avoid non-leaf typecheck in GetClassNode for PythonObject for small polymorphism

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/object/GetClassNode.java

@@ -85,12 +85,6 @@ protected PythonClass getIt(@SuppressWarnings("unused") GetSetDescriptor object)
         return getCore().lookupType(PythonBuiltinClassType.GetSetDescriptor);
     }
 
-    @Specialization(guards = "!isNone(object)")
-    protected PythonClass getIt(PythonObject object,
-                    @Cached("createIdentityProfile()") ValueProfile profile) {
-        return profile.profile(object.getPythonClass());
-    }
-
     @Specialization(assumptions = "singleContextAssumption()")
     protected PythonClass getIt(@SuppressWarnings("unused") PNone object,
                     @Cached("getIt(object)") PythonClass klass) {
@@ -197,6 +191,28 @@ protected PythonClass getIt(PythonNativeObject object,
         return getNativeClassNode.execute(object);
     }
 
+    @SuppressWarnings("unchecked")
+    protected Class<? extends PythonObject> asPythonObjectSubclass(Class<? extends Object> clazz) {
+        Class<? extends PythonObject> retval = null;
+        if (PythonObject.class.isAssignableFrom(clazz)) {
+            retval = (Class<? extends PythonObject>) clazz;
+        }
+        return retval;
+    }
+
+    @Specialization(guards = {"object.getClass() == cachedClass"}, limit = "5")
+    protected PythonClass getPythonClassCached(Object object,
+                    @Cached("asPythonObjectSubclass(object.getClass())") Class<? extends PythonObject> cachedClass,
+                    @Cached("createIdentityProfile()") ValueProfile profile) {
+        return profile.profile(cachedClass.cast(object).getPythonClass());
+    }
+
+    @Specialization(replaces = "getPythonClassCached")
+    protected PythonClass getPythonClassGeneric(PythonObject object,
+                    @Cached("createIdentityProfile()") ValueProfile profile) {
+        return profile.profile(object.getPythonClass());
+    }
+
     @Specialization(guards = "isForeignObject(object)", assumptions = "singleContextAssumption()")
     protected PythonClass getIt(@SuppressWarnings("unused") TruffleObject object,
                     @Cached("getIt(object)") PythonClass klass) {