--- /dev/null
+#include <limits.h>
+#include "libm.h"
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double logbl(long double x)
+{
+ return logb(x);
+}
+#else
+long double logbl(long double x)
+{
+ int i = ilogbl(x);
+
+ if (i == FP_ILOGB0)
+ return -1.0/fabsl(x);
+ if (i == FP_ILOGBNAN || i == INT_MAX)
+ return x * x;
+ return i;
+}
+#endif