Imported gcc-4.4.3

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

diff --git a/mpfr/exp.c b/mpfr/exp.c
new file mode 100644 (file)
index 0000000..10e859c
--- /dev/null
+++ b/mpfr/exp.c
@@ -0,0 +1,163 @@
+/* mpfr_exp -- exponential of a floating-point number
+
+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"
+
+/* #define DEBUG */
+
+int
+mpfr_exp (mpfr_ptr y, mpfr_srcptr x, mp_rnd_t rnd_mode)
+{
+  mp_exp_t expx;
+  mp_prec_t precy;
+  int inexact;
+  MPFR_SAVE_EXPO_DECL (expo);
+
+  MPFR_LOG_FUNC (("x[%#R]=%R rnd=%d", x, x, rnd_mode),
+                 ("y[%#R]=%R inexact=%d", y, y, inexact));
+
+  if (MPFR_UNLIKELY( MPFR_IS_SINGULAR(x) ))
+    {
+      if (MPFR_IS_NAN(x))
+        {
+          MPFR_SET_NAN(y);
+          MPFR_RET_NAN;
+        }
+      else if (MPFR_IS_INF(x))
+        {
+          if (MPFR_IS_POS(x))
+            MPFR_SET_INF(y);
+          else
+            MPFR_SET_ZERO(y);
+          MPFR_SET_POS(y);
+          MPFR_RET(0);
+        }
+      else
+        {
+          MPFR_ASSERTD(MPFR_IS_ZERO(x));
+          return mpfr_set_ui (y, 1, rnd_mode);
+        }
+    }
+
+  /* First, let's detect most overflow and underflow cases. */
+  {
+    mpfr_t e, bound;
+
+    /* We must extended the exponent range and save the flags now. */
+    MPFR_SAVE_EXPO_MARK (expo);
+
+    mpfr_init2 (e, sizeof (mp_exp_t) * CHAR_BIT);
+    mpfr_init2 (bound, 32);
+
+    inexact = mpfr_set_exp_t (e, expo.saved_emax, GMP_RNDN);
+    MPFR_ASSERTD (inexact == 0);
+    mpfr_const_log2 (bound, expo.saved_emax < 0 ? GMP_RNDD : GMP_RNDU);
+    mpfr_mul (bound, bound, e, GMP_RNDU);
+    if (MPFR_UNLIKELY (mpfr_cmp (x, bound) >= 0))
+      {
+        /* x > log(2^emax), thus exp(x) > 2^emax */
+        mpfr_clears (e, bound, (mpfr_ptr) 0);
+        MPFR_SAVE_EXPO_FREE (expo);
+        return mpfr_overflow (y, rnd_mode, 1);
+      }
+
+    inexact = mpfr_set_exp_t (e, expo.saved_emin, GMP_RNDN);
+    MPFR_ASSERTD (inexact == 0);
+    inexact = mpfr_sub_ui (e, e, 2, GMP_RNDN);
+    MPFR_ASSERTD (inexact == 0);
+    mpfr_const_log2 (bound, expo.saved_emin < 0 ? GMP_RNDU : GMP_RNDD);
+    mpfr_mul (bound, bound, e, GMP_RNDD);
+    if (MPFR_UNLIKELY (mpfr_cmp (x, bound) <= 0))
+      {
+        /* x < log(2^(emin - 2)), thus exp(x) < 2^(emin - 2) */
+        mpfr_clears (e, bound, (mpfr_ptr) 0);
+        MPFR_SAVE_EXPO_FREE (expo);
+        return mpfr_underflow (y, rnd_mode == GMP_RNDN ? GMP_RNDZ : rnd_mode,
+                               1);
+      }
+
+    /* Other overflow/underflow cases must be detected
+       by the generic routines. */
+    mpfr_clears (e, bound, (mpfr_ptr) 0);
+    MPFR_SAVE_EXPO_FREE (expo);
+  }
+
+  MPFR_CLEAR_FLAGS (y);
+
+  expx  = MPFR_GET_EXP (x);
+  precy = MPFR_PREC (y);
+
+  /* if x < 2^(-precy), then exp(x) i.e. gives 1 +/- 1 ulp(1) */
+  if (MPFR_UNLIKELY (expx < 0 && (mpfr_uexp_t) (-expx) > precy))
+    {
+      mp_exp_t emin = __gmpfr_emin;
+      mp_exp_t emax = __gmpfr_emax;
+      int signx = MPFR_SIGN (x);
+
+      MPFR_SET_POS (y);
+      if (MPFR_IS_NEG_SIGN (signx) && (rnd_mode == GMP_RNDD ||
+                                       rnd_mode == GMP_RNDZ))
+        {
+          __gmpfr_emin = 0;
+          __gmpfr_emax = 0;
+          mpfr_setmax (y, 0);  /* y = 1 - epsilon */
+          inexact = -1;
+        }
+      else
+        {
+          __gmpfr_emin = 1;
+          __gmpfr_emax = 1;
+          mpfr_setmin (y, 1);  /* y = 1 */
+          if (MPFR_IS_POS_SIGN (signx) && rnd_mode == GMP_RNDU)
+            {
+              mp_size_t yn;
+              int sh;
+
+              yn = 1 + (MPFR_PREC(y) - 1) / BITS_PER_MP_LIMB;
+              sh = (mp_prec_t) yn * BITS_PER_MP_LIMB - MPFR_PREC(y);
+              MPFR_MANT(y)[0] += MPFR_LIMB_ONE << sh;
+              inexact = 1;
+            }
+          else
+            inexact = -MPFR_FROM_SIGN_TO_INT(signx);
+        }
+
+      __gmpfr_emin = emin;
+      __gmpfr_emax = emax;
+    }
+  else  /* General case */
+    {
+      if (MPFR_UNLIKELY (precy > MPFR_EXP_THRESHOLD))
+        /* mpfr_exp_3 saves the exponent range and flags itself, otherwise
+           the flag changes in mpfr_exp_3 are lost */
+        inexact = mpfr_exp_3 (y, x, rnd_mode); /* O(M(n) log(n)^2) */
+      else
+        {
+          MPFR_SAVE_EXPO_MARK (expo);
+          inexact = mpfr_exp_2 (y, x, rnd_mode); /* O(n^(1/3) M(n)) */
+          MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);
+          MPFR_SAVE_EXPO_FREE (expo);
+        }
+    }
+
+  return mpfr_check_range (y, inexact, rnd_mode);
+}