https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99637
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- I think the relevant sentence is "Each bit of the value representation of the result is equal to the corresponding bit in the object representation of from." For one of the bits in the result, there is no corresponding bit in the object representation of from. So the result cannot be created.
