
+      d -= GMP_NUMB_BITS;
+      up += 1, usize -= 1;
+      *qp++ = q;
+    }
+
+  if (d)
+    {
+      mp_limb_t b;
+      mp_limb_t q = (up[0] * v_inv) & (((mp_limb_t)1<<d) - 1);
+      if (q <= 1)
+       {
+         if (q == 0)
+           return 0;
+         else
+           b = mpn_sub_n (up, up, vp, MIN (usize, vsize));
+       }
+      else
+       b = mpn_submul_1 (up, vp, MIN (usize, vsize), q);
+
+      if (usize > vsize)
+       mpn_sub_1 (up + vsize, up + vsize, usize - vsize, b);
+      return q;
+    }
+
+  return 0;
+}