Since it's too late to edit my comment, I'm replying to note I was a bit off. `undef` actually doesn't propagate all the way to the conditional; instead, LLVM

Since it's too late to edit my comment, I'm replying to note I was a bit off. `undef` actually doesn't propagate all the way to the conditional; instead, LLVM replaces `undef < 150` with `false`, and the same for `undef > 120`, and then `false || false` is simplified to `false`. In C, comparing indeterminate values is undefined behavior, so LLVM would be allowed to replace `undef < 150` with `undef`, but it seems that LLVM itself has slightly stronger semantics. See also: https://llvm.org/docs/LangRef.html#undefined-values https://llvm.org/docs/LangRef.html#undefined-values