1. fully binary: "[all] UB is nonsense" vs. "[all] UB is necessary for performance"
2. qualitative / anecdotic: "look at this compiler doing something unexpected" vs. "look at this optimizing compiler's transformation that would be impossible without UB".
Instead I would love to see a more fine-grained and quantitative study. There are many different types of UB. I'm sure every one of them is exploited by optimizing compilers. However, what would be the quantitative impact of disabling each of them on, say, SPECINT benchmarks? Of course some types of UB-related assumptions are deeply embedded in compilers, so it's clearly a question easier asked than answered. But I think simple things like signed-integer overflow handling can be changed (in clang at least?). Has anyone done benchmarking with this? Are you aware of any papers on the topic?