Created by: wks

It has been proposed long ago that "everything the API can do should also be possible in the Mu IR".

This issue maintains a checklist of features not in the Mu IR. These functions should be gradually added to the IR.

Features in the API but not the IR:

• bundle loading
• stack introspection: current_func_ver, current_instruction, dump_keepalives
• OSR: pop_frame, push_frame
• Handle traps and undefined functions in Mu IR. It depends on how the Mu VM itself is implemented.
• Handle watchpoint in Mu IR: an instruction which is a no-op when disabled, but a (maybe limited kind of) Mu function call when enabled.

Things that can be done dynamically via handles in the API, but can only be done statically in the IR. I am not sure how dynamic Mu should be, or need to be, because some of the items below can be worked around with some Mu IR code, such as maintaining a hash table implemented in Mu IR, or writing wrapper functions.

• Opaque handle type: a handle that holds any Mu value. ref<T> can be a candidate for this purpose.
• Getting a Mu constant value (including constants, globals and functions) by its ID. This is a kind of introspection.
  • This can be done with a type argument: %c = GET_CONST <@T> %id, %c is a @T
  • Or return a handle: %ch = GET_CONST_H %id, %ch is a ref<void>
• Creating Mu heap objects by a type ID.
• Calling a Mu function (or constructing a Mu frame) with both the callee and the arguments as handles. This allows calling a Mu function with a run-time-determined arity and arg types.
• Dump keepalive variables.
  • This can be done with a type argument: %sixth_ka = GET_KEEPALIVE <@T> %frame 6
  • or return handle: %sixth_ka_handle = GET_KEEPALIVE_H %frame 6