This repository is the official compiler for the Cairo programming language, a Turing-complete language designed for provable computation (zero-knowledge proofs). It compiles Cairo source through a multi-stage pipeline: parsing (via LALRPOP), semantic analysis with type inference and trait resolution, lowering to a control-flow graph with extensive optimizations (CSE, constant folding, inlining, match optimization, gas redeposit), generation of the Sierra intermediate representation (a safe, bounded subset for ZK provability), and final compilation to CASM (Cairo Assembly) for execution on the Cairo VM. The compiler uses the Salsa incremental computation framework for query-based caching and is split into 40+ crates organized by compiler phase (parser, semantic, lowering, sierra-generator, sierra-to-casm, etc.). It also includes a full toolchain for Starknet smart contract development, with plugins for contracts, storage, events, and ABI generation. CLI tools (cairo-compile, cairo-run, sierra-compile, starknet-compile, cairo-test, cairo-format) provide end-to-end functionality. The standard library ('corelib'), written in Cairo, provides fundamental types, collections, hash functions, and Starknet-specific primitives. The codebase demonstrates high craftsmanship with clean abstractions, a generic dataflow analysis framework, deterministic hash map utilities, and a reusable graph algorithm library. It is actively maintained with extensive CI, benchmarks, and a golden-file test infrastructure.