The issue was that LLVM codegen produced buggy output with strict aliasing, but this wasn't really caught until Rust since Rust can use it several orders of mag

The issue was that LLVM codegen produced buggy output with strict aliasing, but this wasn't really caught until Rust since Rust can use it several orders of magnitude more frequently than C / C++ frontends would. AIUI, the solution wasn't that Rust smuggled the language-level construct through the intermediate layer, but that they simply held off on expressing these constraints until bugfixes could be merged upstream into LLVM. The only downside to disabling this was simply that compiled code would potentially be a bit less optimal than otherwise, so such tactics weren't really necessary.