Patent US 7,017,154

A post-link optimization method for renaming non-volatile registers with unused volatile registers, then removing the non-volatile register store/restore instructions from a function prolog/epilog. The volatile registers are saved before each function call and restored immediately afterwards. The optimization method is worthwhile if all of the call instructions are rarely invoked relative to the function prolog/epilog. The method requires that the hot function be disassembled, but does not require the full control flow graph.