“Many can write faster asm than the compiler, yet don’t. Why?” by faul_sname

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Recorded30 Dec 2025

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There's a take I've seen going around, which goes approximately like this: It used to be the case that you had to write assembly to make computers do things, but then compilers came along. Now we have optimizing compilers, and those optimizing compilers can write assembly better than pretty much any human. Because of that, basically nobody writes assembly anymore. The same is about to be true of regular programming. I 85% agree with this take. However, I think there's one important inaccuracy: even today, finding places where your optimizing compiler failed to produce optimal code is often pretty straightforward, and once you've identified those places 10x+ speedups for that specific program on that specific hardware is often possible[1]. The reason nobody writes assembly anymore is the difficulty of mixing hand-written assembly with machine-generated assembly. The issue is that it's easy to have the compiler write all of the assembly in your project, and it's easy from a build perspective to have the compiler write none of the assembly in your project, but having the compiler write most but not all of the assembly in your project is hard. As with many things in proramming, having two sources of [...] The original text contained 4 footnotes which were omitted from this narration. --- First published: December 30th, 2025 Source: https://www.lesswrong.com/posts/LwzSqz3CAmNkWawe8/many-can-write-faster-asm-than-the-compiler-yet-don-t-why --- Narrated by TYPE III AUDIO.

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