Editing Self-modifying code (section)

==={{anchor|Synthesis}}Massalin's Synthesis kernel===
The Synthesis [[kernel (operating system)|kernel]] presented in [[Alexia Massalin]]'s [[Doctor of Philosophy|Ph.D.]] thesis<ref name="Massalin_1992_Synthesis"/><ref name="Henson_2008"/> is a tiny [[Unix]] kernel that takes a [[structured programming|structured]], or even [[object-oriented programming|object oriented]], approach to self-modifying code, where code is created for individual [[quaject]]s, like filehandles. Generating code for specific tasks allows the Synthesis kernel to (as a JIT interpreter might) apply a number of [[Compiler optimization|optimization]]s such as [[constant folding]] or [[common subexpression elimination]].<!-- Anyone want to go read the thesis and see what other optimizations Massalin lists? -->

The Synthesis kernel was very fast, but was written entirely in assembly. The resulting lack of portability has prevented Massalin's optimization ideas from being adopted by any production kernel. However, the structure of the techniques suggests that they could be captured by a higher level [[programming language|language]], albeit one more complex than existing mid-level languages. Such a language and compiler could allow development of faster operating systems and applications.

[[Paul Haeberli]] and Bruce Karsh have objected to the "marginalization" of self-modifying code, and optimization in general, in favor of reduced development costs.<ref name="Haeberli_1994_GraficaObscura"/>