The compiler cannot optimize that into `while(true)` because the original code does not encounter undefined behavior when `limit` is small enough to fit into `int`. What it can do: infer that `limit <= INT_MAX` and use that to optimize the code following after the loop (and in some cases, even the code before the loop).

This isn't complete example. I don't remember the details unfortunately.

But somehow compiler has decided that i <= limit is always true.