[clang] [clang][CodeGen] Add TBAA for bit-field accesses (PR #226806)

[Bruno De Fraine via cfe-commits]

brunodf-gf wrote:

How about a simpler test case:

```
struct Bits {
  int a : 3;
  int b : 3;
};

int test(Bits *x, int *y) {
  x->a = 0;
  *y = 1;
  return x->a;
}
```

Is your intention to allow eliminating the reload here too?

Also, your patch should contain tests for the TBAA metadata generated by CodeGen directly.

https://github.com/llvm/llvm-project/pull/226806