pub const HOST_CALL: u32 = 26;Expand description
host_call(instance_slot=φ[7], endpoint_idx=φ[8]) — push a
child InstanceEntry from the Cap::Instance at
instance_slot, move the caller’s slot[0] into the child’s
slot[0]. The interpreter exits with
ExitReason::HostCall(HOST_CALL); the drive_and_translate
loop re-enters Interpreter::run on the new top frame. On
child HALT the loop pops the child, reflects its slot[0]
back into the caller’s slot[0], and resumes the caller.