We follow the slow mutation of an intermediate representation from a
well known quad-based form to a sparse graph-based form.  The final form is 
similar to an operator-level Program Dependence Graph or Gated Single 
Assignment form.  The final form contains all the information required to 
execute the program.  What is more important, the graph form explicitly 
contains use-def information.  Analyses can use this information directly 
without having to calculate it.  Transformations modify the use-def 
information directly, without requiring separate steps to modify the 
intermediate representation and the use-def information.