Intro:
CF Bolz-Tereick wrote some excellent posts in which they introduce a small IR and optimizer and extend it with allocation removal. We also did a live stream together in which we did some more heap optimizations.
In this blog post, I’m going to write a small abtract interpreter for the Toy IR and then show how we can use it to do some simple optimizations. It assumes that you are familiar with the little IR, which I have reproduced unchanged in a GitHub Gist.
Abstract interpretation is a general framework for efficiently computing properties that must be true for all possible executions of a program. It’s a widely used approach both in compiler optimizations as well as offline static analysis for finding bugs. I’m writing this post to pave the way for CF’s next post on proving abstract interpreters correct for range analysis and known bits analysis inside PyPy.