You can never trust an optimizing compiler. I’ve seen similar issues in pretty much every language I’ve written performance-sensitive code in. Point revisions c

You can never trust an optimizing compiler. I’ve seen similar issues in pretty much every language I’ve written performance-sensitive code in. Point revisions change optimizations all the time, sometimes with horribly disastrous results. One example: every time rust upgrades the version of LLVM underlying the compiler backend, the team prepares itself for a deluge of optimization regression reports (though this has been somewhat "mitigated" by a massive regression in rustc's ability to convey sufficient information to the LLVM backend for it to optimize to begin with, thanks to a change made to improve compile times [0]). This is almost universally true across all languages. The behaviors you see are usually the result of countless heuristics stacked one atop the other, and a tiny change here can end up with huge changes there. [0]: https://github.com/rust-lang/rust/pull/91743 https://github.com/rust-lang/rust/pull/91743