diff -r f95d63e2154a -r ac637b7220d1 src/cpu/x86/vm/c1_LIRGenerator_x86.cpp
--- a/src/cpu/x86/vm/c1_LIRGenerator_x86.cpp	Tue Nov 23 13:22:55 2010 -0800
+++ b/src/cpu/x86/vm/c1_LIRGenerator_x86.cpp	Tue Nov 30 23:23:40 2010 -0800
@@ -1151,9 +1151,12 @@
     stub = new SimpleExceptionStub(Runtime1::throw_class_cast_exception_id, obj.result(), info_for_exception);
   }
   LIR_Opr reg = rlock_result(x);
+  LIR_Opr tmp3 = LIR_OprFact::illegalOpr;
+  if (!x->klass()->is_loaded() || UseCompressedOops) {
+    tmp3 = new_register(objectType);
+  }
   __ checkcast(reg, obj.result(), x->klass(),
-               new_register(objectType), new_register(objectType),
-               !x->klass()->is_loaded() ? new_register(objectType) : LIR_OprFact::illegalOpr,
+               new_register(objectType), new_register(objectType), tmp3,
                x->direct_compare(), info_for_exception, patching_info, stub,
                x->profiled_method(), x->profiled_bci());
 }
@@ -1170,9 +1173,12 @@
     patching_info = state_for(x, x->state_before());
   }
   obj.load_item();
+  LIR_Opr tmp3 = LIR_OprFact::illegalOpr;
+  if (!x->klass()->is_loaded() || UseCompressedOops) {
+    tmp3 = new_register(objectType);
+  }
   __ instanceof(reg, obj.result(), x->klass(),
-                new_register(objectType), new_register(objectType),
-                !x->klass()->is_loaded() ? new_register(objectType) : LIR_OprFact::illegalOpr,
+                new_register(objectType), new_register(objectType), tmp3,
                 x->direct_compare(), patching_info, x->profiled_method(), x->profiled_bci());
 }