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diff --git a/mpfr/eq.c b/mpfr/eq.c
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+++ b/mpfr/eq.c
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+/* mpfr_eq -- Compare two floats up to a specified bit #.
+
+Copyright 1999, 2001, 2003, 2004, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+Contributed by the Arenaire and Cacao projects, INRIA.
+
+This file is part of the GNU MPFR Library.
+
+The GNU MPFR 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 2.1 of the License, or (at your
+option) any later version.
+
+The GNU MPFR 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 MPFR Library; see the file COPYING.LIB.  If not, write to
+the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
+MA 02110-1301, USA. */
+
+
+#include "mpfr-impl.h"
+
+/* return non-zero if the first n_bits bits of u, v are equal,
+   0 otherwise */
+int
+mpfr_eq (mpfr_srcptr u, mpfr_srcptr v, unsigned long int n_bits)
+{
+  mp_srcptr up, vp;
+  mp_size_t usize, vsize, size, i;
+  mp_exp_t uexp, vexp;
+  int k;
+
+  if (MPFR_ARE_SINGULAR(u, v))
+    {
+      if (MPFR_IS_NAN(u) || MPFR_IS_NAN(v))
+        return 0; /* non equal */
+      else if (MPFR_IS_INF(u) && MPFR_IS_INF(v))
+        return (MPFR_SIGN(u) == MPFR_SIGN(v));
+      else if (MPFR_IS_ZERO(u) && MPFR_IS_ZERO(v))
+        return 1;
+      else
+        return 0;
+    }
+
+  /* 1. Are the signs different?  */
+  if (MPFR_SIGN(u) != MPFR_SIGN(v))
+    return 0;
+
+  uexp = MPFR_GET_EXP (u);
+  vexp = MPFR_GET_EXP (v);
+
+  /* 2. Are the exponents different?  */
+  if (uexp != vexp)
+    return 0; /* no bit agree */
+
+  usize = (MPFR_PREC(u) - 1) / BITS_PER_MP_LIMB + 1;
+  vsize = (MPFR_PREC(v) - 1) / BITS_PER_MP_LIMB + 1;
+
+  if (vsize > usize) /* exchange u and v */
+    {
+      up = MPFR_MANT(v);
+      vp = MPFR_MANT(u);
+      size = vsize;
+      vsize = usize;
+      usize = size;
+    }
+  else
+    {
+      up = MPFR_MANT(u);
+      vp = MPFR_MANT(v);
+    }
+
+  /* now usize >= vsize */
+  MPFR_ASSERTD(usize >= vsize);
+
+  if (usize > vsize)
+    {
+      if ((unsigned long) vsize * BITS_PER_MP_LIMB < n_bits)
+        {
+          /* check if low min(PREC(u), n_bits) - (vsize * BITS_PER_MP_LIMB)
+             bits from u are non-zero */
+          unsigned long remains = n_bits - (vsize * BITS_PER_MP_LIMB);
+          k = usize - vsize - 1;
+          while (k >= 0 && remains >= BITS_PER_MP_LIMB && !up[k])
+            {
+              k--;
+              remains -= BITS_PER_MP_LIMB;
+            }
+          /* now either k < 0: all low bits from u are zero
+                 or remains < BITS_PER_MP_LIMB: check high bits from up[k]
+                 or up[k] <> 0: different */
+          if (k >= 0 && (((remains < BITS_PER_MP_LIMB) &&
+                          (up[k] >> (BITS_PER_MP_LIMB - remains))) ||
+                         (remains >= BITS_PER_MP_LIMB && up[k])))
+            return 0;           /* surely too different */
+        }
+      size = vsize;
+    }
+  else
+    {
+      size = usize;
+    }
+
+  /* now size = min (usize, vsize) */
+
+  /* If size is too large wrt n_bits, reduce it to look only at the
+     high n_bits bits.
+     Otherwise, if n_bits > size * BITS_PER_MP_LIMB, reduce n_bits to
+     size * BITS_PER_MP_LIMB, since the extra low bits of one of the
+     operands have already been check above. */
+  if ((unsigned long) size > 1 + (n_bits - 1) / BITS_PER_MP_LIMB)
+    size = 1 + (n_bits - 1) / BITS_PER_MP_LIMB;
+  else if (n_bits > (unsigned long) size * BITS_PER_MP_LIMB)
+    n_bits = size * BITS_PER_MP_LIMB;
+
+  up += usize - size;
+  vp += vsize - size;
+
+  for (i = size - 1; i > 0 && n_bits >= BITS_PER_MP_LIMB; i--)
+    {
+      if (up[i] != vp[i])
+        return 0;
+      n_bits -= BITS_PER_MP_LIMB;
+    }
+
+  /* now either i=0 or n_bits<BITS_PER_MP_LIMB */
+
+  /* since n_bits <= size * BITS_PER_MP_LIMB before the above for-loop,
+     we have the invariant n_bits <= (i+1) * BITS_PER_MP_LIMB, thus
+     we always have n_bits <= BITS_PER_MP_LIMB here */
+  MPFR_ASSERTD(n_bits <= BITS_PER_MP_LIMB);
+
+  if (n_bits & (BITS_PER_MP_LIMB - 1))
+    return (up[i] >> (BITS_PER_MP_LIMB - (n_bits & (BITS_PER_MP_LIMB - 1))) ==
+            vp[i] >> (BITS_PER_MP_LIMB - (n_bits & (BITS_PER_MP_LIMB - 1))));
+  else
+    return (up[i] == vp[i]);
+}