6b8fb3fbd8
Enable const propagation into operands at mir_opt_level=2 Feature was added in #74507 but gated with `mir_opt_level>=3` because of compile time regressions. Let's see whether the LLVM 11 update solves that. As the [perf results](https://github.com/rust-lang/rust/pull/77107#issuecomment-697668154) show, enabling this optimization results in a lot less regression as before. cc @oli-obk r? @ghost