i guess this comment is misleading in shadowframe class in stack h this is a two part array number of vregs  holds the raw virtual registers  and each element here is always bytes number of vregs  number of vregs holds only reference registers  each element here is ptr sized  in other words when a primitive is stored in vx  the second  reference  part of the array will be null  when a reference is stored in vx  the second  reference  part of the array will be a copy of vx  uint t vregs 