I think they're suggesting programming in implicit CPS/callback style. Eg:

  int bar(int i) { return i+1; }
  /* bar takes a implicit return address in [esp+0] */
  noreturn foo((*ra)(int),int x)
    {
    /* where (*)(RetType) is a return address */
    int y = bar(x); /* x86 call pushes eip */
    ra return bar(y); /* pseudo-tail-call (push ra) */
    }
  int quux(int x)
    {
    (*ret)(int); ret = (return); /* get implicit RA */
    foo(ret,x);
    } // unreachable

You'd also need to adjust the stack and/or frame pointer though, which is probably going to be the hard part.