Partially revert 482d98318fc1bfd003942c9de4ee1c7e8a0c45f0
Partially revert 482d98318fc1bfd003942c9de4ee1c7e8a0c45f0

This partially reverts "Convert int_to_float! to a function".

japaric/rustc-builtins,japaric/rustc-builtins