Imported gcc-4.4.3

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

diff --git a/gmp/mpn/generic/dc_divrem_n.c b/gmp/mpn/generic/dc_divrem_n.c
new file mode 100644 (file)
index 0000000..61ddde7
--- /dev/null
+++ b/gmp/mpn/generic/dc_divrem_n.c
@@ -0,0 +1,121 @@
+/* mpn_dc_divrem_n and auxilliary routines.
+
+   THE FUNCTIONS IN THIS FILE ARE 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 2000, 2001, 2002, 2004, 2005 Free Software Foundation, Inc.
+Contributed by Paul Zimmermann.
+
+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/.  */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+
+/*
+[1] Fast Recursive Division, by Christoph Burnikel and Joachim Ziegler,
+    Technical report MPI-I-98-1-022, october 1998.
+    http://www.mpi-sb.mpg.de/~ziegler/TechRep.ps.gz
+*/
+
+static mp_limb_t mpn_dc_div_3_by_2
+  __GMP_PROTO ((mp_ptr qp, mp_ptr np, mp_srcptr dp, mp_size_t n, mp_ptr scratch));
+static mp_limb_t mpn_dc_div_2_by_1
+  __GMP_PROTO ((mp_ptr qp, mp_ptr np, mp_srcptr dp, mp_size_t n, mp_ptr scratch));
+
+/* mpn_dc_divrem_n - Implements algorithm of page 8 in [1]: divides (np,2n)
+   by (dp,n) and puts the quotient in (qp,n), the remainder in (np,n).
+   Returns most significant limb of the quotient, which is 0 or 1.
+   Requires that the most significant bit of the divisor is set.  */
+
+mp_limb_t
+mpn_dc_divrem_n (mp_ptr qp, mp_ptr np, mp_srcptr dp, mp_size_t n)
+{
+  mp_limb_t ret;
+  mp_ptr scratch;
+  TMP_DECL;
+  TMP_MARK;
+
+  scratch = TMP_ALLOC_LIMBS (n);
+  ret = mpn_dc_div_2_by_1 (qp, np, dp, n, scratch);
+
+  TMP_FREE;
+  return ret;
+}
+
+static mp_limb_t
+mpn_dc_div_2_by_1 (mp_ptr qp, mp_ptr np, mp_srcptr dp, mp_size_t n, mp_ptr scratch)
+{
+  mp_limb_t qhl, cc;
+  mp_size_t n2 = n/2;
+
+  if (n % 2 != 0)
+    {
+      mp_ptr qp1 = qp + 1;
+      qhl = mpn_dc_div_3_by_2 (qp1 + n2, np + 2 + n2, dp + 1, n2, scratch);
+      qhl += mpn_add_1 (qp1 + n2, qp1 + n2, n2,
+                       mpn_dc_div_3_by_2 (qp1, np + 2, dp + 1, n2, scratch));
+
+      cc = mpn_submul_1 (np + 1, qp1, n - 1, dp[0]);
+      cc = mpn_sub_1 (np + n, np + n, 1, cc);
+      if (qhl != 0)
+       cc += mpn_sub_1 (np + n, np + n, 1, dp[0]);
+      while (cc != 0)
+       {
+         qhl -= mpn_sub_1 (qp1, qp1, n - 1, (mp_limb_t) 1);
+         cc -= mpn_add_n (np + 1, np + 1, dp, n);
+       }
+      qhl += mpn_add_1 (qp1, qp1, n - 1,
+                       mpn_sb_divrem_mn (qp, np, n + 1, dp, n));
+    }
+  else
+    {
+      qhl = mpn_dc_div_3_by_2 (qp + n2, np + n2, dp, n2, scratch);
+      qhl += mpn_add_1 (qp + n2, qp + n2, n2,
+                       mpn_dc_div_3_by_2 (qp, np, dp, n2, scratch));
+    }
+  return qhl;
+}
+
+
+/* divides (np, 3n) by (dp, 2n) and puts the quotient in (qp, n),
+   the remainder in (np, 2n) */
+
+static mp_limb_t
+mpn_dc_div_3_by_2 (mp_ptr qp, mp_ptr np, mp_srcptr dp, mp_size_t n, mp_ptr scratch)
+{
+  mp_size_t twon = n + n;
+  mp_limb_t qhl, cc;
+
+  if (n < DIV_DC_THRESHOLD)
+    qhl = mpn_sb_divrem_mn (qp, np + n, twon, dp + n, n);
+  else
+    qhl = mpn_dc_div_2_by_1 (qp, np + n, dp + n, n, scratch);
+
+  mpn_mul_n (scratch, qp, dp, n);
+  cc = mpn_sub_n (np, np, scratch, twon);
+
+  if (qhl != 0)
+    cc += mpn_sub_n (np + n, np + n, dp, n);
+  while (cc != 0)
+    {
+      qhl -= mpn_sub_1 (qp, qp, n, (mp_limb_t) 1);
+      cc -= mpn_add_n (np, np, dp, twon);
+    }
+  return qhl;
+}