presto-main/src/main/java/io/prestosql/operator/aggregation/state/StateCompiler.java/StateCompiler/generateInstanceSize
class StateCompiler:    private static FieldDefinition generateInstanceSize(ClassDefinition definition)
    {
        // Store instance size in static field
        FieldDefinition instanceSize = definition.declareField(a(PRIVATE, STATIC, FINAL), "INSTANCE_SIZE", long.class);
        definition.getClassInitializer()
                .getBody()
                .comment("INSTANCE_SIZE = ClassLayout.parseClass(%s.class).instanceSize()", definition.getName())
                .push(definition.getType())
                .invokeStatic(ClassLayout.class, "parseClass", ClassLayout.class, Class.class)
                .invokeVirtual(ClassLayout.class, "instanceSize", int.class)
                .intToLong()
                .putStaticField(instanceSize);
        return instanceSize;
    }