A Gentle Introduction to LLVM IR · mcyoung

The other day, I saw this tweet. In it, Andrew Gallant argues that reaching for LLVM IR, instead of assembly, is a useful tool for someone working on performance. Unfortunately, learning material on LLVM is usually aimed at compiler engineers, not generalist working programmers. Now, I’m a compiler engineer, so my answer is of course you should know your optimizer’s IR. But I do think there’s a legitimate reason to be able to read it, in the same way that being able to read assembly to understand what your processor is doing is a powerful tool. I wrote an introduction to assembly over a year ago (still have to finish the followups… 💀), which I recommend reading first. Learning LLVM IR is similar, but it helps you understand what your compiler is doing to create highly optimized code. LLVM IR is very popular, and as such well-documented and reasonably well-specified, to the point that we can just treat it as a slightly weird programming language. In this article, I want to dig into wha

A Gentle Introduction to LLVM IR · mcyoung mcyoung I'm Sunny. I write about compilers, performance, and silly computer things. I also draw Pokémon. © 2026 Sunny Young de la Sota CC BY-SA • Site Analytics 2023-08-01 • 7554 words • 83 minutes • #dark-arts • #assembly • #toolchains A Gentle Introduction to LLVM IR The other day, I saw this tweet . In it, Andrew Gallant argues that reaching for LLVM IR, instead of assembly, is a useful tool for someone working on performance. Unfortunately, learning material on LLVM is usually aimed at compiler engineers, not generalist working programmers. N

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