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Pylir

pylir is an optimizing ahead-of-time compiler for python. Goal of the project is therefore to compile python code to native executables that run as fast as possible through the use of optimizations. Despite being ahead-of-time one of the goals is to achieve as high of language conformance as is possible and reasonable.

Usage

pylir has a GCC style command line interface, with all options listable via pylir --help. To compile a python program, simply pass the main module of your python program to the compiler: pylir test.py. This will then produce an executable called test (test.exe on Windows). Using the -o flag you can change the name of the binary.

The current default is to not apply any optimizations. To enable optimizations pass -O3 as a command line flag.

Status

Pylir is very much work in progress. The Frontend parts were first completed and are almost fully complete and support parsing Python 3.9 code. The compiler can already compile many builtin types and some functions from the builtins namespace such as print are already available. Some operators are already implemented but others are yet to be implemented. Exception handling is complete and a very basic Garbage Collector is already implemented.

A good way to check on current language conformance is to take a look at the testsuite for it here.

Most time is currently spent working on the optimizer.

Technologies used

Pylir is written from scratch in C++17 and uses following notable technologies:

  • The bulk of the code makes use of MLIR, which is used to create a high level IR that precisely models the semantics of Python code. Most of the optimizations are done in MLIR, which then gradually lowers it to LLVM
  • LLVM is used as the backend of the compiler. Once the MLIR optimizer has lowered the code down to a C/C++ Abstraction level, LLVM runs its optimizer to apply low level optimizations and finally emits native machine code for the requested target. The project also makes use of LLVMs excellent, Garbage collection support via statepoints, to support 100% accurate Garbage Collection as well as relocating Garbage Collectors in the future.

Building from Source

Building from Source requires a C++17 Compiler, cmake and the correct version of MLIR, LLVM and LLD. MLIR is currently a very fast moving project and Pylirs source code tries to closely track tip of the tree. The required revision tested to build a specific version of pylir is always documented here. Pylir requires LLVM, MLIR and LLD to be built at this revision, and then be able to be found via cmake. Via the CMAKE_PREFIX_PATH variable, one can point cmake at the LLVM and MLIR installation.

Quick tour of the source code

src     - Contains all the C++ code making up the compiler
`-pylir
  |-CodeGen     - Contains the Frontend AST to MLIR generation
  |-Diagnostics     - Diagnostics Infra used by the Lexer and Parser
  |-Interfaces      - Common Info used throughout the compiler
  |-Lexer       - The Python Lexer
  |-LLVM        - Custom LLVM passes and plugins used mainly for Garbage Collection
  |-Main        - The main program and driver of the compiler
  |-Optimizer   - The optimizer utilizing MLIR with Dialect, Transformation Passes, Analysis Passes and Dialect lowering
  |-Parser      - The Python Parser
  |-Runtime     - Runtime code linked into the final executable, containing a C++ API to interact with python objects as
  |               well as support code that implements Exception Handling and Garbage Collection
  `-Support     - Various utility code and data structures used by the compiler and runtime.