llvmir

LLVM IR, or LLVM Intermediate Representation, is a low-level, statically typed representation of program semantics. It serves as a universal intermediate language for various compilers within the LLVM compiler infrastructure. LLVM IR is designed to be "three-address code," meaning each instruction typically performs at most one operation and produces at most one temporary result. This structure facilitates extensive analysis and transformation by compiler optimizations.

The IR can be represented in a human-readable textual format, which is useful for debugging and understanding compiler behavior. It can also be represented in a compact binary format for more efficient storage and loading. LLVM IR is crucial because it decouples the front-end (language parsing and semantic analysis) from the back-end (code generation for specific target architectures). This allows developers to create new front-ends for different programming languages (like C++, Rust, Swift) that can then leverage LLVM's mature back-end optimizations and support for a wide range of hardware targets without needing to reimplement optimization passes or code generators for each new language.

Key features of LLVM IR include its well-defined instruction set, type system, and control flow graph representation. It supports various data types, including integers, floating-point numbers, pointers, and aggregates. The control flow is managed through basic blocks, which are sequences of instructions ending in a control flow instruction like a branch or return. This structured approach makes it amenable to various compiler optimizations, such as dead code elimination, loop optimizations, and function inlining, ultimately leading to more efficient machine code.