Comment by fwsgonzo

  function fib(n, acc, prev)
    if (n < 1) then
      return acc
    else
      return fib(n - 1, prev + acc, acc)
    end
  end
  print(fib(50, 0, 1))

  $ ./rvlinux -P ~/github/LuaRiscvJIT/src/luajit -- test.lua
  12586269025
  >>> Program exited, exit code = 0 (0x0)
  Runtime: 0.281ms   (Use --accurate for instruction counting)
  Pages in use: 429 (1716 kB virtual memory, total 2674 kB)

It's definitely working!