1 files changed, 134 insertions, 0 deletions
diff --git a/lib/libc/alpha/gen/ldexp.c b/lib/libc/alpha/gen/ldexp.c
new file mode 100644
index 0000000..0cb9938
--- /dev/null
+++ b/lib/libc/alpha/gen/ldexp.c
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+/*	$NetBSD: ldexp.c,v 1.1 1995/02/10 17:50:24 cgd Exp $	*/
+
+/*
+ * Copyright (c) 1994, 1995 Carnegie-Mellon University.
+ * All rights reserved.
+ *
+ * Author: Chris G. Demetriou
+ * 
+ * Permission to use, copy, modify and distribute this software and
+ * its documentation is hereby granted, provided that both the copyright
+ * notice and this permission notice appear in all copies of the
+ * software, derivative works or modified versions, and any portions
+ * thereof, and that both notices appear in supporting documentation.
+ * 
+ * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 
+ * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 
+ * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
+ * 
+ * Carnegie Mellon requests users of this software to return to
+ *
+ *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
+ *  School of Computer Science
+ *  Carnegie Mellon University
+ *  Pittsburgh PA 15213-3890
+ *
+ * any improvements or extensions that they make and grant Carnegie the
+ * rights to redistribute these changes.
+ */
+
+#include <sys/types.h>
+#include <machine/ieee.h>
+#include <errno.h>
+#include <math.h>
+
+/*
+ * double ldexp(double val, int exp)
+ * returns: val * (2**exp)
+ */
+double
+ldexp(val, exp)
+	double val;
+	int exp;
+{
+	register int oldexp, newexp, mulexp;
+	union doub {
+		double v;
+		struct ieee_double s;
+	} u, mul;
+
+	/*
+	 * If input is zero, or no change, just return input.
+	 * Likewise, if input is Inf or NaN, just return it.
+	 */
+	u.v = val;
+	oldexp = u.s.dbl_exp;
+	if (val == 0 || exp == 0 || oldexp == DBL_EXP_INFNAN)
+		return (val);
+
+	/*
+	 * Compute new exponent and check for over/under flow.
+	 * Underflow, unfortunately, could mean switching to denormal.
+	 * If result out of range, set ERANGE and return 0 if too small
+	 * or Inf if too big, with the same sign as the input value.
+	 */
+	newexp = oldexp + exp;
+	if (newexp >= DBL_EXP_INFNAN) {
+		/* u.s.dbl_sign = val < 0; -- already set */
+		u.s.dbl_exp = DBL_EXP_INFNAN;
+		u.s.dbl_frach = u.s.dbl_fracl = 0;
+		errno = ERANGE;
+		return (u.v);		/* Inf */
+	}
+	if (newexp <= 0) {
+		/*
+		 * The output number is either a denormal or underflows
+		 * (see comments in machine/ieee.h).
+		 */
+		if (newexp <= -DBL_FRACBITS) {
+			/* u.s.dbl_sign = val < 0; -- already set */
+			u.s.dbl_exp = 0;
+			u.s.dbl_frach = u.s.dbl_fracl = 0;
+			errno = ERANGE;
+			return (u.v);		/* zero */
+		}
+		/*
+		 * We are going to produce a denorm.  Our `exp' argument
+		 * might be as small as -2097, and we cannot compute
+		 * 2^-2097, so we may have to do this as many as three
+		 * steps (not just two, as for positive `exp's below).
+		 */
+		mul.v = 0;
+		while (exp <= -DBL_EXP_BIAS) {
+			mul.s.dbl_exp = 1;
+			val *= mul.v;
+			exp += DBL_EXP_BIAS - 1;
+		}
+		mul.s.dbl_exp = exp + DBL_EXP_BIAS;
+		val *= mul.v;
+		return (val);
+	}
+
+	/*
+	 * Newexp is positive.
+	 *
+	 * If oldexp is zero, we are starting with a denorm, and simply
+	 * adjusting the exponent will produce bogus answers.  We need
+	 * to fix that first.
+	 */
+	if (oldexp == 0) {
+		/*
+		 * Multiply by 2^mulexp to make the number normalizable.
+		 * We cannot multiply by more than 2^1023, but `exp'
+		 * argument might be as large as 2046.  A single
+		 * adjustment, however, will normalize the number even
+		 * for huge `exp's, and then we can use exponent
+		 * arithmetic just as for normal `double's.
+		 */
+		mulexp = exp <= DBL_EXP_BIAS ? exp : DBL_EXP_BIAS;
+		mul.v = 0;
+		mul.s.dbl_exp = mulexp + DBL_EXP_BIAS;
+		val *= mul.v;
+		if (mulexp == exp)
+			return (val);
+		u.v = val;
+		newexp -= mulexp;
+	}
+
+	/*
+	 * Both oldexp and newexp are positive; just replace the
+	 * old exponent with the new one.
+	 */
+	u.s.dbl_exp = newexp;
+	return (u.v);
+}