XSRETURN(n) is just setting the stack pointer and returns, so if you already set up the correct stack pointer with XPUSHs() then there is indeed no need to call XSRETURN(n). XSRETURN(n) is usefull if you return fewer values than you had input parameters and just set your return values by direct assignment to ST(i). Or even if you called EXTEND(SP, n), and then assigned to ST(i), which is slightly more efficient than a long series of XPUSHs() calls.