Check out the Synthesis Kernel: http://en.wikipedia.org/wiki/Self-modifying_code#Massalin.27s_Synthesis_kernel http://en.wikipedia.org/wiki/Self-modifying_code#

Check out the Synthesis Kernel: http://en.wikipedia.org/wiki/Self-modifying_code#Massalin.27s_Synthesis_kernel http://en.wikipedia.org/wiki/Self-modifying_code#Massalin.27... It uses run time information to modify its own code to perform optimally. It was incredibly fast, but the difficulty in using SMC far outweighs the benefits in most applications.