Context-threading is a JIT technique. CRuby can optionally use call-threading where each op is a function and dispatch is an infinite loop of function calls. It's not the default since direct or token threading are faster but it's there.

Call-threading looks like this:

  while(1) { interpreter_state = *virtual_program_counter++(interpreter_state); }

There's an indirect jump here.

With context-threading you JIT very simple code which looks like this and has only direct calls:

  interpreter_state = put1(interpreter_state);
  interpreter_state = put1(interpreter_state);
  interpreter_state = plus(interpreter_state);