Introduction to Codegen with llvmlite

This is a small introduction to how an AST would use llvmlite to generate llvm-ir (llir).

This is technically turing complete (I think). It is missing features a language would likely want.

There are of course several TODO/exercise comments left in the code as challenges for the reader.

This was shared on the Compilers and Interpreters discord server on 01/06/2024 (M/D/Y) If you see this before that date, come join us to learn more!

Requirements

• python 3.11.x (uses a 3.11 features + a feature that was removed in 3.12)
• pip (do pip install -r requirements.txt)

Things not included here

These things are intentionally not included in this example.

• Lexing
• Parsing
• Emitting to a file
• Identified Struct types
• "Advanced" llvm instructions like gep or phi
• Type checking (there is only 1 type present)
• Optimization passes
• JIT / the execution engine
• Emiting object file
• Linking (to create an executable)

Instructions covered

• icmp (>, <, & ==. != also kind-of used)
• alloca
• store
• ret (but not ret void)
• load
• br (cbranch and branch)
• add
• sub
• mul
• sdiv
• zext
• Function definition
• Creating blocks & positioning.
• Doing all allocations at the start of a function.
• An extremely basic Type system that includes 1 type.

Additional resources.

• Compilers and Interpreters discord (Invite)

• llvmlite docs: user-guide

• Mapping High-level Constructs to LLVM-IR

• This is useful for those unaffiliated with ANSI
  Info about ANSI escape codes

• LLVM has bad documentation in my experience
  LLVM language reference

• What is SSA

• This explains __slots__. Most people don't know about this python feature
  What is __slots__

• A little self-plug, but I do use llvmlite here. Please consider starring the project!
  BCL

Reuse of this code

If you wish to reuse this code, you may do so. The only thing I ask is that you credit me on your project's readme or wherever it makes sense to add the attribution.