Imported gcc-4.4.3

[msp430-gcc.git] / gmp / mpn / generic / gcd_1.c

diff --git a/gmp/mpn/generic/gcd_1.c b/gmp/mpn/generic/gcd_1.c
new file mode 100644 (file)
index 0000000..73be151
--- /dev/null
+++ b/gmp/mpn/generic/gcd_1.c
@@ -0,0 +1,115 @@
+/* mpn_gcd_1 -- mpn and limb greatest common divisor.
+
+Copyright 1994, 1996, 2000, 2001 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/.  */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+
+/* Does not work for U == 0 or V == 0.  It would be tough to make it work for
+   V == 0 since gcd(x,0) = x, and U does not generally fit in an mp_limb_t.
+
+   The threshold for doing u%v when size==1 will vary by CPU according to
+   the speed of a division and the code generated for the main loop.  Any
+   tuning for this is left to a CPU specific implementation.  */
+
+mp_limb_t
+mpn_gcd_1 (mp_srcptr up, mp_size_t size, mp_limb_t vlimb)
+{
+  mp_limb_t      ulimb;
+  unsigned long  zero_bits, u_low_zero_bits;
+
+  ASSERT (size >= 1);
+  ASSERT (vlimb != 0);
+  ASSERT_MPN_NONZERO_P (up, size);
+
+  ulimb = up[0];
+
+  /* Need vlimb odd for modexact, want it odd to get common zeros. */
+  count_trailing_zeros (zero_bits, vlimb);
+  vlimb >>= zero_bits;
+
+  if (size > 1)
+    {
+      /* Must get common zeros before the mod reduction.  If ulimb==0 then
+        vlimb already gives the common zeros.  */
+      if (ulimb != 0)
+       {
+         count_trailing_zeros (u_low_zero_bits, ulimb);
+         zero_bits = MIN (zero_bits, u_low_zero_bits);
+       }
+
+      ulimb = MPN_MOD_OR_MODEXACT_1_ODD (up, size, vlimb);
+      if (ulimb == 0)
+       goto done;
+
+      goto strip_u_maybe;
+    }
+
+  /* size==1, so up[0]!=0 */
+  count_trailing_zeros (u_low_zero_bits, ulimb);
+  ulimb >>= u_low_zero_bits;
+  zero_bits = MIN (zero_bits, u_low_zero_bits);
+
+  /* make u bigger */
+  if (vlimb > ulimb)
+    MP_LIMB_T_SWAP (ulimb, vlimb);
+
+  /* if u is much bigger than v, reduce using a division rather than
+     chipping away at it bit-by-bit */
+  if ((ulimb >> 16) > vlimb)
+    {
+      ulimb %= vlimb;
+      if (ulimb == 0)
+       goto done;
+      goto strip_u_maybe;
+    }
+
+  while (ulimb != vlimb)
+    {
+      ASSERT (ulimb & 1);
+      ASSERT (vlimb & 1);
+
+      if (ulimb > vlimb)
+       {
+         ulimb -= vlimb;
+         do
+           {
+             ulimb >>= 1;
+             ASSERT (ulimb != 0);
+           strip_u_maybe:
+             ;
+           }
+         while ((ulimb & 1) == 0);
+       }
+      else /*  vlimb > ulimb.  */
+       {
+         vlimb -= ulimb;
+         do
+           {
+             vlimb >>= 1;
+             ASSERT (vlimb != 0);
+           }
+         while ((vlimb & 1) == 0);
+       }
+    }
+
+ done:
+  return vlimb << zero_bits;
+}