Imported gcc-4.4.3

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

diff --git a/mpfr/round_p.c b/mpfr/round_p.c
new file mode 100644 (file)
index 0000000..d3c5d98
--- /dev/null
+++ b/mpfr/round_p.c
@@ -0,0 +1,123 @@
+/* mpfr_round_p -- check if an approximation is roundable.
+
+Copyright 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"
+
+/* Check against mpfr_can_round ? */
+#ifdef WANT_ASSERT
+# if WANT_ASSERT >= 2
+int mpfr_round_p_2 (mp_limb_t *, mp_size_t, mp_exp_t, mp_prec_t);
+int
+mpfr_round_p (mp_limb_t *bp, mp_size_t bn, mp_exp_t err0, mp_prec_t prec)
+{
+  int i1, i2;
+
+  i1 = mpfr_round_p_2 (bp, bn, err0, prec);
+  i2 = mpfr_can_round_raw (bp, bn, MPFR_SIGN_POS, err0,
+                           GMP_RNDN, GMP_RNDZ, prec);
+  if (i1 != i2)
+    {
+      fprintf (stderr, "mpfr_round_p(%d) != mpfr_can_round(%d)!\n"
+               "bn = %lu, err0 = %ld, prec = %lu\nbp = ", i1, i2,
+               (unsigned long) bn, (long) err0, (unsigned long) prec);
+      gmp_fprintf (stderr, "%NX\n", bp, bn);
+      MPFR_ASSERTN (0);
+    }
+  return i1;
+}
+# define mpfr_round_p mpfr_round_p_2
+# endif
+#endif
+
+/*
+ * Assuming {bp, bn} is an approximation of a non-singular number
+ * with error at most equal to 2^(EXP(b)-err0) (`err0' bits of b are known)
+ * of direction unknown, check if we can round b toward zero with
+ * precision prec.
+ */
+int
+mpfr_round_p (mp_limb_t *bp, mp_size_t bn, mp_exp_t err0, mp_prec_t prec)
+{
+  mp_prec_t err;
+  mp_size_t k, n;
+  mp_limb_t tmp, mask;
+  int s;
+
+  err = (mp_prec_t) bn * BITS_PER_MP_LIMB;
+  if (MPFR_UNLIKELY (err0 <= 0 || (mpfr_uexp_t) err0 <= prec || prec >= err))
+    return 0;  /* can't round */
+  err = MIN (err, (mpfr_uexp_t) err0);
+
+  k = prec / BITS_PER_MP_LIMB;
+  s = BITS_PER_MP_LIMB - prec%BITS_PER_MP_LIMB;
+  n = err / BITS_PER_MP_LIMB - k;
+
+  MPFR_ASSERTD (n >= 0);
+  MPFR_ASSERTD (bn > k);
+
+  /* Check first limb */
+  bp += bn-1-k;
+  tmp = *bp--;
+  mask = s == BITS_PER_MP_LIMB ? MP_LIMB_T_MAX : MPFR_LIMB_MASK (s);
+  tmp &= mask;
+
+  if (MPFR_LIKELY (n == 0))
+    {
+      /* prec and error are in the same limb */
+      s = BITS_PER_MP_LIMB - err % BITS_PER_MP_LIMB;
+      MPFR_ASSERTD (s < BITS_PER_MP_LIMB);
+      tmp  >>= s;
+      mask >>= s;
+      return tmp != 0 && tmp != mask;
+    }
+  else if (MPFR_UNLIKELY (tmp == 0))
+    {
+      /* Check if all (n-1) limbs are 0 */
+      while (--n)
+        if (*bp-- != 0)
+          return 1;
+      /* Check if final error limb is 0 */
+      s = BITS_PER_MP_LIMB - err % BITS_PER_MP_LIMB;
+      if (s == BITS_PER_MP_LIMB)
+        return 0;
+      tmp = *bp >> s;
+      return tmp != 0;
+    }
+  else if (MPFR_UNLIKELY (tmp == mask))
+    {
+      /* Check if all (n-1) limbs are 11111111111111111 */
+      while (--n)
+        if (*bp-- != MP_LIMB_T_MAX)
+          return 1;
+      /* Check if final error limb is 0 */
+      s = BITS_PER_MP_LIMB - err % BITS_PER_MP_LIMB;
+      if (s == BITS_PER_MP_LIMB)
+        return 0;
+      tmp = *bp >> s;
+      return tmp != (MP_LIMB_T_MAX >> s);
+    }
+  else
+    {
+      /* First limb is different from 000000 or 1111111 */
+      return 1;
+    }
+}