this post was submitted on 31 Aug 2023
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Rust
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The only problem with that is that llvm, which the Rust compiler uses, is primarily designed for C++. Since this language always has aliasing, the compiler isn’t optimizing well for that situation. I think it's fixed now, but for the first few years, rustc didn’t even supply the noalias attribute to the optimizer, because it was completely broken.
Yes, that optimization is finally enabled now. But even without it, programmers are less defensive when writing rust because of the freedom of UB, so they write more optimal code and use better architectures before the compiler even comes into play. It doesn't show in micro benchmarks, but in more complex software that has been written in rust from the start it's pretty obvious.