8023542: Test java/io/File/CheckPermission.java fails due to unfinished...

8023542: Test java/io/File/CheckPermission.java fails due to unfinished recursion (java.lang.StackOverflowError) when JIT'ed code (-client,-server) is running
Summary: Move null check before klass reference materialization in checkcast
Reviewed-by: kvn, roland

src/cpu/x86/vm/c1_LIRAssembler_x86.cpp

@@ -1724,14 +1724,6 @@ void LIR_Assembler::emit_typecheck_helper(LIR_OpTypeCheck *op, Label* success, L
   }
 
   assert_different_registers(obj, k_RInfo, klass_RInfo);
-  if (!k->is_loaded()) {
-    klass2reg_with_patching(k_RInfo, op->info_for_patch());
-  } else {
-#ifdef _LP64
-    __ mov_metadata(k_RInfo, k->constant_encoding());
-#endif // _LP64
-  }
-  assert(obj != k_RInfo, "must be different");
 
   __ cmpptr(obj, (int32_t)NULL_WORD);
   if (op->should_profile()) {
@@ -1748,6 +1740,14 @@ void LIR_Assembler::emit_typecheck_helper(LIR_OpTypeCheck *op, Label* success, L
   } else {
     __ jcc(Assembler::equal, *obj_is_null);
   }
+
+  if (!k->is_loaded()) {
+    klass2reg_with_patching(k_RInfo, op->info_for_patch());
+  } else {
+#ifdef _LP64
+    __ mov_metadata(k_RInfo, k->constant_encoding());
+#endif // _LP64
+  }
   __ verify_oop(obj);
 
   if (op->fast_check()) {