Imported gcc-4.4.3

[msp430-gcc.git] / gmp / mpz / divexact.c

diff --git a/gmp/mpz/divexact.c b/gmp/mpz/divexact.c
new file mode 100644 (file)
index 0000000..e7d9d00
--- /dev/null
+++ b/gmp/mpz/divexact.c
@@ -0,0 +1,134 @@
+/* mpz_divexact -- finds quotient when known that quot * den == num && den != 0.
+
+Copyright 1991, 1993, 1994, 1995, 1996, 1997, 1998, 2000, 2001, 2002, 2005,
+2006, 2007 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/.  */
+
+/*  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.  */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+void
+mpz_divexact (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den)
+{
+  mp_ptr qp, tp;
+  mp_size_t qsize, tsize;
+  mp_srcptr np, dp;
+  mp_size_t nsize, dsize;
+  TMP_DECL;
+
+#if WANT_ASSERT
+  {
+    mpz_t  rem;
+    mpz_init (rem);
+    mpz_tdiv_r (rem, num, den);
+    ASSERT (SIZ(rem) == 0);
+    mpz_clear (rem);
+  }
+#endif
+
+  nsize = ABS (num->_mp_size);
+  dsize = ABS (den->_mp_size);
+
+  qsize = nsize - dsize + 1;
+  if (quot->_mp_alloc < qsize)
+    _mpz_realloc (quot, qsize);
+
+  np = num->_mp_d;
+  dp = den->_mp_d;
+  qp = quot->_mp_d;
+
+  if (nsize < dsize)
+    {
+      /* This special case avoids segfaults below when the function is
+        incorrectly called with |N| < |D|, N != 0.  It also handles the
+        well-defined case N = 0.  */
+      quot->_mp_size = 0;
+      return;
+    }
+
+  if (dsize <= 1)
+    {
+      if (dsize == 1)
+       {
+         MPN_DIVREM_OR_DIVEXACT_1 (qp, np, nsize, dp[0]);
+         qsize -= qp[qsize - 1] == 0;
+         quot->_mp_size = (num->_mp_size ^ den->_mp_size) >= 0 ? qsize : -qsize;
+         return;
+       }
+
+      /*  Generate divide-by-zero error since dsize == 0.  */
+      DIVIDE_BY_ZERO;
+    }
+
+  /* Avoid quadratic behaviour, but do it conservatively.  */
+  if (qsize > 1500)
+    {
+      mpz_tdiv_q (quot, num, den);
+      return;
+    }
+
+  TMP_MARK;
+
+  /*  QUOT <-- NUM/2^r, T <-- DEN/2^r where = r number of twos in DEN.  */
+  while (dp[0] == 0)
+    np += 1, nsize -= 1, dp += 1, dsize -= 1;
+  tsize = MIN (qsize, dsize);
+  if ((dp[0] & 1) != 0)
+    {
+      if (quot == den)         /*  QUOT and DEN overlap.  */
+       {
+         tp = (mp_ptr) TMP_ALLOC (tsize * BYTES_PER_MP_LIMB);
+         MPN_COPY (tp, dp, tsize);
+       }
+      else
+       tp = (mp_ptr) dp;
+      if (qp != np)
+       MPN_COPY_INCR (qp, np, qsize);
+    }
+  else
+    {
+      unsigned int r;
+      tp = (mp_ptr) TMP_ALLOC (tsize * BYTES_PER_MP_LIMB);
+      count_trailing_zeros (r, dp[0]);
+      mpn_rshift (tp, dp, tsize, r);
+      if (dsize > tsize)
+       tp[tsize - 1] |= (dp[tsize] << (GMP_NUMB_BITS - r)) & GMP_NUMB_MASK;
+      mpn_rshift (qp, np, qsize, r);
+      if (nsize > qsize)
+       qp[qsize - 1] |= (np[qsize] << (GMP_NUMB_BITS - r)) & GMP_NUMB_MASK;
+    }
+
+  /*  Now QUOT <-- QUOT/T.  */
+  mpn_bdivmod (qp, qp, qsize, tp, tsize, qsize * GMP_NUMB_BITS);
+  MPN_NORMALIZE (qp, qsize);
+
+  quot->_mp_size = (num->_mp_size ^ den->_mp_size) >= 0 ? qsize : -qsize;
+
+  TMP_FREE;
+}