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diff --git a/libm/s_ilogb.c b/libm/s_ilogb.c
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+/* @(#)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.
+ * ====================================================
+ */
+
+#if defined(LIBM_SCCS) && !defined(lint)
+static char rcsid[] = "$NetBSD: s_ilogb.c,v 1.9 1995/05/10 20:47:28 jtc 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 "math_private.h"
+
+#ifdef __STDC__
+ int ilogb(double x)
+#else
+ int ilogb(x)
+ double x;
+#endif
+{
+ int32_t hx,lx,ix;
+
+ GET_HIGH_WORD(hx,x);
+ hx &= 0x7fffffff;
+ if(hx<0x00100000) {
+ GET_LOW_WORD(lx,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;
+}