693 Opensource replacement of sunwlibm

Reviewed by: Igor Kozhukhov ikozhukhov@gmail.com
Reviewed by: Keith M Wesolowski <keith.wesolowski@joyent.com>
Reviewed by: Richard Lowe <richlowe@richlowe.net>
Approved by: Dan McDonald <danmcd@omniti.com>

1 files changed, 88 insertions, 0 deletions

diff --git a/usr/src/lib/libm/common/C/exp2.c b/usr/src/lib/libm/common/C/exp2.c
new file mode 100644
index 0000000000..f447890f9e
--- /dev/null
+++ b/usr/src/lib/libm/common/C/exp2.c
@@ -0,0 +1,88 @@
+/*
+ * 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 exp2 = __exp2
+
+/* INDENT OFF */
+/*
+ * exp2(x)
+ * Code by K.C. Ng for SUN 4.0 libm.
+ * Method :
+ *	exp2(x) = 2**x = 2**((x-anint(x))+anint(x))
+ *		= 2**anint(x)*2**(x-anint(x))
+ *		= 2**anint(x)*exp((x-anint(x))*ln2)
+ */
+/* INDENT ON */
+
+#include "libm.h"
+
+static const double C[] = {
+	0.0,
+	1.0,
+	0.5,
+	6.93147180559945286227e-01,
+	1.0e300,
+	1.0e-300,
+};
+
+#define	zero	C[0]
+#define	one	C[1]
+#define	half	C[2]
+#define	ln2	C[3]
+#define	huge	C[4]
+#define	tiny	C[5]
+
+double
+exp2(double x) {
+	int	ix, hx, k;
+	double	t;
+
+	ix = ((int *)&x)[HIWORD];
+	hx = ix & ~0x80000000;
+
+	if (hx >= 0x4090e000) {	/* |x| >= 1080 or x is nan */
+		if (hx >= 0x7ff00000) {	/* x is inf or nan */
+			if (ix == 0xfff00000 && ((int *)&x)[LOWORD] == 0)
+				return (zero);
+			return (x * x);
+		}
+		t = (ix < 0)? tiny : huge;
+		return (t * t);
+	}
+
+	if (hx < 0x3fe00000) {	/* |x| < 0.5 */
+		if (hx < 0x3c000000)
+			return (one + x);
+		return (exp(ln2 * x));
+	}
+
+	k = (int)x;
+	if (x != (double)k)
+		k = (int)((ix < 0)? x - half : x + half);
+	return (scalbn(exp(ln2 * (x - (double)k)), k));
+}