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Comment by _bxg1 | Hacker News Reader

The original question aside, it's awesome that Rust has the potential to be faster than C++ because its language semantics allow for more compiler optimizations. I'd thought it was slightly slower, but maybe that's just a temporary state because C++ has had so much time to get optimized.

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I don't think that's the case. The article is comparing wildly different compilers (Visual Studio and LLVM) which are inevitably going to give very different results. Comparing Rust with clang would be a more interesting comparison since they use the same back end.

The idea that Rust has the potential to produce faster binaries than C/C++ comes, I guess, mainly from the fact that (once the bugs in LLVM have been fixed) Rust will be able to apply restrict/noalias very liberally to the generated IR, facilitating optimizations by the compiler backend which are not possible in your usual C/C++ codebase.

But yes, in this case it probably came down to some more obvious cause like a wildly different compiler.

Right, but I'm not basing that purely on these benchmarks. The fact that C++ allows so much, which Rust doesn't, prevents you from transforming code in certain ways that might achieve better performance with identical behavior. I'd just never really thought about the implications of that before. Because of this, in theory, equivalent Rust and C++ code should asymptotically approach a place where Rust is faster, even though at the moment there are many other factors like comparative maturity of the ecosystems.

The author posted a clang benchmark at the end of the article. It has pretty much the same performance as the MSVC one.

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