For now using the checkpoint or switchcpu pseudo instructions will return control...

For now using the checkpoint or switchcpu pseudo instructions will return control to Python, returning the cause to be the instruction name.  The user's script must then interpret the reason for exiting the simulation loop and handle the action accordingly.  This may change in the future.

src/sim/pseudo_inst.cc:
    Exit sim loop with a specific string to indicate to Python what caused the exit.  The user's script needs to interpret the exit events and handle them as desired.

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extra : convert_revision : 8eb4a42285dacb3ada3a791173c605b5acb78598