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What is LLVM? The power behind Swift, Rust, Clang, and more

The development landscape is a bustling hive of new and improved languages, such as Mozilla’s Rust and Apple’s Swift. LLVM compilers are crucial for language development as they automate tasks like compiler creation and creating architecture-specific optimizations. The open licencing of LLVM enables its reuse as software or as a service.

What is LLVM?

LLVM is a library that provides an API for producing machine-native code in the intermediate representation (IR) format. It includes primitives for generating typical structures and patterns in programming languages such as functions, global variables, coroutines, and C foreign-function interfaces. Its internal representation contains standard components and metaphors for building coroutines and communicating with C libraries. LLVM implementations can be used by developers to focus on certain language aspects.

LLVM is planned to be adaptable

LLVM is a portable and architecture-independent high-level assembly language. It provides primitives closely tied to system hardware and can therefore be adapted to almost any system architecture. Unlike C, LLVM’s IR is meant to be mobile by providing basics that are not constrained by the maximum bit width of the underlying hardware. It also eliminates the requirement to match output to a certain processor’s guidance set. Because LLVM is architecture-neutral, it can handle hardware of all sorts, both present and future.

How LLVM is used in programming languages

The most typical app for LLVM is an AOT language compiler. For example, Clang converts C and C++ into native programs. However, LLVM allows for additional possibilities.

LLVM just-in-time execution

Julia and Numba are Python math accelerator libraries that employ JIT compilation to generate code while running. Julia interacts with the user through the REPL or interactive prompts, whereas Numba can construct Numba-decorated code early in time. Some are testing LLVM as a JIT compiler to get a fivefold speed gain.

LLVM-based automatic code improvement

LLVM not only converts IR to native machine code, but it also optimizes the code programmatically throughout the linking process, enabling aggressive optimizations like function inlining, invalid code eradication, and loop unrolling. These functionalities can be activated or deactivated as needed.

LLVM-based domain-specific languages

LLVM is a sophisticated compiler tool that improves performance for universal and vertical languages. Emscripten transforms LLVM IR code to JavaScript, allowing Rust to compile to WebAssembly directly. Domain-specific extensions to current languages can also be provided using LLVM. The Multi-Level Intermediate Representation project’s goal is to translate complicated data structures into LLVM IR in order to accelerate the compilation of complex procedures.

Programming using LLVM

LLVM is developed in a language connected with its libraries, such as C or C++; however, other languages can be called straight into C libraries. LLVM development libraries are available in Rust.

What does LLVM fail to offer?

LLVM, unlike many other tools, does not analyse a language’s grammar. It excludes the software environment around a certain language, such as installing binaries, managing packages, and upgrading the toolchain. It also lacks basics for managing waste memory, however, it does give tools for building it by allowing code to be tagged with metadata.


This does not rule out the possibility of LLVM introducing native garbage collection solutions in the future. LLVM is growing quickly, with a major upgrade every six months. Since many modern languages integrate LLVM into their development cycles, the rate of development is likely to accelerate.