diff --git a/third_party/gmp/gen-fib.c b/third_party/gmp/gen-fib.c
new file mode 100644
index 0000000..647a6bb
--- /dev/null
+++ b/third_party/gmp/gen-fib.c
@@ -0,0 +1,156 @@
+/* Generate Fibonacci table data.
+
+Copyright 2001, 2002, 2004, 2012, 2014, 2015 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 either:
+
+  * 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.
+
+or
+
+  * the GNU General Public License as published by the Free Software
+    Foundation; either version 2 of the License, or (at your option) any
+    later version.
+
+or both in parallel, as here.
+
+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 General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library.  If not,
+see https://www.gnu.org/licenses/.  */
+
+#include <stdio.h>
+#include "bootstrap.c"
+
+mpz_t  *f;
+int    fnum, fib_limit, luc_limit;
+
+void
+generate (int numb_bits)
+{
+  mpz_t  limit, l;
+  int    falloc, i;
+
+  mpz_init2 (limit, numb_bits + 1);
+  mpz_setbit (limit, numb_bits);
+
+  /* fib(2n) > 2^n, so use 2n as a limit for the table size */
+  falloc = 2 * numb_bits;
+  f = (mpz_t*) xmalloc (falloc * sizeof (*f));
+
+  mpz_init_set_ui (f[0], 1L);  /* F[-1] */
+  mpz_init_set_ui (f[1], 0L);  /* F[0] */
+
+  mpz_init (l);
+
+  for (i = 2; ; i++)
+    {
+      assert (i < falloc);
+
+      /* F[i] = F[i-1] + F[i-2] */
+      mpz_init (f[i]);
+      mpz_add (f[i], f[i-1], f[i-2]);
+      if (mpz_cmp (f[i], limit) >= 0)
+        break;
+
+      fnum = i+1;
+      fib_limit = i-1;
+
+      /* L[i] = F[i]+2*F[i-1] */
+      mpz_add (l, f[i], f[i-1]);
+      mpz_add (l, l, f[i-1]);
+
+      if (mpz_cmp (l, limit) < 0)
+        luc_limit = i-1;
+    }
+
+  mpz_clear (limit);
+}
+
+
+void
+header (int numb_bits)
+{
+  printf ("/* This file generated by gen-fib.c - DO NOT EDIT. */\n");
+  printf ("\n");
+  printf ("#if GMP_NUMB_BITS != %d\n", numb_bits);
+  printf ("Error, error, this data is for %d bits\n", numb_bits);
+  printf ("#endif\n");
+  printf ("\n");
+  printf ("#define FIB_TABLE_LIMIT         %d\n", fib_limit);
+  printf ("#define FIB_TABLE_LUCNUM_LIMIT  %d\n", luc_limit);
+}
+
+void
+table (int numb_bits)
+{
+  int  i;
+
+  printf ("/* This file generated by gen-fib.c - DO NOT EDIT. */\n");
+  printf ("\n");
+  printf ("#include \"gmp.h\"\n");
+  printf ("#include \"gmp-impl.h\"\n");
+  printf ("\n");
+  printf ("#if GMP_NUMB_BITS != %d\n", numb_bits);
+  printf ("Error, error, this data is for %d bits\n", numb_bits);
+  printf ("#endif\n");
+  printf ("\n");
+  printf ("const mp_limb_t\n");
+  printf ("__gmp_fib_table[FIB_TABLE_LIMIT+2] = {\n");
+
+  for (i = 0; i < fnum; i++)
+    {
+      printf ("  CNST_LIMB (0x");
+      mpz_out_str (stdout, 16, f[i]);
+      printf ("),  /* %d */\n", i-1);
+    }
+  printf ("};\n");
+}
+
+int
+main (int argc, char *argv[])
+{
+  int  limb_bits, nail_bits, numb_bits;
+
+  if (argc != 4)
+    {
+      fprintf (stderr, "Usage: gen-fib <header|table> <limbbits> <nailbits>\n");
+      exit (1);
+    }
+
+  limb_bits = atoi (argv[2]);
+  nail_bits = atoi (argv[3]);
+
+  if (limb_bits <= 0
+      || nail_bits < 0
+      || nail_bits >= limb_bits)
+    {
+      fprintf (stderr, "Invalid limb/nail bits: %d %d\n",
+               limb_bits, nail_bits);
+      exit (1);
+    }
+  numb_bits = limb_bits - nail_bits;
+
+  generate (numb_bits);
+
+  if (strcmp (argv[1], "header") == 0)
+    header (numb_bits);
+  else if (strcmp (argv[1], "table") == 0)
+    table (numb_bits);
+  else
+    {
+      fprintf (stderr, "Invalid header/table choice: %s\n", argv[1]);
+      exit (1);
+    }
+
+  return 0;
+}