Transmitting continuation values

The p_swcv instruction is used to send a continuation value to the forked hart.
The value is written to the forked hart stack (the stack is empty as the forked hart has not started yet).
The second source of the instruction is a constant which represents the destination offset in the stack.
Any register can be transmitted to the forked hart.
At least register ra (holding the join address) and register t0 (holding the join hart identification) should be transmitted.

The p_lwcv instruction is used to receive a continuation value from the forking hart.
The value is read from the current hart stack.
The second source of the instruction is a constant which represents the source offset in the stack.

In the following example, registers ra and t0 are transmitted from core 0, hart 0 to core 0, hart 1 and then from core 0, hart 1 to core 1, hart 0. They are respectively placed at address 0 and 4 of the receiving hart stack.