release/1.1.5.1_cvsreleng/1

1 files changed, 56 insertions, 0 deletions

diff --git a/lib/msun/src/s_ilogb.c b/lib/msun/src/s_ilogb.c
new file mode 100644
index 000000000000..6ca76107928a
--- /dev/null
+++ b/lib/msun/src/s_ilogb.c
@@ -0,0 +1,56 @@
+/* @(#)s_ilogb.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+#ifndef lint
+static char rcsid[] = "$Id: s_ilogb.c,v 1.1.1.1 1994/05/06 00:20:05 gclarkii Exp $";
+#endif
+
+/* ilogb(double x)
+ * return the binary exponent of non-zero x
+ * ilogb(0) = 0x80000001
+ * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
+ */
+
+#include "math.h"
+#include <machine/endian.h>
+
+#if BYTE_ORDER == LITTLE_ENDIAN
+#define n0	1
+#else
+#define n0	0
+#endif
+
+#ifdef __STDC__
+	int ilogb(double x)
+#else
+	int ilogb(x)
+	double x;
+#endif
+{
+	int hx,lx,ix;
+
+	hx  = (*(n0+(unsigned*)&x))&0x7fffffff;	/* high word of x */
+	if(hx<0x00100000) {
+	    lx = *(1-n0+(int*)&x);
+	    if((hx|lx)==0) 
+		return 0x80000001;	/* ilogb(0) = 0x80000001 */
+	    else			/* subnormal x */
+		if(hx==0) {
+		    for (ix = -1043; lx>0; lx<<=1) ix -=1;
+		} else {
+		    for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
+		}
+	    return ix;
+	}
+	else if (hx<0x7ff00000) return (hx>>20)-1023;
+	else return 0x7fffffff;
+}