Who does put receiver object onto the operand stack in bytecode interpreter?

[Colin(Du Li) ()]

Hi, I have a question about the c++ interpreter.
For an "invokevirtual" method, the operand stack is like:
    ..., objectref, [arg1, [arg2 ...]]

I know the arguments are put onto the stack by some "load" instructions explicitly. But, how is the objectref (receiver object) put onto the stack? Who did that and when?

Thanks a lot!

Colin