The Four Phases of Compilation
First, what is meant by the term "compilation" depends on the selected injection strategy.
For bytecode rewriting, compilation means generating a new instrumented variation of the passed program.
For direct engine support, compilation means compiling the .mm script to a .v3 program that interfaces with an engine to instrument the program dynamically.
The original program is not touched when using this strategy.
The first three phases of whamm! compilation are identical for both strategies.
The final emit phase is where the variation lies.
This is because "emitting" for bytecode rewriting means using the walrus library to insert new instructions into the program.
Whereas "emitting" for direct engine support means emitting Virgil code to specify the instrumentation probes in a new format that leverages the target engine's instrumentation API.
These are the four phases of compilation: