Careful use of the compiler optimize qualities described above or special declarations may significantly improve the performance of your code. However it is not recommended that you simply experiment with the effect of adding declarations. It is more productive to work systematically:
:explaindeclarations to make the compiler generate optimization hints, and
The most important tool for speeding up programs is the Profiler. You use the profiler to find the bottlenecks in the program, and then optimize these bottlenecks by helping the compiler to produce better code.
The remainder of this section describes some specific ways to produce efficient compiled code with LispWorks.
LispWorks User Guide and Reference Manual - 21 Dec 2011