http://www.chiark.greenend.org.uk/doc/cmucl-docs/compiler-hint.html http://www.chiark.greenend.org.uk/doc/cmucl-docs/compiler-hi... is mostly applicable to SBCL

http://www.chiark.greenend.org.uk/doc/cmucl-docs/compiler-hint.html http://www.chiark.greenend.org.uk/doc/cmucl-docs/compiler-hi... is mostly applicable to SBCL last I checked. It gives an idea of what kind of cleverness the compiler can undertake.