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diff --git a/gmp/mpf/set_prc.c b/gmp/mpf/set_prc.c
new file mode 100644
index 00000000..52f44aa4
--- /dev/null
+++ b/gmp/mpf/set_prc.c
@@ -0,0 +1,58 @@
+/* mpf_set_prec(x) -- Change the precision of x.
+
+Copyright 1993, 1994, 1995, 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"
+
+
+/* A full new_prec+1 limbs are always retained, even though just new_prec
+   would satisfy the requested precision.  If size==new_prec+1 then
+   certainly new_prec+1 should be kept since no copying is needed in that
+   case.  If just new_prec was kept for size>new_prec+1 it'd be a bit
+   inconsistent.  */
+
+void
+mpf_set_prec (mpf_ptr x, unsigned long int new_prec_in_bits)
+{
+  mp_size_t  old_prec, new_prec, new_prec_plus1;
+  mp_size_t  size, sign;
+  mp_ptr     xp;
+
+  new_prec = __GMPF_BITS_TO_PREC (new_prec_in_bits);
+  old_prec = PREC(x);
+
+  /* do nothing if already the right precision */
+  if (new_prec == old_prec)
+    return;
+
+  PREC(x) = new_prec;
+  new_prec_plus1 = new_prec + 1;
+
+  /* retain most significant limbs */
+  sign = SIZ(x);
+  size = ABS (sign);
+  xp = PTR(x);
+  if (size > new_prec_plus1)
+    {
+      SIZ(x) = (sign >= 0 ? new_prec_plus1 : -new_prec_plus1);
+      MPN_COPY_INCR (xp, xp + size - new_prec_plus1, new_prec_plus1);
+    }
+
+  PTR(x) = __GMP_REALLOCATE_FUNC_LIMBS (xp, old_prec+1, new_prec_plus1);
+}