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diff --git a/usr/src/lib/libm/common/Q/tanl.c b/usr/src/lib/libm/common/Q/tanl.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.
+ */
+
+/*
+ * tanl(x)
+ * Table look-up algorithm by K.C. Ng, November, 1989.
+ *
+ * kernel function:
+ *	__k_tanl	... tangent function on [-pi/4,pi/4]
+ *	__rem_pio2l	... argument reduction routine
+ *
+ * Method.
+ *      Let S and C denote the sin and cos respectively on [-PI/4, +PI/4].
+ *      1. Assume the argument x is reduced to y1+y2 = x-k*pi/2 in
+ *	   [-pi/2 , +pi/2], and let n = k mod 4.
+ *	2. Let S=S(y1+y2), C=C(y1+y2). Depending on n, we have
+ *
+ *          n        sin(x)      cos(x)        tan(x)
+ *     ----------------------------------------------------------
+ *	    0	       S	   C		 S/C
+ *	    1	       C	  -S		-C/S
+ *	    2	      -S	  -C		 S/C
+ *	    3	      -C	   S		-C/S
+ *     ----------------------------------------------------------
+ *
+ * Special cases:
+ *      Let trig be any of sin, cos, or tan.
+ *      trig(+-INF)  is NaN, with signals;
+ *      trig(NaN)    is that NaN;
+ *
+ * Accuracy:
+ *	computer TRIG(x) returns trig(x) nearly rounded.
+ */
+
+#pragma weak tanl = __tanl
+
+#include "libm.h"
+#include "longdouble.h"
+
+long double
+tanl(long double x) {
+	long double y[2], z = 0.0L;
+	int n, ix;
+
+	ix = *(int *) &x;		/* High word of x */
+	ix &= 0x7fffffff;
+	if (ix <= 0x3ffe9220)		/* |x| ~< pi/4 */
+		return (__k_tanl(x, z, 0));
+	else if (ix >= 0x7fff0000)	/* trig(Inf or NaN) is NaN */
+		return (x - x);
+	else {				/* argument reduction needed */
+		n = __rem_pio2l(x, y);
+		return (__k_tanl(y[0], y[1], (n & 1)));
+	}
+}