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, 85 insertions, 0 deletions

diff --git a/usr/src/lib/libm/common/C/logb.c b/usr/src/lib/libm/common/C/logb.c
new file mode 100644
index 0000000000..71c31e069c
--- /dev/null
+++ b/usr/src/lib/libm/common/C/logb.c
@@ -0,0 +1,85 @@
+/*
+ * 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.
+ */
+
+#if defined(ELFOBJ)
+#pragma weak logb = __logb
+#pragma weak _logb = __logb
+#endif
+
+#include "libm.h"
+#include "xpg6.h"	/* __xpg6 */
+#define	_C99SUSv3_logb	_C99SUSv3_logb_subnormal_is_like_ilogb
+
+#if defined(USE_FPSCALE) || defined(__x86)
+static const double two52 = 4503599627370496.0;
+#else
+/*
+ * v: high part of a non-zero subnormal |x|; w: low part of |x|
+ */
+static int
+ilogb_subnormal(unsigned v, unsigned w) {
+	int r = -1022 - 52;
+
+	if (v)
+		r += 32;
+	else
+		v = w;
+	if (v & 0xffff0000)
+		r += 16, v >>= 16;
+	if (v & 0xff00)
+		r += 8, v >>= 8;
+	if (v & 0xf0)
+		r += 4, v >>= 4;
+	v <<= 1;
+	return (r + ((0xffffaa50 >> v) & 0x3));
+}
+#endif	/* defined(USE_FPSCALE) */
+
+double
+logb(double x) {
+	int *px = (int *) &x, k = px[HIWORD] & ~0x80000000;
+
+	if (k < 0x00100000) {
+		if ((px[LOWORD] | k) == 0)
+			return (_SVID_libm_err(x, x, 45));
+		else if ((__xpg6 & _C99SUSv3_logb) != 0) {
+#if defined(USE_FPSCALE) || defined(__x86)
+			x *= two52;
+			return ((double) (((px[HIWORD] & 0x7ff00000) >> 20)
+				- 1075));
+#else
+			return ((double) ilogb_subnormal(k, px[LOWORD]));
+#endif
+		} else
+			return (-1022.0);
+	} else if (k < 0x7ff00000)
+		return ((double) ((k >> 20) - 1023));
+	else
+		return (x * x);
+}