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diff --git a/mpfr/sqr.c b/mpfr/sqr.c
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--- /dev/null
+++ b/mpfr/sqr.c
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+/* mpfr_sqr -- Floating square
+
+Copyright 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+Contributed by the Arenaire and Cacao projects, INRIA.
+
+This file is part of the GNU MPFR Library.
+
+The GNU MPFR 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 MPFR 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 MPFR Library; see
+the file COPYING.LIB.  If not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
+MA 02110-1301, USA. */
+
+#include "mpfr-impl.h"
+
+int
+mpfr_sqr (mpfr_ptr a, mpfr_srcptr b, mp_rnd_t rnd_mode)
+{
+  int cc, inexact;
+  mp_exp_t  ax;
+  mp_limb_t *tmp;
+  mp_limb_t b1;
+  mp_prec_t bq;
+  mp_size_t bn, tn;
+  MPFR_TMP_DECL(marker);
+
+  MPFR_LOG_FUNC (("x[%#R]=%R rnd=%d", b, b, rnd_mode),
+                 ("y[%#R]=%R inexact=%d", a, a, inexact));
+
+  /* deal with special cases */
+  if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(b)))
+    {
+      if (MPFR_IS_NAN(b))
+        {
+          MPFR_SET_NAN(a);
+          MPFR_RET_NAN;
+        }
+      MPFR_SET_POS (a);
+      if (MPFR_IS_INF(b))
+        MPFR_SET_INF(a);
+      else
+        ( MPFR_ASSERTD(MPFR_IS_ZERO(b)), MPFR_SET_ZERO(a) );
+      MPFR_RET(0);
+    }
+  MPFR_CLEAR_FLAGS(a);
+  ax = 2 * MPFR_GET_EXP (b);
+  bq = MPFR_PREC(b);
+
+  MPFR_ASSERTD (2 * bq > bq); /* PREC_MAX is /2 so no integer overflow */
+
+  bn = MPFR_LIMB_SIZE(b); /* number of limbs of b */
+  tn = 1 + (2 * bq - 1) / BITS_PER_MP_LIMB; /* number of limbs of square,
+                                               2*bn or 2*bn-1 */
+
+  MPFR_TMP_MARK(marker);
+  tmp = (mp_limb_t *) MPFR_TMP_ALLOC((size_t) 2 * bn * BYTES_PER_MP_LIMB);
+
+  /* Multiplies the mantissa in temporary allocated space */
+  mpn_sqr_n (tmp, MPFR_MANT(b), bn);
+  b1 = tmp[2 * bn - 1];
+
+  /* now tmp[0]..tmp[2*bn-1] contains the product of both mantissa,
+     with tmp[2*bn-1]>=2^(BITS_PER_MP_LIMB-2) */
+  b1 >>= BITS_PER_MP_LIMB - 1; /* msb from the product */
+
+  /* if the mantissas of b and c are uniformly distributed in ]1/2, 1],
+     then their product is in ]1/4, 1/2] with probability 2*ln(2)-1 ~ 0.386
+     and in [1/2, 1] with probability 2-2*ln(2) ~ 0.614 */
+  tmp += 2 * bn - tn; /* +0 or +1 */
+  if (MPFR_UNLIKELY(b1 == 0))
+    mpn_lshift (tmp, tmp, tn, 1); /* tn <= k, so no stack corruption */
+
+  cc = mpfr_round_raw (MPFR_MANT (a), tmp, 2 * bq, 0,
+                       MPFR_PREC (a), rnd_mode, &inexact);
+  /* cc = 1 ==> result is a power of two */
+  if (MPFR_UNLIKELY(cc))
+    MPFR_MANT(a)[MPFR_LIMB_SIZE(a)-1] = MPFR_LIMB_HIGHBIT;
+
+  MPFR_TMP_FREE(marker);
+  {
+    mp_exp_t ax2 = ax + (mp_exp_t) (b1 - 1 + cc);
+    if (MPFR_UNLIKELY( ax2 > __gmpfr_emax))
+      return mpfr_overflow (a, rnd_mode, MPFR_SIGN_POS);
+    if (MPFR_UNLIKELY( ax2 < __gmpfr_emin))
+      {
+        /* In the rounding to the nearest mode, if the exponent of the exact
+           result (i.e. before rounding, i.e. without taking cc into account)
+           is < __gmpfr_emin - 1 or the exact result is a power of 2 (i.e. if
+           both arguments are powers of 2), then round to zero. */
+        if (rnd_mode == GMP_RNDN &&
+            (ax + (mp_exp_t) b1 < __gmpfr_emin || mpfr_powerof2_raw (b)))
+          rnd_mode = GMP_RNDZ;
+        return mpfr_underflow (a, rnd_mode, MPFR_SIGN_POS);
+      }
+    MPFR_SET_EXP (a, ax2);
+    MPFR_SET_POS (a);
+  }
+  MPFR_RET (inexact);
+}