I appreciate the effort to have a web page talking about writing your own compiler. Right now, I'm looking for an easy way to add define-use chains to a compiler. I know it involves breaking code into blocks and tracing through the code looking for use of the same variables. This tutorial is good because it adds a symbol table on each block level, which helps in differentiating names that are re-used in a block and don't refer to other variables of the same name. Does anyone know of code that makes clear what is involved in def-use for a variable without saying "this is an exercise for the reader" ?