It’s a VM you need. Not a compiler. The Pharo Project’s VM [0] is in C, and not that extensive. Most of the good stuff is written in smalltalk.

[0]: https://github.com/pharo-project/pharo-vm

https://github.com/Cuis-Smalltalk/Cuis-Smalltalk-Dev

Download and search !Compiler in:

    ./Cuis7-0-main/CuisImage/Cuis7.0.sources

:and you'll see the commented Compiler class source code:

"The compiler accepts Smalltalk source code and compiles it with respect to a given class. The user of the compiler supplies a context so that temporary variables are accessible during compilation."

It would be easier to install Cuis Smalltalk and use the Smalltalk browsers to explore the Compiler code.