Rewrite erand48() to put the random bits into the mantissa by simple

bitshifts instead of calling ldexp() three times.
(for ieee doubles only -- vax can't use it, so the old version
needs to stay around)
This removes the dependency on ldexp() which also didn't participate in
the usual __RENAME game, thus lead to confusion.
In addition, this version is almost 3 times as fast for me.

lib/libc/stdlib/erand48_ieee754.c

@@ -0,0 +1,47 @@
+/*	$NetBSD: erand48_ieee754.c,v 1.1 2006/03/22 21:06:03 drochner Exp $	*/
+
+/*
+ * Copyright (c) 1993 Martin Birgmeier
+ * All rights reserved.
+ *
+ * You may redistribute unmodified or modified versions of this source
+ * code provided that the above copyright notice and this and the
+ * following conditions are retained.
+ *
+ * This software is provided ``as is'', and comes with no warranties
+ * of any kind. I shall in no event be liable for anything that happens
+ * to anyone/anything when using this software.
+ */
+
+#include <sys/cdefs.h>
+#if defined(LIBC_SCCS) && !defined(lint)
+__RCSID("$NetBSD: erand48_ieee754.c,v 1.1 2006/03/22 21:06:03 drochner Exp $");
+#endif /* LIBC_SCCS and not lint */
+
+#include "namespace.h"
+
+#include <assert.h>
+#include <machine/ieee.h>
+
+#include "rand48.h"
+
+#ifdef __weak_alias
+__weak_alias(erand48,_erand48)
+#endif
+
+double
+erand48(unsigned short xseed[3])
+{
+	union ieee_double_u u;
+
+	_DIAGASSERT(xseed != NULL);
+
+	__dorand48(xseed);
+	u.dblu_dbl.dbl_sign = 0;
+	u.dblu_dbl.dbl_exp = DBL_EXP_BIAS; /* so we get [1,2) */
+	u.dblu_dbl.dbl_frach = ((unsigned int)xseed[0] << 4)
+				| ((unsigned int)xseed[1] >> 12);
+	u.dblu_dbl.dbl_fracl = (((unsigned int)xseed[1] & 0x0fff) << 20)
+				| ((unsigned int)xseed[2] << 4);
+	return (u.dblu_d - 1);
+}