The following code snippet crashes when generating CIR with -O2 enabled after PR#1220 was merged.

typedef struct { union { int a, b; }; int c; } S; void foo(S *s) { s->a = 1; } 

I haven't done a thorough review of the changes made, but I just noticed the PR broke something that worked for me before. Can't we add unions here, or just emit tbaa_NYI for all the non-scalar types for now?

cc: @PikachuHyA, @bcardosolopes