Imported gcc-4.4.3

[msp430-gcc.git] / mpfr / ui_pow_ui.c

diff --git a/mpfr/ui_pow_ui.c b/mpfr/ui_pow_ui.c
new file mode 100644 (file)
index 0000000..f72a907
--- /dev/null
+++ b/mpfr/ui_pow_ui.c
@@ -0,0 +1,95 @@
+/*  mpfr_ui_pow_ui -- compute the power beetween two machine integer
+
+Copyright 1999, 2000, 2001, 2002, 2003, 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_ui_pow_ui (mpfr_ptr x, unsigned long int y, unsigned long int n,
+                mp_rnd_t rnd)
+{
+  mp_exp_t err;
+  unsigned long m;
+  mpfr_t res;
+  mp_prec_t prec;
+  int size_n;
+  int inexact;
+  MPFR_ZIV_DECL (loop);
+  MPFR_SAVE_EXPO_DECL (expo);
+
+  if (MPFR_UNLIKELY (n <= 1))
+    {
+      if (n == 1)
+        return mpfr_set_ui (x, y, rnd);     /* y^1 = y */
+      else
+        return mpfr_set_ui (x, 1, rnd);     /* y^0 = 1 for any y */
+    }
+  else if (MPFR_UNLIKELY (y <= 1))
+    {
+      if (y == 1)
+        return mpfr_set_ui (x, 1, rnd);     /* 1^n = 1 for any n > 0 */
+      else
+        return mpfr_set_ui (x, 0, rnd);     /* 0^n = 0 for any n > 0 */
+    }
+
+  for (size_n = 0, m = n; m; size_n++, m >>= 1);
+
+  MPFR_SAVE_EXPO_MARK (expo);
+  prec = MPFR_PREC (x) + 3 + size_n;
+  mpfr_init2 (res, prec);
+
+  MPFR_ZIV_INIT (loop, prec);
+  for (;;)
+    {
+      int i = size_n;
+
+      inexact = mpfr_set_ui (res, y, GMP_RNDU);
+      err = 1;
+      /* now 2^(i-1) <= n < 2^i: i=1+floor(log2(n)) */
+      for (i -= 2; i >= 0; i--)
+        {
+          inexact |= mpfr_mul (res, res, res, GMP_RNDU);
+          err++;
+          if (n & (1UL << i))
+            inexact |= mpfr_mul_ui (res, res, y, GMP_RNDU);
+        }
+      /* since the loop is executed floor(log2(n)) times,
+         we have err = 1+floor(log2(n)).
+         Since prec >= MPFR_PREC(x) + 4 + floor(log2(n)), prec > err */
+      err = prec - err;
+
+      if (MPFR_LIKELY (inexact == 0
+                       || MPFR_CAN_ROUND (res, err, MPFR_PREC (x), rnd)))
+        break;
+
+      /* Actualisation of the precision */
+      MPFR_ZIV_NEXT (loop, prec);
+      mpfr_set_prec (res, prec);
+    }
+  MPFR_ZIV_FREE (loop);
+
+  inexact = mpfr_set (x, res, rnd);
+
+  mpfr_clear (res);
+
+  MPFR_SAVE_EXPO_FREE (expo);
+  return mpfr_check_range (x, inexact, rnd);
+}