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diff --git a/gmp/mpn/generic/toom2_sqr.c b/gmp/mpn/generic/toom2_sqr.c
new file mode 100644
index 00000000..445cff8f
--- /dev/null
+++ b/gmp/mpn/generic/toom2_sqr.c
@@ -0,0 +1,135 @@
+/* mpn_toom2_sqr -- Square {ap,an}.
+
+   Contributed to the GNU project by Torbjorn Granlund.
+
+   THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.  IT IS ONLY
+   SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.  IN FACT, IT IS ALMOST
+   GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
+
+Copyright 2006, 2007, 2008 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"
+
+/* Evaluate in: -1, 0, +inf
+
+  <-s--><--n-->
+   ____ ______
+  |_a1_|___a0_|
+   |b1_|___b0_|
+   <-t-><--n-->
+
+  v0  =  a0     * b0       #   A(0)*B(0)
+  vm1 = (a0- a1)*(b0- b1)  #  A(-1)*B(-1)
+  vinf=      a1 *     b1   # A(inf)*B(inf)
+*/
+
+#if TUNE_PROGRAM_BUILD
+#define MAYBE_sqr_toom2   1
+#else
+#define MAYBE_sqr_toom2							\
+  (SQR_TOOM3_THRESHOLD >= 2 * SQR_TOOM2_THRESHOLD)
+#endif
+
+#define TOOM2_SQR_N_REC(p, a, n, ws)					\
+  do {									\
+    if (! MAYBE_sqr_toom2						\
+	|| BELOW_THRESHOLD (n, SQR_KARATSUBA_THRESHOLD))		\
+      mpn_sqr_basecase (p, a, n);					\
+    else								\
+      mpn_toom2_sqr (p, a, n, ws);					\
+  } while (0)
+
+void
+mpn_toom2_sqr (mp_ptr pp,
+	       mp_srcptr ap, mp_size_t an,
+	       mp_ptr scratch)
+{
+  mp_size_t n, s;
+  mp_limb_t cy, cy2;
+  mp_ptr asm1;
+
+#define a0  ap
+#define a1  (ap + n)
+
+  s = an >> 1;
+  n = an - s;
+
+  ASSERT (0 < s && s <= n);
+
+  asm1 = pp;
+
+  /* Compute asm1.  */
+  if (s == n)
+    {
+      if (mpn_cmp (a0, a1, n) < 0)
+	{
+	  mpn_sub_n (asm1, a1, a0, n);
+	}
+      else
+	{
+	  mpn_sub_n (asm1, a0, a1, n);
+	}
+    }
+  else
+    {
+      if (mpn_zero_p (a0 + s, n - s) && mpn_cmp (a0, a1, s) < 0)
+	{
+	  mpn_sub_n (asm1, a1, a0, s);
+	  MPN_ZERO (asm1 + s, n - s);
+	}
+      else
+	{
+	  mpn_sub (asm1, a0, n, a1, s);
+	}
+    }
+
+#define v0	pp				/* 2n */
+#define vinf	(pp + 2 * n)			/* s+s */
+#define vm1	scratch				/* 2n */
+
+  /* vm1, 2n limbs */
+  TOOM2_SQR_N_REC (vm1, asm1, n, scratch);
+
+  /* vinf, s+s limbs */
+  TOOM2_SQR_N_REC (vinf, a1, s, scratch);
+
+  /* v0, 2n limbs */
+  TOOM2_SQR_N_REC (v0, ap, n, scratch);
+
+  /* H(v0) + L(vinf) */
+  cy = mpn_add_n (pp + 2 * n, v0 + n, vinf, n);
+
+  /* L(v0) + H(v0) */
+  cy2 = cy + mpn_add_n (pp + n, pp + 2 * n, v0, n);
+
+  /* L(vinf) + H(vinf) */
+  cy += mpn_add (pp + 2 * n, pp + 2 * n, n, vinf + n, s + s - n);
+
+  cy -= mpn_sub_n (pp + n, pp + n, vm1, 2 * n);
+
+  ASSERT (cy + 1  <= 3);
+  ASSERT (cy2 <= 2);
+
+  mpn_incr_u (pp + 2 * n, cy2);
+  if (LIKELY (cy <= 2))
+    mpn_incr_u (pp + 3 * n, cy);
+  else
+    mpn_decr_u (pp + 3 * n, 1);
+}