1 files changed, 101 insertions, 0 deletions
diff --git a/usr/src/lib/libm/common/C/tanh.c b/usr/src/lib/libm/common/C/tanh.c
new file mode 100644
index 0000000000..aa45520ae0
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+++ b/usr/src/lib/libm/common/C/tanh.c
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+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
+ */
+/*
+ * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#pragma weak tanh = __tanh
+
+/* INDENT OFF */
+/*
+ * TANH(X)
+ * RETURN THE HYPERBOLIC TANGENT OF X
+ * code based on 4.3bsd
+ * Modified by K.C. Ng for sun 4.0, Jan 31, 1987
+ *
+ * Method :
+ *	1. reduce x to non-negative by tanh(-x) = - tanh(x).
+ *	2.
+ *	    0      <  x <=  1.e-10 :  tanh(x) := x
+ *					          -expm1(-2x)
+ *	    1.e-10 <  x <=  1      :  tanh(x) := --------------
+ *					         expm1(-2x) + 2
+ *							  2
+ *	    1      <= x <=  22.0   :  tanh(x) := 1 -  ---------------
+ *						      expm1(2x) + 2
+ *	    22.0   <  x <= INF     :  tanh(x) := 1.
+ *
+ *	Note: 22 was chosen so that fl(1.0+2/(expm1(2*22)+2)) == 1.
+ *
+ * Special cases:
+ *	tanh(NaN) is NaN;
+ *	only tanh(0)=0 is exact for finite argument.
+ */
+
+#include "libm.h"
+#include "libm_synonyms.h"
+#include "libm_protos.h"
+#include <math.h>
+
+static const double
+	one = 1.0,
+	two = 2.0,
+	small = 1.0e-10,
+	big = 1.0e10;
+/* INDENT ON */
+
+double
+tanh(double x) {
+	double t, y, z;
+	int signx;
+	volatile double dummy;
+
+	if (isnan(x))
+		return (x * x);	/* + -> * for Cheetah */
+	signx = signbit(x);
+	t = fabs(x);
+	z = one;
+	if (t <= 22.0) {
+		if (t > one)
+			z = one - two / (expm1(t + t) + two);
+		else if (t > small) {
+			y = expm1(-t - t);
+			z = -y / (y + two);
+		} else {
+			/* raise the INEXACT flag for non-zero t */
+			dummy = t + big;
+#ifdef lint
+			dummy = dummy;
+#endif
+			return (x);
+		}
+	} else if (!finite(t))
+		return (copysign(1.0, x));
+	else
+		return (signx == 1 ? -z + small * small : z - small * small);
+
+	return (signx == 1 ? -z : z);
+}