[SkySkimmer]

If you search for @@loop in TFA the last occurrence is in this paragraph:

>if a function is not purely tail-recursive, but contains some tail-recursive calls then the transformation will rewrite those calls but not the other ones. This may result in better code but it's hard to be sure in advance. In such cases (and cases where functions become purely tail-recursive only after inlining), users can force the transformation by using the [@@loop] attribute

[gergo_barany]

Unfortunately this doesn't answer the OP's question. OK, it may not result in better code. But in which cases, and for what reason? EDIT: And for that matter, does "not better" mean "neutral" or "actually worse"? To be clear, this is a flaw in the article, not a criticism of your response to the OP.