(FAST-SAVE '(PCS-CODE-BLOCK ...) [dest|])

Assuming the given PCS-CODE-BLOCK is correct (as are those given by COMPILE), FAST-SAVE outputs the fast-load form of the code-block to port dest| or to the default output-port if no dest| is given. This is the low-level primitive used by FAST-SAVE-FILE, as COMPILE is the low-level primitive used by COMPILE-FILE.