It's unclear. There were discussions on the rustc Zulip that recently pointed to LLVM being actually quite performant at canonicalizing poor-quality IR; so any

It's unclear. There were discussions on the rustc Zulip that recently pointed to LLVM being actually quite performant at canonicalizing poor-quality IR; so any time saved in the backend by producing better IR is offset by the additional time spent in the front-end to produce that IR. (I'm not a compiler developer, don't quote me on this)