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diff --git a/ghc/rts/gmp/mpz/rrandomb.c b/ghc/rts/gmp/mpz/rrandomb.c
new file mode 100644
index 0000000..7d78243
--- /dev/null
+++ b/ghc/rts/gmp/mpz/rrandomb.c
@@ -0,0 +1,117 @@
+/* mpz_rrandomb -- Generate a positive random mpz_t of specified bit size, with
+   long runs of consecutive ones and zeros in the binary representation.
+   Meant for testing of other MP routines.
+
+Copyright (C) 2000 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 2.1 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; see the file COPYING.LIB.  If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+MA 02111-1307, USA. */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+
+static void gmp_rrandomb _PROTO ((mp_ptr rp, gmp_randstate_t rstate, unsigned long int nbits));
+
+void
+#if __STDC__
+mpz_rrandomb (mpz_ptr x, gmp_randstate_t rstate, unsigned long int nbits)
+#else
+mpz_rrandomb (x, rstate, nbits)
+     mpz_ptr x;
+     gmp_randstate_t rstate;
+     unsigned long int nbits;
+#endif
+{
+  mp_size_t nl = 0;
+
+  if (nbits != 0)
+    {
+      mp_ptr xp;
+      nl = (nbits + BITS_PER_MP_LIMB - 1) / BITS_PER_MP_LIMB;
+      if (x->_mp_alloc < nl)
+	_mpz_realloc (x, nl);
+
+      xp = PTR(x);
+      gmp_rrandomb (xp, rstate, nbits);
+      MPN_NORMALIZE (xp, nl);
+    }
+
+  SIZ(x) = nl;
+}
+
+#define BITS_PER_CHUNK 4
+
+static void
+#if __STDC__
+gmp_rrandomb (mp_ptr rp, gmp_randstate_t rstate, unsigned long int nbits)
+#else
+gmp_rrandomb (rp, rstate, nbits)
+     mp_ptr rp;
+     gmp_randstate_t rstate;
+     unsigned long int nbits;
+#endif
+{
+  int nb;
+  int bit_pos;
+  mp_size_t limb_pos;
+  mp_limb_t ran, ranm;
+  mp_limb_t acc;
+  mp_size_t n;
+
+  bit_pos = nbits % BITS_PER_MP_LIMB;
+  limb_pos = nbits / BITS_PER_MP_LIMB;
+  if (bit_pos == 0)
+    {
+      bit_pos = BITS_PER_MP_LIMB;
+      limb_pos--;
+    }
+
+  acc = 0;
+  while (limb_pos >= 0)
+    {
+      _gmp_rand (&ranm, rstate, BITS_PER_CHUNK + 1);
+      ran = ranm;
+      nb = (ran >> 1) + 1;
+      if ((ran & 1) != 0)
+	{
+	  /* Generate a string of ones.  */
+	  if (nb > bit_pos)
+	    {
+	      rp[limb_pos--] = acc | ((((mp_limb_t) 1) << bit_pos) - 1);
+	      bit_pos += BITS_PER_MP_LIMB;
+	      bit_pos -= nb;
+	      acc = (~(mp_limb_t) 0) << bit_pos;
+	    }
+	  else
+	    {
+	      bit_pos -= nb;
+	      acc |= ((((mp_limb_t) 1) << nb) - 1) << bit_pos;
+	    }
+	}
+      else
+	{
+	  /* Generate a string of zeroes.  */
+	  if (nb > bit_pos)
+	    {
+	      rp[limb_pos--] = acc;
+	      acc = 0;
+	      bit_pos += BITS_PER_MP_LIMB;
+	    }
+	  bit_pos -= nb;
+	}
+    }
+}