diff --git a/libm/src/s_ilogb.c b/libm/src/s_ilogb.c
new file mode 100644
index 0000000..bd4a44b
--- /dev/null
+++ b/libm/src/s_ilogb.c
@@ -0,0 +1,49 @@
+/* @(#)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[] = "$FreeBSD: src/lib/msun/src/s_ilogb.c,v 1.9 2004/10/09 17:14:28 stefanf Exp $";
+#endif
+
+/* ilogb(double x)
+ * return the binary exponent of non-zero x
+ * ilogb(0) = FP_ILOGB0
+ * ilogb(NaN) = FP_ILOGBNAN (no signal is raised)
+ * ilogb(inf) = INT_MAX (no signal is raised)
+ */
+
+#include <limits.h>
+
+#include "math.h"
+#include "math_private.h"
+
+	int ilogb(double x)
+{
+	int32_t hx,lx,ix;
+
+	EXTRACT_WORDS(hx,lx,x);
+	hx &= 0x7fffffff;
+	if(hx<0x00100000) {
+	    if((hx|lx)==0)
+		return FP_ILOGB0;
+	    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 if (hx>0x7ff00000 || lx!=0) return FP_ILOGBNAN;
+	else return INT_MAX;
+}