1) bare invoke
This opcode assumes P0 = Sub, P1 = Continuation
2) bare invokecc
This opcode assumes P0 = Sub
3) invoke Px
This opcode assumes P1 = Continuation, but it has a double usage: call a
coroutine (not the first time) and yield from a coroutine with this code
interpinfo Px, .INTERPINFO_CURRENT_SUB
Instead I'd like to have distinct opcodes, that carry the effects on
operands clearly in their signature. The replacement for above would be:
1) invoke PSub, PCont # call sub with given continuation
2) invokecc PSub # call sub, create continuation - exists
3a) invoke PCoro # call sub, leave continuation as is
3b) yield # yield results from a coroutine
3a) exists too, but it currently picks up a continuation in P1.
Rational: the register allocator has to track the usage of all symbols.
For all the implicit register usage, extra code is needed that tracks
register usage. See trunk imcc/cfg.c for details.