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diff --git a/rts/gmp/mpz/com.c b/rts/gmp/mpz/com.c
new file mode 100644
index 0000000..18d6427
--- /dev/null
+++ b/rts/gmp/mpz/com.c
@@ -0,0 +1,93 @@
+/* mpz_com(mpz_ptr dst, mpz_ptr src) -- Assign the bit-complemented value of
+   SRC to DST.
+
+Copyright (C) 1991, 1993, 1994, 1996 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"
+
+void
+#if __STDC__
+mpz_com (mpz_ptr dst, mpz_srcptr src)
+#else
+mpz_com (dst, src)
+     mpz_ptr dst;
+     mpz_srcptr src;
+#endif
+{
+  mp_size_t size = src->_mp_size;
+  mp_srcptr src_ptr;
+  mp_ptr dst_ptr;
+
+  if (size >= 0)
+    {
+      /* As with infinite precision: one's complement, two's complement.
+	 But this can be simplified using the identity -x = ~x + 1.
+	 So we're going to compute (~~x) + 1 = x + 1!  */
+
+      if (dst->_mp_alloc < size + 1)
+	_mpz_realloc (dst, size + 1);
+
+      src_ptr = src->_mp_d;
+      dst_ptr = dst->_mp_d;
+
+      if (size == 0)
+	{
+	  /* Special case, as mpn_add wants the first arg's size >= the
+	     second arg's size.  */
+	  dst_ptr[0] = 1;
+	  dst->_mp_size = -1;
+	  return;
+	}
+
+      {
+	mp_limb_t cy;
+
+	cy = mpn_add_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
+	if (cy)
+	  {
+	    dst_ptr[size] = cy;
+	    size++;
+	  }
+      }
+
+      /* Store a negative size, to indicate ones-extension.  */
+      dst->_mp_size = -size;
+    }
+  else
+    {
+      /* As with infinite precision: two's complement, then one's complement.
+	 But that can be simplified using the identity -x = ~(x - 1).
+	 So we're going to compute ~~(x - 1) = x - 1!  */
+      size = -size;
+
+      if (dst->_mp_alloc < size)
+	_mpz_realloc (dst, size);
+
+      src_ptr = src->_mp_d;
+      dst_ptr = dst->_mp_d;
+
+      mpn_sub_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
+      size -= dst_ptr[size - 1] == 0;
+
+      /* Store a positive size, to indicate zero-extension.  */
+      dst->_mp_size = size;
+    }
+}