[flang-commits] [flang] [flang] Create TBAA subtree for COMMON block variables. (PR #153918)

[Slava Zakharin via flang-commits]

vzakhari wrote:

These changes work incorrectly for the following case:
```
module m1
  common /block/ a(10), b(10)
end
module m2
  common /block/ c(20)
end
subroutine foo
  use m1
  use m2
  a(1) = c(1) + b(1)
end
```

So in order to resolve this properly I need the information about the starting offsets withing the physical storage: https://discourse.llvm.org/t/rfc-flang-representation-for-objects-inside-physical-storage/88026

https://github.com/llvm/llvm-project/pull/153918