https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92152
--- Comment #14 from Jan Hubicka <hubicka at gcc dot gnu.org> --- Created attachment 47901 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47901&action=edit another related testcase > But that means we now miscompile the later two tests. Good point, those are my testcases :) I have missed it is scan-not. I will make updated patch. I am attaching related testcase that reads same data using two different union fields relying on C++ initial sequence rule (as Mark Williams explained me). "In a standard-layout union with an active member of non-union class type T1, it is permitted to read a non-static data member m of another union member of non-union class type T2 provided m is part of the common initial sequence of T1 and T2 (except that reading a volatile member through non-volatile glvalue is undefined)." This seems to indicate that we really can not disambiguate after union reference by access path unless we implement the "common initial sequence" check
