Imported gcc-4.4.3

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

diff --git a/mpfr/csch.c b/mpfr/csch.c
new file mode 100644 (file)
index 0000000..dbd42ee
--- /dev/null
+++ b/mpfr/csch.c
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+/* mpfr_csch - Hyperbolic cosecant function.
+
+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. */
+
+/* the hyperbolic cosecant is defined by csch(x) = 1/sinh(x).
+   csch (NaN) = NaN.
+   csch (+Inf) = +0.
+   csch (-Inf) = -0.
+   csch (+0) = +Inf.
+   csch (-0) = -Inf.
+*/
+
+#define FUNCTION mpfr_csch
+#define INVERSE  mpfr_sinh
+#define ACTION_NAN(y) do { MPFR_SET_NAN(y); MPFR_RET_NAN; } while (1)
+#define ACTION_INF(y) do { MPFR_SET_SAME_SIGN(y,x); MPFR_SET_ZERO (y); \
+                           MPFR_RET(0); } while (1)
+#define ACTION_ZERO(y,x) do { MPFR_SET_SAME_SIGN(y,x); MPFR_SET_INF(y); \
+                              MPFR_RET(0); } while (1)
+
+/* (This analysis is adapted from that for mpfr_csc.)
+   Near x=0, we have csch(x) = 1/x - x/6 + ..., more precisely we have
+   |csch(x) - 1/x| <= 0.2 for |x| <= 1. The error term has the opposite
+   sign as 1/x, thus |csch(x)| <= |1/x|. Then:
+   (i) either x is a power of two, then 1/x is exactly representable, and
+       as long as 1/2*ulp(1/x) > 0.2, we can conclude;
+   (ii) otherwise assume x has <= n bits, and y has <= n+1 bits, then
+   |y - 1/x| >= 2^(-2n) ufp(y), where ufp means unit in first place.
+   Since |csch(x) - 1/x| <= 0.2, if 2^(-2n) ufp(y) >= 0.4, then
+   |y - csch(x)| >= 2^(-2n-1) ufp(y), and rounding 1/x gives the correct
+   result. If x < 2^E, then y > 2^(-E), thus ufp(y) > 2^(-E-1).
+   A sufficient condition is thus EXP(x) <= -2 MAX(PREC(x),PREC(Y)). */
+#define ACTION_TINY(y,x,r) \
+  if (MPFR_EXP(x) <= -2 * (mp_exp_t) MAX(MPFR_PREC(x), MPFR_PREC(y)))   \
+    {                                                                   \
+      int signx = MPFR_SIGN(x);                                         \
+      inexact = mpfr_ui_div (y, 1, x, r);                               \
+      if (inexact == 0) /* x is a power of two */                       \
+        { /* result always 1/x, except when rounding to zero */         \
+          if (rnd_mode == GMP_RNDU || (rnd_mode == GMP_RNDZ && signx < 0)) \
+            {                                                           \
+              if (signx < 0)                                            \
+                mpfr_nextabove (y); /* -2^k + epsilon */                \
+              inexact = 1;                                              \
+            }                                                           \
+          else if (rnd_mode == GMP_RNDD || rnd_mode == GMP_RNDZ)        \
+            {                                                           \
+              if (signx > 0)                                            \
+                mpfr_nextbelow (y); /* 2^k - epsilon */                 \
+              inexact = -1;                                             \
+            }                                                           \
+          else /* round to nearest */                                   \
+            inexact = signx;                                            \
+        }                                                               \
+      MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);                \
+      goto end;                                                         \
+    }
+
+#include "gen_inverse.h"