LLVM in 100 Seconds

LLVM streamlines the arduous process of transforming human-friendly code into machine-ready instructions across diverse architectures. It unifies the complex steps involved in translating source code into optimized machine code, addressing the gap between intuitive programming languages and hardware requirements. Created in 2003 by graduate student Chris Lattner at the University of Illinois, LLVM now underpins essential tools like clang.

Intermediate Representation converts varied high-level languages like C, C++, Rust, Swift, and Julia into a single, language-agnostic code format. This common IR enables even distinct languages such as CUDA and Ruby to utilize the same analysis and optimization tools before being translated into machine-specific instructions. The compiler’s process is streamlined into three stages: a front end that parses source code into IR, a middle section that refines and optimizes it, and a back end that produces tailored machine code.

Begin by installing LLVM and preparing a C file to set the stage for an innovative programming language. A lexer transforms raw source code into tokens such as literals, identifiers, and operators, laying the groundwork for an abstract syntax tree built with dedicated node classes. A parser then organizes these tokens into a structured tree, which is converted into an intermediate representation using LLVM primitives that remain independent of specific hardware. Optimization passes refine this representation through measures like dead code elimination and scalar replacement before a backend module emits platform-agnostic object code.