diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index ca88155904f..01d2a0d8b54 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2009-06-18  Uros Bizjak  <ubizjak@gmail.com>
+
+	* convert.c (convert_to_integer): Convert (int)logb() into ilogb().
+
 2009-06-17  Olivier Hainque  <hainque@adacore.com>
 
 	* collect2.c (main): Use CONST_CAST2 to perform char ** to
diff --git a/gcc/convert.c b/gcc/convert.c
index b6a9d3dc531..8245e1647fb 100644
--- a/gcc/convert.c
+++ b/gcc/convert.c
@@ -482,6 +482,37 @@ convert_to_integer (tree type, tree expr)
 	}
     }
 
+  /* Convert (int)logb(d) -> ilogb(d).  */
+  if (optimize
+      && flag_unsafe_math_optimizations
+      && !flag_trapping_math && !flag_errno_math && flag_finite_math_only
+      && integer_type_node
+      && (outprec > TYPE_PRECISION (integer_type_node)
+	  || (outprec == TYPE_PRECISION (integer_type_node)
+	      && !TYPE_UNSIGNED (type))))
+    {
+      tree s_expr = strip_float_extensions (expr);
+      tree s_intype = TREE_TYPE (s_expr);
+      const enum built_in_function fcode = builtin_mathfn_code (s_expr);
+      tree fn = 0;
+       
+      switch (fcode)
+	{
+	CASE_FLT_FN (BUILT_IN_LOGB):
+	  fn = mathfn_built_in (s_intype, BUILT_IN_ILOGB);
+	  break;
+
+	default:
+	  break;
+	}
+
+      if (fn)
+        {
+	  tree newexpr = build_call_expr (fn, 1, CALL_EXPR_ARG (s_expr, 0));
+	  return convert_to_integer (type, newexpr);
+	}
+    }
+
   switch (TREE_CODE (intype))
     {
     case POINTER_TYPE:
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c16ecd04795..e0d1f6f421c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2009-06-18  Uros Bizjak  <ubizjak@gmail.com>
+
+	* gcc.dg/builtins-65.c: New test.
+
 2009-06-18  Janus Weil  <janus@gcc.gnu.org>
 
 	PR fortran/40451
diff --git a/gcc/testsuite/gcc.dg/builtins-65.c b/gcc/testsuite/gcc.dg/builtins-65.c
new file mode 100644
index 00000000000..7c6aa20bd84
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtins-65.c
@@ -0,0 +1,39 @@
+/* { dg-do link } */
+/* { dg-options "-O2 -ffast-math" } */
+
+extern int ilogbf (float);
+extern float logbf (float);
+extern int ilogb (double);
+extern double logb (double);
+extern int ilogbl (long double);
+extern long double logbl (long double);
+
+extern void link_error(void);
+
+void testf(float x)
+{
+  if ((int) logbf (x) != ilogbf (x))
+    link_error ();
+}
+
+void test(double x)
+{
+  if ((int) logb (x) != ilogb (x))
+    link_error ();
+}
+
+void testl(long double x)
+{
+  if ((int) logbl (x) != ilogbl (x))
+    link_error ();
+}
+
+int main()
+{
+  testf (2.0f);
+  test (2.0);
+  testl (2.0l);
+
+  return 0;
+}
+