auto import from //depot/cupcake/@135843
diff --git a/s_ilogb.c b/s_ilogb.c
new file mode 100644
index 0000000..240f9bf
--- /dev/null
+++ b/s_ilogb.c
@@ -0,0 +1,46 @@
+
+/* @(#)s_ilogb.c 1.3 95/01/18 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunSoft, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+/* ieee_ilogb(double x)
+ * return the binary exponent of non-zero x
+ * ieee_ilogb(0) = 0x80000001
+ * ieee_ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
+ */
+
+#include "fdlibm.h"
+
+#ifdef __STDC__
+ int ieee_ilogb(double x)
+#else
+ int ieee_ilogb(x)
+ double x;
+#endif
+{
+ int hx,lx,ix;
+
+ hx = (__HI(x))&0x7fffffff; /* high word of x */
+ if(hx<0x00100000) {
+ lx = __LO(x);
+ if((hx|lx)==0)
+ return 0x80000001; /* ieee_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;
+}