The frame pointer, instruction pointer and stack pointer are all part of the VM state.
We either need to store them in memory, or pass them as an argument/return value when calling or returning from a C function (or jitted code).

The only reason we passed these values as arguments or return value was for efficiency. It reduces the number of memory accesses at the point of transfer. If it turns out that most callees don't need them, we can just remove the parameter from the API.

The difference with this PR is that the return value is meaningful, not just a cached value. Thenext_instr cannot be derived from theprev_instr stored on the frame. If the last instruction was a jump thennext_instr != prev_instr + 1.

Things would be neater if these were all explicit and we didn't have to recover one or the other throughtstate->current_frame.

tstate->current_frame is the current frame and holds the previous instruction and stack pointers.
Unless we are passing values in registers for performance, we don't want to make copies that could get out of sync.

Thanks for the changes.

I believe we decided offline to hold off on this until Brandt has had an opportunity to change_PyOptimizer_BackEdge not to call the executor, and to modifyJUMP_BACKWARD instead to "deoptimize" toENTER_EXECUTOR. (Or to find out that there was a reason why things are the way they are.)

This is now obsolete