call optimize_cf() to delete dead-code that might arise after cond_eval

[r19906]

ir/opt/condeval.c

@@ -696,14 +696,19 @@ void opt_cond_eval(ir_graph* irg)
 		changed |= rerun;
 	} while (rerun);
 
+	clear_using_irn_visited(irg);
+	clear_using_irn_link(irg);
+
 	if (changed) {
 		/* control flow changed, some blocks may become dead */
 		set_irg_outs_inconsistent(irg);
 		set_irg_doms_inconsistent(irg);
 		set_irg_extblk_inconsistent(irg);
 		set_irg_loopinfo_inconsistent(irg);
+
+		/* Dead code might be created. Optimize it away as it is dangerous
+		 * to call optimize_df() an dead code. */
+		optimize_cf(irg);
 	}
 
-	clear_using_irn_visited(irg);
-	clear_using_irn_link(irg);
 }